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Objective: Gender differences in immune response and the rate of disease progression in HIV-infected individuals have been reported but the underlying mechanism remains unclear, in part because of the lack of relevant animal models. Here, we report a novel nonhuman primate model for investigation of sex disparity in HIV disease progression., Design/methods: Viral load and rate of disease progression were evaluated in rhesus macaques infected intrarectally with lineage-related subtype C R5 simian HIVs. Cytokine/chemokine levels in rectal swab eluates, and bacterial species adherent to the swabs and in the feces were determined., Results: Simian HIV-infected female rhesus macaques progressed faster to AIDS than male macaques, recapitulating the sex bias in HIV-1 disease in humans. There were no significant differences in the levels of soluble immune mediators in the rectal mucosa of naive female and male macaques. However, an exploratory longitudinal study in six infected macaques indicates that the female macaques mounted an earlier and more robust proinflammatory skewed rectal immune response to infection. Moreover, expansion of Proteobacteria that increase in other intestinal inflammatory disorders was significantly higher in the rectal mucosa of female than male macaques during acute infection., Conclusion: These findings suggest that sex differences in local innate immune activation and compositional shifts in the gut microbiota could be the drivers of increased disease susceptibility in female macaques. Further studies with this novel nonhuman primate model of HIV infection could lead to innovative research on gender differences, which may have important therapeutic implications for controlling disease in infected men as well as women.

Objective: Development of an effective vaccine or topical compound to prevent HIV transmission remains a major goal for control of the AIDS pandemic. Using a nonhuman primate model of heterosexual HIV-1 transmission, we tested whether a topical microbicide that reduces viral infectivity can potentiate the efficacy of a T-cell-based HIV vaccine., Design: A DNA prime and rAd5 virus boost vaccination strategy was employed, and a topical microbicide against the HIV nucleocapsid protein was used. To rigorously test the combination hypothesis, the vaccine constructs contained only two transgenes and the topical microbicide inhibitor was used at a suboptimal dose. Vaccinees were exposed in the absence and presence of the topical microbicide to repeated vaginal R5 simian human immunodeficiency virus (SHIV)(SF162P3) challenge at an escalating dose to more closely mimic high-risk exposure of women to HIV., Methods: Infection status was determined by PCR. Antiviral immune responses were evaluated by gp120 ELISA and intracellular cytokine staining., Results: A significant delay in SHIV acquisition (log-rank test; P = 0.0416) was seen only in vaccinated macaques that were repeatedly challenged in the presence of the topical microbicide. Peak acute viremia was lower (Mann-Whitney test; P = 0.0387) and viral burden was also reduced (Mann-Whitney test; P = 0.0252) in the combination-treated animals., Conclusion: The combined use of a topical microbicide to lower the initial viral seeding/spread and a T-cell-based vaccine to immunologically contain the early virological events of mucosal transmission holds promise as a preventive approach to control the spread of the AIDS epidemic.

Objectives: To assess the safety and distribution of a cellulose acetate 1,2-benzenedicarboxylate (CAP) gel formulation in rhesus macaques as part of the development process for its use as a vaginally administered product in humans., Design: The similarities between the reproductive physiology, anatomy and vaginal microflora of human and non-human primates makes non-human primates a relevant animal model to assess the safety and distribution of candidate anti-HIV microbicides., Methods: CAP gel was instilled once or once daily for 4 days into the vaginal vault of rhesus macaques. Colposcopy and magnetic resonance imaging were performed to detect adverse effects and spread of CAP, respectively. Additionally, vaginal pH and composition of the vaginal micorflora in macaques before, during and after CAP instillations were determined, and vaginal biopsies obtained following repeated CAP exposures were examined to further document its safety., Results: CAP is safe for repeated use and exhibits a favorable distribution profile, showing no evidence of penetration into cells that line the vaginal epithelium. Further, the presence of CAP has no adverse effect on vaginal pH or the composition of the vaginal microflora, and does not induce vaginal epithelial thinning or inflammation., Conclusions: CAP gel shows minimal toxicity in vivo, supporting its use as a candidate vaginal microbicide in humans.

Objectives: To evaluate the protective efficacy of cellulose acetate 1,2-benzenedicarboxylate (CAP) formulated in a glycerol-based gel against infection with CXCR4 (X4) and CCR5 (R5) viruses in the simian/human immunodeficiency virus (SHIV)/rhesus macaque model of HIV-1 transmission., Design: Mucosal infection of non-human primates is a reasonable model for use in the investigation of HIV-1 intervention strategies., Methods: Rhesus macaques treated with Depo-Provera 5 weeks prior to challenge were inoculated intravaginally twice, over a period of 6 h with mixed inocula of pathogenic X4- and R5-SHIV in the presence or absence of CAP. Plasma viral load, peripheral and mucosal CD4 T cell counts as well as the genotype of the circulating virus were determined., Results: CAP protected seven of ten macaques against transmission of both X4- and R5-SHIV, reaching statistically significant values (P = 0.0256). Delayed and/or reduced virus replication, as well as blunting of peripheral and mucosal CD4 T cell loss was noted in the three macaques that were infected in the CAP treated group compared to those in the placebo group. Further, protection conferred by CAP appeared to be more effective against X4- than R5-SHIV infection., Conclusions: CAP is protective against highly permissive challenges with X4 and R5 viruses in vivo. Research on further development of this promising compound as a candidate microbicide for the prevention of sexual HIV-1 transmission is therefore warranted.

Baboons were evaluated for their utility to serve as a model for testing envelope-based vaccines against human immunodeficiency virus type 1 (HIV-1). The ability of HIV-1 strains IIIB, RF, and SF2 to infect baboons was compared with that of simian/human immunodeficiency virus (SHIV) recombinant viruses comprised of either HXB2 or SF2 env, tat, rev, and vpu genes inserted into the SIVmac239 backbone. Both SHIV recombinants replicated in baboon PBMC in vitro, while no evidence of replication was noted for HIV-1 strains (MN, IIIB, SF2). Infection of baboons in vivo correlated with the restriction of infection in vitro. Virus was recovered by cocultivation methods early after SHIV (HXBc2) infection of two baboons with seroconversion profiles that parallel those observed in simian immunodeficiency virus (SIV)mac-infected rhesus monkeys. One of two baboons inoculated with SHIV(SF2) also seroconverted within 4 weeks; however, the kinetics of infection in a second animal appeared much later, with seroconversion to gp120 not evident until 20 weeks and no virus recovery during 32 weeks following infection. Viral DNA was detected in the lymph nodes of the SHIV-inoculated animals by nested polymerase chain reaction (PCR) amplification. Histopathologic changes were evident in lymph nodes, yet no overt clinical disease was observed. When HIV-1 strains (IIIB, RF, and SF2) were inoculated into baboons, virus was not recovered and no seroconversion to the major HIV-1 antigens was observed. However, viral DNA from the lymph nodes of four animals inoculated with HIV-1 strains could be detected by nested PCR, indicating a persistent but diminutive infection of HIV-1. The baboon thus represents a new animal model for testing HIV-1 envelope-based vaccines including the evaluation of new immunogens, dosages, routes, and adjuvants that act in eliciting protective responses.

Objective: To determine whether the HIV-1 genomes that grow out in vitro from peripheral blood mononuclear cells (PBMC) better represent the in vivo quasi-species present in plasma or PBMC., Results: For one patient (9606), PBMC culture represented more accurately the plasma rather than the in vivo PBMC quasi-species distribution, because a large number of tat-defective proviruses present in PBMC in vivo were not detected in plasma nor in the PBMC cultures. For a second patient (9605), PBMC culture was representative of both in vivo PBMC and plasma tat sequences, but selection of C2-V3 env sequences was observed in PBMC cultures compared with sequences present in both plasma and PBMC in vivo. This selection consisted of the absence in vitro of genomes with certain amino-acid substitutions at or near conserved glycosylation sites of the C2 region at positions 276 and 289. Site 276 has been reported to be important for viral infectivity, and these substitutions may therefore have affected infectivity. In the third patient (10095), selection of both tat and C2-V3 sequences was observed in culture as compared to plasma and PBMC in vivo. In contrast to the first two patients, this third patient contained V3 sequences in vivo that were predicted to impart syncytium induction and enhanced replication capacity. It was these sequences that grew out preferentially in vitro., Conclusion: This study suggests that short-term PBMC culture is representative of HIV-1 genomes present in PBMC and plasma in vivo to the degree that they are infectious.

HIV research in the past year has elucidated many questions relevant to strategies for treatment and control. For instance, there is a greater understanding of the diversity of HIV isolates as well as the wide range of potential cells sensitive to infection. The search for a safe, effective vaccine now calls for more caution in the light of the discovery of neutralization-resistant variants and antibody-mediated enhancement of infection. Efforts to control HIV must take into account the various mechanisms of virus entry into host cells, and the processes involved in cytopathic effects. Moreover, the role of cells of the mononuclear phagocyte system as reservoirs for HIV particles should be recognized. Together with new information about cytokine induction of HIV, the concept of latent infection of monocytes and macrophages has profound implications for virus persistence and dissemination, especially in the seronegative individual. While many factors about HIV have been uncovered in the past year, several questions remain unanswered and new ones have arisen. For instance, in how many ways does the virus kill in host cell? What causes latency and why does it occur in some but not all hosts? How can virus-filled macrophage vesicles be reached by therapeutic agents or prevented from releasing HIV? What surveillance mechanisms allow some productively infected hosts (cells as well as individuals) to survive beyond expectation? These and other questions should provoke future research on this presently complex and challenging pathogen.