Samir K Lakhashe

Publications of Samir K Lakhashe

• No Acquisition: a New Ambition for HIV Vaccine Development?

  Authors: Samir K Lakhashe, Guido Silvestri, Ruth M Ruprecht

  Current opinion in virology. 10/2011; 1(4):246-253.

  Development of a safe and effective prophylactic HIV-1 vaccine presents unique challenges. The pessimism following the failure of two HIV-1 vaccine concepts in clinical trials, HIV-1 gp120 and anDevelopment of a safe and effective prophylactic HIV-1 vaccine presents unique challenges. The pessimism following the failure of two HIV-1 vaccine concepts in clinical trials, HIV-1 gp120 and an adenovirus-based approach to induce only cellular immune responses, has been replaced by cautious optimism engendered by the RV144 trial outcome, the isolation of several new broadly reactive neutralizing monoclonal antibodies, and recent primate model data indicating prevention of viral acquisition by active or passive immunization. Intense efforts are underway to optimize immunogen design, adjuvants, and the tools for preclinical evaluation of candidate vaccines in primates, where correlates of protection can be examined in detail - as proof-of-concept for clinical trials.

• High-level, lasting antiviral immunity induced by a bimodal AIDS vaccine and boosted by live-virus exposure: prevention of viremia.

  Authors: Robert A Rasmussen, Nagadenahalli B Siddappa, Samir K Lakhashe, Jennifer Watkins, François Villinger, Chris Ibegbu, Ruth H Florese, Marjorie Robert-Guroff, David C Montefiori, Donald N Forthal, David O'Connor, Ruth M Ruprecht

  AIDS (London, England). 09/2011; 26(2):149-55.

  To characterize the correlates of protection from systemic infection in a vaccinated rhesus macaque, RAt-9, which had been challenged sequentially with two related clade C simian/humanTo characterize the correlates of protection from systemic infection in a vaccinated rhesus macaque, RAt-9, which had been challenged sequentially with two related clade C simian/human immunodeficiency viruses (SHIV-Cs) yet remained aviremic for more than 5 years despite indirect evidence of cryptic infection. To measure long-term anti-SHIV-C immunity, host genetics and gene-expression patterns for protective correlates. Long-term immune reactivity was evaluated and identification of virus in RAt-9 was attempted by RT-PCR analysis of concentrated plasma and blood transfer to CD8(+) cell-depleted infant macaques. Full MHC genotyping of RAt-9, TRIM5α and KIR3DL allelic expression analysis of PBMC, and microarray gene expression analysis were performed. All attempts to detect/isolate virus, including blood transfer to CD8(+) cell-depleted infant rhesus macaques, were negative, and the animal maintained normal levels of memory CD4(+) T cells in both peripheral blood and gut tissues. However, RAt-9 maintained high levels of anti-SHIV-C humoral and cellular immunity, including reactivity to nonvaccine neoantigens (Nef and Rev), up to 63 months postinitial challenge, suggesting chronic sub-threshold infection. RAt-9 expressed the Mamu A*001 allele negative for B*008 and B*017, had a B13 serotype, and had increased expression of killer-cell immunoglobulin-like receptors (KIRs) previously linked to favorable outcomes of lentiviral infection. Elements of the gene expression profiling coincided with genotyping results. RAt-9 also displayed CD8 cell noncytotoxic antiviral response (CNAR) activity. Monkey RAt-9 is the first example of a virus-exposed, persistently aviremic animal that has maintained long-term, high-level cellular and humoral antiviral immunity in the absence of an identifiable cryptic reservoir.

• Prime-boost vaccination with heterologous live vectors encoding SIV gag and multimeric HIV-1 gp160 protein: efficacy against repeated mucosal R5 clade C SHIV challenges.

  Authors: Samir K Lakhashe, Vijayakumar Velu, Gaia Sciaranghella, Nagadenahalli B Siddappa, Janet M Dipasquale, Girish Hemashettar, John K Yoon, Robert A Rasmussen, Feng Yang, Sandra J Lee [......] Rama Rao Amara, Maria Kahn, Shiu-Lok Hu, Sufen Li, Zhongxia Li, Fred R Frankel, Marjorie Robert-Guroff, Welkin E Johnson, Judy Lieberman, Ruth M Ruprecht

  Vaccine. 06/2011; 29(34):5611-22.

  We sought to induce primate immunodeficiency virus-specific cellular and neutralizing antibody (nAb) responses in rhesus macaques (RM) through a bimodal vaccine approach. RM were immunizedWe sought to induce primate immunodeficiency virus-specific cellular and neutralizing antibody (nAb) responses in rhesus macaques (RM) through a bimodal vaccine approach. RM were immunized intragastrically (i.g.) with the live-attenuated Listeria monocytogenes (Lm) vector Lmdd-BdopSIVgag encoding SIVmac239 gag. SIV Gag-specific cellular responses were boosted by intranasal and intratracheal administration of replication-competent adenovirus (Ad5hr-SIVgag) encoding the same gag. To broaden antiviral immunity, the RM were immunized with multimeric HIV clade C (HIV-C) gp160 and HIV Tat. SIV Gag-specific cellular immune responses and HIV-1 nAb developed in some RM. The animals were challenged intrarectally with five low doses of R5 SHIV-1157ipEL-p, encoding a heterologous HIV-C Env (22.1% divergent to the Env immunogen). All five controls became viremic. One out of ten vaccinees was completely protected and another had low peak viremia. Sera from the completely and partially protected RM neutralized the challenge virus > 90%; these RM also had strong SIV Gag-specific proliferation of CD8⁺ T cells. Peak and area under the curve of plasma viremia (during acute phase) among vaccinees was lower than for controls, but did not attain significance. The completely protected RM showed persistently low numbers of the α4β7-expressing CD4⁺ T cells; the latter have been implicated as preferential virus targets in vivo. Thus, vaccine-induced immune responses and relatively lower numbers of potential target cells were associated with protection.

• Vaccination against heterologous R5 clade C SHIV: prevention of infection and correlates of protection.

  Authors: Samir K Lakhashe, Wendy Wang, Nagadenahalli B Siddappa, Girish Hemashettar, Patricia Polacino, Shiu-Lok Hu, François Villinger, James G Else, Francis J Novembre, John K Yoon, Sandra J Lee, David C Montefiori, Ruth M Ruprecht, Robert A Rasmussen

  PloS one. 01/2011; 6(7):e22010.

  A safe, efficacious vaccine is required to stop the AIDS pandemic. Disappointing results from the STEP trial implied a need to include humoral anti-HIV-1 responses, a notion supported by RV144 trialA safe, efficacious vaccine is required to stop the AIDS pandemic. Disappointing results from the STEP trial implied a need to include humoral anti-HIV-1 responses, a notion supported by RV144 trial data even though correlates of protection are unknown. We vaccinated rhesus macaques with recombinant simian immunodeficiency virus (SIV) Gag-Pol particles, HIV-1 Tat and trimeric clade C (HIV-C) gp160, which induced cross-neutralizing antibodies (nAbs) and robust cellular immune responses. After five low-dose mucosal challenges with a simian-human immunodeficiency virus (SHIV) that encoded a heterologous R5 HIV-C envelope (22.1% divergence from the gp160 immunogen), 94% of controls became viremic, whereas one third of vaccinees remained virus-free. Upon high-dose SHIV rechallenge, all controls became infected, whereas some vaccinees remained aviremic. Peak viremia was inversely correlated with both cellular immunity (p<0.001) and cross-nAb titers (p<0.001). These data simultaneously linked cellular as well as humoral immune responses with the degree of protection for the first time.

• An anti-HIV-1 V3 loop antibody fully protects cross-clade and elicits T-cell immunity in macaques mucosally challenged with an R5 clade C SHIV.

  Authors: Jennifer D Watkins, Nagadenahalli B Siddappa, Samir K Lakhashe, Michael Humbert, Anton Sholukh, Girish Hemashettar, Yin Ling Wong, John K Yoon, Wendy Wang, Francis J Novembre [......] Chris Ibegbu, Kalpana Patel, Davide Corti, Gloria Agatic, Fabrizia Vanzetta, Siro Bianchi, Jonathan L Heeney, Federica Sallusto, Antonio Lanzavecchia, Ruth M Ruprecht

  PloS one. 01/2011; 6(3):e18207.

  Neutralizing antibodies have been shown to protect macaques against SHIV challenge. However, genetically diverse HIV-1 clades have evolved, and a key question left unanswered is whether neutralizingNeutralizing antibodies have been shown to protect macaques against SHIV challenge. However, genetically diverse HIV-1 clades have evolved, and a key question left unanswered is whether neutralizing antibodies can confer cross-clade protection in vivo. The novel human monoclonal antibody HGN194 was isolated from an individual infected with an HIV-1 clade AG recombinant circulating recombinant form (CRF). HGN194 targets an epitope in the third hypervariable loop (V3) of HIV-1 gp120 and neutralizes a range of relatively neutralization-sensitive and resistant viruses. We evaluated the potential of HGN194 to protect infant rhesus monkeys against a SHIV encoding a primary CCR5-tropic HIV-1 clade C envelope. After high-dose mucosal challenge, all untreated controls became highly viremic while all HGN194-treated animals (50 mg/kg) were completely protected. When HGN194 was given at 1 mg/kg, one out of two monkeys remained aviremic, whereas the other had delayed, lower peak viremia. Interestingly, all protected monkeys given high-dose HGN194 developed Gag-specific proliferative responses of both CD4+ and CD8+ T cells. To test whether generation of the latter involved cryptic infection, we ablated CD8+ cells after HGN194 clearance. No viremia was detected in any protected monkeys, thus ruling out virus reservoirs. Thus, induction of CD8 T-cell immunity may have resulted from transient "Hit and Run" infection or cross priming via Ag-Ab-mediated cross-presentation. Together, our data identified the HGN194 epitope as protective and provide proof-of-concept that this anti-V3 loop mAb can prevent infection with sterilizing immunity after challenge with virus of a different clade, implying that V3 is a potential vaccine target.

• Bimodal AIDS vaccine approach: induction of cellular as well as humoral immunity can protect from systemic infection.

  Authors: Robert A Rasmussen, Samir K Lakhashe, Ruth M Ruprecht

  Vaccine. 05/2010; 28 Suppl 2:B25-31.

  HIV clade C (HIV-C) strains comprise approximately 56% of all HIV infections worldwide, and AIDS vaccines intended for global use must protect against this subtype. Our vaccine strategy has been toHIV clade C (HIV-C) strains comprise approximately 56% of all HIV infections worldwide, and AIDS vaccines intended for global use must protect against this subtype. Our vaccine strategy has been to induce balanced antiviral immunity consisting of both neutralizing antibody and cell-mediated immune responses, an approach we tested in primates. As reported earlier, after isolating recently transmitted HIV-C strains from Zambian infants, we used env from one such virus, HIV1084i, to generate a multimeric gp160 immunogen. From another virus, isolated from a different child of the same mother-infant cohort, we cloned env to generate a recombinant simian-human immunodeficiency virus (SHIV), which was adapted to rhesus monkeys to yield SHIV-1157ip. Infant macaques were immunized with recombinant viral proteins, including multimeric HIV-C Env 1084i. To test whether cross-protection could be achieved, we mismatched HIV-C Env immunogens and challenge virus env. All vaccinated and control monkeys were exposed orally to low-dose SHIV-1157ip. Animals with no or only transient infection were rechallenged intrarectally with a high dose of R5 SHIV-1157ipd3N4, a "late", animal-evolved variant of SHIV-1157ip. Compared to controls, the vaccinees had significantly lower peak viral RNA loads, and one vaccinee remained completely virus-free, even in lymphoid tissues. Data from our novel heterologous mucosal challenge model and our protein-only immunogens imply that significant protection against heterologous viruses circulating in the local community may be achievable with a strategy that seeks to simultaneously induce cellular immunity as well as neutralizing antibody responses.

• Bimodal AIDS vaccine approach: Induction of cellular as well as humoral immunity can protect from systemic infection

  Authors: Robert A. Rasmussen, Samir K. Lakhashe, Ruth M. Ruprecht

  Vaccine.

  HIV clade C (HIV-C) strains comprise ∼56% of all HIV infections worldwide, and AIDS vaccines intended for global use must protect against this subtype. Our vaccine strategy has been to induceHIV clade C (HIV-C) strains comprise ∼56% of all HIV infections worldwide, and AIDS vaccines intended for global use must protect against this subtype. Our vaccine strategy has been to induce balanced antiviral immunity consisting of both neutralizing antibody and cell-mediated immune responses, an approach we tested in primates. As reported earlier, after isolating recently transmitted HIV-C strains from Zambian infants, we used env from one such virus, HIV1084i, to generate a multimeric gp160 immunogen. From another virus, isolated from a different child of the same mother–infant cohort, we cloned env to generate a recombinant simian–human immunodeficiency virus (SHIV), which was adapted to rhesus monkeys to yield SHIV-1157ip. Infant macaques were immunized with recombinant viral proteins, including multimeric HIV-C Env 1084i. To test whether cross-protection could be achieved, we mismatched HIV-C Env immunogens and challenge virus env. All vaccinated and control monkeys were exposed orally to low-dose SHIV-1157ip. Animals with no or only transient infection were rechallenged intrarectally with a high dose of R5 SHIV-1157ipd3N4, a “late”, animal-evolved variant of SHIV-1157ip. Compared to controls, the vaccinees had significantly lower peak viral RNA loads, and one vaccinee remained completely virus-free, even in lymphoid tissues. Data from our novel heterologous mucosal challenge model and our protein-only immunogens imply that significant protection against heterologous viruses circulating in the local community may be achievable with a strategy that seeks to simultaneously induce cellular immunity as well as neutralizing antibody responses.