T cell chemo-vaccination effects after repeated mucosal SHIV exposures and oral pre-exposure prophylaxis

Pre-exposure prophylaxis differentially alters circulating and mucosal immune cell activation in herpes simplex virus type 2 seropositive women

OBJECTIVE

Oral tenofovir-based pre-exposure prophylaxis (PrEP) is an important tool for prevention of new HIV infections, which also reduces subclinical herpes simplex virus type 2 (HSV-2) shedding and symptomatic lesions in HIV-negative, HSV-2-seropositive individuals. However, the impact of PrEP on mucosal immunity has not been examined in detail.

DESIGN

Here we evaluate paired genital tissue and systemic immune profiles to characterize the immunological effects of PrEP in HIV-negative, HSV-2-seropositive African women sexually exposed to HIV.

METHODS

We compared local and systemic innate and T-cell characteristics in samples collected during PrEP usage and 2 months after PrEP discontinuation.

RESULTS

We found that frequencies of cervical CCR5CD4 cells, regulatory T cells, and tissue macrophages were significantly reduced during PrEP use compared with after PrEP discontinuation. In contrast, peripheral blood CD4 and CD8 T cells expressing markers of activation and trafficking were increased during PrEP usage.

CONCLUSION

Together, our data are consistent with PrEP altering immunity differentially in the female genital tract compared with circulation in HSV-2+ women. Further study including comparison with HSV-2 negative women is needed to define the overall impact and mechanisms underlying these effects. These results point to the critical need to study the human mucosal compartment to characterize immune responses to mucosal infections.

Acquisition of wild-type HIV-1 infection in a patient on pre-exposure prophylaxis with high intracellular concentrations of tenofovir diphosphate: a case report

BACKGROUND

Pre-exposure prophylaxis (PrEP) with emtricitabine and tenofovir disoproxil fumarate is highly effective against acquisition of HIV infection, and only two cases of infection with a multidrug-resistant virus have been reported under adequate long-term adherence, as evidenced by tenofovir diphosphate concentrations in dried blood spots. We report a case of wild-type HIV-1 infection despite consistent use of emtricitabine and tenofovir disoproxil fumarate.

METHODS

The patient participated in the Amsterdam PrEP project, a demonstration project of daily and event-driven PrEP. We did extensive testing for HIV, including plasma HIV RNA and nested PCR on bulk peripheral blood mononuclear cells (PBMCs) and sigmoid biopsies after seroconversion.

FINDINGS

A 50-year-old man who has sex with men and had been on daily emtricitabine and tenofovir disoproxil fumarate for 8 months presented with fever, urinary tract infection caused by Escherichia coli, anal lymphogranuloma venereum infection, and a positive fourth-generation HIV test. We found an atypical seroconversion pattern, with initially only gp160 antibodies detected in the western blot. HIV RNA could not be detected in plasma, and nested PCR for HIV RNA and DNA on bulk PBMCs and sigmoid biopsies were negative. PrEP was discontinued; 3 weeks later HIV RNA was detected in plasma. No drug-resistant mutations were detected. Tenofovir diphosphate concentrations in dried blood spots were stable and high.

INTERPRETATION

To our knowledge, this is the first detailed case report suggesting wild-type HIV-1 infection despite good adherence, evidenced by repeatedly high concentrations of tenofovir diphosphate in dried blood spots. PrEP providers need to be aware that infection can occur despite good adherence. Regular HIV testing and awareness of atypical patterns of seroconversion is highly recommended.

FUNDING

ZonMw, National Institute for Public Health and the Environment, Internal GGD research funds, Aidsfonds, Stichting AmsterdamDiner Foundation, Gilead Sciences, Janssen Pharmaceutica, M A C AIDS Fund, and ViiV Healthcare.

Humoral responses against HIV in male genital tract: role in sexual transmission and perspectives for preventive strategies

: Most new HIV infections occur via sexual routes. The induction of protective anti-HIV antibodies in genital mucosa is an important step toward reducing HIV transmission. Mucosal anti-HIV antibodies may play a dual role by either protecting against HIV transmission or facilitating it. Protective properties against HIV of mucosal IgGs and IgAs exhibiting neutralizing or antibody-dependent cell-mediated cytotoxicity activities have been described in highly exposed seronegative individuals. Conversely, some IgGs may facilitate the crossing of HIV free-particles through epithelial barriers by transcytosis. Hence knowledge of the mechanisms underlying anti-HIV antibody production in the genital tract and their exact role in sexual transmission may help to develop appropriate preventive strategies based on passive immunization or mucosal vaccination approaches. Our review focuses on the characteristics of the humoral immune responses against HIV in the male genital tract and related prevention strategies.

Mucosal Vaccination with Heterologous Viral Vectored Vaccine Targeting Subdominant SIV Accessory Antigens Strongly Inhibits Early Viral Replication

Conventional HIV T cell vaccine strategies have not been successful in containing acute peak viremia, nor in providing long-term control. We immunized rhesus macaques intramuscularly and rectally using a heterologous adenovirus vectored SIV vaccine regimen encoding normally weakly immunogenic tat, vif, rev and vpr antigens fused to the MHC class II associated invariant chain. Immunizations induced broad T cell responses in all vaccinees. Following up to 10 repeated low-dose intrarectal challenges, vaccinees suppressed early viral replication (P = 0.01) and prevented the peak viremia in 5/6 animals. Despite consistently undetectable viremia in 2 out of 6 vaccinees, all animals showed evidence of infection induced immune responses indicating that infection had taken place. Vaccinees, with and without detectable viremia better preserved their rectal CD4 + T cell population and had reduced immune hyperactivation as measured by naïve T cell depletion, Ki-67 and PD-1 expression on T cells. These results indicate that vaccination towards SIV accessory antigens vaccine can provide a level of acute control of SIV replication with a suggestion of beneficial immunological consequences in infected animals of unknown long-term significance.

In conclusion, our studies demonstrate that a vaccine encoding subdominant antigens not normally associated with virus control can exert a significant impact on acute peak viremia.

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Mucosal heterologousvirus-vectored vaccine used with MHC class II associated invariant chain linked SIV accessory antigens

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Mucosal vaccination targeting subdominant antigens delay SIV mac251 replication in rhesus macaques.

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Longterm reduction of immune hyperactivation following SIV infection of vaccinated macaques.

Mucosal immunization is used with heterologous viral vectors and a genetic adjuvant to raise responses against poorly immunogenic SIV antigens. Following repeated low-dose challenge we observed delayed establishment of chronic phase viremia and reduced immune hyperactivation 6 months after established infection. Vaccination was found to strongly reduce viremia at early, but not late time points, after detected infection and in 2 out of 6 animals infection could only observed as virus induced T cell responses. Subdominant antigen vaccines may thus be used to delay SIV mac251 infection and can enable control of chronic viremia in a minority of cases.

HIV-1-Neutralizing IgA Detected in Genital Secretions of Highly HIV-1-Exposed Seronegative Women on Oral Preexposure Prophylaxis

Although nonhuman primate studies have shown that simian immunodeficiency virus/simian-human immunodeficiency virus (SIV/SHIV) exposure during preexposure prophylaxis (PrEP) with oral tenofovir can induce SIV immunity without productive infection, this has not been documented in humans. We evaluated cervicovaginal IgA in Partners PrEP Study participants using a subtype C primary isolate and found that women on PrEP had IgA with higher average human immunodeficiency virus type 1 (HIV-1)-neutralizing magnitude than women on placebo (33% versus 7%; P = 0.008). Using a cutoff of ≥90% HIV-1 neutralization, 19% of women on-PrEP had HIV-1-neutralizing IgA compared to 0% of women on placebo (P = 0.09). We also estimated HIV-1 exposure and found that the proportion of women with HIV-1-neutralizing IgA was associated with the level of HIV-1 exposure (P = 0.04). Taken together, our data suggest that PrEP and high levels of exposure to HIV may each enhance mucosal HIV-1-specific humoral immune responses in sexually exposed but HIV-1-uninfected individuals.

IMPORTANCE

Although there is not yet an effective HIV-1 vaccine, PrEP for at-risk HIV-1-uninfected individuals is a highly efficacious intervention to prevent HIV-1 acquisition and is currently being recommended by the CDC and WHO for all individuals at high risk of HIV-1 acquisition. We previously demonstrated that PrEP use does not enhance peripheral blood HIV-1-specific T-cell responses in HIV-exposed individuals. Here, we evaluate for cervicovaginal HIV-neutralizing IgA responses in genital mucosal secretions of HIV-exposed women, which is likely a more relevant site than peripheral blood for observation of potentially protective immune events occurring in response to sexual HIV-1 exposure for various periods. Furthermore, we assess for host response in the context of longitudinal quantification of HIV-1 exposure. We report that HIV-neutralizing IgA is significantly correlated with higher HIV-1 exposure and, furthermore, that there are more women with HIV-1-neutralizing IgA in the on-PrEP group than in the placebo group.

Superior Efficacy of a Human Immunodeficiency Virus Vaccine Combined with Antiretroviral Prevention in Simian-Human Immunodeficiency Virus-Challenged Nonhuman Primates

Although vaccines and antiretroviral (ARV) prevention have demonstrated partial success against human immunodeficiency virus (HIV) infection in clinical trials, their combined introduction could provide more potent protection. Furthermore, combination approaches could ameliorate the potential increased risk of infection following vaccination in the absence of protective immunity. We used a nonhuman primate model to determine potential interactions of combining a partially effective ARV microbicide with an envelope-based vaccine. The vaccine alone provided no protection from infection following 12 consecutive low-dose intravaginal challenges with simian-HIV strain SF162P3, with more animals infected compared to naive controls. The microbicide alone provided a 68% reduction in the risk of infection relative to that of the vaccine group and a 45% reduction relative to that of naive controls. The vaccine-microbicide combination provided an 88% reduction in the per-exposure risk of infection relative to the vaccine alone and a 79% reduction relative to that of the controls. Protected animals in the vaccine-microbicide group were challenged a further 12 times in the absence of microbicide and demonstrated a 98% reduction in the risk of infection. A total risk reduction of 91% was observed in this group over 24 exposures (P = 0.004). These important findings suggest that combined implementation of new biomedical prevention strategies may provide significant gains in HIV prevention.

IMPORTANCE There is a pressing need to maximize the impact of new biomedical prevention tools in the face of the 2 million HIV infections that occur each year. Combined implementation of complementary biomedical approaches could create additive or synergistic effects that drive improved reduction of HIV incidence. Therefore, we assessed a combination of an untested vaccine with an ARV-based microbicide in a nonhuman primate vaginal challenge model. The vaccine alone provided no protection (and may have increased susceptibility to a simian-HIV vaginal challenge), while the microbicide reduced the infection risk compared to that of vaccinated and naive animals. Importantly, the combined interventions provided the greatest level of protection, which was sustained following withdrawal of the microbicide. The data suggest that provision of ARV prophylaxis during vaccination reduces the potential for unexpected increased risks of infection following immunization and augments vaccine efficacy. These findings are important for the potential adoption of ARV prophylaxis as the baseline intervention for future HIV/AIDS vaccines.

Distinct genital tract HIV-specific antibody profiles associated with tenofovir gel

The impact of topical antiretrovirals for pre-exposure prophylaxis on humoral responses following HIV infection is unknown. Using a binding antibody multiplex assay, we investigated HIV-specific IgG and IgA responses to envelope glycoproteins, p24 Gag and p66, in the genital tract (GT) and plasma following HIV acquisition in women assigned to tenofovir gel (n=24) and placebo gel (n=24) in the CAPRISA 004 microbicide trial to assess if this topical antiretroviral had an impact on mucosal and systemic antibody responses. Linear mixed effect modeling and partial least squares discriminant analysis was used to identify multivariate antibody signatures associated with tenofovir use. There were significantly higher response rates to gp120 Env (P=0.03), p24 (P=0.002), and p66 (P=0.009) in plasma and GT in women assigned to tenofovir than placebo gel at multiple time points post infection. Notably, p66 IgA titers in the GT and plasma were significantly higher in the tenofovir compared with the placebo arm (P<0.05). Plasma titers for 9 of the 10 HIV-IgG specificities predicted GT levels. Taken together, these data suggest that humoral immune responses are increased in blood and GT of individuals who acquire HIV infection in the presence of tenofovir gel.

Repeated Vaginal SHIV Challenges in Macaques Receiving Oral or Topical Preexposure Prophylaxis Induce Virus-Specific T-Cell Responses

BACKGROUND

Preexposure prophylaxis (PrEP) for HIV prevention is a novel biomedical prevention method. We have previously modeled PrEP during rectal SHIV exposures in macaques and identified that Simian/Human Immunodeficiency Virus chimera (SHIV)-specific T-cell responses were induced in the presence of antiretroviral drugs, an observation previously termed T-cell chemo-vaccination. This report expands those initial findings by examining a larger group of macaques that were given oral or topical PrEP during repeated vaginal virus exposure.

METHODS

Thirty-six female pigtail macaques received up to 20 repeat low-dose vaginal inoculations with wild-type (WT) SHIVSF162P3 (n = 24) or a clonal derivative with the tenofovir (TFV) K65R drug-resistant mutation (n = 12). PrEP consisted of oral Truvada (n = 6, WT), TFV vaginal gel (n = 6, K65R), or TFV intravaginal ring (n = 6, WT). The remaining animals were PrEP-inexperienced controls (n = 12, WT; n = 6, K65R). SHIV-specific T cells were identified and characterized using interferon γ Enzyme-Linked ImmunoSpot (ELISPOT) and multiparameter flow cytometry.

RESULTS

Of 9 animals that were on PrEP and remained uninfected during WT SHIV vaginal challenges, 8 (88.9%) developed virus-specific T-cell responses. T cells were in CD4 and CD8 compartments, reached up to 4900 interferon γ-producing cells per million peripheral blood mononuclear cells, and primarily pol directed. In contrast, the replication-impaired K65R virus did not induce detectable T-cell responses, likely reflecting the need for adequate replication.

CONCLUSIONS

Virus-specific T-cell responses occur frequently in oral or topical PrEP-protected pigtail macaques after vaginal exposure to WT SHIV virus. The contribution of such immune responses to protection from infection during and after PrEP warrants further investigation.

Antiretroviral Pre-Exposure Prophylaxis Does Not Enhance Immune Responses to HIV in Exposed but Uninfected Persons

BACKGROUND

Antiretroviral preexposure prophylaxis (PrEP), using daily oral combination tenofovir disoproxil fumarate plus emtricitabine, is an effective human immunodeficiency virus (HIV) prevention strategy for populations at high risk of HIV acquisition. Although the primary mode of action for the protective effect of PrEP is probably direct antiviral activity, nonhuman primate studies suggest that PrEP may also allow for development of HIV-specific immune responses, hypothesized to result from aborted HIV infections providing a source of immunologic priming. We sought to evaluate whether PrEP affects the development of HIV-specific immune response in humans.

METHODS AND RESULTS

Within a PrEP clinical trial among high-risk heterosexual African men and women, we detected HIV-specific CD4(+) and CD8(+) peripheral blood T-cell responses in 10%-20% of 247 subjects evaluated. The response rate and magnitude of T-cell responses did not vary significantly between those assigned PrEP versus placebo, and no significant difference between those assigned PrEP and placebo was observed in measures of innate immune function.

CONCLUSIONS

We found no evidence to support the hypothesis that PrEP alters either the frequency or magnitude of HIV-specific immune responses in HIV-1-exposed seronegative individuals. These results suggest that PrEP is unlikely to serve as an immunologic prime to aid protection by a putative HIV vaccine.

A polyvalent Clade B virus-like particle HIV vaccine combined with partially protective oral preexposure prophylaxis prevents simian-human immunodeficiency virus Infection in macaques and primes for virus-amplified immunity

Vaccination and preexposure prophylaxis (PrEP) with antiretrovirals have shown only partial protection from HIV-1 infection in human trials. Oral Truvada (emtricitabine/tenofovir disoproxil fumarate) is FDA approved as PrEP but partial adherence reduces efficacy. If combined as biomedical preventions (CBP), an HIV vaccine could protect when PrEP adherence is low and PrEP could prevent vaccine breakthroughs. The efficacy of combining oral PrEP with an HIV vaccine has not been evaluated in humans. We determined the efficacy of combining a DNA/virus-like particle (VLP) vaccine with partially effective intermittent PrEP in Indian rhesus macaques (RM). Eight RM received intramuscular inoculations of five DNA plasmids encoding four HIV-1 Clade B primary isolate Envs and SIVmac239 Gag (at weeks 0 and 4), followed by intramuscular and intranasal inoculations of homologous Gag VLPs and four Env VLPs (at weeks 12, 16, and 53). At week 61, we initiated weekly rectal exposures with heterologous SHIV162p3 (10 TCID50) along with oral Truvada (TDF, 22 mg/kg; FTC 20 mg/kg) dosing 2 h before and 22 h after each exposure. This PrEP regimen previously demonstrated 50% efficacy. Five controls (no vaccine, no PrEP) received weekly SHIV162p3. All controls were infected after a median of four exposures; the mean peak plasma viral load (VL) was 3.9×10(7) vRNA copies/ml. CBP protected seven of eight (87.5%) RM. The one infected CBP RM had a reduced peak VL of 8.8×10(5) copies/ml. SHIV exposures during PrEP amplified Gag and Env antibody titers in protected RM. These results suggest that combining oral PrEP with HIV vaccines could enhance protection against HIV-1 infection.

New clinical trial designs for HIV vaccine evaluation

PURPOSE OF REVIEW

With multiple HIV vaccine candidates suitable for efficacy evaluation in a rapidly changing HIV prevention landscape, innovative HIV vaccine trial design research is much needed to optimally utilize resources by building on lessons learned from past HIV vaccine efficacy trials.

RECENT FINDINGS

Several recent articles propose new vaccine efficacy trial design strategies tailored to the emerging needs in HIV vaccine evaluation. These include a focus on efficacy evaluation proximal to the vaccination series; more intensive interim monitoring for potential harm, nonefficacy and high efficacy of the vaccine; simultaneous evaluation of multiple vaccine regimens with a shared placebo group; designs that include pilot immunogenicity studies of putative immune correlates to expedite their evaluation; as well as designs tailored to evaluate vaccine efficacy in the context of partially effective nonvaccine prevention modalities.

SUMMARY

A more rapid evaluation of multiple vaccine candidates is possible. Weaker vaccines can be weeded out quickly. Pilot studies can be done during the trial to prepare for a timely immune correlates assessment. Evidence that emerges regarding the efficacy of nonvaccine prevention modalities will have important implications for future trial designs.

In pursuit of an HIV vaccine: designing efficacy trials in the context of partially effective nonvaccine prevention modalities

The HIV prevention landscape is evolving rapidly, and future efficacy trials of candidate vaccines, which remain the best long-term option for stemming the HIV epidemic, will be conducted in the context of partially effective nonvaccine prevention modalities. It is essential that these trials provide for valid and efficient evaluation of vaccine efficacy and immune correlates. The availability of partially effective prevention modalities presents opportunities to study their interactions with vaccines to maximally reduce HIV incidence. This article proposes an approach for conducting future vaccine efficacy trials in the context of background use of partially effective nonvaccine prevention modalities, and for conducting future vaccine efficacy trials that provide nonvaccine prevention modalities in one or more of the randomized study groups. Strategies are discussed for responding to emerging evidence on nonvaccine prevention modalities during ongoing vaccine trials. Next-generation HIV vaccine efficacy trials will almost certainly be more complex in their design and implementation but may become more relevant to at-risk populations and better suited to the ultimate goal of reducing HIV incidence at the population level.

Reduced inflammation and CD4 loss in acute SHIV infection during oral pre-exposure prophylaxis

BACKGROUND

The impact of pre-exposure prophylaxis (PrEP) with antiretrovirals on breakthrough HIV or SHIV infection is not fully documented. We addressed the hypothesis that SHIV(SF162P3) infection despite active PrEP results in altered early immune parameters, compared with untreated infection.

METHODS

Eleven rhesus macaques were infected during repeated, rectal, low-dose SHIV(SF162P3) exposures while receiving concurrent oral PrEP (Truvada [n = 2] or GS7340 [n = 4]) or as untreated controls (n = 5). We measured SHIV RNA, inflammatory cytokines, CD4 cells, and SHIV-specific and memory T cells until 20 weeks after peak viremia.

RESULTS

SHIV infection during PrEP resulted in 100-fold lower peak viremia and lower IL-15, IL-18, and IL-1Ra levels, compared with controls (P < .05; Wilcoxon rank-sum test). Unlike controls, PrEP-treated macaques showed no significant CD4 cell count reduction during acute infection and developed more SHIV-specific central memory T cells, relative to controls. After in vivo CD8 cell depletion, viral load increased to similar levels, indicating that CD8 cells were critical for viral control in both groups.

CONCLUSIONS

PrEP with antiretrovirals has beneficial effects on early SHIV infection even when infection is not prevented. Although long-term immune control could not be examined in this SHIV infection model, our results suggest that PrEP results in improved early disease parameters in breakthrough infections.

Advances in HIV microbicide development

There is an urgent need control the spread of the global HIV pandemic. A microbicide, or topical drug applied to the mucosal environment to block transmission, is a promising HIV prevention strategy. The development of a safe and efficacious microbicide requires a thorough understanding of the mucosal environment and its role in HIV transmission. Knowledge of the key events in viral infection identifies points at which the virus might be most effectively targeted by a microbicide. The cervicovaginal and rectal mucosa play an important role in the innate defense against HIV, and microbicides must not interfere with these functions. In this review, we discuss the current research on HIV microbicide development.