Name: Intracerebroventricular and Intravascular Injection of Viral Particles and Fluorescent Microbeads into the Neonatal Brain (Video) | JoVE Journal
Uploaded: 2016-07-24T14:00:00.000+00:00
Duration: 5 min 51 s
Description: Learn intracerebroventricular and intravascular injection techniques to observe viral particle distribution in the neonatal mouse brain during acute infection. This method enables direct microscopic visualization for neurovirology research.

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5 minutes

The authors thank Mr. Masaaki Kaneta, Ms. Hiromi Suzuki, and Ms. Mitsue Kawashima (Department of Regenerative and Infectious Pathology, Hamamatsu University School of Medicine) for their excellent technical assistance. This work was supported by the Japan Society for the Promotion of Science, KAKENHI Grant Number 23590445.

All the experimental protocols were approved by the Animal Care Committee of Hamamatsu University of School of Medicine.
1. Preparation of MCMV (Smith strain) and Recombinant M32-enhanced Green Fluorescent Protein (EGFP)-MCMV
<ol>
	<li>Generate recombinant M32-EGFP-MCMV according to the method as follows (1.2 - 1.9) and as previously described8.</li>
	<li>Use recombinant viruses derived from the Smith strain of wild-type MCMV (accession number: U68299). Insert EGFP (4,361 base pairs; bp) between 37,089 and 41,450 bp (M32 - M31 locus) in the MCMV genome by homologous recombination.</li>
	<li>Amplify by polymerase chain reaction the MCMV M32 (41,450 - 39,286 bp, left flanking sequence and M31 (37,089 - 39,246 bp, right flanking sequence gene loci using the following primers: M32, 5&#8242;-CTACTAGCTAGCCTTCCGCGAGTCGCTGTATT-3&#8242; (forward primer), 5&#8242;-CTACTAGCTAGCCTTCCGCGAGTCGCTGTATT-3&#8242; (reverse primer); M31, 5&#8242;-CTAAATTAACTTAAGTCGTCCTCTTCGTCTCACAA-3&#8242; (forward primer), 5&#8242;-AACTAGTCTAGATCGCTCCTGGTTGGTTTTTA-3&#8242; (reverse primer).</li>
	<li>Insert the M32 locus into the EGFP-expressing vector using NheI and BamHI restriction sites. Insert the M31 locus into the M32-EGFP-recombinant plasmid using AflII and XbaI sites. Cleave the M32-EGFP-M31 sequence with NheI and AflII from the M32-EGFP-M31 recombination plasmid and dissolve in H2O.</li>
	<li>Transfect the cleaved construct into the nuclei of MCMV (Smith strain)-infected NIH3T3 cells 24 hr post-infection (hpi) using an electroporation system to induce homologous recombination.</li>
	<li>At 3 days post-infection, co-culture the cells with uninfected mouse embryonic fibroblasts (MEFs) at a ratio of 1/1,000 in six-well plates and screen for EGFP-expressing foci of infected cells.</li>
	<li>Harvest the virus-containing supernatants from the wells containing green fluorescent foci and dilute tenfold. For purification, choose wells that display single green fluorescent foci.</li>
	<li>When all foci resulting from the limiting-dilution infection display EGFP expression, the virus preparation is pure, indicating that no wild-type virus remains. Quantify the virus by the plaque-assay method as previously described17.</li>
	<li>Treat MCMV in certified biosafety cabinets at biosafety level 2 wearing gloves and mask.</li>
	<li>Passage MCMV (Smith strain) and recombinant MCMV in MEFs prepared from 12-day-old ICR mouse embryos as previously described17.</li>
	<li>Remove cells from the supernatants of infected MEF cultures by centrifugation at 3,000 &#215; g for 20 min at 16 &#176;C.</li>
	<li>Ultracentrifuge the supernatants for 40 min at 70,000 &#215; g. Resuspend the pellets containing virions in 1 ml of Tris-buffered saline and transfer onto a preformed linear sorbitol gradient (25% - 70%). Ultracentrifuge again at 70,000 x g for 60 min18.</li>
	<li>Harvest the virion-containing band with a syringe. Pellet the harvested virions by an additional ultracentrifugation step at 70,000 &#215; g for 40 min.</li>
	<li>Resuspend the pellet in 1 ml of phosphate-buffered saline (PBS) and store at -80 &#176;C until the infection experiments.</li>
	<li>Quantify the virus titer by the plaque-assay method as previously described19.</li>
	<li>Visualize the EGFP expression of the recombinant MCMV particles (excitation at 489 nm, emission at 508 nm) by fluorescent microscopy (Figure 1A) and the particle structure by transmission electron microscopy (TEM)8 (Figure 1B).</li>
</ol>
2. Preparation of Nile Red Fluorescent Microbeads
<ol>
	<li>Purchase carboxyl fluorescent Nile red microbeads and place 500 &#181;l of microbeads into tubes according to diameter (0.04 - 0.06 &#181;m, approximately 3.63 &#215; 1012 particles; 0.1 - 0.3 &#181;m, approximately 5.75 &#215; 1010 particles; and 1.7 - 2.2 &#181;m, approximately 6.85 &#215; 107 particles).</li>
	<li>Treat beads with 500 &#181;l of 0.1 M NaOH for approximately 1 day to remove any endotoxins and resuspend the beads in sterile water at RT.</li>
	<li>Adsorb the beads O/N with 10% mouse serum obtained from C57BL/6 mice at RT prior to use.</li>
	<li>To separate aggregates, vortex the beads and sonicate thoroughly before use.</li>
</ol>
3. ICV Injection of MCMV and Fluorescent Microbeads into Neonatal Mice
<ol>
	<li>Maintain normal pregnant ICR mice in a temperature-controlled facility under a 12 hr light/dark cycle. The neonates are designated as P 0.5 on the day of birth.</li>
	<li>Sterilize a 10-&#181;l syringe and a 27 G&#160;needle with 70% alcohol.</li>
	<li>Load the injection solution (5 &#181;l) containing MCMV or fluorescent microbeads into the needle by carefully pulling the plunger of the syringe.</li>
	<li>Restrain neonatal mouse (P 0.5) by putting the mouse on ice for 3 - 4 min. Once the animal is under anesthesia, use the toe-pinch response method to determine the depth of anesthesia.</li>
	<li>Mark the injection site with a non-toxic laboratory pen at a location approximately 0.7 - 1.0 mm lateral to the sagittal suture and 0.7 - 1.0 mm caudal from the neonatal bregma (Figure 2A).</li>
	<li>Insert the needle 2 mm deep, perpendicular to the skull surface at the marked injection site. For reference, mark 2 mm from the tip of needle with a non-toxic maker.</li>
	<li>Slowly inject 5 &#181;l of MCMV (approximately 5 &#215; 105 PFU) into the lateral ventricle without opening the scalp (Figure 2B).</li>
	<li>In another group of mice, inject a 5 &#181;l solution containing fluorescent microbeads (0.1 - 0.3 &#181;m, approximately 5.75 &#215; 108 particles) by the same method.</li>
	<li>Slowly remove the needle 10 - 20 sec after discontinuing the plunger movement to prevent backflow.</li>
	<li>To recover, keep the mice for 5 - 10 min in a warm container until movement and general responsiveness are restored.</li>
	<li>Harvest the brains as described in section 5 at a range of time points (3, 12, 24, 48, and 72 hr) post-injection.</li>
</ol>
4. IV Injection of MCMV or Fluorescent Microbeads into Neonatal Mice
<ol>
	<li>Restrain neonatal mouse (P 0.5) by putting the mouse on ice for 3 - 4 min.</li>
	<li>Use a 1-ml syringe with a 35 G needle to perform the intravenous injection of MCMV in P 0.5 neonates.</li>
	<li>Use a transilluminator (vein finder) to visualize the superficial temporal (facial) vein. Before injection, secure the neonate to the transilluminator using surgical tape (Figure 2C).</li>
	<li>While wearing magnifying glasses (1.5X), slowly infuse 50 &#181;l of MCMV (approximately 5.45 &#215; 109 particles) or fluorescent microbeads (0.04 - 0.06 &#181;m, approximately 3.63 &#215; 1011 particles; 0.1 - 0.3 &#181;m, approximately 5.75 &#215; 109 particles; and 1.7 - 2.2 &#181;m, approximately 6.85 &#215; 106 particles) into the superficial temporal vein (Figure 2D).</li>
	<li>After removing the needle, use gauze containing 70% alcohol to apply pressure to the injection site until the bleeding ceases.</li>
	<li>Give the neonate approximately 5 min in a warm container to recover before returning it to the cage.</li>
	<li>Harvest the brains as described in section 5 at a range of time points (3, 12, 24, and 72 hr) post-injection.</li>
</ol>
5. Brain Tissue Sample Preparation for Paraffin Sections
<ol>
	<li>Place the injected neonates in a small plastic dish&#160;on crushed ice.</li>
	<li>Once the animal is under anesthesia, use the toe-pinch response method to determine the depth of anesthesia.</li>
	<li>Make one central or two end horizontal end cuts through the rib cage to open up the thoracic cavity.</li>
	<li>Make a cut in the atrium with sharp scissors. Infuse 4% paraformaldehyde (PFA) solution into the atrium. Stop perfusion when spontaneous movement (PFA dance) and lightened-color of the liver are observed. Do not exsanguinate.</li>
	<li>Dissect the neonate (as previously described20) by first removing the head using a pair of scissors.</li>
	<li>Make a midline incision along the integument from the neck to the nose to expose the skull.</li>
	<li>Place the sharp end of a pair of iris scissors into the foramen magnum on one side, carefully sliding along the inner surface of the skull.</li>
	<li>Make a cut extending to the distal edge of the posterior skull surface, and make an identical cut on the contralateral side. Clear away the skull around the cerebellum.</li>
	<li>Carefully peel back the skull on one side to prevent damage to the brain. Repeat this procedure on the other side of the brain.</li>
	<li>Using a spatula, sever the olfactory bulbs and nervous connections along the ventral surface of the brain.</li>
	<li>Gently separate the brain from the head, trimming any dura that still connect the brain to the skull using scissors, and remove the brain.</li>
	<li>Place the brain in a vial of fixative containing 4% PFA at least 10 times the volume of the brain for 24 hr at 4&#176;C.</li>
	<li>Dehydrate the tissue through a series of graded ethanol baths to displace the water, and then infiltrate with paraffin wax, forming a block. Cut the paraffin block with a microtome into slices 4 &#181;m thick21.</li>
	<li>Deparaffinize and rehydrate the slides of the infected brains22. Proceed to in situ hybridization for paraffin embedded sections.</li>
</ol>
6. Brain Tissue Sample Preparation for Frozen Sections
<ol>
	<li>Remove the brain following the steps outlined in 5.1 - 5.11.</li>
	<li>To observe the fluorescent microbeads and M32-EGFP-MCMV, place the resected brain on flat bottom cryomolds. Add embedding medium to completely cover the brain sample. Snap freeze the cryomolds in precooled n-hexane (-80 &#186;C), using forceps to hold the edge of the cryomolds prior to attaching it to the chuck.</li>
	<li>For sectioning, attach the frozen tissue block on the precooled cryostat chuck. Transfer the frozen tissue with the chuck into a cryostat chamber and lower the temperature to between -10 and -20 &#176;C, and cut the slices approximately 8 - 10 &#181;m thick23.</li>
	<li>Fix the sections with cytofixative (mixture of isopropyl alcohol and polyethylene glycol) by spraying. Air dry the sections for 30 min at RT immediately after spraying, and store them at - 80 &#186;C until further use.</li>
	<li>Equilibrate the sections back to RT and wash three times with PBS.</li>
	<li>Stain the sections with fluorescein isothiocyanate (FITC)-conjugated Griffonia simplicifolia isolectin B4 at a concentration of 1:100 for 10 min in PBS at RT (Figure 5) or with PE-conjugated CD31 antibody at a concentration of 1:100 for 30 min in PBS at RT (Figure 6).</li>
	<li>Wash the sections with PBS three times.</li>
	<li>After the washing, stain the sections with 4&#8242;,6-diamidino-2-phenylindole (DAPI) to visualize cell nuclei. Mount the sections in anti-fade reagent and image DAPI (excitation at 345 nm, emission at 455 nm), EGFP (excitation at 489 nm, emission at 508 nm), and Nile red (excitation at 553 nm, emission at 637 nm) with a fluorescent microscope (Figures 3, 5, 6).</li>
</ol>
7. Fluorescent in situ Hybridization (FISH) for Paraffin Embedded Sections
<ol>
	<li>Prepare the FISH probe labeled directly with fluorophore for DNA in situ hybridization by nick translation using a bacterial artificial chromosome containing the whole MCMV DNA genome (pSM3fr)19. The concentration of the FISH probe is 0.1 &#181;g/&#181;l.</li>
	<li>Deparaffinize and rehydrate the slides of the infected brains22.</li>
	<li>Treat the tissue sections with RNase (100 &#181;g/ml in PBS) to detect viral DNA.</li>
	<li>Perform antigen retrieval with a 0.05% NP40, 0.01 M citrate buffer (pH 6.0) at 95 - 98&#176;C for 20 min. Cool the slides down to RT for 20 min.</li>
	<li>In a glass Coplin staining jar, wash the slides in pure water three times for 2 min each time. Perform an additional antigen retrieval step with a 0.06% pepsin, 0.01 N HCl solution for 5 min at 37 &#176;C.</li>
	<li>Rinse slides three times in pure water for 2 min each time in a glass Coplin staining jar.</li>
	<li>Dehydrate the tissue sections again by transferring the slides from 70% ethanol, to 85% ethanol, and then to 100% ethanol.</li>
	<li>For preparing 10 ml of the hybridization buffer, mix 1.25 ml in situ hybridization salts (3 M NaCl, 100 mM Tris-HCl pH 8.0, 100 mM sodium phosphate pH 6.8, 50 mM EDTA) with 5 ml deionized formamide, 2.5 ml 50% Dextran sulfate, 250 &#181;l 50x Denhardt&#39;s solution, 125 &#181;l 100 mg/ml tRNA, and 875 &#181;l H2O.</li>
	<li>Dilute the DNA probe directly labeled with fluorophores that recognize the whole MCMV genome randomly in the hybridization buffer. The final volume should be 10 &#181;l (7 &#181;l hybridization buffer, 1 &#181;l probe (0.1 &#181;g/&#181;l), and 2 &#181;l distilled water).</li>
	<li>Add the probe mix (10 &#181;l) to each slide and cover with a coverslip (15 &#215; 15 mm). Seal the coverslip with rubber cement. Denature the probe mix for 5 min at 85 &#176;C, and complete the hybridization step O/N at 42 &#176;C.</li>
	<li>Wash the slides with 0.3% NP40, 0.4x SSC at 73&#176;C for 2 min; with 0.1% NP40, 0.4x SSC at 73 &#176;C for 1 min; and with 2x SSC twice.</li>
	<li>Counterstain the nuclei with DAPI (10 ng/ml) and cover the slide with a coverslip.</li>
	<li>Mount the sections in anti-fade reagent and image DAPI (excitation at 345 nm, emission at 455 nm) and EGFP (excitation at 489 nm, emission at 508 nm) with a fluorescent microscope (Figure 4).</li>
</ol>

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</ol>

The authors have nothing to disclose.

In animal models, ICV, intraperitoneal, direct placental, and IV infections have been used to study the pathogenesis of viral encephalitis. We focused on the ICV and IV injection models of neonatal mice for the simplicity of the procedures and the benefit of direct injection of particles into the target region. Although intraperitoneal infection is an easy method, viral particles spread systemically via an indirect process5,24. Direct placental infection is a good method to study embryonic systemic infection. ...

When studying viral encephalitis, the initial distribution of viral particles is very important to understand disease pathogenesis and to identify viral targets in the brain. Most viruses range in size from 20 to 300 nm, although the Pandoravirus is more than 700 nm in size1. The distribution of the viral particles in the acute phase of infection may depend on the size of the particles, the distribution of cellular receptors, or the affinity of the cellular receptors for viruses. In animal models, intracerebroventricular (ICV), intraperitoneal, direct placental, and intravenous (IV) infections have been used to study the pathogenesis of viral encephalitis. ICV inoculation with virus is often used to establish central nervous system (CNS) infections in mice. Studies using this technique report widespread infection, particularly of cells in the periventricular zones and in regions of the brain in direct contact with the cerebrospinal fluid (CSF), similar to the effects of viral ventriculoencephalitis. The small size of adeno-associated virus (AAV) particles (20 - 25 nm in diameter) facilitates their dissemination throughout the brain in ICV infections2-4. Intraperitoneal5, direct placental6, and IV injections7 represent hematogenic systemic administration. The penetration of viral particles through the blood-brain barrier (BBB) allows them to reach the parenchyma of the neonatal brain, representing diffuse microglial nodules8,9.
Cytomegalovirus (CMV) is a common virus that belongs to the herpes virus family. In the United States, 50% - 80% of the people have had CMV infection by age 40. CMV infections are rarely harmful but can cause diseases in immunocompromised patients and fetuses. Of all deliveries, 0.2% - 2% are born with CMV10, resulting in severe symptoms such as microcephaly, periventricular calcification, cerebellar hypoplasia, microphthalmia, and optic nerve atrophy11,12. Furthermore, mental retardation, sensorineural hearing loss, visual defects, seizure, and epilepsy occur in about 10% of non-fatally CMV-infected infants13,14. CNS dysfunction is the most common characteristic symptom of CMV congenital anomaly. More children are permanently disabled each year by congenital CMV than by Down syndrome, fetal alcohol syndrome, or spina bifida15. There are no vaccinations against CMV available at the present, calling for a need of a safe and effective vaccine. Studying the interaction of CMV particles with their receptors in the earliest phase of infection is important to understand the effect of vaccination.
Ventriculoencephalitis and diffuse microglial nodules are the two main pathological characteristics of CMV encephalitis16. It has been uncertain how the CMV particles (150 - 300 nm) spread through the brain in the acute phase of infection and how the distribution of cellular receptors and their affinity for viruses contribute to the viral spread. Kawasaki et al. have evaluated ICV and IV infections from the perspective of the distribution of particles and their receptors (&#946;1 integrin) in the earliest phase of infection. We have found that the dissemination of CMV particles and the expression of &#946;1 integrin are well correlated in the earliest phase of infection in both ICV and IV infections8. ICV infection is a model of ventriculoencephalitis and IV infection is a model of diffuse microglial nodules. Studying the dynamics of viral or fluorescent particles would give useful information on the effect of particle size, viral interactions with cellular receptors, and the mechanism of BBB penetration in the brain. The following protocol could be used to investigate any viral infection and viral vector in the CNS.

<table><tbody><tr><td>Tris; tris(hydroxymethyl)- aminomethane</td><td>Sigma-Aldrich</td><td>T-6791</td><td></td></tr><tr><td>HCl</td><td>Sigma-Aldrich</td><td>H-1758</td><td></td></tr><tr><td>pEGFP-N1 vector&amp;nbsp;</td><td>Clontech</td><td>#6085-1</td><td></td></tr><tr><td>D-sorbitol</td><td>Sigma-Aldrich</td><td>S-1876</td><td></td></tr><tr><td>SPHERO TM Fluorescent Polystyrene Nile Red 0.04 - 0.06</td><td>Spherotech, Inc.</td><td>FP-00556-2</td><td></td></tr><tr><td>SPHERO TM Fluorescent Polystyrene Nile Red 0.1 - 0.3</td><td>Spherotech, Inc.</td><td>FP-0256-2</td><td></td></tr><tr><td>SPHERO TM Fluorescent Polystyrene Nile Red 1.7 - 2.2</td><td>Spherotech, inc.&amp;nbsp;</td><td>FP-2056-2</td><td></td></tr><tr><td>10% mouse serum</td><td>DAKO&amp;nbsp;</td><td>X0910</td><td></td></tr><tr><td>C57BL/6 mouse</td><td>SLC, Inc.</td><td></td><td></td></tr><tr><td>ICR mouse</td><td>SLC, Inc.</td><td></td><td></td></tr><tr><td>Modified Microliter Syringes (7000 Series)</td><td>Hamilton company</td><td></td><td></td></tr><tr><td>35-gauge needle</td><td>Saito Medical</td><td></td><td></td></tr><tr><td>A Wee Sight Transilluminator</td><td>Phillips Healthcare</td><td>1017920</td><td></td></tr><tr><td>O.C.T.Compound</td><td>Sakura Finetek</td><td>4583</td><td></td></tr><tr><td>RNase A</td><td>Sigma-Aldrich</td><td>R4642</td><td></td></tr><tr><td>Nonidet(R) P-40</td><td>Nacalai</td><td>25223-04</td><td></td></tr><tr><td>citrate buffer (pH 6) x 10</td><td>Sigma-Aldrich</td><td>C9999-100ml</td><td></td></tr><tr><td>pepsin</td><td>Sigma-Aldrich</td><td>P6887</td><td></td></tr><tr><td>EDTA</td><td>dojindo</td><td>N001</td><td></td></tr><tr><td>Formamide</td><td>TCI</td><td>F0045</td><td></td></tr><tr><td>Dextran sulfate sodium salt</td><td>Sigma-Aldrich</td><td>42867-5G</td><td></td></tr><tr><td>Denhardt&#039;s Solution (50x)</td><td>ThermoFishcer sceintific</td><td>750018</td><td></td></tr><tr><td>Yeast tRNA (10 mg/ml)</td><td>ThermoFishcer sceintific</td><td>AM7119</td><td></td></tr><tr><td>SSC 20x</td><td>Sigma-Aldrich</td><td>S6639</td><td></td></tr><tr><td>DAPI</td><td>ThermoFishcer sceintific</td><td>D1306</td><td></td></tr><tr><td>n-Hexane</td><td>Sigma-Aldrich</td><td>296090</td><td></td></tr><tr><td>superfrost plus glass</td><td>ThermoFishcer sceintific</td><td>12-55-18</td><td></td></tr><tr><td>Cytokeep II</td><td>Nippon Shoji Co.</td><td></td><td></td></tr><tr><td>FITC-conjugated Griffonia simplicifolia isolectin B4</td><td>Vector laboratories, Inc.</td><td>L1104</td><td></td></tr><tr><td>Anti-Mouse CD31 (PECAM-1) PE</td><td>ebioscience</td><td>12-0311</td><td></td></tr><tr><td>ProLong&amp;nbsp; Gold</td><td>ThermoFishcer sceintific</td><td>P36934</td><td></td></tr><tr><td>BIOREVO</td><td>KEYENCE</td><td>BZ-9000E</td><td></td></tr></tbody></table>

intracerebroventricular and intravascular injection of viral particles and fluorescent microbeads into the neonatal brain

Intracerebroventricular and Intravascular Injection of Viral Particles and Fluorescent Microbeads into the Neonatal Brain

In the study on the pathogenesis of viral encephalitis, the infection method is critical. The first of the two main infectious routes to the brain is the hematogenous route, which involves infection of the endothelial cells and pericytes of the brain. The second is the intracerebroventricular (ICV) route. Once within the central nervous system (CNS), viruses may spread to the subarachnoid space, meninges, and choroid plexus via the cerebrospinal fluid. In experimental models, the earliest stages of CNS viral distribution are not well characterized, and it is unclear whether only certain cells are initially infected. Here, we have analyzed the distribution of cytomegalovirus (CMV) particles during the acute phase of infection, termed primary viremia, following ICV or intravascular (IV) injection into the neonatal mouse brain. In the ICV injection model, 5 &#181;l of murine CMV (MCMV) or fluorescent microbeads were injected into the lateral ventricle at the midpoint between the ear and eye using a 10-&#181;l syringe with a 27 G needle. In the IV injection model, a 1-ml syringe with a 35 G needle was used. A transilluminator was used to visualize the superficial temporal (facial) vein of the neonatal mouse. We infused 50 &#181;l of MCMV or fluorescent microbeads into the superficial temporal vein. Brains were harvested at different time points post-injection. MCMV genomes were detected using the in situ hybridization method. Fluorescent microbeads or green fluorescent protein expressing recombinant MCMV particles were observed by fluorescent microscopy. These techniques can be applied to many other pathogens to investigate the pathogenesis of encephalitis.

In studies on the pathogenesis of viral encephalitis, the infection method is important. The hematogenous route represents an acute infection of the endothelial cells and pericytes of the brain, while the ICV route represents an acute infection spreading via the CSF through the subarachnoid space, reaching to the meninges and choroid plexus. To analyze the first distribution of particles in acute encephalitis, in situ hybridization detecting the MCMV genomes and direct observatio...

Here, we describe a simple method of intracerebroventricular and intravascular injection of viral particles or fluorescent microbeads into the neonatal mouse brain. The localization pattern of the virus and nanoparticles could be detected by microscopic evaluation or by in situ hybridization.

In the study on the pathogenesis of viral encephalitis, the infection method is critical. The first of the two main infectious routes to the brain is the ...

The overall goal of this procedure is to observe the distribution of viral particles during the acute phase of infection in the central nervous system. This method can help answer key questions in the neurovirology field. Such as how do virus particles distribute in the immature central nervous system during the acute infection phase.The main advantage of this technique is that the initial distribution of viral particles can be observed directly with a microscope using two simple methods. Such as intercerebroventricular and intravascular injection. Begin my sterilizing a 10 microliter syringe and a 27 gauge needle with 70%alcohol.Then load five microliters of murine cytomegalovirus injection solution or fluorescent microbeads into the needle by carefully pulling the plunger of the syringe. After anesthetizing and immobilizing a PO.5 neonatal mouse by placing it on ice for three to four minutes, use the toe pinch response method to determine the depth of anesthesia. Mark the injection site on the anesthetized mouse with a non toxic laboratory pen at a location approximately 0.7 to 1.0 mm lateral to the saggital suture and 0.7 to 1.0 mm cuddle from the neonatal bregma.This diagram shows the site in more detail. For reference, mark 2 mm from the tip of the needle with a non toxic marker. Next, insert the needle 2 mm deep perpendicular to the skull surface at the marked injection site.Then slowly inject 5 microliters of murine cytomegalovirus into the lateral ventricle without opening the scalp. In another group of mice inject a 5 microliter solution containing fluorescent microbeads by the same method. After injection, allow the needle to remain in place for 10 to 20 seconds to prevent backflow.Then slowly remove the needle. Allow the injected animals to recover for 5 to 10 minutes in a warm container until movement and general responsiveness are restored. For intravenous injection secure the anesthetized neonate to the transilluminator using surgical tape and then visualize the superficial temporal vein.Next, while wearing 1.5x magnifying glasses use a 1 ml syringe with a 35 gauge needle to slowly infuse 50 microliters of murine cytomegalovirus virus into the superficial temporal vein. Again repeat the procedure with fluorescent microbeads of the appropriate size in the control group. After removing the needle use gauze containing 70%alcohol to apply pressure to the injection site until the bleeding ceases.Give the neonate approximately five minutes in a warm container to recover before returning it to the cage. Two hours after introcerbroventricular injection in the acute infection phase green recombinant M32 EGFP MCMV particles are mainly observed in the marginal area as indicated by the arrows and seen in the magnified region. At this time the M32 EGFP MCMV particles are also seen in the choroid plexus and subventricular zone.The MCMV genome is first detected in the subventricular zone at three hours post intracerebralventricular injection. Using fluorescent and C2 hybridization the MCV genome is visible as green spots and indicated by arrows in this magnified region. At three hours post intravenous injection the MCMV particles visible as green spots and indicated by arrows are found inside and outside of the vascular area of the parenchyma, as this increased magnification image demonstrates.At this time the MCMV particles are still visible in the choroid plexus and subventricular zone. Using fluorescent and C2 hybridization the MCMV genome is detected in the vascular area and meninges at 12 hours post IV injection. As indicated by the arrows.Once mastered, this technique can be done in five minutes if it is performed properly. After watching this video you should have a good understanding of how to observe the distribution of viral particles during the acute phase of infection in the central nervous system. Don't forget that working with a virus can be extremely hazardous and precaution such as wearing masks and gloves should always be taken while performing this procedure.

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Research

JoVE Journal

Neuroscience

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An Intracerebroventricular Injection to Analyze Murine Cytomegalovirus Distribution in a Neonatal Mouse Brain

Human Cytomegalovirus (HCMV) infection of neonates represents an important cause of mental retardation, yet the molecular events leading to virus-induced pathogenesis are still poorly understood. To investigate the dynamics of brain infection, we adapted whole-animal in vivo imaging to perform time-course analysis of neonates infected with a luciferase-recombinant virus.

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Intravenous Injections in Neonatal Mice

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Learn intracerebroventricular and intravascular injection techniques to observe viral particle distribution in the neonatal mouse brain during acute infection. This method enables direct microscopic visualization for neurovirology research.

Intracerebroventricular and Intravascular Injection of Viral Particles and Fluorescent Microbeads into the Neonatal Brain

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