T cell dynamics in HIV-1 infection

The cGAS-STING pathway in HIV-1 and Mycobacterium tuberculosis coinfection

Mycobacterium tuberculosis (M. tuberculosis) infection is the most common opportunistic infection in human immunodeficiency virus-1 (HIV-1)-infected individuals, and the mutual reinforcement of these two pathogens may accelerate disease progression and lead to rapid mortality. Therefore, HIV-1/M. tuberculosis coinfection is one of the major global public health concerns. HIV-1 infection is the greatest risk factor for M. tuberculosis infection and increases the likelihood of endogenous relapse and exogenous reinfection with M. tuberculosis. Moreover, M. tuberculosis further increases HIV-1 replication and the occurrence of chronic immune activation, accelerating the progression of HIV-1 disease. Exploring the pathogenesis of HIV-1/M. tuberculosis coinfections is essential for the development of novel treatments to reduce the global burden of tuberculosis. Innate immunity, which is the first line of host immune defense, plays a critical role in resisting HIV-1 and M. tuberculosis infections. The role of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway, which is a major DNA-sensing innate immune signaling pathway, in HIV-1 infection and M. tuberculosis infection has been intensively studied. This paper reviews the role of the cGAS-STING signaling pathway in HIV-1 infection and M. tuberculosis infection and discusses the possible role of this pathway in HIV-1/M. tuberculosis coinfection to provide new insight into the pathogenesis of HIV-1/M. tuberculosis coinfection and the development of novel therapeutic strategies.

Role of the CARD8 inflammasome in HIV pathogenesis

Human immunodeficiency virus (HIV) continues to be a significant global health challenge despite decades of research and advances in treatment. Substantial gaps in our understanding of the mechanisms of HIV pathogenesis and the host immune responses still exist. The interaction between HIV and these immune responses is pivotal in the disease progression to acquired immunodeficiency syndrome (AIDS). Recently, the caspase recruitment domain-containing protein 8 (CARD8) inflammasome has emerged as a crucial factor in orchestrating innate immune responses to HIV infection and exerting a substantial impact on viral pathogenesis. CARD8 restricts viral replication by detecting the activity of HIV protease. Conversely, it also contributes to the depletion of CD4+ T cells, a key feature of disease progression towards AIDS. The purpose of this review is to summarize the role of the CARD8 inflammasome in HIV pathogenesis, delving into its mechanisms of action and potential implications for the development of therapeutic strategies.

Help or Hinder: Protein Host Factors That Impact HIV-1 Replication

Interactions between human immunodeficiency virus type 1 (HIV-1) and the host factors or restriction factors of its target cells determine the cell's susceptibility to, and outcome of, infection. Factors intrinsic to the cell are involved at every step of the HIV-1 replication cycle, contributing to productive infection and replication, or severely attenuating the chances of success. Furthermore, factors unique to certain cell types contribute to the differences in infection between these cell types. Understanding the involvement of these factors in HIV-1 infection is a key requirement for the development of anti-HIV-1 therapies. As the list of factors grows, and the dynamic interactions between these factors and the virus are elucidated, comprehensive and up-to-date summaries that recount the knowledge gathered after decades of research are beneficial to the field, displaying what is known so that researchers can build off the groundwork of others to investigate what is unknown. Herein, we aim to provide a review focusing on protein host factors, both well-known and relatively new, that impact HIV-1 replication in a positive or negative manner at each stage of the replication cycle, highlighting factors unique to the various HIV-1 target cell types where appropriate.

Impact of HIV-Related Immune Impairment of Yellow Fever Vaccine Immunogenicity in People Living with HIV-ANRS 12403

The yellow fever (YF) vaccine is one of the safest and most effective vaccines currently available. Still, its administration in people living with HIV (PLWH) is limited due to safety concerns and a lack of consensus regarding decreased immunogenicity and long-lasting protection for this population. The mechanisms associated with impaired YF vaccine immunogenicity in PLWH are not fully understood, but the general immune deregulation during HIV infection may play an important role. To assess if HIV infection impacts YF vaccine immunogenicity and if markers of immune deregulation could predict lower immunogenicity, we evaluated the association of YF neutralization antibody (NAb) titers with the pre-vaccination frequency of activated and exhausted T cells, levels of pro-inflammatory cytokines, and frequency of T cells, B cells, and monocyte subsets in PLWH and HIV-negative controls. We observed impaired YF vaccine immunogenicity in PLWH with lower titers of YF-NAbs 30 days after vaccination, mainly in individuals with CD4 count <350 cells/mm3. At the baseline, those individuals were characterized by having a higher frequency of activated and exhausted T cells and tissue-like memory B cells. Elevated levels of those markers were also observed in individuals with CD4 count between 500 and 350 cells/mm3. We observed a negative correlation between the pre-vaccination level of CD8+ T cell exhaustion and CD4+ T cell activation with YF-NAb titers at D365 and the pre-vaccination level of IP-10 with YF-NAb titers at D30 and D365. Our results emphasize the impact of immune activation, exhaustion, and inflammation in YF vaccine immunogenicity in PLWH.

Inflammation and cytomegalovirus viremia during pregnancy drive sex-differentiated differences in mortality and immune development in HIV-exposed infants

Children who are HIV-exposed but uninfected have increased infectious mortality compared to HIV-unexposed children, raising the possibility of immune abnormalities following exposure to maternal viraemia, immune dysfunction, and co-infections during pregnancy. In a secondary analysis of the SHINE trial in rural Zimbabwe we explored biological pathways underlying infant mortality, and maternal factors shaping immune development in HIV-exposed uninfected infants. Maternal inflammation and cytomegalovirus viraemia were independently associated with infant deaths: mortality doubled for each log10 rise in maternal C-reactive protein (adjusted hazard ratio (aHR) 2.09; 95% CI 1.33-3.27), and increased 1.6-fold for each log10 rise in maternal cytomegalovirus viral load (aHR 1.62; 95% CI 1.11-2.36). In girls, mortality was more strongly associated with maternal C-reactive protein than cytomegalovirus; in boys, mortality was more strongly associated with cytomegalovirus than C-reactive protein. At age one month, HIV-exposed uninfected infants had a distinct immune milieu, characterised by raised soluble CD14 and an altered CD8 + T-cell compartment. Alterations in immunophenotype and systemic inflammation were generally greater in boys than girls. Collectively, these findings show how the pregnancy immune environment in women with HIV underlies mortality and immune development in their offspring in a sex-differentiated manner, and highlights potential new intervention strategies to transform outcomes of HIV-exposed children. ClinicalTrials.gov/NCT01824940.

The CARD8 inflammasome dictates HIV/SIV pathogenesis and disease progression

While CD4+ T cell depletion is key to disease progression in people living with HIV and SIV-infected macaques, the mechanisms underlying this depletion remain incompletely understood, with most cell death involving uninfected cells. In contrast, SIV infection of "natural" hosts such as sooty mangabeys does not cause CD4+ depletion and AIDS despite high-level viremia. Here, we report that the CARD8 inflammasome is activated immediately after HIV entry by the viral protease encapsulated in incoming virions. Sensing of HIV protease activity by CARD8 leads to rapid pyroptosis of quiescent cells without productive infection, while T cell activation abolishes CARD8 function and increases permissiveness to infection. In humanized mice reconstituted with CARD8-deficient cells, CD4+ depletion is delayed despite high viremia. Finally, we discovered loss-of-function mutations in CARD8 from "natural hosts," which may explain the peculiarly non-pathogenic nature of these infections. Our study suggests that CARD8 drives CD4+ T cell depletion during pathogenic HIV/SIV infections.

Estimates of the global burden of non-Hodgkin lymphoma attributable to HIV: a population attributable modeling study

Background

Human immunodeficiency virus (HIV) significantly increases the risk of non-Hodgkin lymphoma (NHL) development, yet the population-level impact on NHL burden is unquantified. We aim to quantify this association and estimate the global burden of HIV-associated NHL.

Methods

In this meta-analysis, we searched five databases (PubMed, EMBASE, Cochrane Library, Web of Science, Scopus) from database inception up to September 13, 2023, identifying cohort, case-control, or cross-sectional studies with an effective control group to assess NHL risk among individuals with HIV infection, with two authors extracting summary data from reports. Global and regional HIV-associated population attributable fraction (PAF) and NHL disease burden were calculated based on the pooled risk ratio (RR). HIV prevalence and NHL incidence were obtained from the Joint United Nations Programme on HIV/AIDS (UNAIDS) and Global Burden of Diseases, Injuries, and Risk Factors Study 2019. Trends in NHL incidence due to HIV were assessed using age-standardised incidence rate (ASIR) and estimated annual percentage change (EAPC). This study was registered with PROSPERO (CRD42023404150).

Findings

Out of 14,929 literature sources, 39 articles met our inclusion criteria. The risk of NHL was significantly increased in the population living with HIV (pooled RR 23.51, 95% CI 17.62-31.37; I2 = 100%, p < 0.0001), without publication bias. Globally, 6.92% (95% CI 2.18%-11.57%) of NHL new cases in 2019 were attributable to HIV infection (30,503, 95% CI 9585-52,209), which marked a more than three-fold increase from 1990 (8340, 95% CI 3346-13,799). The UNAIDS region of Eastern and Southern Africa was the highest affected region, with 44.46% (95% CI 19.62%-58.57%) of NHL new cases attributed to HIV infection. The Eastern Europe and Central Asia region experienced the highest increase in ASIR of NHL due to HIV in the past thirty years, wherein the EAPC was 8.74% (95% CI 7.66%-9.84%), from 2010 to 2019.

Interpretation

People with HIV infection face a significantly increased risk of NHL. Targeted prevention and control policies are especially crucial for countries in Eastern and Southern Africa, Eastern Europe and Central Asia, to achieve the UNAIDS's '90-90-90' Fast-Track targets. Limited studies across diverse regions and heterogeneity between research have hindered precise estimations for specific periods and regions.

Funding

Sichuan Provincial People's Hospital, Chengdu, China; Health Care for Cadres of Sichuan Province, Chengdu, China; Science and Technology Department of Sichuan Province, Chengdu, China.

Host immunity associated with spontaneous suppression of viremia in therapy-naïve young rhesus macaques following neonatal SHIV infection

IMPORTANCE

Despite the advent of highly active anti-retroviral therapy, people are still dying from HIV-related causes, many of whom are children, and a protective vaccine or cure is needed to end the HIV pandemic. Understanding the nature and activation states of immune cell subsets during infection will provide insights into the immunologic milieu associated with viremia suppression that can be harnessed via therapeutic strategies to achieve a functional cure, but these are understudied in pediatric subjects. We evaluated humoral and adaptive host immunity associated with suppression of viremia in rhesus macaques infected soon after birth with a pathogenic SHIV. The results from our study provide insights into the immune cell subsets and functions associated with viremia control in young macaques that may translate to pediatric subjects for the design of future anti-viral strategies in HIV-1-infected infants and children and contribute to an understudied area of HIV-1 pathogenesis in pediatric subjects.

Engineering RNA export for measurement and manipulation of living cells

A system for programmable export of RNA molecules from living cells would enable both non-destructive monitoring of cell dynamics and engineering of cells capable of delivering executable RNA programs to other cells. We developed genetically encoded cellular RNA exporters, inspired by viruses, that efficiently package and secrete cargo RNA molecules from mammalian cells within protective nanoparticles. Exporting and sequencing RNA barcodes enabled non-destructive monitoring of cell population dynamics with clonal resolution. Further, by incorporating fusogens into the nanoparticles, we demonstrated the delivery, expression, and functional activity of exported mRNA in recipient cells. We term these systems COURIER (controlled output and uptake of RNA for interrogation, expression, and regulation). COURIER enables measurement of cell dynamics and establishes a foundation for hybrid cell and gene therapies based on cell-to-cell delivery of RNA.

HIV-1 remission and possible cure in a woman after haplo-cord blood transplant

Previously, two men were cured of HIV-1 through CCR5Δ32 homozygous (CCR5Δ32/Δ32) allogeneic adult stem cell transplant. We report the first remission and possible HIV-1 cure in a mixed-race woman who received a CCR5Δ32/Δ32 haplo-cord transplant (cord blood cells combined with haploidentical stem cells from an adult) to treat acute myeloid leukemia (AML). Peripheral blood chimerism was 100% CCR5Δ32/Δ32 cord blood by week 14 post-transplant and persisted through 4.8 years of follow-up. Immune reconstitution was associated with (1) loss of detectable replication-competent HIV-1 reservoirs, (2) loss of HIV-1-specific immune responses, (3) in vitro resistance to X4 and R5 laboratory variants, including pre-transplant autologous latent reservoir isolates, and (4) 18 months of HIV-1 control with aviremia, off antiretroviral therapy, starting at 37 months post-transplant. CCR5Δ32/Δ32 haplo-cord transplant achieved remission and a possible HIV-1 cure for a person of diverse ancestry, living with HIV-1, who required a stem cell transplant for acute leukemia.

Prolonged experimental CD4+ T-cell depletion does not cause disease progression in SIV-infected African green monkeys

CD4⁺ T-cell depletion is a hallmark of HIV infection, leading to impairment of cellular immunity and opportunistic infections, but its contribution to SIV/HIV-associated gut dysfunction is unknown. Chronically SIV-infected African Green Monkeys (AGMs) partially recover mucosal CD4⁺ T-cells, maintain gut integrity and do not progress to AIDS. Here we assess the impact of prolonged, antibody-mediated CD4 + T-cell depletion on gut integrity and natural history of SIV infection in AGMs. All circulating CD4⁺ T-cells and >90% of mucosal CD4⁺ T-cells are depleted. Plasma viral loads and cell-associated viral RNA in tissues are lower in CD4⁺-cell-depleted animals. CD4⁺-cell-depleted AGMs maintain gut integrity, control immune activation and do not progress to AIDS. We thus conclude that CD4⁺ T-cell depletion is not a determinant of SIV-related gut dysfunction, when gastrointestinal tract epithelial damage and inflammation are absent, suggesting that disease progression and resistance to AIDS are independent of CD4⁺ T-cell restoration in SIVagm-infected AGMs.

Net charge and position 22 of the V3 loop are associated with HIV-1 tropism in recently infected female sex workers in Nairobi, Kenya

Human immunodeficiency virus (HIV) infection affects around 37 million people worldwide, and in Kenya, key populations especially female sex workers (FSW), are thought to play a substantial role in the wider, mostly heterosexual HIV-1 transmission structure. Notably, HIV tropism has been found to correlate with HIV-1 transmission and disease progression in HIV-infected patients. In this study, recently infected FSWs from Nairobi, Kenya, were assessed for HIV tropism and the factors related to it. We used a cross-sectional study design to analyze 76 HIV-1 positive plasma samples obtained from FSWs enrolled in sex worker outreach program clinics in Nairobi between November 2020 and April 2021. The effects of clinical, demographic, and viral genetic characteristics were determined using multivariable logistic regression. HIV-1 subtype A1 accounted for 89.5% of all cases, with a prevalence of CXCR4-tropic viruses of 26.3%. WebPSSMR5X4 and Geno2Pheno [G2P:10-15% false positive rate] showed high concordance of 88%. Subjects infected with CXCR4-tropic viruses had statistically significant lower baseline CD4+T-cell counts than those infected with CCR5-tropic viruses (P = .044). Using multivariable logistic regression and adjusting for potential confounders, we found that net charge, the amino acid at position 22 of the V3 loop, and the geographic location of the subject were associated with tropism. A unit increase in V3 loop's net-charge increased the odds of a virus being CXCR4-tropic by 2.4 times (OR = 2.40, 95%CI = 1.35-5.00, P = .007). Second, amino acid threonine at position 22 of V3 loop increased the odds of a strain being X4 by 55.7 times compared to the alanine which occurred in CCR5-tropic strains (OR = 55.7, 95%CI = 4.04-84.1, P < .003). The Kawangware sex worker outreach program clinic was associated with CXCR4-tropic strains (P = .034), but there was there was no evidence of a distinct CXCR4-tropic transmission cluster. In conclusion, this study revealed a high concordance of WebPSSMR5X4 and Geno2Pheno in predicting HIV tropism. The most striking finding was that amino acid position 22 of the V3 loop is linked to tropism in HIV-1 subtype A1. Additional studies with a large dataset are warranted to confirm our findings.

In Vitro and In Vivo Toxicological Evaluation of Avicennia africana P: Beauv. (Avicenniaceae) Leaf Extract in a Rat Model

Avicennia africana is an important ethnomedicinal plant that has long been used to treat malaria and several other diseases. Despite the plant's antimalarial and other therapeutic properties, there is limited evidence-based data on its potential toxicity. Hence, the purpose of the current study was to assess the safety of A. africana leaf ethanolic extract (AAE). The study was designed to ascertain the cytotoxic effects of the crude extract on red blood cells (RBCs) as well as the acute and subacute toxicity in Wistar albino rats in accordance with Organization for Economic Co-operation and Development (OECD) guidelines "Test No. 423" and CPMW/SWP/1042/99. The pulverized, shade-dried plant leaves were sequentially macerated with 70% ethanol to obtain the crude extract (AAE). The extract's cytotoxic activity (CC50) against the uninfected human red blood cells (RBCs) was determined using the 3-(4,5-Dimethylythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. For the acute toxicity studies, the rats (male and female) were divided randomly into six groups of five rats (n = 5) and dosed orally once with the following dose levels: 100, 300, 1000, 3000, and 5000 mgkg-1, p.o. of the extracted AAE, with the control group receiving only the vehicle. In the repeated dose toxicity studies, the rats (both sexes) were orally administered daily with AAE at 100, 300, and 1000 mgkg-1 for 14 days. Rat body weights were measured, and blood samples were tested for haematological and biochemical markers. Internal organs like the heart, kidney, liver, and spleen were collected, inspected, and weighed, and histological examinations were performed. The median lethal dose (LD50) value is greater than 5000 mgkg-1 body weight, with no significant change in bodyweight or relative organ weight (ROWs) of the extract-treated groups or control group. The extract showed greater cytotoxicity activity (CC50), which was >100 μg/mL, compared to the reference drug (artesunate).The dosage groups of 100 and 300 mgkg-1bwt had neutrophilia and lymphocytopenia (p < 0.05). However, changes in these haematological parameters may not be dose dependent and could be stress related. All the serum biochemical markers studied in rats given AAE did not show any significant change (p > 0.05). Histopathological examination of internal organs of AAE-treated rats did not show any significant abnormalities resulting from the extract treatment compared to the control group. Based on the findings in the present study, the LD50 value of AAE was found to exceed 5000 mgkg-1 in the acute toxicity test, while the no observed adverse effect level (NOAEL) in rats was 1000 mgkg-1 p.o. In the sub-acute toxicity tests. Histopathological analysis revealed no morphological abnormalities in the vital organs.

Causes and outcomes of hepatic fibrosis in persons living with HIV

PURPOSE OF REVIEW

The epidemiology of liver disease in people living with HIV has evolved since the arrival of effective hepatitis C virus (HCV) treatment. Nonalcoholic fatty liver disease (NAFLD) in HIV patients is highly prevalent while hepatitis D, hepatitis E, and occult hepatitis B remain underappreciated. We discuss mechanisms of fibrosis in HIV and review clinical outcomes of HIV-associated liver diseases.

RECENT FINDINGS

HIV-HCV co-infection is receding as a cause of progressive liver disease, but fibrosis biomarkers after HCV treatment remain elevated. Antiretroviral therapy (ART) with anti-hepatitis B virus (HBV) activity promotes stable liver disease, but oversimplifying ART regimens in unrecognized suppressed HBV may lead to activation of HBV. A high prevalence of fibrosis and rapid progression of fibrosis are seen in HIV-associated NAFLD, with visceral fat as a major risk factor. Newer ART such as integrase strand inhibitors may have limited intrinsic hepatoxicity but do increase weight, which may secondarily lead to hepatic steatosis. Promising therapies for HIV-associated NAFLD include tesamorelin and CCR5 blockade agents.

SUMMARY

Our understanding of the natural history and pathogenesis of liver diseases in HIV has advanced and adapted to the changing landscape of liver disease in this population. Future research should evaluate long-term clinical and histological outcomes, prevention strategies, and treatment options to improve morbidity and mortality in HIV-related liver diseases.

Inflammasomes in Human Immunodeficiency Virus Type 1 Infection

Innate immune responses are the host's first line of defense against human immunodeficiency virus type 1 (HIV-1) infection, with pattern recognition receptors detecting viral specific pathogen-associated molecular patterns and initiating antiviral responses. In response to HIV-1 nucleic acids or proteins, some pattern recognition receptors have the ability to assemble a large multiprotein complex called the inflammasome, which triggers pro-inflammatory cytokine release and a form of lytic programmed cell death called pyroptosis. Here, we review our current understanding of the mechanism of the inflammasome in sensing HIV-1 infection. Furthermore, we discuss the contribution of inflammasome activation in HIV-1 pathogenesis as well as potential strategies of targeting inflammasome activation for the treatment of HIV-1 infection.

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 cellular trafficking signal in the SIV envelope protein cytoplasmic domain is strongly selected for in pathogenic infection

The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-based trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting. Despite extensive analysis, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which this signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY), replicates acutely to high levels in pigtail macaques (PTM) but is rapidly controlled. However, we previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion encoding amino acids 734-736 (ΔQTH) that overlaps the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected that generated a new signal for polarized sorting but not endocytosis. This genotype, together with the ΔGY mutation, was conserved in association with high viral loads for several months when introduced into naïve PTMs. For the first time, our findings reveal strong selection pressure for Env endocytosis and particularly for polarized sorting during pathogenic SIV infection in vivo.

Contribution of Sex Differences to HIV Immunology, Pathogenesis, and Cure Approaches

Approximately 38 million people were living with human immunodeficiency virus (HIV) in 2020 and 53% of those infected were female. A variety of virological and immunological sex-associated differences (sexual dimorphism) in HIV infection have been recognized in males versus females. Social, behavioral, and societal influences play an important role in how the HIV pandemic has affected men and women differently. However, biological factors including anatomical, physiologic, hormonal, and genetic differences in sex chromosomes can each contribute to the distinct characteristics of HIV infection observed in males versus females. One striking example of this is the tendency for women to have lower HIV plasma viral loads than their male counterparts early in infection, though both progress to AIDS at similar rates. Sex differences in acquisition of HIV, innate and adaptive anti-HIV immune responses, efficacy/suitability of specific antiretroviral drugs, and viral pathogenesis have all been identified. Sex differences also have the potential to affect viral persistence, latency, and cure approaches. In this brief review, we summarize the major biological male/female sex differences in HIV infection and their importance to viral acquisition, pathogenesis, treatment, and cure efforts.

Anti-CD4 autoantibodies in immunological non-responder people living with HIV: Cause of CD4+ T-cell depletion?

OBJECTIVE

We aimed to evaluate the anti-CD4 IgG role in the poor immune recovery of immunological nonresponder people with HIV (INR).

DESIGN

INR display low CD4+ T-cell increase despite long-term undetectable viremia. Among other factors, autologous anti-CD4 IgG-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells has been proposed to cause CD4+ T-cell depletion.

METHODS

Plasma anti-CD4 IgG levels were quantified and purified by chromatography columns for the subsequent use in a coculture of CD4+ T and NK cells. We analyzed NK cell degranulation markers (CD107a, perforin and granzyme B) and IFN-γ release, and CD4+ T-cell death. Binding affinity of anti-CD4 IgG for CD4+ T cells was also assessed.

RESULTS

A total of 168 individuals were enrolled (INR, 56; immunological responders, 40; treatment-naive, 39; and healthy controls, 33). The highest anti-CD4 IgG levels were found in treatment-naive PWH, followed by participants on treatment. There were no correlations between anti-CD4 IgG levels and CD4+ T-cell counts. In a 15-participant subgroup (naive, immunological responders, and INR), anti-CD4 IgG induced a slight NK-cell expression of degranulation markers and IFN-γ; however, the percentage of CD4+ T-cell death was negligible. Consistently, no significant changes in NK cell polyfunctionality were observed. In addition, purified anti-CD4 IgG showed scarce binding affinity for CD4+ T cells. These results were similar in all analyzed participant groups.

CONCLUSION

Our results suggest that autologous anti-CD4 IgG neither trigger CD4+ T-cell death by ADCC nor are responsible for CD4+ lymphocyte depletion in INR.

VIDEO ABSTRACT

http://links.lww.com/QAD/C518.

Immunogenicity and safety of 4 intramuscular standard-dose and high-dose hepatitis B vaccine in people living with HIV: a randomized, parallel-controlled trial

OBJECTIVES

The immunogenicity of hepatitis B vaccine is unsatisfactory in the people living with HIV (PLHIV). Studies evaluating optimal regimens to enhance immunogenicity have heretofore been inconclusive. The study was to compare the immunogenicity and safety of the four standard-dose and high-dose regimens of hepatitis B vaccine among PLHIV.

METHODS

A randomized, parallel-controlled trial was conducted between May, 2020, and January, 2021. Patients were randomly assigned to receive 3 or 4 doses of 20 or 60 µg of hepatitis B vaccine. Seroconversion rate, high-level response rate, and geometric mean concentration (GMC) of antibody to hepatitis B surface antigen (anti-HBs) at weeks 12 and 28 were the main outcome measures.

RESULTS

At week 28, the seroconversion rate and GMC of anti-HBs in both IM20 × 4 and IM60 × 4 groups were significantly higher than those in the IM20 × 3 group (P < 0.05), and the GMC of anti-HBs was numerically higher in the IM60 × 4 group than that in the IM20 × 4 group.

CONCLUSIONS

In PLHIV, both the four standard-dose and high-dose regimens significantly improved immunogenicity. The GMC of anti-HBs was numerically higher in the IM60 × 4 group than that in the IM20 × 4 group.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NCT03962803).

Impact of Chronic HIV Infection on SARS-CoV-2 Infection, COVID-19 Disease and Vaccines

PURPOSE OF REVIEW

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has developed into a global pandemic that affect the health of hundreds of millions worldwide. In particular, SARS-CoV-2 infection in people with chronic human immune deficiency virus (HIV) infection is of concern, due to their already immunocompromised status. Yet, whether and how the immunological changes brought about by HIV will affect the immune responses against SARS-CoV-2 acute infection and impact the effectiveness of vaccines remain unclear. We discuss the intersection of COVID-19 in HIV-infected individuals.

RECENT FINDINGS

People living with HIV (PLWH) may be at increased risk of severe SARS-CoV-2 mediated disease complication due to functional impairment of the immune system and persistent inflammation, which can be ameliorated by antiretroviral therapy. Importantly, limited data suggest that current approved vaccines may be safe and efficacious in PLWH. To address remaining questions and supplement limited experimental evidence, more studies examining the interplay between HIV and SARS-CoV-2 through their impact on the host immune system are required.

Chlamydia trachomatis Stimulation Enhances HIV-1 Susceptibility through the Modulation of a Member of the Macrophage Inflammatory Proteins

Sexually transmitted infections such as Chlamydia trachomatis can enhance HIV-1 infection. However, the molecular mechanisms modulating the enhancement of HIV-1 infectivity and replication during HIV-1/sexually transmitted infections coinfection remain elusive. In this study, we performed an ex vivo infection of HIV-1 in PBMCs of C. trachomatis‒infected patients and observed a significant increase in HIV-1 p24 levels compared with those in cells from healthy donors. Similarly, C. trachomatis‒stimulated PBMCs from healthy donors showed enhanced susceptibility to HIV-1. C. trachomatis‒stimulated CD4 T cells also harbored more HIV-1 copy numbers. RNA sequencing data revealed the upregulation of CCL3L1/CCL3L3, a paralog of CCL3 in C. trachomatis‒stimulated CD4 T cells infected with HIV-1. Furthermore, an increase in CCL3L1/CCL3L3 expression levels correlated with HIV-1 replication in C. trachomatis‒stimulated cells. However, the addition of exogenous CCL3L1 reduces HIV-1 infection of healthy cells, indicating a dual role of CCL3L1 in HIV-1 infection. Further investigation revealed that a knockout of CCL3L1/CCL3L3 in Jurkat T cells rescued the increased susceptibility of C. trachomatis‒stimulated cells to HIV-1 infection. These results reveal a role for CCL3L1/CCL3L3 in enhancing HIV-1 replication and production and highlight a mechanism for the enhanced susceptibility to HIV-1 among C. trachomatis‒infected patients.

GALT CD4+PD-1hi T follicular helper (Tfh) cells repopulate after anti-retroviral therapy

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by dramatic alterations in the mucosal CD4 T cell compartment. Though viremia is effectively suppressed, and peripheral CD4 T cell numbers recover to near healthy levels after highly active anti-retroviral therapy (HAART), some of the dysfunctional consequences of HIV infection continue to persist during therapy. We hypothesized that CD4 T follicular helper (Tfh) cell deficiencies may play a role in this process. Using the macaque model we show that SIV infection was associated with a significant loss of Tfh cells in the GALT that drain the mesentery lining the gastrointestinal tract (GIT). Loss of Tfh cells significantly correlated with the depletion of the overall memory CD4 T cell compartment; most Tfh cells in the GALT expressed a CD95+CD28+ memory phenotype suggesting that infection of the memory compartment likely drives the loss of GALT Tfh cells during infection. Continuous anti-retroviral therapy (cART) was accompanied by a significant repopulation of Tfh cells in the GALT to levels similar to those of uninfected animals. Repopulating Tfh cells displayed significantly higher capacity to produce IL-21 as compared to SIV infected animals suggesting that cART fully restores Tfh cells that are functionally capable of supporting GC reactions in the GALT.

The role of CD38 in HIV infection

The widely-expressed molecule CD38 is a single-stranded type II transmembrane glycoprotein that is mainly involved in regulating the differentiation and activation state of the cell. CD38 has broad and complex functions, including enzymatic activity, intercellular signal transduction, cell activation, cytokine production, receptor function and adhesion activity, and it plays an important role in the physiological and pathological processes of many diseases. Many studies have shown that CD38 is related to the occurrence and development of HIV infection, and CD38 may regulate its progression through different mechanisms. Therefore, investigating the role of CD38 in HIV infection and the potential signaling pathways that are involved may provide a new perspective on potential treatments for HIV infection. In the present review, the current understanding of the roles CD38 plays in HIV infection are summarized. In addition, the specific role of CD38 in the process of HIV infection of human CD4⁺ T lymphocytes is also discussed.

Brief Report: Heplisav-B Seroprotection in People With HIV: A Single-Center Experience

BACKGROUND

Heplisav-B, a hepatitis B virus (HBV) vaccine with an immunostimulatory adjuvant, was FDA approved in 2017 for adults ≥18 years. In randomized controlled trials, Heplisav-B demonstrated seroprotection rates (SPR) of 90%-95% versus 65%-80% for Engerix-B. No studies have included people with HIV (PWH), and the SPR and its predictors in this population are unknown.

SETTING

Quaternary care center HIV clinic.

METHODS

This retrospective cohort study evaluated PWH aged ≥18 years without current HBV seroprotection (anti-HBV surface antibody level [anti-HBs] <10 mIU/mL) who were administered Heplisav-B. Patients without post-immunization titers were excluded. The primary outcome was the SPR, the proportion of participants with HBV seroprotection at any point after the first vaccination.

RESULTS

Among 64 PWH included, median time to anti-HBs measurement after vaccination was 13 weeks. The median age was 58 years, 81% were men, and 95% had a viral load <200. The SPR was 81% in the entire cohort (and 86% in those without significant non-HIV immunosuppression), 79% in those with no prior HBV vaccination and no anti-HBc positivity, and 84% in those with prior vaccine nonresponse. Lower current and nadir CD4+ counts were associated with progressively lower seroprotection.

CONCLUSION

In the first single-center retrospective study of Heplisav-B in PWH, the SPR compared favorably with the SPR seen among PWH from prior HBV vaccines across key subgroups. Given these findings, Heplisav-B should be considered for expanded use for HBV vaccination in PWH. Further research on the effectiveness of a repeat vaccination series or higher dosing in nonresponders is needed.

Thresholds for post-rebound SHIV control after CCR5 gene-edited autologous hematopoietic cell transplantation

Autologous, CCR5 gene-edited hematopoietic stem and progenitor cell (HSPC) transplantation is a promising strategy for achieving HIV remission. However, only a fraction of HSPCs can be edited ex vivo to provide protection against infection. To project the thresholds of CCR5-edition necessary for HIV remission, we developed a mathematical model that recapitulates blood T cell reconstitution and plasma simian-HIV (SHIV) dynamics from SHIV-1157ipd3N4-infected pig-tailed macaques that underwent autologous transplantation with CCR5 gene editing. The model predicts that viral control can be obtained following analytical treatment interruption (ATI) when: (1) transplanted HSPCs are at least fivefold higher than residual endogenous HSPCs after total body irradiation and (2) the fraction of protected HSPCs in the transplant achieves a threshold (76-94%) sufficient to overcome transplantation-dependent loss of SHIV immunity. Under these conditions, if ATI is withheld until transplanted gene-modified cells engraft and reconstitute to a steady state, spontaneous viral control is projected to occur.

The role of Th17 cells in viral infections

The present review provides an overview of recent advances regarding the function of Th17 cells and their produced cytokines in the progression of viral diseases. Viral infections alone do not lead to virus-induced malignancies, as both genetic and host safety factors are also involved in the occurrence of malignancies. Acquired immune responses, through the differentiation of Th17 cells, form the novel components of the Th17 cell pathway when reacting with viral infections all the way from the beginning to its final stages. As a result, instead of inducing the right immune responses, these events lead to the suppression of the immune system. In fact, the responses from Th17 cells during persistent viral infections causes chronic inflammation through the production of IL-17 and other cytokines which provide a favorable environment for tumor growth and its development. Additionally, during the past decade, these cells have been understood to be involved in tumor progression and metastasis. However, further research is required to understand Th17 cells' immune mechanisms in the vast variety of viral diseases. This review aims to determine the roles and effects of the immune system, especially Th17 cells, in the progression of viral diseases; which can be highly beneficial for the diagnosis and treatment of these infections.

Organized immune cell interactions within tumors sustain a productive T-cell response

Tumor-infiltrating CD8 T cells are associated with improved patient survival and response to immunotherapy in various cancers. Persistent antigen leads to CD8 T-cell exhaustion, where proliferation/self-renewal and killing are divided within distinct subsets of CD8 T cells in the tumor. CD8 T-cell responses in chronic antigen settings must be maintained for long periods of time, suggesting that mechanisms that regulate chronic CD8 T-cell responses may differ from those in acute settings. Currently, factors that regulate the maintenance of stem-like CD8 T cells in the tumor or their differentiation into terminally differentiated cells are unknown. In this review, we discuss the role of dendritic cells in the activation and differentiation of CD8 T-cell subsets within secondary lymphoid tissue and tumors. In addition, we examine changes in CD4 T-cell differentiation in response to chronic antigens and consider how subset-specific mechanisms could assist the stem-like and terminally differentiated CD8 T-cell subsets. Finally, we highlight how tumor-infiltrating CD4 T cells and dendritic cells interact with CD8 T cells within organized lymphoid-like areas in the tumor and propose a CD8 T-cell differentiation model that requires the collaboration of CD4 T cells and dendritic cells. These organized interactions coordinate the anti-tumor response and control disease progression by mechanisms that regulate CD8 T-cell differentiation, which permit the maintenance of an effective balance of stem-like and terminally differentiated CD8 T cells.

HIV Skews a Balanced Mtb-Specific Th17 Response in Latent Tuberculosis Subjects to a Pro-inflammatory Profile Independent of Viral Load

HIV infection predisposes latent tuberculosis-infected (LTBI) subjects to active TB. This study is designed to determine whether HIV infection of LTBI subjects compromises the balanced Mycobacterium tuberculosis (Mtb)-specific T helper 17 (Th17) response of recognized importance in anti-TB immunity. Comparative analysis of Mtb- and cytomegalovirus (CMV)-specific CD4⁺ T cell responses demonstrates a marked dampening of the Mtb-specific CD4⁺ T cell effectors and polyfunctional cells while preserving CMV-specific response. Additionally, HIV skews the Mtb-specific Th17 response in chronic HIV-infected LTBI progressors, but not long-term non-progressors (LTNPs), with preservation of pro-inflammatory interferon (IFN)-γ⁺/interleukin-17⁺ (IL-17⁺) and significant loss of anti-inflammatory IL-10⁺/IL-17⁺ effectors that is restored by anti-retroviral therapy (ART). HIV-driven impairment of Mtb-specific response cannot be attributed to preferential infection as cell-associated HIV DNA and HIV RNA reveal equivalent viral burden in CD4⁺ T cells from different antigen specificities. We therefore propose that beyond HIV-induced loss of Mtb-specific CD4⁺ T cells, the associated dysregulation of Mtb-specific T cell homeostasis can potentially enhance the onset of TB in LTBI subjects.

Insights Into the Pathophysiology of Liver Disease in HCV/HIV: Does it End With HCV Cure?

HCV-HIV coinfected patients exhibit rapid progression of liver damage relative to HCV monoinfected patients. The availability of new directly acting antiviral agents has dramatically improved outcomes for coinfected patients as sustained virologic response rates now exceed 95% and fibrosis-related parameters are improved. Nevertheless, coinfected patients still have a higher mortality risk and more severe hepatocellular carcinoma compared to HCV monoinfected patients, implying the existence of pathways unique to people living with HIV that continue to promote accelerated liver disease. In this article, we review the pathobiology of liver disease in HCV-HIV coinfected patients in the directly acting antiviral era and explore the mechanisms through which HIV itself induces liver damage. Since liver disease is one of the leading causes of non-AIDS-related mortality in HIV-positive patients, enhancing our understanding of HIV-associated fibrotic pathways will remain important for new diagnostic and therapeutic strategies to slow or reverse liver disease progression, even after HCV cure.

'Rinse and Replace': Boosting T Cell Turnover To Reduce HIV-1 Reservoirs

Latent HIV-1 persists indefinitely during antiretroviral therapy (ART) as an integrated silent genome in long-lived memory CD4+ T cells. In untreated infections, immune activation increases the turnover of intrinsically long-lived provirus-containing CD4+ T cells. Those are 'washed out' as a result of their activation, which when coupled to viral protein expression can facilitate local inflammation and recruitment of uninfected cells to activation sites, causing latently infected cells to compete for survival. De novo infection can counter this washout. During ART, inflammation and CD4+ T cell activation wane, resulting in reduced cell turnover and a persistent reservoir. We propose accelerating reservoir washout during ART by triggering sequential waves of polyclonal CD4+ T cell activation while simultaneously enhancing virus protein expression. Reservoir reduction as an adjunct to other therapies might achieve lifelong viral control.

Macrophage targeted nanocarrier delivery systems in HIV therapeutics

INTRODUCTION

Human immunodeficiency virus (HIV) targets and modulates the immune system increasing the risk of other associated infections. Highly active antiretroviral therapy (HAART) has significantly improved AIDS-associated morbidity, but has limitations of adverse effects, frequent dosing regimen leading to medical non-adherence. Drug delivery systems that target HIV reservoirs could potentially reduce dose-dependent toxicity and the duration of treatment. The major cellular HIV reservoirs are macrophages and CD4⁺ T cells with macrophages being responsible for carrying and spreading the virus. The crucial involvement of macrophages in the pathogenesis of HIV infection has led to development of macrophage targeted nanocarrier delivery systems.

AREAS COVERED

Eradication of viral reservoirs like HIV-infected macrophages has emerged to be a fundamental barrier and challenge for complete eradication of HIV from the immune system. Literature reports several macrophage targeted nanocarrier delivery systems developed as either functionalized or non-functionalized formulations such as liposomes, ethosomes, polymeric nanoparticles, dendrimers, and solid lipid nanoparticles showcasing superior efficacy over the conventional antiretroviral delivery systems.

EXPERT OPINION

The development of fixed dose combination of antiretroviral drugs into macrophage targeted delivery systems should factor in the inherent plasticity and heterogeneity of macrophages that is dependent on their microenvironment. A rational selection of nanocarriers will facilitate selectivity and enhanced efficacy of antiretroviral drugs accompanied by reduced dosing and toxicity. Such macrophage targeted delivery systems would positively impact the therapeutic outcomes in the management of HIV infection.

Simulating the entire natural course of HIV infection by extending the basic viral dynamics equations to include declining viral clearance

The basic model of viral dynamics is a relatively simple set of equations describing the most essential features of the host-pathogen interactions. Coupled with data, it has been used extensively and successfully to reproduce and explain the features of the early acute phase of HIV infection and the effects of antiretroviral treatment, as well as to estimate the lifespan of infected cells, viral growth and clearance rates and predict early outcomes under different circumstances. However, it cannot reproduce the entire natural course of untreated HIV infection consistently with constant parameters. Here we show that it is possible to qualitatively reproduce the whole course of untreated HIV infection within the general framework of the basic model by assuming progressively declining viral clearance coupled with viral load. We discuss the interpretation of this model as proof-of-concept that may inspire further research into the role of viral clearance in HIV infection.

Delineation of Homeostatic Immune Signatures Defining Viremic Non-progression in HIV-1 Infection

Viremic non-progressors (VNPs), a distinct group of HIV-1-infected individuals, exhibit no signs of disease progression and maintain persistently elevated CD4+ T cell counts for several years despite high viral replication. Comprehensive characterization of homeostatic cellular immune signatures in VNPs can provide unique insights into mechanisms responsible for coping with viral pathogenesis as well as identifying strategies for immune restoration under clinically relevant settings such as antiretroviral therapy (ART) failure. We report a novel homeostatic signature in VNPs, the preservation of the central memory CD4+ T cell (CD4+ T_CM) compartment. In addition, CD4+ T_CM preservation was supported by ongoing interleukin-7 (IL-7)-mediated thymic repopulation of naive CD4+ T cells leading to intact CD4+ T cell homeostasis in VNPs. Regulatory T cell (Treg) expansion was found to be a function of preserved CD4+ T cell count and CD4+ T cell activation independent of disease status. However, in light of continual depletion of CD4+ T cell count in progressors but not in VNPs, Tregs appear to be involved in lack of disease progression despite high viremia. In addition to these homeostatic mechanisms resisting CD4+ T cell depletion in VNPs, a relative diminution of terminally differentiated effector subset was observed exclusively in these individuals that might ameliorate consequences of high viral replication. VNPs also shared signatures of impaired CD8+ T cell cytotoxic function with progressors evidenced by increased exhaustion (PD-1 upregulation) and CD127 (IL-7Rα) downregulation contributing to persistent viremia. Thus, the homeostatic immune signatures reported in our study suggest a complex multifactorial mechanism accounting for non-progression in VNPs.

Addition of Maraviroc Versus Placebo to Standard Antiretroviral Therapy for Initial Treatment of Advanced HIV Infection: A Randomized Trial

BACKGROUND

Patients diagnosed with advanced HIV infection have a poor prognosis despite initiation of combined antiretroviral therapy (c-ART).

OBJECTIVE

To assess the benefit of adding maraviroc, an antiretroviral drug with immunologic effects, to standard c-ART for patients with advanced disease at HIV diagnosis.

DESIGN

Randomized controlled trial. (ClinicalTrials.gov: NCT01348308).

SETTING

Clinical sites in France (n = 25), Italy (n = 5), and Spain (n = 20).

PARTICIPANTS

416 HIV-positive, antiretroviral-naive adults with CD4 counts less than 0.200 × 109 cells/L and/or a previous AIDS-defining event (ADE).

INTERVENTION

C-ART plus placebo or maraviroc (300 mg twice daily with dose modification) for 72 weeks.

MEASUREMENTS

The primary end point was first occurrence of severe morbidity (new ADE, selected serious infections, serious non-ADE, immune reconstitution inflammatory syndrome, or death). Prespecified secondary outcomes included primary outcome components, biological and pharmacokinetic measures, and adverse events graded 2 or higher.

RESULTS

409 randomly assigned participants (207 in the placebo group and 202 in the maraviroc group) who received more than 1 dose were included in the analysis. During 72 weeks of follow-up, incidence of severe morbidity was 11.1 per 100 person-years in the maraviroc group and 11.2 per 100 person-years in the placebo group (hazard ratio, 0.97 [95% CI, 0.57 to 1.67]). Incidence of adverse events graded 2 or higher was 36.1 versus 41.5 per 100 person-years (incidence rate ratio, 0.87 [CI, 0.65 to 1.15]).

LIMITATIONS

Sixty-four participants discontinued therapy during follow-up. The study was not designed to evaluate time-dependent outcomes or effect modification.

CONCLUSION

Addition of maraviroc to standard c-ART does not improve clinical outcomes of patients initiating therapy for advanced HIV infection.

PRIMARY FUNDING SOURCE

INSERM-ANRS (French National Agency for Research on AIDS).

HIV-1 elite controllers present a high frequency of activated regulatory T and Th17 cells

HIV-1 infection is characterized by generalized deregulation of the immune system, resulting in increased chronic immune activation. However, some individuals called HIV controllers (HICs) present spontaneous control of viral replication and have a more preserved immune system. Among HICs, discordant results have been observed regarding immune activation and the frequency of different T cell subsets, including Treg and Th17 cells. We evaluated T cell immune activation, differentiation and regulatory profiles in two groups of HICs—elite controllers (ECs) and viremic controllers (VCs)—and compared them to those of cART-treated individuals (cART) and HIV-1-negative (HIV-neg) individuals. ECs demonstrated similar levels of activated CD4⁺ and CD8⁺ T cells in comparison to HIV-neg, while cART and VCs showed elevated T cell activation. CD4⁺ T cell subset analyses showed differences only for transitional memory T cell frequency between the EC and HIV-neg groups. However, VC individuals showed higher frequencies of terminally differentiated, naïve, and stem cell memory T cells and lower frequencies of transitional memory and central memory T cells compared to the HIV-neg group. Among CD8⁺ T cell subsets, ECs presented higher frequencies of stem cell memory T cells, while VCs presented higher frequencies of terminally differentiated T cells compared to the HIV-neg group. HICs showed lower frequencies of total Treg cells compared to the HIV-neg and cART groups. ECs also presented higher frequencies of activated and a lower frequency of resting Treg cells than the HIV-neg and cART groups. Furthermore, we observed a high frequency of Th17 cells in ECs and high Th17/Treg ratios in both HIC groups. Our data showed that ECs had low levels of activated T cells and a high frequency of activated Treg and Th17 cells, which could restrict chronic immune activation and be indicative of a preserved mucosal response in these individuals.

Immunological Paradigms, Mechanisms, and Models: Conceptual Understanding Is a Prerequisite to Effective Modeling

Most mathematical models that describe the individual or collective actions of cells aim at creating faithful representations of limited sets of data in a self-consistent manner. Consistency with relevant physiological rules pertaining to the greater picture is rarely imposed. By themselves, such models have limited predictive or even explanatory value, contrary to standard claims. Here I try to show that a more critical examination of currently held paradigms is necessary and could potentially lead to models that pass the test of time. In considering the evolution of paradigms over the past decades I focus on the “smart surveillance” theory of how T cells can respond differentially, individually and collectively, to both self- and foreign antigens depending on various “contextual” parameters. The overall perspective is that physiological messages to cells are encoded not only in the biochemical connections of signaling molecules to the cellular machinery but also in the magnitude, kinetics, and in the time- and space-contingencies, of sets of stimuli. By rationalizing the feasibility of subthreshold interactions, the “dynamic tuning hypothesis,” a central component of the theory, set the ground for further theoretical and experimental explorations of dynamically regulated immune tolerance, homeostasis and diversity, and of the notion that lymphocytes participate in nonclassical physiological functions. Some of these efforts are reviewed. Another focus of this review is the concomitant regulation of immune activation and homeostasis through the operation of a feedback mechanism controlling the balance between renewal and differentiation of activated cells. Different perspectives on the nature and regulation of chronic immune activation in HIV infection have led to conflicting models of HIV pathogenesis—a major area of research for theoretical immunologists over almost three decades—and can have profound impact on ongoing HIV cure strategies. Altogether, this critical review is intended to constructively influence the outlook of prospective model builders and of interested immunologists on the state of the art and to encourage conceptual work.

Long-term evolution of transmitted CXCR4-using HIV-1 under effective antiretroviral therapy

OBJECTIVE

To study the long-term evolution of the transmitted CXCR4-using viruses. CCR5-using viruses (R5 viruses) predominate during primary HIV-1 infections (PHI) while CXCR4-using viruses are isolated in less than 10% of PHI.

DESIGN

Six patients infected with an R5X4 virus, detected by a sensitive phenotypic assay during PHI, were matched with six patients infected with a pure R5 virus for sex, Fiebig stage, time of antiretroviral initiation and duration of follow-up.

METHODS

We used MiSeq ultra-deep sequencing to determine the composition of the virus quasispecies during PHI and at the end of follow-up (median time of follow-up: 12.5 years).

RESULTS

X4 viruses were detected by genetic analysis in three of six samples from the R5X4 group, accounting for 1.3-100% of the virus quasispecies, during PHI, and in four of six samples (accounting for 6.7-100%) at the end of follow-up. No X4 virus was detected in the R5 group during PHI and in only one patient (accounting for 1.2%) at the end of follow-up. The complexity of the virus quasispecies at the stage of PHI was higher in the R5X4 group than in the R5 group. Complexity increased from PHI to the end of follow-up in the R5 group but remained stable in the R5X4 group.

CONCLUSION

CXCR4-using viruses persisted in the peripheral blood mononuclear cells of several patients on suppressive antiretroviral therapy for a median duration of 12.5 years after PHI. The genetic complexity of HIV-1 evolved differently post-PHI in patients infected with R5X4 viruses from those infected with R5 viruses.

Acute HIV Infection and CD4/CD8 Ratio Normalization After Antiretroviral Therapy Initiation

BACKGROUND

We estimated the effect of initiating virologically suppressive antiretroviral therapy (ART) during acute HIV infection versus chronic HIV infection (AHI vs. CHI) on CD4/CD8 ratio normalization.

SETTING

A prospective clinical cohort study.

METHODS

We included patients initiating ART with AHI and CHI between 2000 and 2015 and compared time from ART initiation to the first normal CD4/CD8 ratio (defined as CD4/CD8 ≥1) using Kaplan-Meier curves and multivariable Cox proportional hazards models. Patient time was censored at virologic failure, lost to follow-up, or death. We also characterized CD4, CD8, and CD4/CD8 trajectories over the first 3 years of ART.

RESULTS

The 1198 patients were 27% female and 60% African American, with a median age of 37 years (interquartile range 28-47) at ART initiation. The 83 AHI patients were more likely male, younger, and of white race, than CHI patients. After 2 years of suppressive ART, 70% of AHI patients achieved a normal CD4/CD8 ratio, compared to 6%-38% of CHI patients, with greater likelihood of normalization at higher baseline CD4 counts. Time to normalization was shortest among AHI patients, followed by CHI patients with higher baseline CD4. The adjusted hazard ratio for time to normalization for AHI patients compared to CHI patients with baseline CD4 >350 was 4.33 (95% CI: 3.16 to 5.93). Higher baseline CD4/CD8 ratio was also associated with time to normalization (adjusted hazard ratio 1.54; 1.46, 1.63, per 0.1 increase in ratio).

CONCLUSIONS

Initiating ART during AHI at higher baseline CD4 cell counts and CD4/CD8 ratios was associated with shorter time to CD4/CD8 ratio normalization.

Impact of ART on dynamics of growth factors and cytokines in primary HIV infection

Antiretroviral treatment (ART) of Primary HIV Infection (PHI) has demonstrated virological and immunological benefits. The effect of early ART during PHI on the level of growth factors and chemokines modulating immune cell functions remains to be established. The aim of our work was to analyze the dynamics of 27 cytokines, chemokines and growth/regulation factors in plasma of HIV infected patients treated during PHI. Patients with PHI (n = 43) were enrolled before, 24 and 48 weeks after therapy initiation. Quantification of soluble immune mediators was performed in plasma from HIV infected patients and healthy donors (HD, n = 7) by Luminex technology. The cytokines profile was strongly perturbed in primary HIV infected patients when compared to healthy donors (HD). After 48 weeks of ART, some of these factors were restored to HD level (IL-2, IL-5, IL-7, IL-9, IL12p70, TNFα) while others persisted higher than HD (IL-6, IL-10, IL-13). Interestingly, a subset of chemokines, such as IL-8, MCP-1, RANTES and CCL27, and growth factors such as HGF, SCF and GM-CSF, increased during ART, reaching values significantly higher than HD after 48 weeks. Moreover, the G-CSF and MIP-1β soluble mediators were persistently altered and showed an inverse correlation with the CD4/CD8 T cell ratio. The increase of chemokines with antiviral activity and of growth factors with hematopoietic and immunomodulatory properties may have beneficial effects. Other studies are mandatory to evaluate the effects of long lasting levels of these factors to clarify their possible role in the context of protection/pathogenesis.

Lovastatin Inhibits HIV-1-Induced MHC-I Downregulation by Targeting Nef-AP-1 Complex Formation: A New Strategy to Boost Immune Eradication of HIV-1 Infected Cells

Current combined antiretroviral therapy (cART) mainly targets 3 of the 15 HIV proteins leaving many potential viral vulnerabilities unexploited. To purge the HIV-1 latent reservoir, various strategies including “shock and kill” have been developed. A key question is how to restore impaired immune surveillance. HIV-1 protein Nef has long been known to mediate the downregulation of cell-surface MHC-I and assist HIV-1 to evade the immune system. Through high throughput screening of Food and Drug Administration (FDA) approved drugs, we identified lovastatin, a statin drug, to significantly antagonize Nef to downregulate MHC-I, CD4, and SERINC5, and inhibit the intrinsic infectivity of virions. In addition, lovastatin boosted autologous CTLs to eradicate the infected cells and effectively inhibit the subsequent viral rebound in CD4⁺ T-lymphocytes isolated from HIV-1-infected individuals receiving suppressive cART. Furthermore, we found that lovastatin inhibits Nef-induced MHC-I downregulation by directly binding with Nef and disrupting the Nef–AP-1 complex. These results demonstrate that lovastatin is a promising agent for counteracting Nef-mediated downregulation of MHC-I, CD4, and SERINC5. Lovastatin could potentially be used in the clinic to enhance anti-HIV-1 immune surveillance.

Simian-Human Immunodeficiency Virus SHIV.CH505 Infection of Rhesus Macaques Results in Persistent Viral Replication and Induces Intestinal Immunopathology

Simian-human immunodeficiency viruses (SHIVs) have been utilized to test vaccine efficacy and characterize mechanisms of viral transmission and pathogenesis. However, the majority of SHIVs currently available have significant limitations in that they were developed using sequences from chronically HIV-infected individuals or uncommon HIV subtypes or were optimized for the macaque model by serially passaging the engineered virus in vitro or in vivo Recently, a newly developed SHIV, SHIV.C.CH505.375H.dCT (SHIV.CH505), which incorporates vpu-env (gp140) sequences from a transmitted/founder HIV-1 subtype C strain, was shown to retain attributes of primary HIV-1 strains. However, a comprehensive analysis of the immunopathology that results from infection with this virus, especially in critical tissue compartments like the intestinal mucosa, has not been completed. In this study, we evaluated the viral dynamics and immunopathology of SHIV.CH505 in rhesus macaques. In line with previous findings, we found that SHIV.CH505 is capable of infecting and replicating efficiently in rhesus macaques, resulting in peripheral viral kinetics similar to that seen in pathogenic SIV and HIV infection. Furthermore, we observed significant and persistent depletions of CCR5⁺ and CCR6⁺ CD4⁺ T cells in mucosal tissues, decreases in CD4⁺ T cells producing Th17 cell-associated cytokines, CD8⁺ T cell dysfunction, and alterations of B cell and innate immune cell function, indicating that SHIV.CH505 elicits intestinal immunopathology typical of SIV/HIV infection. These findings suggest that SHIV.CH505 recapitulates the early viral replication dynamics and immunopathogenesis of HIV-1 infection of humans and thus can serve as a new model for HIV-1 pathogenesis, treatment, and prevention research.IMPORTANCE The development of chimeric SHIVs has been instrumental in advancing our understanding of HIV-host interactions and allowing for in vivo testing of novel treatments. However, many of the currently available SHIVs have distinct drawbacks and are unable to fully reflect the features characteristic of primary SIV and HIV strains. Here, we utilize rhesus macaques to define the immunopathogenesis of the recently developed SHIV.CH505, which was designed without many of the limitations of previous SHIVs. We observed that infection with SHIV.CH505 leads to peripheral viral kinetics and mucosal immunopathogenesis comparable with those caused by pathogenic SIV and HIV. Overall, these data provide evidence of the value of SHIV.CH505 as an effective model of SIV/HIV infection and an important tool that can be used in future studies, including preclinical testing of new therapies or prevention strategies.

Kynurenine 3-Monooxygenase Inhibition during Acute Simian Immunodeficiency Virus Infection Lowers PD-1 Expression and Improves Post-Combination Antiretroviral Therapy CD4+ T Cell Counts and Body Weight

The kynurenine pathway (KP) is a key regulator of many important physiological processes and plays a harmful role in cancer, many neurologic conditions, and chronic viral infections. In HIV infection, KP activity is consistently associated with reduced CD4 T cell counts and elevated levels of T cell activation and viral load; it also independently predicts mortality and morbidity from non-AIDS events. Kynurenine 3-monooxygenase (KMO) is a therapeutically important target in the KP. Using the nonhuman primate model of SIV infection in rhesus macaques, we investigated whether KMO inhibition could slow the course of disease progression. We used a KMO inhibitor, CHDI-340246, to perturb the KP during early acute infection and followed the animals for 1 y to assess clinical outcomes and immune phenotype and function during pre-combination antiretroviral therapy acute infection and combination antiretroviral therapy-treated chronic infection. Inhibition of KMO in acute SIV infection disrupted the KP and prevented SIV-induced increases in downstream metabolites, improving clinical outcome as measured by both increased CD4+ T cell counts and body weight. KMO inhibition increased naive T cell frequency and lowered PD-1 expression in naive and memory T cell subsets. Importantly, early PD-1 expression during acute SIV infection predicted clinical outcomes of body weight and CD4+ T cell counts. Our data indicate that KMO inhibition in early acute SIV infection provides clinical benefit and suggest a rationale for testing KMO inhibition as an adjunctive treatment in SIV/HIV infection to slow the progression of the disease and improve immune reconstitution.

HIV Disease Progression: Overexpression of the Ectoenzyme CD38 as a Contributory Factor?

Despite abundant evidence associating CD38 overexpression and CD4 T cell depletion in HIV infection, no causal relation has been investigated. To address this issue, a series of mechanisms are proposed, supported by evidence from different fields, by which CD38 overexpression can facilitate CD4 T cell depletion in HIV infection. According to this model, increased catalytic activity of CD38 may reduce CD4 T cells' cytoplasmic nicotin-amide adenine dinucleotide (NAD), leading to a chronic Warburg effect. This will reduce mitochondrial function. Simultaneously, CD38's catalytic products ADPR and cADPR may be transported to the cytoplasm, where they can activate calcium channels and increase cytoplasmic Ca2+ concentrations, further altering mitochondrial integrity. These mechanisms will decrease the viability and regenerative capacity of CD4 T cells. These hypotheses can be tested experimentally, and might reveal novel therapeutic targets. Also see the video abstract here https://youtu.be/k1LTyiTKPKs.

Immune Checkpoints as the Immune System Regulators and Potential Biomarkers in HIV-1 Infection

Immune checkpoints are several co-stimulatory and inhibitory pathways that regulate T cell immune responses. Most of the discoveries about immune checkpoints were made in cancer research where inhibitory immune checkpoints cause immune exhaustion and down-regulate anti-tumor responses. In addition to cancer, immune checkpoints are exploited in chronic infectious diseases. In human immunodeficiency virus (HIV) infection, the immune checkpoint molecule called programmed cell death protein 1 (PD-1) has been determined as being a major regulatory factor for T cell exhaustion. Recent studies with antibodies blocking either PD-1 ligand 1 (PD-L1) or PD-1 show not only promising results in the enhancement of HIV-specific immune responses but even in reducing the latent HIV reservoir. Apart from the therapeutic target for a functional cure of HIV-1, immune checkpoint molecules might be used as biomarkers for monitoring disease progression and therapeutic response. In this review, we will summarize and discuss the inhibitory immune checkpoint molecules PD-1, cytotoxic T-lymphocyte-associated protein 4 (CTLA4), lymphocyte-activation gene 3 (LAG3), and T cell immunoglobulin and mucin-domain-containing-3 (TIM3) as well as the co-stimulatory molecules CD40L and CD70, including their role in immunity, with a particular focus on HIV infection, and being potential targets for a functional HIV cure.

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.

Within-patient mutation frequencies reveal fitness costs of CpG dinucleotides and drastic amino acid changes in HIV

HIV has a high mutation rate, which contributes to its ability to evolve quickly. However, we know little about the fitness costs of individual HIV mutations in vivo, their distribution and the different factors shaping the viral fitness landscape. We calculated the mean frequency of transition mutations at 870 sites of the pol gene in 160 patients, allowing us to determine the cost of these mutations. As expected, we found high costs for non-synonymous and nonsense mutations as compared to synonymous mutations. In addition, we found that non-synonymous mutations that lead to drastic amino acid changes are twice as costly as those that do not and mutations that create new CpG dinucleotides are also twice as costly as those that do not. We also found that G→A and C→T mutations are more costly than A→G mutations. We anticipate that our new in vivo frequency-based approach will provide insights into the fitness landscape and evolvability of not only HIV, but a variety of microbes.

Past Life and Future Effects-How Heterologous Infections Alter Immunity to Influenza Viruses

Influenza virus frequently mutates due to its error-prone polymerase. This feature contributes to influenza virus’s ability to evade pre-existing immunity, leading to annual epidemics and periodic pandemics. T cell memory plays a key protective role in the face of an antigenically distinct influenza virus strain because T cell targets are often derived from conserved internal proteins, whereas humoral immunity targets are often sites of increased mutation rates that are tolerated by the virus. Most studies of influenza T cell memory are conducted in naive, specific pathogen free mice and do not account for repetitive influenza infection throughout a lifetime, sequential acute heterologous infections between influenza infections, or heterologous chronic co-infections. By contrast to these mouse models, humans often experience numerous influenza infections, encounter heterologous acute infections between influenza infections, and are infected with at least one chronic virus. In this review, we discuss recent advances in understanding the effects of heterologous infections on the establishment and maintenance of CD8+ T cell immunological memory. Understanding the various factors that affect immune memory can provide insights into the development of more effective vaccines and increase reproducibility of translational studies between animal models and clinical results.

Exosome markers associated with immune activation and oxidative stress in HIV patients on antiretroviral therapy

Exosomes are nanovesicles released from most cell types including immune cells. Prior studies suggest exosomes play a role in HIV pathogenesis, but little is known about exosome cargo in relation to immune responses and oxidative stress. Here, we characterize plasma exosomes in HIV patients and their relationship to immunological and oxidative stress markers. Plasma exosome fractions were isolated from HIV-positive subjects on ART with suppressed viral load and HIV-negative controls. Exosomes were characterized by electron microscopy, nanoparticle tracking, immunoblotting, and LC-MS/MS proteomics. Plasma exosomes were increased in HIV-positive subjects compared to controls, and correlated with increased oxidative stress markers (cystine, oxidized cys-gly) and decreased PUFA (DHA, EPA, DPA). Untargeted proteomics detected markers of exosomes (CD9, CD63, CD81), immune activation (CD14, CRP, HLA-A, HLA-B), oxidative stress (CAT, PRDX1, PRDX2, TXN), and Notch4 in plasma exosomes. Exosomal Notch4 was increased in HIV-positive subjects versus controls and correlated with immune activation markers. Treatment of THP-1 monocytic cells with patient-derived exosomes induced expression of genes related to interferon responses and immune activation. These results suggest that exosomes in ART-treated HIV patients carry proteins related to immune activation and oxidative stress, have immunomodulatory effects on myeloid cells, and may have pro-inflammatory and redox effects during pathogenesis.

Elevated Level of CD4+ T Cell Immune Activation in Acutely HIV-1-Infected Stage Associates With Increased IL-2 Production and Cycling Expression, and Subsequent CD4+ T Cell Preservation

Persistent immune activation is a striking consequence of HIV-1 infection and a driving force of CD4⁺ T cell depletion and AIDS events during chronic infection. High level of T cell immune activation associates with antiretroviral therapy (ART)-treated clinical outcomes in chronically HIV-1-infected patients. However, the role of T cell activation during acute infection stage in subsequent CD4⁺ T cell decline in the absence of ART treatment is unknown. In this study, we enrolled 26 acutely HIV-1-infected patients in the absence of ART treatment from a prospective acute HIV-1 infection cohort in Beijing (PRIMO). A comprehensive analysis of CD4⁺ and CD8⁺ T cell immune activation during acute infection stage and the clinical outcomes was studied. We found that patients with higher level of CD4⁺ T cell activation (%CD38⁺HLA-DR⁺CD4⁺ T cells) exhibited more effective function (%IL-2 production and %ki67 expression) in CD4⁺ T cells compared to those from patients without increased T cell activation at the acute phase. Direct correlations were observed between CD4⁺ T cell activation and the percentages of IL-2-producing or ki67-expressing CD4⁺ T cells in patients at the acute phase of infection. Importantly, the increased levels of CD4⁺ T cell immune activation, IL-2 production, and cycling expression during acute infection were associated with less decline of CD4⁺ T cell after 2 years of infection. However, immune exhaustion molecules in acute infection, including CD160, T cell immunoglobulin and ITIM domain, programmed cell death protein 1, and T cell immunoglobulin and mucin 3, were not associated with the CD4⁺ T cell depletion. These significant associations of CD4⁺ T cell activation were not demonstrable for CD8⁺ T cell activation at the acute phase. Taken together, our observations provide new insight into the possible role of T cell activation in preventing CD4⁺ T cell depletion during acute HIV-1 infection.