T Cell Chemo-Vaccination Effects after Repeated Mucosal SHIV Exposures and Oral Pre-Exposure Prophylaxis

Pre-exposure prophylaxis (PrEP) with anti-viral drugs is currently in clinical trials for the prevention of HIV infection. Induction of adaptive immune responses to virus exposures during anti-viral drug administration, i.e., a “chemo-vaccination” effect, could contribute to PrEP efficacy. To study possible chemo-vaccination, we monitored humoral and cellular immune responses in nine rhesus macaques undergoing up to 14 weekly, low-dose SHIVSF162P3 rectal exposures. Six macaques concurrently received PrEP with intermittent, oral Truvada; three were no-PrEP controls. PrEP protected 4 macaques from infection. Two of the four showed evidence of chemo-vaccination, because they developed anti-SHIV CD4+ and CD8+ T cells; SHIV-specific antibodies were not detected. Control macaques showed no anti-SHIV immune responses before infection. Chemo-vaccination-induced T cell responses were robust (up to 3,940 SFU/106 PBMCs), predominantly central memory cells, short-lived (≤22 weeks), and appeared intermittently and with changing specificities. The two chemo-vaccinated macaques were virus-challenged again after 28 weeks of rest, after T cell responses had waned. One macaque was not protected from infection. The other macaque concurrently received additional PrEP. It remained uninfected and T cell responses were boosted during the additional virus exposures. In summary, we document and characterize PrEP-induced T cell chemo-vaccination. Although not protective after subsiding in one macaque, chemo-vaccination-induced T cells warrant more comprehensive analysis during peak responses for their ability to prevent or to control infections after additional exposures. Our findings highlight the importance of monitoring these responses in clinical PrEP trials and suggest that a combination of vaccines and PrEP potentially might enhance efficacy

HIV Transmission in a State Prison System, 1988–2005

INTRODUCTION: HIV prevalence among state prison inmates in the United States is more than five times higher than among nonincarcerated persons, but HIV transmission within U.S. prisons is sparsely documented. We investigated 88 HIV seroconversions reported from 1988-2005 among male Georgia prison inmates. METHODS: We analyzed medical and administrative data to describe seroconverters' HIV testing histories and performed a case-crossover analysis of their risks before and after HIV diagnosis. We sequenced the gag, env, and pol genes of seroconverters' HIV strains to identify genetically-related HIV transmission clusters and antiretroviral resistance. We combined risk, genetic, and administrative data to describe prison HIV transmission networks. RESULTS: Forty-one (47%) seroconverters were diagnosed with HIV from July 2003-June 2005 when voluntary annual testing was offered. Seroconverters were less likely to report sex (OR [odds ratio] = 0.02, 95% CI [confidence interval]: 0-0.10) and tattooing (OR = 0.03, 95% CI: <0.01-0.20) in prison after their HIV diagnosis than before. Of 67 seroconverters' specimens tested, 33 (49%) fell into one of 10 genetically-related clusters; of these, 25 (76%) reported sex in prison before their HIV diagnosis. The HIV strains of 8 (61%) of 13 antiretroviral-naïve and 21 (40%) of 52 antiretroviral-treated seroconverters were antiretroviral-resistant. DISCUSSION: Half of all HIV seroconversions were identified when routine voluntary testing was offered, and seroconverters reduced their risks following their diagnosis. Most genetically-related seroconverters reported sex in prison, suggesting HIV transmission through sexual networks. Resistance testing before initiating antiretroviral therapy is important for newly-diagnosed inmates

Recombinant Viruses and Early Global HIV-1 Epidemic

Central Africa was the epicenter of the HIV type 1 (HIV-1) pandemic. Understanding the early epidemic in the Democratic Republic of the Congo, formerly Zaire, could provide insight into how HIV evolved and assist vaccine design and intervention efforts. Using enzyme immunosorbent assay, we tested 3,988 serum samples collected in Kinshasa in the mid-1980s and confirmed seroreactivity by Western blot. Polymerase chain reaction of gag p17, env C2V3C3, and/or gp41; DNA sequencing; and genetic analyses were performed. Gene regions representing all the HIV-1 group M clades and unclassifiable sequences were found. From two or three short gene regions, 37% of the strains represented recombinant viruses, multiple infections, or both, which suggests that if whole genome sequences were available, most of these strains would have mosaic genomes. We propose that the HIV epidemic was established in Central Africa by the early 1980s and that some recombinant viruses most likely seeded the early global epidemic

Epitope specificity of T cells induced by chemo-vaccination.

<p><b>A</b>: T cell specificities in PrEP-protected macaques 4284 and 35451 change rapidly during SHIV exposures and PrEP, while they remain more consistent in infected control macaque AG94, and in 4284 after infection. T cell specificities were determined by IFNγ-ELISPOT with 14 peptide pools represented by the indicated colors. The pie charts depict percentages of contributions to the T cell response. Arrows indicate time point of virus exposures, adjacent numbers indicate how many exposures were given. Seroconversion is recorded by “Y”; numbers indicates the study week of seroconversion. <b>B</b>: T cells induced by chemo-vaccination appear focused on epitopes derived from the <i>pol</i> region. IFNγ-ELISPOT responses to 14 peptide pools were combined for the indicated gene products; their contribution to the response (all 14 peptide pools) was calculated. All IFNγ-ELISPOT results from week 1–41 are depicted. N refers to number of macaques in the 4 specified groups. P-values were obtained by unpaired, two-sided student's t-tests comparing all results before infection (12 time-points from 3 chemo-vaccinated macaques, filled circles and open diamonds combined) to those after infection (56 time-points from 5 macaques in control or PrEP-infected groups, open circles and filled triangles combined).</p

Experimental Design.

<p>SHIV-specific T cells were measured during the indicated experimental procedures. Arrows indicate repeated viral exposures, horizontal lines depict intermittent, oral PrEP. PrEP consisted of human-equivalent doses of oral Truvada. Each virus exposure was flanked by a waning drug dose of 7 days prior, and one drug dose administered 2 hours after exposure, as a model for intermittent PrEP use in humans. Bolded rectangles highlight final outcomes of SHIV challenges. Numbers in lower right corners refer to macaque identifications (IDs).</p

Chemo-vaccination effect.

<p>SHIV-specific T cells are induced in two PrEP-protected macaques during PrEP and virus exposures. PrEP protected four macaques from infection during 14 SHIV exposures in weeks 1–14 (<b>A</b> and <b>B</b>), while two became infected despite PrEP (<b>C</b>); three macaques were controls (<b>D</b>). SHIV-specific T cells were determined by IFNγ-ELISPOT. The black bars represent the number of specific T cells as a sum of responses to 14 SHIV-derived peptide pools for antigenic simulation, measured in SFU (spot forming units, left axis). Grey lines depict plasma viremia (right axes). The graphs represent data from individual macaques, their identification codes are bolded. The dotted lines are cut-off values for positive T cell responses. Two PrEP-protected macaques (35451 (<b>A</b>), 4284 (<b>B</b>)) showed signs of chemo-vaccination. During re-challenge with 14 SHIV exposures in weeks 42–55, additional PrEP protected macaques 35451 and 33756 (<b>A</b>). Chemo-vaccinated macaques 4284 and 33246 were not protected from SHIV infection (<b>B</b>). Throughout the study, anti-SHIV antibodies were determined every 6 weeks (weeks 1–41) or 4 weeks (weeks 42–69). “Y” indicates time of seroconversion.</p

Cytokine production of CD4⁺ and CD8⁺ T cells induced by chemo-vaccination.

<p>Intracellular production of IFNγ, IL-2, MIP-1β, or TNFα was measured by flow cytometry after in-vitro incubation of freeze-thawed cells with the two dominant peptide pools as determined by previous IFNγ-ELISPOT. We gated on CD3⁺ and CD69⁺ (<b>A, B</b>), or on CD3⁺, CD69⁺, and CD4⁺ or CD8⁺ (<b>C</b>), and determined the number of cells with intracellular production of any of the factors, regardless of whether they simultaneously produced the remaining 3 factors. “Any” refers to cells producing any of the indicated factors, not necessarily all simultaneously. Samples from infected controls or infected PrEP-treated macaques were from peak viremia or 6 weeks thereafter, whenever available. Such samples are not shown for CD4/CD8 analysis, because CD4⁺ cells significantly decline depending on the stage of SHIV infection. (<b>B</b>) Representative example of results obtained with cells from macaque 34912 before its infection, without stimulation (“no stim.”), with the two dominant peptide pools, or with SEB for polyclonal stimulation.</p