Preferential depletion of gut CD4-expressing iNKT cells contributes to systemic immune activation in HIV-1 infection

Mucosal T-cell responses to chronic viral infections: Implications for vaccine design

Mucosal surfaces that line the respiratory, gastrointestinal and genitourinary tracts are the major interfaces between the immune system and the environment. Their unique immunological landscape is characterized by the necessity of balancing tolerance to commensal microorganisms and other innocuous exposures against protection from pathogenic threats such as viruses. Numerous pathogenic viruses, including herpesviruses and retroviruses, exploit this environment to establish chronic infection. Effector and regulatory T-cell populations, including effector and resident memory T cells, play instrumental roles in mediating the transition from acute to chronic infection, where a degree of viral replication is tolerated to minimize immunopathology. Persistent antigen exposure during chronic viral infection leads to the evolution and divergence of these responses. In this review, we discuss advances in the understanding of mucosal T-cell immunity during chronic viral infections and how features of T-cell responses develop in different chronic viral infections of the mucosa. We consider how insights into T-cell immunity at mucosal surfaces could inform vaccine strategies: not only to protect hosts from chronic viral infections but also to exploit viruses that can persist within mucosal surfaces as vaccine vectors.

Activation-induced pyroptosis contributes to the loss of MAIT cells in chronic HIV-1 infected patients

BACKGROUND

Mucosal-associated invariant T (MAIT) cells are systemically depleted in human immunodeficiency virus type 1 (HIV-1) infected patients and are not replenished even after successful combined antiretroviral therapy (cART). This study aimed to identify the mechanism underlying MAIT cell depletion.

METHODS

In the present study, we applied flow cytometry, single-cell RNA sequencing and immunohistochemical staining to evaluate the characteristics of pyroptotic MAIT cells in a total of 127 HIV-1 infected individuals, including 69 treatment-naive patients, 28 complete responders, 15 immunological non-responders, and 15 elite controllers, at the Fifth Medical Center of Chinese PLA General Hospital, Beijing, China.

RESULTS

Single-cell transcriptomic profiles revealed that circulating MAIT cells from HIV-1 infected subjects were highly activated, with upregulation of pyroptosis-related genes. Further analysis revealed that increased frequencies of pyroptotic MAIT cells correlated with markers of systemic T-cell activation, microbial translocation, and intestinal damage in cART-naive patients and poor CD4⁺ T-cell recovery in long-term cART patients. Immunohistochemical staining revealed that MAIT cells in the gut mucosa of HIV-1 infected patients exhibited a strong active gasdermin-D (GSDMD, marker of pyroptosis) signal near the cavity side, suggesting that these MAIT cells underwent active pyroptosis in the colorectal mucosa. Increased levels of the proinflammatory cytokines interleukin-12 (IL-12) and IL-18 were observed in HIV-1 infected patients. In addition, activated MAIT cells exhibited an increased pyroptotic phenotype after being triggered by HIV-1 virions, T-cell receptor signals, IL-12 plus IL-18, and combinations of these factors, in vitro.

CONCLUSIONS

Activation-induced MAIT cell pyroptosis contributes to the loss of MAIT cells in HIV-1 infected patients, which could potentiate disease progression and poor immune reconstitution.

Dominant CD8+ T Cell Nucleocapsid Targeting in SARS-CoV-2 Infection and Broad Spike Targeting From Vaccination

CD8+ T cells have key protective roles in many viral infections. While an overall Th1-biased cellular immune response against SARS-CoV-2 has been demonstrated, most reports of anti-SARS-CoV-2 cellular immunity have evaluated bulk T cells using pools of predicted epitopes, without clear delineation of the CD8+ subset and its magnitude and targeting. In recently infected persons (mean 29.8 days after COVID-19 symptom onset), we confirm a Th1 bias (and a novel IL-4-producing population of unclear significance) by flow cytometry, which does not correlate to antibody responses against the receptor binding domain. Evaluating isolated CD8+ T cells in more detail by IFN-γ ELISpot assays, responses against spike, nucleocapsid, matrix, and envelope proteins average 396, 901, 296, and 0 spot-forming cells (SFC) per million, targeting 1.4, 1.5, 0.59, and 0.0 epitope regions respectively. Nucleocapsid targeting is dominant in terms of magnitude, breadth, and density of targeting. The magnitude of responses drops rapidly post-infection; nucleocapsid targeting is most sustained, and vaccination selectively boosts spike targeting. In SARS-CoV-2-naïve persons, evaluation of the anti-spike CD8+ T cell response soon after vaccination (mean 11.3 days) yields anti-spike CD8+ T cell responses averaging 2,463 SFC/million against 4.2 epitope regions, and targeting mirrors that seen in infected persons. These findings provide greater clarity on CD8+ T cell anti-SARS-CoV-2 targeting, breadth, and persistence, suggesting that nucleocapsid inclusion in vaccines could broaden coverage and durability.

Preferential and persistent impact of acute HIV-1 infection on CD4+ iNKT cells in colonic mucosa

Evidence suggests that HIV-1 disease progression is determined in the early stages of infection. Here, preinfection invariant natural killer T (iNKT) cell levels were predictive of the peak viral load during acute HIV-1 infection (AHI). Furthermore, iNKT cells were preferentially lost in AHI. This was particularly striking in the colonic mucosa, where iNKT cells were depleted more profoundly than conventional CD4⁺ T cells. The initiation of antiretroviral therapy during AHI-prevented iNKT cell dysregulation in peripheral blood but not in the colonic mucosa. Overall, our results support a model in which iNKT cells are early and preferential targets for HIV-1 infection during AHI.

Acute HIV-1 infection (AHI) results in the widespread depletion of CD4⁺ T cells in peripheral blood and gut mucosal tissue. However, the impact on the predominantly CD4⁺ immunoregulatory invariant natural killer T (iNKT) cells during AHI remains unknown. Here, iNKT cells from peripheral blood and colonic mucosa were investigated during treated and untreated AHI. iNKT cells in blood were activated and rapidly depleted in untreated AHI. At the time of peak HIV-1 viral load, these cells showed the elevated expression of cell death–associated transcripts compared to preinfection. Residual peripheral iNKT cells suffered a diminished responsiveness to in vitro stimulation early into chronic infection. Additionally, HIV-1 DNA, as well as spliced and unspliced viral RNA, were detected in iNKT cells isolated from blood, indicating the active infection of these cells in vivo. The loss of iNKT cells occurred from Fiebig stage III in the colonic mucosa, and these cells were not restored to normal levels after initiation of ART during AHI. CD4⁺ iNKT cells were depleted faster and more profoundly than conventional CD4⁺ T cells, and the preferential infection of CD4⁺ iNKT cells over conventional CD4⁺ T cells was confirmed by in vitro infection experiments. In vitro data also provided evidence of latent infection in iNKT cells. Strikingly, preinfection levels of peripheral blood CD4⁺ iNKT cells correlated directly with the peak HIV-1 load. These findings support a model in which iNKT cells are early targets for HIV-1 infection, driving their rapid loss from circulation and colonic mucosa.

Novel in vitro invariant natural killer T cell functional assays

BACKGROUND

Invariant Natural Killer T (iNKT) cells are innate lymphocytes bridging the innate and adaptive immune systems and are critical first responders against cancer and infectious diseases. iNKT cell phenotype and functionality are studied using in vitro stimulation assays assessing cytokine response and proliferation capabilities. The most common stimulant is the glycolipid α-Galactosyl Ceramide (α-GalCer), which stimulates iNKT cells when presented by CD1d, an MHC class I-like molecule expressed by antigen-presenting cells (APC). Another stimulant used is α-GalCer-loaded DimerX, a CD1d-Ig fusion protein which stimulates iNKT cells in an APC-independent fashion. Here, we demonstrate use of the PBS-57-loaded CD1d-tetramer as an APC-independent stimulant, where PBS-57 is an α-GalCer analogue.

METHODS

Using healthy fresh (n = 4) and frozen (n = 7) peripheral blood mononuclear cells (PBMCs), 10-h cytokine response (measuring IFN-γ production) and 10-day proliferation assays were performed assessing iNKT functionality using α-GalCer, CD1d-tetramer and DimerX stimulants.

RESULTS

All stimulants effectively induced IFN-γ production in both fresh and frozen PBMC. After the 10-h activation, CD1d-tetramer was significantly more effective than α-GalCer (p = 0.032) in inducing IFN-γ production in fresh PBMC and significantly more effective than both α-GalCer (p = 0.004) and DimerX (p = 0.021) in frozen PBMC. Similarly, all stimulants induced strong proliferation responses in all samples, although this was only significant in the frozen PBMC. No significant differences in proliferation were observed between stimulants.

SIGNIFICANCE

This study supports PBS-57-loaded CD1d-tetramer as an effective in vitro APC-independent iNKT cell stimulant, which is comparable to or even more effective than α-GalCer and DimerX. As CD1d is downregulated during infectious disease and cancer as evasion strategies, in vitro assays which are APC-independent can assist in providing objective insight to iNKT activation by not relying on CD1d expression by APCs. Overall, the novel CD1d-tetramer stimulation equips researchers with an expanded "toolkit" to successfully assess iNKT cell function.

Metabolomics as a Tool to Investigate HIV/TB Co-Infection

The HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome) and tuberculosis (TB) pandemics are perpetuated by a significant global burden of HIV/TB co-infection. The synergy between HIV and Mycobacterium tuberculosis (Mtb) during co-infection of a host is well established. While this synergy is known to be driven by immunological deterioration, the metabolic mechanisms thereof remain poorly understood. Metabolomics has been applied to study various aspects of HIV and Mtb infection separately, yielding insights into infection- and treatment-induced metabolic adaptations experienced by the host. Despite the contributions that metabolomics has made to the field, this approach has not yet been systematically applied to characterize the HIV/TB co-infected state. Considering that limited HIV/TB co-infection metabolomics studies have been published to date, this review briefly summarizes what is known regarding the HIV/TB co-infection synergism from a conventional and metabolomics perspective. It then explores metabolomics as a tool for the improved characterization of HIV/TB co-infection in the context of previously published human-related HIV infection and TB investigations, respectively as well as for addressing the gaps in existing knowledge based on the similarities and deviating trends reported in these HIV infection and TB studies.

Gut Innate Immunity and HIV Pathogenesis

PURPOSE OF REVIEW

In the gastro-intestinal tract, the complex network of multiple innate cell populations play critical roles not only as a first line of defense against invading pathogens and in driving adaptive immune responses but also in maintaining intestinal homeostasis. Here, we describe the roles of various innate immune cell populations in gut immunity and detail studies investigating the impact of acute and chronic HIV infection on these cell populations.

RECENT FINDINGS

Alterations in frequencies, phenotype and/or function of innate lymphoid cells, dendritic cells, macrophages, neutrophils, and innate-like T cells have been reported in people with HIV (PWH), with many of these features persisting despite anti-retroviral therapy and virological suppression. Dysregulated gut innate immunity in PWH is a feature of gut pathogenesis. A greater understanding of the mechanisms driving impairment in the multiple different gut innate immune cell populations and the downstream consequences of an altered innate immune response on host defense and gut homeostasis in PWH is needed to develop more effective HIV treatments and cure strategies.

Off the beaten path: Novel mRNA-nanoformulations for therapeutic vaccination against HIV

Over the last few years, immunotherapy for HIV in general and therapeutic vaccination in particular, has received a tremendous boost, both in preclinical research and in clinical applications. This interest is based on the evidence that the immune system plays a crucial role in controlling HIV infection, as shown for long-term non-progressors and elite controllers, and that immune responses can be manipulated towards targeting conserved epitopes. So far, the most successful approach has been vaccination with autologous dendritic cells (DCs) loaded ex vivo with antigens and activation signals. Although this approach offers much promise, it also comes with significant drawbacks such as the requirement of a specialized infrastructure and expertise, as well as major challenges for logistics and storage, making it extremely time consuming and costly. Therefore, methods are being developed to avoid the use of ex vivo generated, autologous DCs. One of these methods is based on mRNA for therapeutic vaccination. mRNA has proven to be a very promising vaccine platform, as the coding information for any desired protein, including antigens and activation signals, can be generated in a very short period of time, showing promise both as an off-the-shelf therapy and as a personalized approach. However, an important drawback of this approach is the short half-life of native mRNA, due to the presence of ambient RNases. In addition, proper immunization requires that the antigens are expressed, processed and presented at the right immunological site (e.g. the lymphoid tissues). An ambivalent aspect of mRNA as a vaccine is its capacity to induce type I interferons, which can have beneficial adjuvant effects, but also deleterious effects on mRNA stability and translation. Thus, proper formulation of the mRNA is crucially important. Many approaches for RNA formulation have already been tested, with mixed success. In this review we discuss the state-of-the-art and future trends for mRNA-nanoparticle formulations for HIV vaccination, both in the prophylactic and in the therapeutic setting.

Treatment with Commonly Used Antiretroviral Drugs Induces a Type I/III Interferon Signature in the Gut in the Absence of HIV Infection

Tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) are used for HIV treatment and prevention. Previously, we found that topical rectal tenofovir gel caused immunological changes in the mucosa. Here, we assess the effect of oral TDF/FTC in three HIV pre-exposure prophylaxis trials, two with gastrointestinal and one with cervicovaginal biopsies. TDF/FTC induces type I/III interferon-related (IFN I/III) genes in the gastrointestinal tract, but not blood, with strong correlations between the two independent rectal biopsy groups (Spearman r = 0.91) and between the rectum and duodenum (r = 0.81). Gene set testing also indicates stimulation of the type I/III pathways in the ectocervix and of cellular proliferation in the duodenum. mRNA sequencing, digital droplet PCR, proteomics, and immunofluorescence confirm IFN I/III pathway stimulation in the gastrointestinal tract. Thus, oral TDF/FTC stimulates an IFN I/III signature throughout the gut, which could increase antiviral efficacy but also cause chronic immune activation in HIV prevention and treatment settings.

Tenofovir (TDF) and emtricitabine (FTC) are used for HIV treatment and prevention

TDF/FTC induce a type I/III interferon-associated signature throughout the gut

IFN I/III induction is confirmed in independent clinical cohorts and 5 assay types

IFN I/III induction may contribute to anti-HIV efficacy and chronic immune activation

Perturbation of mucosal-associated invariant T cells and iNKT cells in HIV infection

PURPOSE OF REVIEW

To analyze the possible role that the 'unconventional' T-cell populations mucosal-associated invariant T cell (MAIT) and iNKT cells play during HIV infection and following antiretroviral therapy (ART) treatment.

RECENT FINDINGS

A substantial body of evidence now demonstrates that both MAIT and iNKT cells are depleted in blood during HIV infection. The depletion and dysfunction of MAIT and iNKT cells are only partially restored by suppressive ART, potentially contributing to HIV-related comorbidities.

SUMMARY

The deficiency and dysfunction of MAIT and iNKT T-cell subsets likely impact on immunity to important coinfections including Mycobacterium tuberculosis. This underscores the importance of research on restoring these unconventional T cells during HIV infection. Future studies in this field should address the challenge of studying tissue-resident cells, particularly in the gut, and better defining the determinants of MAIT/iNKT cell dysfunction. Such studies could have a significant impact on improving the immune function of HIV-infected individuals.

γδ T-cell responses during HIV infection and antiretroviral therapy

HIV infection is associated with a rapid and sustained inversion of the Vδ1:Vδ2 T‐cell ratio in peripheral blood. Studies of antiretroviral therapy (ART)‐treated cohorts suggest that ART is insufficient to reconstitute either the frequency or function of the γδ T‐cell subset. Recent advances are now beginning to shed light on the relationship between microbial translocation, chronic inflammation, immune ageing and γδ T‐cell immunology. Here, we review the impact of acute, chronic untreated and treated HIV infection on circulating and mucosal γδ T‐cell subsets and highlight novel approaches to harness γδ T cells as components of anti‐HIV immunotherapy.

Porcine Invariant Natural Killer T Cells: Functional Profiling and Dynamics in Steady State and Viral Infections

Pigs are important livestock and comprehensive understanding of their immune responses in infections is critical to improve vaccines and therapies. Moreover, similarities between human and swine physiology suggest that pigs are a superior animal model for immunological studies. However, paucity of experimental tools for a systematic analysis of the immune responses in pigs represent a major disadvantage. To evaluate the pig as a biomedical model and additionally expand the knowledge of rare immune cell populations in swine, we established a multicolor flow cytometry analysis platform of surface marker expression and cellular responses for porcine invariant Natural Killer T cells (iNKT). In humans, iNKT cells are among the first line defenders in various tissues, respond to CD1d-restricted antigens and become rapidly activated. Naïve porcine iNKT cells were CD3⁺/CD4⁻/CD8⁺ or CD3⁺/CD4⁻/CD8⁻ and displayed an effector- or memory-like phenotype (CD25⁺/ICOS⁺/CD5^hi/CD45RA⁻/CCR7 ^± /CD27⁺). Based on their expression of the transcription factors T bet and the iNKT cell-specific promyelocytic leukemia zinc finger protein (PLZF), porcine iNKT cells were differentiated into functional subsets. Analogous to human iNKT cells, in vitro stimulation of porcine leukocytes with the CD1d ligand α-galactosylceramide resulted in rapid iNKT cell proliferation, evidenced by an increase in frequency and Ki-67 expression. Moreover, this approach revealed CD25, CD5, ICOS, and the major histocompatibility complex class II (MHC II) as activation markers on porcine iNKT cells. Activated iNKT cells also expressed interferon-γ, upregulated perforin expression, and displayed degranulation. In steady state, iNKT cell frequency was highest in newborn piglets and decreased with age. Upon infection with two viruses of high relevance to swine and humans, iNKT cells expanded. Animals infected with African swine fever virus displayed an increase of iNKT cell frequency in peripheral blood, regional lymph nodes, and lungs. During Influenza A virus infection, iNKT cell percentage increased in blood, lung lymph nodes, and broncho-alveolar lavage. Our in-depth characterization of porcine iNKT cells contributes to a better understanding of porcine immune responses, thereby facilitating the design of innovative interventions against infectious diseases. Moreover, we provide new evidence that endorses the suitability of the pig as a biomedical model for iNKT cell research.

Mucosal Immunity in HIV/SIV Infection: T Cells, B Cells and Beyond

As our understanding of mucosal immunity increases, it is becoming clear that the host response to HIV-1 is more complex and nuanced than originally believed. The mucosal landscape is populated with a variety of specialized cell types whose functions include combating infectious agents while preserving commensal microbiota, maintaining barrier integrity, and ensuring immune homeostasis. Advances in multiparameter flow cytometry, gene expression analysis and bioinformatics have allowed more detailed characterization of these cell types and their roles in host defense than was previously possible. This review provides an overview of existing literature on immunity to HIV-1 and SIVmac in mucosal tissues of the female reproductive tract and the gastrointestinal tract, focusing on major effector cell populations and briefly summarizing new information on tissue resident memory T cells, T_reg, Th17, Th22 and innate lymphocytes (ILC), subsets that have been studied primarily in the gastrointestinal mucosa.

Functional Invariant Natural Killer T Cells Secreting Cytokines Are Associated With Non-Progressive Human Immunodeficiency Virus-1 Infection but Not With Suppressive Anti-Retroviral Treatment

Background

CD1d restricted invariant natural killer T (iNKT) cells are important in the activation and regulation of immune responses. Limited information is available regarding the functional role of iNKT cells in the human immunodeficiency virus (HIV) disease progression.

Methodology

α-GalCer stimulated iNKT cells were characterized for their functionality in terms of cytokine production (IFN-γ, TNF-α, IL-2, IL-4, and IL-21) and CD107a expression in HIV-1 infected [23 long-term non progressors (LTNPs), 28 progressors, 18 patients before and after suppressive anti-retroviral treatment (ART)] along with 25 HIV-1 negative subjects using multicolor flow cytometry.

Results

The functional profile of α-GalCer stimulated iNKT cells was similar in LTNPs and healthy controls. The number of LTNPs showing functional response in terms of secretion of cytokines (IFN-γ/IL2/TNF-α) and CD107a expression was significantly higher than seen in the progressors. The cytokine secretion by the stimulated iNKT cells was predominantly Th1 type. The frequencies of iNKT cells showing secretion of IFN-γ or IL2 or TNF-α or expression of CD107a were higher in LTNPs (p < 0.05 for all) and also significantly associated with lower plasma viral load (p value ranged from 0.04 to 0.003) and higher CD4 count (p value ranged from 0.02 to <0.0001). The functional profile of the iNKT cells before and after ART did not differ significantly indicating absence of restoration of iNKT cells functionality after suppressive ART. The IL-4 and IL-21 secreting iNKT cells were rare in all study populations.

Conclusion

The presence of functional iNKT cells secreting number of cytokines in non-progressive HIV infection could be one of the multiple factors required to achieve HIV control and hence have relevance in understanding the immunity in HIV infection. The failure of restoration of the iNKT functionality after ART should be potential area of future research.

Treatment-Naïve HIV-Infected Patients Have Fewer Gut-Homing β7 Memory CD4 T Cells than Healthy Controls

OBJECTIVES

The integrin α4β7 is the gut-homing receptor for lymphocytes. It also is an important co-receptor for human immunodeficiency virus (HIV) via glycoprotein (gp)120 binding. Depletion of gut cluster of differentiation (CD)4 T cells is linked to chronic inflammation in patients with HIV; however, measuring CD4 cells in the gut is invasive and not routine. As such, establishing a peripheral marker for CD4 depletion of the gut is needed. We hypothesized that α4β7 CD4 T cells are depleted in the peripheral blood of treatment-naïve patients with HIV compared with healthy controls.

METHODS

The study groups were treatment-naïve patients with HIV and uninfected controls. Subjects were included if they were 18 years or older with no history of opportunistic infections, active tuberculosis, or cancer. We collected peripheral blood and examined on whole blood using flow cytometry for the following cell surface markers: CD4, CD45RO, chemokine receptor type 5, C-X-C chemokine receptor type 4 (CXCR4), and the integrin β7. We collected demographic information, including age, sex, and ethnicity, as well as viral load (VL) and CD4 count. Two-sample t tests and Fisher exact tests were used to compare the differences between the two groups. Spearman correlation coefficients were calculated between CD4 count and log10^- VL and percentage of CD4⁺/CD45RO⁺/β7⁺ and log10^- VL in patients.

RESULTS

Twenty-two subjects were enrolled in the study (12 patients with HIV and 10 controls). There were no differences in age or sex between the two groups. There were more Hispanics and fewer Asians in the group comprising patients with HIV compared with the control group (7 vs 2 and 0 vs 4, P = 0.05, respectively). Patients infected with HIV had significantly lower frequencies of CD4⁺/CD45RO⁺/β7⁺ cells (median 12%, range 5-18 compared with uninfected controls: median 20%, range 11-26, P = 0.0007). There was a statistically significant difference in the percentage of CD4⁺/CD45RO⁺/C-X-C chemokine receptor type 4⁺ cells between patients (72%, range 60%-91%) compared with controls (79%, range 72%-94%, P = 0.04). The percentage of CD4⁺/CD45RO⁺/chemokine receptor type 5⁺ did not differ between the group of patients with HIV and the control groups (22%, range 11%-57% vs 27%, range 14%-31%; P = 0.8, respectively). There was no correlation between percentage of CD4⁺/CD45RO⁺/β⁺ cells and log10^- VL as measured by the Spearman correlation coefficient (r = 0.05, P = 0.88) in patients infected with HIV.

CONCLUSIONS

Memory CD4 β7⁺ cells are reduced significantly in the peripheral blood of untreated patients infected with HIV, which could be used as a noninvasive indicator of intestinal CD4 T cell loss and recovery. Further studies are needed to examine whether depletion of these CD4⁺/CD45RO⁺/β7⁺ cells in the peripheral blood parallels depletion in the gut of treatment-naïve patients with HIV and whether levels return to control levels after treatment.

Bacteroides are associated with GALT iNKT cell function and reduction of microbial translocation in HIV-1 infection

Invariant natural killer T (iNKT) cells are innate-like T cells that respond to lipid antigens presented by CD1d. These immunoregulatory cells have the capacity for rapid cytokine release after antigen recognition and are essential for the activation of multiple arms of the immune response. HIV-1 infection is associated with iNKT cell depletion in the peripheral blood; however, their role in the gastrointestinal-associated lymphoid tissue (GALT) is less well studied. Our results show that iNKT cells are found at a higher frequency in GALT compared with blood, particularly in HIV-1 elite controllers. The capacity of iNKT cells to produce interleukin-4 (IL-4) and IL-10 in the GALT was associated with less immune activation and lower markers of microbial translocation, whereas regulatory T cell frequency showed positive associations with immune activation. We hypothesized that the composition of the microbiota would influence iNKT cell frequency and function. We found positive associations between the abundance of several Bacteroides species and iNKT cell frequency and their capacity to produce IL-4 in the GALT but not in the blood. Overall, our results are consistent with the hypothesis that GALT iNKT cells, influenced by certain bacterial species, may have a key role in regulating immune activation in HIV-1 infection.

Th1 and Th17 proinflammatory profile characterizes invariant natural killer T cells in virologically suppressed HIV+ patients with low CD4+/CD8+ ratio

INTRODUCTION

Scanty data exist on the phenotype and functionality of invariant natural killer T (iNKT) cells in HIV-infected (HIV+) patients.

METHODS

By flow cytometry, we studied iNKT cells from 54 HIV+ patients who started combined antiretroviral therapy and had undetectable viral load for more than 1 year. Twenty-five maintained a CD4/CD8 ratio less than 0.4, whereas 29 reached a ratio more than 1.1; 32 age-matched and sex-matched patients were healthy controls (CTR).

RESULTS

Patients with low ratio had lower percentage of CD4 iNKT cells compared with patients with high ratio and higher CD8 iNKT cell percentage; double-negative iNKT cells were lower in HIV+ patients compared with CTR. Patients with low ratio had higher percentage of CD4 and double-negative iNKT cells expressing CD38 and HLA-DR compared with patients with high ratio. CD4 iNKT cells expressing PD-1 were higher in patients with CD4/CD8 ratio less than 0.4, whereas double-negative iNKT cells expressing PD-1 were lower compared with patients with ratio more than 1.1. Patients with low ratio had higher CD4 iNKT cells producing IL-17, CD8 iNKT cells producing IFN-γ, TNF-α or IFN-γ and TNF-α, and double-negative iNKT cells producing IL-17 or IL-17 and IFN-γ compared with CTR. Activated CD4 (or CD8) T cells correlated with activated CD4 (or CD8) iNKT cells, as well as the percentages of CD4 (or CD8) T cells expressing PD-1 was correlated to that of CD4 (or CD8) iNKT cells expressing PD-1.

CONCLUSION

Low CD4/CD8 ratio despite effective combined antiretroviral therapy is associated with altered iNKT cell subsets, enhanced activation, and prominent Th1/Th17 proinflammatory profile.

Innate Invariant NKT Cell Recognition of HIV-1-Infected Dendritic Cells Is an Early Detection Mechanism Targeted by Viral Immune Evasion

Invariant NKT (iNKT) cells are innate-like T cells that respond rapidly with a broad range of effector functions upon recognition of glycolipid Ags presented by CD1d. HIV-1 carries Nef- and Vpu-dependent mechanisms to interfere with CD1d surface expression, indirectly suggesting a role for iNKT cells in control of HIV-1 infection. In this study, we investigated whether iNKT cells can participate in the innate cell-mediated immune response to HIV-1. Infection of dendritic cells (DCs) with Nef- and Vpu-deficient HIV-1 induced upregulation of CD1d in a TLR7-dependent manner. Infection of DCs caused modulation of enzymes in the sphingolipid pathway and enhanced expression of the endogenous glucosylceramide Ag. Importantly, iNKT cells responded specifically to rare DCs productively infected with Nef- and Vpu-defective HIV-1. Transmitted founder viral isolates differed in their CD1d downregulation capacity, suggesting that diverse strains may be differentially successful in inhibiting this pathway. Furthermore, both iNKT cells and DCs expressing CD1d and HIV receptors resided in the female genital mucosa, a site where HIV-1 transmission occurs. Taken together, these findings suggest that innate iNKT cell sensing of HIV-1 infection in DCs is an early immune detection mechanism, which is independent of priming and adaptive recognition of viral Ag, and is actively targeted by Nef- and Vpu-dependent viral immune evasion mechanisms.

Exploring the feasibility of multi-site flow cytometric processing of gut associated lymphoid tissue with centralized data analysis for multi-site clinical trials

The purpose of this study was to determine whether the development of a standardized approach to the collection of intestinal tissue from healthy volunteers, isolation of gut associated lymphoid tissue mucosal mononuclear cells (MMC), and characterization of mucosal T cell phenotypes by flow cytometry was sufficient to minimize differences in the normative ranges of flow parameters generated at two trial sites. Forty healthy male study participants were enrolled in Pittsburgh and Los Angeles. MMC were isolated from rectal biopsies using the same biopsy acquisition and enzymatic digestion protocols. As an additional comparator, peripheral blood mononuclear cells (PBMC) were collected from the study participants. For quality control, cryopreserved PBMC from a single donor were supplied to both sites from a central repository (qPBMC). Using a jointly optimized standard operating procedure, cells were isolated from tissue and blood and stained with monoclonal antibodies targeted to T cell phenotypic markers. Site-specific flow data were analyzed by an independent center which analyzed all data from both sites. Ranges for frequencies for overall CD4+ and CD8+ T cells, derived from the qPBMC samples, were equivalent at both UCLA and MWRI. However, there were significant differences across sites for the majority of T cell activation and memory subsets in qPBMC as well as PBMC and MMC. Standardized protocols to collect, stain, and analyze MMC and PBMC, including centralized analysis, can reduce but not exclude variability in reporting flow data within multi-site studies. Based on these data, centralized processing, flow cytometry, and analysis of samples may provide more robust data across multi-site studies. Centralized processing requires either shipping of fresh samples or cryopreservation and the decision to perform centralized versus site processing needs to take into account the drawbacks and restrictions associated with each method.

Seminal plasma HIV-1 RNA concentration is strongly associated with altered levels of seminal plasma interferon-γ, interleukin-17, and interleukin-5

Seminal plasma HIV-1 RNA level is an important determinant of the risk of HIV-1 sexual transmission. We investigated potential associations between seminal plasma cytokine levels and viral concentration in the seminal plasma of HIV-1-infected men. This was a prospective, observational study of paired blood and semen samples from 18 HIV-1 chronically infected men off antiretroviral therapy. HIV-1 RNA levels and cytokine levels in seminal plasma and blood plasma were measured and analyzed using simple linear regressions to screen for associations between cytokines and seminal plasma HIV-1 levels. Forward stepwise regression was performed to construct the final multivariate model. The median HIV-1 RNA concentrations were 4.42 log10 copies/ml (IQR 2.98, 4.70) and 2.96 log10 copies/ml (IQR 2, 4.18) in blood and seminal plasma, respectively. In stepwise multivariate linear regression analysis, blood HIV-1 RNA level (p<0.0001) was most strongly associated with seminal plasma HIV-1 RNA level. After controlling for blood HIV-1 RNA level, seminal plasma HIV-1 RNA level was positively associated with interferon (IFN)-γ (p=0.03) and interleukin (IL)-17 (p=0.03) and negatively associated with IL-5 (p=0.0007) in seminal plasma. In addition to blood HIV-1 RNA level, cytokine profiles in the male genital tract are associated with HIV-1 RNA levels in semen. The Th1 and Th17 cytokines IFN-γ and IL-17 are associated with increased seminal plasma HIV-1 RNA, while the Th2 cytokine IL-5 is associated with decreased seminal plasma HIV-1 RNA. These results support the importance of genital tract immunomodulation in HIV-1 transmission.

Invariant natural killer T (iNKT) cells in HAART-treated, HIV-positive patients with bone and cardiovascular impairment

Background

Invariant Natural Killer T (iNKT) cells represent a determinant in the course of infections and diseases, however, their role in the pathogenesis of non-infectious co-morbidities in HIV-positive patients is unknown.

Methods

Flow cytometry was used to investigate iNKT cell frequency, phenotype and function in HIV-infected patients on HAART with bone and/or cardiovascular disorders and in HIV-positive controls free from co-morbidities.

Results

iNKT cells from subjects with bone and cardiovascular impairment expressed high levels of CD161 and predominantly secreted TNF. iNKT cells from individuals with bone disease alone did not show any distinctive phenotypical or functional characteristics. The functional capacity of iNKT cells in patients with cardiovascular disorder was impaired with no cytokine release upon stimulation.

Conclusion

iNKT cells may have a role in non-infectious co-morbidities in treated HIV disease, possibly through the exacerbation of inflammation. Further studies are needed to investigate iNKT cells in the pathogenesis of non-communicable disorders in HIV infection.

Immunomodulation of antiretroviral drug-suppressed chronic HIV-1 infection in an oral probiotic double-blind placebo-controlled trial

A putative source of inappropriate immune activation that drives human immunodeficiency virus (HIV)-1 immunopathogenesis is the gastrointestinal tract. Even with effective antiretroviral treatment, residual activation persists. We hypothesized that an oral probiotic could improve the residual immune activation in chronic treated HIV-1 infection, and tested a Bacillus coagulans GBI-30, 6086 capsule probiotic in HIV-1-infected persons with suppressed viremia on stable antiretroviral therapy in a 3-month double-blind placebo-controlled trial (10 probiotic, 7 placebo). The Gastrointestinal Symptom Rating Scale (GSRS) was administered monthly. Blood was tested at the start and end of placebo/probiotic administration for viremia, CD4(+) T cell percentage/concentration, soluble (s)CD14, soluble intestinal fatty acid binding protein, sCD163, D-dimer, C-reactive protein (CRP), interleukin-8, and tumor necrosis factor-α. All participants maintained viremia <40 RNA copies/ml. The probiotic was safe and well tolerated, and appeared to improve chronic gastrointestinal symptoms. Its administration was associated with a significant increase in the percentage of blood CD4(+) T cells compared to placebo (+2.8% versus -1.8%, p=0.018) although CD4(+) T cell concentrations were generally unchanged in both groups. None of the biomarkers showed significant changes on probiotic treatment or between-group differences in change (although significance was borderline for a greater sCD163 drop in the probiotic versus placebo group, p=0.05). Some biomarkers showed significant correlations to each other, particularly D-dimer with CRP and sCD14 with tumor necrosis factor (TNF)-α. These data demonstrate the safety and possible benefit of this probiotic for residual inflammation in treated HIV-1 infection, although further study will be required to determine the immune pathways involved.

NKT cell depletion in humans during early HIV infection

Natural killer T (NKT) cells bridge across innate and adaptive immune responses and have an important role in chronic viral infections such as human immunodeficiency virus (HIV). NKT cells are depleted during chronic HIV infection, but the timing, drivers and implications of this NKT cell depletion are poorly understood. We studied human peripheral blood NKT cell levels, phenotype and function in 31 HIV-infected subjects not on antiretroviral treatment from a mean of 4 months to 2 years after HIV infection. We found that peripheral CD4(+) NKT cells were substantially depleted and dysfunctional by 4 months after HIV infection. The depletion of CD4(+) NKT cells was more marked than the depletion of total CD4(+) T cells. Further, the early depletion of NKT cells correlated with CD4(+) T-cell decline, but not HIV viral levels. Levels of activated CD4(+) T cells correlated with the loss of NKT cells. Our studies suggest that the early loss of NKT cells is associated with subsequent immune destruction during HIV infection.

Natural killer T cells in advanced melanoma patients treated with tremelimumab

A significant barrier to effective immune clearance of cancer is loss of antitumor cytotoxic T cell activity. Antibodies to block pro-apoptotic/downmodulatory signals to T cells are currently being tested. Because invariant natural killer T cells (iNKT) can regulate the balance of Th1/Th2 cellular immune responses, we characterized the frequencies of circulating iNKT cell subsets in 21 patients with melanoma who received the anti-CTLA4 monoclonal antibody tremelimumab alone and 8 patients who received the antibody in combination with MART-1_26–35 peptide-pulsed dendritic cells (MART-1/DC). Blood T cell phenotypes and functionality were characterized by flow cytometry before and after treatment. iNKT cells exhibited the central memory phenotype and showed polyfunctional cytokine production. In the combination treatment group, high frequencies of pro-inflammatory Th1 iNKT CD8⁺ cells correlated with positive clinical responses. These results indicate that iNKT cells play a critical role in regulating effective antitumor T cell activity.