Professor, Department of Microbiology & Immunology
Research in our laboratory is focused on three areas of HIV: Biology, therapeutics and pathogenesis.
HIV Biology: We have a long-standing interest in in the early events of HIV-1 replication. In earlier work, we outlined the role of residues in the polymerase domain that determine the fidelity of DNA synthesis by RT. We are currently focused on cellular proteins that influence the viral reverse transcription process upon viral entry into a susceptible cell during infection.
Aptamer therapeutics: We are developing and testing the efficacy of novel, anti-HIV-1 RNA aptamers to inhibit HIV-1 replication in cell culture. Aptamers are sequences isolated by the iterative process of SELEX that are highly specific to their targets. The most efficacious aptamers identified in our laboratory as well as combinations of them will then be tested in nonhuman primates (macaque). We will introduce such aptamers into hematopoeitic stem cells, which will then be used in bone marrow transplantation followed by challenge with chimeric, pathogenic SHIVs. In earlier work, we have done considerable amount of work on anti-RT aptamers. We have now generated new aptamers to other viral targets including structural, catalytic and accessory proteins of HIV. We have shown that perturbing HIV-1 Gag and viral RNA interaction using anti-Gag aptamers can lead to downmodulation of viral RNA metabolism thus inhibiting virus production.
HIV associated Dementia: The severe form of HIV associated dementia (HAD) is common among clade-B HIV-infected individuals in the US and Western Europe, but less common among individuals infected with clade-C HIV-1 such as in India, suggesting that there are clade-specific differences in neuropathogenicity. Understanding clade-specific determinants of neuropathogenesis may shed light on the disease mechanism and help develop targeted drugs for HAD. Therefore, we are investigating neuropathogenesis induced by the two HIV-1 clades using SCID mouse HIV encephalitis model. It has previously been shown that introduction of clade B HIV into SCID mouse brain recapitulates the key features of the human HAD disease. In our studies, clade B (HIV-1ADA) or clade C (HIVIndie-C1) HIV-infected macrophages were injected intracranially into SCID mice. In cognitive tests, mice exposed to similar inputs of HIVIndie-C1 made fewer memory errors than those exposed to HIV-1ADA. Mice exposed to HIV-1ADA exhibited greater astrogliosis and loss of neuronal network integrity. In vitro differences were noted in another key characteristic of HIV-1 that influences HAD, the increased monocyte recruitment. HIV-1Indie-C1-infected macrophages recruited monocytes poorly in vitro compared to HIV-1ADA-infected macrophages. Monocyte recruitment was HIV-1 Tat-dependent. These results are in agreement with our striking observation previously that the Tat protein from clade C HIV-1 is a defective chemokine. This is the first demonstration, since HIV neuropathogenesis was first recognized, that genetic differences in different HIV-1 clades can affect disease severity. We are currently examining other clades as well as exploiting clade differences to identify viral determinants of HAD.
In ongoing work, we are identifying the genetic basis underlying some subtype C countries showing high incidence of HAD. In addition, we are also interested in understanding the mechanisms underlying the damage to blood-brain barrier caused by exposure to HIV infected cell supernatants in vitro.
Early Events of HIV-1 Replication
1. Hamburgh, M., Curr, K., Monaghan, M., Rao, V. R., Tripathi, S., Preston, B. D., Sarafianos, S, Arnold, E. A. and Prasad V. R. (2006) Structural determinants of slippage-mediated mutations by human immunodeficiency virus type 1 reverse transcriptase. J. Biol. Chem. 281:7421-7428.
2. Mandal, D., Dash, C. V., Le Grice, S. F. and Prasad V. R. (2006) Analysis of HIV-1 replication block due to substitutions at F61 residue of reverse transcriptase reveals additional defects involving RNase H function. Nuc. Acids Res. 34:2853-2863.
3. Garforth, S., Lee, T. W., Parniak, M. A., Kool, E. T. and Prasad, V. R. (2007) Site-directed mutagenesis in the fingers subdomain of HIV-1 reverse transcriptase reveals a specific role for the b3-b4 hairpin loop in dNTP selection. J. Mol. Biol. 365:38-49
4. Garforth, S.,Parniak, M. A. and Prasad, V. R. (2008) Utilization of deoxynucleoside diphosphates as substrate by a DNA polymerase. Plos One. 3(4):e2074.
5. Garforth, S. J., Domaoal, R. A., Lwatula, C., Landau, M. J., Meyer, A. J., Anderson, K. S. and Vinayaka Prasad (2010) K65R and K65A substitutions in HIV-1 reverse transcriptase enhance polymerase fidelity by decreasing both dNTP misinsertion and mispaired primer extension efficiencies. J. Mol. Biol. 401:33-44.
6. Lwatula, C., Garforth, SJ and Prasad, VR (2012) Lys66 as a determinant of high mismatch extension and misinsertion rates of HIV-1 reverse transcriptase FEBS J 2012 Aug 28. doi:10.1111/j.1742-4568.2012.08807.x.[Epub ahead of print]
7. Joshi, P. and Prasad, V. R. (2002) Potent inhibition of HV-1 replication by template analog reverse transcriptase inhibitors (TRTIs) derived by SELEX. J. Virol. 76:6545-6557.
8. Joshi. P., North, T. W. and Prasad, V. R. (2005) Aptamers Directed to HIV-1 Reverse Transcriptase Display Greater Efficacy over Small Hairpin RNAs Targeted to Viral RNA in Blocking HIV-1 Replication. Mol. Ther. 11:677-686.
9. Ramalingam, D, Duclair, S., Datta, S., Ellington, A.D., Rein, A. and Prasad, V. R. (2010) RNA aptamers directed to HIV-1 Gag bind to the matrix and nucleocapsid domains and inhibit virus production. J. Virol. 85:305-314.
10. Ranga, U., Shankarappa, R., Siddappa, N. B., Lakshmi, R., Nagendran, R., Mahalingam, M., Mahadevan, A., Jayasuryan, N., Satishchandra, P., Shankar, S.K. and Prasad, V. R. (2004)Tat protein of HIV-1subtype-C viruses is a defective chemokine. J. Virol. 78:2586-2590.
11. Dash, P. K., Siddappa, N. B., Mangaiarkarasi, A., Anand, K. K., Padmanabhan, R. B, Mahendarkar, A. V., Mahadevan, A., Satishchandra, P., Shankar, S. K., Prasad, V. R., Ranga, U. (2008) Expanded coreceptor use of Human Immunodeficiency Virus Type-1 subtype C molecular isolates from an Indian subject with HIV-1 associated dementia. Retrovirology. 5:25
12. Rao, V. R., Sas, A., Eugenin, E., Siddappa, N. B., Bimonte-Nelson, H., Berman, J., Ranga, U., Tyor, W. R. and Prasad, V. R. (2008) HIV-1 clade-specific differences in the induction of neuropathogenesis. J. Neurosci. 28:10010-6.
13. Neogi, U., Gupta, S., Sahoo, PN, Shet, A., Ranga, U. and Prasad, VR (2012) Genetic characterization of HIV type 1 Tat Exon 1 from a South Indian clinical cohort: Identification of unique epidemiological signature residues. AIDS Res. Hum Retroviruses 28:952-956.
More Information About Dr. Vinayaka Prasad
Material in this section is provided by individual faculty members who are solely responsible for its accuracy and content.
Albert Einstein College of Medicine
Jack and Pearl Resnick Campus
1300 Morris Park Avenue
Golding Building, Room 401
Bronx, NY 10461