Delayed differentiation of potent effector CD8+ T cells reducing viremia and reservoir seeding in acute HIV infection

Impact of antiretroviral therapy during acute or early HIV infection on virologic and immunologic outcomes: results from a multinational clinical trial

OBJECTIVE

To assess how antiretroviral therapy (ART) initiation during acute or early HIV infection (AEHI) affects the viral reservoir and host immune responses.

DESIGN

Single-arm trial of ART initiation during AEHI at 30 sites in the Americas, Africa, and Asia.

METHODS

HIV DNA was measured at week 48 of ART in 5 million CD4 + T cells by sensitive qPCR assays targeting HIV gag and pol . Peripheral blood mononuclear cells were stimulated with potential HIV T cell epitope peptide pools consisting of env , gag , nef, and pol peptides and stained for expression of CD3, CD4, CD8, and intracellular cytokines/chemokines.

RESULTS

From 2017 to 2019, 188 participants initiated ART during Fiebig stages I ( n  = 6), II ( n  = 43), III ( n  = 56), IV ( n  = 23), and V ( n  = 60). Median age was 27 years (interquartile range 23-38), 27 (14%) participants were female, and 180 (97%) cisgender. Among 154 virally suppressed participants at week 48, 100% had detectable HIV gag or pol DNA. Participants treated during Fiebig I had the lowest HIV DNA levels ( P  < 0.001). Week 48 HIV DNA mostly did not correlate with concurrent CD4 + or CD8 + T cell HIV-specific immune responses (rho range -0.11 to +0.19, all P  > 0.025). At week 48, the magnitude, but not polyfunctionality, of HIV-specific T cell responses was moderately reduced among participants who initiated ART earliest.

CONCLUSION

Earlier ART initiation during AEHI reduced but did not eliminate the persistence of HIV-infected cells in blood. These findings explain the rapid viral rebound observed after ART cessation in early-treated individuals with undetectable HIV DNA by less sensitive methods.

Recent advances on anti-HIV chimeric antigen receptor-T-cell treatment to provide sustained HIV remission

PURPOSE OF REVIEW

Successful sustained remission of HIV infection has been achieved after CCR5Δ32/Δ32 allogeneic hematopoietic stem cell transplantation for treatment of leukemia in a small cohort of people living with HIV (PLWH). This breakthrough demonstrated that the goal of curing HIV was achievable. However, the high morbidity and mortality associated with bone marrow transplantation limits the routine application of this approach and provides a strong rationale for pursuing alternative strategies for sustained long-term antiretroviral therapy (ART)-free HIV remission. Notably, long-term immune-mediated control of HIV replication observed in elite controllers and posttreatment controllers suggests that potent HIV-specific immune responses could provide sustained ART-free remission in PLWH. The capacity of chimeric antigen receptor (CAR)-T cells engineered to target malignant cells to induce remission and cure in cancer patients made this an attractive approach to provide PLWH with a potent HIV-specific immune response. Here, we review the recent advances in the design and application of anti-HIV CAR-T-cell therapy to provide a functional HIV cure.

RECENT FINDINGS

HIV reservoirs are established days after infection and persist through clonal expansion of infected cells. The continuous interaction between latently infected cells and the immune system shapes the landscape of HIV latency and likely contributes to ART-free viral control in elite controllers. CAR-T cells can exhibit superior antiviral activity as compared with native HIV-specific T cells, particularly because they can be engineered to have multiple HIV specificities, resistance to HIV infection, dual costimulatory signaling, immune checkpoint inhibitors, stem cell derivation, CMV TCR coexpression, and tissue homing ligands. These modifications can significantly improve the capacities of anti-HIV CAR-T cells to prevent viral escape, resist HIV infection, and enhance cytotoxicity, persistence, and tissue penetration. Collectively, these novel modifications of anti-HIV CAR-T cell design have increased their capacity to control HIV infection.

SUMMARY

Anti-HIV CAR-T cells can be engineered to provide potent and sustained in-vitro and in-vivo antiviral function. The combination of anti-HIV CAR-T cells with other immunotherapeutics may contribute to long-term HIV remission in PLWH.

Understanding early HIV-1 rebound dynamics following antiretroviral therapy interruption: The importance of effector cell expansion

Most people living with HIV-1 experience rapid viral rebound once antiretroviral therapy is interrupted; however, a small fraction remain in viral remission for an extended duration. Understanding the factors that determine whether viral rebound is likely after treatment interruption can enable the development of optimal treatment regimens and therapeutic interventions to potentially achieve a functional cure for HIV-1. We built upon the theoretical framework proposed by Conway and Perelson to construct dynamic models of virus-immune interactions to study factors that influence viral rebound dynamics. We evaluated these models using viral load data from 24 individuals following antiretroviral therapy interruption. The best-performing model accurately captures the heterogeneity of viral dynamics and highlights the importance of the effector cell expansion rate. Our results show that post-treatment controllers and non-controllers can be distinguished based on the effector cell expansion rate in our models. Furthermore, these results demonstrate the potential of using dynamic models incorporating an effector cell response to understand early viral rebound dynamics post-antiretroviral therapy interruption.

Immune targeting of HIV-1 reservoir cells: a path to elimination strategies and cure

Successful approaches for eradication or cure of HIV-1 infection are likely to include immunological mechanisms, but remarkably little is known about how human immune responses can recognize and interact with the few HIV-1-infected cells that harbour genome-intact viral DNA, persist long term despite antiretroviral therapy and represent the main barrier to a cure. For a long time regarded as being completely shielded from host immune responses due to viral latency, these cells do, on closer examination with single-cell analytic techniques, display discrete footprints of immune selection, implying that human immune responses may be able to effectively engage and target at least some of these cells. The failure to eliminate rebound-competent virally infected cells in the majority of persons likely reflects the evolution of a highly selected pool of reservoir cells that are effectively camouflaged from immune recognition or rely on sophisticated approaches for resisting immune-mediated killing. Understanding the fine-tuned interplay between host immune responses and viral reservoir cells will help to design improved interventions that exploit the immunological vulnerabilities of HIV-1 reservoir cells.

Understanding early HIV-1 rebound dynamics following antiretroviral therapy interruption: The importance of effector cell expansion

Most people living with HIV-1 experience rapid viral rebound once antiretroviral therapy is interrupted; however, a small fraction remain in viral remission for an extended duration. Understanding the factors that determine whether viral rebound is likely after treatment interruption can enable the development of optimal treatment regimens and therapeutic interventions to potentially achieve a functional cure for HIV-1. We built upon the theoretical framework proposed by Conway and Perelson to construct dynamic models of virus-immune interactions to study factors that influence viral rebound dynamics. We evaluated these models using viral load data from 24 individuals following antiretroviral therapy interruption. The best-performing model accurately captures the heterogeneity of viral dynamics and highlights the importance of the effector cell expansion rate. Our results show that post-treatment controllers and non-controllers can be distinguished based on the effector cell expansion rate in our models. Furthermore, these results demonstrate the potential of using dynamic models incorporating an effector cell response to understand early viral rebound dynamics post-antiretroviral therapy interruption.

Erratum to: Progress Note 2024: Curing HIV; Not in My Lifetime or Just Around the Corner?

[This corrects the article DOI: 10.20411/pai.v8i2.665.].

Cerebrospinal fluid pleocytosis is associated with HIV-1 neuroinvasion during acute infection

OBJECTIVE

HIV-1 invades the brain within days post-transmission. This study quantitated cerebrospinal fluid (CSF) white blood cell count (WBC) and investigated whether it associated with plasma and CSF HIV-1 RNA during untreated acute HIV infection (AHI).

DESIGN

Seventy participants underwent lumbar puncture during Fiebig stages I-V AHI.

METHOD

WBC and HIV-1 RNA with a lower limit of quantification (LLQ) of 80 copies/ml were measured in CSF.

RESULTS

Sixty-nine (99%) participants were men, with a median age of 26. Their blood CD4 + and CD8 + T-cell counts were 335 [interquartile range (IQR) 247-553) and 540 (IQR 357-802) cells/μl, respectively. Forty-five (64%) were in Fiebig stages III-V whereas 25 (36%) were in Feibig stages I-II. Fifty-two (74%) experienced acute retroviral syndrome. Median plasma and CSF HIV-1 RNA were 6.10 (IQR 5.15-6.78) and 3.15 (IQR 1.90-4.11) log 10 copies/ml, respectively. Sixteen (23%) CSF samples had HIV-1 RNA below LLQ. Median CSF WBC was 2.5 (IQR 1-8) cells/μl. CSF pleocytosis (WBC >5) was observed in 33% and was only present in CSF samples with detectable HIV-1 RNA. The frequencies of CSF pleocytosis during Fiebig stages III-V and among CSF samples of higher viral load (>1000 copies/ml) were 42 and 45%, respectively. Pleocytosis independently associated with CSF HIV-1 RNA in multivariate analysis [adjusted coefficient: 0.79, 95% confidence interval (CI) 0.41-1.14), P  < 0.001] and a lower plasma to CSF HIV-1 RNA ratio ( P  < 0.001).

CONCLUSION

CSF pleocytosis was present in one-third of participants with AHI. It associated with higher CSF HIV-1 RNA and a lower plasma to CSF HIV-1 RNA ratio, suggesting a potential association with HIV-1 neuroinvasion.

Progress Note 2024: Curing HIV; Not in My Lifetime or Just Around the Corner?

Once a death sentence, HIV is now considered a manageable chronic disease due to the development of antiretroviral therapy (ART) regimens with minimal toxicity and a high barrier for genetic resistance. While highly effective in arresting AIDS progression and rendering the virus untransmissible in people living with HIV (PLWH) with undetectable viremia (U=U) [1, 2]), ART alone is incapable of eradicating the "reservoir" of resting, latently infected CD4+ T cells from which virus recrudesces upon treatment cessation. As of 2022 estimates, there are 39 million PLWH, of whom 86% are aware of their status and 76% are receiving ART [3]. As of 2017, ART-treated PLWH exhibit near normalized life expectancies without adjustment for socioeconomic differences [4]. Furthermore, there is a global deceleration in the rate of new infections [3] driven by expanded access to pre-exposure prophylaxis (PrEP), HIV testing in vulnerable populations, and by ART treatment [5]. Therefore, despite outstanding issues pertaining to cost and access in developing countries, there is strong enthusiasm that aggressive testing, treatment, and effective viral suppression may be able to halt the ongoing HIV epidemic (ie, UNAIDS' 95-95-95 targets) [6-8]; especially as evidenced by recent encouraging observations in Sydney [9]. Despite these promising efforts to limit further viral transmission, for PLWH, a "cure" remains elusive; whether it be to completely eradicate the viral reservoir (ie, cure) or to induce long-term viral remission in the absence of ART (ie, control; Figure 1). In a previous salon hosted by Pathogens and Immunity in 2016 [10], some researchers were optimistic that a cure was a feasible, scalable goal, albeit with no clear consensus on the best route. So, how are these cure strategies panning out? In this commentary, 8 years later, we will provide a brief overview on recent advances and failures towards identifying determinants of viral persistence and developing a scalable cure for HIV. Based on these observations, and as in the earlier salon, we have asked several prominent HIV cure researchers for their perspectives.

Cohort Profile: The Zurich Primary HIV Infection Study

The Zurich Primary HIV Infection (ZPHI) study is a longitudinal cohort study established in 2002, aiming to study the clinical, epidemiological, and biological characteristics of primary HIV infection. The ZPHI enrolls individuals with documented primary HIV-1 infection. At the baseline and thereafter, the socio-demographic, clinical, and laboratory data are systematically collected, and regular blood sampling is performed for biobanking. By the end of December 2022, 486 people were enrolled, of which 353 were still undergoing active follow-up. Of the 486 participants, 86% had an acute infection, and 14% a recent HIV-1 infection. Men who have sex with men accounted for 74% of the study population. The median time from the estimated date of infection to diagnosis was 32 days. The median time from diagnosis to the initiation of antiretroviral therapy was 11 days, and this has consistently decreased over the last two decades. During the seroconversion phase, 447 (92%) patients reported having symptoms, of which only 73% of the patients were classified as having typical acute retroviral syndrome. The ZPHI study is a well-characterized cohort belonging to the most extensively studied primary HIV infection cohort. Its findings contribute to advancing our understanding of the early stages of HIV infection and pathogenesis, and it is paving the way to further improve HIV translational research and HIV medicine.

Early antiretroviral therapy favors post-treatment SIV control associated with the expansion of enhanced memory CD8+ T-cells

HIV remission can be achieved in some people, called post-treatment HIV controllers, after antiretroviral treatment discontinuation. Treatment initiation close to the time of infection was suggested to favor post-treatment control, but the circumstances and mechanisms leading to this outcome remain unclear. Here we evaluate the impact of early (week 4) vs. late (week 24 post-infection) treatment initiation in SIVmac251-infected male cynomolgus macaques receiving 2 years of therapy before analytical treatment interruption. We show that early treatment strongly promotes post-treatment control, which is not related to a lower frequency of infected cells at treatment interruption. Rather, early treatment favors the development of long-term memory CD8+ T cells with enhanced proliferative and SIV suppressive capacity that are able to mediate a robust secondary-like response upon viral rebound. Our model allows us to formally demonstrate a link between treatment initiation during primary infection and the promotion of post-treatment control and provides results that may guide the development of new immunotherapies for HIV remission.

Epitope-dependent effect of long-term cART on maintenance and recovery of HIV-1-specific CD8+ T cells

IMPORTANCE

HIV-1-specific CD8+ T cells are anticipated to become effector cells for curative treatment using the "shock and kill" approach in people living with HIV-1 (PLWH) under combined antiretroviral therapy (cART). Previous studies demonstrated that the frequency of HIV-1-specific CD8+ T cells is reduced under cART and their functional ability remains impaired. These studies analyzed T-cell responses to a small number of HIV-1 epitopes or overlapping HIV-1 peptides. Therefore, the features of CD8+ T cells specific for HIV-1 epitopes under cART remain only partially clarified. Here, we analyzed CD8+ T cells specific for 63 well-characterized epitopes in 90 PLWH. We demonstrated that CD8+ T cells specific for large numbers of HIV-1 epitopes were maintained in an epitope-dependent fashion under long-term cART and that long-term cART enhanced or restored the ability of HIV-1-specific T cells to proliferate in vitro. This study implies that some HIV-1-specific T cells would be useful as effector cells for curative treatment.

Generating and measuring effective vaccine-elicited HIV-specific CD8 + T cell responses

PURPOSE OF REVIEW

There is growing consensus that eliciting CD8 + T cells in addition to antibodies may be required for an effective HIV vaccine for both prevention and cure. Here, we review key qualities of vaccine-elicited CD8 + T cells as well as major CD8 + T cell-based delivery platforms used in recent HIV vaccine clinical trials.

RECENT FINDINGS

Much progress has been made in improving HIV immunogen design and delivery platforms to optimize CD8 + T cell responses. With regards to viral vectors, recent trials have tested newer chimp and human adenovirus vectors as well as a CMV vector. DNA vaccine immunogenicity has been increased by delivering the vaccines by electroporation and together with adjuvants as well as administering them as part of a heterologous regimen. In preclinical models, self-amplifying RNA vaccines can generate durable tissue-based CD8 + T cells. While it may be beneficial for HIV vaccines to recapitulate the functional and phenotypic features of HIV-specific CD8 + T cells isolated from elite controllers, most of these features are not routinely measured in HIV vaccine clinical trials.

SUMMARY

Identifying a vaccine capable of generating durable T cell responses that target mutationally vulnerable epitopes and that can rapidly intercept infecting or rebounding virus remains a challenge for HIV. Comprehensive assessment of HIV vaccine-elicited CD8 + T cells, as well as comparisons between different vaccine platforms, will be critical to advance our understanding of how to design better CD8 + T cell-based vaccines for HIV.

Metabolic and mitochondrial dysregulation in CD4+ T cells from HIV-positive women on combination anti-retroviral therapy

BACKGROUND

For optimal functionality, immune cells require a robust and adaptable metabolic program that is fueled by dynamic mitochondrial activity. In this study, we investigate the metabolic alterations occurring in immune cells during HIV infection and antiretroviral therapy by analyzing the uptake of metabolic substrates and mitochondrial phenotypes. By delineating changes in immune cell metabolic programming during HIV, we may identify novel potential therapeutic targets to improve anti-viral immune responses.

METHODS

After consent and voluntary participation was confirmed, whole blood was drawn from HIV uninfected women and women with chronic HIV infection on long-term combination antiretroviral therapy (HIV/cART). Peripheral blood mononuclear cells-derived immune cells were directly incubated with different fluorescently tagged metabolites and markers of mitochondrial activity: FITC-2-NBDG (2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose), FITC-BODIPY (4,4-Difluoro-5,7-Dimethyl-4-Bora-3a,4a-Diaza-s-Indacene-3-Hexadecanoic Acid), FITC-MitoTracker Green and APC-MitoTracker Deep Red. The uptake of glucose and fats and the mitochondrial mass and potential were measured using flow cytometry. All values are reported quantitatively as geometric means of fluorescence intensity.

RESULTS

During chronic HIV infection, cellular uptake of glucose increases in HIV+ dendritic cells in particular. CD4+ T cells had the lowest uptake of glucose and fats compared to all other cells regardless of HIV status, while CD8+ T cells took up more fatty acids. Interestingly, despite the lower utilization of glucose and fats in CD4+ T cells, mitochondrial mass increased in HIV+ CD4+ T cells compared to HIV negative CD4+ T-cells. HIV+ CD4+ T cells also had the highest mitochondrial potential.

CONCLUSIONS

Significant disparities in the utilization of substrates by leukocytes during chronic HIV/cART exist. Innate immune cells increased utilization of sugars and fats while adaptive immune cells displayed lower glucose and fat utilization despite having a higher mitochondrial activity. Our findings suggest that cART treated HIV-infected CD4+ T cells be dysfunctional or may prefer alternative fuel sources not included in these studies. This underscores the importance of understanding the metabolic effects of HIV treatment on immune function.

An active HIV reservoir during ART is associated with maintenance of HIV-specific CD8+ T cell magnitude and short-lived differentiation status

Before initiation of antiretroviral therapy (ART), HIV-specific CD8+ T cells are dysfunctional and short lived. To better understand the relationship between the HIV reservoir in CD4+ T cells and the magnitude and differentiation status of HIV-specific CD8+ T cells, we investigated these cells from acute and chronic HIV-infected individuals after 2 years of ART. Although both the HIV reservoir and the CD8+ T cell responses declined significantly after 2 years of ART, sustained HIV-specific CD8+ T cell responses correlated with a greater reduction of integrated HIV provirus. However, the magnitude of CD8+ T cells specific for HIV Gag, Pol, Nef, and Vif proteins positively associated with the active reservoir size during ART, measured as cell-associated RNA. Importantly, high HIV DNA levels strongly associate with maintenance of short-lived HIV-specific CD8+ T cells, regardless of ART initiation time. Our data suggest that the active reservoir maintains HIV-specific CD8+ T cell magnitude but prevents their differentiation into functional cells.

CD8+ cells and small viral reservoirs facilitate post-ART control of SIV replication in M3+ Mauritian cynomolgus macaques initiated on ART two weeks post-infection

Sustainable HIV remission after antiretroviral therapy (ART) withdrawal, or post-treatment control (PTC), remains a top priority for HIV treatment. We observed surprising PTC in an MHC-haplomatched cohort of MHC-M3+ SIVmac239+ Mauritian cynomolgus macaques (MCMs) initiated on ART at two weeks post-infection (wpi). None of the MCMs possessed MHC haplotypes previously associated with SIV control. For six months after ART withdrawal, we observed undetectable or transient viremia in seven of the eight MCMs, despite detecting replication competent SIV using quantitative viral outgrowth assays. In vivo depletion of CD8α+ cells induced rebound in all animals, indicating the observed PTC was mediated, at least in part, by CD8α+ cells. With intact proviral DNA assays, we found that MCMs had significantly smaller viral reservoirs two wpi than a cohort of identically infected rhesus macaques, a population that rarely develops PTC. We found a similarly small viral reservoir among six additional SIV+ MCMs in which ART was initiated at eight wpi, some of whom exhibited viral rebound. These results suggest that an unusually small viral reservoir is a hallmark among SIV+ MCMs. By evaluating immunological differences between MCMs that did and did not rebound, we identified that PTC was associated with a reduced frequency of CD4+ and CD8+ lymphocyte subsets expressing exhaustion markers. Together, these results suggest a combination of small reservoirs and immune-mediated virus suppression contribute to PTC in MCMs. Further, defining the immunologic mechanisms that engender PTC in this model may identify therapeutic targets for inducing durable HIV remission in humans.

Elevated glutamate impedes anti-HIV-1 CD8 + T cell responses in HIV-1-infected individuals on antiretroviral therapy

CD8 + T cells are essential for long-lasting HIV-1 control and have been harnessed to develop therapeutic and preventive approaches for people living with HIV-1 (PLWH). HIV-1 infection induces marked metabolic alterations. However, it is unclear whether these changes affect the anti-HIV function of CD8 + T cells. Here, we show that PLWH exhibit higher levels of plasma glutamate than healthy controls. In PLWH, glutamate levels positively correlate with HIV-1 reservoir and negatively correlate with the anti-HIV function of CD8 + T cells. Single-cell metabolic modeling reveals glutamate metabolism is surprisingly robust in virtual memory CD8 + T cells (TVM). We further confirmed that glutamate inhibits TVM cells function via the mTORC1 pathway in vitro. Our findings reveal an association between metabolic plasticity and CD8 + T cell-mediated HIV control, suggesting that glutamate metabolism can be exploited as a therapeutic target for the reversion of anti-HIV CD8 + T cell function in PLWH.

Recent advances in CD8+ T cell-based immune therapies for HIV cure

Achieving a cure for HIV infection is a global priority. There is substantial evidence supporting a central role for CD8⁺ T cells in the natural control of HIV, suggesting the rationale that these cells may be exploited to achieve remission or cure of this infection. In this work, we review the major challenges for achieving an HIV cure, the models of HIV remission, and the mechanisms of HIV control mediated by CD8⁺ T cells. In addition, we discuss strategies based on this cell population that could be used in the search for an HIV cure. Finally, we analyze the current challenges and perspectives to translate this basic knowledge toward scalable HIV cure strategies.

Autologous neutralizing antibodies increase with early antiretroviral therapy and shape HIV rebound after treatment interruption

Early initiation of antiretroviral therapy (ART) alters viral rebound kinetics after analytic treatment interruption (ATI) and may play a role in promoting HIV-1 remission. Autologous neutralizing antibodies (aNAbs) represent a key adaptive immune response in people living with HIV-1. We aimed to investigate the role of aNAbs in shaping post-ATI HIV-1 rebound variants. We performed single-genome amplification of HIV-1 env from pre-ART and post-ATI plasma samples of 12 individuals who initiated ART early after infection. aNAb activity was quantified using pseudoviruses derived from the most common plasma variant, and the serum dilution that inhibited 50% of viral infections was determined. aNAb responses matured while participants were on suppressive ART, because on-ART plasma and purified immunoglobulin G (IgG) demonstrated improved neutralizing activity against pre-ART HIV-1 strains when compared with pre-ART plasma or purified IgG. Post-ATI aNAb responses exerted selective pressure on the rebounding viruses, because the post-ATI HIV-1 strains were more resistant to post-ATI plasma neutralization compared with the pre-ART virus. Several pre-ATI features distinguished post-treatment controllers from noncontrollers, including an infecting HIV-1 sequence that was more similar to consensus HIV-1 subtype B, more restricted proviral diversity, and a stronger aNAb response. Post-treatment control was also associated with the evolution of distinct N-glycosylation profiles in the HIV-1 envelope. In summary, aNAb responses appeared to mature after early initiation of ART and applied selective pressure on rebounding viruses. The combination of aNAb activity with select HIV-1 sequence and reservoir features identified individuals with a greater chance of post-treatment control.

Primary role of type I interferons for the induction of functionally optimal antigen-specific CD8+ T cells in HIV infection

BACKGROUND

CD8⁺ T cells equipped with a full arsenal of antiviral effector functions are critical for effective immune control of HIV-1. It has nonetheless remained unclear how best to elicit such potent cellular immune responses in the context of immunotherapy or vaccination. HIV-2 has been associated with milder disease manifestations and more commonly elicits functionally replete virus-specific CD8⁺ T cell responses compared with HIV-1. We aimed to learn from this immunological dichotomy and to develop informed strategies that could enhance the induction of robust CD8⁺ T cell responses against HIV-1.

METHODS

We developed an unbiased in vitro system to compare the de novo induction of antigen-specific CD8⁺ T cell responses after exposure to HIV-1 or HIV-2. The functional properties of primed CD8⁺ T cells were assessed using flow cytometry and molecular analyses of gene transcription.

FINDINGS

HIV-2 primed functionally optimal antigen-specific CD8⁺ T cells with enhanced survival properties more effectively than HIV-1. This superior induction process was dependent on type I interferons (IFNs) and could be mimicked via the adjuvant delivery of cyclic GMP-AMP (cGAMP), a known agonist of the stimulator of interferon genes (STING). CD8⁺ T cells elicited in the presence of cGAMP were polyfunctional and highly sensitive to antigen stimulation, even after priming from people living with HIV-1.

INTERPRETATION

HIV-2 primes CD8⁺ T cells with potent antiviral functionality by activating the cyclic GMP-AMP synthase (cGAS)/STING pathway, which results in the production of type I IFNs. This process may be amenable to therapeutic development via the use of cGAMP or other STING agonists to bolster CD8⁺ T cell-mediated immunity against HIV-1.

FUNDING

This work was funded by INSERM, the Institut Curie, and the University of Bordeaux (Senior IdEx Chair) and by grants from Sidaction (17-1-AAE-11097, 17-1-FJC-11199, VIH2016126002, 20-2-AEQ-12822-2, and 22-2-AEQ-13411), the Agence Nationale de la Recherche sur le SIDA (ECTZ36691, ECTZ25472, ECTZ71745, and ECTZ118797), and the Fondation pour la Recherche Médicale (EQ U202103012774). D.A.P. was supported by a Wellcome Trust Senior Investigator Award (100326/Z/12/Z).

Advances in HIV Research Using Mass Cytometry

PURPOSE OF REVIEW

This review describes how advances in CyTOF and high-dimensional analysis methods have furthered our understanding of HIV transmission, pathogenesis, persistence, and immunity.

RECENT FINDINGS

CyTOF has generated important insight on several aspects of HIV biology: (1) the differences between cells permissive to productive vs. latent HIV infection, and the HIV-induced remodeling of infected cells; (2) factors that contribute to the persistence of the long-term HIV reservoir, in both blood and tissues; and (3) the impact of HIV on the immune system, in the context of both uncontrolled and controlled infection. CyTOF and high-dimensional analysis tools have enabled in-depth assessment of specific host antigens remodeled by HIV, and have revealed insights into the features of HIV-infected cells enabling them to survive and persist, and of the immune cells that can respond to and potentially control HIV replication. CyTOF and other related high-dimensional phenotyping approaches remain powerful tools for translational research, and applied HIV to cohort studies can inform on mechanisms of HIV pathogenesis and persistence, and potentially identify biomarkers for viral eradication or control.

Factors associated with post-treatment control of viral load in HIV-infected patients: a systematic review and meta-analysis

OBJECTIVES

This study aimed to investigate the factors associated with maintenance of viral suppression after antiretroviral therapy (ART) discontinuation.

METHODS

Databases were searched for studies published between January 01, 2011, and July 01, 2022, that correlated the time of virus rebound with treatment interruption (TI). The corresponding data were extracted from these studies. A fixed-effects model was used to calculate pooled estimates.

RESULTS

Thirty-one studies were included in this analysis. Results showed that patients who started ART during acute or early infection had longer viral control than those who started ART during chronic infection. It has been reported that some broadly neutralizing HIV-1-specific antibodies can significantly prolong viral inhibition. The study also found that approximately 7.2% of patients achieved post-treatment control (PTC) approximately a year after TI.

CONCLUSION

ART initiation in the acute or early phases can delay viral rebound after TI. Cell-associated HIV RNA and HIV DNA have been difficult to prove as able to predict viral rebound time. Many vaccines and antibodies have also been shown to be effective in prolonging viral control in people without PTC, and more research is needed to develop alternative ART therapies that can effectively inhibit or even eliminate HIV.

Role of CXCR5+ CD8+ T cells in human immunodeficiency virus-1 infection

Human immunodeficiency virus (HIV) infection can be effectively suppressed by life-long administration of combination antiretroviral therapy (cART). However, the viral rebound can occur upon cART cessation due to the long-term presence of HIV reservoirs, posing a considerable barrier to drug-free viral remission. Memory CD4⁺ T cell subsets, especially T follicular helper (T _FH ) cells that reside in B-cell follicles within lymphoid tissues, are regarded as the predominant cellular compartment of the HIV reservoir. Substantial evidence indicates that HIV-specific CD8⁺ T cell-mediated cellular immunity can sustain long-term disease-free and transmission-free HIV control in elite controllers. However, most HIV cure strategies that rely on expanded HIV-specific CD8⁺ T cells for virus control are likely to fail due to cellular exhaustion and T _FH reservoir-specialized anatomical structures that isolate HIV-specific CD8⁺ T cell entry into B-cell follicles. Loss of stem-like memory properties is a key feature of exhaustion. Recent studies have found that CXC chemokine receptor type 5 (CXCR5)-expressing HIV-specific CD8⁺ T cells are memory-like CD8⁺ T cells that can migrate into B-cell follicles to execute inhibition of viral replication. Furthermore, these unique CD8⁺ T cells can respond to immune checkpoint blockade (ICB) therapy. In this review, we discuss the functions of these CD8⁺ T cells as well as the translation of findings into viable HIV treatment and cure strategies.

Long-term antiretroviral therapy initiated in acute HIV infection prevents residual dysfunction of HIV-specific CD8+ T cells

Background

Harnessing CD8⁺ T cell responses is being explored to achieve HIV remission. Although HIV-specific CD8⁺ T cells become dysfunctional without treatment, antiretroviral therapy (ART) partially restores their function. However, the extent of this recovery under long-term ART is less understood.

Methods

We analyzed the differentiation status and function of HIV-specific CD8⁺ T cells after long-term ART initiated in acute or chronic HIV infection ex vivo and upon in vitro recall.

Findings

ART initiation in any stage of acute HIV infection promoted the persistence of long-lived HIV-specific CD8⁺ T cells with high expansion (P<0·0008) and cytotoxic capacity (P=0·02) after in vitro recall, albeit at low cell number (P=0·003). This superior expansion capacity correlated with stemness (r=0·90, P=0·006), measured by TCF-1 expression, similar to functional HIV-specific CD8⁺ T cells found in spontaneous controllers. Importanly, TCF-1 expression in these cells was associated with longer time to viral rebound ranging from 13 to 48 days after ART interruption (r =0·71, P=0·03). In contrast, ART initiation in chronic HIV infection led to more differentiated HIV-specific CD8⁺ T cells lacking stemness properties and exhibiting residual dysfunction upon recall, with reduced proliferation and cytolytic activity.

Interpretation

ART initiation in acute HIV infection preserves functional HIV-specific CD8⁺ T cells, albeit at numbers too low to control viral rebound post-ART. HIV remission strategies may need to boost HIV-specific CD8⁺ T cell numbers and induce stem cell-like properties to reverse the residual dysfunction persisting on ART in people treated after acute infection prior to ART release.

Funding

U.S. National Institutes of Health and U.S. Department of Defense.

Neuropathogenesis of HIV-1: insights from across the spectrum of acute through long-term treated infection

This review outlines the neuropathogenesis of HIV, from initial HIV entry into the central nervous system (CNS) to chronic infection, focusing on key advancements in the last 5 years. Discoveries regarding acute HIV infection reveal timing and mechanisms of early HIV entry and replication in the CNS, early inflammatory responses, and establishment of genetically distinct viral reservoirs in the brain. Recent studies additionally explore how chronic HIV infection is maintained in the CNS, examining how the virus remains in a latent "hidden" state in diverse cells in the brain, and how this leads to sustained pathological inflammatory responses. Despite viral suppression with antiretroviral therapy, HIV can persist and even replicate in the CNS, and associate with ongoing neuropathology including CD8 + T-lymphocyte mediated encephalitis. Crucial investigation to advance our understanding of the immune mechanisms that both control viral infection and lead to pathological consequences in the brain is necessary to develop treatments to optimize long-term neurologic health in people living with HIV.

Limited impact of fingolimod treatment during the initial weeks of ART in SIV-infected rhesus macaques

Antiretroviral therapy (ART) is not curative due to the persistence of a reservoir of HIV-infected cells, particularly in tissues such as lymph nodes, with the potential to cause viral rebound after treatment cessation. In this study, fingolimod (FTY720), a lysophospholipid sphingosine-1-phosphate receptor modulator is administered to SIV-infected rhesus macaques at initiation of ART to block the egress from lymphoid tissues of natural killer and T-cells, thereby promoting proximity between cytolytic cells and infected CD4+ T-cells. When compared with the ART-only controls, FTY720 treatment during the initial weeks of ART induces a profound lymphopenia and increases frequencies of CD8+ T-cells expressing perforin in lymph nodes, but not their killing capacity; FTY720 also increases frequencies of cytolytic NK cells in lymph nodes. This increase of cytolytic cells, however, does not limit measures of viral persistence during ART, including intact proviral genomes. After ART interruption, a subset of animals that initially receives FTY720 displays a modest delay in viral rebound, with reduced plasma viremia and frequencies of infected T follicular helper cells. Further research is needed to optimize the potential utility of FTY720 when coupled with strategies that boost the antiviral function of T-cells in lymphoid tissues.

CCL5-Secreting Virtual Memory CD8+ T Cells Inversely Associate With Viral Reservoir Size in HIV-1-Infected Individuals on Antiretroviral Therapy

Recent studies highlighted that CD8+ T cells are necessary for restraining reservoir in HIV-1-infected individuals who undergo antiretroviral therapy (ART), whereas the underlying cellular and molecular mechanisms remain largely unknown. Here, we enrolled 60 virologically suppressed HIV-1-infected individuals, to assess the correlations of the effector molecules and phenotypic subsets of CD8+ T cells with HIV-1 DNA and cell-associated unspliced RNA (CA usRNA). We found that the levels of HIV-1 DNA and usRNA correlated positively with the percentage of CCL4+CCL5- CD8+ central memory cells (T_CM) while negatively with CCL4-CCL5+ CD8+ terminally differentiated effector memory cells (T_EMRA). Moreover, a virtual memory CD8+ T cell (T_VM) subset was enriched in CCL4-CCL5+ T_EMRA cells and phenotypically distinctive from CCL4+ T_CM subset, supported by single-cell RNA-Seq data. Specifically, T_VM cells showed superior cytotoxicity potentially driven by T-bet and RUNX3, while CCL4+ T_CM subset displayed a suppressive phenotype dominated by JUNB and CREM. In viral inhibition assays, T_VM cells inhibited HIV-1 reactivation more effectively than non-T_VM CD8+ T cells, which was dependent on CCL5 secretion. Our study highlights CCL5-secreting T_VM cells subset as a potential determinant of HIV-1 reservoir size. This might be helpful to design CD8+ T cell-based therapeutic strategies for cure of the disease.

HIV-1 Reservoir Persistence and Decay: Implications for Cure Strategies

PURPOSE OF REVIEW

Despite suppressive antiretroviral therapy (ART), a viral reservoir persists in individuals living with HIV that can reignite systemic replication should treatment be interrupted. Understanding how HIV-1 persists through effective ART is essential to develop cure strategies to induce ART-free virus remission.

RECENT FINDINGS

The HIV-1 reservoir resides in a pool of CD4-expressing cells as a range of viral species, a subset of which is genetically intact. Recent studies suggest that the reservoir on ART is highly dynamic, with expansion and contraction of virus-infected cells over time. Overall, the intact proviral reservoir declines faster than defective viruses, suggesting enhanced immune clearance or cellular turnover. Upon treatment interruption, rebound viruses demonstrate escape from adaptive and innate immune responses, implicating these selective pressures in restriction of virus reactivation. Cure strategies employing immunotherapy are poised to test whether host immune pressure can be augmented to enhance reservoir suppression or clearance. Alternatively, genomic engineering approaches are being applied to directly eliminate intact viruses and shrink the replication-competent virus pool. New evidence suggests host immunity exerts selective pressure on reservoir viruses and clears HIV-1 infected cells over years on ART. Efforts to build on the detectable, but insufficient, reservoir clearance via empiric testing in clinical trials will inform our understanding of mechanisms of viral persistence and the direction of future cure strategies.

Transforming dysfunctional CD8+ T cells into natural controller-like CD8+ T cells: can TCF-1 be the magic wand?

HIV infection results in defective CD8+ T cell functions that are incompletely resolved by antiretroviral therapy (ART) except in natural controllers, who have functional CD8+ T cells associated with viral control. In this issue of the JCI, Perdomo-Celis et al. demonstrated that targeting the Wnt/transcription factor T cell factor 1 (Wnt/TCF-1) pathway in dysfunctional CD8+ T cells led to gains in stemness phenotype, metabolic quiescence, survival potential, response to homeostatic γ-chain cytokines, and antiviral capacities, similar to profiles of functional CD8+ T cells in natural controllers. Although reprogramming might not sufficiently reverse the imprinted dysfunction of CD8+ T cells in HIV infection, these findings outline the Wnt/TCF-1 pathway as a potential target to reprogram dysfunctional CD8+ T cells in efforts to achieve HIV remission.

A cytotoxic-skewed immune set point predicts low neutralizing antibody levels after Zika virus infection

Although generating high neutralizing antibody levels is a key component of protective immunity after acute viral infection or vaccination, little is known about why some individuals generate high versus low neutralizing antibody titers. Here, we leverage the high-dimensional single-cell profiling capacity of mass cytometry to characterize the longitudinal cellular immune response to Zika virus (ZIKV) infection in viremic blood donors in Puerto Rico. During acute ZIKV infection, we identify widely coordinated responses across innate and adaptive immune cell lineages. High frequencies of multiple activated cell types during acute infection are associated with high titers of ZIKV neutralizing antibodies 6 months post-infection, while stable immune features suggesting a cytotoxic-skewed immune set point are associated with low titers. Our study offers insight into the coordination of immune responses and identifies candidate cellular biomarkers that may offer predictive value in vaccine efficacy trials aimed at inducing high levels of antiviral neutralizing antibodies.

Evolving Strategies to Eliminate the CD4 T Cells HIV Viral Reservoir via CAR T Cell Immunotherapy

Although the advent of ART has significantly reduced the morbidity and mortality associated with HIV infection, the stable pool of HIV in latently infected cells requires lifelong treatment adherence, with the cessation of ART resulting in rapid reactivation of the virus and productive HIV infection. Therefore, these few cells containing replication-competent HIV, known as the latent HIV reservoir, act as the main barrier to immune clearance and HIV cure. While several strategies involving HIV silencing or its reactivation in latently infected cells for elimination by immune responses have been explored, exciting cell based immune therapies involving genetically engineered T cells expressing synthetic chimeric receptors (CAR T cells) are highly appealing and promising. CAR T cells, in contrast to endogenous cytotoxic T cells, can function independently of MHC to target HIV-infected cells, are efficacious and have demonstrated acceptable safety profiles and long-term persistence in peripheral blood. In this review, we present a comprehensive picture of the current efforts to target the HIV latent reservoir, with a focus on CAR T cell therapies. We highlight the current challenges and advances in this field, while discussing the importance of novel CAR designs in the efforts to find a HIV cure.

Paradoxically greater persistence of HIV RNA+ cells in lymphoid tissue when ART is initiated in the earliest stage of infection

Starting antiretroviral therapy (ART) in Fiebig 1 acute HIV infection limits the size of viral reservoirs in lymphoid tissues, but does not impact time to virus rebound during a treatment interruption. To better understand why the reduced reservoir size did not increase the time to rebound we measured the frequency and location of HIV RNA⁺ cells in lymph nodes from participants in the RV254 acute infection cohort. HIV RNA⁺ cells were detected more frequently and in greater numbers when ART was initiated in Fiebig 1 compared to later Fiebig stages and were localized to the T-cell zone compared to the B-cell follicle with treatment in later Fiebig stages. Variability of virus production in people treated during acute infection suggests that the balance between virus-producing cells and the immune response to clear infected cells rapidly evolves during the earliest stages of infection.

Clinical Trials Registration: NCT02919306.

Deep Phenotypic Analysis of Blood and Lymphoid T and NK Cells From HIV+ Controllers and ART-Suppressed Individuals

T and natural killer (NK) cells are effector cells with key roles in anti-HIV immunity, including in lymphoid tissues, the major site of HIV persistence. However, little is known about the features of these effector cells from people living with HIV (PLWH), particularly from those who initiated antiretroviral therapy (ART) during acute infection. Our study design was to use 42-parameter CyTOF to conduct deep phenotyping of paired blood- and lymph node (LN)-derived T and NK cells from three groups of HIV+ aviremic individuals: elite controllers (N = 5), and ART-suppressed individuals who had started therapy during chronic (N = 6) vs. acute infection (N = 8), the latter of which is associated with better outcomes. We found that acute-treated individuals are enriched for specific subsets of T and NK cells, including blood-derived CD56-CD16+ NK cells previously associated with HIV control, and LN-derived CD4+ T follicular helper cells with heightened expansion potential. An in-depth comparison of the features of the cells from blood vs. LNs of individuals from our cohort revealed that T cells from blood were more activated than those from LNs. By contrast, LNs were enriched for follicle-homing CXCR5+ CD8+ T cells, which expressed increased levels of inhibitory receptors and markers of survival and proliferation as compared to their CXCR5- counterparts. In addition, a subset of memory-like CD56^brightTCF1+ NK cells was enriched in LNs relative to blood. These results together suggest unique T and NK cell features in acute-treated individuals, and highlight the importance of examining effector cells not only in blood but also the lymphoid tissue compartment, where the reservoir mostly persists, and where these cells take on distinct phenotypic features.

Pre-cART Immune Parameters in People Living With HIV Might Help Predict CD8+ T-Cell Characteristics, Inflammation Levels, and Reservoir Composition After Effective cART

Background

Combined antiretroviral treatment (cART) for HIV infection is highly effective in controlling viral replication. However, it cannot achieve a sterilizing cure. Several strategies have been proposed to achieve a functional cure, some of them based on immune-mediated clearing of persistently infected cells. Here, we aimed at identifying factors related to CD8TC and CD4TC quality before cART initiation that associate with the persistence of CD8TC antiviral response after cART, inflammation levels, and the size of the viral reservoir.

Methods

Samples from 25 persons living with HIV were obtained before and after (15 months) cART initiation. Phenotype and functionality of bulk and HIV-specific T cells were assayed by flow cytometry ex vivo or after expansion in pre-cART or post-cART samples, respectively. Cell-Associated (CA) HIV DNA (total and integrated) and RNA (unspliced [US] and multiple spliced [MS]) were quantitated by real-time PCR on post-cART samples. Post-cART plasma levels of CXCL10 (IP-10), soluble CD14 (sCD14) and soluble CD163 (sCD163) were measured by ELISA.

Results

Pre-cART phenotype of CD8TCs and magnitude and phenotype of HIV-specific response correlated with the phenotype and functionality of CD8TCs post-cART. Moreover, the phenotype of the CD8TCs pre-cART correlated with markers of HIV persistence and inflammation post-cART. Finally, exhaustion and differentiation of CD4TCs pre-cART were associated with the composition of the HIV reservoir post-cART and the level of inflammation.

Conclusions

Overall, this work provides data to help understand and identify parameters that could be used as markers in the development of immune-based functional HIV cure strategies.

Ethical considerations for HIV remission clinical research involving participants diagnosed during acute HIV infection

HIV remission clinical researchers are increasingly seeking study participants who are diagnosed and treated during acute HIV infection—the brief period between infection and the point when the body creates detectable HIV antibodies. This earliest stage of infection is often marked by flu-like illness and may be an especially tumultuous period of confusion, guilt, anger, and uncertainty. Such experiences may present added ethical challenges for HIV research recruitment, participation, and retention. The purpose of this paper is to identify potential ethical challenges associated with involving acutely diagnosed people living with HIV in remission research and considerations for how to mitigate them. We identify three domains of potential ethical concern for clinicians, researchers, and ethics committee members to consider: 1) Recruitment and informed consent; (2) Transmission risks and partner protection; and (3) Ancillary and continuing care. We discuss each of these domains with the aim of inspiring further work to advance the ethical conduct of HIV remission research. For example, experiences of confusion and uncertainty regarding illness and diagnosis during acute HIV infection may complicate informed consent procedures in studies that seek to recruit directly after diagnosis. To address this, it may be appropriate to use staged re-consent procedures or comprehension assessment. Responsible conduct of research requires a broad understanding of acute HIV infection that encompasses its biomedical, psychological, social, and behavioral dimensions. We argue that the lived experience of acute HIV infection may introduce ethical concerns that researchers and reviewers should address during study design and ethical approval.

Patterns of pretreatment drug resistance mutations of very early diagnosed and treated infants in Botswana

OBJECTIVE

To describe the occurrence of HIV drug resistance mutations (DRMs) in both intact and defective HIV-1 cell-associated DNA (HIV-1 CAD) among early-treated infants.

DESIGN

The Botswana EIT Study (ClinicalTrials.gov NCT02369406) initiated antiretroviral therapy (ART) in the first week of life and evaluated HIV-1 in plasma and peripheral blood mononuclear cells (PBMCs).

METHODOLOGY

We analyzed 257 near-HIV-1 full-length sequences (nFLS) obtained by Illumina next-generation sequencing from infants near birth. Sanger sequencing of pol was performed for mothers at delivery and children with clinical failure through 96 weeks. DRMs were identified using the Stanford HIV Drug Resistance Database.

RESULTS

In 27 infants, median PBMC HIV-1 proviral load was 492 copies/ml [IQR: 78-1246 copies/ml] at a median of 2 days (range 1-32); 18 (66.7%) had no DRMs detected; six (22.2%) had DRMs detected in defective DNA only, and three (11.1%) had DRMs in both defective and intact DNA (P = 0.09). A total of 60 of 151 (37.7%) defective sequences had at least one DRM: 31.8% NNRTI, 15.2% NRTI, 5.3% protease inhibitor, and 15.5% INSTI-associated mutations. In intact sequences, 33 of 106 (31.1%) had at least 1 DRM: 29.2% NNRTI, 7.5% NRTI, 0.9% protease inhibitor, and no INSTI-associated mutations. For all three infants with intact sequence DRMs, corresponding DRMs occurred in maternal plasma at delivery. Archived DRMs were detectable at a later clinical rebound on only one occasion.

CONCLUSION

Defective HIV-1 cell-associated DNA sequences may overestimate the prevalence of drug resistance among early-treated children. The impact of DRMs from intact proviruses on long-term treatment outcomes warrants further investigation.

Cohort profile: the Netherlands Cohort Study on Acute HIV infection (NOVA), a prospective cohort study of people with acute or early HIV infection who immediately initiate HIV treatment

PURPOSE

Initiation of combination antiretroviral therapy (cART) during acute or early HIV-infection (AEHI) limits the size of the viral reservoir and preserves immune function. This renders individuals who started cART during AEHI promising participants in HIV-cure trials. Therefore, we established a multicentre prospective cohort study in the Netherlands that enrols people with AEHI. In anticipation of future cure trials, we will longitudinally investigate the properties of the viral reservoir size and HIV-specific immune responses among cohort participants.

PARTICIPANTS

Participants immediately initiate intensified cART: dolutegravir, emtricitabine/tenofovir and darunavir/ritonavir (DRV/r). After 4 weeks, once baseline resistance data are available, DRV/r is discontinued. Three study groups are assembled based on the preparedness of individuals to participate in the extensiveness of sampling. Participants accepting immediate treatment and follow-up but declining additional sampling are included in study group 1 ('standard') and routine diagnostic procedures are performed. Participants willing to undergo blood, leukapheresis and semen sampling are included in study group 2 ('less invasive'). In study group 3 ('extended'), additional tissue (gut-associated lymphoid tissue, peripheral lymph node) and cerebrospinal fluid sampling are performed.

FINDINGS TO DATE

Between 2015 and 2020, 140 individuals with AEHI have been enrolled at nine study sites. At enrolment, median age was 36 (IQR 28-47) years, and 134 (95.7%) participants were men. Distribution of Fiebig stages was as follows: Fiebig I, 3 (2.1%); II, 20 (14.3%); III, 7 (5.0%); IV, 49 (35.0%); V, 39 (27.9%); VI, 22 (15.7%). Median plasma HIV RNA was 5.9 (IQR 4.7-6.7) log10 copies/mL and CD4 count 510 (IQR 370-700) cells/mm3. Median time from cART initiation to viral suppression was 8.0 (IQR 4.0-16.0) weeks.

FUTURE PLANS

The Netherlands Cohort Study on Acute HIV infection remains open for participant enrolment and for additional sites to join the network. This cohort provides a unique nationwide platform for conducting future in-depth virological, immunological, host genetic and interventional studies investigating HIV-cure strategies.

Understanding Viral and Immune Interplay During Vertical Transmission of HIV: Implications for Cure

Despite the significant progress that has been made to eliminate vertical HIV infection, more than 150,000 children were infected with HIV in 2019, emphasizing the continued need for sustainable HIV treatment strategies and ideally a cure for children. Mother-to-child-transmission (MTCT) remains the most important route of pediatric HIV acquisition and, in absence of prevention measures, transmission rates range from 15% to 45% via three distinct routes: in utero, intrapartum, and in the postnatal period through breastfeeding. The exact mechanisms and biological basis of these different routes of transmission are not yet fully understood. Some infants escape infection despite significant virus exposure, while others do not, suggesting possible maternal or fetal immune protective factors including the presence of HIV-specific antibodies. Here we summarize the unique aspects of HIV MTCT including the immunopathogenesis of the different routes of transmission, and how transmission in the antenatal or postnatal periods may affect early life immune responses and HIV persistence. A more refined understanding of the complex interaction between viral, maternal, and fetal/infant factors may enhance the pursuit of strategies to achieve an HIV cure for pediatric populations.

Antigen Presenting Cells Contribute to Persistent Immune Activation Despite Antiretroviral Therapy Initiation During Hyperacute HIV-1 Infection

Human immunodeficiency virus (HIV)-induced changes in immune cells during the acute phase of infection can cause irreversible immunological damage and predict the rate of disease progression. Antiretroviral therapy (ART) remains the most effective strategy for successful immune restoration in immunocompromised people living with HIV and the earlier ART is initiated after infection, the better the long-term clinical outcomes. Here we explored the effect of ART on peripheral antigen presenting cell (APC) phenotype and function in women with HIV-1 subtype C infection who initiated ART in the hyperacute phase (before peak viremia) or during chronic infection. Peripheral blood mononuclear cells obtained longitudinally from study participants were used for immunophenotyping and functional analysis of monocytes and dendritic cells (DCs) using multiparametric flow cytometry and matched plasma was used for measurement of inflammatory markers IL-6 and soluble CD14 (sCD14) by enzyme-linked immunosorbent assay. HIV infection was associated with expansion of monocyte and plasmacytoid DC (pDC) frequencies and perturbation of monocyte subsets compared to uninfected persons despite antiretroviral treatment during hyperacute infection. Expression of activation marker CD69 on monocytes and pDCs in early treated HIV was similar to uninfected individuals. However, despite early ART, HIV infection was associated with elevation of plasma IL-6 and sCD14 levels which correlated with monocyte activation. Furthermore, HIV infection with or without early ART was associated with downmodulation of the co-stimulatory molecule CD86. Notably, early ART was associated with preserved toll-like receptor (TLR)-induced IFN-α responses of pDCs. Overall, this data provides evidence of the beneficial impact of ART initiated in hyperacute infection in preservation of APC functional cytokine production activity; but also highlights persistent inflammation facilitated by monocyte activation even after prolonged viral suppression and suggests the need for therapeutic interventions that target residual immune activation.

Viral, inflammatory, and reservoir characteristics of posttreatment controllers

PURPOSE OF REVIEW

To provide an overview of studies to date that have identified posttreatment controllers (PTCs) and to explore current evidence around clinical characteristics, immune effector function, and inflammatory and viral reservoir characteristics that may underlie the control mechanism.

RECENT FINDINGS

PTCs are broadly defined as individuals capable of maintaining control of HIV replication after cessation of antiretroviral therapy (ART). While starting ART early after HIV infection is associated with PTC, genetic disposition or CD8+ T-cell function do not appear to explain this phenomenon, but these features have not been exhaustively analyzed in PTCs. A lower frequency of latently infected cells prior to stopping ART has been associated with achieving PTC, including a lower level of intact HIV DNA, but more studies are needed to map the genetic location, epigenetic characteristics, and tissue distribution of the intact HIV reservoir in PTCs.

SUMMARY

Current studies are small and heterogeneous and there is a significant need to agree on a uniform definition of PTC. Many aspects of PTC are still unexplored including whether specific features of genetic disposition, immune effector functions, and/or viral reservoir characteristics play a role in PTC. A large multisite international cohort study could aide in providing the important insights needed to fully understand PTC.

Concordance of immunological events between intrarectal and intravenous SHIVAD8-EO infection when assessed by Fiebig-equivalent staging

Primary HIV-1 infection can be classified into six Fiebig stages based on virological and serological laboratory testing, whereas simian-HIV (SHIV) infection in nonhuman primates (NHPs) is defined in time post-infection, making it difficult to extrapolate NHP experiments to the clinics. We identified and extensively characterized the Fiebig-equivalent stages in NHPs challenged intrarectally or intravenously with SHIVAD8-EO. During the first month post-challenge, intrarectally challenged monkeys were up to 1 week delayed in progression through stages. However, regardless of the challenge route, stages I-II predominated before, and stages V-VI predominated after, peak viremia. Decrease in lymph node (LN) CD4+ T cell frequency and rise in CD8+ T cells occurred at stage V. LN virus-specific CD8+ T cell responses, dominated by degranulation and TNF, were first detected at stage V and increased at stage VI. A similar late elevation in follicular CXCR5+ CD8+ T cells occurred, consistent with higher plasma CXCL13 levels at these stages. LN SHIVAD8-EO RNA+ cells were present at stage II, but appeared to decline at stage VI when virions accumulated in follicles. Fiebig-equivalent staging of SHIVAD8-EO infection revealed concordance of immunological events between intrarectal and intravenous infection despite different infection progressions, and can inform comparisons of NHP studies with clinical data.

Abundant HIV-infected cells in blood and tissues are rapidly cleared upon ART initiation during acute HIV infection

The timing and location of the establishment of the viral reservoir during acute HIV infection remain unclear. Using longitudinal blood and tissue samples obtained from HIV-infected individuals at the earliest stage of infection, we demonstrate that frequencies of infected cells reach maximal values in gut-associated lymphoid tissue and lymph nodes as early as Fiebig stage II, before seroconversion. Both tissues displayed higher frequencies of infected cells than blood until Fiebig stage III, after which infected cells were equally distributed in all compartments examined. Initiation of antiretroviral therapy (ART) at Fiebig stages I to III led to a profound decrease in the frequency of infected cells to nearly undetectable level in all compartments. The rare infected cells that persisted were preferentially found in the lymphoid tissues. Initiation of ART at later stages (Fiebig stages IV/V and chronic infection) induced only a modest reduction in the frequency of infected cells. Quantification of HIV DNA in memory CD4⁺ T cell subsets confirmed the unstable nature of most of the infected cells at Fiebig stages I to III and the emergence of persistently infected cells during the transition to Fiebig stage IV. Our results indicate that although a large pool of cells is infected during acute HIV infection, most of these early targets are rapidly cleared upon ART initiation. Therefore, infected cells present after peak viremia have a greater ability to persist.

Epigenetic Features of HIV-Induced T-Cell Exhaustion Persist Despite Early Antiretroviral Therapy

T cell dysfunction occurs early following HIV infection, impacting the emergence of non-AIDS morbidities and limiting curative efforts. ART initiated during primary HIV infection (PHI) can reverse this dysfunction, but the extent of recovery is unknown. We studied 66 HIV-infected individuals treated from early PHI with up to three years of ART. Compared with HIV-uninfected controls, CD4 and CD8 T cells from early HIV infection were characterised by T cell activation and increased expression of the immune checkpoint receptors (ICRs) PD1, Tim-3 and TIGIT. Three years of ART lead to partial – but not complete – normalisation of ICR expression, the dynamics of which varied for individual ICRs. For HIV-specific cells, epigenetic profiling of tetramer-sorted CD8 T cells revealed that epigenetic features of exhaustion typically seen in chronic HIV infection were already present early in PHI, and that ART initiation during PHI resulted in only a partial shift of the epigenome to one with more favourable memory characteristics. These findings suggest that although ART initiation during PHI results in significant immune reconstitution, there may be only partial resolution of HIV-related phenotypic and epigenetic changes.

Optimal Maturation of the SIV-Specific CD8+ T Cell Response after Primary Infection Is Associated with Natural Control of SIV: ANRS SIC Study

Highly efficient CD8⁺ T cells are associated with natural HIV control, but it has remained unclear how these cells are generated and maintained. We have used a macaque model of spontaneous SIVmac251 control to monitor the development of efficient CD8⁺ T cell responses. Our results show that SIV-specific CD8⁺ T cells emerge during primary infection in all animals. The ability of CD8⁺ T cells to suppress SIV is suboptimal in the acute phase but increases progressively in controller macaques before the establishment of sustained low-level viremia. Controller macaques develop optimal memory-like SIV-specific CD8⁺ T cells early after infection. In contrast, a persistently skewed differentiation phenotype characterizes memory SIV-specific CD8⁺ T cells in non-controller macaques. Accordingly, the phenotype of SIV-specific CD8⁺ T cells defined early after infection appears to favor the development of protective immunity in controllers, whereas SIV-specific CD8⁺ T cells in non-controllers fail to gain antiviral potency, feasibly as a consequence of early defects imprinted in the memory pool.

Long-term effects of early antiretroviral initiation on HIV reservoir markers: a longitudinal analysis of the MERLIN clinical study

BACKGROUND

Early antiretroviral therapy (ART) initiation (ie, within 3 months of infection) limits establishment of the HIV reservoir. However, the effect of early ART initiation on the long-term dynamics of the pool of infected cells remains unclear.

METHODS

In this longitudinal analysis, we included cisgender men who have sex with men (MSM) and transgender women (aged 18-54 years) at high risk for HIV infection, enrolled in the ongoing longitudinal MERLIN study in Peru between Oct 28, 2014, and Nov 8, 2018. Participants were eligible if they had been infected with HIV less than 90 days before enrolment, and if they had cryopreserved peripheral blood mononuclear cell (PBMC) samples. Participants were stratified into three groups on the basis of whether they initiated ART at 30 days or less (acute group), at 31-90 days (early group), or more than 24 weeks (deferred group) after the estimated date of detectable infection. PBMC samples were collected before ART initiation and longitudinally for up to 4 years on ART. The main outcomes were to establish the size of the HIV reservoir before ART initiation and to assess the effect of the timing of ART initiation on the decay of the HIV reservoir over 4 years follow-up. We quantified viral load, and isolated CD4 cells to quantify total HIV DNA, integrated HIV DNA and 2-long terminal repeat circles. Longitudinal analysis of active and inducible HIV reservoirs were measured by quantifying the frequency of CD4 cells producing multiply-spliced HIV RNA ex vivo and after in-vitro stimulation with a tat/rev induced limiting dilution assay (TILDA). A mixed-effects model from the time of ART initiation was used to measure longitudinal decays in viral loads and each HIV reservoir measure in each of the three groups.

FINDINGS

We included 56 participants in this analysis, all of whom were MSM: 15 were in the acute group, 19 were in the early group, and 22 were in the deferred group. Participants in all three groups had similar levels of all HIV reservoir markers before ART initiation. All participants, including those in the acute group, had a pool of transcriptionally silent HIV-infected cells before ART initiation, as indicated by a substantial increase in TILDA measures upon stimulation. Longitudinal analysis over 4 years of ART revealed a biphasic decay of all HIV persistence markers, with a rapid initial decline followed by a slower decay in all participants. During the first-phase decay, the half-lives of both total and integrated HIV DNA and TILDA measures were significantly shorter in the acute group than in the early and deferred groups. During the second-phase decay, HIV reservoir markers continued to decline only in participants in the acute group.

INTERPRETATION

Participants who initiated ART within 30 days or less of HIV infection showed a steeper and more sustained decay in HIV reservoir measures, suggesting long-term benefit of acute ART initiation on reservoir clearance.

FUNDING

The US National Institutes of Health and the Canadian Institutes for Health Research.

Evolution and Diversity of Immune Responses during Acute HIV Infection

Understanding the earliest immune responses following HIV infection is critical to inform future vaccines and therapeutics. Here, we review recent prospective human studies in at-risk populations that have provided insight into immune responses during acute infection, including additional relevant data from non-human primate (NHP) studies. We discuss the timing, nature, and function of the diverse immune responses induced, the onset of immune dysfunction, and the effects of early anti-retroviral therapy administration. Treatment at onset of viremia mitigates peripheral T and B cell dysfunction, limits seroconversion, and enhances cellular antiviral immunity despite persistence of infection in lymphoid tissues. We highlight pertinent areas for future investigation, and how application of high-throughput technologies, alongside targeted NHP studies, may elucidate immune response features to target in novel preventions and cures.

Clinical and laboratory impact of concomitant syphilis infection during acute HIV

INTRODUCTION

Cognitive impairment has been reported in people living with HIV-1 (PLWH) with prior syphilis, while PLWH who present with incident syphilis have reduced blood CD4 T-lymphocyte and elevated HIV-1 RNA levels. However, the clinical, virological and neurocognitive effects of syphilis during acute HIV-1 (AHI) remain unknown.

METHODS

Pre-antiretroviral therapy laboratory outcomes and neurocognitive performance in a four-test battery in the SEARCH10/RV254 AHI cohort were compared according to syphilis status, determined by serum Treponema pallidum haemagglutination (TPHA), Venereal Disease Research Laboratory (VDRL) and syphilis treatment history. Impaired cognitive performance was defined as having z-scores ≤ -1 in at least two tests or ≤ -2 in at least one test.

RESULTS

Out of 595 AHI participants (97% male, median age of 26 years and estimated duration of HIV-1 infection of 19 days), 119 (20%) had history of syphilis (TPHA-positive), of whom 51 (9%) had untreated syphilis (TPHA-positive/VDRL-positive/without prior treatment). Compared with those without syphilis (TPHA-negative), individuals with untreated syphilis had higher CD8 T-lymphocyte levels but not higher plasma HIV-1 RNA or lower CD4 T-lymphocyte levels. Taking into account estimated duration of HIV-1 infection (P < 0.001), and later Fiebig stages (III-V) (P < 0.001), those with untreated syphilis had higher CD8 T-lymphocyte levels (P = 0.049). Individuals with any syphilis (TPHA-positive), but not untreated syphilis, had higher odds of impaired cognitive performance than those without (P = 0.002).

CONCLUSIONS

During AHI, individuals with any history of syphilis (TPHA-positive) had poorer cognitive performance than those without syphilis. However, syphilis was not associated with worsened HIV disease measures as described in chronic infection.

TCF-1 regulates HIV-specific CD8+ T cell expansion capacity

Although many HIV cure strategies seek to expand HIV-specific CD8+ T cells to control the virus, all are likely to fail if cellular exhaustion is not prevented. A loss in stem-like memory properties (i.e., the ability to proliferate and generate secondary effector cells) is a key feature of exhaustion; little is known, however, about how these properties are regulated in human virus-specific CD8+ T cells. We found that virus-specific CD8+ T cells from humans and nonhuman primates naturally controlling HIV/SIV infection express more of the transcription factor TCF-1 than noncontrollers. HIV-specific CD8+ T cell TCF-1 expression correlated with memory marker expression and expansion capacity and declined with antigenic stimulation. CRISPR-Cas9 editing of TCF-1 in human primary T cells demonstrated a direct role in regulating expansion capacity. Collectively, these data suggest that TCF-1 contributes to the regulation of the stem-like memory property of secondary expansion capacity of HIV-specific CD8+ T cells, and they provide a rationale for exploring the enhancement of this pathway in T cell-based therapeutic strategies for HIV.

Dendritic cells focus CTL responses toward highly conserved and topologically important HIV-1 epitopes

Background

During early HIV-1 infection, immunodominant T cell responses to highly variable epitopes lead to the establishment of immune escape virus variants. Here we assessed a type 1-polarized monocyte-derived dendritic cell (MDC1)-based approach to selectively elicit cytotoxic T lymphocyte (CTL) responses against highly conserved and topologically important HIV-1 epitopes in HIV-1-infected individuals from the Thailand RV254/SEARCH 010 cohort who initiated antiretroviral therapy (ART) during early infection (Fiebig stages I-IV).

Methods

Autologous MDC1 were used as antigen presenting cells to induce in vitro CTL responses against HIV-1 Gag, Pol, Env, and Nef as determined by flow cytometry and ELISpot assay. Ultra-conserved or topologically important antigens were respectively identified using the Epigraph tool and a structure-based network analysis approach and compared to overlapping peptides spanning the Gag proteome.

Findings

MDC1 presenting either the overlapping Gag, Epigraph, or Network 14–21mer peptide pools consistently activated and expanded HIV-1-specific T cells to epitopes identified at the 9–13mer peptide level. Interestingly, some CTL responses occurred outside known or expected HLA associations, providing evidence of new HLA-associated CTL epitopes. Comparative analyses demonstrated more sequence conservation among Epigraph antigens but a higher magnitude of CTL responses to Network and Gag peptide groups. Importantly, CTL responses against topologically constrained Gag epitopes contained in both the Network and Gag peptide pools were selectively enhanced in the Network pool-initiated cultures.

Interpretation

Our study supports the use of MDC1 as a therapeutic strategy to induce and focus CTL responses toward putative fitness-constrained regions of HIV-1 to prevent immune escape and control HIV-1 infection.

Funding

A full list of the funding sources is detailed in the Acknowledgment section of the manuscript.

Non-synonymous Substitutions in HIV-1 GAG Are Frequent in Epitopes Outside the Functionally Conserved Regions and Associated With Subtype Differences

In 2019, 38 million people lived with HIV-1 infection resulting in 690,000 deaths. Over 50% of this infection and its associated deaths occurred in Sub-Saharan Africa. The West African region is a known hotspot of the HIV-1 epidemic. There is a need to develop an HIV-1 vaccine if the HIV epidemic would be effectively controlled. Few protective cytotoxic T Lymphocytes (CTL) epitopes within the HIV-1 GAG (HIV_gagconsv) have been previously identified to be functionally conserved among the HIV-1 M group. These epitopes are currently the focus of universal HIV-1 T cell-based vaccine studies. However, these epitopes' phenotypic and genetic properties have not been observed in natural settings for HIV-1 strains circulating in the West African region. This information is critical as the usefulness of universal HIV-1 vaccines in the West African region depends on these epitopes' occurrence in strains circulating in the area. This study describes non-synonymous substitutions within and without HIV_gagconsv genes isolated from 10 infected Nigerians at the early stages of HIV-1 infection. Furthermore, we analyzed these substitutions longitudinally in five infected individuals from the early stages of infection till after seroconversion. We identified three non-synonymous substitutions within HIV_gagconsv genes isolated from early HIV infected individuals. Fourteen and nineteen mutations outside the HIV_gagconsv were observed before and after seroconversion, respectively, while we found four mutations within the HIV_gagconsv. These substitutions include previously mapped CTL epitope immune escape mutants. CTL immune pressure likely leaves different footprints on HIV-1 GAG epitopes within and outside the HIV_gagconsv. This information is crucial for universal HIV-1 vaccine designs for use in the West African region.

Levels of Human Immunodeficiency Virus DNA Are Determined Before ART Initiation and Linked to CD8 T-Cell Activation and Memory Expansion

Initiation of antiretroviral therapy (ART) in early compared with chronic human immunodeficiency virus (HIV) infection is associated with a smaller HIV reservoir. This longitudinal analysis of 60 individuals who began ART during primary HIV infection (PHI) investigates which pre- and posttherapy factors best predict HIV DNA levels (a correlate of reservoir size) after treatment initiation during PHI. The best predictor of HIV DNA at 1 year was pre-ART HIV DNA, which was in turn significantly associated with CD8 memory T-cell differentiation (effector memory, naive, and T-bet⁻Eomes⁻ subsets), CD8 T-cell activation (CD38 expression) and T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) expression on memory T cells. No associations were found for any immunological variables after 1 year of ART. Levels of HIV DNA are determined around the time of ART initiation in individuals treated during PHI. CD8 T-cell activation and memory expansion are linked to HIV DNA levels, suggesting the importance of the initial host-viral interplay in eventual reservoir size.