Non‐neutralizing epitopes induce robust hepatitis C virus (HCV)‐specific antibody‐dependent CD56+ natural killer cell responses in chronic HCV‐infected patients

Natural killer (NK) cell‐mediated antibody‐dependent cellular cytotoxicity (NK‐ADCC) is of considerable interest in viral infection. However, little is known about NK‐ADCC responses in chronic hepatitis C virus (HCV) infection. In this study, impaired non‐specific antibody‐dependent CD56⁺ NK cell responses were observed in chronic HCV infection, as shown by decreased degranulation (extracellular CD107a expression) and interferon (IFN)‐γ production in response to antibody‐bound P815 cells. A peptide pool composed of epitopes recognized by anti‐HCV‐E1/E2 antibodies could induce pronounced HCV‐specific antibody‐dependent NK cell responses in sera from approximately half the chronic HCV carriers. Additionally, HCV‐specific epitopes with the capacity to induce robust NK‐ADCC activity were identified. Five linear NK‐ADCC epitopes (aa211‐aa217, aa384‐aa391, aa464‐aa475, aa544‐aa551 and aa648‐aa659 of the HCV envelope) were identified and do not overlap with putative linear neutralizing epitopes. This study revealed the dysfunctional characteristics of antibody‐dependent CD56⁺ NK cell responses in chronic HCV carriers. The key non‐neutralizing NK‐ADCC epitopes identified in this study may act as new targets for immunological intervention.     

Pol as a target for antibody dependent cellular cytotoxicity responses in HIV-1 infection

Antibody-dependent cellular cytotoxicity (ADCC) may assist in preventing HIV or delaying disease progression. Most prior studies have analysed Env-specific ADCC responses. We hypothesized that effective ADCC-based immunity may target conserved internal viral proteins such as Pol. We analysed the ability overlapping Pol peptides to induce activation of NK cells via ADCC. We prospectively studied ADCC responses in 83 HIV+ subjects followed for 3 years. Pol peptides were commonly targeted by ADCC responses in these chronically infected subjects (in 32 of the 83 subjects). However, Pol-specific ADCC responses declined over time and did not correlate with delayed HIV progression, measured by either baseline CD4 T cells, CD4 T cell loss over time, baseline viral load or the need to start antiretroviral therapy. Although Pol is frequently targeted by ADCC in HIV+ subjects, the strength or specificity of Pol-specific ADCC responses needs to be modulated to be effective in delaying HIV progression.     

CD4+ T cells recognize diverse epitopes within GAD65: implications for repertoire development and diabetes monitoring

Type 1 diabetes is associated with T‐cell responses to β‐cell antigens such as GAD65. Single T‐cell epitopes have been investigated for immune monitoring with some success, but multiple epitopes may be required to fully characterize responses in all subjects. We used a systematic approach to examine the diversity of the GAD65‐specific T‐cell repertoire in subjects with DRB1*04:01 haplotypes. Using class II tetramers, we observed responses to 15 GAD65 epitopes, including five novel epitopes. The majority were confirmed to be processed and presented. Upon stimulation with peptides, GAD‐specific responses were equally broad in subjects with diabetes and healthy controls in the presence or absence of CD25⁺ T cells, suggesting that a susceptible HLA is sufficient to generate a potentially autoreactive repertoire. Without depleting CD25⁺ cells, GAD_113–132 and GAD_265–284 responses were significantly stronger in subjects with diabetes. Although nearly every individual responded to at least one GAD65 epitope, most were seen in less than half of the subjects tested, suggesting that multiple epitopes are recommended for immune monitoring.     

Comprehensive analysis of HIV Gag‐specific IFN‐γ response in HIV‐1‐ and HIV‐2‐infected asymptomatic patients from a clinical cohort in The Gambia

Majority of HIV‐2‐infected individuals meet the criteria of long‐term non‐progressors. This has been linked to superior qualitative HIV‐2‐specific cellular immune responses that correlate with viral control. However, it is unknown whether this is due to frequent targeting of immunodominant Gag epitopes in HIV‐2 than HIV‐1 infection. We describe a comprehensive comparison of the magnitude, breadth and frequency of Gag responses and the degree of cross‐recognition of frequently targeted, immunodominant Gag peptides in a cross‐sectional study of asymptomatic HIV‐1‐ and HIV‐2‐infected individuals. Fresh PBMC from 20 HIV‐1‐ and 20 HIV‐2‐infected patients with similar CD4⁺ T‐cell counts (p=0.36) were stimulated with pools of HIV‐1 and/or HIV‐2 Gag peptides in an IFN‐γ ELISPOT assay. We found no difference in the cumulative magnitude of IFN‐γ responses (p=0.75) despite significantly lower plasma viral loads in HIV‐2‐infected people (p<0.0001). However, Gag211–290 was targeted with significantly higher magnitude in HIV‐2‐infected subjects (p=0.03) although this did not correlate with viral control. There was no difference in frequently targeted Gag peptides, the breadth, immunodominance or cross‐recognition of Gag peptide pools between the two infections. This suggests that other factors may control viral replication in HIV‐2 infection.     

Highly avid,oligoclonal, early‐differentiated antigen‐specific CD8+ T cells in chronic HIV‐2 infection

HIV‐1‐specific CD8⁺ T cells are present in most HIV‐1‐infected people and play an important role in controlling viral replication, but the characteristics of an effective HIV‐specific T‐cell response are largely unknown. The majority of HIV‐2‐infected people behave as long‐term non‐progressors while those who progress to AIDS do so in a manner indistinguishable from HIV‐1. A detailed study of HIV‐2 infection may identify protective immune responses. Robust gag p26‐specific T‐cell responses are elicited during HIV‐2 infection and correlate with control of viremia. In this study, we analyzed features of an HLA‐B^*3501‐restricted T‐cell response to HIV‐2 p26 that may contribute to virus control. In contrast to HIV‐1, HIV‐2‐specific T cells are at an early stage of differentiation (CD27⁺CD28⁺), a finding that relates directly to CD4⁺ T‐cell levels and inversely to immune activation. The cells demonstrate IFN‐γ secretion, oligoclonal T‐cell receptor Vβ gene segment usage, exceptional avidity and secretion of pro‐inflammatory cytokines. Despite the potentially strong selection pressure imposed on the virus by these cells, there was no evidence of HIV‐2 sequence evolution. We propose that in chronic HIV‐2 infection, the maintenance of early‐differentiated, highly avid CD8⁺ T cells could account for the non‐progressive course of disease. Such responses may be desirable from an HIV vaccine.     

The impact of concurrent HIV and type II diabetes on immune maturation,immune regulation and immune activation

Chronic immune activation and inflammation are constant findings in people living with HIV (PLWH) and contribute to the risk of non‐AIDS‐related morbidities, including cardiovascular diseases (CVD). Type 2 diabetes (T2D) is also characterized by immune activation and inflammation. We aimed to investigate the impact of concurrent HIV infection and T2D on T‐cell subsets. The study included PLWH with T2D (HIV+T2D+, N = 25) and without T2D (HIV+T2D?, N = 25) and HIV‐negative controls with T2D (HIV?T2D+, N = 22) and without T2D (HIV?T2D?, N = 28). All PLWH in the study were receiving combination antiretroviral therapy. We examined T‐cell homeostasis by determining T‐cell subsets (immune maturation, immune regulation and immune activation) using flow cytometry. HIV+T2D? had lower proportion of Tc17 cells and higher proportion of apoptotic cells than HIV?T2D?. When comparing HIV+T2D+ and HIV+T2D? a lower proportion of CD4+ recent thymic emigrants (RTE) was found (p = 0.028). Furthermore, HIV+T2D+ had a higher proportion of non‐suppressive CD4+ Tregs compared to HIV+T2D? (p = 0.010). In conclusion, even in the setting of treated HIV infection, distinct immunological alterations are found. In PLWH with concomitant T2D, most alterations in T‐cell subsets were related to HIV and only few differences were found between PLWH with and without diabetes.     

Detection of Epstein–Barr virus‐specific memory CD4+ T cells using a peptide‐based cultured enzyme‐linked immunospot assay

Approaches to evaluate T‐cell responses to Epstein–Barr virus (EBV) include enzyme‐linked immunospot (ELISPOT), which quantifies cells capable of immediate interferon‐γ secretion upon antigen stimulation. However, evaluation of expandable EBV‐specific memory T cells in an ELISPOT format has not been described previously. We quantified EBV‐specific T‐cell precursors with high proliferative capacity by using a peptide‐based cultured interferon‐γ ELISPOT assay. Standard and cultured ELISPOT responses to overlapping peptide pools (15‐mers overlapping by 11 amino acids) covering the lytic (BZLF1 and BMRF1) and latent (EBNA1, EBNA3a, EBNA3b, EBNA3c, LMP1 and LMP2) EBV proteins were evaluated in 20 healthy subjects with remote EBV infection and, for comparison, in four solid organ transplant recipients. Cultured ELISPOT responses to both lytic and latent EBV antigens were significantly higher than standard ELISPOT responses. The distribution of EBV‐specific T‐cell responses detected in healthy virus carriers showed more consistent cultured ELISPOT responses compared with standard ELISPOT responses. T‐cell responses quantified by cultured ELISPOT were mainly mediated by CD4⁺ T cells and a marked pattern of immunodominance to latent‐phase antigens (EBNA1 > EBNA3 family antigens > LMP2 > LMP1) was shown. Both the magnitude and distribution of EBV‐specific T‐cell responses were altered in solid organ transplant recipients; in particular, cultured ELISPOT responses were almost undetectable in a lung‐transplanted patient with EBV‐associated diseases. Analysis of T‐cell responses to EBV by ELISPOT assays might provide new insights into the pathogenesis of EBV‐related diseases and serve as new tools in the monitoring of EBV infection in immunocompromised patients.     

CD8+ Cell Anti-HIV Activity Rapidly Increases Upon Discontinuation of Early Antiretroviral Therapy

Introduction  CD8+ lymphocytes can suppress HIV replication without killing the infected cells. This CD8+ cell noncytotoxic anti-HIV response (CNAR) is associated with a beneficial clinical course. Materials and Methods  In this longitudinal study of 16 participants in the Options Project at UCSF, we measured the ability of CD8+ lymphocytes to suppress HIV replication in CD4+ cells during primary HIV infection, early antiretroviral therapy, and after treatment. Results and Discussion  CD8+ lymphocytes from subjects with untreated primary HIV-1 infection strongly suppressed HIV replication. Initiation of antiretroviral therapy during primary HIV-1 infection caused a marked decline in this CNAR. CD8+ cells from these subjects regained anti-HIV activity when early therapy was discontinued. The timing of the appearance of CD8+ cell anti-HIV activity directly correlated with the emergence of detectable virus levels. Maximal CNAR activity coincided with a decay in the kinetics of HIV replication. In addition, peak viral loads during treatment interruption were lower than pre-treatment virus levels (median reduction = 0.8 logs, p = 0.005) and CD4+ T cell counts were maintained for a 24-week period of follow-up. Conclusion  These results suggest that CNAR plays an important role in suppressing HIV replication in the setting of antiretroviral treatment interruption in HIV-infected individuals.     

Activation of NK cells by ADCC antibodies and HIV disease progression

Antibody-dependent cellular cytotoxicity (ADCC) is of considerable interest as an immune response that may facilitate the control of HIV infection. We studied ADCC responses prospectively in a cohort of 79 HIV-positive subjects followed up for a mean of 2.3 years without antiretroviral therapy. We used a novel assay of the ability of ADCC to activate natural killer (NK) cells, either from the same HIV-positive subject or from a healthy blood donor. We found that ADCC responses to either gp140 Env protein or HIV peptide pools were common in HIV-positive subjects when NK cells from the HIV-positive subject were used but did not correlate with markers of HIV disease progression. In contrast, ADCC responses to whole gp140 Env protein were strongly associated with a slower decline in CD4 T-cell loss when healthy donor NK cells were used as effectors. Our data had implications for induction of the most effective ADCC responses by HIV vaccines.     

Immune activation and antibody responses in non‐progressing elite controller individuals infected with HIV‐1

An extremely rare subset of patients infected with HIV‐1 designated as “non‐progressing elite controllers” appears to be able to maintain stable CD4⁺ T‐cell counts and a median plasma viremia below the detection limit of current ultrasensitive assays (<50–80 copies/ml of plasma) for >10 years in the absence of antiretroviral therapy. Lymphocyte subsets (CD4⁺, CD8⁺), immune activation markers (HLA‐DR⁺, CD38⁺, Beta‐2‐microglobulin), and HIV‐specific antibody responses were longitudinally examined in four non‐progressing elite controllers over more than 5 years. Two control groups of seronegative healthy individuals and untreated patients infected with HIV‐1 presenting detectable viremia were also included. None of the non‐progressing elite controllers displayed the high T‐cell activation levels generally seen in the seropositive individuals, keeping them within the normal range. Three non‐progressing elite controllers showed no significant immune system abnormalities when compared to seronegative individuals, displaying a low proportion of HIV‐1‐specific binding antibodies and low avidity index, similar to those observed for individuals infected recently with HIV‐1. One non‐progressing elite controller exhibited CD8⁺ T‐cell counts and β2‐M levels above normal ranges and developed a low but “mature” (high‐avidity) HIV‐1‐specific antibody response. Thus, the non‐progressing elite controllers are able to maintain normal T‐cell activation levels, which may contribute to prevent, or greatly reduce, the damage of the immune system typically induced by the HIV‐1 over time. They are, however, immunologically heterogeneous and very low levels of antigen exposure seem to occur in these patients, sufficient for sustaining a low, but detectable, HIV‐1‐specific immunity. J. Med. Virol. 81:1681–1690, 2009. © 2009 Wiley‐Liss, Inc.     

FcγRIII (CD16)‐mediated ADCC by NK cells is regulated by monocytes and FcγRII (CD32)

Monocytes are known to engage in reciprocal crosstalk with NK cells but their influence on NK‐cell‐associated antibody‐dependent cellular cytotoxicity (ADCC) is not well understood. We demonstrate that in humans FcγRIII (CD16)‐dependent ADCC by NK cells is considerably enhanced by monocytes, and that this effect is regulated by FcγRII (CD32) crosslinking in healthy individuals. It is known that during HIV‐1 infection, NK cells are known to express low levels of CD16 and exhibit reduced ADCC. We show that immune regulation of CD16‐mediated NK‐cell cytotoxicity by monocytes through CD32 engagement is substantially disturbed in chronic progressive HIV‐1 infection. Expression of activating isoform of CD32 represented a compensatory mechanism for reduced expression of CD16 on NK cells during HIV‐1 infection. As a result, the regulation of NK‐cell‐associated ADCC by monocytes is skewed and eventually constitutes a novel factor that contributes to HIV‐1‐associated immune deficiency, dysregulation and pathogenesis. Our data therefore provide evidence, for the first time, that in humans monocytes act as a rheostat for FcγRIII‐mediated NK‐cell functions maintaining a well‐balanced immune response.     

Novel HIV‐1 clade B candidate vaccines designed for HLA‐B*5101+ patients protected mice against chimaeric ecotropic HIV‐1 challenge

Novel candidate HIV‐1 vaccines have been constructed, which are tailor‐designed for HLA‐B^*5101⁺ patients infected with HIV‐1 clade B. These vaccines employ novel immunogen HIVB‐B^*5101 derived from consensus HIV‐1 clade B Gag p17 and p24 regions coupled to two Pol‐derived B^*5101‐restricted epitopes, which are together with a third B^*5101 epitope in Gag dominant in HIV‐1‐infected long‐term non‐progressing patients. Both plasmid DNA and modified vaccinia virus Ankara (MVA) vectors supported high expression levels of the HIVB‐B^*5101 immunogen in cultured cells. Heterologous DNA prime‐recombinant MVA boost regimen induced efficiently HIV‐1‐specific CD8⁺ T‐cell responses in BALB/c mice. These vaccine‐elicited T cells were multifunctional, killed efficiently target cells in vivo, and protected mice against challenge with ecotropic HIV‐1/NL4‐3 and ecotropic HIV‐1/NDK chimaeric viruses with HIV‐1 clade B or D backbones, respectively, and ecotropic murine leukemia virus gp80 envelope, and therefore did so in the absence of anti‐HIV‐1 gp120 antibodies. These results support further development of HIVB‐B^*5101 vaccines in combined heterologous‐modality regimens. The use of allele‐specific vaccines in humans is discussed in the context of other developments in the HIV‐1 field.     

Comparing HIV‐1 and HIV‐2 infection: Lessons for viral immunopathogenesis

HIV‐1 and HIV‐2 share many similarities including their basic gene arrangement, modes of transmission, intracellular replication pathways and clinical consequences: both result in AIDS. However, HIV‐2 is characterised by lower transmissibility and reduced likelihood of progression to AIDS. The underlying mechanistic differences between these two infections illuminate broader issues of retroviral pathogenesis, which remain incompletely understood. Comparisons between these two infections from epidemiological, clinical, virologic and immunologic viewpoints provide a basis for hypothesis generation and testing in this ‘natural experiment’ in viral pathogenesis. In terms of epidemiology, HIV‐2 remains largely confined to West Africa, whereas HIV‐1 extends worldwide. Clinically, HIV‐2 infected individuals seem to dichotomise, most remaining long‐term non‐progressors, whereas most HIV‐1 infected individuals progress. When clinical progression occurs, both diseases demonstrate very similar pathological processes, although progression in HIV‐2 occurs at higher CD4 counts. Plasma viral loads are consistently lower in HIV‐2, as are average levels of immune activation. Significant differences exist between the two infections in all components of the immune system. For example, cellular responses to HIV‐2 tend to be more polyfunctional and produce more IL‐2; humoral responses appear broader with lower magnitude intratype neutralisation responses; innate responses appear more robust, possibly through differential effects of tripartite motif protein isoform 5 alpha. Overall, the immune response to HIV‐2 appears more protective against disease progression suggesting that pivotal immune factors limit viral pathology. If such immune responses could be replicated or induced in HIV‐1 infected patients, they might extend survival and reduce requirements for antiretroviral therapy. Copyright © 2013 John Wiley & Sons, Ltd.     

HIV‐specific T‐cell responses detected in the genital tract of chronically HIV‐infected women are largely monofunctional

HIV‐specific T cells that produce interferon‐γ (IFN‐γ) are present in the genital tract of HIV‐infected women although these do not provide protection against genital HIV shedding. Because polyfunctional HIV‐specific T cells have been implicated in better HIV control than those with a single function, this study aimed to investigate whether polyfunctional T cells were present at the female genital mucosa. Cervical cytobrush‐derived T cells were obtained from chronically HIV‐infected women and compared with blood. CD3⁺ T cells from both compartments were expanded with Dynal anti‐CD3/CD28 expander beads for 14 days and flow cytometry was used to evaluate four T‐cell functions (CD107a, IFN‐γ, tumour necrosis factor‐α and macrophage inflammatory protein‐1β) from 16 women. The majority of Gag‐specific T‐cell responses in the female genital tract were monofunctional, although low frequencies of HIV Gag‐specific polyfunctional CD8⁺ T cells were detected at the cervix in 81·3% (13/16) of women. The ability of CD8⁺ T cells at both the cervix and in blood to express CD107a and to exhibit polyfunctional responses (two or more functions) following Gag stimulation was inversely associated with plasma viral load and positively associated with blood CD4 counts, suggesting that clinical status impacted on the functionality of HIV‐specific T cells at the mucosa, in a similar way to blood. HIV Gag‐specific cervical T cells were largely monofunctional. Polyfunctional T cells were detected at the cervix in women with high blood CD4 count and low plasma viral load but these did not protect from HIV genital shedding.     

Phenotypic characterization of regulatory T cells from antiretroviral‐naive HIV‐1‐infected people

Regulatory T (Treg) cells play a key role in dampening excessive immune activation. However, antiretroviral therapy (ART) ‐naive HIV‐1 infection maintains the immune system in a sustained state of activation that could alter both Treg cell surface markers and functions. As Treg cell surface markers are directly linked to their functions the overall objective of this study was to determine how ART‐naive HIV infection affects the phenotypic properties of Treg cells. Our data showed that in ART‐naive HIV‐1 infection, Treg cells are dominated by effector (CD45RA⁺ CD27⁻ CCR7⁻ CD62L⁻) and effector memory (CD45RA⁻ CD27⁻ CCR7⁻ CD62L⁻) cells. In contrast Treg cells from HIV‐negative individuals were mainly naive (CD45RA⁺ CD27⁺ CCR7⁺ CD62L⁺) and central memory (CD45RA⁻ CD27⁺ CCR7⁺ CD62L⁺) cells. Whereas effector and effector memory Treg cells showed enhanced expression of CD39 (P < 0·05), CD73 (P < 0·001), HLA‐DR and CD38 (P < 0·001); naive and central memory Treg cells showed a significant reduction in the expression of these markers. Overall Treg cell frequencies within total CD4⁺ T cells correlated positively with plasmatic HIV‐1 viral load. As increased viral load is associated with augmented CD4⁺ T‐cell destruction; this could suggest a resistance of peripheral Treg cells to HIV‐1 destruction. Hence the modulation of Treg cell phenotype and frequencies could be considered in designing immunotherapeutic strategies targeting immune system restoration during HIV‐1 infection.     

HIV gag‐specific immune response mediated by double negative (CD3+CD4−CD8−) T cells in HIV‐exposed seronegative individuals

Double negative (DN) T cells are CD3⁺, CD4^?, CD8^? cells with either T‐cell receptors (TCR) αβ or TCR γδ whose importance on protection against HIV infection is unknown. Since HIV‐exposed seronegative individuals correspond to an ideal group in whom correlates of protection are expected, the role of these cells was studied in 13 HIV‐serodiscordant couples in a stable relationship and reporting unprotected sexual intercourses. HIV‐specific immune responses mediated by DN T‐cells were evaluated by measuring intracellular IFNγ and MIP1β (CCL4) production in response to HIV‐Gag peptides. Thirty‐five healthy controls not exposed to HIV were tested similarly and used to define a threshold for positive responses. Interestingly, Gag‐specific DN T‐cell responses were found in 3/13 (23%) HIV‐exposed seronegative individuals (Group A), involving both DN/αβ⁺ and DN/γδ⁺ T‐cells through MIP1β and IFNγ production. 4/13 (30%) of partners infected with HIV (Group B) also showed Gag‐specific responses but were mediated exclusively by DN/γδ⁺ T‐cells, mainly through IFNγ production. DN T‐cells in Group A individuals can display differential HIV‐specific immune responses, which might contribute to the low susceptibility to infection with HIV shown by individuals in Group A. J. Med. Virol. 85:200–209, 2013. © 2012 Wiley Periodicals, Inc.     

Impaired natural killer cell‐induced antibody‐dependent cell‐mediated cytotoxicity is associated with human immunodeficiency virus‐1 disease progression

This study evaluates the correlation between natural killer (NK) cell function and human immunodeficiency virus (HIV)-1 disease progression in 133 untreated HIV-1 positive Chinese subjects, including 41 former plasma donors (FPDs) and 92 men who have sex with men, and 35 HIV-negative controls. Flow cytometry was used to determine the abundance of NK cell subsets, the expression levels of receptor species, human leucocyte antigen (HLA) genotyping and the antibody-dependent cell-mediated cytotoxicity (ADCC) responses of NK cells. We observed a decreased expression of CD56^dimCD16⁺ NK cell subsets and an increased expression of CD56⁻CD16⁺ with HIV-1 infection. As well, the expression of activating and inhibitory receptors increased significantly in NK cells, but CD16 receptor levels and the NKG2A/NKG2C ratio were down-regulated with HIV-1 infection. ADCC responses were higher in elite controllers than in all other groups, and were correlated inversely with HIV-1 viral load but correlated positively with CD4 count only in FPDs. Furthermore, individuals infected for < 1 year have lower ADCC responses than those infected for > 1 year. We also observed a negative association between ADCC responses and viral load in those who carry the HLA-A*30/B*13/Cw*06 haplotype. The positive correlation between CD16 expression and ADCC responses and a negative correlation trend between CD158a and ADCC responses were also observed (P = 0·058). Our results showed that the ADCC response is associated with patients'' disease status, receptor expression levels, infection time and specific HLA alleles, which indicates that ADCC may offer protective effects against HIV-1 infection.     

Minocycline attenuates HIV‐1 infection and suppresses chronic immune activation in humanized NOD/LtsZ‐scidIL‐2Rγnull mice

More than a quarter of a century of research has established chronic immune activation and dysfunctional T cells as central features of chronic HIV infection and subsequent immunodeficiency. Consequently, the search for a new immunomodulatory therapy that could reduce immune activation and improve T‐cell function has been increased. However, the lack of small animal models for in vivo HIV study has hampered progress. In the current study, we have investigated a model of cord blood haematopoietic progenitor cells (CB‐HPCs) ‐transplanted humanized NOD/LtsZ‐scidIL‐2Rγ^null mice in which progression of HIV infection is associated with widespread chronic immune activation and inflammation. Indeed, HIV infection in humanized NSG mice caused up‐regulation of several T‐cell immune activation markers such as CD38, HLA‐DR, CD69 and co‐receptor CCR5. T‐cell exhaustion markers PD‐1 and CTLA‐4 were found to be significantly up‐regulated on T cells. Moreover, increased plasmatic levels of lipopolysaccharide, sCD14 and interleukin‐10 were also observed in infected mice. Treatment with minocycline resulted in a significant decrease of expression of cellular and plasma immune activation markers, inhibition of HIV replication and improved T‐cell counts in HIV‐infected humanized NSG mice. The study demonstrates that minocycline could be an effective, low‐cost adjunctive treatment to regulate chronic immune activation and replication of HIV.     

CCR5 expression,haplotype and immune activation in protection from infection in HIV‐exposed uninfected individuals in HIV‐serodiscordant relationships

Several host factors have been implicated in resistance to HIV infection in individuals who remain HIV‐seronegative despite exposure. In a cohort of HIV‐serodiscordant heterosexual couples, we investigated interactions between systemic inflammation and T‐cell activation in resistance to HIV infection. Males and females in stable long‐term relationships with either HIV‐infected or uninfected partners were recruited, blood T‐cell activation (CD38, HLA‐DR, CCR5 and Ki67) and plasma cytokine concentrations were evaluated. The HIV‐negative exposed individuals had significantly lower frequencies of CCR5⁺ CD4⁺ and CD8⁺ T cells than unexposed individuals. Mean fluorescence intensity of CCR5 expression on CD4⁺ T cells was significantly lower in HIV‐negative exposed than unexposed individuals. Protective CCR5 haplotypes (HHA/HHF*2, HHF*2/HHF*2, HHC/HHF*2, HHA/HHA, HHA/HHC and HHA/HHD) tended to be over‐represented in exposed compared with unexposed individuals (38% versus 28%, P = 0·58) whereas deleterious genotypes (HHC/HHD, HHC/HHE, HHD/HHE, HHD/HHD and HHE/HHE) were under‐represented (26% versus 44%; P = 0·16). Plasma concentrations of interleukin‐2 (P = 0·02), interferon‐γ (P = 0·05) and granulocyte–macrophage colony‐stimulating factor (P = 0·006) were lower in exposed compared with unexposed individuals. Activation marker expression and systemic cytokine concentrations were not influenced by gender. We conclude that the dominant signature of resistance to HIV infection in this cohort of exposed but uninfected individuals was lower T‐cell CCR5 expression and plasma cytokine concentrations.     

Progressive CD127 down‐regulation correlates with increased apoptosis of CD8 T cells during chronic HIV‐1 infection

Chronic HIV‐1 infection can induce a significant decrease in CD127 expression on CD8 T cells, but the underlying mechanisms and immunological consequences are unclear. In this study, we investigated CD127 expression on CD8 T cells from a total of 51 HIV‐1‐infected subjects and 16 healthy individuals and analyzed the association between CD127 expression and CD8 T‐cell apoptosis in these HIV‐1‐infected subjects. We found that CD127 expression on total CD8 T cells was significantly down‐regulated, which was correlated with the increased CD8 T‐cell apoptosis and disease progression of chronic HIV‐1 infection. The in vitro addition of IL‐7 efficiently rescued the spontaneous apoptosis of CD8 T cells from HIV‐1‐infected individuals. IL‐7 stimulation also transiently down‐regulated CD127 expression, whereas some of the CD127^? CD8 T cells regained CD127 expression soon after IL‐7 was retracted from the incubation medium. Thus, IL‐7 stimulation reduced apoptosis of both CD127⁺ and CD127^?CD8 T cells to some degree. These data indicate that CD127 loss might impair IL‐7 signaling and increase CD8 T‐cell apoptosis during HIV‐1 infection. This study, therefore, will extend the notion that IL‐7 could be a good candidate for immunotherapy in HIV‐1‐infected patients.