Genomic surveillance of omicron B.1.1.529 SARS-CoV-2 and its variants between December 2021 and March 2023 in Tamil Nadu, India-A state-wide prospective longitudinal study.

A state-wide prospective longitudinal investigation of the genomic surveillance of the omicron B.1.1.529 SARS-CoV-2 variant and its sublineages in Tamil Nadu, India, was conducted between December 2021 and March 2023. The study aimed to elucidate their mutational patterns and their genetic interrelationship in the Indian population. The study identified several unique mutations at different time-points, which likely could attribute to the changing disease characteristics, transmission, and pathogenicity attributes of omicron variants. The study found that the omicron variant is highly competent in its mutating potentials, and that it continues to evolve in the general population, likely escaping from natural as well as vaccine-induced immune responses. Our findings suggest that continuous surveillance of viral variants at the global scenario is warranted to undertake intervention measures against potentially precarious SARS-CoV-2 variants and their evolution.

Mucosal-Associated Invariant T Cells: Diplomatic Front-Runners in the Fight against Hepatitis B Virus Infection.

Mucosal-associated invariant T (MAIT) cells are a unique subset of innate-like T cells that bridge between innate and adaptive immunity. MAIT cells act like a 'biliary firewall' protecting the epithelial lining of the liver against pathogenic intruders. MAIT1 and MAIT17 subsets respond rapidly to pathogenic presence both in the liver as well as in the peripheral circulation. In addition to chronic hepatitis B virus (HBV) infection, MAIT cells also appear to serve as potential therapeutic targets in several other chronic ailments. Evidence indicates that MAIT cells have tissue repair functions also paving way for fibrotic changes during chronic HBV infection. Observations also suggest that HBV-hepatitis delta virus (HDV) co-infection disease progression is closely associated with loss of MAIT cells. Furthermore, reduction in the number of hepatic MAIT cells in patients with cirrhotic non-alcoholic fatty liver disease and HBV-associated primary liver cancer has also been reported. Given their concrete role against HBV disease progression, and has also become evident that the tumor microenvironment can cause functional impairment of MAIT cells. Here, we reviewed the protective and the pathological role of MAIT cells in chronic HBV infection and certain other related medical conditions based on the understanding that an optimal functioning of the MAIT cell arsenal is key to a "host-friendly" immune defense against HBV disease progression.

A comparative study on the efficiency of commercial reverse transcriptase-Polymerase chain reaction kits for the detection of severe acute respiratory syndrome coronavirus 2 infections.

Background: Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) kits have been reliably employed for the diagnosis of coronavirus disease 2019 (COVID-19) by the detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA since the beginning of the disease outbreak. In consideration of reliable diagnosis, apart from RT-PCR, the isothermal nucleic acid amplification-based point-of-care automated kits have also been tagged as a simpler and rapid alternative to the conventional techniques. Currently, the availability of a better diagnostic method for COVID-19 when compared to RT-PCR is nil. The most important step in the detection of SARS-CoV-2 in a RT-PCR diagnostic laboratory is to identify and employ RT-PCR kits with higher sensitivity as well as specificity. Objectives: This study aimed to study commercially available RT-PCR kits for the detection of SARS-CoV-2 infections. Methods: The performance of seven different RT-PCR kits from different manufacturers used for diagnosis of COVID-19 in Govt Theni Medical College and Hospital, Theni, Tamil Nadu were analysed. Nasopharyngeal and oropharyngeal swabs were collected from patients and subjected to RT-PCR using these kits. Results and Conclusion: The sensitivities and batch effects of the assessed kits were slightly different for different targets, for SARS-CoV-2 detection in nasopharyngeal swab specimens. Examination of COVID-19 kits should be done using currently employed kits in routine diagnosis for better efficiency.

Human Immunodeficiency Virus-Human Pegivirus Coinfected Individuals Display Functional Mucosal-Associated Invariant T Cells and Follicular T Cells Irrespective of PD-1 Expression.

Human pegivirus (HPgV) appears to alter the prognosis of HIV disease by modulating T cell homeostasis, chemokine/cytokine production, and T cell activation. In this study, we evaluated if HPgV had any 'favorable' impact on the quantity and quality of T cells in HIV-infected individuals. T cell subsets such as CD4lo, CD4hi, and CD8+ T cells, CD4+ MAIT cells, CD8+ MAIT cells, follicular helper T (TFH) cells, and follicular cytotoxic T (TFC) cells were characterized based on the expression of markers associated with immune activation (CD69, ICOS), proliferation (ki67), cytokine production (TNF-α, IFN-γ), and exhaustion (PD-1). HIV+HPgV+ individuals had lower transaminase SGOT (liver) and GGT (biliary) in the plasma than those who were HPgV-. HIV/HPgV coinfection was significantly associated with increased absolute CD4+ T cell counts. HIV+HPgV+ and HIV+HPgV- individuals had highly activated T cell subsets with high expression of CD69 and ICOS on bulk CD4+ and CD8+ T cells, CD4+ MAIT cells, CD8+ MAIT cells, and CXCR5+CD4+ T cells and CXCR5+CD8+ T cells compared with healthy controls. Irrespective of immune activation markers, these cells also displayed higher levels of PD-1 on CD4+ T and CD8+ T cells . Exploring effector functionality based on mitogen stimulation demonstrated increased cytokine production by CD4+ MAIT and CD8+ MAIT cells. Decrease in absolute CD4+ T cell counts correlated positively with intracellular IFN-γ levels by CD4lo T cells, whereas increase of the same correlated negatively with TNF-α in the CD4lo T cells of HIV+HPgV+ individuals. HIV/HPgV coinfected individuals display functional CD4+ and CD8+ MAIT, TFH, and TFC cells irrespective of PD-1 expression.

Chronic Viral Infection Compromises the Quality of Circulating Mucosal-Associated Invariant T Cells and Follicular T Helper Cells via Expression of Inhibitory Receptors.

BACKGROUND: Chronic viral infection results in impaired immune responses rendering viral persistence. Here, we compared the quality of T-cell responses among chronic hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV)-infected individuals by examining the levels of expression of selected immune activation and exhaustion molecules on circulating MAIT cells and Tfh cells. METHODS: Cytokines were measured using a commercial Bio-plex Pro Human Cytokine Grp I Panel 17-plex kit (BioRad, Hercules, CA, USA). Inflammation was assessed by measuring an array of plasma cytokines, and phenotypic alterations in CD4+ T cells including circulating Tfh cells, CD8+ T cells, and TCR iVα7.2+ MAIT cells in chronic HBV, HCV, and HIV-infected patients and healthy controls. The cells were characterized based on markers pertaining to immune activation (CD69, ICOS, and CD27) proliferation (Ki67), cytokine production (TNF-α, IFN-γ) and exhaustion (PD-1). The cytokine levels and T cell phenotypes together with cell markers were correlated with surrogate markers of disease progression. RESULTS: The activation marker CD69 was significantly increased in CD4+hi T cells, while CD8+ MAIT cells producing IFN-γ were significantly increased in chronic HBV, HCV and HIV infections. Six cell phenotypes, viz., TNF-α+CD4+lo T cells, CD69+CD8+ T cells, CD69+CD4+ MAIT cells, PD-1+CD4+hi T cells, PD-1+CD8+ T cells, and Ki67+CD4+ MAIT cells, were independently associated with decelerating the plasma viral load (PVL). TNF-α levels showed a positive correlation with increase in cytokine levels and decrease in PVL. CONCLUSION: Chronic viral infection negatively impacts the quality of peripheral MAIT cells and Tfh cells via differential expression of both activating and inhibitory receptors.

Serosurveillance of dengue infection and correlation with mosquito pools for dengue virus positivity during the COVID-19 pandemic in Tamil Nadu, India - A state-wide cross-sectional cluster randomized community-based study.

Background: Dengue is a vector-borne viral disease impacting millions across the globe. Nevertheless, akin to many other diseases, reports indicated a decline in dengue incidence and seroprevalence during the COVID-19 pandemic (2020-22). This presumably could be attributed to reduced treatment-seeking rates, under-reporting, misdiagnosis, disrupted health services and reduced exposure to vectors due to lockdowns. Scientific evidence on dengue virus (DENV) disease during the COVID-19 pandemic is limited globally. Methods: A cross-sectional, randomized cluster sampling community-based survey was carried out to assess anti-dengue IgM and IgG and SARS-CoV-2 IgG seroprevalence across all 38 districts of Tamil Nadu, India. The prevalence of DENV in the Aedes mosquito pools during 2021 was analyzed and compared with previous and following years of vector surveillance for DENV by real-time PCR. Findings: Results implicate that both DENV-IgM and IgG seroprevalence and mosquito viral positivity were reduced across all the districts. A total of 13464 mosquito pools and 5577 human serum samples from 186 clusters were collected. Of these, 3·76% of mosquito pools were positive for DENV. In the human sera, 4·12% were positive for DENV IgM and 6·4% were positive for DENV IgG. The anti-SARS-CoV-2 antibody titres correlated with dengue seropositivity with a significant association whereas vaccination status significantly correlated with dengue IgM levels. Interpretation: Continuous monitoring of DENV seroprevalence, especially with the evolving variants of the SARS-CoV-2 virus and surge in COVID-19 cases will shed light on the transmission and therapeutic attributes of dengue infection.

Emergence of SARS-CoV-2 Omicron Variant JN.1 in Tamil Nadu, India - Clinical Characteristics and Novel Mutations.

In December 2023, we observed a notable shift in the COVID-19 landscape, when the JN.1 emerged as a predominant SARS-CoV-2 variant with a 95% incidence. We characterized the clinical profile, and genetic changes in JN.1, an emerging SARS-CoV-2 variant of interest. Whole genome sequencing was performed on SARS-CoV-2 positive samples, followed by sequence analysis. Mutations within the spike protein sequences were analyzed and compared with the previous lineages and sublineages of SARS-CoV-2, to identify the potential impact of these unique mutations on protein structure and possible functionality. Several unique and dynamic mutations were identified herein. Our data provides key insights into the emergence of newer variants of SARS-CoV-2 in our region and highlights the need for robust and sustained genomic surveillance of SARS-CoV-2.

Surrogate Biomarkers of Disease Progression in Human Pegivirus Seropositive Human Immunodeficiency Virus-Infected Individuals.

Scientific observations indicate that an actively prevailing systemic condition could alleviate the pathology of another disease. Human pegivirus (HPgV), a highly ubiquitous flavivirus is believed to be associated with slow human immunodeficiency virus (HIV) disease progression, and has seldom been linked to hepatic pathology. In this study, we investigated whether HPgV seropositivity had any impact on surrogate markers of HIV disease progression in a cohort of HIV-infected HPgV seropositive (n = 28) and seronegative (n = 12) individuals who were prospectively evaluated for absolute CD4+ T cell counts, plasma viral load (PVL), liver enzymes, and plasma cytokine levels. The HIV PVL was relatively lower in HPgV seropositive than in HPgV seronegative HIV-infected subjects. Clinical markers of hepatic injury were significantly low among HPgV seropositive HIV-infected participants. HPgV seropositive individuals showed significantly higher levels of interleukin-7 (IL-7), and although not significant, the levels of IL-6 were lower among HPgV seropositive subjects. Spearman correlation analysis showed that the absolute CD4+T cell count was inversely correlated with HIV PVL. Exposure to HPgV appears to have a positive prognostic impact on the levels of surrogate biomarkers of HIV disease progression.

Chronic viral infection compromises the quality of circulating mucosal-invariant T cells and follicular T helper cells via expression of both activating and inhibitory receptors.

Chronic viral infection results in impaired immune responses rendering viral persistence. Here, we investigated the role of immune activation and compared the quality of T-cell responses in chronic HBV, HCV, and HIV infections. Cytokines were measured using a commercial Bio-plex Pro Human Cytokine Grp I Panel 17-plex kit (BioRad, Hercules, CA, USA). Inflammation was assessed by measuring an array of plasma cytokines, and peripheral CD4+ T cells including circulating Tfh cells, CD8+ T cells, and TCR iVα7.2+ MAIT cells in chronic HBV, HCV, and HIV-infected patients and healthy controls. The cells were characterized based markers pertaining to immune activation (CD69, ICOS, and CD27) proliferation (Ki67), cytokine production (TNF-α, IFN-γ) and exhaustion (PD-1). The cytokine levels and T cell phenotypes together with cell markers were correlated with surrogate markers of disease progression. The activation marker CD69 was significantly increased in CD4+ hi T cells, while CD8+ MAIT cells expressing IFN-γ were significantly increased in chronic HBV, HCV and HIV infections. Six cell phenotypes, viz., TNF-α+CD4+ lo T cells, CD69+CD8+ T cells, CD69+CD4+ MAIT cells, PD-1+CD4+ hi T cells, PD-1+CD8+ T cells, Ki67+CD4+ MAIT cells were independently associated with decelerating the plasma viral load (PVL). TNF-α levels showed a positive correlation with increase in cytokine levels and decrease in PVL. Chronic viral infection negatively impacts the quality of peripheral MAIT cells and TFH cells via expression of both activating and inhibitory receptors.

Plasma CXCL8 and MCP-1 as biomarkers of latent tuberculosis infection.

Background: Early detection of latent tuberculosis infection (LTBI) is critical to TB elimination in the current WHO vision of End Tuberculosis Strategy. Methods: We investigated whether detecting plasma cytokines could aid in diagnosing LTBI across household contacts (HHCs) positive for IGRA, HHCs negative for IGRA, and healthy controls. We also measured the plasma cytokines using a commercial Bio-Plex Pro Human Cytokine 17-plex assay. Results: Increased plasma CXCL8 and decreased MCP-1, TNF-α, and IFN-γ were associated with LTBI. Regression analysis showed that a combination of CXCL8 and MCP-1 increased the risk of LTBI among HHCs to 14-fold. Conclusions: We postulated that CXCL8 and MCP-1 could be the surrogate biomarkers of LTBI, especially in resource-limited settings.

Clinical characteristics and novel mutations of omicron subvariant XBB in Tamil Nadu, India - a cohort study.

Background: Despite the continued vaccination efforts, there had been a surge in breakthrough infections, and the emergence of the B.1.1.529 omicron variant of SARS-CoV-2 in India. There is a paucity of information globally on the role of newer XBB variants in community transmission. Here, we investigated the mutational patterns among hospitalised patients infected with the XBB omicron sub-variant, and checked if there was any association between the rise in the number of COVID-19 cases and the observed novel mutations in Tamil Nadu, India. Methods: Nasopharyngeal and oropharyngeal swabs, collected from symptomatic and asymptomatic COVID-19 patients were subjected to real-time PCR followed by Next Generation Sequencing (NGS) to rule out the ambiguity of mutations in viruses isolated from the patients (n = 98). Using the phylogenetic association, the mutational patterns were used to corroborate clinico-demographic characteristics and disease severity among the patients. Findings: Overall, we identified 43 mutations in the S gene across 98 sequences, of which two were novel mutations (A27S and T747I) that have not been reported previously with XBB sub-variants in the available literature. Additionally, the XBB sequences from our cohort had more mutations than omicron B.1.1.529. The phylogenetic analysis comprising six major branches clearly showed convergent evolution of XBB. Our data suggests that age, and underlying conditions (e.g., diabetes, hypertension, and cardiovascular disease) or secondary complications confers increased susceptibility to infection rather than vaccination status or prior exposure. Many vaccinated individuals showed evidence of a breakthrough infection, with XBB.3 being the predominant variant identified in the study population. Interpretation: Our study indicates that the XBB variant is highly evasive from available vaccines and may be more transmissible, and potentially could emerge as the 'next' predominant variant, which likely could overwhelm the existing variants of SARS-CoV-2 omicron variants. Funding: National Health Mission (India), SIDASARC, VINNMER (Sweden), ORIP/NIH (USA).

Plasma CXCL8 and MCP-1 as surrogate plasma biomarkers of latent tuberculosis infection among household contacts-A cross-sectional study.

Early detection of latent tuberculosis infection (LTBI) is critical to TB elimination in the current WHO vision of End Tuberculosis Strategy. The study investigates whether detecting plasma cytokines could aid in diagnosing LTBI across household contacts (HHCs) positive for IGRA, HHCs negative for IGRA, and healthy controls. The plasma cytokines were measured using a commercial Bio-Plex Pro Human Cytokine 17-plex assay. Increased plasma CXCL8 and decreased MCP-1, TNF-α, and IFN-γ were associated with LTBI. Regression analysis showed that a combination of CXCL8 and MCP-1 increased the risk of LTBI among HHCs to 14-fold. Our study suggests that CXCL-8 and MCP-1 could serve as the surrogate biomarkers of LTBI, particularly in resource-limited settings. Further laboratory investigations are warranted before extrapolating CXCL8 and MCP-1 for their usefulness as surrogate biomarkers of LTBI in resource-limited settings.

Plasma interleukin-7 correlation with human immunodeficiency virus RNA and CD4+ T cell counts, and interleukin-5 with circulating hepatitis B virus DNA may have implications in viral control.

Chronic viral infections represent a leading cause of global morbidity and mortality. Chronic HBV, HCV, and HIV infections result in cytokine perturbations that may hold key implications in understanding the complex disease mechanisms driving virus persistence and/or resolution. Here, we determined the levels of various plasma cytokines using a commercial Bio-Plex Luminex cytokine array in chronic HBV (n = 30), HCV (n = 15), and HIV (n = 40) infections and correlated with corresponding plasma viral loads (PVLs) and liver parameters. We observed differential perturbations in cytokine profiles among the study groups. The cytokines levels positively correlated with PVL and liver transaminases. The monocyte-derived cytokines viz., MIP-1ß, IL-8, and TNF-α, and Th2 cytokines like IL-4, IL-5, and IL-13 showed a better correlation with liver enzymes as compared to their corresponding PVLs. Our investigation also identified two cytokines viz., IL-5 and IL-7 that inversely correlated with HBV DNA and HIV PVLs, respectively. Regression analysis adjusted for age showed that every increase of IL-5 by one unit was associated with a reduction in HBV PVL by log10 0.4, whereas, every elevation by a unit of IL-7 was associated with decreased HIV PVL by log10 2.5. We also found that IL-7 levels correlated positively with absolute CD4+ T cell counts in HIV-infected patients. We concluded that plasma IL-5 and IL-7 may likely have a key role on viral control in HBV and HIV infections, respectively. A noteworthy increase in cytokines appears to bear protective and pathological significance, and indeed is reflective of the host's versatile immune armory against viral persistence.

Low SARS-CoV-2 viral load among vaccinated individuals infected with Delta B.1.617.2 and Omicron BA.1.1.529 but not with Omicron BA.1.1 and BA.2 variants.

The rapid spread of SARS-CoV-2 variants in the global population is indicative of the development of selective advantages in emerging virus strains. Here, we performed a case-control investigation of the clinical and demographic characteristics, clinical history, and virological markers to predict disease progression in hospitalized adults for COVID-19 between December 2021 and January 2022 in Chennai, India. COVID-19 diagnosis was made by a commercial TaqPath COVID-19 RT-PCR, and WGS was performed with the Ion Torrent Next Generation Sequencing System. High-quality (<5% of N) complete sequences of 73 Omicron B.1.1.529 variants were randomly selected for phylogenetic analysis. SARS-CoV-2 viral load, number of comorbidities, and severe disease presentation were independently associated with a shorter time-to-death. Strikingly, this was observed among individuals infected with Omicron BA.2 but not among those with the BA.1.1.529, BA.1.1, or the Delta B.1.617.2 variants. Phylogenetic analysis revealed severe cases predominantly clustering under the BA.2 lineage. Sequence analyses showed 30 mutation sites in BA.1.1.529 and 33 in BA.1.1. The mutations unique to BA.2 were T19I, L24S, P25del, P26del, A27S, V213G, T376A, D405N and R408S. Low SARS-CoV-2 viral load among vaccinated individuals infected with Delta B.1.617.2 and the Omicron BA.1.1.529 variant but not with Omicron BA.1.1 or BA.2 suggests that the newer strains are largely immune escape variants. The number of vaccine doses received was independently associated with increased odds of developing asymptomatic disease or recovery. We propose that the novel mutations reported herein could likely bear a significant impact on the clinical characteristics, disease progression, and epidemiological aspects of COVID-19. Surging rates of mutations and the emergence of eclectic variants of SARS-CoV-2 appear to impact disease dynamics.

Peripheral Follicular T Helper Cells and Mucosal-Associated Invariant T Cells Represent Activated Phenotypes During the Febrile Phase of Acute Dengue Virus Infection.

Peripheral follicular helper T (pTfh) cells represent specialized CD4+ T cells that help B cells to secrete antibodies. Dengue infection appears to cause immune activation in a wide array of immune cells. Herein, we investigated the signatures of immune activation of circulating Tfh cells and mucosal-associated invariant T (MAIT) cells in adult subjects with confirmed acute clinical dengue virus (DENV) infection by multiparametric flow cytometry. The acute DENV infection induced a significant expansion of highly activated pTfh cells and circulating MAIT cells during acute febrile infection. We found a higher frequency of activated PD-1+ Tfh cells and CD38+ pTfh cells in clinical DENV infection. We also found similar activated and expanding phenotypes of MAIT cells in the patients tested. The total counts of activated pTfh cells and circulating MAIT cells were higher in dengue patients relative to healthy controls. We concluded that pTfh cells and circulating MAIT cells represent activated phenotypes in acute DENV infection.

Molecular diversity of dengue virus serotypes 1-4 during an outbreak of acute dengue virus infection in Theni, India.

Background: Dengue fever (DF) is caused by an arthropod-borne dengue virus (DENV), has four serotypes and several genotypes. Although having clinical and epidemiological significance, the information on the circulating serotypes/genotypes is scarce in India. Materials and Methods: Blood specimens were collected from the patients suspected of DF and they are tested for DENV NS1 antigen and DENV IgM by ELISA. Antigen-positive samples were further serotyped by reverse transcriptase polymerase chain reaction. Representative samples from each serotype were sequenced to identify the genotypes. Results: All the four DENV serotypes were detected with the pre-dominance of DENV-1 (n = 49; 41.9%). Cases with multiple DENV serotype infections were also identified. Genotyping showed that DENV-1 belonging to genotype I, DENV-2 cosmopolitan (IV), DENV-3 genotype III and DENV-4 genotype I were active in the circulation during the outbreak in 2017. Conclusion: Our study documents the molecular characteristics of DENV circulating in our geographical locality. The detection of heterologous DENV serotypes highlights the importance of regular molecular monitoring for the early recognition of any switch in pre-dominant serotype.

Increase of Plasma TNF-α Is Associated with Decreased Levels of Blood Platelets in Clinical Dengue Infection.

Dengue virus (DENV) infection has become an increasingly common concern in tropical and subtropical regions. It has protean manifestations ranging from febrile phase to severe life-threatening illness. In this study, we estimated Th1 and Th2 cytokines and correlated the levels with dengue severity along with certain hematological and biochemical parameters. We also studied the seroprevalence of dengue between October and December 2017 at the Government Theni Medical College, India. Individuals with dengue fever (DF) were positive for either IgM or IgG, or both. The biochemical and hematological parameters along with plasma tumor necrosis factor alpha (TNF-α), interferon-gamma (IFN-γ), granulocyte monocyte-colony stimulating factor (GM-CSF), interleukin (IL)-13, IL-12p70, IL-10, IL-5, IL-4, and IL-2 cytokines were estimated. The prevalence of DF was 42.9% during the study period. IL-2, TNF-α, IL-4, and IL-10 levels were significantly elevated (p < 0.005) in patients with secondary DENV infection, whereas the level of IL-13 remained unaltered during both primary and secondary infections. No statistically significant difference was noticed with IL-12p70, IL-5, IFN-γ, and GM-CSF between the healthy controls and the primary and secondary DENV-infected groups. Increase of 1 unit of TNF-α was associated with a decrease of 160 units of blood platelets. Together, the study suggests that TNF-α could play a key role in the pathogenesis of dengue, and despite the decrease in platelet levels, it remains to be seen whether any other inflammatory cells regulate the levels of TNF-α in DENV infection.

Functional MAIT Cells Are Associated With Reduced Simian-Human Immunodeficiency Virus Infection.

Mucosa-associated invariant T (MAIT) cells are recently characterized as a novel subset of innate-like T cells that recognize microbial metabolites as presented by the MHC-1b-related protein MR1. The significance of MAIT cells in anti-bacterial defense is well-understood but not clear in viral infections such as SIV/HIV infection. Here we studied the phenotype, distribution, and function of MAIT cells and their association with plasma viral levels during chronic SHIV infection in rhesus macaques (RM). Two groups of healthy and chronic SHIV-infected macaques were characterized for MAIT cells in blood and mucosal tissues. Similar to human, we found a significant fraction of macaque T cells co-expressing MAIT cell markers CD161 and TCRVα-7.2 that correlated directly with macaque MR1 tetramer. These cells displayed memory phenotype and expressed high levels of IL-18R, CCR6, CD28, and CD95. During chronic infection, the frequency of MAIT cells are enriched in the blood but unaltered in the rectum; both blood and rectal MAIT cells displayed higher proliferative and cytotoxic phenotype post-SHIV infection. The frequency of MAIT cells in blood and rectum correlated inversely with plasma viral RNA levels and correlated directly with total CD4 T cells. MAIT cells respond to microbial products during chronic SHIV infection and correlated positively with serum immunoreactivity to flagellin levels. Tissue distribution analysis of MAIT cells during chronic infection showed significant enrichment in the non-lymphoid tissues (lung, rectum, and liver) compared to lymphoid tissues (spleen and LN), with higher levels of tissue-resident markers CD69 and CD103. Exogenous in vitro cytokine treatments during chronic SHIV infection revealed that IL-7 is important for the proliferation of MAIT cells, but IL-12 and IL-18 are important for their cytolytic function. Overall our results demonstrated that MAIT cells are enriched in blood but unaltered in the rectum during chronic SHIV infection, which displayed proliferative and functional phenotype that inversely correlated with SHIV plasma viral RNA levels. Treatment such as combined cytokine treatments could be beneficial for enhancing functional MAIT cells during chronic HIV infection in vivo.

Inhibitory natural killer cell receptor KIR3DL1 with its ligand Bw4 constraints HIV-1 disease among South Indians.

OBJECTIVE: To investigate the role of genotypic and phenotypic characteristics of killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA) class-1 ligands in HIV-1 disease progression. STUDY DESIGN AND METHODS: This is a nested case-control study including 347 HIV seropositive (HIV-1+) individuals from South India constituting 45 long-term nonprogressors (LTNPs) and 302 disease progressors. KIR genotyping was performed by multiplex sequence-specific primer-directed PCR (SSP-PCR). Phenotypic expressions of KIR3DL1/S1 was studied using multiparametric flow cytometry assay. HLA-Bw4 and Bw6 epitopes were determined by ARMS-PCR. HLA-Bw4I80, HLA-Bw4T80, HLA-C1, HLA-C2, and HLA-Aw4 were genotyped using SSP-PCR. Serum levels of IFN-γ was quantified using ELISA method. RESULTS: Overall, 37 different KIR genotypes were observed and the distribution of genotypes with AB-AB (OR = 2.2, P = 0.033) constellations showed significant increase among LTNPs. The frequencies of 3DL1-2DL3-2DL5 (OR = 2.2, Pc = 0.031), 3DL1-Bw4/Aw4 (OR = 2.49, Pc = 0.019), homozygous Bw4 (OR = 2.422, Pc = 0.011) were observed higher in LTNPs and 2DS1-2DS2-2DS3 (OR =  0.475, Pc = 0.03), homozygous Bw6 (OR = 0.413, Pc = 0.011) were higher in the disease progressors. Flow cytometry assay showed the increased expression and maintenance of 3DL1/S1+NK cells in LTNPs (P = 0.0001). Further the expansion of 3DS1+NK cells was higher than 3DL1+NK cells in the heterozygous 3DL1/S1 LTNPs (P = 0.001). CONCLUSION: The inhibitory receptor 3DL1 with Bw4 and its A-haplotype defining KIR genes (2DL3/L5) confers protection against HIV-1 disease progression. An increased expression and maintenance of 3DL1/S1+ natural killer cells may contribute to the efficient activation of the natural killer cells and subsequent long-term nonprogression (LTNPn) to the disease.

Hyper-Expression of PD-1 Is Associated with the Levels of Exhausted and Dysfunctional Phenotypes of Circulating CD161++TCR iVα7.2+ Mucosal-Associated Invariant T Cells in Chronic Hepatitis B Virus Infection.

Mucosal-associated invariant T (MAIT) cells, defined as CD161++TCR iVα7.2+ T cells, play an important role in the innate defense against bacterial infections, and their functionality is impaired in chronic viral infections. Here, we investigated the frequency and functional role of MAIT cells in chronic hepatitis B virus (HBV) infection. The peripheral CD3+CD161++TCR iVα7.2+ MAIT cells in chronic HBV-infected patients and healthy controls were phenotypically characterized based on CD57, PD-1, TIM-3, and CTLA-4, as well as HLA-DR and CD38 expression. The frequency of MAIT cells was significantly decreased among chronic HBV-infected individuals as compared to controls. Expression of CD57, PD-1, CTLA-4, as well as HLA-DR and CD38 on MAIT cells was significantly elevated in chronic HBV-infected individuals relative to controls. The percentage of T cell receptor (TCR) iVα7.2+ CD161+ MAIT cells did not correlate with HBV viral load but inversely with HLA-DR on CD4+ T cells and MAIT cells and with CD57 on CD8+ T cells suggesting that decrease of MAIT cells may not be attributed to direct infection by HBV but driven by HBV-induced chronic immune activation. The percentage and expression levels of PD-1 as well as CTLA-4 on MAIT cells inversely correlated with plasma HBV-DNA levels, which may suggest either a role for MAIT cells in the control of HBV infection or the effect of HBV replication in the liver on MAIT cell phenotype. We report that decrease of TCR iVα7.2+ MAIT cells in the peripheral blood and their functions were seemingly impaired in chronic HBV-infected patients likely because of the increased expression of PD-1.