Tracking the killers: how should we measure CD8 T cells in HIV infection?

Interferon gamma, interleukin 6 and tissue necrosis factor alpha levels among asymptomatic HIV patients in Benin City, Nigeria

BACKGROUND

Morbidity and mortality associated with HIV infection is immune-mediated, and an understanding of HIV immunology will be beneficial in the management of HIV infectionOBJECTIVE: The objective of this research was to measure the levels of TNF-α, IL-6 and IFN-γ in asymptomatic HIV patients and non-HIV subjects, as well as their relationship with CD4 count.

METHOD

Blood samples were collected from 173 subjects, consisting of 125 asymptomatic HIV patients (44 HAART-naïve and 81 on HAART) and 48 non-HIV subjects. The IFN-, IL-6, and TNF- levels in the blood were determined using enzyme-linked immunosorbent assays, and the CD4 count of all participants was determined using flow cytometry.

RESULTS

Regardless of treatment status, the IFN-γ levels of non-HIV subjects were significantly higher than those of HIV patients (p< 0.001). The opposite was true for IL-6, as the levels of IL-6 in non-HIV subjects were significantly lower than those in HAART-naïve HIV patients (p< 0.001) and those on HAART (p< 0.01). TNF-α levels did not differ between HIV patients and their non-HIV counterparts. Generally, the levels of these cytokines was not affected (p> 0.05) by immunosuppression (measured by CD4 count < 200 cells/μL) and there was no significant correlation between CD4 count and these cytokines (p> 0.05).

CONCLUSION

In conclusion, asymptomatic HIV infection decreased IFN-γ, increased IL-6, and had no effect on TNF-α levels, regardless of treatment status. Immunosuppression had no impact on these cytokine levels, and there was no relationship between them and CD4 counts.

Elevated Numbers of HIV-Specific Poly-Functional CD8+ T Cells With Stem Cell-Like and Follicular Homing Phenotypes in HIV-Exposed Seronegative Individuals

HIV-specific CD8⁺ T cells are known to play a key role in viral control during acute and chronic HIV infection. Although many studies have demonstrated the importance of HIV-specific CD8⁺ T cells in viral control, its correlation with protection against HIV infection remains incompletely understood. To better understand the nature of the immune response that contributes to the early control of HIV infection, we analyzed the phenotype, distribution and function of anti-viral CD8⁺ T cells in a cohort of HIV-exposed seronegative (HESN) women, and compared them with healthy controls and HIV-infected individuals. Further, we evaluated the in vitro viral inhibition activity of CD8⁺ T cells against diverse HIV-1 strains. We found that the HESN group had significantly higher levels of CD8⁺ T cells that express T-stem cell-like (TSCM) and follicular homing (CXCR5⁺) phenotype with more effector like characteristics as compared to healthy controls. Further, we observed that the HESN population had a higher frequency of HIV-specific poly-functional CD8⁺ T cells with robust in vitro virus inhibiting capacity against different clades of HIV. Overall, our results demonstrate that the HESN population has elevated levels of HIV-specific poly-functional CD8⁺ T cells with robust virus inhibiting ability and express elevated levels of markers pertaining to TSCM and follicular homing phenotype. These results demonstrate that future vaccine and therapeutic strategies should focus on eliciting these critical CD8⁺ T cell subsets.

Mechanisms of CD8+ T cell-mediated suppression of HIV/SIV replication

In this article, we summarize the role of CD8⁺ T cells during natural and antiretroviral therapy (ART)-treated HIV and SIV infections, discuss the mechanisms responsible for their suppressive activity, and review the rationale for CD8⁺ T cell-based HIV cure strategies. Evidence suggests that CD8⁺ T cells are involved in the control of virus replication during HIV and SIV infections. During early HIV infection, the cytolytic activity of CD8⁺ T cells is responsible for control of viremia. However, it has been proposed that CD8⁺ T cells also use non-cytolytic mechanisms to control SIV infection. More recently, CD8⁺ T cells were shown to be required to fully suppress virus production in ART-treated SIV-infected macaques, suggesting that CD8⁺ T cells are involved in the control of virus transcription in latently infected cells that persist under ART. A better understanding of the complex antiviral activities of CD8⁺ T cells during HIV/SIV infection will pave the way for immune interventions aimed at harnessing these functions to target the HIV reservoir.

Utilization of Feline ELISpot to Evaluate the Immunogenicity of a T Cell-Based FIV MAP Vaccine

The prototype and the commercial dual-subtype feline immunodeficiency virus (FIV) vaccines conferred protection against homologous FIV strains as well as heterologous FIV strains from the vaccine subtypes with closely related envelope (Env) sequences. Such protection was mediated by the FIV neutralizing antibodies (NAbs) induced by the vaccines. Remarkably, both prototype and commercial FIV vaccines also conferred protection against heterologous FIV subtypes with highly divergent Env sequences from the vaccine strains. Such protection was not mediated by the vaccine-induced NAbs but was mediated by a potent FIV-specific T-cell immunity generated by the vaccines (Aranyos et al., Vaccine 34: 1480-1488, 2016). The protective epitopes on the FIV vaccine antigen were identified using feline interleukin-2 (IL-2) and interferon-γ (IFNγ) ELISpot assays with overlapping FIV peptide stimulation of the peripheral blood mononuclear cells (PBMC) from cats immunized with prototype FIV vaccine. Two of the protective FIV peptide epitopes were identified on FIV p24 protein and another two protective peptide epitopes were found on FIV reverse transcriptase. In the current study, the multiple antigenic peptides (MAPs) of the four protective FIV peptides were combined with an adjuvant as the FIV MAP vaccine. The laboratory cats were immunized with the MAP vaccine to evaluate whether significant levels of vaccine-specific cytokine responses can be generated to the FIV MAPs and their peptides at post-second and post-third vaccinations. The PBMC from vaccinated cats and non-vaccinated control cats were tested for IL-2, IFNγ, and IL-10 ELISpot responses to the FIV MAPs and peptides. These results were compared to the results from CD4⁺ and CD8⁺ T-cell proliferation to the FIV MAPs and peptides. Current study demonstrates that IL-2 and IFNγ ELISpot responses can be used to detect memory responses of the T cells from vaccinated cats after the second and third vaccinations.

The Significance of Interferon-γ in HIV-1 Pathogenesis, Therapy, and Prophylaxis

Interferon-γ (IFNγ) plays various roles in the pathogenesis of HIV/AIDS. In an HIV-1 infected individual, the production of IFNγ is detected as early as the acute phase and continually detected throughout the course of infection. Initially produced to clear the primary infection, IFNγ together with other inflammatory cytokines are involved in establishing a chronic immune activation that exacerbates clinical diseases associated with AIDS. Unlike Type 1 IFNs, IFNγ has no direct antiviral activity against HIV-1 in primary cultures, as supported by the in vivo findings of IFNγ therapy in infected subjects. Results from both in vitro and ex vivo studies show that IFNγ can instead enhance HIV-1 replication and its associated diseases, and therapies aimed at decreasing its production are under consideration. On the other hand, IFNγ has been shown to enhance cytotoxic T lymphocytes and NK cell activities against HIV-1 infected cells. These activities are important in controlling HIV-1 replication in an individual and will most likely play a role in the prophylaxis of an effective vaccine against HIV-1. Additionally, IFNγ has been used in combination with HIV-1 vaccine to augment antiviral immunity. Technological advancements have focused on using IFNγ as a biological marker to analyze the type(s) of immunity generated by candidate HIV vaccines and the levels of immunity restored by anti-retroviral drug therapies or novel immunotherapies. Hence, in addition to its valuable ancillary role as a biological marker for the development of effective HIV-1 prophylactic and therapeutic strategies, IFNγ has a vital role in promoting the pathogenesis of HIV.

Measuring inhibition of HIV replication by ex vivo CD8⁺ T cells

HIV replication is unrestrained in vivo in the vast majority of infected subjects, and the ability of some rare individuals to control this virus is poorly understood. Standard immunogenicity assays for detecting HIV-1-specific CD8(+) T-cell responses, such as IFN-γ ELISpot and intracellular cytokine staining, generally fail to correlate with in vivo inhibition of HIV replication. Several viral inhibition assays, which measure the effectiveness of CD8(+) T-cell responses in suppressing HIV replication in vitro, have been described; but most depend on in vitro expansion of CD8(+) T cells, and some show inhibitory activity in HIV-negative individuals. We have optimized an assay to assess the suppressive capability of CD8(+) T cells directly ex vivo, eliminating the potential for altering their function through activation or expansion prior to assay setup, and thereby enhancing the assay's sensitivity by avoiding non-specific inhibition. With this method, the ability of ex vivo CD8(+) T cells to control HIV-1 replication in vitro can be quantified over several orders of magnitude. Specifically, our assay can be used to better define the antiviral function of CD8(+) T cells induced by vaccination, and can provide insight into their ability to control viral replication if HIV infection occurs post-vaccination.

Development of a luciferase based viral inhibition assay to evaluate vaccine induced CD8 T-cell responses

Emergence of SIV and HIV specific CD8 T cells has been shown to correlate with control of in vivo replication. Poor correlation between IFN-γ ELISPOT responses and in vivo control of the virus has triggered the development of more relevant assays to assess functional HIV-1 specific CD8 T-cell responses for the evaluation and prioritization of new HIV-1 vaccine candidates. We previously established a viral inhibition assay (VIA) that measures the ability of vaccine-induced CD8 T-cell responses to inhibit viral replication in autologous CD4 T cells. In this assay, viral replication is determined by measuring p24 in the culture supernatant. Here we describe the development of a novel VIA, referred to as IMC LucR VIA that exploits replication-competent HIV-1 infectious molecular clones (IMCs) in which the complete proviral genome is strain-specific and which express the Renilla luciferase (LucR) gene to determine viral growth and inhibition. The introduction of the luciferase readout does provide significant improvement of the read out time. In addition to switching to the LucR read out, changes made to the overall protocol resulted in the miniaturization of the assay from a 48 to a 96-well plate format, which preserved sample and allowed for the introduction of replicates. The overall assay time was reduced from 13 to 8 days. The assay has a high degree of specificity, and the previously observed non-specific background inhibition in cells from HIV-1 negative volunteers has been reduced dramatically. Importantly, we observed an increase in positive responses, indicating an improvement in sensitivity compared to the original VIA. Currently, only a limited number of "whole-genome" IMC-LucR viruses are available and our efforts will focus on expanding the panel to better evaluate anti-viral breadth. Overall, we believe the IMC LucR VIA provides a platform to assess functional CD8 T-cell responses in large-scale clinical trial testing, which will enhance the ability to select the most promising HIV-1 vaccine candidates capable of controlling HIV-1 replication in vivo.

Immune and viral correlates of "secondary viral control" after treatment interruption in chronically HIV-1 infected patients

Upon interruption of antiretroviral therapy, HIV-infected patients usually show viral load rebound to pre-treatment levels. Four patients, hereafter referred to as secondary controllers (SC), were identified who initiated therapy during chronic infection and, after stopping treatment, could control virus replication at undetectable levels for more than six months. In the present study we set out to unravel possible viral and immune parameters or mechanisms of this phenomenon by comparing secondary controllers with elite controllers and non-controllers, including patients under HAART. As candidate correlates of protection, virus growth kinetics, levels of intracellular viral markers, several aspects of HIV-specific CD4+ and CD8+ T cell function and HIV neutralizing antibodies were investigated. As expected all intracellular viral markers were lower in aviremic as compared to viremic subjects, but in addition both elite and secondary controllers had lower levels of viral unspliced RNA in PBMC as compared to patients on HAART. Ex vivo cultivation of the virus from CD4+ T cells of SC consistently failed in one patient and showed delayed kinetics in the three others. Formal in vitro replication studies of these three viruses showed low to absent growth in two cases and a virus with normal fitness in the third case. T cell responses toward HIV peptides, evaluated in IFN-γ ELISPOT, revealed no significant differences in breadth, magnitude or avidity between SC and all other patient groups. Neither was there a difference in polyfunctionality of CD4+ or CD8+ T cells, as evaluated with intracellular cytokine staining. However, secondary and elite controllers showed higher proliferative responses to Gag and Pol peptides. SC also showed the highest level of autologous neutralizing antibodies. These data suggest that higher T cell proliferative responses and lower replication kinetics might be instrumental in secondary viral control in the absence of treatment.

HIV/AIDS: 30 years of progress and future challenges

Acquired immune deficiency syndrome (AIDS) was first described 30 years ago in a report from the US Centers for Disease Control. Two years later the causative virus was identified and afterwards named the human immunodeficiency virus (HIV). This article reviews the progress made in the three decades since the recognition of AIDS and the discovery of HIV, with respect to the virus, the infected cell, and the host, as well as directions for future studies.

mRNA-based dendritic cell vaccination induces potent antiviral T-cell responses in HIV-1-infected patients

BACKGROUND

In an effort to raise protective antiviral immunity, dendritic cell immunotherapy was evaluated in six adults infected with human immunodeficiency virus (HIV)-1 and stable under highly active antiretroviral therapy (HAART).

DESIGN AND METHODS

Autologous monocyte-derived dendritic cells electroporated with mRNA encoding Gag and a chimeric Tat-Rev-Nef protein were administered, whereas patients remained on HAART. Feasibility, safety, immunogenicity and antiviral responses were investigated.

RESULTS

Dendritic cell vaccine preparation and administration were successful in all patients and only mild adverse events were seen. There was a significant increase post-dendritic cell as compared to pre-dendritic cell vaccination in magnitude and breadth of HIV-1-specific interferon (IFN)-γ response, in particular to Gag, and in T-cell proliferation. Breadth of IFN-γ response and T-cell proliferation were both correlated with CD4(+) and CD8(+) polyfunctional T-cell responses. Importantly, dendritic cell vaccination induced or increased the capacity of autologous CD8(+) T cells to inhibit superinfection of CD4(+) T cells with the vaccine-related IIIB virus and some but not all other HIV-1 strains tested. This HIV-1-inhibitory activity, indicative of improved antiviral response, was correlated with magnitude and breadth of Gag-specific IFN-γ response.

CONCLUSIONS

Therapeutic immunization with dendritic cells was safe and successful in raising antiviral cellular immune responses, including effector CD8(+) T cells with virus inhibitory activity. The stimulation of those potent immunological and antiviral effects, which have been associated with control of HIV-1, underscores the potential of dendritic cell vaccination in the treatment of HIV-1. The incomplete nature of the response in some patients helped to identify potential targets for future improvement, that is increasing antigenic spectrum and enhancing T-cell response.

Immune escape mutations detected within HIV-1 epitopes associated with viral control during treatment interruption

We analyzed immune responses in chronically HIV-infected individuals who took part in a treatment interruption (TI) trial designed for patients who initiated antiretroviral therapy within 6 months of seroconversion. In the 2 subjects who exhibited the best viral control, we detected CD8(+) T-cell responses against 1-2 Gag epitopes during the early weeks of TI and a subsequent increase in the number of epitopes recognized by the later time points. Each of these subjects developed mutations within the epitopes targeted by the highest magnitude responses. In the subject with the worst viral control, we detected responses against 2 Gag epitopes throughout the entire TI and no Gag mutations. The magnitude of these responses increased dramatically with time, greatly exceeding those detected in the virologic controllers. The highest levels of contemporaneous autologous neutralizing antibody activity were detected in the virologic controllers, and a subsequent escape mutation developed within the envelope gene of one controller that abrogated the response. These data suggest that immune escape mutations are a sign of viral control during TI, and that the absence of immune escape mutations in the presence of high levels of viral replication indicates the lack of an effective host immune response.

Fluorescent dye labeled influenza virus mainly infects innate immune cells and activated lymphocytes and can be used in cell-mediated immune response assay

Early results have recognized that influenza virus infects the innate and adaptive immune cells. The data presented in this paper demonstrated that influenza virus labeled with fluorescent dye not only retained the ability to infect and replicate in host cells, but also stimulated a similar human immune response as did unlabeled virus. Influenza virus largely infected the innate and activated adaptive immune cells. Influenza B type virus was different from that of A type virus. B type virus was able to infect the immature lymphocytes, but in lower amounts when compared to activated lymphocytes. Protection from influenza is tightly associated with cellular immunity. Traditional methods of cellular immunity assay had limitations to imitate the natural human cell-mediated responses to influenza virus. Labeled viruses could be used in the assay of virus-specific cytotoxicity, which might reflect the natural process more closely. Furthermore, human immune cells activated by one influenza subtype virus could kill the cells infected by other subtype virus. These results implied the human immune cells could directly handle and remove free virus using similar mechanism that was used to remove virus-infected nonimmune cells, which might help to simplify the design and production of influenza vaccine, thereby reduce the cost.

The spread, treatment, and prevention of HIV-1: evolution of a global pandemic

The most up-to-date estimates demonstrate very heterogeneous spread of HIV-1, and more than 30 million people are now living with HIV-1 infection, most of them in sub-Saharan Africa. The efficiency of transmission of HIV-1 depends primarily on the concentration of the virus in the infectious host. Although treatment with antiviral agents has proven a very effective way to improve the health and survival of infected individuals, as we discuss here, the epidemic will continue to grow unless greatly improved prevention strategies can be developed and implemented. No prophylactic vaccine is on the horizon. However, several behavioral and structural strategies have made a difference--male circumcision provides substantial protection from sexually transmitted diseases, including HIV-1, and the application of antiretroviral agents for prevention holds great promise.

Autologous CD4/CD8 co-culture assay: a physiologically-relevant composite measure of CD8+ T lymphocyte function in HIV-infected persons

During HIV-1 infection, the CD8(+) T lymphocyte response is critical to controlling the virus; indeed, the development of AIDS results, in large part, from the eventual failure of this response. The ability to measure the composite CD8(+) T lymphocyte anti-viral activity is, therefore, an essential requirement in the evaluation of immune based therapies and potential vaccines. We report here the details of a reproducible assay that measures the ability of CD8(+) T lymphocytes to suppress viral production by infected autologous CD4(+) T lymphocytes. The assay is not limited to persons with any specific HLA type, and the use of bi-specific antibodies for cell expansion makes the assay feasible in situations where cell numbers may be limiting. The measurement of viral production over time provides a global readout of the CD8(+) T lymphocyte overall function against HIV-1, which can be used for longitudinal assessment of individual HIV-infected persons in order to evaluate therapy, immune reconstitution, and new vaccines.

Cytokine gene expression profiles in human lymphocytes induced by a formula of traditional Chinese medicine, vigconic VI-28

VI-28 is a formula of traditional Chinese medicine (TCM) that has been used in aged individuals to improve health and, recently, to treat patients with chronic human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections. The mechanism underlying its clinical effect is, however, largely unknown. In the current study, we used a transwell culture system that mimics the in vivo situation and applied microarray technology to explore the effect of VI-28 on gene expression in human lymphocytes. The VI-28 treatment induced expression of a number of proinflammatory cytokines/chemokines in both peripheral blood mononuclear cells (PBMC) and spleen cells, including interleukin-1 (IL-1), growth-related protein-beta (GRO-beta) and epithelial cellderived neutrophil-activating peptide (ENA-78 [CXCL5]). Furthermore, a specific upregulation of interferon- gamma (IFN-gamma), monokine induced by gamma interferon (MIG [CXCL9]) and interleukin-2 receptor alpha (IL-2Ralpha) in spleen cells was noted, whereas tissue inhibitor of metalloproteinase-3 (TIMP-3) and disabled-2 (DAB2) were downregulated. VI-28 might, thus, enhance both innate and acquired immunity, in particular, T cell function. In addition, genes with no obvious immunologic function, such as insulin-like growth factor-2 (IGF- 1) and CD9, were also differentially affected. Further analysis of individual and combination of ingredients of VI-28 may shed light on the role of this herbal medicine in combating different diseases.

Evaluation of aldrithiol-2-inactivated preparations of HIV type 1 subtypes A, B, and D as reagents to monitor T cell responses

The development of HIV vaccines is an urgent priority and there is need to generate reagents representing multiple subtypes that can be used to screen HIV-1-specific responses. We used Aldrithiol-2 (AT-2), a mild oxidizing reagent, to eliminate the infectivity of HIV while maintaining its structure and ability to be processed for presentation to T cells. Inactivated subtype A, B, and D viruses were evaluated for their ability to stimulate T cell responses in PBMC samples from 18 U.S. subjects infected with HIV-1 subtype B and 32 Ugandan subjects infected with subtypes A and D or recombinants AC and AD. Five HIV-1-negative samples were also analyzed. T cell responses to AT-2-inactivated viral isolates were monitored by interferon-gamma (IFN-gamma) intracellular cytokine secretion (ICS) analysis; matched microvesicle preparations served as negative controls. Among the 18 subtype B infected subjects, 39% had CD3(+) CD4 (+) IFN-gamma responses and 67% had CD3(+) CD8(+) IFN-gamma responses. Of the 32 Ugandan subjects, 34% demonstrated CD3(+) CD4(+) IFN-gamma responses and 78% demonstrated CD3(+) CD8(+) IFN-gamma responses. Both subtype-specific and cross-reactive responses were observed. Responses to the AT-2 viruses tended to be lower in magnitude than those detected by a set of overlapping gag peptides. Robust lymphoproliferative responses to AT-2 viruses were seen in a subset of subjects. In conclusion, AT-2-inactivated HIV-1 virions stimulated both CD4 and CD8 HIV-1-specific responses and may provide an additional reagent for screening HIV-1-specific responses in HIV seropositives and vaccinees.

CD25+ regulatory T cells isolated from HIV-infected individuals suppress the cytolytic and nonlytic antiviral activity of HIV-specific CD8+ T cells in vitro

HIV infection is characterized by CD4(+) T cell depletion and progressive immune dysfunction; particularly impacted are HIV-specific T cell responses. An important component of immune-mediated control of HIV replication, killing of infected cells, appears to be impaired, in part due to poor cytolytic activity of HIV-specific cytotoxic T cells (CTL). In vitro, several functions of HIV-specific T cells, such as cytokine production, can be enhanced by the depletion of the immunosuppressive CD25(+) FoxP3(+) CD4(+) regulatory (Treg) cell subset. However, the effect of CD25(+) Treg cells on virus-specific cytolytic activity in the context of HIV or any human viral infection has not been investigated. The present study demonstrates that CD25(+) Treg cells isolated from the peripheral blood of HIV-infected subjects significantly suppress HIV Gag-specific cytolytic activity in vitro. In addition, CD25(+) Treg cells suppress effector function (coexpression of TNF-alpha and IFN-gamma) of HIV-specific CD8(+) T cells that proliferate in response to HIV antigen. Finally, the secretion of HIV-inhibitory CC-chemokines by HIV-specific and nonspecific CD8(+) T cells is significantly reduced in the presence of CD25(+) Treg cells. These data suggest that CD25(+) Treg-mediated suppression of the antiviral activity of HIV-specific CD8(+) T cells could impact the ability of HIV-infected individuals to control HIV replication in vivo.

Therapeutic vaccination against HIV: current progress and future possibilities

Although effective in reducing mortality, current antiretroviral therapy for HIV infection involves complex and expensive drug regimens that are toxic and difficult to take. Eradication of HIV reservoirs is not possible with existing therapies. The concept of therapeutic vaccination has been investigated to increase the potency and breadth of anti-HIV immune responses in order to delay or reduce antiretroviral therapy use. A variety of approaches targeted to both cell- and antibody-mediated immunity have been developed, including whole inactivated HIV-1, protein subunits and synthetic peptides, DNA vaccines and a number of viral vectors expressing HIV-1. These investigations have occurred in the absence of a clear understanding of disease pathogenesis or the correlates of protective immunity. At this time, there is no licensed therapeutic vaccine for any viral disease, including HIV; however, this review will consider recent progress in the field and summarize the challenges faced in the development of a therapeutic HIV vaccine.

HIV-specific CD8+ lymphocytes in semen are not associated with reduced HIV shedding

Sexual contact with HIV-infected semen is a major driving force behind the global HIV pandemic. Little is known regarding the immune correlates of virus shedding in this compartment, although HIV-1-specific CD8+ T cells are present in semen. We collected blood and semen from 27 chronically HIV-infected, therapy-naive men without common sexually transmitted infections or urethral inflammation and measured HIV-1 RNA viral load and cytokine/chemokine levels in both compartments. HIV-1 RNA levels were 10-fold higher in blood than semen, but discordantly high semen shedding was associated with higher semen levels of the proinflammatory cytokines IL-6, IL-8, IL-12, and IFN-gamma. Virus-specific CD8+ T cell epitopes were mapped in blood by IFN-gamma ELISPOT, using an overlapping HIV-1 clade B peptide matrix, and blood and semen CD8+ T cell responses were then assayed ex vivo using intracellular IFN-gamma staining. HIV-specific CD8+ responses were detected in 70% of semen samples, and their frequency was similar to or higher than blood. There was no correlation between the presence of virus-specific CD8+ T cells in semen and levels of HIV-1 RNA shedding. Among participants with detectable CD8+ IFN-gamma semen responses, their relative frequency was not associated with reduced HIV-1 RNA shedding, and their absolute number was correlated with higher levels of HIV-1 RNA semen shedding (r = 0.6; p = 0.03) and of several proinflammatory cytokines. Neither the presence nor the frequency of semen HIV-specific CD8+ T cell IFN-gamma responses in semen correlated with reduced levels of HIV RNA in semen.