Double-negative T cells during HIV/SIV infections: potential pinch hitters in the T-cell lineup

Innate adaptive immune cell dynamics in tonsillar tissues during chronic SIV infection

HIV-infected patients are at higher risk of developing oral mucosal infection and Epstein-Barr virus (EBV)-associated B cell malignancies. However, the potential role of oral immunity in the pathogenesis of oral lesions is unknown. Tonsils are oral-pharyngeal mucosal-associated lymphoid tissues that play an important role in oral mucosal immunity. In this study, we investigated the changes of innate and adaptive immune cells in macaque tonsils during chronic SIV infection. We found significantly higher frequencies of classical monocytes, CD3+CD56+ (NKT-like) cells, CD3+CD4+CD8+ (DP), and CD161+ CD4 T cells in tonsils from chronic infected compared to naïve animals. On the contrary, intermediate monocytes and CD3+CD4-CD8- (DN) cells were lower in chronic SIV-infected macaques. We further confirmed a recently described small B-cell subset, NKB cells, were higher during chronic infection. Furthermore, both adaptive and innate cells showed significantly higher TNF-α and cytotoxic marker CD107a, while IL-22 production was significantly reduced in innate and adaptive immune cells in chronic SIV-infected animals. A dramatic reduction of IFN-γ production by innate immune cells might indicate enhanced susceptibility to EBV infection and potential transformation of B cells in the tonsils. In summary, our observation shows that the SIV-associated immune responses are distinct in the tonsils compared to other mucosal tissues. Our data extends our understanding of the oral innate immune system during SIV infection and could aid future studies in evaluating the role of tonsillar immune cells during HIV-associated oral mucosal infections.

Cellular and molecular insights into incomplete immune recovery in HIV/AIDS patients

Highly active antiretroviral therapy (ART) can effectively inhibit virus replication and restore immune function in most people living with human immunodeficiency virus (HIV). However, an important proportion of patients fail to achieve a satisfactory increase in CD4⁺ T cell counts. This state is called incomplete immune reconstitution or immunological nonresponse (INR). Patients with INR have an increased risk of clinical progression and higher rates of mortality. Despite widespread attention to INR, the precise mechanisms remain unclear. In this review, we will discuss the alterations in the quantity and quality of CD4⁺ T as well as multiple immunocytes, changes in soluble molecules and cytokines, and their relationship with INR, aimed to provide cellular and molecular insights into incomplete immune reconstitution.

Frequency and functional profile of circulating TCRαβ+ double negative T cells in HIV/TB co-infection

BACKGROUND

Increased frequency of circulating double negative T (DNT, CD4^-CD8^-CD3⁺) cells with protective immune function has been observed in human immunodeficiency virus (HIV) infection and tuberculosis (TB). Here the role of circulating TCRαβ⁺ DNT cells was further investigated in HIV/TB co-infection.

METHODS

A cross-sectional study was conducted to investigate the frequency and functional profiles of peripheral TCRαβ⁺ DNT cells including apoptosis, chemokine and cytokine expression among healthy individuals and patients with TB, HIV infection and HIV/TB co-infection by cell surface staining and intracellular cytokine staining combined with flow cytometry.

RESULTS

Significantly increased frequency of TCRαβ⁺ DNT cells was observed in HIV/TB co-infection than that in TB (p < 0.001), HIV infection (p = 0.039) and healthy controls (p < 0.001). Compared with TB, HIV/TB co-infection had higher frequency of Fas expression (p = 0.007) and lower frequency of Annexin V expression on TCRαβ⁺ DNT cells (p = 0.049), and the frequency of Annexin V expression on Fas⁺TCRαβ⁺ DNT cells had no significant difference. TCRαβ⁺ DNT cells expressed less CCR5 in HIV/TB co-infection than that in TB (p = 0.014), and more CXCR4 in HIV/TB co-infection than that in HIV infection (p = 0.043). Compared with healthy controls, TB and HIV/TB co-infection had higher frequency of TCRαβ⁺ DNT cells secreting Granzyme A (p = 0.046; p = 0.005). In TB and HIV/TB co-infection, TCRαβ⁺ DNT cells secreted more granzyme A (p = 0.002; p = 0.002) and perforin (p < 0.001; p = 0.017) than CD4⁺ T cells but similar to CD8⁺ T cells.

CONCLUSIONS

Reduced apoptosis may take part in the mechanism of increased frequency of peripheral TCRαβ⁺ DNT cells in HIV/TB co-infection. TCRαβ⁺ DNT cells may play a cytotoxic T cells-like function in HIV/TB co-infection.

Double-negative T cells are increased in HIV-infected patients under antiretroviral therapy

Double-negative T (DNT) cells are a T-cell subset with a CD4-CD8- phenotype. They represent 1% to 5% of circulating lymphocytes, but an increase in this proportion can be found during lymphoproliferative and autoimmune diseases. This increase has also been reported in persons with HIV (PWH). The aim of this work was to better describe the proportion of DNT cell subset in PWH. We retrospectively collected 984 samples from PWH referred for lymphocyte immunophenotyping over a 7.5-year period. Quantification of DNT cells was performed by flow cytometry. DNT cell proportion was calculated by subtracting the CD4+ and CD8+ subsets proportions from the total of T cells. A total of 984 blood samples from PWH were collected. Mean CD4 T-cell count was decreased in such patients while DNT cell frequency was increased with a mean of 6.7%. More than half of the patients had a DNT cell proportion >5%. Patients with DNT cell proportion over 5% exhibited significantly reduced CD3+ and CD4+ T-cell counts, while CD8+ T-cell count was unchanged compared to patients with normal DNT cell rates. Interestingly, DNT cell percentage was negatively correlated with CD4 and CD3 T-cell counts in all included patients. Moreover, the DNT cell proportion was significantly increased in subjects with CD4+ T cells <200/mm3 compared to those with CD4+ T cells >200/mm3. Interestingly, DNT cell proportions were significantly higher in patients with high viral load compared with those presenting undetectable viral load. HIV infection is associated with an increase in DNT cell proportion. This increase is more frequent as the CD4 count is decreased and the viral load is increased. DNT cell subset should not be omitted when interpreting immunophenotyping in PWH as it appears to be associated with disease progression in patients under antiretroviral therapy.

Elevated Foxp3+ double-negative T cells are associated with disease progression during HIV infection

Persistent immune activation, which occurs during the whole course of HIV infection, plays a pivotal role in CD4⁺ T cells depletion and AIDS progression. Furthermore, immune activation is a key factor that leads to impaired immune reconstitution after long-term effective antiretroviral therapy (ART), and is even responsible for the increased risk of developing non-AIDS co-morbidities. Therefore, it’s imperative to identify an effective intervention targeting HIV-associated immune activation to improve disease management. Double negative T cells (DNT) were reported to provide immunosuppression during HIV infection, but the related mechanisms remained puzzled. Foxp3 endows Tregs with potent suppressive function to maintain immune homeostasis. However, whether DNT cells expressed Foxp3 and the accurate function of these cells urgently needed to be investigated. Here, we found that Foxp3⁺ DNT cells accumulated in untreated people living with HIV (PLWH) with CD4⁺ T cell count less than 200 cells/µl. Moreover, the frequency of Foxp3⁺ DNT cells was negatively correlated with CD4⁺ T cell count and CD4/CD8 ratio, and positively correlated with immune activation and systemic inflammation in PLWH. Of note, Foxp3⁺ DNT cells might exert suppressive regulation by increased expression of CD39, CD25, or vigorous proliferation (high levels of GITR and ki67) in ART-naive PLWH. Our study underlined the importance of Foxp3⁺ DNT cells in the HIV disease progression, and suggest that Foxp3⁺ DNT may be a potential target for clinical intervention for the control of immune activation during HIV infection.

Double-negative T cells: Setting the stage for disease control or progression

Double-negative (DN) T cells are present at relatively low frequencies in human peripheral blood, and are characterized as expressing the alpha-beta or gamma-delta T-cell receptor (TCR), but not the CD4 nor the CD8 co-receptors. Despite their low frequencies, these cells are potent producers of cytokines and, thus, are key orchestrators of immune responses. DN T cells were initially associated with induction of peripheral immunological tolerance and immunomodulatory activities related to disease prevention. However, other studies demonstrated that these cells can also display effector functions associated with pathology development. This apparent contradiction highlighted the heterogeneity of the DN T-cell population. Here, we review phenotypic and functional characteristics of DN T cells, emphasizing their role in human diseases. The need for developing biomarkers to facilitate the translation of studies from animal models to humans will also be discussed. Finally, we will examine DN T cells as promising therapeutic targets to prevent or inhibit human disease development.

Mild and Asymptomatic COVID-19 Convalescents Present Long-Term Endotype of Immunosuppression Associated With Neutrophil Subsets Possessing Regulatory Functions

The SARS-CoV-2 infection [coronavirus disease 2019 (COVID-19)] is associated with severe lymphopenia and impaired immune response, including expansion of myeloid cells with regulatory functions, e.g., so-called low-density neutrophils, containing granulocytic myeloid-derived suppressor cells (LDNs/PMN-MDSCs). These cells have been described in both infections and cancer and are known for their immunosuppressive activity. In the case of COVID-19, long-term complications have been frequently observed (long-COVID). In this context, we aimed to investigate the immune response of COVID-19 convalescents after a mild or asymptomatic course of disease. We enrolled 13 convalescents who underwent a mild or asymptomatic infection with SARS-CoV-2, confirmed by a positive result of the PCR test, and 13 healthy donors without SARS-CoV-2 infection in the past. Whole blood was used for T-cell subpopulation and LDNs/PMN-MDSCs analysis. LDNs/PMN-MDSCs and normal density neutrophils (NDNs) were sorted out by FACS and used for T-cell proliferation assay with autologous T cells activated with anti-CD3 mAb. Serum samples were used for the detection of anti-SARS-CoV-2 neutralizing IgG and GM-CSF concentration. Our results showed that in convalescents, even 3 months after infection, an elevated level of LDNs/PMN-MDSCs is still maintained in the blood, which correlates negatively with the level of CD8+ and double-negative T cells. Moreover, LDNs/PMN-MDSCs and NDNs showed a tendency for affecting the production of anti-SARS-CoV-2 S1 neutralizing antibodies. Surprisingly, our data showed that in addition to LDNs/PMN-MDSCs, NDNs from convalescents also inhibit proliferation of autologous T cells. Additionally, in the convalescent sera, we detected significantly higher concentrations of GM-CSF, indicating the role of emergency granulopoiesis. We conclude that in mild or asymptomatic COVID-19 convalescents, the neutrophil dysfunction, including propagation of PD-L1-positive LDNs/PMN-MDSCs and NDNs, is responsible for long-term endotype of immunosuppression.

HIV Infection and Persistence in Pulmonary Mucosal Double Negative T Cells In Vivo

The lungs are relatively unexplored anatomical human immunodeficiency virus (HIV) reservoirs in the antiretroviral therapy (ART) era. Double negative (DN) T cells are a subset of T cells that lack expression of CD4 and CD8 (CD4^- CD8^-) and may have both regulatory and effector functions during HIV infection. Notably, circulating DN T cells were previously described as cellular HIV reservoirs. Here, we undertook a thorough analysis of pulmonary versus blood DN T cells of people living with HIV (PLWH) under ART. Bronchoalveolar lavage (BAL) fluid and matched peripheral blood were collected from 35 PLWH on ART and 16 uninfected volunteers without respiratory symptoms. Both PLWH and HIV-negative (HIV^-) adults displayed higher frequencies of DN T cells in BAL versus blood, and these cells mostly exhibited an effector memory phenotype. In PLWH, pulmonary mucosal DN T cells expressed higher levels of HLA-DR and several cellular markers associated with HIV persistence (CCR6, CXCR3, and PD-1) than blood. We also observed that DN T cells were less senescent (CD28^- CD57⁺) and expressed less immunosuppressive ectonucleotidase (CD73/CD39), granzyme B, and perforin in the BAL fluid than in the blood of PLWH. Importantly, fluorescence-activated cell sorter (FACS)-sorted DN T cells from the BAL fluid of PLWH under suppressive ART harbored HIV DNA. Using the humanized bone marrow-liver-thymus (hu-BLT) mouse model of HIV infection, we observed higher infection frequencies of lung DN T cells than those of the blood and spleen in both early and late HIV infection. Overall, our findings show that HIV is seeded in pulmonary mucosal DN T cells early following infection and persists in these potential cellular HIV reservoirs even during long-term ART.IMPORTANCE Reservoirs of HIV during ART are the primary reasons why HIV/AIDS remains an incurable disease. Indeed, HIV remains latent and unreachable by antiretrovirals in cellular and anatomical sanctuaries, preventing its eradication. The lungs have received very little attention compared to other anatomical reservoirs despite being immunological effector sites exhibiting characteristics ideal for HIV persistence. Furthermore, PLWH suffer from a high burden of pulmonary non-opportunistic infections, suggesting impaired pulmonary immunity despite ART. Meanwhile, various immune cell populations have been proposed to be cellular reservoirs in blood, including CD4^- CD8^- DN T cells, a subset that may originate from CD4 downregulation by HIV proteins. The present study aims to describe DN T cells in human and humanized mice lungs in relation to intrapulmonary HIV burden. The characterization of DN T cells as cellular HIV reservoirs and the lungs as an anatomical HIV reservoir will contribute to the development of targeted HIV eradication strategies.

Comparative Analysis of Cellular Immune Responses in Conventional and SPF Olive Baboons (Papio anubis)

Olive baboons (P. anubis) have provided a useful model of human diseases and conditions, including cardiac, respiratory, and infectious diseases; diabetes; and involving genetics, immunology, aging, and xenotransplantation. The development of a immunologically defined SPF baboons has advanced research further, especially for studies involving the immune system and immunosuppression. In this study, we compare normal immunologic changes of PBMC subsets, and their function in age-matched conventional and SPF baboons. Our results revealed that both groups have comparable numbers of different lymphocyte subsets, but phenotypic differences in central and effector memory T-cell subsets are more pronounced in CD4+ T cells. Despite equal proportions of CD3+ T cells among the conventional and SPF baboons, PBMC from the conventional group showed greater proliferative responses to phytohemagglutinin and pokeweed mitogen and higher numbers of IFNγ-producing cells after stimulation with concanavalin A or pokeweed mitogen, whereas plasma levels of the inflammatory cytokine TNFα were significantly higher in SPF baboons. Exposure of PBMC from conventional baboons to various Toll-like (TLR) ligands, including TLR3, TLR4, and TLR8, yielded increased numbers of IFNγ producing cells, whereas PBMC from SPF baboons stimulated with TLR5 or TLR6 ligand had more IFNγ-producing cells. These findings suggest that although lymphocyte subsets share many phenotypic and functional similarities in conventional and SPF baboons, specific differences in the immune function of lymphocytes could differentially influence the quality and quantity of their innate and adaptive immune responses. These differences should be considered in interpreting experimental outcomes, specifically in studies measuring immunologic endpoints.

Decreased CD4+CD8low T cells in early HIV infection are associated with rapid disease progression

BACKGROUND

HIV rapid progressors (RPs) present with a rapid decline of CD4⁺ T cells within a few years of infection. Determining the underlying mechanisms throughout this decline is important to identify prognostic biomarkers and intervention strategies. Determining the numbers of CD4⁺ and CD8⁺ T cells is essential for monitoring the immune status of HIV infected patients. There are additional kinds of cell subtypes in T cells, but their relationship to the rapid progression of HIV disease is not well defined.

METHODS

Nineteen RPs and twenty-one chronic progressors (CPs) were enrolled in this study. Based on the intensity of CD4 and CD8 expression, different T cell subtypes were identified, including CD4⁺CD8⁺T cells, CD4^-CD8^- T cells, CD4⁺CD8^low T cells and CD4^-CD8^low T cells. Alterations in these T cell subtypes in early HIV infection (within 120 days of infection) between RPs and CPs were measured, and the relationships between these subtypes and HIV disease progression were investigated. In addition, expression of IFN-γ in T cell subtypes after PMA stimulation was analyzed by flow cytometry.

RESULTS

We found that during early HIV infection, CD4⁺CD8^low T cells both significantly decreased in numbers and percentages in RPs compared to CPs. Furthermore, baseline CD4⁺CD8^low T cells positively correlated not only with baseline CD4⁺T cells but also with CD4⁺T cells 12 months after infection. Moreover, survival analysis indicated that low levels of baseline CD4⁺CD8low T cells significantly accelerated the decline in CD4⁺ T cells as well as increased viral loads. CD4⁺CD8^low T cells secreted significantly more IFN-γ after PMA stimulation compared to CD4⁺CD8^-T cells and CD4^-CD8⁺T cells, which may be beneficial for the prevention of disease progression.

CONCLUSIONS

Our results identified that in early stage HIV-1 infection, a subtype of T cells, CD4⁺CD8^low, are associated with subsequent disease progression.

Peripheral immune cell markers in children with recurrent respiratory infections in the absence of primary immunodeficiency

The immune system of a child has a degree of immaturity that is maintained until 6–7 years of age. Immaturity may be due to age-related functional disorders in the immune response. A healthy child can contract a series of infections which contribute to the maturation of the immune system during the pre-pubertal period. If repeated infections with prolonged or severe complications occur during childhood, the presence of an immunodeficiency should then be considered. Much more frequent than primary immunodeficiency are recurrent infections (frequently involving the upper respiratory tract), which are less severe and occur under the conditions of an immune system with no apparent major defects. A child can present with 4 to 8 episodes of respiratory infections within a year, during the first 5 years of its life. The average duration of infection is 8 days and up to 2 weeks; if the child presents with 3 episodes of acute infections over a period of 6 months, the respiratory infections are then considered recurrent. The aim of this study was to identify the immunological changes or deviations that cause this clinical syndrome in children. For this purpose, 30 children with recurrent respiratory infections and 10 healthy children were included. Immunoglobulin levels were examined and immunophenotyping was performed. We found that the serum immunoglobulin levels were in the normal range in 70% of the children. On the contrary, our data revealed changes in peripheral cell populations, the most important being the decrease in the T-cluster of differentiation (CD)8⁺ and total B cell percentages and the increase in the number of memory B cells. The data obtained herein indicated that the decrease in the number of total B cells was mainly due to the decrease in the number of naive IgD⁺ B cells. On the whole, the findings of this study indicate that recurrent respiratory infections may be associated with an altered cellular immune response. In such situations, the investigation of immunological parameters, such as T and B cell subtypes could complete the clinical diagnosis and guide the treatment strategy, thus increasing the quality of life of patients.

Multivariate profiling of African green monkey and rhesus macaque T lymphocytes

The complexity of immune responses limits the usefulness of univariate methods in answering complex immunology questions. To demonstrate the utility of a multivariate approach, we employ such approach to compare T cells of African green monkeys (AGMs) and rhesus macaques (RMs). Among the most prominent distinguishing features we found were lower CD3 and higher CD28 surface expression in AGMs compared to RMs. After in vitro stimulation, a larger proportion of AGM T cells secreted cytokines, especially those producing more than one cytokine (i.e. multifunctional cells). To find out whether multifunctional responses associate with protection in other species, we compared T cells of cynomolgus macaques (CMs) infected with wild-type Simian Immunodeficiency Virus (SIV) to those of CMs infected (vaccinated) with a replication-defective virus. Wild-type SIV infection in macaques leads to simian Acquired Immunodeficiency Syndrome (AIDS), which does not happen in animals previously vaccinated with a replication-defective virus. Interestingly, after in vitro stimulation, multifunctional cells were more abundant among T cells of vaccinated CMs. Our results propose T-cell multifunctionality as a potentially useful marker of immunity, although additional verification is needed. Finally, we hope our multivariate model and its associated validation methods will inform future studies in the field of immunology.

Elevated CD3low double negative T lymphocyte is associated with pneumonia and its severity in pediatric patients

Background

Previous studies have shown that the adaptive immunity function of T cells in disease states correlates with CD3 surface expression closely. During routine assessment of TBNK subsets in peripheral blood of pediatric patients by flow cytometry, we noticed that variable expression levels of CD3 on CD3⁺CD4⁻CD8⁻ double-negative T (DNT) lymphocytes in different patients. The objective of this study was to assess the relationship of CD3 expression levels on DNT cells with disease severity.

Methods

In this prospective study, we investigated the frequencies of circulating CD4⁻CD8⁻ DNT cell subsets with CD3^low or CD3^high phenotype by flow cytometry in 76 pediatric patients with pneumonia, 55 patients with severe pneumonia (SP), and 29 healthy controls (Con).

Results

The numbers of circulating DNT cells were similar in all groups; however, the frequency of CD3^low DNT cell subsets was significantly increased in patients with pneumonia (p < 0.001) and SP (p < 0.001). The elevated CD3^low DNT cell frequency showed a positive correlation with the clinical severity of pneumonia. On sub-group analysis, the frequency of CD3^low DNT cells was only elevated in children with pneumonia aged <5 years, while no association was observed with the causative pathogen of pneumonia.

Conclusions

These findings suggest that CD3 expression levels on DNT cell subsets of peripheral lymphocytes may be a valuable biomarker for evaluation of immune response in pediatric infectious disease. CD3^low DNT cells were elevated in children with pneumonia aged <5 years, which indicates that it may be an important research target in pediatric infectious diseases.

Elevated peripheral blood B lymphocytes and CD3+CD4-CD8- T lymphocytes in patients with non-small cell lung cancer: A preliminary study on peripheral immune profile

It has been established that the tumor microenvironment (TME) has a crucial role in enabling tumors to evade from host immune responses. Previous studies demonstrated that tumor cells are not only able to reshape immune milieu at the tumor site, but also exert systemic effects, which has been demonstrated to be important for metastasis. At present, how the peripheral immune environment change in the tumor-bearing host is unclear. The present study identified a number of changes in the proportions of lymphocyte subpopulations and the levels of cytokines in patients with NSCLC, which may provide a preliminary profile of the immune environment in the peripheral blood of patients harboring a tumor. These findings expand on the present knowledge on how tumors can alter the immune system to benefit its growth and metastasis, which may provide a potential novel strategy for immunotherapy.

Low Double-Negative CD3+CD4-CD8- T Cells Are Associated with Incomplete Restoration of CD4+ T Cells and Higher Immune Activation in HIV-1 Immunological Non-Responders

Failure of immune reconstitution increases the risk of AIDS or non-AIDS related morbidity and mortality in HIV-1-infected patients. CD3⁺CD4⁻CD8⁻ T cells, which are usually described as double-negative (DN) T cells, display CD4-like helper and immunoregulatory functions. Here, we have measured the percentage of DN T cells in the immune reconstituted vs. non-immune reconstituted HIV-1-infected individuals. We observed that immunological non-responders (INRs) had a low number of DN T cells after long-term antiretroviral therapy (ART), and the number of these cells positively correlated with the CD4⁺ T cell count. The ART did not result in complete suppression of immune activation recorded by the percentage of CD38⁺HLA-DR⁺CD8⁺ T cells in INRs, and a strong inverse correlation was observed between DN T cells and immune activation. A low proportion of TGF-β1⁺DN T cells was found in INRs. Further mechanism study demonstrated that the level of TGF-β1-producing DN T cells and immune activation had a negative correlation after ART. Taken together, our study suggests that DN T cells control the immunological response in HIV-1-infected patients. These findings expand our understanding of the mechanism of immune reconstitution and could develop specific treatments to return the immune system to homeostasis following initiation of HIV-1 therapy.

Association of Epstein-Barr virus reactivation with the recovery of CD4/CD8 double-negative T lymphocytes after haploidentical hematopoietic stem cell transplantation

EBV infection is one of the life-threatening clinical complications in patients who underwent haploidentical hematopoietic stem cell transplantation (haploHSCT). Although immune recovery is recognized to be crucial for decreasing subsequent morbidity of infections, the link between T-cell recovery and EBV infection after haploHSCT remains elusive. We recently compared the influences of different doses of antithymocyte globulin conditioning on the T-cell reconstitution post haploHSCT and suggested that CD4^-CD8^-T cells might interact with the occurrence of EBV reactivation. In the current study, haploHSCT recipients with EBV-DNAemia (n=64) were compared with a control group without EBV reactivation (n=192), with regard to the recoveries of T-cell subpopulations. In contrast to other T-cell subpopulations, the median counts ofCD4^-CD8^-T cells in recipients with EBV-DNAemia were significantly lower than the control group at a serial time course (30, 90 and 180 days) after transplantation. Landmark studies further confirmed the correlation of CD4^-CD8^-T cells with the EBV infection. Multivariate analysis showed that hampered recovery of CD4^-CD8^-T cells and EBV reactivation were the independent risk factors to predict transplant-related mortality. Our findings may facilitate the intervention strategies to improve the overall survival of haploHSCT recipients.

Wide array of T-cell subpopulation alterations in patients with alcohol use disorders

BACKGROUND

Alcohol abuse impacts innate and adaptive immunity and predisposes to infections. However, prevalence and correlations of cellular immune alterations in large case series is underreported. We aimed to analyze quantitative alterations of T-lymphocyte subpopulations in patients with alcohol use disorder (AUD).

METHODS

cross-sectional study in patients admitted for detoxification between January 1, 2002 and December 31, 2012. Socio-demographic and alcohol use characteristics and blood samples for biochemistry, hematology and immune phenotype was obtained at admission.

RESULTS

238 patients (79.8%M) were eligible; age at admission was 43 years (interquartile range [IQR]: 38-51 years), the amount of alcohol consumption was 180 g/day (IQR: 120-200 g/day) and median duration of AUD was 18 years (IQR: 9-25 years). Compared to healthy individuals, 50% of patients had significantly fewer double-negative (DN) T-lymphocytes (<34 × 10(9)/L) and 23% had more double-positive (DP) T-cells (>52 × 10(9)/L). In addition, 24% of patients had high number of CD8(+) cells (>735 × 10(9)/L) and 13% had low CD4(+) cell counts (<600 × 10(9)/L). In multivariable analysis, age, sex, serum albumin, and current cocaine use were predictors of T-cell subpopulation alterations. Women were three-times (OR=3.5, 95%CI:1.3-9.5) more likely to present with higher DP T-lymphocytes than men.

CONCLUSIONS

Quantitative alterations of T-cell subpopulations are frequent in patients seeking treatment of AUD. Assessment of cellular immunity in this population may help to identify those at increased risk of immune alterations.

Tropism of human pegivirus (formerly known as GB virus C/hepatitis G virus) and host immunomodulation: insights into a highly successful viral infection

Human pegivirus (HPgV; originally called GB virus C/hepatitis G virus) is an RNA virus within the genus Pegivirus of the family Flaviviridae that commonly causes persistent infection. Worldwide, ~750 million people are actively infected (viraemic) and an estimated 0.75-1.5 billion people have evidence of prior HPgV infection. No causal association between HPgV and disease has been identified; however, several studies described a beneficial relationship between persistent HPgV infection and survival in individuals infected with human immunodeficiency virus. The beneficial effect appeared to be related to a reduction in host immune activation. HPgV replicates well in vivo (mean plasma viral loads typically >1×107 genome copies ml-1); however, the virus grows poorly in vitro and systems to study this virus are limited. Consequently, mechanisms of viral persistence and host immune modulation remain poorly characterized, and the primary permissive cell type(s) has not yet been identified. HPgV RNA is found in liver, spleen, bone marrow and PBMCs, including T- and B-lymphocytes, NK-cells, and monocytes, although the mechanism of cell-to-cell transmission is unclear. HPgV RNA is also present in serum microvesicles with properties of exosomes. These microvesicles are able to transmit viral RNA to PBMCs in vitro, resulting in productive infection. This review summarizes existing data on HPgV cellular tropism and the effect of HPgV on immune activation in various PBMCs, and discusses how this may influence viral persistence. We conclude that an increased understanding of HPgV replication and immune modulation may provide insights into persistent RNA viral infection of humans.

Immunogenetic characterization of a captive colony of sooty mangabeys (Cercocebus atys) used for SIV research

BACKGROUND

African non-human primates are SIV natural hosts and do not develop disease following infection. Understanding disease avoidance mechanisms in these species is important for HIV vaccine development. The largest captive population of sooty mangabeys, a SIV natural host species, resides at the Yerkes National Primate Research Center.

METHODS

Thirteen primer sets that amplify polymorphic microsatellite loci within the MHC region were used to genotype 144 animals. Immunogenetic Management Software (IMS) was used to identify MHC haplotypes and organize data.

RESULTS

Seventy-three haplotypes were identified. Limited haplotype diversity was observed in this population with 88.2% of included animals carrying one of 18 haplotypes. Differences in haplotype frequency were observed between SIV (+) and SIV (-) populations.

CONCLUSIONS

We have developed a novel tool for others to use in the analysis of the role of the MHC in a natural host non-human primate model species used for SIV research.

Double negative (DN) αβ T cells: misperception and overdue recognition

CD4(-)CD8(-)double negative (DN) αβ T cells are legitimate components of the normal immune system. However, they are poorly understood and largely ignored by immunologists because of their historical association with the lymphoproliferation that occurs in mice (lpr and gld) and humans (autoimmune lymphoproliferative syndromes patients) with impaired Fas-mediated apoptosis where they are considered abnormal T cells. We believe that the traditional view that DN T cells that cause lymphoproliferation (hereafter referred to as lpr DN T cells) are CD4 and CD8 T cells that lost their coreceptor, conceived more than two decades ago, is flawed and that conflating lpr DN T cells with DN T cells found in normal immune system (hereafter referred to as nDN T cells) is unnecessarily dampening interest of this potentially important cell type. To begin rectifying these misperceptions, we will revisit the traditional view of lpr DN T cells and show that it does not hold true in light of recent immunological advances. In lieu of it, we offer a new model proposing that Fas-mediated apoptosis actively removes normally existing DN T cells from the periphery and that impaired Fas-mediated apoptosis leads to accumulation of these cells rather than de novo generation of DN T cells from activated CD4 or CD8 T cells. By doing so, we hope to provoke a new discussion that may lead to a consensus about the origin of lpr DN T cells and regulation of their homeostasis by the Fas pathway and reignite wider interest in nDN T cells.

Enrichment of LAG-3, but not PD-1, on double negative T cells at the female genital tract

PROBLEM

The expression of inhibitory markers such as LAG-3 and PD-1 on T lymphocytes regulates immune function. Their expression at the genital mucosa is poorly understood, but regulation of immune activation at the female genital tract likely controls susceptibility to sexually transmitted infections.

METHOD OF STUDY

Cervical mononuclear cells were phenotyped by flow cytometry. Concentrations of cytokines were determined in cervical-vaginal lavage samples by bead array.

RESULTS

LAG-3 expression was significantly elevated at the genital mucosa and was associated with expression of CCR5 and CD69. Double negative (DN) T cells expressed the highest levels of LAG-3, but not PD-1, and were more activated than other T lymphocytes.

CONCLUSION

The elevated expression of LAG-3 at the genital tract suggests it may regulate T-cell activation, and identify cells susceptible to HIV infection. The enrichment of LAG-3 on DN T cells suggests LAG-3 may contribute to the immunoregulatory activity of these cells.

Double Negative (DN) [CD3⁺CD4⁻CD8⁻] T cells correlate with disease progression during HIV infection

Although double negative T (DNT) cells (CD3⁺CD4⁻CD8⁻) share some characteristics with T regulatory cells, the relationship between DNT cells and disease progression in HIV infection is unclear. In this study, we analyzed the relationship between DNT cells and disease progression during the first 2 years of HIV infection. We found that DNT cell numbers tended to decrease with disease progression. There was a positive correlation between DNT cells and CD4 counts. The DNT cell numbers were significantly lower in the high viral load group compared with the low viral load group. Therefore, we conclude that DNT cells correlated with disease progression in HIV infection. These data provide valuable information for further understanding of the role of DNT cells during HIV infection.

The contribution of non-conventional T cells and NK cells in the mycobacterial-specific IFNγ response in Bacille Calmette-Guérin (BCG)-immunized infants

BACKGROUND

The Mycobacterium bovis Bacille Calmette-Guérin (BCG) vaccine is given to >120 million infants each year worldwide. Most studies investigating the immune response to BCG have focused on adaptive immunity. However the importance of TCR-gamma/delta (γδ) T cells and NK cells in the mycobacterial-specific immune response is of increasing interest.

METHODS

Participants in four age-groups were BCG-immunized. Ten weeks later, in vitro BCG-stimulated blood was analyzed for NK and T cell markers, and intracellular IFNgamma (IFNγ) by flow cytometry. Total functional IFNγ response was calculated using integrated median fluorescence intensity (iMFI).

RESULTS

In infants and children, CD4 and CD4-CD8- (double-negative (DN)) T cells were the main IFNγ-expressing cells representing 43-56% and 27-37% of total CD3+ IFNγ+ T cells respectively. The iMFI was higher in DN T cells compared to CD4 T cells in all age groups, with the greatest differences seen in infants immunized at birth (p=0.002) or 2 months of age (p<0.0001). When NK cells were included in the analysis, they accounted for the majority of total IFNγ-expressing cells and, together with DN Vδ2 γδ T cells, had the highest iMFI in infants immunized at birth or 2 months of age.

CONCLUSION

In addition to CD4 T cells, NK cells and DN T cells, including Vδ2 γδ T cells, are the key populations producing IFNγ in response to BCG immunization in infants and children. This suggests that innate immunity and unconventional T cells play a greater role in the mycobacterial immune response than previously recognized and should be considered in the design and assessment of novel tuberculosis vaccines.

Multifunctional double-negative T cells in sooty mangabeys mediate T-helper functions irrespective of SIV infection

Studying SIV infection of natural host monkey species, such as sooty mangabeys, has provided insights into the immune changes associated with these nonprogressive infections. Mangabeys maintain immune health despite high viremia or the dramatic CD4 T cell depletion that can occur following multitropic SIV infection. Here we evaluate double-negative (DN)(CD3+CD4−CD8−) T cells that are resistant to SIV infection due to a lack of CD4 surface expression, for their potential to fulfill a role as helper T cells. We first determined that DN T cells are polyclonal and predominantly exhibit an effector memory phenotype (CD95+CD62L−). Microarray analysis of TCR (anti-CD3/CD28) stimulated DN T cells indicated that these cells are multifunctional and upregulate genes with marked similarity to CD4 T cells, such as immune genes associated with Th1 (IFNγ), Th2 (IL4, IL5, IL13, CD40L), Th17 (IL17, IL22) and T_FH (IL21, ICOS, IL6) function, chemokines such as CXCL9 and CXCL10 and transcription factors known to be actively regulated in CD4 T cells. Multifunctional T-helper cell responses were maintained in DN T cells from uninfected and SIV infected mangabeys and persisted in mangabeys exhibiting SIV mediated CD4 loss. Interestingly, TCR stimulation of DN T cells from SIV infected mangabeys results in a decreased upregulation of IFNγ and increased IL5 and IL13 expression compared to uninfected mangabeys. Evaluation of proliferative capacity of DN T cells in vivo (BrDU labeling) indicated that these cells maintain their ability to proliferate despite SIV infection, and express the homeostatic cytokine receptors CD25 (IL2 receptor) and CD127 (IL7 receptor). This study identifies the potential for a CD4-negative T cell subset that is refractory to SIV infection to perform T-helper functions in mangabeys and suggests that immune therapeutics designed to increase DN T cell function during HIV infection may have beneficial effects for the host immune system.

SIV infection of sooty mangabeys is generally characterized by maintained CD4 T cell levels and a lack of disease progression despite active virus replication. We have previously shown however, that dramatic loss of CD4 T cells can occur during SIV infection of mangabeys. This study investigates the potential for double negative (DN) T cells (which lack CD4 and CD8, and are refractory to SIV/HIV infection) to perform helper T cell functions. In our study, sooty mangabey DN T cells exhibited a memory phenotype and a diverse repertoire in their T cell receptors. Once stimulated, the DN T cells expressed multiple cytokines, indicating that they have the potential to function as helper T cells (a function normally undertaken by CD4+ T cells). In SIV infected mangabeys, DN T cells continue to function, proliferate in vivo, and maintain expression of homeostatic cytokine receptors on their surface. It is therefore likely that DN T cells have the potential to compensate for the loss of CD4 T cells during SIV infection. These studies indicate that increasing DN T cell levels and/or function during pathogenic HIV infection may provide one tangible component of a functional cure, and inhibit progression to clinical disease and AIDS