Individuals who are heterozygous for the CCR5-?32 mutation provide a natural model to examine the effects of reduced CCR5 expression on human immunodeficiency virus (HIV) persistence. We evaluated the HIV reservoir in 18 CCR5-?32 heterozygotes and 54 CCR5 wild-type individuals during suppressive antiretroviral therapy. Cell-associated HIV RNA levels (P = .035), RNA to DNA transcriptional ratios (P = .013), and frequency of detectable HIV 2-long terminal repeat circular DNA (P = .013) were significantly lower in CD4(+) T cells from CCR5-?32 heterozygotes. Cell-associated HIV RNA was significantly correlated with CCR5 surface expression on CD4(+) T cells (r(2) = 0.136; P = .002). Our findings suggest that curative strategies should further explore manipulation of CCR5.
The design of biomimetic nanomaterials that can directly influence the behavior of cells and facilitate the regeneration of tissues and organs has become an active area of research. Here, the production of materials based on nano-hydroxyapatite composites in scaffolds with nanofibrous and nanoporous topographies, designed to mimic the native bone matrix for applications in bone tissue engineering, is reported. Human mesenchymal stem cells grown on these nanocomposites are stimulated to rapidly produce bone minerals in situ, even in the absence of osteogenic supplements in the cell-culture medium. Nanocomposites comprising type I collagen and nano-hydroxyapatite are found to be especially efficient at inducing mineralization. When subcutaneously implanted into nude mice, this biomimetic nanocomposite is able to form a new bone matrix within only two weeks. Furthermore, when the nanocomposite is enriched with human mesenchymal stem cells before implantation, development of the bone matrix is accelerated to within one week. To the best of the authors' knowledge, this study provides the first clear in vitro and in vivo demonstration of osteoinduction controlled by the material characteristics of a biomimetic nanocomposite. This approach can potentially facilitate the translation of de novo bone-formation technologies to the clinic.
Antibody VRC01 is a human immunoglobulin that neutralizes about 90% of HIV-1 isolates. To understand how such broadly neutralizing antibodies develop, we used x-ray crystallography and 454 pyrosequencing to characterize additional VRC01-like antibodies from HIV-1-infected individuals. Crystal structures revealed a convergent mode of binding for diverse antibodies to the same CD4-binding-site epitope. A functional genomics analysis of expressed heavy and light chains revealed common pathways of antibody-heavy chain maturation, confined to the IGHV1-2*02 lineage, involving dozens of somatic changes, and capable of pairing with different light chains. Broadly neutralizing HIV-1 immunity associated with VRC01-like antibodies thus involves the evolution of antibodies to a highly affinity-matured state required to recognize an invariant viral structure, with lineages defined from thousands of sequences providing a genetic roadmap of their development.
Microinjection of recombinant DNA into zygotic pronuclei has been widely used for producing transgenic mice. However, with this method, the insertion site, integrity, and copy number of the transgene cannot be controlled. Here, we present an integrase-based approach to produce transgenic mice via pronuclear injection, whereby an intact single-copy transgene can be inserted into predetermined chromosomal loci with high efficiency (up to 40%), and faithfully transmitted through generations. We show that neighboring transgenic elements and bacterial DNA within the transgene cause profound silencing and expression variability of the transgenic marker. Removal of these undesirable elements leads to global high-level marker expression from transgenes driven by a ubiquitous promoter. We also obtained faithful marker expression from a tissue-specific promoter. The technique presented here will greatly facilitate murine transgenesis and precise structure/function dissection of mammalian gene function and regulation in vivo.
The circadian rhythm in Neurospora crassa is exhibited as alternating areas of conidiating and non-conidiating mycelia growth. A significant role in this circadian rhythm is played by the frq (frequency) and wc (white-collar) genes, comprising the "FWC" oscillator. Strains lacking the FWC can be restored to rhythmicity, which has been attributed to a second oscillator, called the FLO (frq-less oscillator). This study reports additional conditions that allow this rhythmicity to occur. Rhythmicity was restored to mutants lacking either the frq, or wc-1, or wc-2 genes in D/D (constant darkness) or L/L (constant light) by the addition of low levels of menadione, a known stimulator of ROS (reactive oxygen species). Additional studies are reported on the rhythm effects from caffeine, a known cAMP phospho-diesterase inhibitor as well as the effects from mutations in the csp-1 gene, the rco-1 gene, and other genes. A theme ties all of these "downstream effects" together, i.e., they affect either components thought to be part of the conidiation process itself, or the RAS-cAMP-protein kinase pathway. Since mutations in these components unexpectedly had rhythm effects, this suggests that these components may be good candidates for some part of the frq-less oscillator.
The monoclonal antibody (MAb) VRC01 was isolated from a slowly progressing HIV-1-infected donor and was shown to neutralize diverse HIV-1 strains by binding to the conserved CD4 binding site (CD4bs) of gp120. To better understand the virologic factors associated with such antibody development, we characterized HIV-1 envelope (Env) variants from this donor and five other donors who developed broadly neutralizing antibodies. A total of 473 env sequences were obtained by single-genome amplification, and 100 representative env clones were expressed and tested for entry and neutralization sensitivity. While VRC01 neutralizes about 90% of the genetically diverse heterologous HIV-1 strains tested, only selective archival Env variants from the VRC01 donor were sensitive to VRC01 and all of the Env variants derived from the donor plasma were resistant, indicating strong antibody-based selection pressure. Despite their resistance to this broadly reactive MAb that partially mimics CD4, all Env variants required CD4 for entry. Three other CD4bs MAbs from the same donor were able to neutralize some VRC01 escape variants, suggesting that CD4bs antibodies continued to evolve in response to viral escape. We also observed a relatively high percentage of VRC01-resistant Env clones in the plasma of four of five additional broadly neutralizing donors, suggesting the presence of CD4bs-directed neutralizing antibodies in these donors. In total, these data indicate that the CD4bs-directed neutralizing antibodies exert ongoing selection pressure on the conserved CD4bs epitope of HIV-1 Env.
Related JoVE Video
Journal of Visualized Experiments
What is Visualize?
JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.
How does it work?
We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.
Video X seems to be unrelated to Abstract Y...
In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.