Intravenous inoculation of replication-deficient recombinant vaccinia virus DIs expressing simian immunodeficiency virus gag controls highly pathogenic simian-human immunodeficiency virus in monkeys

Vaccination of rhesus macaques with recombinant Mycobacterium bovis bacillus Calmette-Guérin Env V3 elicits neutralizing antibody-mediated protection against simian-human immunodeficiency virus with a homologous but not a heterologous V3 motif

Although the correlates of vaccine-induced protection against human immunodeficiency virus type 1 (HIV-1) are not fully known, it is presumed that neutralizing antibodies (NAb) play a role in controlling virus infection. In this study, we examined immune responses elicited in rhesus macaques following vaccination with recombinant Mycobacterium bovis bacillus Calmette-Guérin expressing an HIV-1 Env V3 antigen (rBCG Env V3). We also determined the effect of vaccination on protection against challenge with either a simian-human immunodeficiency virus (SHIV-MN) or a highly pathogenic SHIV strain (SHIV-89.6PD). Immunization with rBCG Env V3 elicited significant levels of NAb for the 24 weeks tested that were predominantly HIV-1 type specific. Sera from the immunized macaques neutralized primary HIV-1 isolates in vitro, including HIV-1BZ167/X4, HIV-1SF2/X4, HIV-1CI2/X4, and, to a lesser extent, HIV-1MNp/X4, all of which contain a V3 sequence homologous to that of rBCG Env V3. In contrast, neutralization was not observed against HIV-1SF33/X4, which has a heterologous V3 sequence, nor was it found against primary HIV-1 R5 isolates from either clade A or B. Furthermore, the viral load in the vaccinated macaques was significantly reduced following low-dose challenge with SHIV-MN, and early plasma viremia was markedly decreased after high-dose SHIV-MN challenge. In contrast, replication of pathogenic SHIV-89.6PD was not affected by vaccination in any of the macaques. Thus, we have shown that immunization with an rBCG Env V3 vaccine elicits a strong, type-specific V3 NAb response in rhesus macaques. While this response was not sufficient to provide protection against a pathogenic SHIV challenge, it was able to significantly reduce the viral load in macaques following challenge with a nonpathogenic SHIV. These observations suggest that rBCG vectors have the potential to deliver an appropriate virus immunogen for desirable immune elicitations.

A novel adjuvant for mucosal immunity to HIV-1 gp120 in nonhuman primates

The development of a safe and effective mucosal adjuvant is a crucial step toward a mucosal HIV/AIDS vaccine. This study seeks to determine the promise of a nontoxic mutant of cholera toxin (mCT; E112K) as a mucosal adjuvant in nonhuman primates. HIV-1 gp120 was nasally administered together with mCT E112K or native CT (nCT) as adjuvant on five to six occasions over a 6- to 8-wk period to groups of four rhesus macaques and alone to two monkeys that acted as controls. Macaques given nasal gp120 with either mCT E112K or nCT showed elevated gp120-specific IgG and IgA Ab responses with virus-neutralizing activity in both their plasma and mucosal external secretions, as well as higher numbers of gp120-specific IgA Ab-forming cells in their mucosal and peripheral lymphoid tissues and of IL-4-producing Th2-type CD4-positive (CD4(+)) T cells than did controls. Even though significant mucosal adjuvanticity was seen with both mCT E112K and nCT, neuronal damage was observed only in the nCT-treated, but not in the control or mCT E112K-treated groups. These results clearly show that mCT E112K is an effective and safe mucosal adjuvant for the development of a nasal HIV/AIDS vaccine.

A consecutive priming-boosting vaccination of mice with simian immunodeficiency virus (SIV) gag/pol DNA and recombinant vaccinia virus strain DIs elicits effective anti-SIV immunity

To evaluate immunity induced by a novel DNA prime-boost regimen, we constructed a DNA plasmid encoding the gag and pol genes from simian immunodeficiency virus (SIV) (SIVgag/pol DNA), in addition to a replication-deficient vaccinia virus strain DIs recombinant expressing SIV gag and pol genes (rDIsSIVgag/pol). In mice, priming with SIVgag/pol DNA, followed by rDIsSIVgag/pol induced an SIV-specific lymphoproliferative response that was mediated by a CD4+-T-lymphocyte subset. Immunization with either vaccine alone was insufficient to induce high levels of proliferation or Th1 responses in the animals. The prime-boost regimen also induced SIV Gag-specific cellular responses based on gamma interferon secretion, as well as cytotoxic-T-lymphocyte responses. Thus, the regimen of DNA priming and recombinant DIs boosting induced Th1-type cell-mediated immunity, which was associated with resistance to viral challenge with wild-type vaccinia virus expressing SIVgag/pol, suggesting that this new regimen may hold promise as a safe and effective vaccine against human immunodeficiency virus type 1.