A simple, validated protocol consisting of a battery of tests is available to identify elderly patients with frailty syndrome. This syndrome of decreased reserve and resistance to stressors increases in incidence with increasing age. In the elderly, frailty may pursue a step-wise loss of function from non-frail to pre-frail to frail. We studied frailty in HIV-infected patients and found that ~20% are frail using the Fried phenotype using stringent criteria developed for the elderly1,2. In HIV infection the syndrome occurs at a younger age.
HIV patients were checked for 1) unintentional weight loss; 2) slowness as determined by walking speed; 3) weakness as measured by a grip dynamometer; 4) exhaustion by responses to a depression scale; and 5) low physical activity was determined by assessing kilocalories expended in a week's time. Pre-frailty was present with any two of five criteria and frailty was present if any three of the five criteria were abnormal.
The tests take approximately 10-15 min to complete and they can be performed by medical assistants during routine clinic visits. Test results are scored by referring to standard tables. Understanding which of the five components contribute to frailty in an individual patient can allow the clinician to address relevant underlying problems, many of which are not evident in routine HIV clinic visits.
21 Related JoVE Articles!
A Standardized Obstacle Course for Assessment of Visual Function in Ultra Low Vision and Artificial Vision
Institutions: University of Pittsburgh, University of Pittsburgh.
We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. Six sighted controls and 36 completely blind but otherwise healthy adult male (n=29) and female (n=13) subjects (age range 19-85 years), were enrolled in one of three studies involving testing of the BrainPort sensory substitution device. Subjects were asked to navigate the course prior to, and after, BrainPort training. They completed a total of 837 course runs in two different locations. Means and standard deviations were calculated across control types, courses, lights, and visits. We used a linear mixed effects model to compare different categories in the PPWS (percent preferred walking speed) and error percent data to show that the course iterations were properly designed. The course is relatively inexpensive, simple to administer, and has been shown to be a feasible way to test mobility function. Data analysis demonstrates that for the outcome of percent error as well as for percentage preferred walking speed, that each of the three courses is different, and that within each level, each of the three iterations are equal. This allows for randomization of the courses during administration.
preferred walking speed (PWS)
course speed (CS)
percentage preferred walking speed (PPWS)
Medicine, Issue 84, Obstacle course, navigation assessment, BrainPort, wayfinding, low vision
Characterization of Complex Systems Using the Design of Experiments Approach: Transient Protein Expression in Tobacco as a Case Study
Institutions: RWTH Aachen University, Fraunhofer Gesellschaft.
Plants provide multiple benefits for the production of biopharmaceuticals including low costs, scalability, and safety. Transient expression offers the additional advantage of short development and production times, but expression levels can vary significantly between batches thus giving rise to regulatory concerns in the context of good manufacturing practice. We used a design of experiments (DoE) approach to determine the impact of major factors such as regulatory elements in the expression construct, plant growth and development parameters, and the incubation conditions during expression, on the variability of expression between batches. We tested plants expressing a model anti-HIV monoclonal antibody (2G12) and a fluorescent marker protein (DsRed). We discuss the rationale for selecting certain properties of the model and identify its potential limitations. The general approach can easily be transferred to other problems because the principles of the model are broadly applicable: knowledge-based parameter selection, complexity reduction by splitting the initial problem into smaller modules, software-guided setup of optimal experiment combinations and step-wise design augmentation. Therefore, the methodology is not only useful for characterizing protein expression in plants but also for the investigation of other complex systems lacking a mechanistic description. The predictive equations describing the interconnectivity between parameters can be used to establish mechanistic models for other complex systems.
Bioengineering, Issue 83, design of experiments (DoE), transient protein expression, plant-derived biopharmaceuticals, promoter, 5'UTR, fluorescent reporter protein, model building, incubation conditions, monoclonal antibody
An Affordable HIV-1 Drug Resistance Monitoring Method for Resource Limited Settings
Institutions: University of KwaZulu-Natal, Durban, South Africa, Jembi Health Systems, University of Amsterdam, Stanford Medical School.
HIV-1 drug resistance has the potential to seriously compromise the effectiveness and impact of antiretroviral therapy (ART). As ART programs in sub-Saharan Africa continue to expand, individuals on ART should be closely monitored for the emergence of drug resistance. Surveillance of transmitted drug resistance to track transmission of viral strains already resistant to ART is also critical. Unfortunately, drug resistance testing is still not readily accessible in resource limited settings, because genotyping is expensive and requires sophisticated laboratory and data management infrastructure. An open access genotypic drug resistance monitoring method to manage individuals and assess transmitted drug resistance is described. The method uses free open source software for the interpretation of drug resistance patterns and the generation of individual patient reports. The genotyping protocol has an amplification rate of greater than 95% for plasma samples with a viral load >1,000 HIV-1 RNA copies/ml. The sensitivity decreases significantly for viral loads <1,000 HIV-1 RNA copies/ml. The method described here was validated against a method of HIV-1 drug resistance testing approved by the United States Food and Drug Administration (FDA), the Viroseq genotyping method. Limitations of the method described here include the fact that it is not automated and that it also failed to amplify the circulating recombinant form CRF02_AG from a validation panel of samples, although it amplified subtypes A and B from the same panel.
Medicine, Issue 85, Biomedical Technology, HIV-1, HIV Infections, Viremia, Nucleic Acids, genetics, antiretroviral therapy, drug resistance, genotyping, affordable
The Multiple Sclerosis Performance Test (MSPT): An iPad-Based Disability Assessment Tool
Institutions: Cleveland Clinic Foundation, Cleveland Clinic Foundation, Cleveland Clinic Foundation, Cleveland Clinic Foundation.
Precise measurement of neurological and neuropsychological impairment and disability in multiple sclerosis is challenging. We report a new test, the Multiple Sclerosis Performance Test (MSPT), which represents a new approach to quantifying MS related disability. The MSPT takes advantage of advances in computer technology, information technology, biomechanics, and clinical measurement science. The resulting MSPT represents a computer-based platform for precise, valid measurement of MS severity. Based on, but extending the Multiple Sclerosis Functional Composite (MSFC), the MSPT provides precise, quantitative data on walking speed, balance, manual dexterity, visual function, and cognitive processing speed. The MSPT was tested by 51 MS patients and 49 healthy controls (HC). MSPT scores were highly reproducible, correlated strongly with technician-administered test scores, discriminated MS from HC and severe from mild MS, and correlated with patient reported outcomes. Measures of reliability, sensitivity, and clinical meaning for MSPT scores were favorable compared with technician-based testing. The MSPT is a potentially transformative approach for collecting MS disability outcome data for patient care and research. Because the testing is computer-based, test performance can be analyzed in traditional or novel ways and data can be directly entered into research or clinical databases. The MSPT could be widely disseminated to clinicians in practice settings who are not connected to clinical trial performance sites or who are practicing in rural settings, drastically improving access to clinical trials for clinicians and patients. The MSPT could be adapted to out of clinic settings, like the patient’s home, thereby providing more meaningful real world data. The MSPT represents a new paradigm for neuroperformance testing. This method could have the same transformative effect on clinical care and research in MS as standardized computer-adapted testing has had in the education field, with clear potential to accelerate progress in clinical care and research.
Medicine, Issue 88, Multiple Sclerosis, Multiple Sclerosis Functional Composite, computer-based testing, 25-foot walk test, 9-hole peg test, Symbol Digit Modalities Test, Low Contrast Visual Acuity, Clinical Outcome Measure
Rapid Screening of HIV Reverse Transcriptase and Integrase Inhibitors
Institutions: National Cancer Institute.
Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify new compounds that can inhibit infection by the common drug resistant HIV-1 strains with minimal toxicity. Here we describe an efficient assay that can be used to rapidly determine the cellular cytotoxicity and efficacy of a compound against WT and mutant viral strains.
The desired target cell line is seeded in a 96-well plate and, after a 24 hr incubation, serially dilutions of the compounds to be tested are added. No further manipulations are necessary for cellular cytotoxicity assays; for anti HIV assays a predetermined amount of either a WT or drug resistant HIV-1 vector that expresses luciferase is added to the cells. Cytotoxicity is measured by using an ATP dependent luminescence assay and the impact of the compounds on infectivity is measured by determining the amount of luciferase in the presence or the absence of the putative inhibitors.
This screening assay takes 4 days to complete and multiple compounds can be screened in parallel. Compounds are screened in triplicate and the data are normalized to the infectivity/ATP levels in absence of target compounds. This technique provides a quick and accurate measurement of the efficacy and toxicity of potential anti HIV compounds.
Immunology, Issue 86, HIV, cytotoxicity, infectivity, luciferase, drug resistance, integrase, reverse transcriptase
A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses
Institutions: Emory University, Emory University.
The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target conserved portions of the HIV-1 genome that escape with difficulty. Sequence changes attributed to cellular immune pressure arise across the genome during infection, and if found within conserved regions of the genome such as Gag, can affect the ability of the virus to replicate in vitro
. Transmission of HLA-linked polymorphisms in Gag to HLA-mismatched recipients has been associated with reduced set point viral loads. We hypothesized this may be due to a reduced replication capacity of the virus. Here we present a novel method for assessing the in vitro
replication of HIV-1 as influenced by the gag
gene isolated from acute time points from subtype C infected Zambians. This method uses restriction enzyme based cloning to insert the gag
gene into a common subtype C HIV-1 proviral backbone, MJ4. This makes it more appropriate to the study of subtype C sequences than previous recombination based methods that have assessed the in vitro
replication of chronically derived gag-pro
sequences. Nevertheless, the protocol could be readily modified for studies of viruses from other subtypes. Moreover, this protocol details a robust and reproducible method for assessing the replication capacity of the Gag-MJ4 chimeric viruses on a CEM-based T cell line. This method was utilized for the study of Gag-MJ4 chimeric viruses derived from 149 subtype C acutely infected Zambians, and has allowed for the identification of residues in Gag that affect replication. More importantly, the implementation of this technique has facilitated a deeper understanding of how viral replication defines parameters of early HIV-1 pathogenesis such as set point viral load and longitudinal CD4+ T cell decline.
Infectious Diseases, Issue 90, HIV-1, Gag, viral replication, replication capacity, viral fitness, MJ4, CEM, GXR25
Combining Magnetic Sorting of Mother Cells and Fluctuation Tests to Analyze Genome Instability During Mitotic Cell Aging in Saccharomyces cerevisiae
Institutions: Rensselaer Polytechnic Institute.
has been an excellent model system for examining mechanisms and consequences of genome instability. Information gained from this yeast model is relevant to many organisms, including humans, since DNA repair and DNA damage response factors are well conserved across diverse species. However, S. cerevisiae
has not yet been used to fully address whether the rate of accumulating mutations changes with increasing replicative (mitotic) age due to technical constraints. For instance, measurements of yeast replicative lifespan through micromanipulation involve very small populations of cells, which prohibit detection of rare mutations. Genetic methods to enrich for mother cells in populations by inducing death of daughter cells have been developed, but population sizes are still limited by the frequency with which random mutations that compromise the selection systems occur. The current protocol takes advantage of magnetic sorting of surface-labeled yeast mother cells to obtain large enough populations of aging mother cells to quantify rare mutations through phenotypic selections. Mutation rates, measured through fluctuation tests, and mutation frequencies are first established for young cells and used to predict the frequency of mutations in mother cells of various replicative ages. Mutation frequencies are then determined for sorted mother cells, and the age of the mother cells is determined using flow cytometry by staining with a fluorescent reagent that detects bud scars formed on their cell surfaces during cell division. Comparison of predicted mutation frequencies based on the number of cell divisions to the frequencies experimentally observed for mother cells of a given replicative age can then identify whether there are age-related changes in the rate of accumulating mutations. Variations of this basic protocol provide the means to investigate the influence of alterations in specific gene functions or specific environmental conditions on mutation accumulation to address mechanisms underlying genome instability during replicative aging.
Microbiology, Issue 92, Aging, mutations, genome instability, Saccharomyces cerevisiae, fluctuation test, magnetic sorting, mother cell, replicative aging
Collection, Isolation, and Flow Cytometric Analysis of Human Endocervical Samples
Institutions: University of Manitoba, University of Manitoba.
Despite the public health importance of mucosal pathogens (including HIV), relatively little is known about mucosal immunity, particularly at the female genital tract (FGT). Because heterosexual transmission now represents the dominant mechanism of HIV transmission, and given the continual spread of sexually transmitted infections (STIs), it is critical to understand the interplay between host and pathogen at the genital mucosa. The substantial gaps in knowledge around FGT immunity are partially due to the difficulty in successfully collecting and processing mucosal samples. In order to facilitate studies with sufficient sample size, collection techniques must be minimally invasive and efficient. To this end, a protocol for the collection of cervical cytobrush samples and subsequent isolation of cervical mononuclear cells (CMC) has been optimized. Using ex vivo
flow cytometry-based immunophenotyping, it is possible to accurately and reliably quantify CMC lymphocyte/monocyte population frequencies and phenotypes. This technique can be coupled with the collection of cervical-vaginal lavage (CVL), which contains soluble immune mediators including cytokines, chemokines and anti-proteases, all of which can be used to determine the anti- or pro-inflammatory environment in the vagina.
Medicine, Issue 89, mucosal, immunology, FGT, lavage, cervical, CMC
Community-based Adapted Tango Dancing for Individuals with Parkinson's Disease and Older Adults
Institutions: Emory University School of Medicine, Brigham and Woman‘s Hospital and Massachusetts General Hospital.
Adapted tango dancing improves mobility and balance in older adults and additional populations with balance impairments. It is composed of very simple step elements. Adapted tango involves movement initiation and cessation, multi-directional perturbations, varied speeds and rhythms. Focus on foot placement, whole body coordination, and attention to partner, path of movement, and aesthetics likely underlie adapted tango’s demonstrated efficacy for improving mobility and balance. In this paper, we describe the methodology to disseminate the adapted tango teaching methods to dance instructor trainees and to implement the adapted tango by the trainees in the community for older adults and individuals with Parkinson’s Disease (PD). Efficacy in improving mobility (measured with the Timed Up and Go, Tandem stance, Berg Balance Scale, Gait Speed and 30 sec chair stand), safety and fidelity of the program is maximized through targeted instructor and volunteer training and a structured detailed syllabus outlining class practices and progression.
Behavior, Issue 94, Dance, tango, balance, pedagogy, dissemination, exercise, older adults, Parkinson's Disease, mobility impairments, falls
Simultaneous Quantification of T-Cell Receptor Excision Circles (TRECs) and K-Deleting Recombination Excision Circles (KRECs) by Real-time PCR
Institutions: Spedali Civili di Brescia.
T-cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) are circularized DNA elements formed during recombination process that creates T- and B-cell receptors. Because TRECs and KRECs are unable to replicate, they are diluted after each cell division, and therefore persist in the cell. Their quantity in peripheral blood can be considered as an estimation of thymic and bone marrow output. By combining well established and commonly used TREC assay with a modified version of KREC assay, we have developed a duplex quantitative real-time PCR that allows quantification of both newly-produced T and B lymphocytes in a single assay. The number of TRECs and KRECs are obtained using a standard curve prepared by serially diluting TREC and KREC signal joints cloned in a bacterial plasmid, together with a fragment of T-cell receptor alpha constant gene that serves as reference gene. Results are reported as number of TRECs and KRECs/106
cells or per ml of blood. The quantification of these DNA fragments have been proven useful for monitoring immune reconstitution following bone marrow transplantation in both children and adults, for improved characterization of immune deficiencies, or for better understanding of certain immunomodulating drug activity.
Immunology, Issue 94, B lymphocytes, primary immunodeficiency, real-time PCR, immune recovery, T-cell homeostasis, T lymphocytes, thymic output, bone marrow output
Assessment of Age-related Changes in Cognitive Functions Using EmoCogMeter, a Novel Tablet-computer Based Approach
Institutions: Freie Universität Berlin, Charité Berlin, Freie Universität Berlin, Psychiatric University Hospital Zurich.
The main goal of this study was to assess the usability of a tablet-computer-based application (EmoCogMeter) in investigating the effects of age on cognitive functions across the lifespan in a sample of 378 healthy subjects (age range 18-89 years). Consistent with previous findings we found an age-related cognitive decline across a wide range of neuropsychological domains (memory, attention, executive functions), thereby proving the usability of our tablet-based application. Regardless of prior computer experience, subjects of all age groups were able to perform the tasks without instruction or feedback from an experimenter. Increased motivation and compliance proved to be beneficial for task performance, thereby potentially increasing the validity of the results. Our promising findings underline the great clinical and practical potential of a tablet-based application for detection and monitoring of cognitive dysfunction.
Behavior, Issue 84, Neuropsychological Testing, cognitive decline, age, tablet-computer, memory, attention, executive functions
Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules
Institutions: Princeton University.
The aim of de novo
protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific properties, such as binding affinity, agonist or antagonist behavior, or stability, relative to the native sequence. Protein design lies at the center of current advances drug design and discovery. Not only does protein design provide predictions for potentially useful drug targets, but it also enhances our understanding of the protein folding process and protein-protein interactions. Experimental methods such as directed evolution have shown success in protein design. However, such methods are restricted by the limited sequence space that can be searched tractably. In contrast, computational design strategies allow for the screening of a much larger set of sequences covering a wide variety of properties and functionality. We have developed a range of computational de novo
protein design methods capable of tackling several important areas of protein design. These include the design of monomeric proteins for increased stability and complexes for increased binding affinity.
To disseminate these methods for broader use we present Protein WISDOM (http://www.proteinwisdom.org), a tool that provides automated methods for a variety of protein design problems. Structural templates are submitted to initialize the design process. The first stage of design is an optimization sequence selection stage that aims at improving stability through minimization of potential energy in the sequence space. Selected sequences are then run through a fold specificity stage and a binding affinity stage. A rank-ordered list of the sequences for each step of the process, along with relevant designed structures, provides the user with a comprehensive quantitative assessment of the design. Here we provide the details of each design method, as well as several notable experimental successes attained through the use of the methods.
Genetics, Issue 77, Molecular Biology, Bioengineering, Biochemistry, Biomedical Engineering, Chemical Engineering, Computational Biology, Genomics, Proteomics, Protein, Protein Binding, Computational Biology, Drug Design, optimization (mathematics), Amino Acids, Peptides, and Proteins, De novo protein and peptide design, Drug design, In silico sequence selection, Optimization, Fold specificity, Binding affinity, sequencing
Peptide-based Identification of Functional Motifs and their Binding Partners
Institutions: Morehouse School of Medicine, Institute for Systems Biology, Universiti Sains Malaysia.
Specific short peptides derived from motifs found in full-length proteins, in our case HIV-1 Nef, not only retain their biological function, but can also competitively inhibit the function of the full-length protein. A set of 20 Nef scanning peptides, 20 amino acids in length with each overlapping 10 amino acids of its neighbor, were used to identify motifs in Nef responsible for its induction of apoptosis. Peptides containing these apoptotic motifs induced apoptosis at levels comparable to the full-length Nef protein. A second peptide, derived from the Secretion Modification Region (SMR) of Nef, retained the ability to interact with cellular proteins involved in Nef's secretion in exosomes (exNef). This SMRwt peptide was used as the "bait" protein in co-immunoprecipitation experiments to isolate cellular proteins that bind specifically to Nef's SMR motif. Protein transfection and antibody inhibition was used to physically disrupt the interaction between Nef and mortalin, one of the isolated SMR-binding proteins, and the effect was measured with a fluorescent-based exNef secretion assay. The SMRwt peptide's ability to outcompete full-length Nef for cellular proteins that bind the SMR motif, make it the first inhibitor of exNef secretion. Thus, by employing the techniques described here, which utilize the unique properties of specific short peptides derived from motifs found in full-length proteins, one may accelerate the identification of functional motifs in proteins and the development of peptide-based inhibitors of pathogenic functions.
Virology, Issue 76, Biochemistry, Immunology, Infection, Infectious Diseases, Molecular Biology, Medicine, Genetics, Microbiology, Genomics, Proteins, Exosomes, HIV, Peptides, Exocytosis, protein trafficking, secretion, HIV-1, Nef, Secretion Modification Region, SMR, peptide, AIDS, assay
The α-test: Rapid Cell-free CD4 Enumeration Using Whole Saliva
Institutions: Weill Cornell Medical College , University of Missouri-Kansas City-School of Dentistry, University of Missouri Kansas City- School of Pharmacy, Bamenda, NWP, Cameroon, Mezam Polyclinic HIV/AIDS Treatment Center, Cameroon, Institute for Human Genetics and Biochemistry.
There is an urgent need for affordable CD4 enumeration to monitor HIV disease. CD4 enumeration is out of reach in resource-limited regions due to the time and temperature restrictions, technical sophistication, and cost of reagents, in particular monoclonal antibodies to measure CD4 on blood cells, the only currently acceptable method. A commonly used cost-saving and time-saving laboratory strategy is to calculate, rather than measure certain blood values. For example, LDL levels are calculated using the measured levels of total cholesterol, HDL, and triglycerides1
. Thus, identification of cell-free correlates that directly regulate the number of CD4+
T cells could provide an accurate method for calculating CD4 counts due to the physiological relevance of the correlates.
The number of stem cells that enter blood and are destined to become circulating CD4+
T cells is determined by the chemokine CXCL12 and its receptor CXCR4 due to their influence on locomotion2
. The process of stem cell locomotion into blood is additionally regulated by cell surface human leukocyte elastase (HLECS
) and the HLECS
-reactive active α1
proteinase inhibitor (α1
. In HIV-1 disease, α1
PI is inactivated due to disease processes 4
. In the early asymptomatic categories of HIV-1 disease, active α1
PI was found to be below normal in 100% of untreated HIV-1 patients (median=12 μM, and to achieve normal levels during the symptomatic categories4, 5
. This pattern has been attributed to immune inactivation, not to insufficient synthesis, proteolytic inactivation, or oxygenation. We observed that in HIV-1 subjects with >220 CD4 cells/μl, CD4 counts were correlated with serum levels of active α1
=0.93, p<0.0001, n=26) and inactive α1
=0.91, p<0.0001, n=26) 5
. Administration of α1
PI to HIV-1 infected and uninfected subjects resulted in dramatic increases in CD4 counts suggesting α1
PI participates in regulating the number of CD4+
T cells in blood 3
With stimulation, whole saliva contains sufficient serous exudate (plasma containing proteinaceous material that passes through blood vessel walls into saliva) to allow measurement of active α1
PI and the correlation of this measurement is evidence that it is an accurate method for calculating CD4 counts. Briefly, sialogogues such as chewing gum or citric acid stimulate the exudation of serum into whole mouth saliva. After stimulating serum exudation, the activity of serum α1
PI in saliva is measured by its capacity to inhibit elastase activity. Porcine pancreatic elastase (PPE) is a readily available inexpensive source of elastase. PPE binds to α1
PI forming a one-to-one complex that prevents PPE from cleaving its specific substrates, one of which is the colorimetric peptide, succinyl-L-Ala-L-Ala-L-Ala-p-nitroanilide (SA3
NA). Incubating saliva with a saturating concentration of PPE for 10 min at room temperature allows the binding of PPE to all the active α1
PI in saliva. The resulting inhibition of PPE by active α1
PI can be measured by adding the PPE substrate SA3
NA. (Figure 1)
. Although CD4 counts are measured in terms of blood volume (CD4 cells/μl), the concentration of α1
PI in saliva is related to the concentration of serum in saliva, not to volume of saliva since volume can vary considerably during the day and person to person6
. However, virtually all the protein in saliva is due to serum content, and the protein content of saliva is measurable7
. Thus, active α1
PI in saliva is calculated as a ratio to saliva protein content and is termed the α1
PI Index. Results presented herein demonstrate that the α1
PI Index provides an accurate and precise physiologic method for calculating CD4 counts.
Medicine, Issue 63, CD4 count, saliva, antitrypsin, hematopoiesis, T cells, HIV/AIDS, clinical
Sequencing of Bacterial Microflora in Peripheral Blood: our Experience with HIV-infected Patients
Institutions: San Paolo Hospital University of Milan, Italy.
The healthy gastrointestinal tract is physiologically colonized by a large variety of commensal microbes that influence the development
of the humoral and cellular mucosal immune system1,2
Microbiota is shielded from the immune system via a strong mucosal barrier. Infections and antibiotics are known to alter both the normal
gastrointestinal tract barrier and the composition of resident bacteria, which may result in possible immune abnormalities3
HIV causes a breach in the gastrointestinal barrier with progressive failure of mucosal immunity and leakage into the systemic circulation of bacterial bioproducts, such as lipopolysaccharide and
bacterial DNA fragments, which contribute to systemic immune activation4-7
. Microbial translocation is implicated in HIV/AIDS immunopathogenesis and response to therapy 4,8
We aimed to characterise the composition of bacteria translocating in peripheral blood of HIV-infected patients. To pursue our aim we set up a PCR reaction for the panbacteric 16S ribosomial gene
followed by a sequencing analysis.
Briefly, whole blood from both HIV-infected and healthy subjects is used. Given that healthy individuals present normal intestinal homeostasis no translocation of microflora is expected in
these patients. Following whole blood collection by venipuncture and plasma separation, DNA is extracted from plasma and used to perform a broad range PCR reaction for the panbacteric
16S ribosomial gene9
. Following PCR product purification, cloning and sequencing analyses are performed.
Medicine, Issue 52, Plasma DNA extraction, 16S rRNA gene PCR, sequencing analysis, HIV
Specific Marking of HIV-1 Positive Cells using a Rev-dependent Lentiviral Vector Expressing the Green Fluorescent Protein
Institutions: George Mason University.
Most of HIV-responsive expression vectors are based on the HIV promoter, the long terminal repeat (LTR). While responsive to an early HIV protein, Tat, the LTR is also responsive to cellular activation states and to the local chromatin activity where the integration has occurred. This can result in high HIV-independent activity, and has restricted the usefulness of LTR-based reporter to mark HIV positive cells 1,2,3
. Here, we constructed an expression lentiviral vector that possesses, in addition to the Tat-responsive LTR, numerous HIV DNA sequences that include the Rev-response element and HIV splicing sites 4,5,6
. The vector was incorporated into a lentiviral reporter virus, permitting highly specific detection of replicating HIV in living cell populations. The activity of the vector was measured by expression of the green fluorescence protein (GFP). The application of this vector as reported here offers a novel alternative approach to existing methods, such as in situ
PCR or HIV antigen staining, to identify HIV-positive cells. The vector can also express therapeutic genes for basic or clinical experimentation to target HIV-positive cells.
Infectious Disease, Issue 43, HIV-1, Rev, GFP, lentiviral vector, RRE
Molecular Evolution of the Tre Recombinase
Institutions: Max Plank Institute for Molecular Cell Biology and Genetics, Dresden.
Here we report the generation of Tre recombinase through directed, molecular evolution. Tre recombinase recognizes a pre-defined target sequence within the LTR sequences of the HIV-1 provirus, resulting in the excision and eradication of the provirus from infected human cells.
We started with Cre, a 38-kDa recombinase, that recognizes a 34-bp double-stranded DNA sequence known as loxP. Because Cre can effectively eliminate genomic sequences, we set out to tailor a recombinase that could remove the sequence between the 5'-LTR and 3'-LTR of an integrated HIV-1 provirus. As a first step we identified sequences within the LTR sites that were similar to loxP and tested for recombination activity. Initially Cre and mutagenized Cre libraries failed to recombine the chosen loxLTR sites of the HIV-1 provirus. As the start of any directed molecular evolution process requires at least residual activity, the original asymmetric loxLTR sequences were split into subsets and tested again for recombination activity. Acting as intermediates, recombination activity was shown with the subsets. Next, recombinase libraries were enriched through reiterative evolution cycles. Subsequently, enriched libraries were shuffled and recombined. The combination of different mutations proved synergistic and recombinases were created that were able to recombine loxLTR1 and loxLTR2. This was evidence that an evolutionary strategy through intermediates can be successful. After a total of 126 evolution cycles individual recombinases were functionally and structurally analyzed. The most active recombinase -- Tre -- had 19 amino acid changes as compared to Cre. Tre recombinase was able to excise the HIV-1 provirus from the genome HIV-1 infected HeLa cells (see "HIV-1 Proviral DNA Excision Using an Evolved Recombinase", Hauber J., Heinrich-Pette-Institute for Experimental Virology and Immunology, Hamburg, Germany). While still in its infancy, directed molecular evolution will allow the creation of custom enzymes that will serve as tools of "molecular surgery" and molecular medicine.
Cell Biology, Issue 15, HIV-1, Tre recombinase, Site-specific recombination, molecular evolution
Interview: HIV-1 Proviral DNA Excision Using an Evolved Recombinase
Institutions: Heinrich-Pette-Institute for Experimental Virology and Immunology, University of Hamburg.
HIV-1 integrates into the host chromosome of infected cells and persists as a provirus flanked by long terminal repeats. Current treatment strategies primarily target virus enzymes or virus-cell fusion, suppressing the viral life cycle without eradicating the infection. Since the integrated provirus is not targeted by these approaches, new resistant strains of HIV-1 may emerge. Here, we report that the engineered recombinase Tre (see Molecular evolution of the Tre recombinase , Buchholz, F., Max Planck Institute for Cell Biology and Genetics, Dresden) efficiently excises integrated HIV-1 proviral DNA from the genome of infected cells. We produced loxLTR containing viral pseudotypes and infected HeLa cells to examine whether Tre recombinase can excise the provirus from the genome of HIV-1 infected human cells. A virus particle-releasing cell line was cloned and transfected with a plasmid expressing Tre or with a parental control vector. Recombinase activity and virus production were monitored. All assays demonstrated the efficient deletion of the provirus from infected cells without visible cytotoxic effects. These results serve as proof of principle that it is possible to evolve a recombinase to specifically target an HIV-1 LTR and that this recombinase is capable of excising the HIV-1 provirus from the genome of HIV-1-infected human cells.
Before an engineered recombinase could enter the therapeutic arena, however, significant obstacles need to be overcome. Among the most critical issues, that we face, are an efficient and safe delivery to targeted cells and the absence of side effects.
Medicine, Issue 16, HIV, Cell Biology, Recombinase, provirus, HeLa Cells
Using Visual and Narrative Methods to Achieve Fair Process in Clinical Care
Institutions: Brandeis University, Brandeis University.
The Institute of Medicine has targeted patient-centeredness as an important area of quality improvement. A major dimension of patient-centeredness is respect for patient's values, preferences, and expressed needs. Yet specific approaches to gaining this understanding and translating it to quality care in the clinical setting are lacking. From a patient perspective quality is not a simple concept but is best understood in terms of five dimensions: technical outcomes; decision-making efficiency; amenities and convenience; information and emotional support; and overall patient satisfaction. Failure to consider quality from this five-pronged perspective results in a focus on medical outcomes, without considering the processes central to quality from the patient's perspective and vital to achieving good outcomes. In this paper, we argue for applying the concept of fair process in clinical settings. Fair process involves using a collaborative approach to exploring diagnostic issues and treatments with patients, explaining the rationale for decisions, setting expectations about roles and responsibilities, and implementing a core plan and ongoing evaluation. Fair process opens the door to bringing patient expertise into the clinical setting and the work of developing health care goals and strategies. This paper provides a step by step illustration of an innovative visual approach, called photovoice or photo-elicitation, to achieve fair process in clinical work with acquired brain injury survivors and others living with chronic health conditions. Applying this visual tool and methodology in the clinical setting will enhance patient-provider communication; engage patients as partners in identifying challenges, strengths, goals, and strategies; and support evaluation of progress over time. Asking patients to bring visuals of their lives into the clinical interaction can help to illuminate gaps in clinical knowledge, forge better therapeutic relationships with patients living with chronic conditions such as brain injury, and identify patient-centered goals and possibilities for healing. The process illustrated here can be used by clinicians, (primary care physicians, rehabilitation therapists, neurologists, neuropsychologists, psychologists, and others) working with people living with chronic conditions such as acquired brain injury, mental illness, physical disabilities, HIV/AIDS, substance abuse, or post-traumatic stress, and by leaders of support groups for the types of patients described above and their family members or caregivers.
Medicine, Issue 48, person-centered care, participatory visual methods, photovoice, photo-elicitation, narrative medicine, acquired brain injury, disability, rehabilitation, palliative care
A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia
Institutions: Universite de Montreal, Universite de Montreal, Universite de Montreal.
There are several lines of evidence supporting the role of de novo
mutations as a mechanism for common disorders, such as autism and schizophrenia. First, the de novo
mutation rate in humans is relatively high, so new mutations are generated at a high frequency in the population. However, de novo
mutations have not been reported in most common diseases. Mutations in genes leading to severe diseases where there is a strong negative selection against the phenotype, such as lethality in embryonic stages or reduced reproductive fitness, will not be transmitted to multiple family members, and therefore will not be detected by linkage gene mapping or association studies. The observation of very high concordance in monozygotic twins and very low concordance in dizygotic twins also strongly supports the hypothesis that a significant fraction of cases may result from new mutations. Such is the case for diseases such as autism and schizophrenia. Second, despite reduced reproductive fitness1
and extremely variable environmental factors, the incidence of some diseases is maintained worldwide at a relatively high and constant rate. This is the case for autism and schizophrenia, with an incidence of approximately 1% worldwide. Mutational load can be thought of as a balance between selection for or against a deleterious mutation and its production by de novo
mutation. Lower rates of reproduction constitute a negative selection factor that should reduce the number of mutant alleles in the population, ultimately leading to decreased disease prevalence. These selective pressures tend to be of different intensity in different environments. Nonetheless, these severe mental disorders have been maintained at a constant relatively high prevalence in the worldwide population across a wide range of cultures and countries despite a strong negative selection against them2
. This is not what one would predict in diseases with reduced reproductive fitness, unless there was a high new mutation rate. Finally, the effects of paternal age: there is a significantly increased risk of the disease with increasing paternal age, which could result from the age related increase in paternal de novo
mutations. This is the case for autism and schizophrenia3
. The male-to-female ratio of mutation rate is estimated at about 4–6:1, presumably due to a higher number of germ-cell divisions with age in males. Therefore, one would predict that de novo
mutations would more frequently come from males, particularly older males4
. A high rate of new mutations may in part explain why genetic studies have so far failed to identify many genes predisposing to complexes diseases genes, such as autism and schizophrenia, and why diseases have been identified for a mere 3% of genes in the human genome. Identification for de novo
mutations as a cause of a disease requires a targeted molecular approach, which includes studying parents and affected subjects. The process for determining if the genetic basis of a disease may result in part from de novo
mutations and the molecular approach to establish this link will be illustrated, using autism and schizophrenia as examples.
Medicine, Issue 52, de novo mutation, complex diseases, schizophrenia, autism, rare variations, DNA sequencing
Using Micro-Electro-Mechanical Systems (MEMS) to Develop Diagnostic Tools
Institutions: Brigham and Women's Hospital.
Cellular Biology, Issue 8, microfluidics, diagnostics, capture, blood, HIV, bioengineering