HIV-1-specific CD4+ T cells are detectable in most individuals with active HIV-1 infection, but decline with prolonged viral suppression

Multiple treatment interruptions and protecting HIV-specific CD4 T cells enable durable CD8 T cell response and viral control

Human Immunodeficiency Virus (HIV) remains a global health challenge, and novel approaches to improve HIV control are significantly important. The cell and gene therapy product AGT103-T was previously evaluated (NCT04561258) for safety, immunogenicity, and persistence in seven patients for up to 180 days post infusion. In this study, we sought to investigate the impact of AGT103-T treatment upon analytical treatment interruptions (ATIs). Six patients previously infused with AGT103-T were enrolled into an ATI study (NCT05540964), wherein they suspended their antiretroviral therapy (ART) until their viral load reached 100,000 copies/mL in two successive visits, or their CD4 count was reduced to below 300 cells/μL. During the ATI, all patients experienced viral rebound followed by a notable expansion in HIV specific immune responses. The participants demonstrated up to a five-fold increase in total CD8 counts over baseline approximately 1-2 weeks followed by the peak viremia. This coincided with a rise in HIV-specific CD8 T cells, which was attributed to the increase in antigen availability and memory recall. Thus, the protocol was amended to include a second ATI with the first ATI serving as an "auto-vaccination." Four patients participated in a second ATI. During the second ATI, the Gag-specific CD8 T cells were either maintained or rose in response to viral rebound and the peak viremia was substantially decreased. The patients reached a viral set point ranging from 7,000 copies/mL to 25,000 copies/mL. Upon resuming ART, all participants achieved viral control more rapidly than during the first ATI, with CD4 counts remaining within 10% of baseline measurements and without any serious adverse events or evidence of drug resistance. In summary, the rise in CD8 counts and the viral suppression observed in 100% of the study participants are novel observations demonstrating that AGT103-T gene therapy when combined with multiple ATIs, is a safe and effective approach for achieving viral control, with viral setpoints consistently below 25,000 copies/mL and relatively stable CD4 T cell counts. We conclude that HIV cure-oriented cell and gene therapy trials should include ATI and may benefit from designs that include multiple ATIs when induction of CD8 T cells is required to establish viral control.

HIV-1-specific T-cell responses and exhaustion profiles in people with HIV after switching to dual therapy vs. maintaining triple therapy based on integrase inhibitors

BACKGROUND

Dual therapy (DT) has shown comparable results to triple therapy (TT) in efficacy and other immunological aspects. However, there are still some concerns about DT, including several immunological features. Therefore, we evaluated whether HIV-1-specific memory T-cell responses and exhaustion phenotypes are adversely influenced after simplification to DT.

METHODS

HIV-1-specific CD4+ and CD8+ T-cell responses were assessed by intracellular cytokine and degranulation marker staining, and polyfunctionality indexes after stimulation with a Gag peptide pool. Exhaustion phenotypes were evaluated by PD-1, TIM-3, and LAG-3 expression in CD4+ and CD8+ T cells.

RESULTS

Forty participants in the TRIDUAL trial (ClinicalTrials.gov: NCT03447873) who were randomized to continue integrase inhibitor-based TT (n = 20) or to switch to DT (dolutegravir or darunavir/cobicistat plus lamivudine) (n = 20). After 96 weeks, the magnitude of CD4+ and CD8+ T-cell responses was similar in both treatment arms (p = 0.221 and p = 0.602, respectively). The CD4+ polyfunctionality index decreased in the TT arm (p = 0.013) and remained stable in the DT arm, while the polyfunctionality of CD8+ T cells was unchanged in both arms. There was a significant decrease in the expression of PD-1, TIM-3, and the co-expression of PD-1+TIM-3+LAG-3+, and PD-1 +TIM-3 + in both CD4+ and CD8+ T cells. However, the decrease in the expression of exhaustion markers did not improve HIV-1-specific T-cell responses.

CONCLUSIONS

Our results suggest that simplification to DT does not negatively influence the HIV-1-specific T-cell response or the exhaustion phenotype after 96 weeks of follow-up.

Contribution of the HIV-1 Envelope Glycoprotein to AIDS Pathogenesis and Clinical Progression

In the absence of antiviral therapy, HIV-1 infection progresses to a wide spectrum of clinical manifestations that are the result of an entangled contribution of host, immune and viral factors. The contribution of these factors is not completely established. Several investigations have described the involvement of the immune system in the viral control. In addition, distinct HLA-B alleles, HLA-B27, -B57-58, were associated with infection control. The combination of these elements and antiviral host restriction factors results in different clinical outcomes. The role of the viral proteins in HIV-1 infection has been, however, less investigated. We will review contributions dedicated to the pathogenesis of HIV-1 infection focusing on studies identifying the function of the viral envelope glycoprotein (Env) in the clinical progression because of its essential role in the initial events of the virus life-cycle. Some analysis showed that inefficient viral Envs were dominant in non-progressor individuals. These poorly-functional viral proteins resulted in lower cellular activation, viral replication and minor viral loads. This limited viral antigenic production allows a better immune response and a lower immune exhaustion. Thus, the properties of HIV-1 Env are significant in the clinical outcome of the HIV-1 infection and AIDS pathogenesis.

A role for CD4 + helper cells in HIV control and progression

OBJECTIVE

It remains unclear why HIV persists in most untreated individuals, and why a small minority of individuals can control the virus, either spontaneously or after an early treatment. Striking differences have been discovered between patient cohorts in CD4 + T-cell avidity but not in CD8 + T-cell avidity. The present work has the aim to explain the diverse outcome of infection and identify the key virological and immunological parameters predicting the outcome.

DESIGN AND METHOD

A mathematical model informed by these experiments and taking into account the details of HIV virology is developed.

RESULTS

The model predicts an arms race between viral dissemination and the proliferation of HIV-specific CD4 + helper cells leading to one of two states: a low-viremia state (controller) or a high-viremia state (progressor). Helper CD4 + cells with a higher avidity favor virus control. The parameter segregating spontaneous and posttreatment controllers is the infectivity difference between activated and resting CD4 + T cells. The model is shown to have a better connection to experiment than a previous model based on T-cell 'exhaustion'.

CONCLUSION

Using the model informed by patient data, the timing of antiretroviral therapy can be optimized.

Multi-targeted drug repurposing approach for breast cancer via integrated functional network analysis

The present study focuses on the interconnected functional network of altered metabolism and EMT (epithelial to mesenchymal transition) signaling in breast cancer. We have interlinked the metabolic and EMT signaling circuits and selected Insulin receptor (IR), Integrin beta 1 (ITGB1), and CD36 as target proteins based on network analysis. Extensive computational approaches discerned the potential drug molecules from the library of 1293 FDA-approved drugs to block all three target proteins. Using molecular docking, molecular dynamics simulation, and MMPBSA binding free energy studies, Capmatinib, Ponatinib, Naldemedine, and Pimozide were identified as potential repurposed drugs to block the function of all three target proteins. Among in silico selected candidate drugs, Pimozide, a known anti-psychotic drug, was further validated using in-vitro studies for its anti-cell proliferative potential on breast cancer cell lines (namely, MCF7, MDAMB231 and MDAMB468). The inhibitory concentration (IC50) values of MCF7, MDAMB231 and MDAMB468 was found to be 16.26 µM, 20.82 µM and 13.10 µM, respectively. The effect of Pimozide on EMT-induced MDAMB231 and MDAMB468 cells was evident from their IC50 values of 7.85 µM and 6.83 µM, respectively. The potent anti-cancer property of Pimozide has opened up avenues for drug repurposing towards 'multi-targeted therapy' in EMT dynamics.

Immunogenicity of personalized dendritic-cell therapy in HIV-1 infected individuals under suppressive antiretroviral treatment: interim analysis from a phase II clinical trial

Background

We developed a personalized Monocyte-Derived Dendritic-cell Therapy (MDDCT) for HIV-infected individuals on suppressive antiretroviral treatment and evaluated HIV-specific T-cell responses.

Methods

PBMCs were obtained from 10 HIV⁺ individuals enrolled in trial NCT02961829. Monocytes were differentiated into DCs using IFN-α and GM-CSF. After sequencing each patient’s HIV-1 Gag and determining HLA profiles, autologous Gag peptides were selected based on the predicted individual immunogenicity and used to pulse MDDCs. Three doses of the MDDCT were administered every 15 days. To assess immunogenicity, patients’ cells were stimulated in vitro with autologous peptides, and intracellular IL-2, TNF, and interferon-gamma (IFN-γ) production were measured in CD4⁺ and CD8⁺ T-cells.

Results

The protocol of ex-vivo treatment with IFN-α and GM-CSF was able to induce maturation of MDDCs, as well as to preserve their viability for reinfusion. MDDCT administration was associated with increased expression of IL-2 in CD4⁺ and CD8⁺ T-cells at 15 and/or 30 days after the first MDDCT administration. Moreover, intracellular TNF and IFN-γ expression was significantly increased in CD4⁺ T-cells. The number of candidates that increased in vitro the cytokine levels in CD4⁺ and CD8⁺ T cells upon stimulation with Gag peptides from baseline to day 15 and from baseline to day 30 and day 120 after MDDCT was significant as compared to Gag unstimulated response. This was accompanied by an increasing trend in the frequency of polyfunctional T-cells over time, which was visible when considering both cells expressing two and three out of the three cytokines examined.

Conclusions

MDDC had a mature profile, and this MDDCT promoted in-vitro T-cell immune responses in HIV-infected patients undergoing long-term suppressive antiretroviral treatment.

Trial registration NCT02961829: (Multi Interventional Study Exploring HIV-1 Residual Replication: a Step Towards HIV-1 Eradication and Sterilizing Cure, https://www.clinicaltrials.gov/ct2/show/NCT02961829, posted November 11th, 2016)

Supplementary Information

The online version contains supplementary material available at 10.1186/s12981-021-00426-z.

The relationship between sex-related alcohol expectancies and hazardous drinking among persons with HIV disease

Hazardous drinking is a clinically significant problem among persons with HIV (PWH) disease, and is associated with a number of poor outcomes. Hazardous drinking among PWH is associated with risky substance use and sexual behavior, but little work has examined factors that may be associated with greater hazardous drinking and subsequent risky sexual behaviors among PWH. Research among the general population suggests that sex-related alcohol expectancies, defined as drinking to enhance sexual experience, increase sexual risk-taking, and disinhibition of sexual behavior, are associated with greater hazardous alcohol use and risky sexual behavior, but these relations have not been explored among PWH. Therefore, the current study examined the associations of sex-related alcohol expectancies with hazardous alcohol consumption, dependence, and problems among 146 PWH (M_age = 50.99, SD = 9.41) \ enrolled in a clinical trial examining a personalized feedback intervention to reduce hazardous drinking in primary HIV care. Results showed that only sexual disinhibition-related alcohol expectancies were significantly associated with the criterion variables, such that greater drinking alcohol for sexual disinhibition was associated with greater hazardous drinking behaviors. These results sit on the backdrop of a larger literature documenting the links between disinhibition and hazardous alcohol use and provide explanatory specificity to PWH who are hazardous drinkers.

Theranostic Advances in Breast Cancer in Nuclear Medicine

The implication of 'theranostic' refers to targeting an identical receptor for diagnostic and therapeutic purposes, by the same radioligand, simultaneously or separately. In regard to extensive efforts, many considerable theranostic tracers have been developed in recent years. Emerging evidence strongly demonstrates the tendency of nuclear medicine towards therapies based on a diagnosis. This review is focused on the examples of targeted radiopharmaceuticals for the imaging and therapy of breast cancer.

Droplet-based mRNA sequencing of fixed and permeabilized cells by CLInt-seq allows for antigen-specific TCR cloning

T cell receptors (TCRs) surveil cellular environment by recognizing peptides presented by the major histocompatibility complex. TCR sequencing allows for understanding the scope of T cell reactivity in health and disease. Specific TCR clones can be used as therapeutics in cancer and autoimmune disease. We present a technique that allows for TCR sequencing based on intracellular signaling molecules, such as cytokines and transcription factors. The core concept is highly generalizable and should be applicable to global gene expression analysis where intracellular marker-based cell isolation is required.

T cell receptors (TCRs) are generated by somatic recombination of V/D/J segments to produce up to 10¹⁵ unique sequences. Highly sensitive and specific techniques are required to isolate and identify the rare TCR sequences that respond to antigens of interest. Here, we describe the use of mRNA sequencing via cross-linker regulated intracellular phenotype (CLInt-Seq) for efficient recovery of antigen-specific TCRs in cells stained for combinations of intracellular proteins such as cytokines or transcription factors. This method enables high-throughput identification and isolation of low-frequency TCRs specific for any antigen. As a proof of principle, intracellular staining for TNFα and IFNγ identified cytomegalovirus (CMV)- and Epstein-Barr virus (EBV)-reactive TCRs with efficiencies similar to state-of-the-art peptide-MHC multimer methodology. In a separate experiment, regulatory T cells were profiled based on intracellular FOXP3 staining, demonstrating the ability to examine phenotypes based on transcription factors. We further optimized the intracellular staining conditions to use a chemically cleavable primary amine cross-linker compatible with current single-cell sequencing technology. CLInt-Seq for TNFα and IFNγ performed similarly to isolation with multimer staining for EBV-reactive TCRs. We anticipate CLInt-Seq will enable droplet-based single-cell mRNA analysis from any tissue where minor populations need to be isolated by intracellular markers.

The single-cell landscape of immunological responses of CD4+ T cells in HIV versus severe acute respiratory syndrome coronavirus 2

PURPOSE OF REVIEW

CD4 T cell loss is the hallmark of uncontrolled HIV-1 infection. Strikingly, CD4 T cell depletion is a strong indicator for disease severity in the recently emerged coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We reviewed recent single-cell immune profiling studies in HIV-1 infection and COVID-19 to provide critical insight in virus-induced immunopathogenesis.

RECENT FINDINGS

Cytokine dysregulation in HIV-1 leads to chronic inflammation, while severe SARS-CoV-2 infection induces cytokine release syndrome and increased mortality. HIV-1-specific CD4 T cells are dysfunctional, while SARS-CoV-2-specific CD4 T cells exhibit robust Th1 function and correlate with protective antibody responses. In HIV-1 infection, follicular helper T cells (TFH) are susceptible to HIV-1 infection and persist in immune-sanctuary sites in lymphoid tissues as an HIV-1 reservoir. In severe SARS-CoV-2 infection, TFH are absent in lymphoid tissues and are associated with diminished protective immunity. Advancement in HIV-1 DNA, RNA, and protein-based single-cell capture methods can overcome the rarity and heterogeneity of HIV-1-infected cells and identify mechanisms of HIV-1 persistence and clonal expansion dynamics.

SUMMARY

Single-cell immune profiling identifies a high-resolution picture of immune dysregulation in HIV-1 and SARS-CoV-2 infection and informs outcome prediction and therapeutic interventions.

Evaluation of HIV-specific T-cell responses in HIV-infected older patients with controlled viremia on long-term antiretroviral therapy

HIV-infected older individuals may have a diminished immune response because of exhaustion/immune aging of T-cells. Therefore, we have investigated HIV-specific CD4 and CD8 T-cell responses in 100 HIV-infected patients (HIV⁺) who have aged on long-term antiretroviral therapy (ART) and achieved controlled viremia (mostly undetectable viral load; 92 patients with <20 to <40 HIV RNA copies/mL and 8 <60 to <100) and improved CD4 T-cell counts. We show that the median frequencies of HIV-specific CD4⁺ and CD8⁺ IFN-γ T-cells were higher in HIV⁺ than uninfected individuals (HIV^-), including increasing levels of IFN-γproduced by CD4⁺ T-cells and decreasing levels by CD8⁺ T-cells with increasing CD4 T-cell counts in HIV⁺. No correlation was found between T-cell responses and varying levels of undetectable viremia. HIV-specific TNF-α made by CD8⁺ T-cells was higher in HIV⁺ than HIV^-, including decreasing levels with increasing CD4 T-cell counts in HIV⁺. Furthermore, the CD8⁺ T-cell mediators, CD107a and Granzyme-B, were higher in HIV⁺ than HIV^-, and decreased with increasing CD4 T-cell counts in HIV⁺. Remarkably, HIV-specific CD8 T-cells produced decreasing levels of IFN-γwith increasing age of HIV⁺, including decreased levels of CD107a and Granzyme-B in older HIV⁺. However, HIV-specific CD8⁺ T-cells produced increasing levels of TNF-α with increasing age of the HIV⁺, suggesting continued inflammation. In conclusion, HIV⁺ with controlled viremia on long-term ART and with higher CD4 T-cell counts showed reduced HIV-specific CD8 T-cell responses as compared to those with lower CD4 T-cell counts, and older HIV⁺ exhibited decreasing levels of CD8 T-cell responses with increasing age.

Persistent expansion and Th1-like skewing of HIV-specific circulating T follicular helper cells during antiretroviral therapy

Background

Untreated HIV infection leads to alterations in HIV-specific CD4⁺ T cells including increased expression of co-inhibitory receptors (IRs) and skewing toward a T follicular helper cell (Tfh) signature. However, which changes are maintained after suppression of viral replication with antiretroviral therapy (ART) is poorly known.

Methods

We analyzed blood CD4⁺ T cells specific to HIV and comparative viral antigens in ART-treated people using a cytokine-independent activation-induced marker assay alone or in combination with functional readouts.

Findings

In intra-individual comparisons, HIV-specific CD4⁺ T cells were characterized by a larger fraction of circulating Tfh (cTfh) cells than CMV- and HBV-specific cells and preferentially expressed multiple IRs and showed elevated production of the Tfh cytokines CXCL13 and IL-21. In addition, HIV-specific cTfh exhibited a predominant Th1-like phenotype and function when compared to cTfh of other specificities, contrasting with a reduction in Th1-functions in HIV-specific non-cTfh. Using longitudinal samples, we demonstrate that this distinct HIV-specific cTfh profile was induced during chronic untreated HIV infection, persisted on ART and correlated with the translation-competent HIV reservoir but not with the total HIV DNA reservoir.

Interpretation

Expansion and altered features of HIV-specific cTfh cells are maintained during ART and may be driven by persistent HIV antigen expression.

Funding

This work was supported by the National Institutes of Health (NIH), the Canadian Institutes of Health Research (CIHR) and the FRQS AIDS and Infectious Diseases Network.

The forces driving clonal expansion of the HIV-1 latent reservoir

Despite antiretroviral therapy (ART) which halts HIV-1 replication and reduces plasma viral load to clinically undetectable levels, viral rebound inevitably occurs once ART is interrupted. HIV-1-infected cells can undergo clonal expansion, and these clonally expanded cells increase over time. Over 50% of latent reservoirs are maintained through clonal expansion. The clonally expanding HIV-1-infected cells, both in the blood and in the lymphoid tissues, contribute to viral rebound. The major drivers of clonal expansion of HIV-1-infected cells include antigen-driven proliferation, homeostatic proliferation and HIV-1 integration site-dependent proliferation. Here, we reviewed how viral, immunologic and genomic factors contribute to clonal expansion of HIV-1-infected cells, and how clonal expansion shapes the HIV-1 latent reservoir. Antigen-specific CD4⁺ T cells specific for different pathogens have different clonal expansion dynamics, depending on antigen exposure, cytokine profiles and exhaustion phenotypes. Homeostatic proliferation replenishes the HIV-1 latent reservoir without inducing viral expression and immune clearance. Integration site-dependent proliferation, a mechanism also deployed by other retroviruses, leads to slow but steady increase of HIV-1-infected cells harboring HIV-1 proviruses integrated in the same orientation at specific sites of certain cancer-related genes. Targeting clonally expanding HIV-1 latent reservoir without disrupting CD4⁺ T cell function is a top priority for HIV-1 eradication.

T cell functionality in HIV-1, HIV-2 and dually infected individuals: correlates of disease progression and immune restoration

The role of suppressive anti-retroviral therapy (ART) in eliciting restoration of dysregulated immune function remains unclear in HIV-1 infection. Also, due to tailoring of therapeutic regimens towards HIV-1, this possible impairment of therapy may be even more pronounced in HIV-2 and dual (HIV-D) infection. Thus, we evaluated the impact of ART on immune restoration by assessing T cell functions, including HIV specific responses in HIV-1-, HIV-2- and HIV-D-infected individuals. Both ART-treated and naive infected subjects showed persistently altered frequency of CD4+ T cell subsets [regulatory T cells (Treg ), naive/central memory, effector memory], increased immune activation, cytoxicity and decreased frequency of natural killer T (NKT)- like cells and T helper type 17 (Th17)/Treg ratio with elevated microbial translocation. Further, HIV-specific responses were dominated by gag-specific CD4+ T cells in virologically suppressed HIV-D individuals, suggesting retention of T cell memory for both viruses. Increased antigen-specific responses, including dual-functional interleukin (IL)-2/interferon (IFN)-γ CD4+ T cells, were detected in therapy receiving HIV-2-infected individuals indicative of a greater and more functionally diverse T cell memory repertoire. We delineated immune signatures specific to therapy-naive single HIV infection, as well as a unique signature associated with HIV-2 disease progression and immune restoration. Circulating Treg frequency, T cell activation and microbial translocation levels correlated with disease progression and immune restoration among all types of HIV infection. Also, memory responses negatively correlated, irrespective of type of infection, in ART receiving infected individuals, with CD4 rebound and decreased pan T cell activation. Our data highlight the need for adjunct immunomodulatory therapeutic strategies to achieve optimal immune restoration in HIV infection.

Cytotoxic CD4+ T-cells during HIV infection: Targets or weapons?

Classically, CD4⁺ T-cells have been referred as cytokine-producing cells and important players in immune responses by providing soluble factors that potentiate several effector immune functions. However, it is now evident that CD4⁺ T-cells can also elaborate cytotoxic responses, inducing apoptosis of target cells. Cytotoxic CD4⁺ T cells (CD4⁺ CTLs), exhibit cytolytic functions that resemble those of CD8⁺ T-cells; in fact, there is evidence suggesting that they may have a role in the control of viral infections. In this article, we discuss the role of CD4⁺ CTLs during HIV infection, where CD4⁺ CTLs have been associated with viral control and slow disease progression. In addition, we address the implication of CD4⁺ CTLs in the context of antiretroviral therapy and the partial reconstitution of CD8⁺ T-cells effector function.

10-year outcome of temporary structured treatment interruption (STI) among HIV-1-infected patients: An observational study in a single medical center

BACKGROUND

Lifelong antiretroviral therapy (ART) is recommended for HIV-1 infected patients but may lead to intolerance or poor adherence. Structured treatment interruption (STI) is a strategy for drug holiday or to boost HIV-specific immunity. But the long-term outcome of STI was never reported in literature.

METHODS

This is a single-center observational study. We followed the HIV-infected patients who already had a stable viral suppression and voluntarily started temporary STI with a fixed 12-week interval after counseling, evaluation and education. HIV-1-specific T cell response was also measured in some patients.

RESULTS

Totally 34 HIV-infected patients received temporary STI since July, 2006. 18 patients completed 10-year follow-up. All patients received protease inhibitors (PI)-based ART before and during temporary STI. The patients received temporary STI with a period of 36-85 weeks. All of them reached viral suppression after 12 weeks of restarting continuous ART. No viral rebound or opportunistic disease was recorded during follow-up. No adverse event or comorbidity was attributed to STI. The plasma viral load (PVL) at the end of STI was significantly lower than baseline PVL in patients with a longer duration of STI (≤36 weeks vs. >36 weeks, P = 0.005). The T cell response study revealed that cyclically increased HIV-1-specific T cell response after starting STI in patients with baseline CD4+ count >350/μL.

CONCLUSION

Temporary STI may not lead to worse long-term outcome among highly selected patients. The policy may partially control viral replication through reminding the HIV-1 specific T cell immunity.

Have Cells Harboring the HIV Reservoir Been Immunoedited?

Immunoediting is an important concept in oncology, delineating the mechanisms through which tumors are selected for resistance to immune-mediated elimination. The recent emergence of immunotherapies, such as checkpoint inhibitors, as pillars of cancer therapy has intensified interest in immunoediting as a constraint limiting the efficacy of these approaches. Immunoediting manifests at a number of levels for different cancers, for example through the establishment of immunosuppressive microenvironments within solid tumors. Of particular interest to the current review, selection also occurs at the cellular level; and recent studies have revealed novel mechanisms by which tumor cells acquire intrinsic resistance to immune recognition and elimination. While the selection of escape mutations in viral epitopes by HIV-specific T cells, which is a hallmark of chronic HIV infection, can be considered a form of immunoediting, few studies have considered the possibility that HIV-infected cells themselves may parallel tumors in having differential intrinsic susceptibilities to immune-mediated elimination. Such selection, on the level of an infected cell, may not play a significant role in untreated HIV, where infection is propagated by high levels of cell-free virus produced by cells that quickly succumb to viral cytopathicity. However, it may play an unappreciated role in individuals treated with effective antiretroviral therapy where viral replication is abrogated. In this context, an "HIV reservoir" persists, comprising long-lived infected cells which undergo extensive and dynamic clonal expansion. The ability of these cells to persist in infected individuals has generally been attributed to viral latency, thought to render them invisible to immune recognition, and/or to their compartmentalization in anatomical sites that are poorly accessible to immune effectors. Recent data from ex vivo studies have led us to propose that reservoir-harboring cells may additionally have been selected for intrinsic resistance to CD8+ T cells, limiting their elimination even in the context of antigen expression. Here, we draw on knowledge from tumor immunoediting to discuss potential mechanisms by which clones of HIV reservoir-harboring cells may resist elimination by CD8+ T cells. The establishment of such parallels may provide a premise for testing therapeutics designed to sensitize tumor cells to immune-mediated elimination as novel approaches aimed at curing HIV infection.

Broad Recognition of Circulating HIV-1 by HIV-1-Specific Cytotoxic T-Lymphocytes with Strong Ability to Suppress HIV-1 Replication

HIV-1-specific cytotoxic T-lymphocytes (CTLs) with strong abilities to suppress HIV-1 replication and recognize most circulating HIV-1 strains are candidates for effector T cells for cure treatment and prophylactic AIDS vaccine. Previous studies demonstrated that the existence of CTLs specific for 11 epitopes was significantly associated with good clinical outcomes in Japan, although CTLs specific for one of these epitopes select for escape mutations. However, it remains unknown whether the CTLs specific for the remaining 10 epitopes suppress HIV-1 replication in vitro and recognize circulating HIV-1. Here, we investigated the abilities of these CTLs to suppress HIV-1 replication and to recognize variants in circulating HIV-1. CTL clones specific for 10 epitopes had strong abilities to suppress HIV-1 replication in vitro The ex vivo and in vitro analyses of T-cell responses to variant epitope peptides showed that the T cells specific for 10 epitopes recognized mutant peptides which are detected in 84.1% to 98.8% of the circulating HIV-1 strains found in HIV-1-infected Japanese individuals. In addition, the T cells specific for 5 epitopes well recognized target cells infected with 7 mutant viruses that had been detected in >5% of tested individuals. Taken together, these results suggest that CTLs specific for the 10 epitopes effectively suppress HIV-1 replication and broadly recognize the circulating HIV-1 strains in the HIV-1-infected individuals. This study suggests the use of these T cells in clinical trials.IMPORTANCE In recent T-cell AIDS vaccine trials, the vaccines did not prevent HIV-1 infection, although HIV-1-specific T cells were induced in the vaccinated individuals, suggesting that the T cells have a weak ability to suppress HIV-1 replication and fail to recognize circulating HIV-1. We previously demonstrated that the T-cell responses to 10 epitopes were significantly associated with good clinical outcome. However, there is no direct evidence that these T cells have strong abilities to suppress HIV-1 replication and recognize circulating HIV-1. Here, we demonstrated that the T cells specific for the 10 epitopes had strong abilities to suppress HIV-1 replication in vitro Moreover, the T cells cross-recognized most of the circulating HIV-1 in HIV-1-infected individuals. This study suggests the use of T cells specific for these 10 epitopes in clinical trials of T-cell vaccines as a cure treatment.

Tfh1 Cells in Germinal Centers During Chronic HIV/SIV Infection

T follicular helper CD4 cells (Tfh) are essential for the development and maintenance of germinal center (GC) reactions, a critical process that promotes the generation of long-lived high affinity humoral immunity. It is becoming increasingly evident that GC-Tfh cells are heterogeneous in nature with some cellular characteristics associated with a Th1, Th2, and Th17 phenotype. Emerging studies suggest that GC-Tfh cells are directed to differentiate into distinct phenotypes during chronic HIV/SIV infection and these changes in GC-Tfh cells can greatly impact the B cell response and subclass of antibodies generated. Studies in HIV-infected humans have shown that certain Tfh phenotypes are associated with the generation of broadly neutralizing antibody responses. Moreover, the susceptibility of particular GC-Tfh subsets to HIV infection within the secondary lymphoid sites can also impact GC-Tfh/B cell interactions. In this review, we discuss the recent advances that show Tfh heterogeneity during chronic HIV/SIV infection. In particular, we will discuss the dynamics of GC-Tfh cells, their altered differentiation state and function, and their impact on B cell responses during HIV/SIV infection. In addition, we will also discuss the potential role of a recently described novel subset of follicular homing CXCR5⁺ CD8 T cells (Tfc) and their importance in contributing to control of chronic HIV/SIV infection. A better understanding of the mechanistic role of follicular homing CD4 and CD8 T cells during HIV/SIV infection will aid in the design of vaccines and therapeutic strategies to prevent and treat HIV/AIDS.

Targeting the Latent Reservoir for HIV-1

Antiretroviral therapy can effectively block HIV-1 replication and prevent or reverse immunodeficiency in HIV-1-infected individuals. However, viral replication resumes within weeks of treatment interruption. The major barrier to a cure is a small pool of resting memory CD4+ T cells that harbor latent HIV-1 proviruses. This latent reservoir is now the focus of an intense international research effort. We describe how the reservoir is established, challenges involved in eliminating it, and pharmacologic and immunologic strategies for targeting this reservoir. The development of a successful cure strategy will most likely require understanding the mechanisms that maintain HIV-1 proviruses in a latent state and pathways that drive the proliferation of infected cells, which slows reservoir decay. In addition, a cure will require the development of effective immunologic approaches to eliminating infected cells. There is renewed optimism about the prospect of a cure, and the interventions discussed here could pave the way.

Nonprogressing HIV-infected children share fundamental immunological features of nonpathogenic SIV infection

Disease-free infection in HIV-infected adults is associated with human leukocyte antigen-mediated suppression of viremia, whereas in the sooty mangabey and other healthy natural hosts of simian immunodeficiency virus (SIV), viral replication continues unabated. To better understand factors preventing HIV disease, we investigated pediatric infection, where AIDS typically develops more rapidly than in adults. Among 170 nonprogressing antiretroviral therapy-naïve children aged >5 years maintaining normal-for-age CD4 T cell counts, immune activation levels were low despite high viremia (median, 26,000 copies/ml). Potent, broadly neutralizing antibody responses in most of the subjects and strong virus-specific T cell activity were present but did not drive pediatric nonprogression. However, reduced CCR5 expression and low HIV infection in long-lived central memory CD4 T cells were observed in pediatric nonprogressors. These children therefore express two cardinal immunological features of nonpathogenic SIV infection in sooty mangabeys-low immune activation despite high viremia and low CCR5 expression on long-lived central memory CD4 T cells-suggesting closer similarities with nonpathogenetic mechanisms evolved over thousands of years in natural SIV hosts than those operating in HIV-infected adults.

Parvovirus B19 in HIV+ adult patients with different CD4+ lymphocyte counts

PURPOSE

Human parvovirus B19 (B19V) can cause anemia in immunocompromised patients. We aimed to investigate the presence of B19V in HIV+ adults with different CD4+ T cell counts, to recognise the frequency of B19V in these different conditions and its possible association with anemia.

METHODOLOGY

We studied B19V specific IgM, IgG and DNA in 98 HIV+ patients and in 52 healthy individuals. HIV load, CD4+ counts and haemoglobin level were also determined in the patients.

RESULTS

No individual in the control group had detectable IgM, 41/52 (78.8 %) had IgG and 5/52 (9.6 %) had B19V DNA. Among HIV+ patients, we found 5/98 (5.1 %) IgM+, 66/98 (67.3 %) IgG+ and 15/98 (15.3 %) had B19V DNA (no significant differences between the two groups compared). Considering the CD4+ cell range in HIV patients, 37 had <200 CD4+ cells ml^-1, 31 had 200-500, and 30 had >500. Anti-B19V IgG prevalence in patients with >500 CD4+ cells ml^-1 was significantly higher than in the rest (P=0.004) and compared to the control (P=0.046). B19V DNA concentration was always <10³ IU ml^-1, including 5 healthy individuals and 15 HIV+ patients. There was no significant association between B19V IgM or DNA and anemia nor between B19V DNA and HIV load.

CONCLUSIONS

The results indicate that B19V is not a high-risk factor for anemia in adult HIV+ patients under HAART treatment. Further studies will contribute to elucidate the mechanisms and significance of B19V DNA prevalence/persistence in adults, independently of the CD4+ cell status.

Preserved immune functionality and high CMV-specific T-cell responses in HIV-infected individuals with poor CD4+ T-cell immune recovery

Poor CD4⁺ T-cell recovery after cART has been associated with skewed T-cell maturation, inflammation and immunosenescence; however, T-cell functionality in those individuals has not been fully characterized. In the present study, we assessed T-cell function by assessing cytokine production after polyclonal, CMV and HIV stimulations of T-cells from ART-suppressed HIV-infected individuals with CD4⁺ T-cell counts >350 cells/μL (immunoconcordants) or <350 cells/μL (immunodiscordants). A group of HIV-uninfected individuals were also included as controls. Since CMV co-infection significantly affected T-cell maturation and polyfunctionality, only CMV⁺ individuals were analyzed. Despite their reduced and skewed CD4⁺ T-cell compartment, immunodiscordant individuals showed preserved polyclonal and HIV-specific responses. However, CMV response in immunodiscordant participants was significantly different from immunoconcordant or HIV-seronegative individuals. In immunodiscordant subjects, the magnitude of IFN-γ⁺ CD8⁺ and IL-2⁺ CD4⁺ T-cells in response to CMV was higher and differently associated with the CD4⁺ T-cell maturation profile., showing an increased frequency of naïve, central memory and EMRA CMV-specific CD4⁺ T-cells. In conclusion, CD4⁺ and CD8⁺ T-cell polyfunctionality was not reduced in immunodiscordant individuals, although heightened CMV-specific immune responses, likely related to subclinical CMV reactivations, may be contributing to the skewed T-cell maturation and the higher risk of clinical progression observed in those individuals.

Designing optimal HIV-vaccine T-cell responses

PURPOSE OF REVIEW

T cells can efficaciously control HIV replication, and it has been hypothesized that inducing those responses before exposure occurs may prevent HIV infection. However, conventional attempts to generate protective CD8 T-cell responses against HIV have generally failed. Based on current knowledge from chronic HIV infection and previous vaccine trials, this review details optimal CD8 and CD4 T-cell response design that may confer protection from HIV infection.

RECENT FINDINGS

The failure of two vaccines geared toward inducing T-cell response (STEP trial and HVTN505/Phambili) as well as the modest protection of the RV144 that mainly demonstrated nonneutralizing antibodies to be a correlate of protection have rattled the idea that a pure T-cell-based vaccine may induce protection. Moreover, in the recent years, CD4 T cells, and in particular the T follicular helper cell subset, received attention as a critical component for T-cell-inducing and antibody-inducing vaccines.

SUMMARY

It is apparent that all vaccines depend for their efficacy on a cellular component either to directly kill virally infected cells or to provide important helper signals for the development of efficacious B-cell responses. Recent vaccine trials have had a major impact on the field and are guiding new approaches for HIV vaccine design.

T-bet-expressing B cells during HIV and HCV infections

T-bet-expressing B cells, first identified as perpetuators of autoimmunity, were recently shown to be critical for murine antiviral responses. While their role in human viral infections remains unclear, B cells expressing T-bet or demonstrating a related phenotype have been described in individuals chronically infected with HIV or HCV, suggesting these cells represent a component of human antiviral responses. In this review, we discuss the induction of T-bet in B cells following both HIV and HCV infections, the factors driving T-bet⁺ B cell expansions, T-bet's relationship to atypical memory B cells, and the consequences of T-bet induction. We propose potential antiviral roles for T-bet⁺ B cells and discuss whether this population poses any utility to the HIV and HCV immune responses.

Divergent Expression of CXCR5 and CCR5 on CD4+ T Cells and the Paradoxical Accumulation of T Follicular Helper Cells during HIV Infection

Viral infection sets in motion a cascade of immune responses, including both CXCR5⁺CD4⁺ T follicular helper (Tfh) cells that regulate humoral immunity and CCR5⁺CD4⁺ T cells that mediate cell-mediated immunity. In peripheral blood mononuclear cells, the majority of memory CD4⁺ T cells appear to fall into either of these two lineages, CCR5⁻CXCR5⁺ or CCR5⁺CXCR5⁻. Very high titers of anti-HIV IgG antibodies are a hallmark of infection, strongly suggesting that there is significant HIV-specific CD4⁺ T cell help to HIV-specific B cells. We now know that characteristic increases in germinal centers (GC) in lymphoid tissue (LT) during SIV and HIV-1 infections are associated with an increase in CXCR5⁺PD-1^high Tfh, which expand to a large proportion of memory CD4⁺ T cells in LT, and are presumably specific for SIV or HIV epitopes. Macaque Tfh normally express very little CCR5, yet are infected by CCR5-using SIV, which may occur mainly through infection of a subset of PD-1^intermediateCCR5⁺Bcl-6⁺ pre-Tfh cells. In contrast, in human LT, a subset of PD-1^high Tfh appears to express low levels of CCR5, as measured by flow cytometry, and this may also contribute to the high rate of infection of Tfh. Also, we have found, by assessing fine-needle biopsies of LT, that increases in Tfh and GC B cells in HIV infection are not completely normalized by antiretroviral therapy (ART), suggesting a possible long-lasting reservoir of infected Tfh. In contrast to the increase of CXCR5⁺ Tfh, there is no accumulation of proliferating CCR5⁺ CD4 T HIV Gag-specific cells in peripheral blood that make IFN-γ. Altogether, CXCR5⁺CCR5⁻ CD4 T cells that regulate humoral immunity are allowed greater freedom to operate and expand during HIV-1 infection, but at the same time can contain HIV DNA at levels at least as high as in other CD4 subsets. We argue that early ART including a CCR5 blocker may directly reduce the infected Tfh reservoir in LT and also interrupt cycles of antibody pressure driving virus mutation and additional GC responses to resulting neoantigens.

Decreased PD-1 Expression on CD8 Lymphocyte Subsets and Increase in CD8 Tscm Cells in Children with HIV Receiving Raltegravir

We investigated the effect of combination antiretroviral therapy (cART) on immune recovery, particularly on the percentages of PD-1-positive cells within the major leukocyte subsets. Cryopreserved peripheral blood mononuclear cells and plasma samples collected longitudinally from a subset of 13 children and adolescents (between 9.7 and 18.2 years old) who were enrolled in the International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) P1066 were used for this study. Immunophenotyping by flow cytometry was performed to determine the effect of raltegravir-containing cART regimen on the distribution of leukocyte populations, on the expression of PD-1 on T cell subpopulations, and on the expression of well-established markers of T cell activation (CD38 and HLA-DR) on CD8 T cells. C reactive protein (CRP), lipopolysaccharide (LPS), IL-6, and soluble CD163 were assayed in plasma samples by an enzyme-linked immunosorbent assay. Plasma viral loads were decreased in all subjects (by an average of 2.9 log units). The cART regimen, including raltegravir, induced changes in CD8 T cell subsets, consistent with an effective antiretroviral outcome and improved immunologic status, including increased percentages of CD8 stem cell memory T cells (Tscm). The percentages of CD8 PD-1-positive cells decreased significantly as compared with baseline levels. Among the proinflammatory markers measured in plasma, sCD163 showed a decline that was associated with cART. cART therapy, including raltegravir, over 48 weeks in children is associated with immune restoration, consistent with effective antiretroviral therapy, namely decreased percentages of PD-1⁺ CD8⁺ T cells, an increase in CD8 Tscm cells, and decreased levels of sCD163.

Preclinical evaluation of an mRNA HIV vaccine combining rationally selected antigenic sequences and adjuvant signals (HTI-TriMix)

BACKGROUND

The development of a prophylactic vaccine against HIV-1 has so far not been successful. Therefore, attention has shifted more and more toward the development of novel therapeutic vaccines. Here, we evaluated a new mRNA-based therapeutic vaccine against HIV-1-encoding activation signals (TriMix: CD40L + CD70 + caTLR4) combined with rationally selected antigenic sequences [HIVACAT T-cell immunogen (HTI)] sequence: comprises 16 joined fragments from Gag, Pol, Vif, and Nef).

METHODS

For this purpose, peripheral blood mononuclear cells from HIV-1-infected individuals on cART, lymph node explants from noninfected humans, and splenocytes from immunized mice were collected and several immune functions were measured.

RESULTS

Electroporation of immature monocyte-derived dendritic cells from HIV-infected patients with mRNA encoding HTI + TriMix potently activated dendritic cells which resulted in upregulation of maturation markers and cytokine production and T-cell stimulation, as evidenced by enhanced proliferation and cytokine secretion (IFN-γ). Responses were HIV specific and were predominantly targeted against the sequences included in HTI. These findings were confirmed in human lymph node explants exposed to HTI + TriMix mRNA. Intranodal immunizations with HTI mRNA in a mouse model increased antigen-specific cytotoxic T-lymphocyte responses. The addition of TriMix further enhanced cytotoxic responses.

CONCLUSION

Our results suggest that uptake of mRNA, encoding strong activation signals and a potent HIV antigen, confers a T-cell stimulatory capacity to dendritic cells and enhances their ability to stimulate antigen-specific immunity. These findings may pave the way for therapeutic HIV vaccine strategies based on antigen-encoding RNA to specifically target antigen-presenting cells.

Physiologically-based modeling to predict the clinical behavior of monoclonal antibodies directed against lymphocyte antigens

Many clinically approved and investigational monoclonal antibody (mAb)-based therapeutics are directed against proteins located in the systemic circulation, including cytokines, growth factors, lymphocyte proteins, and shed antigens. Interaction between mAb and target may lead to non-linear pharmacokinetics (PK), characterized by rapid, target-mediated elimination. Several groups have reported that determinants of target-mediated elimination could include mAb-target binding, target expression, and target turnover. Recently, we scaled a physiologically-based pharmacokinetic model for mAb disposition to man and used it to predict the non-linear PK of mAbs directed against tumor epithelial proteins. In this work, we extended the previously described model to account for the influence of lymphocyte proteins on mAb PK in man. To account for the dynamic behavior of lymphocytes in the circulation, lymphocyte cycling between blood and lymphoid organs was described using first-order transfer rate constants. Use of lymphocyte cycling and reported target turnover rates in the model allowed the accurate prediction of the pharmacokinetics and pharmacodynamics (PD) of 4 mAbs (TRX1, MTRX1011a, rituximab, daclizumab) directed against 3 lymphocyte targets (CD4, CD20, CD25). The results described here suggest that the proposed model structure may be useful in the a priori prediction of the PK/PD properties of mAbs directed against antigens in the circulation.

Effect of Schistosoma mansoni Infection on Innate and HIV-1-Specific T-Cell Immune Responses in HIV-1-Infected Ugandan Fisher Folk

In Uganda, fisher folk have HIV prevalence rates, about four times higher than the national average, and are often coinfected with Schistosoma mansoni. We hypothesized that innate immune responses and HIV-specific Th1 immune responses might be downmodulated in HIV/S. mansoni-coinfected individuals compared with HIV+/S. mansoni-negative individuals. We stimulated whole blood with innate receptor agonists and analyzed supernatant cytokines by Luminex. We evaluated HIV-specific responses by intracellular cytokine staining for IFN-γ, IL-2, and TNF-α. We found that the plasma viral load and CD4 count were similar between the HIV+SM+ and HIV+SM− individuals. In addition, the TNF-α response to the imidazoquinoline compound CL097 and β-1, 3-glucan (curdlan), was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. The frequency of HIV-specific IFN-γ+IL-2–TNF-α− CD8 T cells and IFN-γ+IL-2–TNF-α+ CD4 T cells was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. These findings do not support the hypothesis that S. mansoni downmodulates innate or HIV-specific Th1 responses in HIV/S. mansoni-coinfected individuals.

Effective Cytotoxic T Lymphocyte Targeting of Persistent HIV-1 during Antiretroviral Therapy Requires Priming of Naive CD8+ T Cells

Curing HIV-1 infection will require elimination of persistent cellular reservoirs that harbor latent virus in the face of combination antiretroviral therapy (cART). Proposed immunotherapeutic strategies to cure HIV-1 infection include enhancing lysis of these infected cells by cytotoxic T lymphocytes (CTL). A major challenge in this strategy is overcoming viral immune escape variants that have evaded host immune control. Here we report that naive CD8⁺ T cells from chronic HIV-1-infected participants on long-term cART can be primed by dendritic cells (DC). These DC must be mature, produce high levels of interleukin 12p70 (IL-12p70), be responsive to CD40 ligand (CD40L), and be loaded with inactivated, autologous HIV-1. These DC-primed CD8⁺ T cell responders produced high levels of gamma interferon (IFN-γ) in response to a broad range of both conserved and variable regions of Gag and effectively killed CD4⁺ T cell targets that were either infected with the autologous latent reservoir-associated virus or loaded with autologous Gag peptides. In contrast, HIV-1-specific memory CD8⁺ T cells stimulated with autologous HIV-1-loaded DC produced IFN-γ in response to a narrow range of conserved and variable Gag peptides compared to the primed T cells and most notably, displayed significantly lower cytolytic function. Our findings highlight the need to selectively induce new HIV-1-specific CTL from naive precursors while avoiding activation of existing, dysfunctional memory T cells in potential curative immunotherapeutic strategies for HIV-1 infection.

Current immunotherapeutic approaches aim to enhance antiviral immunity against the HIV-1 reservoir; however, it has yet to be shown whether T cells from persons on cART can recognize and eliminate virus-infected cells. We show that in persons on cART a personalized medicine approach using their dendritic cells to stimulate their naive T cells induces potent effector CTL in vitro that recognize and eradicate HIV-1-infected CD4⁺ T cells. Additionally, we show that the same stimulation of existing memory T cells results in cytokine secretion but limited effector function. Our study demonstrates that the naive T cell repertoire can recognize persistent HIV-1 during cART and supports immunotherapy strategies for an HIV-1 cure that targets naive T cells, rather than existing, dysfunctional, memory T cells.

HIV-1 Antibody Neutralization Breadth Is Associated with Enhanced HIV-Specific CD4+ T Cell Responses

Antigen-specific CD4(+) T helper cell responses have long been recognized to be a critical component of effective vaccine immunity. CD4(+) T cells are necessary to generate and maintain humoral immune responses by providing help to antigen-specific B cells for the production of antibodies. In HIV infection, CD4(+) T cells are thought to be necessary for the induction of Env-specific broadly neutralizing antibodies. However, few studies have investigated the role of HIV-specific CD4(+) T cells in association with HIV neutralizing antibody activity in vaccination or natural infection settings. Here, we conducted a comprehensive analysis of HIV-specific CD4(+) T cell responses in a cohort of 34 untreated HIV-infected controllers matched for viral load, with and without neutralizing antibody breadth to a panel of viral strains. Our results show that the breadth and magnitude of Gag-specific CD4(+) T cell responses were significantly higher in individuals with neutralizing antibodies than in those without neutralizing antibodies. The breadth of Gag-specific CD4(+) T cell responses was positively correlated with the breadth of neutralizing antibody activity. Furthermore, the breadth and magnitude of gp41-specific, but not gp120-specific, CD4(+) T cell responses were significantly elevated in individuals with neutralizing antibodies. Together, these data suggest that robust Gag-specific CD4(+) T cells and, to a lesser extent, gp41-specific CD4(+) T cells may provide important intermolecular help to Env-specific B cells that promote the generation or maintenance of Env-specific neutralizing antibodies.

IMPORTANCE

One of the earliest discoveries related to CD4(+) T cell function was their provision of help to B cells in the development of antibody responses. Yet little is known about the role of CD4(+) T helper responses in the setting of HIV infection, and no studies to date have evaluated the impact of HIV-specific CD4(+) T cells on the generation of antibodies that can neutralize multiple different strains of HIV. Here, we addressed this question by analyzing HIV-specific CD4(+) T cell responses in untreated HIV-infected persons with and without neutralizing antibodies. Our results indicate that HIV-infected persons with neutralizing antibodies have significantly more robust CD4(+) T cell responses targeting Gag and gp41 proteins than individuals who lack neutralizing antibodies. These associations suggest that Gag- and gp41-specific CD4(+) T cell responses may provide robust help to B cells for the generation or maintenance of neutralizing antibodies in natural HIV-infection.

Preserving HIV-specific T cell responses: does timing of antiretroviral therapy help?

PURPOSE OF REVIEW

HIV-specific T cell responses are likely to have an important role in HIV cure strategies that aim for long-lasting viral control without antiretroviral therapy (ART). An important issue in enhancing virus-specific T cell responses is whether timing of ART can influence their magnitude and breadth.

RECENT FINDINGS

Early ART is associated with lower T cell activation, preservation of T cell numbers, smaller DNA and RNA reservoir size, and, in a single study (VISCONTI), control of plasma viremia after treatment interruption. The prevention of T cell destruction by early ART is associated with relatively low anti-HIV CD8⁺ T cell responses but stronger CD4⁺ T helper function. The relatively lower CD8⁺T cell response, which is presumably due to rapid lowering of HIV antigen burden after early ART, appears sufficient to control residual viral replication as well as viral rebound upon treatment interruption.

SUMMARY

Available evidence of starting ART during acute or early HIV infection has shown benefit in both virologic and immunologic parameters despite the lower HIV-specific CD8⁺ T cell responses observed. Encouraging as this is, more extensive data are necessary to evaluate its role in combination with immunotherapeutic and latency activation strategies that are being assessed in various HIV cure-related studies.

Survivin-specific CD4+ T cells are decreased in patients with survivin-positive myeloma

Background

Survivin is a small protein inhibitor of apoptosis and a tumor associated antigen. Survivin expression in multiple myeloma is associated with poor prognosis, disease progression, and drug resistance. The CD4+ response against survivin remains uncharacterized.

Methods

In order to better understand the anti-tumor immune response to survivin, and optimize vaccination strategies, we characterized the spontaneous CD4+CD25- T cell response against survivin in healthy donors and myeloma patients using survivin derived peptide pools.

Results

Healthy donors and myeloma patients’ CD4+CD25- T cells exhibited a proliferative and IFN-gamma response against survivin peptides loaded onto autologous dendritic cells. We employed limiting dilution analysis to quantify the precursor frequency of survivin reactive CD4+CD25- T cells. Multiple myeloma patients (range 0% to 2.2x10^-3%, n=12) had fewer survivin reactive CD4+CD25- T cells than healthy blood donors (range 1.1x10^-3 to 8.4x10^-3%, n=10), p = 0.021. The survivin reactive CD4+CD25- T cell precursor frequency was inversely associated with tumor survivin mRNA expression (p = 0.0028, r = −1.0, n = 6), and survivin tumor protein expression by IHC (p = 0.0295, r = −0.67, n = 10). A full length mutant survivin protein-pulsed dendritic cell vaccine expanded survivin reactive CD4+CD25- T cells after 12 days of in vitro culture (range 0-540x,median = 42x), and expansion was achieved even in patients with low baseline survivin reactive CD4+ precursors.

Conclusions

We have, for the first time, quantified the circulating CD4+CD25- precursor frequency against survivin and demonstrated this is lower in myeloma patients than healthy donors. The number of survivin reactive CD4+CD25- T cells is inversely associated with tumor survivin expression suggesting suppression of survivin responsive CD4+CD25- T cells. Further exploration of a full length mutant survivin protein vaccine which expands survivin reactive CD4+ cells independent of the survivin reactive precursor frequency is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-015-0065-1) contains supplementary material, which is available to authorized users.

Intracellular Cytokine Staining (ICS) on Human Lymphocytes or Peripheral Blood Mononuclear Cells (PBMCs)

Production of cytokines plays an important role in the immune response. Cytokines are involved in many different pathways including the induction of many anti-viral proteins by IFN gamma, the induction of T cell proliferation by IL-2 and the inhibition of viral gene expression and replication by TNF alpha. Cytokines are not preformed factors but are rapidly produced and secreted in response to cellular activation. Intracellular cytokine detection by flow cytometry has emerged as the premier technique for studying cytokine production at the single-cell level. It detects the production and accumulation of cytokines within the endoplasmic reticulum after cell stimulation, allowing direct TH1 versus TH2 determination. It can also be used in combination with other flow cytometry protocols for immunophenotyping using cell surface markers or with MHC multimers to detect an antigen specific response, making it an extremely flexible and versatile method. This capability, combined with the high throughput nature of the instrumentation, gives intracellular cytokine staining an enormous advantage over existing single-cell techniques such as ELISPOT, limiting dilution, and T cell cloning. The principle steps of intracellular cytokine staining is as follows: Cells are activated for a few hours using either a specific peptide or a non-specific activation cocktail; An inhibitor of protein transport (e.g. Brefeldin A) is added to retain the cytokines within the cell; Next, EDTA is added to remove adherent cells from the activation vessel;After washing, antibodies to cell surface markers can be added to the cells;The cells are then fixed in paraformaldehyde and permeabilized;The anti-cytokine antibody is added and the cells can be analyzed by flow cytometer.

Cerebrospinal fluid (CSF) CD8+ T-cells that express interferon-gamma contribute to HIV associated neurocognitive disorders (HAND)

Background

HIV associated neurocognitive disorders (HAND) continue to affect cognition and everyday functioning despite anti-retroviral treatment (ART). Previous studies focused on mechanisms related to monocyte/macrophage mediated inflammation. However, in the ART era, there is increasing evidence for the involvement of CD8+ T-cells in CNS pathogenesis.

Methods

To investigate the relationship between T-cell responses and neurocognitive impairment (NCI), cerebrospinal fluid (CSF) and peripheral blood CD4+ and CD8+ T-cell intracellular cytokine (IFNγ, IL-2, TNFα) and lytic marker (CD107a) expression were assessed in HIV infected subjects who underwent comprehensive neurocognitive (NC) evaluation and either initiated or changed ART.

Results

Data were collected from 31 participants at 70 visits. The frequency of cytokine expressing T-cells in CSF was significantly higher than in peripheral blood for CD4+T-cells: TNFα, IL-2, IFNγ and CD8+T-cells: IL-2 and IFNγ. Analysis of T-cell activity and NCI as a function of CSF HIV RNA levels suggested a general association between NCI, high CSF CD8+ (but not CD4+T-cell) cytokine expression and CSF HIV RNA <10³ copies/ml (p<0.0001). Specifically, CSF CD8+ T-cell IFNγ expression correlated with severity of NCI (r = 0.57, p = 0.004). Multivariable analyses indicated that CSF CD8+T-cell IFNγ and myeloid activation (CD163) contributed equally and independently to cognitive status and a composite variable produced the strongest correlation with NCI (r = 0.83, p = 0.0001). In contrast, CD8+ cytolytic activity (CD107a expression) was negatively correlated with NCI (p = 0.05) but was dependent on CD4 levels >400/μl and low CSF HIV RNA levels (<10³ copies/ml). In our longitudinal analysis of 16 subjects, higher CSF CD8+IFNγ expression at baseline predicted NC decline at follow-up (p = 0.02). Severity of NCI at follow-up correlated with level of residual HIV RNA in CSF.

Conclusions

Presence of IFNγ expressing CD8+ T-cells, absence of cytolytic CD8+ T-cells, high myeloid activation, and failure of ART to suppress HIV replication in CSF contribute to increased risk of HAND.

Programming T cell Killers for an HIV Cure: Teach the New Dogs New Tricks and Let the Sleeping Dogs Lie

Despite the success of combination antiretroviral therapy (cART), a latent viral reservoir persists in HIV-1-infected persons. Unfortunately, endogenous cytotoxic T lymphocytes (CTLs) are unable to control viral rebound when patients are removed from cART. A "kick and kill" strategy has been proposed to eradicate this reservoir, whereby infected T cells are induced to express viral proteins via latency-inducing drugs followed by their elimination by CTLs. It has yet to be determined if stimulation of existing HIV-1-specific CTL will be sufficient, or if new CTLs should be primed from naïve T cells. In this review, we propose that dendritic cells (DCs), the most potent antigen presenting cells, act as dog trainers and can induce T cells (the dogs) to do magnificent tricks. We propose the hypothesis that an HIV-1 cure will require targeting of naïve T cells and will necessitate "teaching new dogs new tricks" while avoiding activation of potentially dysfunctional endogenous memory CTLs (letting the sleeping dogs lie).

Fundamentals and application of magnetic particles in cell isolation and enrichment: a review

Magnetic sorting using magnetic beads has become a routine methodology for the separation of key cell populations from biological suspensions. Due to the inherent ability of magnets to provide forces at a distance, magnetic cell manipulation is now a standardized process step in numerous processes in tissue engineering, medicine, and in fundamental biological research. Herein we review the current status of magnetic particles to enable isolation and separation of cells, with a strong focus on the fundamental governing physical phenomena, properties and syntheses of magnetic particles and on current applications of magnet-based cell separation in laboratory and clinical settings. We highlight the contribution of cell separation to biomedical research and medicine and detail modern cell-separation methods (both magnetic and non-magnetic). In addition to a review of the current state-of-the-art in magnet-based cell sorting, we discuss current challenges and available opportunities for further research, development and commercialization of magnetic particle-based cell-separation systems.

Multiparameter Flow Cytometric Assays to Quantify Effector and Regulatory T-Cell Function in Multiple Sclerosis

The immune system plays a major pathological and regulatory role in multiple sclerosis (MS) and, therefore, is a focus of extensive research. Animal models of MS have been crucial in understanding the pathological processes in MS and developing certain treatments, however, all crucial aspects of the human disease may not be appropriately modeled. With the exception of detecting oligoclonal bands and IgG synthesis in cerebrospinal fluids of MS patients, there has not been major progress in the development of immunologic tests that can be used for diagnosis of MS. Further, due to the lack of validated immune assays, routine monitoring of the immune system following therapy initiation is not a part of standard patient care in MS. This is critical since immunomodulatory therapies used for MS treatment are not benign and, more importantly, there is a considerable variation in clinical responses in MS patients initiating such therapies. Flow cytometry is a powerful tool that can be used for studying both the phenotype and function of immune cells. The studies described here will demonstrate how flow cytometry can be used to apply current knowledge about the MS immune system to develop a diagnostic laboratory test for the immunologic monitoring of this disease. Importantly, we will also show that the multiparameter flow cytometry based assay developed by us can also be implemented for the immunologic evaluation of therapeutic success in MS patients.

Understanding HIV infection for the design of a therapeutic vaccine. Part I: Epidemiology and pathogenesis of HIV infection

HIV infection leads to a gradual loss CD4+ T lymphocytes comprising immune competence and progression to AIDS. Effective treatment with combined antiretroviral drugs (cART) decreases viral load below detectable levels but is not able to eliminate the virus from the body. The success of cART is frustrated by the requirement of expensive life-long adherence, accumulating drug toxicities and chronic immune activation resulting in increased risk of several non-AIDS disorders, even when viral replication is suppressed. Therefore there is a strong need for therapeutic strategies as an alternative to cART. Immunotherapy, or therapeutic vaccination, aims to increase existing immune responses against HIV or induce de novo immune responses. These immune responses should provide a functional cure by controlling viral replication and preventing disease progression in the absence of cART. The key difficulty in the development of an HIV vaccine is our ignorance of the immune responses that control of viral replication, and thus how these responses can be elicited and how they can be monitored. Part one of this review provides an extensive overview of the (patho-) physiology of HIV infection. It describes the structure and replication cycle of HIV, the epidemiology and pathogenesis of HIV infection and the innate and adaptive immune responses against HIV. Part two of this review discusses therapeutic options for HIV. Prevention modalities and antiretroviral therapy are briefly touched upon, after which an extensive overview on vaccination strategies for HIV is provided, including the choice of immunogens and delivery strategies.

Clinical, immunological and treatment-related factors associated with normalised CD4+/CD8+ T-cell ratio: effect of naïve and memory T-cell subsets

Background

Although effective antiretroviral therapy(ART) increases CD4+ T-cell count, responses to ART vary considerably and only a minority of patients normalise their CD4+/CD8+ ratio. Although retention of naïve CD4+ T-cells is thought to predict better immune responses, relationships between CD4+ and CD8+ T-cell subsets and CD4+/CD8+ ratio have not been well described.

Methods

A cross-sectional study in a cohort of ambulatory HIV+ patients. We used flow cytometry on fresh blood to determine expanded CD4+ and CD8+ T-cell subsets; CD45RO+CD62L+(central memory), CD45RO+CD62L-(effector memory) and CD45RO-CD62L+(naïve) alongside routine T-cell subsets(absolute, percentage CD4+ and CD8+ counts), HIVRNA and collected demographic and treatment data. Relationship between CD4+/CD8+ T-cell ratio and expanded T-cell subsets was determined using linear regression analysis. Results are median[IQR] and regression coefficients unless stated.

Results

We recruited 190 subjects, age 42(36–48) years, 65% male, 65.3% Caucasian, 91% on ART(52.6% on protease inhibitors), 78.4% with HIVRNA<40cps/ml and median ART duration 6.8(2.6–10.2) years. Nadir and current CD4+ counts were 200(112–309) and 465(335–607) cells/mm³ respectively. Median CD4+/CD8+ ratio was 0.6(0.4–1.0), with 26.3% of subjects achieving CD4+/CD8+ ratio>1. Of the expanded CD4+ T-cell subsets, 27.3(18.0–38.3)% were naïve, 36.8(29.0–40.0)% central memory and 27.4(20.0–38.5)% effector memory. Of the CD8+ T-cells subsets, 16.5(10.2–25.5)% were naïve, 19.9(12.7–26.6)% central memory and 41.0(31.8–52.5)% effector memory. In the multivariable adjusted analysis, total cumulative-ART exposure(+0.15,p = 0.007), higher nadir CD4+ count(+0.011,p<0.001) and higher %CD8+ naive T-cells(+0.0085,p<0.001) were associated with higher CD4+/CD8+ ratio, higher absolute CD8+ T-cell(-0.0044,p<0.001) and higher %CD4+ effector memory T-cells(-0.004,p = 0.0036) were associated with lower CD4+/CD8+ ratio. Those with CD4+/CD8+ ratio>1 had significantly higher median %CD8+ naive T-cells; 25.4(14.0–36.0)% versus 14.4(9.4–21.6)%, p<0.0001, but significantly lower absolute CD8+ count; 464(384.5–567) versus 765(603–1084) cells/mm³, p<0.001.

Conclusions

Study suggests important role for naïve CD8+ T-cell populations in normalisation of the immune response to HIV-infection. How these findings relate to persistent immune activation on ART requires further study.

CD4 T-cell activation and reduced regulatory T-cell populations are associated with early development of cataracts among HIV-infected adults in Uganda

BACKGROUND

Cataracts contribute 12% of visual loss among HIV-infected adults in Uganda. Immuno-pathogenesis of cataracts may differ among HIV-infected individuals; thus the need for innovative therapeutic interventions among HIV-infected adults.

METHODS

In a laboratory based case-control study, nested in a clinical/surgical community outreach camp, 50 adults with cataracts eligible for surgery were selected consecutively. HIV testing was done for individuals with unknown HIV sero-status. Peripheral Blood Mononuclear Cells (PBMC) were collected from all HIV-positive-adults-with-cataracts (cases) and HIV-negative-adults-with-cataracts (comparative group) and age-matched HIV-negative and HIV-positive-adults-without-cataracts (comparative group). Treg were measured as CD3+CD4+FoxP3+CD25+(Bright) and immune activation as CD3+CD4+CD38+HALDR+ using a Facs Canto II flowcytometer. Mann Whitney test was used to compare expression among the four groups.

RESULTS

Of 50 adults operated for cataracts, 24 (48%) were female, 25 (50%) were HIV-positive. HIV-positive-individuals had cataracts earlier [median; Inter-quartile Range (IQR); 49 (44-53) years] than HIV-negative [70 (IQR 59-75) years]; p=0.0005. Treg were lower among individuals with cataracts irrespective of HIV status; p=0.001; but comparable among younger HIV-positive and elderly HIV-negative with cataracts; p=0.301. Immune activation levels were comparable among HIV-positive and HIV-negative individuals with cataracts. However, HIV-positive-individuals with cataracts expressed higher levels of immune activation than HIV-positive-individuals without cataracts; p=0.012 and HIV-negative-individuals-with-cataracts expressed higher levels of immune activation that HIV-negative-without-cataracts; p<0.0001.

CONCLUSION

CD4 T-cell activation and reduced regulatory T-cell populations were associated with cataracts among adults aging with HIV. We recommend studies on clinical relevance of immune modulation in the prevention of early development of cataracts among adults aging with HIV in Africa.

Induction of Gag-specific CD4 T cell responses during acute HIV infection is associated with improved viral control

Effector CD4 T cell responses have been shown to be critically involved in the containment and clearance of viral pathogens. However, their involvement in the pathogenesis of HIV infection is less clear, given their additional role as preferred viral targets. We previously demonstrated that the presence of HIV-specific CD4 T cell responses is somewhat associated with HIV control and that specific CD4 T cell functions, such as direct cytolytic activity, can contribute to control of HIV viremia. However, little is known about how the induction of HIV-specific CD4 T cell responses during acute HIV infection influences disease progression and whether responses induced during the early phase of infection are preferentially depleted. We therefore longitudinally assessed, in a cohort of 55 acutely HIV-infected individuals, HIV-specific CD4 T cell responses from acute to chronic infection. Interestingly, we found that the breadth, magnitude, and protein dominance of HIV-specific CD4 T cell responses remained remarkably stable over time. Moreover, we found that the epitopes targeted at a high frequency in acute HIV infection were recognized at the same frequency by HIV-specific CD4 T cells in chronic HIV infection. Interestingly the induction of Gag-specific CD4 T cell responses in acute HIV infection was significantly inversely correlated with viral set point in chronic HIV infection (R = -0.5; P = 0.03), while the cumulative contribution of Env-specific CD4 T cell responses showed the reverse effect. Moreover, individuals with HIV-specific CD4 T cell responses dominantly targeting Gag over Env in acute HIV infection remained off antiretroviral therapy significantly longer (P = 0.03; log rank). Thus, our data suggest that the induction of HIV-specific CD4 T cell responses during acute HIV infection is beneficial overall and does not fuel disease progression.

IMPORTANCE

CD4 T cells are critical for the clearance and control of viral infections. However, HIV preferentially infects HIV-specific CD4 T cells. Thus, their contribution to the control of HIV viremia is uncertain. Here, we study HIV-specific CD4 T cell responses from acute to chronic HIV infection and show that the generation of certain CD4 responses is associated with control rather than disease progression.

Effective T helper cell responses against retroviruses: are all clonotypes equal?

The critical importance of CD4(+) T cells in coordinating innate and adaptive immune responses is evidenced by the susceptibility to various pathogenic and opportunistic infections that arises from primary or acquired CD4(+) T cell immunodeficiency, such as following HIV-1 infection. However, despite the clearly defined roles of cytotoxic CD8(+) T cells and antibodies in host protection from retroviruses, the ability of CD4(+) T cells to exert a similar function remains unclear. Recent studies in various settings have drawn attention to the complexity of the T cell response within and between individuals. Distinct TCR clonotypes within an individual differ substantially in their response to the same epitope. Functionally similar, "public" TCR clonotypes can also dominate the response of different individuals. TCR affinity for antigen directly influences expansion and differentiation of responding T cells, also likely affecting their ultimate protective capacity. With this increasing understanding of the parameters that determine the magnitude and effector type of the T cell response, we are now better equipped to address the protective capacity against retroviruses of CD4(+) T cell clonotypes induced by natural infection or vaccination.

Cycling memory CD4+ T cells in HIV disease have a diverse T cell receptor repertoire and a phenotype consistent with bystander activation

The mechanisms of increased memory CD4+ T cell cycling in HIV disease are incompletely understood but have been linked to antigen stimulation, homeostatic signals, or exposure to microbial products and the inflammatory cytokines that they induce. We examined the phenotype and Vβ family distribution in cycling memory CD4+ T cells among 52 healthy and 59 HIV-positive (HIV+) donors. Cycling memory CD4+ T cells were proportionally more frequent in subjects with HIV infection than in controls, more often expressed CD38 and PD-1, and less frequently expressed OX40 and intracellular CD40L. OX40 expression on memory CD4+ T cells was induced in vitro by anti-CD3, interleukin-2 (IL-2), IL-7, or IL-15 but not by Toll-like receptor ligands. In HIV+ donors, memory CD4+ T cell cycling was directly related to plasma lipopolysaccharide (LPS) levels, to plasma HIV RNA levels, and to memory CD8+ T cell cycling and was inversely related to peripheral blood CD4+ T cell counts but not to the levels of IL-2, IL-7, or IL-15, while in HIV-negative donors, memory CD4+ T cell cycling was related to IL-7 levels and negatively related to the plasma levels of LPS. In both controls and HIV+ donors, cycling memory CD4+ T cells had a broad distribution of Vβ families comparable to that of noncycling cells. Increased memory CD4+ T cell cycling in HIV disease is reflective of generalized immune activation and not driven primarily by cognate peptide stimulation or exposure to common gamma-chain cytokines. This cycling may be a consequence of exposure to microbial products, to plasma viremia, or, otherwise, to proinflammatory cytokines.

IMPORTANCE

This work provides evidence that the increased memory CD4+ T cell cycling in HIV infection is not a result of cognate peptide recognition but, rather, is more likely related to the inflammatory environment of HIV infection.

From GRID to gridlock: the relationship between scientific biomedical breakthroughs and HIV/AIDS policy in the US Congress

INTRODUCTION

From the travel ban on people living with HIV (PLHIV) to resistance to needle exchange programmes, there are many examples where policy responses to HIV/AIDS in the United States seem divorced from behavioural, public health and sociological evidence. At its root, however, the unknowns about HIV/AIDS lie at biomedical science, and scientific researchers have made tremendous progress over the past 30 years of the epidemic by using antiretroviral therapy to increase the life expectancy of PLHIV almost to the same level as non-infected individuals; but a relationship between biomedical science discoveries and congressional responses to HIV/AIDS has not been studied. Using quantitative approaches, we directly examine the hypothesis that progress in HIV/AIDS biomedical science discoveries would have a correlative relationship with congressional response to HIV/AIDS from 1981 to 2010.

METHODS

This study used original data on every bill introduced, hearing held and law passed by the US Congress relating to HIV/AIDS over 30 years (1981-2010). We combined congressional data with the most cited and impactful biomedical research scientific publications over the same time period as a metric of biomedical science breakthroughs. Correlations between congressional policy and biomedical research were then analyzed at the aggregate and individual levels.

RESULTS

Biomedical research advancements helped shape both the level and content of bill sponsorship on HIV/AIDS, but they had no effect on other stages of the legislative process. Examination of the content of bills and biomedical research indicated that science helped transform HIV/AIDS bill sponsorship from a niche concern of liberal Democrats to a bipartisan coalition when Republicans became the majority party. The trade-off for that expansion has been an emphasis on the global epidemic to the detriment of domestic policies and programmes.

CONCLUSIONS

Breakthroughs in biomedical science did associate with the number and types of HIV/AIDS bills introduced in Congress, but that relationship did not extend to the passage of laws or to hearings. When science matters, it cannot be separated from political considerations. An important implication of our work has been the depoliticizing role that science can play. Scientific breakthroughs helped to transform HIV/AIDS policy from a niche of liberal Democrats into bipartisan support for the global fight against the disease.

Microbial translocation, residual viremia and immune senescence in the pathogenesis of HIV-1 infection

The pathophysiological mechanisms that underlie the progression of human immunodeficiency virus-1 (HIV-1) disease to full-blown AIDS are not well understood. Findings suggest that, during HIV-1 infection, plasma lipopolysaccharide (LPS) levels, which are used as an indicator of microbial translocation (MT), are elevated throughout the acute and chronic phases of HIV-1 disease. The translocation of bacterial products through the damaged gastrointestinal barrier into the systemic circulation has been described as a driver of immune activation. In contrast, comorbidities that are associated with HIV-1 infection have been attributed to chronic inflammation and immune system dysfunction secondary to MT or low-level HIV-1 replication in plasma and cell reservoirs. Moreover, accelerated aging is significantly associated with chronic inflammation, immune activation, and immune senescence. In this review, we aimed to investigate the role of inflammation as a pivotal marker in the pathogenesis of HIV-1 disease. We will discuss the key features of chronic inflammation and immune activation that are observed during the natural course of the disease and those features that are detected in cART-modified infection. The review will focus on the following aspects of HIV-1 infection: (1) MT; (2) the role of residual viremia; and (3) “immune senescence” or “inflammaging.” Many questions remain unanswered about the potential mechanisms that are involved in HIV-1 pathogenesis. Further studies are needed to better investigate the mechanisms that underlie immune activation and their correlation with HIV-1 disease progression.

Human Immunodeficiency Virus-Type 1 Specific Cellular Immunity in Chronic Infected Patients on Prolonged Highly Active Antiretroviral Treatment and on Structured Treatment Interruption

We have followed 15 HIV-1 chronically infected patients during prolonged highly active antiretroviral treatment (HAART) and subsequent long term structured treatment interruption (STI). We analyzed Nef, Tat, and p24 specific cellular immunity using IFN-gamma enzyme-linked immunospot assays and T cell proliferation assays. Eight HAART patients showed IFN-gamma responses to at least one antigen, but no positive responses were seen during STI. We observed retained or increased p24 specific IFN-gamma responses in most patients during HAART with viral suppression. These results showed persisting HIV-1 specific cellular immunity during HAART; however, in prolonged STI with viral rebound this immunity declined.

T-cell therapies for HIV

Antiretroviral therapy has improved the quality of life for HIV(+) individuals but efficacy requires strict adherence and treatment is not curative. Recently, the use of T cells as therapeutic agents has been in the spotlight in the settings of post-transplant opportunistic infections and cancer. Whether T-cell therapy can be harnessed for treating HIV remains to be determined but there are a few studies that seek to answer that question. Infusion of ex vivo-expanded HIV-specific T cells showed limited efficacy but no adverse events. Genetically modified T cells expressing CD4 chimeric antigen receptors have recently been shown to have persistence that outperforms chimeric antigen receptors used for cancers. Although the results have not yet been published for many clinical studies using T cells for HIV, preclinical studies and the clinical data that are available highlight the potential for T-cell therapy to decrease or eliminate HIV patients' dependency on antiretroviral therapy.