Pathogenicity of simian-human immunodeficiency virus SHIV-89.6P and SIVmac is attenuated in cynomolgus macaques and associated with early T-lymphocyte responses.

Because most studies of AIDS pathogenesis in nonhuman primates have been performed in Indian-origin rhesus macaques (Macaca mulatta), little is known about lentiviral pathogenicity and control of virus replication following infection of alternative macaque species. Here, we report the consequences of simian-human immunodeficiency virus SHIV-89.6P and SIVmac251 infection in cynomolgus (Macaca fascicularis) and rhesus macaques of Chinese origin.

Role of genes that modulate host immune responses in the immunogenicity and pathogenicity of vaccinia virus.

Poxvirus vaccine vectors, although capable of eliciting potent immune responses, pose serious health risks in immunosuppressed individuals. We therefore constructed five novel recombinant vaccinia virus vectors which contained overlapping deletions of coding regions for the B5R, B8R, B12R, B13R, B14R, B16R, B18R, and B19R immunomodulatory gene products and assessed them for both immunogenicity and pathogenicity. All five of these novel vectors elicited both cellular and humoral immunity to the inserted HIV-BH10 env comparable to that induced by the parental Wyeth strain vaccinia virus.

Replication-defective adenovirus serotype 5 vectors elicit durable cellular and humoral immune responses in nonhuman primates.

The magnitude and durability of immune responses induced by replication-defective adenovirus serotype 5 (ADV5) vector-based vaccines were evaluated in the simian-human immunodeficiency virus/rhesus monkey model. A single inoculation of recombinant ADV5 vector constructs induced cellular and humoral immunity, but the rapid generation of neutralizing anti-Ad5 antibodies limited the immunity induced by repeated vector administration. The magnitude and durability of the immune responses elicited by these vaccines were greater when they were delivered as boosting immunogens in plasmid DNA-primed monkeys than when they were used as single-modality immunogens.

Dysfunction of simian immunodeficiency virus/simian human immunodeficiency virus-induced IL-2 expression by central memory CD4+ T lymphocytes.

Production of IL-2 and IFN-gamma by CD4+ T lymphocytes is important for the maintenance of a functional immune system in infected individuals. In the present study, we assessed the cytokine production profiles of functionally distinct subsets of CD4+ T lymphocytes in rhesus monkeys infected with pathogenic or attenuated SIV/simian human immunodeficiency virus (SHIV) isolates, and these responses were compared with those in vaccinated monkeys that were protected from immunodeficiency following pathogenic SHIV challenge. We observed that preserved central memory CD4+ T lymphocyte production of SIV/SHIV-induced IL-2 was associated with disease protection following primate lentivirus infection.

Multiclade human immunodeficiency virus type 1 envelope immunogens elicit broad cellular and humoral immunity in rhesus monkeys.

The development of a human immunodeficiency virus type 1 (HIV-1) vaccine that elicits potent cellular and humoral immune responses recognizing divergent strains of HIV-1 will be critical for combating the global AIDS epidemic. The present studies were initiated to examine the magnitude and breadth of envelope (Env)-specific T-lymphocyte and antibody responses generated by vaccines containing either a single or multiple genetically distant HIV-1 Env immunogens. Rhesus monkeys were immunized with DNA prime-recombinant adenovirus boost vaccines encoding a Gag-Pol-Nef polyprotein in combination with either a single Env or a mixture of clade-A, clade-B, and clade-C Envs.

Neutralizing antibodies elicited by immunization of monkeys with DNA plasmids and recombinant adenoviral vectors expressing human immunodeficiency virus type 1 proteins.

Immunization with recombinant serotype 5 adenoviral (rAd5) vectors or a combination of DNA plasmid priming and rAd5 boosting is known to elicit potent immune responses. However, little data exist regarding these immunization strategies and the development of anti-human immunodeficiency virus type 1 (HIV-1) neutralizing antibodies. We used DNA plasmids and rAd5 vectors encoding the HIV-1 89.

Heterologous envelope immunogens contribute to AIDS vaccine protection in rhesus monkeys.

Because a strategy to elicit broadly neutralizing anti-human immunodeficiency virus type 1 (HIV-1) antibodies has not yet been found, the role of an Env immunogen in HIV-1 vaccine candidates remains undefined. We sought to determine whether an HIV-1 Env immunogen genetically disparate from the Env of the challenge virus can contribute to protective immunity. We vaccinated Indian-origin rhesus monkeys with Gag-Pol-Nef immunogens, alone or in combination with Env immunogens that were either matched or mismatched with the challenge virus.

Cellular immunity elicited by human immunodeficiency virus type 1/ simian immunodeficiency virus DNA vaccination does not augment the sterile protection afforded by passive infusion of neutralizing antibodies.

High levels of infused anti-human immunodeficiency virus type 1 (HIV-1) neutralizing monoclonal antibodies (MAbs) can completely protect macaque monkeys against mucosal chimeric simian-human immunodeficiency virus (SHIV) infection. Antibody levels below the protective threshold do not prevent infection but can substantially reduce plasma viremia. To assess if HIV-1/SIV-specific cellular immunity could combine with antibodies to produce sterile protection, we studied the effect of a suboptimal infusion of anti-HIV-1 neutralizing antibodies in macaques with active cellular immunity induced by interleukin-2 (IL-2)-adjuvanted DNA immunization.

Viral escape from dominant simian immunodeficiency virus epitope-specific cytotoxic T lymphocytes in DNA-vaccinated rhesus monkeys.

Virus-specific cytotoxic T lymphocytes (CTL) are critical for control of human immunodeficiency virus type 1 replication. However, viral escape from CTL recognition can undermine this immune control. Here we demonstrate the high frequency and pattern of viral escape from dominant epitope-specific CTL in SIV gag DNA-vaccinated rhesus monkeys following a heterologous simian immunodeficiency virus (SIV) challenge.

Prior vaccination increases the epitopic breadth of the cytotoxic T-lymphocyte response that evolves in rhesus monkeys following a simian-human immunodeficiency virus infection.

Although recent evidence has confirmed the importance of cytotoxic T-lymphocyte (CTL) responses in controlling human immunodeficiency virus type 1 and simian immunodeficiency virus replication, the relevance of the epitopic breadth of those CTL responses remains unexplored. In the present study, we sought to determine whether vaccination can expand CTL populations which recognize a repertoire of viral epitopes that is greater than is typically generated in the course of a viral infection. We demonstrate that potent secondary CTL responses to subdominant epitopes are rapidly generated following a pathogenic simian-human immunodeficiency virus challenge of rhesus monkeys vaccinated with plasmid DNA or recombinant modified vaccinia virus Ankara vaccines.

Eventual AIDS vaccine failure in a rhesus monkey by viral escape from cytotoxic T lymphocytes.

Potent virus-specific cytotoxic T lymphocyte (CTL) responses elicited by candidate AIDS vaccines have recently been shown to control viral replication and prevent clinical disease progression after pathogenic viral challenges in rhesus monkeys. Here we show that viral escape from CTL recognition can result in the eventual failure of this partial immune protection. Viral mutations that escape from CTL recognition have been previously described in humans infected with human immunodeficiency virus (HIV) and monkeys infected with simian immunodeficiency virus (SIV).