HIV controllers exhibit potent CD8 T cell capacity to suppress HIV infection ex vivo and peculiar cytotoxic T lymphocyte activation phenotype

Spontaneous HIV Controllers Exhibit Preserved Immune Parameters in Peripheral Blood and Gastrointestinal Mucosa

BACKGROUND

HIV infection induces several gradual alterations on the peripheral and mucosal immune systems, with different magnitudes between infected individuals. In this regard, spontaneous HIV controllers exhibit either low or undetectable viral loads in the absence of treatment along with decreased immune alterations compared to HIV progressors. Yet, it is unknown how similar immune peripheral and mucosal parameters are when comparing HIV controllers to uninfected individuals.

METHODS

We evaluated a cohort of 11 HIV controllers who were compared to 20 seronegative donors. Peripheral blood (PB) and gut associated lymphoid tissue (GALT) samples were obtained to analyze the following: 1) the frequency and phenotype of immune cells by flow cytometry; 2) the expression of apoptotic molecules by immunohistochemistry; 3) the expression of transcriptional factors associated with T cell profiles by real time PCR; and 4) the serum level of microbial translocation by an enzymatic reaction.

RESULTS

We found that HIV controllers have a conserved frequency of most immune cell populations in PB and GALT, but a reduced percentage of CD4 T cells. The immune activation levels were similar in both groups of individuals, as well as the expression of cleaved caspase-3, transcriptional factors, and the level of microbial translocation. Interestingly, the frequency of CD8 T cells expressing HLA-DR but not CD38, previously associated with high effector functions, were preserved in HIV controllers.

CONCLUSIONS

Our results suggest that despite the infection, HIV controllers have preserved immune parameters, which can be associated with the spontaneous control of viral replication.

Progress Toward HIV Eradication: Case Reports, Current Efforts, and the Challenges Associated with Cure

An estimated 35 million people worldwide are infected with HIV, yet a widely applicable cure strategy remains elusive. Recent case reports have suggested that curing HIV infection is possible, renewing excitement about research efforts. We describe those cases and discuss their relevance to the global HIV epidemic. We also review ongoing cure strategies that are transitioning from the lab to the clinic, and the assays and clinical assessments that can be used to evaluate cure interventions.

Normal T-cell activation in elite controllers with preserved CD4+ T-cell counts

BACKGROUND

HIV elite controllers suppress HIV viremia without antiretroviral therapy (ART), yet previous studies demonstrated that elite controllers maintain an activated T-cell phenotype. Chronic immune activation has detrimental consequences and thus ART has been advocated for all elite controllers. However, elite controllers are not a clinically homogenous group. Since CD4% is among the best predictors of AIDS-related events, in the current study, we assessed whether this marker can be used to stratify elite controllers needing ART.

METHODS

Sixteen elite controllers were divided into two groups based on CD4% (EC > 40% and EC ≤40%), and T-cell subsets were analyzed for markers of memory/differentiation (CD45RA, CCR7, CD28), activation (CD38/HLA-DR), immunosenescence (CD57), costimulation (CD73, CD28) and exhaustion (PD-1, CD160, Tim-3). Monocyte subsets (CD14, CD16) were also analyzed and sCD14 levels were quantified using ELISA.

RESULTS

In the EC group, expression of activation, exhaustion, and immunosensescence markers on T cells were significantly reduced compared with the EC group and similar to the seronegative controls. The EC group expressed higher levels of costimulatory molecules CD28 and CD73 and had lower levels of monocyte activation (HLA-DR expression) with a reduced frequency of inflammatory monocyte (CD14 CD16) subset. Furthermore, the EC group maintained a stable CD4% during a median follow-up of 6 years.

CONCLUSION

Elite controllers with preserved CD4T cells (EC) have normal T-cell and monocyte phenotypes and therefore may have limited benefit from ART. CD4% can be an important marker for evaluating future studies aimed at determining the need for ART in this group of individuals.

Regulation of CD8+ T-cell cytotoxicity in HIV-1 infection

Understanding the mechanisms involved in cellular immune responses against control of human immunodeficiency virus (HIV) infection is key to development of effective immunotherapeutic strategies against viral proliferation. Clear insights into the regulation of cytotoxic CD8+ T cells is crucial to development of effective immunotherapeutic strategies due to their unique ability to eliminate virus-infected cells during the course of infection. Here, we reviewed the roles of transcription factors, co-inhibitory molecules and regulatory cytokines following HIV infection and their potential significance in regulating the cytotoxic potentials of CD8+ T cells.

Challenges and Opportunities for T-Cell-Mediated Strategies to Eliminate HIV Reservoirs

HIV's ability to establish latent reservoirs of reactivation-competent virus is the major barrier to cure. "Shock and kill" methods consisting of latency-reversing agents (LRAs) followed by elimination of reactivating cells through cytopathic effects are under active development. However, the clinical efficacy of LRAs remains to be established. Moreover, recent studies indicate that reservoirs may not be reduced efficiently by either viral cytopathic or CD8(+) T-cell-mediated mechanisms. In this perspective, we highlight challenges to T-cell-mediated elimination of HIV reservoirs, including characteristics of responding T cells, aspects of the cellular reservoirs, and properties of the latent virus itself. We also discuss potential strategies to overcome these challenges by targeting the antiviral activity of T cells toward appropriate viral antigens following latency.

Innate Immune Activity Correlates with CD4 T Cell-Associated HIV-1 DNA Decline during Latency-Reversing Treatment with Panobinostat

The pharmaceutical reactivation of dormant HIV-1 proviruses by histone deacetylase inhibitors (HDACi) represents a possible strategy to reduce the reservoir of HIV-1-infected cells in individuals treated with suppressive combination antiretroviral therapy (cART). However, the effects of such latency-reversing agents on the viral reservoir size are likely to be influenced by host immune responses. Here, we analyzed the immune factors associated with changes in proviral HIV-1 DNA levels during treatment with the potent HDACi panobinostat in a human clinical trial involving 15 cART-treated HIV-1-infected patients. We observed that the magnitude, breadth, and cytokine secretion profile of HIV-1-specific CD8 T cell responses were unrelated to changes in HIV-1 DNA levels in CD4 T cells during panobinostat treatment. In contrast, the proportions of CD3(-) CD56(+) total NK cells and CD16(+) CD56(dim) NK cells were inversely correlated with HIV-1 DNA levels throughout the study, and changes in HIV-1 DNA levels during panobinostat treatment were negatively associated with the corresponding changes in CD69(+) NK cells. Decreasing levels of HIV-1 DNA during latency-reversing treatment were also related to the proportions of plasmacytoid dendritic cells, to distinct expression patterns of interferon-stimulated genes, and to the expression of the IL28B CC genotype. Together, these data suggest that innate immune activity can critically modulate the effects of latency-reversing agents on the viral reservoir and may represent a target for future immunotherapeutic interventions in HIV-1 eradication studies.

IMPORTANCE

Currently available antiretroviral drugs are highly effective in suppressing HIV-1 replication, but the virus persists, despite treatment, in a latent form that does not actively express HIV-1 gene products. One approach to eliminate these cells, colloquially termed the "shock-and-kill" strategy, focuses on the use of latency-reversing agents that induce active viral gene expression in latently infected cells, followed by immune-mediated killing. Panobinostat, a histone deacetylase inhibitor, demonstrated potent activities in reversing HIV-1 latency in a recent pilot clinical trial and reduced HIV-1 DNA levels in a subset of patients. Interestingly, we found that innate immune factors, such as natural killer cells, plasmacytoid dendritic cells, and the expression patterns of interferon-stimulated genes, were most closely linked to a decline in the HIV-1 DNA level during treatment with panobinostat. These data suggest that innate immune activity may play an important role in reducing the residual reservoir of HIV-1-infected cells.

Tumor-infiltrating CD8(+) T lymphocytes associated with clinical outcome in anal squamous cell carcinoma

BACKGROUND

The prognostic significance of tumor-infiltrating CD8(+) T lymphocytes in anal squamous cell carcinoma (SCC) remains unclear. We designed the study to investigate the association between CD8(+) T cells and clinical prognosis among anal SCC patients.

METHODS

The density of CD8(+) T cells was assessed by immunohistochemistry. The numbers of CD8(+) T cells were counted and their relationship with clinicopathological factors and survival was explored.

RESULTS

A strong positive correlation was noted between intratumoral and peritumoral CD8(+) T cells (r = 0.77, P < 0.001). High intratumoral and peritumoral CD8(+) T cells was associated with well tumor differentiation, early-stage diagnosis, and better prognosis (P < 0.05). Better disease-free survival rates were demonstrated in patients with high CD8(+) T cell density in intratumoral nest (P = 0.01); peritumoral stroma (P = 0.004); and both in combination (P = 0.01). High peritumoral CD8(+) T cell was associated with overall survival (P = 0.025). In HIV-infected patients, high CD8(+) T cell density also had association with disease-free survival (P < 0.05).

CONCLUSIONS

High tumor-infiltrating CD8(+) T cell density showed the potential to indicate a favorable effect on prognosis and survival for anal SCC patients.

A Phase I Double Blind, Placebo-Controlled, Randomized Study of the Safety and Immunogenicity of Electroporated HIV DNA with or without Interleukin 12 in Prime-Boost Combinations with an Ad35 HIV Vaccine in Healthy HIV-Seronegative African Adults

BACKGROUND

Strategies to enhance the immunogenicity of DNA vaccines in humans include i) co-administration of molecular adjuvants, ii) intramuscular administration followed by in vivo electroporation (IM/EP) and/or iii) boosting with a different vaccine. Combining these strategies provided protection of macaques challenged with SIV; this clinical trial was designed to mimic the vaccine regimen in the SIV study.

METHODS

Seventy five healthy, HIV-seronegative adults were enrolled into a phase 1, randomized, double-blind, placebo-controlled trial. Multi-antigenic HIV (HIVMAG) plasmid DNA (pDNA) vaccine alone or co-administered with pDNA encoding human Interleukin 12 (IL-12) (GENEVAX IL-12) given by IM/EP using the TriGrid Delivery System was tested in different prime-boost regimens with recombinant Ad35 HIV vaccine given IM.

RESULTS

All local reactions but one were mild or moderate. Systemic reactions and unsolicited adverse events including laboratory abnormalities did not differ between vaccine and placebo recipients. No serious adverse events (SAEs) were reported. T cell and antibody response rates after HIVMAG (x3) prime-Ad35 (x1) boost were independent of IL-12, while the magnitude of interferon gamma (IFN-γ) ELISPOT responses was highest after HIVMAG (x3) without IL-12. The quality and phenotype of T cell responses shown by intracellular cytokine staining (ICS) were similar between groups. Inhibition of HIV replication by autologous T cells was demonstrated after HIVMAG (x3) prime and was boosted after Ad35. HIV specific antibodies were detected only after Ad35 boost, although there was a priming effect with 3 doses of HIVMAG with or without IL-12. No anti-IL-12 antibodies were detected.

CONCLUSION

The vaccines were safe, well tolerated and moderately immunogenic. Repeated administration IM/EP was well accepted. An adjuvant effect of co-administered plasmid IL-12 was not detected.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01496989.

Report of the 2014 Cent Gardes HIV Vaccine Conference-Part 2: Cell-mediated immunity, mucosal protection, and clinical trials: Fondation Mérieux Conference Center, Veyrier du Lac, France, 5-7 October, 2014

The 2014 Cent Gardes Conference took place on October 5-7, 2014, at the Fondation Mérieux Conference Center, on the shores of the Annecy Lake and aimed to review the progress and promise of HIV vaccines. The elicitation of broadly neutralizing antibodies (bNAbs), their use in passive immunization, as well as their genetic delivery (vector immunoprophylaxis) by a recombinant Adenovirus-associated virus (AAV) vector were reviewed in a preceding article [1]. Approaches to the elicitation of long-lasting T cell or mucosal immunity were also discussed and are now reviewed here. The possibility of eliciting mucosal IgAs was discussed, since it was demonstrated that transcytosis-blocking IgAs can protect monkeys against repeated vaginal challenge with a pathogenic chimeric simian and human immunodeficiency virus (SHIV). The possibility of purging the HIV reservoirs from HIV-infected persons and developing a cure of the disease was also discussed.

Success and failure of the cellular immune response against HIV-1

The cellular immune response to HIV-1 has now been studied in extraordinary detail. A very large body of data provides the most likely reasons that the HIV-specific cellular immune response succeeds in a small number of people but fails in most. Understanding the success and failure of the HIV-specific cellular immune response has implications that extend not only to immunotherapies and vaccines for HIV-1 but also to the cellular immune response in other disease states. This Review focuses on the mechanisms that are most likely responsible for durable and potent immunologic control of HIV-1. Although we now have a detailed picture of the cellular immune responses to HIV-1, important questions remain regarding the nature of these responses and how they arise.

During Stably Suppressive Antiretroviral Therapy Integrated HIV-1 DNA Load in Peripheral Blood is Associated with the Frequency of CD8 Cells Expressing HLA-DR/DP/DQ

Background

Characterising the correlates of HIV persistence improves understanding of disease pathogenesis and guides the design of curative strategies. This study investigated factors associated with integrated HIV-1 DNA load during consistently suppressive first-line antiretroviral therapy (ART).

Method

Total, integrated, and 2-long terminal repeats (LTR) circular HIV-1 DNA, residual plasma HIV-1 RNA, T-cell activation markers, and soluble CD14 (sCD14) were measured in peripheral blood of 50 patients that had received 1–14 years of efavirenz-based or nevirapine-based therapy.

Results

Integrated HIV-1 DNA load (per 10⁶ peripheral blood mononuclear cells) was median 1.9 log₁₀ copies (interquartile range 1.7–2.2) and showed a mean difference of 0.2 log₁₀ copies per 10 years of suppressive ART (95% confidence interval − 0.2, 0.6; p = 0.28). It was positively correlated with total HIV-1 DNA load and frequency of CD8⁺HLA-DR/DP/DQ⁺ cells, and was also higher in subjects with higher sCD14 levels, but showed no correlation with levels of 2-LTR circular HIV-1 DNA and residual plasma HIV-1 RNA, or the frequency of CD4⁺CD38⁺ and CD8⁺CD38⁺ cells. Adjusting for pre-ART viral load, duration of suppressive ART, CD4 cell counts, residual plasma HIV-1 RNA levels, and sCD14 levels, integrated HIV-1 DNA load was mean 0.5 log₁₀ copies higher for each 50% higher frequency of CD8⁺HLA-DR/DP/DQ⁺ cells (95% confidence interval 0.2, 0.9; p = 0.01).

Conclusions

The observed positive association between integrated HIV-1 DNA load and frequency of CD8⁺DR/DP/DQ⁺ cells indicates that a close correlation between HIV persistence and immune activation continues during consistently suppressive therapy. The inducers of the distinct activation profile warrant further investigation.

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Data from a homogenously treated population with consistent virological suppression

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Integrated HIV-1 DNA load did not vary significantly by duration of therapy

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Integrated HIV-1 DNA load was not associated with markers of recent virus replication

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Integrated HIV-1 DNA load and CD8+HLA-DR/DP/DQ+ frequency were positively associated

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Subjects with top quartile integrated HIV-1 DNA load showed high sCD14 levels

Integrated HIV-1 DNA load remains constant in the peripheral blood of individuals receiving long-term suppressive antiretroviral therapy (ART). However, the mechanisms preventing decay of the reservoir remain unclear. We studied a cross-sectional population, defined by the duration of suppressive ART. Integrated HIV-1 DNA load did not differ significantly according to the duration of suppressive ART, and showed no association with direct or indirect markers of ongoing virus replication. Rather, there was an independent, positive association between integrated HIV-1 DNA load and the frequency of CD8 cells expressing the activation marker HLA-DR/DP/DQ. These cells appear to have important regulatory and effector function. Our findings add to growing evidence that immune activation sustains the HIV-1 reservoir during long-term suppressive ART.

Reactivation Kinetics of HIV-1 and Susceptibility of Reactivated Latently Infected CD4+ T Cells to HIV-1-Specific CD8+ T Cells

The "shock and kill" model of human immunodeficiency virus type 1 (HIV-1) eradication involves the induction of transcription of HIV-1 genes in latently infected CD4(+) T cells, followed by the elimination of these infected CD4(+) T cells by CD8(+) T cells or other effector cells. CD8(+) T cells may also be needed to control the spread of new infection if residual infected cells are present at the time combination antiretroviral therapy (cART) is discontinued. In order to determine the time frame needed for CD8(+) T cells to effectively prevent the spread of HIV-1 infection, we examined the kinetics of HIV transcription and virus release in latently infected cells reactivated ex vivo. Isolated resting, primary CD4(+) T cells from HIV-positive (HIV+) subjects on suppressive regimens were found to upregulate cell-associated HIV-1 mRNA within 1 h of stimulation and produce extracellular virus as early as 6 h poststimulation. In spite of the rapid kinetics of virus production, we show that CD8(+) T cells from 2 out of 4 viremic controllers were capable of effectively eliminating reactivated autologous CD4(+) cells that upregulate cell-associated HIV-1 mRNA. The results have implications for devising strategies to prevent rebound viremia due to reactivation of rare latently infected cells that persist after potentially curative therapy.

IMPORTANCE

A prominent HIV-1 cure strategy termed "shock and kill" involves the induction of HIV-1 transcription in latently infected CD4(+) T cells with the goal of elimination of these cells by either the cytotoxic T lymphocyte response or other immune cell subsets. However, the cytotoxic T cell response may also be required after curative treatment if residual latently infected cells remain. The kinetics of HIV-1 reactivation indicate rapid upregulation of cell-associated HIV-1 mRNA and a 5-h window between transcription and virus release. Thus, HIV-specific CD8(+) T cell responses likely have a very short time frame to eliminate residual latently infected CD4(+) T cells that become reactivated after discontinuation of antiretroviral therapy following potentially curative treatment strategies.

Immunologic and Virologic Progression in HIV Controllers: The Role of Viral "Blips" and Immune Activation in the ANRS CO21 CODEX Study

Some HIV controllers (HICs) experience CD4+T cell count loss and/or lose their ability to control HIV. In this study, we investigated the rate of immunologic and/or virologic progression (ImmP/VirP) and its determinants in the ANRS CO21/CODEX cohort. Immunologic progression was defined as a lasting fall in CD4+T cell count below 350/mm(3) or more than 200/mm(3) with a baseline count below 600/mm(3). Virologic progression was defined as a HIV viral load (VL) above 2000 copies/mL on two consecutive determinations. Clinical characteristics, immune activation, ultrasensitive HIV VL and total HIV DNA were analyzed. Disease progression was observed in 15 of the 217 patients followed up between 2009 and 2013 (ImmP, n = 10; VirP, n = 5). Progressors had higher ultrasensitive HIV RNA levels at inclusion (i.e. 1-2 years before progression) than non-progressors. ImmP had also lower CD4+T cell nadir and CD4+T cell count at inclusion, and VirP had higher HIV DNA levels in blood. T cell activation and IP10 levels at inclusion were significantly higher in ImmP than in non-progressors. In summary, the lasting loss of CD4+T cells, residual HIV replication and basal levels of immune activation appear to be major determinants of progression in HICs. These factors should be considered for adjusting their follow-up.

A Plant-Derived Multi-HIV Antigen Induces Broad Immune Responses in Orally Immunized Mice

Multi-HIV, a multiepitopic protein derived from both gp120 and gp41 envelope proteins of the human immunodeficiency virus (HIV), has been proposed as a vaccine prototype capable of inducing broad immune responses, as it carries various B and T cell epitopes from several HIV strains. In this study, the immunogenic properties of a Multi-HIV expressed in tobacco chloroplasts are evaluated in test mice. BALB/c mice orally immunized with tobacco-derived Multi-HIV have elicited antibody responses, including both the V3 loop of gp120 and the ELDKWA epitope of gp41. Based on splenocyte proliferation assays, stimulation with epitopes of the C4, V3 domain of gp120, and the ELDKWA domain of gp41 elicits positive cellular responses. Furthermore, specific interferon gamma production is observed in both CD4+ and CD8+ T cells stimulated with HIV peptides. These results demonstrate that plant-derived Multi-HIV induces T helper-specific responses. Altogether, these findings illustrate the immunogenic potential of plant-derived Multi-HIV in an oral immunization scheme. The potential of this low-cost immunization approach and its implications on HIV/AIDS vaccine development are discussed.

Potent Cell-Intrinsic Immune Responses in Dendritic Cells Facilitate HIV-1-Specific T Cell Immunity in HIV-1 Elite Controllers

The majority of HIV-1 elite controllers (EC) restrict HIV-1 replication through highly functional HIV-1-specific T cell responses, but mechanisms supporting the evolution of effective HIV-1-specific T cell immunity in these patients remain undefined. Cytosolic immune recognition of HIV-1 in conventional dendritic cells (cDC) can facilitate priming and expansion of HIV-1-specific T cells; however, HIV-1 seems to be able to avoid intracellular immune recognition in cDCs in most infected individuals. Here, we show that exposure of cDCs from EC to HIV-1 leads to a rapid and sustained production of type I interferons and upregulation of several interferon-stimulated effector genes. Emergence of these cell-intrinsic immune responses was associated with a reduced induction of SAMHD1 and LEDGF/p75, and an accumulation of viral reverse transcripts, but inhibited by pharmacological blockade of viral reverse transcription or siRNA-mediated silencing of the cytosolic DNA sensor cGAS. Importantly, improved cell-intrinsic immune recognition of HIV-1 in cDCs from elite controllers translated into stronger abilities to stimulate and expand HIV-1-specific CD8 T cell responses. These data suggest an important role of cell-intrinsic type I interferon secretion in dendritic cells for the induction of effective HIV-1-specific CD8 T cells, and may be helpful for eliciting functional T cell immunity against HIV-1 for preventative or therapeutic clinical purposes.

Plasmacytoid dendritic cell and functional HIV Gag p55-specific T cells before treatment interruption can inform set-point plasma HIV viral load after treatment interruption in chronically suppressed HIV-1(+) patients

The identification of immune correlates of HIV control is important for the design of immunotherapies that could support cure or antiretroviral therapy (ART) intensification-related strategies. ART interruptions may facilitate this task through exposure of an ART partially reconstituted immune system to endogenous virus. We investigated the relationship between set-point plasma HIV viral load (VL) during an ART interruption and innate/adaptive parameters before or after interruption. Dendritic cell (DC), natural killer (NK) cell and HIV Gag p55-specific T-cell functional responses were measured in paired cryopreserved peripheral blood mononuclear cells obtained at the beginning (on ART) and at set-point of an open-ended interruption from 31 ART-suppressed chronically HIV-1(+) patients. Spearman correlation and linear regression modeling were used. Frequencies of plasmacytoid DC (pDC), and HIV Gag p55-specific CD3(+)  CD4(-)  perforin(+)  IFN-γ(+) cells at the beginning of interruption associated negatively with set-point plasma VL. Inclusion of both variables with interaction into a model resulted in the best fit (adjusted R(2)  = 0·6874). Frequencies of pDC or HIV Gag p55-specific CD3(+)  CD4(-)  CSFE(lo)  CD107a(+) cells at set-point associated negatively with set-point plasma VL. The dual contribution of pDC and anti-HIV T-cell responses to viral control, supported by our models, suggests that these variables may serve as immune correlates of viral control and could be integrated in cure or ART-intensification strategies.

A Phase I Double Blind, Placebo-Controlled, Randomized Study of the Safety and Immunogenicity of an Adjuvanted HIV-1 Gag-Pol-Nef Fusion Protein and Adenovirus 35 Gag-RT-Int-Nef Vaccine in Healthy HIV-Uninfected African Adults

Background

Sequential prime-boost or co-administration of HIV vaccine candidates based on an adjuvanted clade B p24, RT, Nef, p17 fusion protein (F4/AS01) plus a non-replicating adenovirus 35 expressing clade A Gag, RT, Int and Nef (Ad35-GRIN) may lead to a unique immune profile, inducing both strong T-cell and antibody responses.

Methods

In a phase 1, double-blind, placebo-controlled trial, 146 healthy adult volunteers were randomized to one of four regimens: heterologous prime-boost with two doses of F4/AS01_E or F4/AS01_B followed by Ad35-GRIN; Ad35-GRIN followed by two doses of F4/AS01_B; or three co-administrations of Ad35-GRIN and F4/AS01_B. T cell and antibody responses were measured.

Results

The vaccines were generally well-tolerated, and did not cause serious adverse events. The response rate, by IFN-γ ELISPOT, was greater when Ad35-GRIN was the priming vaccine and in the co-administration groups. F4/AS01 induced CD4+ T-cells expressing primarily CD40L and IL2 +/- TNF-α, while Ad35-GRIN induced predominantly CD8+ T-cells expressing IFN-γ +/- IL2 or TNF-α. Viral inhibition was induced after Ad35-GRIN vaccination, regardless of the regimen. Strong F4-specific antibody responses were induced. Immune responses persisted at least a year after the last vaccination. The complementary response profiles, characteristic of each vaccine, were both expressed after co-administration.

Conclusion

Co-administration of an adjuvanted protein and an adenovirus vector showed an acceptable safety and reactogenicity profile and resulted in strong, multifunctional and complementary HIV-specific immune responses.

Trial Registration

ClinicalTrials.gov NCT01264445

Personalized gene therapy locks out HIV, paving the way to control virus without antiretroviral drugs

INTRODUCTION

Advances in adoptive immunotherapy have enabled gene therapy approaches to be tested in clinical trials that involve the transfer of engineered immune cells to specifically target HIV-infected cells or block HIV infection or transmission. Genetic editing through engineered targeted nucleases provides a method for producing cells that are permanently resistant to HIV.

AREAS COVERED

Here, we discuss current and developing gene therapy approaches aimed to confer resistance to HIV infection at the cellular level by targeting viral or cellular elements, with a focus on gene editing strategies that target viral entry. Human gene therapy trials in HIV infection are reviewed.

EXPERT OPINION

In concept, a single infusion of genetically modified cells could potentially reduce the need for lifelong medication by providing long-term control over the virus (functional immunity). While the dream of completely eliminating viral reservoirs (sterilizing immunity) is appealing, this presents a significant additional hurdle and may not be necessary to improve long-term health. A single infusion, or a small number of infusions, of engineered cells may be shown in confirmatory clinical trials to produce a meaningful biologic effect. These techniques have implications for targeted gene therapy in HIV and other diseases.

HIV-1 Tat immunization restores immune homeostasis and attacks the HAART-resistant blood HIV DNA: results of a randomized phase II exploratory clinical trial

BACKGROUND

The phase II multicenter, randomized, open label, therapeutic trial (ISS T-002, Clinicaltrials.gov NCT00751595) was aimed at evaluating the immunogenicity and the safety of the biologically active HIV-1 Tat protein administered at 7.5 or 30 μg, given 3 or 5 times monthly, and at exploring immunological and virological disease biomarkers. The study duration was 48 weeks, however, vaccinees were followed until the last enrolled subject reached the 48 weeks. Reported are final data up to 144 weeks of follow-up. The ISS T-002 trial was conducted in 11 clinical centers in Italy on 168 HIV positive subjects under Highly Active Antiretroviral Therapy (HAART), anti-Tat Antibody (Ab) negative at baseline, with plasma viremia <50 copies/mL in the last 6 months prior to enrollment, and CD4(+) T-cell number ≥200 cells/μL. Subjects from a parallel observational study (ISS OBS T-002, Clinicaltrials.gov NCT0102455) enrolled at the same clinical sites with the same criteria constituted an external reference group to explore biomarkers of disease.

RESULTS

The vaccine was safe and well tolerated and induced anti-Tat Abs in most patients (79%), with the highest frequency and durability in the Tat 30 μg groups (89%) particularly when given 3 times (92%). Vaccination promoted a durable and significant restoration of T, B, natural killer (NK) cells, and CD4(+) and CD8(+) central memory subsets. Moreover, a significant reduction of blood proviral DNA was seen after week 72, particularly under PI-based regimens and with Tat 30 μg given 3 times (30 μg, 3x), reaching a predicted 70% decay after 3 years from vaccination with a half-life of 88 weeks. This decay was significantly associated with anti-Tat IgM and IgG Abs and neutralization of Tat-mediated entry of oligomeric Env in dendritic cells, which predicted HIV-1 DNA decay. Finally, the 30 μg, 3x group was the only one showing significant increases of NK cells and CD38(+)HLA-DR(+)/CD8(+) T cells, a phenotype associated with increased killing activity in elite controllers.

CONCLUSIONS

Anti-Tat immune responses are needed to restore immune homeostasis and effective anti-viral responses capable of attacking the virus reservoir. Thus, Tat immunization represents a promising pathogenesis-driven intervention to intensify HAART efficacy.

HIV controllers with different viral load cutoff levels have distinct virologic and immunologic profiles

BACKGROUND

The mechanisms behind natural control of HIV replication are still unclear, and several studies pointed that elite controllers (ECs) are a heterogeneous group.

METHODS

We performed analyses of virologic, genetic, and immunologic parameters of HIV-1 controllers groups: (1) ECs (viral load, <80 copies/mL); (2) ebbing elite controllers (EECs; transient viremia/blips); and viremic controllers (VCs; detectable viremia, <5000 copies/mL). Untreated noncontrollers (NCs), patients under suppressive highly active antiretroviral therapy (HAART), and HIV-1-negative individuals were analyzed as controls.

RESULTS

Total and integrated HIV-1 DNA for EC were significantly lower than for NC and HAART groups. 2-LTR circles were detected in EEC (3/5) and VC (6/7) but not in EC. Although EC and EEC maintain normal T-cell counts over time, some VC displayed negative CD4 T-cell slopes. VC and EEC showed a higher percentage of activated CD8 T cells and microbial translocation than HIV-1-negative controls. EC displayed a weaker Gag/Nef IFN-γ T-cell response and a significantly lower proportion of anti-HIV IgG antibodies than EEC, VC, and NC groups.

CONCLUSION

Transient/persistent low-level viremia in HIV controllers may have an impact on immunologic and virologic profiles. Classified HIV controller patients taking into account their virologic profile may decrease the heterogeneity of HIV controllers cohorts, which may help to clarify the mechanisms associated to the elite control of HIV.

Combined ART started during acute HIV infection protects central memory CD4+ T cells and can induce remission

BACKGROUND

Therapeutic control of HIV replication reduces the size of the viral reservoir, particularly among central memory CD4+ T cells, and this effect might be accentuated by early treatment.

METHODS

We examined the effect of ART initiated at the time of the primary HIV infection (early ART), lasting 2 and 6 years in 11 and 10 patients, respectively, on the HIV reservoir in peripheral resting CD4+ T cells, sorted into naive (TN), central memory (TCM), transitional memory (TTM) and effector memory (TEM) cells, by comparison with 11 post-treatment controllers (PTCs).

RESULTS

Between baseline and 2 years, CD4+ T cell subset numbers increased markedly (P < 0.004) and HIV DNA levels decreased in all subsets (P < 0.009). TTM cells represented the majority of reservoir cells at both timepoints, T cell activation status normalized and viral diversity remained stable over time. The HIV reservoir was smaller after 6 years of early ART than after 2 years (P < 0.019), and did not differ between PTCs and patients treated for 6 years. One patient, who had low reservoir levels in all T cell subsets after 2 years of treatment similar to the levels in PTCs, spontaneously controlled viral replication during 18 months off treatment.

CONCLUSIONS

Early prolonged ART thus limits the size of the HIV reservoir, protects long-lived cells from persistent infection and may enhance post-treatment control.

A Murine Viral Outgrowth Assay to Detect Residual HIV Type 1 in Patients With Undetectable Viral Loads

BACKGROUND

Sensitive assays are needed for detection of residual human immunodeficiency virus (HIV) in patients with undetectable plasma viral loads to determine whether eradication strategies are effective. The gold standard quantitative viral outgrowth assay (QVOA) underestimates the magnitude of the viral reservoir. We sought to determine whether xenograft of leukocytes from HIV type 1 (HIV)-infected patients with undetectable plasma viral loads into immunocompromised mice would result in viral amplification.

METHODS

Peripheral blood mononuclear cells or purified CD4(+) T cells from HIV or simian immunodeficiency virus (SIV)-infected subjects with undetectable plasma viral loads were adoptively transferred into NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice. The mice were monitored for viremia following depletion of human CD8(+) T cells to minimize antiviral activity. In some cases, humanized mice were also treated with activating anti-CD3 antibody.

RESULTS

With this murine viral outgrowth assay (MVOA), we successfully amplified replication-competent HIV or SIV from all subjects tested, including 5 HIV-positive patients receiving suppressive antiretroviral therapy (ART) and 6 elite controllers or suppressors who were maintaining undetectable viral loads without ART, including an elite suppressor from whom we were unable to recover virus by QVOA.

CONCLUSIONS

Our results suggest that the MVOA has the potential to serve as a powerful tool to identify residual HIV in patients with undetectable viral loads.

Elevated Expression of CD160 and 2B4 Defines a Cytolytic HIV-Specific CD8+ T-Cell Population in Elite Controllers

During chronic human immunodeficiency virus (HIV) infection, virus-specific CD8(+) T cells become functionally exhausted. Unlike most chronically infected individuals, elite controllers of HIV retain CD8(+) T-cell polyfunctionality and cytolytic capacity. It remains unclear whether elite controllers manifest T-cell exhaustion similar to subjects with chronic progression of HIV infection. Here we assessed coexpression of PD-1, Lag-3, CD160, and 2B4 as a measure of T-cell exhaustion in a cohort of elite controllers and in chronic progressors. We found that elite controllers have a high proportion of potentially exhausted (PD1(+)CD160(+)2B4(+)) HIV-specific CD8(+) T cells that is comparable to the proportion in chronic progressors. However, elite controllers also harbor a population of HIV-specific CD160(+)2B4(+) CD8(+) T cells that correlates with cytolytic capacity, as measured by perforin expression, a population not commonly present in chronic progressors. We therefore propose that coexpression of CD160 and 2B4 delineates a population of cytolytic CD8(+) T cells important for the control of HIV.

Post-treatment control of HIV infection

Antiretroviral therapy (ART) for HIV is not a cure. However, recent studies suggest that ART, initiated early during primary infection, may induce post-treatment control (PTC) of HIV infection with HIV RNA maintained at <50 copies per mL. We investigate the hypothesis that ART initiated early during primary infection permits PTC by limiting the size of the latent reservoir, which, if small enough at treatment termination, may allow the adaptive immune response to prevent viral rebound (VR) and control infection. We use a mathematical model of within host HIV dynamics to capture interactions among target cells, productively infected cells, latently infected cells, virus, and cytotoxic T lymphocytes (CTLs). Analysis of our model reveals a range in CTL response strengths where a patient may show either VR or PTC, depending on the size of the latent reservoir at treatment termination. Below this range, patients will always rebound, whereas above this range, patients are predicted to behave like elite controllers. Using data on latent reservoir sizes in patients treated during primary infection, we also predict population-level VR times for noncontrollers consistent with observations.

Clinical outcomes and antiretroviral therapy in 'elite' controllers: a review of the literature

Elite controllers naturally suppress HIV viraemia below the level of detection using standard methods, but demonstrate persistent inflammation and low-level viraemia that is detectable via ultrasensitive assays. These factors may contribute to an increased risk of non-AIDS-related morbidity and mortality among elite controllers. Data suggest that cardiovascular disease may be of particular concern in elite controllers, as evidenced by an increased burden of subclinical cardiovascular disease upon radiographic screening and an elevated rate of hospitalisations for cardiovascular disease as compared to non-controllers who are treated with antiretroviral therapy (ART). Widespread use of ART among non-controllers has led to significant declines in morbidity and mortality, but guidelines are generally silent on the role of ART in the care of elite controllers. Multiple small studies have demonstrated that laboratory markers of inflammation, immune activation and HIV burden improve after initiation of ART in elite controllers. Clinicians must consider these potential benefits of ART when deciding whether to initiate treatment in asymptomatic elite controllers.

Modest attenuation of HIV-1 Vpu alleles derived from elite controller plasma

In the absence of antiretroviral therapy, infection with human immunodeficiency virus type 1 (HIV-1) can typically not be controlled by the infected host and results in the development of acquired immunodeficiency. In rare cases, however, patients spontaneously control HIV-1 replication. Mechanisms by which such elite controllers (ECs) achieve control of HIV-1 replication include particularly efficient immune responses as well as reduced fitness of the specific virus strains. To address whether polymorphisms in the accessory HIV-1 protein Vpu are associated with EC status we functionally analyzed a panel of plasma-derived vpu alleles from 15 EC and 16 chronic progressor (CP) patients. Antagonism of the HIV particle release restriction by the intrinsic immunity factor CD317/tetherin was well conserved among EC and CP Vpu alleles, underscoring the selective advantage of this Vpu function in HIV-1 infected individuals. In contrast, interference with CD317/tetherin induced NF-κB activation was little conserved in both groups. EC Vpus more frequently displayed reduced ability to downregulate cell surface levels of CD4 and MHC class I (MHC-I) molecules as well as of the NK cell ligand NTB-A. Polymorphisms potentially associated with high affinity interactions of the inhibitory killer immunoglobulin-like receptor (KIR) KIR2DL2 were significantly enriched among EC Vpus but did not account for these functional differences. Together these results suggest that in a subgroup of EC patients, some Vpu functions are modestly reduced, possibly as a result of host selection.

Characterization of CD8+ T cell differentiation following SIVΔnef vaccination by transcription factor expression profiling

The onset of protective immunity against pathogenic SIV challenge in SIVΔnef-vaccinated macaques is delayed for 15-20 weeks, a process that is related to qualitative changes in CD8⁺ T cell responses induced by SIVΔnef. As a novel approach to characterize cell differentiation following vaccination, we used multi-target qPCR to measure transcription factor expression in naïve and memory subsets of CD8+⁺ T cells, and in SIV-specific CD8⁺ T cells obtained from SIVΔnef-vaccinated or wild type SIVmac239-infected macaques. Unsupervised clustering of expression profiles organized naïve and memory CD8⁺ T cells into groups concordant with cell surface phenotype. Transcription factor expression patterns in SIV-specific CD8⁺ T cells in SIVΔnef-vaccinated animals were distinct from those observed in purified CD8⁺ T cell subsets obtained from naïve animals, and were intermediate to expression profiles of purified central memory and effector memory T cells. Expression of transcription factors elicited by SIVΔnef vaccination also varied over time: cells obtained at later time points, temporally associated with greater protection, appeared more central-memory like than cells obtained at earlier time points, which appeared more effector memory-like. Expression of transcription factors associated with effector differentiation, such as ID2 and RUNX3, were decreased over time, while expression of transcription factors associated with quiescence or memory differentiation, such as TCF7, BCOR and EOMES, increased. CD8⁺ T cells specific for a more conserved epitope expressed higher levels of TBX21 and BATF, and appeared more effector-like than cells specific for an escaped epitope, consistent with continued activation by replicating vaccine virus. These data suggest transcription factor expression profiling is a novel method that can provide additional data complementary to the analysis of memory cell differentiation based on classical phenotypic markers. Additionally, these data support the hypothesis that ongoing stimulation by SIVΔnef promotes a distinct protective balance of CD8⁺ T cell differentiation and activation states.

The live attenuated vaccine SIVΔnef can induce robust CD8⁺ T cell- mediated protection against infection with pathogenic SIV in macaques. Thus, there is substantial interest in characterizing these immune responses to inform HIV vaccine design. Animals challenged at 15–20 weeks post vaccination exhibit robust protection, whereas animals challenged at 5 weeks post-vaccination manifest little protection. Since the frequency of SIV-specific T cells decreases from week 5 to week 20, it is likely that the quality of the response to challenge changes as virus-specific cells differentiate. We applied a novel approach of transcription factor expression profiling to characterize the differences in SIV-specific cell function and phenotype at more protected and less protected time points. Using unsupervised clustering methods informed by expression profiles assessed in purified CD8⁺ T cell subsets, we show that SIV-specific cells display expression profiles different than any purified CD8⁺ T cell subset, and intermediate to sorted effector memory and central memory subsets. SIV-specific cells overall appear more effector memory-like at week 5 post-vaccination, and more central memory-like at week 20 post-vaccination. Distinct profiles of CD8⁺ T cells specific for different SIV epitopes having different immune escape kinetics suggests maturation is regulated by ongoing low-level replication of vaccine virus.

Clinical outcome of HIV viraemic controllers and noncontrollers with normal CD4 counts is exclusively determined by antigen-specific CD8+ T-cell-mediated HIV suppression

In this cross-sectional study we evaluated T-cell responses using several assays to determine immune correlates of HIV control that distinguish untreated viraemic controllers (VC) from noncontrollers (NC) with similar CD4 counts. Samples were taken from 65 ART-naïve chronically HIV-infected VC and NC from Thailand with matching CD4 counts in the normal range (>450 cells/μl). We determined HIVp24-specific T-cell responses using standard Interferon-gamma (IFNγ) ELISpot assays, and compared the functional quality of HIVp24-specific CD8⁺ T-cell responses using polychromatic flow cytometry. Finally, in vitro HIV suppression assays were performed to evaluate directly the activity of CD8⁺ T cells in HIV control. Autologous CD4⁺ T cells were infected with primary patient-derived HIV isolates and the HIV suppressive activity of CD8⁺ T cells was determined after co-culture, measuring production of HIVp24 Ag by ELISA. The HIVp24-specific T-cell responses of VC and NC could not completely be differentiated through measurement of IFNγ-producing cells using ELISpot assays, nor by the absolute cell numbers of polyfunctional HIVp24-specific CD8⁺ T cells. However, in vitro HIV suppression assays showed clear differences between VC and NC. HIV suppressive activity, mediated by either ex vivo unstimulated CD8⁺ T cells or HIVp24-specific T-cell lines, was significantly greater using cells from VC than NC cells. Additionally, we were able to demonstrate a significant correlation between the level of HIV suppressive activity mediated by ex vivo unstimulated CD8⁺ T cells and plasma viral load (pVL) (Spearman r = -0.7345, p = 0.0003). This study provides evidence that in vitro HIV suppression assays are the most informative in the functional evaluation of CD8⁺ T-cell responses and can distinguish between VC and NC.

Clinical Control of HIV-1 by Cytotoxic T Cells Specific for Multiple Conserved Epitopes

Identification and characterization of CD8(+) T cells effectively controlling HIV-1 variants are necessary for the development of AIDS vaccines and for studies of AIDS pathogenesis, although such CD8(+) T cells have been only partially identified. In this study, we sought to identify CD8(+) T cells controlling HIV-1 variants in 401 Japanese individuals chronically infected with HIV-1 subtype B, in which protective alleles HLA-B*57 and HLA-B*27 are very rare, by using comprehensive and exhaustive methods. We identified 13 epitope-specific CD8(+) T cells controlling HIV-1 in Japanese individuals, though 9 of these epitopes were not previously reported. The breadths of the T cell responses to the 13 epitopes were inversely associated with plasma viral load (P = 2.2 × 10(-11)) and positively associated with CD4 count (P = 1.2 × 10(-11)), indicating strong synergistic effects of these T cells on HIV-1 control in vivo. Nine of these epitopes were conserved among HIV-1 subtype B-infected individuals, whereas three out of four nonconserved epitopes were cross-recognized by the specific T cells. These findings indicate that these 12 epitopes are strong candidates for antigens for an AIDS vaccine. The present study highlighted a strategy to identify CD8(+) T cells controlling HIV-1 and demonstrated effective control of HIV-1 by those specific for 12 conserved or cross-reactive epitopes.

IMPORTANCE

HLA-B*27-restricted and HLA-B*57-restricted cytotoxic T lymphocytes (CTLs) play a key role in controlling HIV-1 in Caucasians and Africans, whereas it is unclear which CTLs control HIV-1 in Asian countries, where HLA-B*57 and HLA-B*27 are very rare. A recent study showed that HLA-B*67:01 and HLA-B*52:01-C*12:02 haplotypes were protective alleles in Japanese individuals, but it is unknown whether CTLs restricted by these alleles control HIV-1. In this study, we identified 13 CTLs controlling HIV-1 in Japan by using comprehensive and exhaustive methods. They included 5 HLA-B*52:01-restricted and 3 HLA-B*67:01-restricted CTLs, suggesting that these CTLs play a predominant role in HIV-1 control. The 13 CTLs showed synergistic effects on HIV-1 control. Twelve out of these 13 epitopes were recognized as conserved or cross-recognized ones. These findings strongly suggest that these 12 epitopes are candidates for antigens for AIDS vaccines.

Increased Levels of Macrophage Inflammatory Proteins Result in Resistance to R5-Tropic HIV-1 in a Subset of Elite Controllers

Elite controllers (ECs) are a rare group of HIV seropositive individuals who are able to control viral replication without antiretroviral therapy. The mechanisms responsible for this phenotype, however, have not been fully elucidated. In this study, we examined CD4(+) T cell resistance to HIV in a cohort of elite controllers and explored transcriptional signatures associated with cellular resistance. We demonstrate that a subgroup of elite controllers possess CD4(+) T cells that are specifically resistant to R5-tropic HIV while remaining fully susceptible to X4-tropic and vesicular stomatitis virus G (VSV-G)-pseudotyped viruses. Transcriptome analysis revealed 17 genes that were differentially regulated in resistant elite controllers relative to healthy controls. Notably, the genes encoding macrophage inflammatory protein 1α (MIP-1α), CCL3 and CCL3L1, were found to be upregulated. The MIP-1α, MIP-1β, and RANTES chemokines are natural ligands of CCR5 and are known to interfere with HIV replication. For three elite controllers, we observed increased production of MIP-1α and/or MIP-1β at the protein level. The supernatant from resistant EC cells contained MIP-1α and MIP-1β and was sufficient to confer R5-tropic resistance to susceptible CD4(+) T cells. Additionally, this effect was reversed by using inhibitory anti-MIP antibodies. These results suggest that the T cells of these particular elite controllers may be naturally resistant to HIV infection by blocking R5-tropic viral entry.

IMPORTANCE

HIV is a pandemic health problem, and the majority of seropositive individuals will eventually progress to AIDS unless antiretroviral therapy (ART) is administered. However, rare patients, termed elite controllers, have a natural ability to control HIV infection in the absence of ART, but the mechanisms by which they achieve this phenotype have not been fully explored. This paper identifies one mechanism that may contribute to this natural resistance: some elite controllers have CD4(+) T cells that produce high levels of MIP chemokines, which block R5-tropic HIV entry. This mechanism could potentially be exploited to achieve a therapeutic effect in other HIV-seropositive individuals.

Identification of effective subdominant anti-HIV-1 CD8+ T cells within entire post-infection and post-vaccination immune responses

Defining the components of an HIV immunogen that could induce effective CD8+ T cell responses is critical to vaccine development. We addressed this question by investigating the viral targets of CD8+ T cells that potently inhibit HIV replication in vitro, as this is highly predictive of virus control in vivo. We observed broad and potent ex vivo CD8+ T cell-mediated viral inhibitory activity against a panel of HIV isolates among viremic controllers (VC, viral loads <5000 copies/ml), in contrast to unselected HIV-infected HIV Vaccine trials Network (HVTN) participants. Viral inhibition of clade-matched HIV isolates was strongly correlated with the frequency of CD8+ T cells targeting vulnerable regions within Gag, Pol, Nef and Vif that had been identified in an independent study of nearly 1000 chronically infected individuals. These vulnerable and so-called “beneficial” regions were of low entropy overall, yet several were not predicted by stringent conservation algorithms. Consistent with this, stronger inhibition of clade-matched than mismatched viruses was observed in the majority of subjects, indicating better targeting of clade-specific than conserved epitopes. The magnitude of CD8+ T cell responses to beneficial regions, together with viral entropy and HLA class I genotype, explained up to 59% of the variation in viral inhibitory activity, with magnitude of the T cell response making the strongest unique contribution. However, beneficial regions were infrequently targeted by CD8+ T cells elicited by vaccines encoding full-length HIV proteins, when the latter were administered to healthy volunteers and HIV-positive ART-treated subjects, suggesting that immunodominance hierarchies undermine effective anti-HIV CD8+ T cell responses. Taken together, our data support HIV immunogen design that is based on systematic selection of empirically defined vulnerable regions within the viral proteome, with exclusion of immunodominant decoy epitopes that are irrelevant for HIV control.

Attempts to develop an HIV vaccine that elicits potent cell-mediated immunity have so far been unsuccessful. This is due in part to the use of immunogens that appear to recapitulate responses induced naturally by HIV that are, at best, partially effective. We previously showed that the capacity of CD8+ T cells from patients to block HIV replication in culture is strongly correlated with HIV control in vivo, therefore, we investigated the virological determinants of potent CD8+ T cell inhibitory activity. We observed that CD8+ T cells from patients with naturally low plasma viral loads (viremic controllers) were better able to inhibit the replication of diverse HIV strains in vitro than CD8+ T cells from HIV-noncontroller patients. Importantly, we also found that the potency of the antiviral activity in the latter group was strongly correlated with recognition of selected regions across the viral proteome that are critical to viral fitness. Vaccines that encode full-length viral proteins rarely elicited responses to these vulnerable regions. Taken together, our results provide insight into the characteristics of effective cell-mediated immune responses against HIV and how these may inform the design of better immunogens.

Attenuation of immune activation in an open-label clinical trial for HIV-AIDS using a polyherbal formulation

To explain a stable clinical outcome observed in a previous pilot clinical trial using a polyherbal formulation (PHF) for HIV-AIDS, we, in the present study, evaluated the T cell functions from fresh and stored blood samples. In three clinical groups-the anti-retroviral therapy, PHF and control arms-we compared the circulating levels of lipopolysaccharide, LPS-binding protein, soluble CD14, aspartate transaminase (AST) and alanine transaminase (ALT). Additionally, we evaluated the expression of T cell markers and gag-specific immune responses. The PHF treatment significantly reduced the levels of sCD14, AST and ALT. In a cross-sectional analysis at 30 months post-treatment, in comparison to the control group, the PHF arm showed significantly low per-cell expression of PD1, CD95 and HLA-DR. The PHF treatment appears to have attenuated general immune activation and hepatic inflammation in the study participants. Targeting the mediators of immune activation must be pursued as a useful strategy for HIV-AIDS management.

Long-term control of simian immunodeficiency virus (SIV) in cynomolgus macaques not associated with efficient SIV-specific CD8+ T-cell responses

The spontaneous control of human and simian immunodeficiency viruses (HIV/SIV) is typically associated with specific major histocompatibility complex (MHC) class I alleles and efficient CD8(+) T-cell responses, but many controllers maintain viral control despite a nonprotective MHC background and weak CD8(+) T-cell responses. Therefore, the contribution of this response to maintaining long-term viral control remains unclear. To address this question, we transiently depleted CD8(+) T cells from five SIV-infected cynomolgus macaques with long-term viral control and weak CD8(+) T-cell responses. Among them, only one carried the protective MHC allele H6. After depletion, four of five controllers experienced a transient rebound of viremia. The return to undetectable viremia was accompanied by only modest expansion of SIV-specific CD8(+) T cells that lacked efficient SIV suppression capacity ex vivo. In contrast, the depletion was associated with homeostatic activation/expansion of CD4(+) T cells that correlated with viral rebound. In one macaque, viremia remained undetectable despite efficient CD8(+) cell depletion and inducible SIV replication from its CD4(+) T cells in vitro. Altogether, our results suggest that CD8(+) T cells are not unique contributors to the long-term maintenance of low viremia in this SIV controller model and that other mechanisms, such as weak viral reservoirs or control of activation, may be important players in control.

IMPORTANCE

Spontaneous control of HIV-1 to undetectable levels is associated with efficient anti-HIV CD8(+) T-cell responses. However, in some cases, this response fades over time, although viral control is maintained, and many HIV controllers (weak responders) have very low frequencies of HIV-specific CD8(+) T cells. In these cases, the importance of CD8 T cells in the maintenance of HIV-1 control is questionable. We developed a nonhuman primate model of durable SIV control with an immune profile resembling that of weak responders. Transient depletion of CD8(+) cells induced a rise in the viral load. However, viremia was correlated with CD4(+) T-cell activation subsequent to CD8(+) cell depletion. Regain of viral control to predepletion levels was not associated with restoration of the anti-SIV capacities of CD8(+) T cells. Our results suggest that CD8(+) T cells may not be involved in maintenance of viral control in weak responders and highlight the fact that additional mechanisms should not be underestimated.

CD8(+) T-cell Cytotoxic Capacity Associated with Human Immunodeficiency Virus-1 Control Can Be Mediated through Various Epitopes and Human Leukocyte Antigen Types

Understanding natural immunologic control over Human Immunodeficiency Virus (HIV)-1 replication, as occurs in rare long-term nonprogressors/elite controllers (LTNP/EC), should inform the design of efficacious HIV vaccines and immunotherapies. Durable control in LTNP/EC is likely mediated by highly functional virus-specific CD8(+) T-cells. Protective Human Leukocyte Antigen (HLA) class I alleles, like B*27 and B*57, are present in most, but not all LTNP/EC, providing an opportunity to investigate features shared by their HIV-specific immune responses. To better understand the contribution of epitope targeting and conservation to immune control, we compared the CD8(+) T-cell specificity and function of B*27/57(neg) LTNP/EC (n = 23), B*27/57(pos) LTNP/EC (n = 23) and B*27/57(neg) progressors (n = 13). Fine mapping revealed 11 previously unreported immunodominant responses. Although B*27/57(neg) LTNP/EC did not target more highly conserved epitopes, their CD8(+) T-cell cytotoxic capacity was significantly higher than progressors. Similar to B*27/57(pos) LTNP/EC, this superior cytotoxicity was mediated by preferential expansion of immunodominant responses and lysis through the predicted HLA. These findings suggest that increased CD8(+) T-cell cytotoxic capacity is a common mechanism of control in most LTNP/EC regardless of HLA type. They also suggest that potent cytotoxicity can be mediated through various epitopes and HLA molecules and could, in theory, be induced in most people.

Therapeutic HIV Peptide Vaccine

Therapeutic vaccines aim to control chronic HIV infection and eliminate the need for lifelong antiretroviral therapy (ART). Therapeutic HIV vaccine is being pursued as part of a functional cure for HIV/AIDS. We have outlined a basic protocol for inducing new T cell immunity during chronic HIV-1 infection directed to subdominant conserved HIV-1 epitopes restricted to frequent HLA supertypes. The rationale for selecting HIV peptides and adjuvants are provided. Peptide subunit vaccines are regarded as safe due to the simplicity, quality, purity, and low toxicity. The caveat is reduced immunogenicity and hence adjuvants are included to enhance and direct the immune response. Although the vaccine has been tested in ART naïve individuals, we recommend future testing of the vaccine during (early started) ART that improves immune function and to select individuals likely to benefit. Peptides representing other epitopes may be used.

Elite control of HIV: is this the right model for a functional cure?

A cure for HIV is still greatly needed and has become a global research priority. A unique subset of HIV-infected individuals who spontaneously control HIV exists, and these are known as 'elite controllers'. They may represent a natural model for a 'functional cure' in which there is long term control of viral replication and remission from symptoms of HIV infection in the absence of antiretroviral therapy. However, controllers have evidence of ongoing inflammation, CD4(+) T cell depletion, and perhaps even inflammation-associated cardiovascular disease, suggesting that this natural long term virologic control may be coming at an immunologic and clinical cost. These individuals may continue to provide continued insights into mechanisms of host control; however, they may not represent the best model of a functional cure, if we believe that a cure should require a disease-free (and not just a treatment-free) state.

Dendritic cell-based therapeutic vaccine elicits polyfunctional HIV-specific T-cell immunity associated with control of viral load

Efforts aimed at restoring robust immune responses limiting human immunodeficiency virus (HIV)-1 replication therapeutically are warranted. We report that vaccination with dendritic cells generated ex vivo and loaded with HIV lipopeptides in patients (n = 19) on antiretroviral therapy was well tolerated and immunogenic. Vaccination increased: (i) the breadth of the immune response from 1 (1-3) to 4 (2-5) peptide-pool responses/patient (p = 0.009); (ii) the frequency of functional T cells (producing at least two cytokines among IFN-γ, TNF-α, and IL-2) from 0.026 to 0.32% (p = 0.002) and from 0.26 to 0.35% (p = 0.005) for CD4(+) and CD8(+) T cells, respectively; and (iii) the breadth of cytokines secreted by PBMCs upon antigen exposure, including IL-2, IFN-γ, IL-21, IL-17, and IL-13. Fifty percent of patients experienced a maximum of viral load (VL) 1 log10 lower than the other half following antiretroviral treatment interruption. An inverse correlation was found between the maximum of VL and the frequency of polyfunctional CD4(+) T cells (p = 0.007), production of IL-2 (p = 0.006), IFN-γ (p = 0.01), IL-21 (p = 0.006), and IL-13 (p = 0.001). These results suggest an association between vaccine responses and a better control of viral replication. These findings will help in the development of strategies for a functional cure for HIV infection.

Peptide-MHC multimer-based monitoring of CD8 T-cells in HIV-1 infection and AIDS vaccine development

The use of MHC multimers allows precise and direct detecting and analyzing of antigen-specific T-cell populations and provides new opportunities to characterize T-cell responses in humans and animals. MHC-multimers enable us to enumerate specific T-cells targeting to viral, tumor and vaccine antigens with exceptional sensitivity and specificity. In the field of HIV/SIV immunology, this technique provides valuable information about the frequencies of HIV- and SIV-specific CD8(+) cytotoxic T lymphocytes (CTLs) in different tissues and sites of infection, AIDS progression, and pathogenesis. Peptide-MHC multimer technology remains a very sensitive tool in detecting virus-specific T -cells for evaluation of the immunogenicity of vaccines against HIV-1 in preclinical trials. Moreover, it helps to understand how immune responses are formed following vaccination in the dynamics from priming point until T-cell memory is matured. Here we review a diversity of peptide-MHC class I multimer applications for fundamental immunological studies in different aspects of HIV/SIV infection and vaccine development.

HIV control is mediated in part by CD8+ T-cell targeting of specific epitopes

We investigated the hypothesis that the correlation between the class I HLA types of an individual and whether that individual spontaneously controls HIV-1 is mediated by the targeting of specific epitopes by CD8(+) T cells. By measuring gamma interferon enzyme-linked immunosorbent spot (ELISPOT) assay responses to a panel of 257 optimally defined epitopes in 341 untreated HIV-infected persons, including persons who spontaneously control viremia, we found that the correlation between HLA types and control is mediated by the targeting of specific epitopes. Moreover, we performed a graphical model-based analysis that suggested that the targeting of specific epitopes is a cause of such control--that is, some epitopes are protective rather than merely associated with control--and identified eight epitopes that are significantly protective. In addition, we use an in silico analysis to identify protein regions where mutations are likely to affect the stability of a protein, and we found that the protective epitopes identified by the ELISPOT analysis correspond almost perfectly to such regions. This in silico analysis thus suggests a possible mechanism for control and could be used to identify protective epitopes that are not often targeted in natural infection but that may be potentially useful in a vaccine. Our analyses thus argue for the inclusion (and exclusion) of specific epitopes in an HIV vaccine.

IMPORTANCE

Some individuals naturally control HIV replication in the absence of antiretroviral therapy, and this ability to control is strongly correlated with the HLA class I alleles that they express. Here, in a large-scale experimental study, we provide evidence that this correlation is mediated largely by the targeting of specific CD8(+) T-cell epitopes, and we identify eight epitopes that are likely to cause control. In addition, we provide an in silico analysis indicating that control occurs because mutations within these epitopes change the stability of the protein structures. This in silico analysis also identified additional epitopes that are not typically targeted in natural infection but may lead to control when included in a vaccine, provided that other epitopes that would otherwise distract the immune system from targeting them are excluded from the vaccine.

Epitope specificity delimits the functional capabilities of vaccine-induced CD8 T cell populations

Despite progress toward understanding the correlates of protective T cell immunity in HIV infection, the optimal approach to Ag delivery by vaccination remains uncertain. We characterized two immunodominant CD8 T cell populations generated in response to immunization of BALB/c mice with a replication-deficient adenovirus serotype 5 vector expressing the HIV-derived Gag and Pol proteins at equivalent levels. The Gag-AI9/H-2K(d) epitope elicited high-avidity CD8 T cell populations with architecturally diverse clonotypic repertoires that displayed potent lytic activity in vivo. In contrast, the Pol-LI9/H-2D(d) epitope elicited motif-constrained CD8 T cell repertoires that displayed lower levels of physical avidity and lytic activity despite equivalent measures of overall clonality. Although low-dose vaccination enhanced the functional profiles of both epitope-specific CD8 T cell populations, greater polyfunctionality was apparent within the Pol-LI9/H-2D(d) specificity. Higher proportions of central memory-like cells were present after low-dose vaccination and at later time points. However, there were no noteworthy phenotypic differences between epitope-specific CD8 T cell populations across vaccine doses or time points. Collectively, these data indicate that the functional and phenotypic properties of vaccine-induced CD8 T cell populations are sensitive to dose manipulation, yet constrained by epitope specificity in a clonotype-dependent manner.

Provirus activation plus CD59 blockage triggers antibody-dependent complement-mediated lysis of latently HIV-1-infected cells

Latently HIV-1-infected cells are recognized as the last barrier toward viral eradication and cure. To purge these cells, we combined a provirus stimulant with a blocker of human CD59, a key member of the regulators of complement activation, to trigger Ab-dependent complement-mediated lysis. Provirus stimulants including prostratin and histone deacetylase inhibitors such as romidepsin and suberoylanilide hydroxamic acid activated proviruses in the latently HIV-1-infected T cell line ACH-2 as virion production and viral protein expression on the cell surface were induced. Romidepsin was the most attractive provirus stimulant as it effectively activated proviruses at nanomolar concentrations that can be achieved clinically. Antiretroviral drugs including two protease inhibitors (atazanavir and darunavir) and an RT inhibitor (emtricitabine) did not affect the activity of provirus stimulants in the activation of proviruses. However, saquinavir (a protease inhibitor) markedly suppressed virus production, although it did not affect the percentage of cells expressing viral Env on the cell surface. Provirus-activated ACH-2 cells expressed HIV-1 Env that colocalized with CD59 in lipid rafts on the cell surface, facilitating direct interaction between them. Blockage of CD59 rendered provirus-activated ACH-2 cells and primary human CD4(+) T cells that were latently infected with HIV-1 sensitive to Ab-dependent complement-mediated lysis by anti-HIV-1 polyclonal Abs or plasma from HIV-1-infected patients. Therefore, a combination of provirus stimulants with regulators of complement activation blockers represents a novel approach to eliminate HIV-1.

Microdevices for examining immunological responses of single cells to HIV

More than 60 million people in the world have been diagnosed with HIV infections since the virus was recognized as the causative agent of AIDS in the 1980s. Even though more than half of the infected patients have died, effective disease treatment and prevention measures have not been established. ART (antiretroviral therapy) is the only proven HIV treatment that sustains the suppression of patient viraemia. Current routine approaches to treat HIV infections are targeted at developing vaccines that will induce humoral or cell memory immune responses. However, developing an effective vaccine has been challenging because the HIV mutates rapidly, which allows the virus to evade immune surveillances established against the previous strain. In addition, the virus is able to quickly establish a reservoir and treatment is difficult because of the general lack of knowledge about HIV immune response mechanisms. This review introduces common disease symptoms and the progression of HIV infection with a brief summary of the current treatment approaches. Different cellular immune responses against HIV are also discussed, with emphasis on a nanotechnology research that has focused on probing T-cell response to HIV infection. Furthermore, we discuss recent noteworthy nanotechnology updates on T-cell response screening that is focused on HIV infection. Finally, we review potential future treatment strategies based on the correlations between T-cell response and HIV infection.

Early skewed distribution of total and HIV-specific CD8+ T-cell memory phenotypes during primary HIV infection is related to reduced antiviral activity and faster disease progression

The important role of the CD8+ T-cells on HIV control is well established. However, correlates of immune protection remain elusive. Although the importance of CD8+ T-cell specificity and functionality in virus control has been underscored, further unraveling the link between CD8+ T-cell differentiation and viral control is needed. Here, an immunophenotypic analysis (in terms of memory markers and Programmed cell death 1 (PD-1) expression) of the CD8+ T-cell subset found in primary HIV infection (PHI) was performed. The aim was to seek for associations with functional properties of the CD8+ T-cell subsets, viral control and subsequent disease progression. Also, results were compared with samples from Chronics and Elite Controllers. It was found that normal maturation of total and HIV-specific CD8+ T-cells into memory subsets is skewed in PHI, but not at the dramatic level observed in Chronics. Within the HIV-specific compartment, this alteration was evidenced by an accumulation of effector memory CD8+ T (TEM) cells over fully differentiated terminal effector CD8+ T (TTE) cells. Furthermore, higher proportions of total and HIV-specific CD8+ TEM cells and higher HIV-specific TEM/(TEM+TTE) ratio correlated with markers of faster progression. Analysis of PD-1 expression on total and HIV-specific CD8+ T-cells from PHI subjects revealed not only an association with disease progression but also with skewed memory CD8+ T-cell differentiation. Most notably, significant direct correlations were obtained between the functional capacity of CD8+ T-cells to inhibit viral replication in vitro with higher proportions of fully-differentiated HIV-specific CD8+ TTE cells, both at baseline and at 12 months post-infection. Thus, a relationship between preservation of CD8+ T-cell differentiation pathway and cell functionality was established. This report presents evidence concerning the link among CD8+ T-cell function, phenotype and virus control, hence supporting the instauration of early interventions to prevent irreversible immune damage.

Association of single nucleotide polymorphisms in the lens epithelium-derived growth factor (LEDGF/p75) with HIV-1 infection outcomes in Brazilian HIV-1+ individuals

The lens epithelium-derived growth factor p75 (LEDGF/p75), coded by the PSIP1 gene, is an important host co-factor that interacts with HIV-1 integrase to target integration of viral cDNA into active genes. The aim of this study was to investigate the association of SNPs in the PSIP1 gene with disease outcome in HIV-1 infected patients. We performed a genetic association study in a cohort of 171 HIV-1 seropositive Brazilian individuals classified as rapid progressors (RP, n = 69), typical progressors (TP, n = 79) and long-term nonprogressors (LTNP, n = 23). The exonic SNP rs61744944 and 9 tag SNPs were genotyped. A group of 192 healthy subjects was analyzed to determine the frequency of SNPs and haplotypes in the general population. Linkage disequilibrium (LD) analyses indicated that the SNPs analyzed were not in high LD (r²<0.8). Logistic regression models suggested that patients carrying the T allele rs61744944 (472L) were more likely to develop a LTNP phenotype (OR = 4.98; p = 0.05) as compared to TP group. The same trend was observed when LTNPs were compared to the RP group (OR = 3.26). Results of haplotype analyses reinforced this association, since the OR values obtained for the haplotype carrying allele T at rs61744944 also reflected an association with LTNP status (OR = 6.05; p = 0.08 and OR = 3.44; p = 0.12 for comparisons to TP and RP, respectively). The rare missense variations Ile436Ser and Thr473Ile were not identified in the patients enrolled in this study. Gene expression analyses showed lower LEDGF/p75 mRNA levels in peripheral blood mononuclear cells obtained from HIV-1 infected individuals. However, these levels were not influenced by any of the SNPs investigated. In spite of the limited number of LTNPs, these data suggest that the PSIP1 gene could be associated with the outcome of HIV-1 infection. Further analyses of this gene may guide the identification of causative variants to help predict disease course.

CD127 expression, exhaustion status and antigen specific proliferation predict sustained virologic response to IFN in HCV/HIV co-infected individuals

Hepatitis C virus (HCV) infection is a major cause of morbidity and mortality in the HIV co-infected population. Interferon-alpha (IFN-α) remains a major component of anti-HCV therapy despite its deleterious effects on the immune system. Furthermore, IFN-α was recently shown to diminish the size of the latent HIV reservoir. The objectives of this study were to monitor the impact of IFN-α on T cell phenotype and proliferation of HIV and HCV-specific T cells during IFN therapy, and to identify immune markers that can predict the response to IFN in HICV/HIV co-infected patients. We performed longitudinal analyses of T cell numbers, phenotype and function in co-infected patients undergoing IFN-α therapy with different outcomes including IFN-α non-responders (NR) (n = 9) and patients who achieved sustained virologic response (SVR) (n = 19). We examined the expression of activation (CD38, HLA-DR), functional (CD127) and exhaustion markers (PD1, Tim-3, CD160 and CD244) on total CD4 and CD8 T cells before, during and after therapy. In addition, we examined the HIV- and HCV-specific proliferative responses against HIV-p24 and HCV-NS3 proteins. Frequencies of CD127⁺ CD4 T cells were higher in SVR than in NR patients at baseline. An increase in CD127 expression on CD8 T cells was observed after IFN-α therapy in all patients. In addition, CD8 T cells from NR patients expressed a higher exhaustion status at baseline. Finally, SVR patients exhibited higher proliferative response against both HIV and HCV antigens at baseline. Altogether, SVR correlated with higher expression of CD127, lower T cell exhaustion status and better HIV and HCV proliferative responses at baseline. Such factors might be used as non-invasive methods to predict the success of IFN–based therapies in co-infected individuals.

Potential role for HIV-specific CD38-/HLA-DR+ CD8+ T cells in viral suppression and cytotoxicity in HIV controllers

Background

HIV controllers (HIC) are rare HIV-1-infected patients who exhibit spontaneous viral control. HIC have high frequency of CD38⁻/HLA-DR⁺ HIV-specific CD8⁺ T cells. Here we examined the role of this subset in HIC status.

Materials and Methods

We compared CD38⁻/HLA-DR⁺ CD8⁺ T cells with the classical CD38⁺/HLA-DR⁺ activated phenotype in terms of 1) their activation status, reflected by CD69, CD25, CD71, CD40 and Ki67 expression, 2) functional parameters: Bcl-2 expression, proliferative capacity, and IFN-γ and IL-2 production, and 3) cytotoxic activity. We also investigated how this particular profile is generated.

Results

Compared to CD38⁺/HLA-DR⁺ cells, CD38⁻/HLA-DR⁺ cells exhibited lower expression of several activation markers, better survival capacity (Bcl-2 MFI, 367 [134–462] vs 638 [307–747], P = 0.001), higher frequency of polyfunctional cells (15% [7%–33%] vs 21% [16%–43%], P = 0.0003), greater proliferative capacity (0-fold [0–2] vs 3-fold [2]–[11], P = 0.007), and higher cytotoxicity in vitro (7% [3%–11%] vs 13% [6%–22%], P = 0.02). The CD38⁻/HLA-DR⁺ profile was preferentially generated in response to low viral antigen concentrations.

Conclusions

These data highlight the role of CD38⁻/HLA-DR⁺ HIV-specific CD8⁺ T cell cytotoxicity in HIC status and provide insights into the mechanism by which they are generated. Induction of this protective CD8⁺ subset may be important for vaccine strategies.