Selective Loss of Early Differentiated, Highly Functional PD1high CD4 T Cells with HIV Progression

Low-level HIV-1 viremia affects T-cell activation and senescence in long-term treated adults in the INSTI era

BACKGROUND

Around 10% of people with HIV (PWH) exhibit a low-level viremia (LLV) under antiretroviral therapy (ART). However, its origin and clinical significance are largely unknown, particularly at viremias between 50 and 200 copies/mL and under modern ART based on integrase strand transfer inhibitors (INSTIs). Our aim was to characterize their poor immune response against HIV in comparison to individuals with suppressed viremia (SV) and non-HIV controls (NHC).

METHODS

Transversal observational study in 81 matched participants: 27 PWH with LLV, 27 PWH with SV, and 27 NHC. Activation (CD25, HLA-DR, and CD38) and senescence [CD57, PD1, and HAVCR2 (TIM3)] were characterized in peripheral T-cell subsets by spectral flow cytometry. 45 soluble biomarkers of systemic inflammation were evaluated by immunoassays. Differences in cell frequencies and plasma biomarkers among groups were evaluated by a generalized additive model for location, scale, and shape (GAMLSS) and generalized linear model (GLM) respectively, adjusted by age, sex at birth, and ART regimen.

RESULTS

The median age was 53 years and 77.8% were male. Compared to NHC, PWH showed a lower CD4+/CD8+ ratio and increased activation, senescence, and inflammation, highlighting IL-13 in LLV. In addition, LLV showed a downtrend in the frequency of CD8+ naive and effector memory (EM) type 1 compared to SV, along with higher activation and senescence in CD4+ and CD8+ EM and terminally differentiated effector memory RA+ (TEMRA) subpopulations. No significant differences in systemic inflammation were observed between PWH groups.

CONCLUSION

LLV between 50 and 200 copies/mL leads to reduced cytotoxic activity and T-cell dysfunction that could affect cytokine production, being unable to control and eliminate infected cells. The increase in senescence markers suggests a progressive loss of immunological memory and a reduction in the proliferative capacity of immune cells. This accelerated immune aging could lead to an increased risk of developing future comorbidities. These findings strongly advocate for heightened surveillance of these PWH to promptly identify potential future complications.

A Greater Increase in Complement C5a Receptor 1 Level at Onset and a Smaller Decrease in Immunoglobulin G Level after Recovery in Severer Coronavirus Disease 2019 Patients: A New Analysis of Existing Data with a New Two-Tailed t-Test

(1) Background: It is our purpose to identify the differences in the changes in Complement C5a receptor 1 (C5aR1) levels showing the degree of inflammation at onset and Immunoglobulin G (IgG) levels showing the extent of survival of the virus fragments after recovery between coronavirus disease 2019 (COVID-19) and pneumonia coronavirus disease (non-COVID-19) for saving patients' lives. (2) Methods: First, the studies showing these markers' levels in individual patients before and after the passage of time were selected from the PubMed Central® databases with the keywords (((COVID-19) AND individual) NOT review) AND C5a/IgG. Then, no changes in these markers' levels with conventional analyses were selected from the studies. Finally, the no changes were reexamined with our new two-tailed t-test using the values on the regression line between initial levels and changed levels instead of the mean or median of changed levels as the expected values of changed levels. (3) Results: Not conventional analyses but our new t-test suggested a greater increase in C5aR1-levels at onset and a smaller decrease in IgG-levels after recovery in COVID-19 patients than non-COVID-19 patients. (4) Conclusion: Our new t-test also should be used in clinics for COVID-19 patients.

Comparisons of Underlying Mechanisms, Clinical Efficacy and Safety Between Anti-PD-1 and Anti-PD-L1 Immunotherapy: The State-of-the-Art Review and Future Perspectives

Over the past decade, diverse PD-1/PD-L1 blockades have demonstrated significant clinical benefit in across a wide range of tumor and cancer types. With the increasing number of PD-1/PD-L1 blockades available in the market, differences between the clinical performance of each of them started to be reported. Here, we provide a comprehensive historical and biological perspective regarding the underlying mechanism and clinical performance of PD-1/PD-L1 blockades, with an emphasis on the comparisons of their clinical efficacy and safety. The real-world evidence indicated that PD-1 blockade may be more effective than the PD-L1, though no significant differences were found as regards to their safety profiles. Future head-to-head studies are warranted for direct comparison between them. Finally, we summarize the yet to be elucidated questions and future promise of anti-PD-1/PD-L1 immunotherapy, including a need to explore novel biomarkers, novel combinatorial strategies, and their clinical use on chronic infection.

CD300a identifies a CD4+ memory T cell subset with a higher susceptibility to HIV-1 infection

: Human CD300a is known to promote the infection by dengue and other enveloped viruses and is overexpressed on CD4 T cells from HIV-1-infected patients. We found that infected CD4+RA- T cells from untreated HIV-1-infected patients were mostly CD300a+. Furthermore, CD300a expressing CD4+RA- T cells from healthy donors were significantly more infected by HIV-1 in vitro than CD300a- cells. CD300a might represent a biomarker of susceptibility to HIV-1 infection on memory CD4 T lymphocytes.

T cells with high PD-1 expression are associated with lower HIV-specific immune responses despite long-term antiretroviral therapy

OBJECTIVE

We evaluated frequencies of T cells with high PD-1 expression (PD-1) before and after long-term effective antiretroviral therapy (ART), and determined if frequencies on-ART correlated positively with measures of HIV persistence and negatively with HIV-specific responses.

METHODS

We enrolled individuals who started ART during chronic infection and had durable suppression of viremia for at least 4 years (N = 99). We assessed PD-1 T-cell frequencies at timepoints pre-ART and on-ART using flow cytometry, and evaluated how frequencies on-ART are associated with measures of HIV persistence, HIV-specific immune responses, and immune activation levels.

RESULTS

Pre-ART, PD-1 CD4 T cells correlated positively with viremia and negatively with CD4 T-cell count. At year 1 on-ART, %PD-1 CD4 T cells decreased but then remained stable at 4 and 6-15 years on-ART, whereas %PD-1 CD8 T cells on-ART remained similar to pre-ART. PD-1 CD4 T cells correlated positively with HIV DNA pre-ART and on-ART, and with CD4 T-cell activation on-ART. PD-1 CD4 T cells negatively correlated with HIV Gag-specific and Env-specific T-cell responses but not with CMV-specific or EBV-specific responses. PD-1 CD8 T cells trended towards a negative correlation with responses to Gag and Env, but not to CMV and EBV.

CONCLUSION

PD-1 T cells persist in blood despite prolonged suppression on ART, correlate with HIV DNA levels, and are associated with lower HIV-specific T-cell responses but not CMV-specific or EBV-specific responses, suggesting that these cells are HIV-specific. The findings support evaluating PD-1 blockade strategies for their effect on HIV persistence and HIV-specific immunity.

Bone Marrow-Derived CD4+ T Cells Are Depleted in Simian Immunodeficiency Virus-Infected Macaques and Contribute to the Size of the Replication-Competent Reservoir

The bone marrow (BM) is the key anatomic site for hematopoiesis and plays a significant role in the homeostasis of mature T cells. However, very little is known on the phenotype of BM-derived CD4+ T cells, their fate during simian immunodeficiency virus (SIV) infection, and their contribution to viral persistence during antiretroviral therapy (ART). In this study, we characterized the immunologic and virologic status of BM-derived CD4+ T cells in rhesus macaques prior to SIV infection, during the early chronic phase of infection, and during ART. We found that BM memory CD4+ T cells are significantly depleted following SIV infection, at levels that are similar to those measured in the peripheral blood (PB). In addition, BM-derived memory CD4+ T cells include a high frequency of cells that express the coinhibitory receptors CTLA-4 and PD-1, two subsets previously shown to be enriched in the viral reservoir; these cells express Ki-67 at levels similar to or higher than the same cells in PB. Finally, when we analyzed SIV-infected RMs in which viral replication was effectively suppressed by 12 months of ART, we found that BM CD4+ T cells harbor SIV DNA and SIV RNA at levels comparable to those of PB CD4+ T cells, including replication-competent SIV. Thus, BM is a largely understudied anatomic site of the latent reservoir which contributes to viral persistence during ART and needs to be further characterized and targeted when designing therapies for a functional or sterilizing cure to HIV.IMPORTANCE The latent viral reservoir is one of the major obstacles in purging the immune system of HIV. It is paramount that we elucidate which anatomic compartments harbor replication-competent virus, which upon ART interruption results in viral rebound and pathogenesis. In this study, using the rhesus macaque model of SIV infection and ART, we examined the immunologic status of the BM and its role as a potential sanctuary for latent virus. We found that the BM compartment undergoes a similar depletion of memory CD4+ T cells as PB, and during ART treatment the BM-derived memory CD4+ T cells contain high levels of cells expressing CTLA-4 and PD-1, as well as amounts of cell-associated SIV DNA, SIV RNA, and replication-competent virus comparable to those in PB. These results enrich our understanding of which anatomic compartments harbor replication virus and suggest that BM-derived CD4+ T cells need to be targeted by therapeutic strategies aimed at achieving an HIV cure.

PD-1 Expression on Mycobacterium tuberculosis-Specific CD4 T Cells Is Associated With Bacterial Load in Human Tuberculosis

Persistent antigen stimulation in chronic infections has been associated with antigen-specific T cell dysfunction and upregulation of inhibitory receptors, including programmed cell death protein 1 (PD-1). Pulmonary tuberculosis (TB) disease is characterized by high levels of Mycobacterium tuberculosis (Mtb), yet the relationship between bacterial load, PD-1 expression, and Mtb-specific T cell function in human TB has not been well-defined. Using peripheral blood samples from adults with LTBI and with pulmonary TB disease, we tested the hypothesis that PD-1 expression is associated with bacterial load and functional capacity of Mtb-specific T cell responses. We found that PD-1 was expressed at significantly higher levels on Th1 cytokine-producing Mtb-specific CD4 T cells from patients with smear-positive TB, compared with smear-negative TB and LTBI, which decreased after completion of anti-TB treatment. By contrast, expression of PD-1 on Mtb-specific CD8 T cells was significantly lower than on Mtb-specific CD4 T cells and did not differ by Mtb infection and disease status. In vitro stimulation of PBMC with Mtb antigens demonstrated that PD-1 is induced on proliferating Mtb-specific CD4 T cells and that Th1 cytokine production capacity is preferentially maintained within PD-1⁺ proliferating CD4 T cells, compared with proliferating Mtb-specific CD4 T cells that lack PD-1 expression. Together, these data indicate that expression of PD-1 on Mtb-specific CD4 T cells is indicative of mycobacterial antigen exposure and identifies a population of effector cells with Th1 cytokine production capacity. These studies provide novel insights into the role of the PD-1 pathway in regulating CD4 and CD8 T cell responses in Mtb infection and provide rationale for future studies to evaluate PD-1 expression on antigen-specific CD4 T cells as a potential biomarker for bacterial load and treatment response in human TB.

Altered Expression of CD300a Inhibitory Receptor on CD4+ T Cells From Human Immunodeficiency Virus-1-Infected Patients: Association With Disease Progression Markers

The ability of the CD300a inhibitory receptor to modulate immune cell functions and its involvement in the pathogenesis of many diseases has aroused a great interest in this molecule. Within human CD4+ T lymphocytes from healthy donors, the inhibitory receptor CD300a is differentially expressed among different T helper subsets. However, there are no data about the expression and regulation of CD300a receptor on CD4+ T cells from human immunodeficiency virus (HIV)-1-infected patients. The objective of this study was to investigate the expression of CD300a on CD4+ T cells from HIV-infected patients on suppressive combined antiretroviral therapy (cART) and cART naïve patients. Our results have demonstrated that the expression levels of this inhibitory receptor were higher on CD4+ T cells from HIV-1 infected subjects compared with healthy donors, and that cART did not reverse the altered expression of CD300a receptor in these patients. We have observed an increase of CD300a expression on both PD1+CD4+ and CD38+CD4+ T cells from HIV-1 infected people. Interestingly, a triple positive (CD300a+PD1+CD38+) subset was expanded in naïve HIV-1 infected patients, while it was very rare in healthy donors and patients on cART. Finally, we found a negative correlation of CD300a expression on CD4+ T lymphocytes and some markers associated with HIV-1 disease progression. Thus, our results show that HIV-1 infection has an impact in the regulation of CD300a inhibitory receptor expression levels, and further studies will shed light into the role of this cell surface receptor in the pathogenesis of HIV infection.

Immunomodulatory effects of Tim-3 and PD-1 on chronic hepatitis B virus infection

In patients with chronic hepatitis B virus (HBV) infection, the immune cells are dysfunctional, and the immune function cannot work normally. T-cell immunoglobulin mucin-3 (Tim-3) and programmed death receptor-1 (PD-1) are overexpressed on the surface of immune cells, such as cluster of differentiation (CD)4+, CD8+ T-lymphocytes, and natural killer (NK) cells. Many studies indicate that this phenomenon is closely related to the persistence, occurrence, development, and prognosis of HBV. Tim-3 and PD-1 may be used as new immune targets for the treatment of chronic hepatitis B.

CTLA-4+PD-1- Memory CD4+ T Cells Critically Contribute to Viral Persistence in Antiretroviral Therapy-Suppressed, SIV-Infected Rhesus Macaques

Antiretroviral therapy (ART) suppresses viral replication in HIV-infected individuals but does not eliminate the reservoir of latently infected cells. Recent work identified PD-1+ follicular helper T (Tfh) cells as an important cellular compartment for viral persistence. Here, using ART-treated, SIV-infected rhesus macaques, we show that CTLA-4+PD-1- memory CD4+ T cells, which share phenotypic markers with regulatory T cells, were enriched in SIV DNA in blood, lymph nodes (LN), spleen, and gut, and contained replication-competent and infectious virus. In contrast to PD-1+ Tfh cells, SIV-enriched CTLA-4+PD-1- CD4+ T cells were found outside the B cell follicle of the LN, predicted the size of the persistent viral reservoir during ART, and significantly increased their contribution to the SIV reservoir with prolonged ART-mediated viral suppression. We have shown that CTLA-4+PD-1- memory CD4+ T cells are a previously unrecognized component of the SIV and HIV reservoir that should be therapeutically targeted for a functional HIV-1 cure.

HIV-Infected Children Have Elevated Levels of PD-1+ Memory CD4 T Cells With Low Proliferative Capacity and High Inflammatory Cytokine Effector Functions

Background

During human immunodeficiency virus (HIV) disease, chronic immune activation leads to T-cell exhaustion. PD-1 identifies "exhausted" CD8 T cells with impaired HIV-specific effector functions, but its role on CD4 T cells and in HIV-infected children is poorly understood.

Methods

In a Kenyan cohort of vertically HIV-infected children, we measured PD-1+ CD4 T-cell frequencies and phenotype by flow cytometry and their correlation with HIV disease progression and immune activation. Second, in vitro CD4 T-cell proliferative and cytokine responses to HIV-specific and -nonspecific stimuli were assessed with and without PD-1 blockade.

Results

HIV-infected children have increased frequencies of PD-1+ memory CD4 T cells that fail to normalize with antiretroviral treatment. These cells are comprised of central and effector memory subsets and correlate with HIV disease progression, measured by viral load, CD4 percentage, CD4:CD8 T-cell ratio, and immune activation. Last, PD-1+ CD4 T cells predict impaired proliferative potential yet preferentially secrete the Th1 and Th17 cytokines interferon-γ and interleukin 17A, and are unresponsive to in vitro PD-1 blockade.

Conclusions

This study highlights differences in PD-1+ CD4 T-cell memory phenotype and response to blockade between HIV-infected children and adults, with implications for potential immune checkpoint therapies.

In vitro and in vivo antivirus activity of an anti-programmed death-ligand 1 (PD-L1) rat-bovine chimeric antibody against bovine leukemia virus infection

Programmed death-1 (PD-1), an immunoinhibitory receptor on T cells, is known to be involved in immune evasion through its binding to PD-ligand 1 (PD-L1) in many chronic diseases. We previously found that PD-L1 expression was upregulated in cattle infected with bovine leukemia virus (BLV) and that an antibody that blocked the PD-1/PD-L1 interaction reactivated T-cell function in vitro. Therefore, this study assessed its antivirus activities in vivo. First, we inoculated the anti-bovine PD-L1 rat monoclonal antibody 4G12 into a BLV-infected cow. However, this did not induce T-cell proliferation or reduction of BLV provirus loads during the test period, and only bound to circulating IgM⁺ B cells until one week post-inoculation. We hypothesized that this lack of in vivo effects was due to its lower stability in cattle and so established an anti-PD-L1 rat-bovine chimeric antibody (Boch4G12). Boch4G12 was able to bind specifically with bovine PD-L1, interrupt the PD-1/PD-L1 interaction, and activate the immune response in both healthy and BLV-infected cattle in vitro. Therefore, we experimentally infected a healthy calf with BLV and inoculated it intravenously with 1 mg/kg of Boch4G12 once it reached the aleukemic (AL) stage. Cultivation of peripheral blood mononuclear cells (PBMCs) isolated from the tested calf indicated that the proliferation of CD4⁺ T cells was increased by Boch4G12 inoculation, while BLV provirus loads were significantly reduced, clearly demonstrating that this treatment induced antivirus activities. Therefore, further studies using a large number of animals are required to support its efficacy for clinical application.

CCR6/CCL20 chemokine axis in human immunodeficiency virus immunity and pathogenesis

Recent studies in human immunodeficiency virus (HIV) have garnered interest for the role of CC chemokine receptor 6 (CCR6) and its known ligands, CC chemokine ligand 20 (CCL20) and human β-defensins, in viral entry, dissemination and antiviral immunity. Several studies have suggested that CCR6 may also act as a weak co-receptor of HIV entry, in addition to the canonical CXC chemokine receptor 4 (CXCR4) and CCR5. However, the pathogenic significance has yet to be demonstrated as the observations for preferential infection of CD4+CCR6+ over CD4+CCR6- T cells appear to be independent of CCR6 expression. This indicates means for preferential infection other than CCR6 co-receptor use. Attention has also turned to the inadvertent role of the CCR6/CCL20 axis in attracting key immune cells, including TH17 cells and dendritic cells, to sites of infection and propagating the virus to other sites of the body. This review article will summarize the latest evidence that the CCR6/CCL20 chemokine axis is playing an important role in HIV pathogenesis and immunity. Further work with in vivo studies is needed to establish the biological and, hence, therapeutic significance of these findings.

Lower Baseline Germinal Center Activity and Preserved Th1 Immunity Are Associated With Hepatitis B Vaccine Response in Treated HIV Infection

BACKGROUND

Why HIV-infected individuals have poor responses to standard dose and schedule hepatitis B virus immunization is not well understood.

METHODS

We compared the serologic and cellular immune profiles of treated HIV-infected individuals with similar durations of infection and preserved CD4 counts (> 350 cells/microliter) by hepatitis B vaccine (HBV) response before and after vaccination.

RESULTS

Similar levels of immune activation and plasma cytokine profile were found between non-responders and responders. The baseline plasma levels of CXCL-13, a surrogate of germinal center reactivity, were significantly lower in HBV responders compared to HBV non-responders and were a predictor of both vaccine response and titer. Furthermore, response to HBV vaccination was associated with a significantly higher frequency of circulating IgG^high memory B cells post vaccination and preserved Th1 antigen-specific T-cell responses.

CONCLUSIONS

Taken together, our data suggest that preserved Th1 responses are associated with hepatitis B vaccine response in treated HIV infection.

Mucosal Regulatory T Cells and T Helper 17 Cells in HIV-Associated Immune Activation

Residual mucosal inflammation along with chronic systemic immune activation is an important feature in individuals infected with human immunodeficiency virus (HIV), and has been linked to a wide range of co-morbidities, including malignancy, opportunistic infections, immunopathology, and cardiovascular complications. Although combined antiretroviral therapy (cART) can reduce plasma viral loads to undetectable levels, reservoirs of virus persist, and increased mortality is associated with immune dysbiosis in mucosal lymphoid tissues. Immune-based therapies are pursued with the goal of improving CD4(+) T-cell restoration, as well as reducing chronic immune activation in cART-treated patients. However, the majority of research on immune activation has been derived from analysis of circulating T cells. How immune cell alterations in mucosal tissues contribute to HIV immune dysregulation and the associated risk of non-infectious chronic complications is less studied. Given the significant differences between mucosal T cells and circulating T cells, and the immediate interactions of mucosal T cells with the microbiome, more attention should be devoted to mucosal immune cells and their contribution to systemic immune activation in HIV-infected individuals. Here, we will focus on mucosal immune cells with a specific emphasis on CD4(+) T lymphocytes, such as T helper 17 cells and CD4(+)Foxp3(+) regulatory T cells (Tregs), which play crucial roles in maintaining mucosal barrier integrity and preventing inflammation, respectively. We hypothesize that pro-inflammatory milieu in cART-treated patients with immune activation significantly contributes to enhanced loss of Th17 cells and increased frequency of dysregulated Tregs in the mucosa, which in turn may exacerbate immune dysfunction in HIV-infected patients. We also present initial evidence to support this hypothesis. A better comprehension of how pro-inflammatory milieu impacts these two types of cells in the mucosa will shed light on mucosal immune dysfunction and HIV reservoirs, and lead to novel ways to restore immune functions in HIV(+) patients.