Anti-retroviral therapy reverses HIV-associated abnormalities in lymphocyte apoptosis

The objective of this study was to assess the role of anti-retroviral therapy (ART) on the susceptibility of peripheral blood lymphocytes (PBL) from HIV-1-infected individuals to activation-induced apoptosis and in comparison with changes in CD4 lymphocyte counts. Eleven symptomatic HIV⁺ patients were studied. Ex vivo apoptosis was measured in phytohaemagglutinin (PHA)-stimulated PBL and CD4 subsets by flow cytometry, at baseline and after 1 month (4–6 weeks) and 2/3 months of ART. Six patients had extended studies of the effects of therapy to a maximum of 21 months. Lymphocyte apoptosis was significantly elevated in HIV⁺ patients at baseline (median 22% compared with 7.5% in HIV^? risk-matched controls; P < 0.05). This decreased to control levels on ART (7.4% at 4–6 weeks, P < 0.01, and 6.2% at 8–12 weeks, P < 0.05, compared with baseline). Similar changes occurred in the CD4⁺ subpopulation. The decrease in apoptosis was maintained for several months, but the effect was rapidly lost if ART was discontinued. CD4 counts showed a reciprocal relationship to changes in apoptosis. The association of changes in apoptosis with those in CD4 counts suggests a link between programmed cell death and lymphocyte depletion. Apoptosis reduced in some individuals without any reduction in viral load, suggesting apoptosis may be influenced by factors in addition to the overall extent of HIV replication.     

Changes to the cytokine microenvironment in the genital tract mucosa of HIV+ women

As previous studies have indicated that genital tract mucosal T cell function may be impaired in HIV infection, we investigated the T cell cytokine mRNA in the genital tract mucosa of HIV-infected women to determine if there are alterations in the cytokine profile which may explain the T cell impairment. The in situ hybridization technique was used to investigate the T helper-1 (Th1: IL-2, interferon-gamma (IFN-γ)) and Th2 cytokine (IL-4, IL-5, IL-10) mRNA profile in cervical biopsies from 10 HIV⁺ and 10 HIV^? subjects. Cervical intraepithelial neoplasia (CIN) and genital infection had previously been excluded and the distribution of immunocompetent cells within the cervical mucosa was known for each subject. Non-parametric tests were used to compare the optical density (OD) of cytokine mRNA in the HIV⁺ and HIV^? groups. Comparisons were also made between peripheral CD4 lymphocyte counts, cervical CD4/CD8 T lymphocyte ratios and cytokine mRNA OD in HIV⁺ subjects. The HIV⁺ women had significantly higher mRNA OD for the Th2 cytokines IL-4, IL-5 and IL-10 than HIV^? women. There was also significantly lower IL-2 mRNA OD in the former group. HIV⁺ women had lower IFN-γ mRNA than HIV^? women, but the difference was not statistically significant. There was no correlation between cytokine mRNA OD and peripheral CD4 count or cervical CD4/CD8 ratio. The predominance of Th2 cytokines, which are immuno-inhibitory, in the cervical mucosa of HIV⁺ women may underlie the impaired cytotoxic potential observed in the CD8⁺ T lymphocytes and may contribute to the susceptibility of HIV-infected women to recurrent genital tract infections and cervical neoplasia.     

Increased expression of CD80, CD86 and CD70 on T cells from HIV-infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8⁺ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8⁺ T cells from HIV⁻ individuals cultured in the absence of CD4⁺ T cells. Addition of CD4⁺ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4⁺ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8⁺ T cells. Thus, to some extent, CD8⁺ T cells in HIV-infected individuals appeared to be refractory to CD4⁺ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8⁺ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.     

CD40 ligand and IFN-γ synergistically restore IL-12 production in HIV-infected patients

IL-12 production in HIV-infected (HIV⁺) individuals is severely impaired after stimulation by bacterial products or T cell-dependent stimuli. Because CD40-CD40 ligand (CD40L) interactions are the major mechanism involved in the T cell-dependent activation of antigen-presenting cells, we investigated whether this pathway was functional in HIV⁺ donors. CD40 expression was increased on freshly isolated monocytes from HIV⁺ individuals compared to HIV⁻ donors. However, equivalent CD40 expression was obtained in the two groups after cytokine stimulation. Since CD40 expression was intact in HIV⁺ donors' cells, we determined whether IL-12 production could be restored by providing exogenous T cell-dependent stimuli, CD40L and IFN-γ, at the time of bacterial stimulation. IL-12 production was not altered by CD40L alone, was increased by IFN-γ, and was synergistically restored to normal values by IFN-γ + CD40L. This combination was more efficient for enhancing IL-12 production than granulocyte-macrophage colony-stimulating factor + CD40L or neutralizing anti-IL-10 antibody + CD40L. CD40L did not affect IL-10 production, whereas IFN-γ significantly decreased it. This study demonstrates that the defect in IL-12 production by leukocytes from HIV⁺ donors can be overcome in vitro if the interacting cells are provided with the right T cell-dependent co-stimuli.     

Hepatitis C (HCV) genotype and viral titer distribution among Argentinean hemophilic patients in the presence or absence of human immunodeficiency virus (HIV) co-infection

Hepatits C (HCV) infection is frequent among hemophilic patients treated with non-inactivated factor-concentrates. Both HCV genotype and viral load have been suggested to be important prognostic markers of disease progression and treatment outcome. In addition, co-infection with the human immunodeficiency virus (HIV) has been associated with increased level of HCV replication and higher risk of developing liver failure. Thus, HCV genotype, viral load, and HIV co-infection are important factors in HCV infection. Using restriction fragment length polymorphism analysis (RFLP) and the branched-DNA (bDNA) assay, we retrospectively investigated the HCV genotypes and viral loads present in 59 Argentinean hemophiliacs, in the presence or absence of HIV infection. HCV genotype 1 was the predominant viral variant detected among HIV-negative (HIV⁻) (76%) and HIV-positive (HIV⁺) (82.5%) patients, followed by genotypes 3 (10.4%), 2(2%) and a small proportion of multiply co-infected patients including genotypes 4 and 5 (6.25%). HIV⁺ patients had higher plasma HCV RNA levels than HIV⁻ patients (88.4 ± 16.5 × 10⁵ Eq/ml vs. 24.7 ± 5.8 × 10⁵ Eq/ml) (P < 0.001); however, no correlation between HCV replication and level of immune suppression, evaluated by CD4⁺ T-cell measurement, was observed among HIV⁺ patients (r = 0.017). Abnormal and higher ALT levels were more frequently detected among HIV⁺ (93%; 123.6 ± 15.7 U/liter) than HIV⁻ (41%; 70.2 ± 24.2 U/liter) patients (P < 0.001; P < 0.05). Although we were able to confirm previous reports suggesting the existence of increased HCV replication in HIV/HCV co-infected hemophiliacs, our data did not support the conclusion that HIV-induced immune suppression is directly responsible for this phenomena. It is possible that other factors induced by HIV are responsible for the increased levels in HCV replication observed. J. Med. Virol. 52:219–225, 1997. © 1997 Wiley-Liss, Inc.     

Lysis of CD4+ lymphocytes by non-HLA-restricted cytotoxic T lymphoe from HIV-infected individuals

Individuals infected with HIV have elevated numbers of total and activated CD8⁺ lymphocytes in peripheral blood. CD8⁺ lymphocytes from HIV-infected individuals have been shown to mediate non-human histocompatibility-linked antigen (HLA)-restricted suppression of viral replication, HLA-restricted killing of cells expressing HIV antigens, and killing of uninfected lymphocytes. We studied CD8⁽ T lymphocytes that lysed autologous CD4+ lymphocytes, hetcrologous CD4¹ lymphocytes from HIV-infected individuals and uninfected CD4⁺ lymphocytes. Killing in all cases required T cell receptor (TCR)-mediated recognition or triggering. However, these CD8 cytotoxic T lymphocytes (CTL) killed HLA class I mismatched CD4* lymphocytes and CD4⁴ lymphocytes treated with a MoAb against HLA-A, B and C antigens (PA2.6) which blocks HLA class I-restricted killing. HLA class H-negativc CD4* T lymphoma cells (CEM.NK^R) were also killed by anti-CD3 inhibited CTL. Stimulation of peripheral blood lymphocytes (PBL) from HIV-infected individuals, but not uninfected controls, with concanavalin A (Con A) and IL-2, induced non-HLA-restricted TCR aft¹, CD8^f CTL which lysed CD4⁺ lymphocytes. Activation ofCD4’lymphocytes increased their susceptibility to CD8^f CTL-mediated lysis. In HIV infection, a population of non-HLA-restricted CTL which lyse activated CD4⁺ lymphocytes is expanded. The expansion of CTL with unusual characteristics is interesting, because the stimulus for this expansion is unknown. CTL which recognize activated CD4⁺ cells could play a role in immune regulation and the pathogenesis of A IDS.     

Neutrophil adhesion molecules in HIV disease

Neutrophil dysfunction in HIV disease is well described. We examined the expression of neutrophil adhesion molecules amongst 72 HIV-infected subjects using a whole blood flow cytometric assay with FITC- and R-PE-labelled isotype-specific MoAbs. We report lesser expression of CD11a (LFA-1) and L -selectin (CD62L) on the circulating neutrophils of HIV⁺ subjects compared with HIV^? controls. Expression of CD11b (Mac-1) was unchanged. Shedding of L -selectin and up-regulation of CD11b in response to in vitro stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP) were less in HIV⁺ compared with HIV^? subjects, most markedly in subjects with CD4 cell counts < 100 cells/mm³. These results suggest that neutrophil dysfunction in HIV disease, which increases with disease progression, may be attributable to dysregulated adhesion molecule expression.     

Inhibition of human immunodeficiency virus (HIV‐1) infection in human peripheral blood leucocytes‐SCID reconstituted mice by rapamycin

The capacity of the immunomodulatory drug rapamycin (RAPA) to inhibit replication of the CCR5 strain of human immunodeficiency virus (HIV) in vitro prompted us to test its effects in a murine preclinical model of HIV infection. RAPA (0·6 or 6 mg/kg body weight) or its vehicle were administered daily, per os, to SCID mice reconstituted with human peripheral blood leucocytes (hu‐PBL) starting 2 days before the intraperitoneal challenge with the R5 tropic SF162 strain of HIV‐1 (1000 50% tissue culture infective dose/ml). Relative to hu‐PBL‐SCID mice that received no treatment, HIV‐infected hu‐PBL‐SCID mice treated with the vehicle control for 3 weeks exhibited a severe depletion of CD4⁺ cells (90%), an increase in CD8⁺ cells and an inversion of the CD4⁺/CD8⁺ cell ratio. In contrast, treatment of HIV‐infected mice with RAPA prevented a decrease in CD4⁺ cells and the increase of CD8⁺ cells, thereby preserving the original CD4⁺ : CD8⁺ cell ratio. Viral infection also resulted in the detection of HIV‐DNA within peritoneal cells and spleen, and lymph node tissues of the vehicle‐treated mice within 3 weeks of the viral challenge. In contrast, treatment with RAPA decreased cellular provirus integration and reduced HIV‐RNA levels in the blood. Furthermore, in co‐cultivation assays, spleens from RAPA‐treated mice exhibited a reduced capacity for infecting allogeneic T cells which was dose‐dependent. These data show that RAPA possesses powerful anti‐viral activity against R5 strains of HIV in vivo and support the use of additional studies to evaluate the potential application of this drug in the management of HIV patients.     

CD8+ T cells and not CD4+ T cells are hyporesponsive to CD28- and CD40L-mediated activation in HIV-infected subjects

T cell dysfunction in HIV-infected subjects could be the consequence of altered sensitivity of CD4⁺ or CD8⁺ T cells to various costimulatory signals. Therefore, we studied proliferation and cytokine production in highly purified CD8⁺ and CD4⁺ T cells from HIV-infected and HIV⁻ subjects, induced by co-activation via cell-bound CD80, CD86 and CD40 or by allo-activation. Regardless of the nature of the first and the costimulatory signal, CD8⁺ T cells from patients proliferated consistently less than controls, while responses from CD4⁺ T cells were similar in patients and controls. This phenomenon was observed after ligation of CD28 combined with anti-CD3 or phorbol myristate acetate (PMA), but also after allogeneic stimulation and after activation by CD40 and anti-CD3. Anti-CD3 combined with CD80 or CD86 induced a mixed Th1/Th2-type cytokine profile in both CD4⁺ and CD8⁺ T cells from controls, whereas anti-CD3 plus CD40 induced only low levels of Th2-type cytokines and no interferon-gamma (IFN-γ) in CD4⁺ T cells. Compared with controls, CD4⁺ T cells from patients produced slightly lower levels of IL-10 but equal amounts of IFN-γ, IL-4 and IL-5, while CD8⁺ T cells from patients produced less of all cytokines tested. In conclusion, responses of purified CD4⁺ T cells from HIV⁺ subjects to various costimulatory pathways are relatively intact, whereas CD8⁺ T cells are hyporesponsive at the level of proliferation and cytokine production. A generalized intrinsic CD8⁺ T cell failure might contribute to viral and neoplastic complications of HIV infection.     

Partial recovery of senescence and differentiation disturbances in CD8+ T cell effector‐memory cells in HIV‐1 infection after initiation of anti‐retroviral treatment

Immune senescence as well as disturbed CD8⁺ T cell differentiation are a hallmark of chronic HIV infection. Here, we investigated to what extent immune senescence is reversible after initiation of anti‐retroviral treatment (ART). Peripheral blood mononuclear cells (PBMCs) from a cohort of HIV patients with different disease courses, including untreated viral controllers (n = 10), viral non‐controllers (n = 16) and patients on ART (n = 20), were analysed and compared to uninfected controls (n = 25) by flow cytometry on bulk and HIV‐specific major histocompatibility complex (MHC) class I tetramer⁺ CD8⁺ T cells for expression of the memory markers CCR7 and CD45RO, as well as the senescence marker CD57 and the differentiation and survival marker CD127. Furthermore, a subset of patients was analysed longitudinally before and after initiation of ART. Frequencies of CD57⁺CD8⁺ T cells decreased after initiation of ART in central memory (Tcm) but not in effector memory T cell populations (TemRO and TemRA). The frequency of CD127⁺CD8⁺ cells increased in Tcm and TemRO. We observed a reduction of CD127^– T cells in Tcm, TemRO and partially in TemRA subsets after initiation of ART. Importantly, HIV‐specific CD8⁺ TemRO cells predominantly displayed a CD127^–CD57⁺ phenotype in untreated HIV‐patients, whereas the CD127⁺CD57^– phenotype was under‐represented in these patients. The frequency of the CD127⁺CD57^–CD8⁺ T cell subpopulation correlated strongly with absolute CD4⁺ counts in HIV‐infected patients before and after initiation of ART. These findings can be interpreted as a phenotypical correlate of CD8⁺ memory T cell differentiation and the premature ‘ageing’ of the immune system, which was even observed in successfully virally suppressed HIV patients.     

Altered ex vivo balance between CD28+ and CD28− cells within HIV-specific CD8+ T cells of HIV-seropositive patients

The CD8⁺ CD28⁻ cell population in the blood of HIV-infected individuals is considerably expanded. Yet the cause of this expansion is not clear. The recent demonstration of identical TCR-rearranged genes in CD8⁺ CD28⁺ and CD8⁺ CD28⁻ expanded T cells of HIV-seropositive patients supports the hypothesis that these two subpopulations are phenotypic variants of the same lineage. To further elucidate the precise relationship between them, we measured the fraction of CD28⁺ and CD28⁻ T cell subsets in IFN-γ-producing CD8⁺ T cells by intracellular staining and cytofluorometry as a functional test for ex vivo recognition of epitopes derived from HIV-1, Epstein-Barr virus (EBV) and influenza virus. HIV-specific CD8⁺ T cells were predominantly CD28⁻ in all the eight HIV-seropositive subjects tested. In contrast, the anti-EBV and anti-influenza CD8⁺ T cells were mainly CD28⁺ in these patients as well as in HIV-seronegative individuals. This supports the notion that the CD8⁺ CD28⁻ hyperlymphocytosis observed in HIV infection is due mainly to chronic activation and differentiation of HIV-specific memory CD8⁺ CD28⁺ T cells into terminally differentiated CD8⁺ CD28⁻ lymphocytes, because of intense HIV-1 replication and without any important bystander activation. This clarification of the mechanisms underlying the CD8⁺ CD28⁻ expansion in HIV-induced pathogenesis may have important therapeutic implications.     

CD8+ CD28− T cells in vertically HIV-infected children

To evaluate whether vertical HIV infection interferes with the expression of CD28 on T lymphocytes, 25 HIV-infected children and 29 seroreverted children born to HIV⁺ mothers were studied. The percentage of CD28⁻ cells among CD8⁺ T lymphocytes was higher in HIV-infected children than in controls (P < 0.001). In fact, in HIV-infected children, this percentage was elevated from the first year of life, while in healthy seroreverted children, the proportion of CD28⁻ cells among CD8⁺ cells rose progressively with age (r = 0.49; P = 0.008). In HIV⁺ children, the CD8⁺ CD28⁻, but not CD8⁺ CD28⁺ cell proportion was significantly correlated with immunological markers of disease progression, such as CD4⁺ cell loss (r = −0.65; P < 0.001) and the level of in vitro spontaneous lymphocyte apoptosis (r = 0.53; P = 0.03).     

Generalized immune activation in pulmonary tuberculosis: co-activation with HIV infection

Parameters of immune activation/differentiation were studied in a group of newly diagnosed HIV⁻ and HIV⁺ pulmonary tuberculosis (TB) patients. Compared with controls, HLA-DR expression on both CD4 and CD8 T cells from the HIV⁻ TB patients was approximately doubled; HLA-DR on T cells from the HIV⁺ group was tripled. The monocytes from both groups of patients expressed abnormally high levels of the Fcγ receptors I and III. Serum levels of tumour necrosis factor-alpha (TNF-α), neopterin and β₂-microglobulin were increased in HIV⁻ and even more so in HIV⁺ TB patients. The expression of HLA-DR on T cell subsets and of FcγR on monocytes correlated with each other, but not with serum activation markers. This pattern of non-specific activation during TB infection may be associated with enhanced susceptibility to HIV infection.     

Superantigen activation of CD4+ and CD8+ T cells from HIV-infected subjects: role of costimulatory molecules and antigen-presenting cells (APC)

T cell receptor (TCR) triggering via superantigens induces decreased proliferative responses and increased apoptosis in T cells from HIV-infected patients compared with controls. Our aim was to delineate the role of intrinsic T cell defects, of APC dysfunction and of cytokines and costimulatory signal dysregulation in the deficient responses of CD4⁺and CD8⁺ T cells from HIV⁺ subjects to the superantigen Staphylococcus enterotoxin A (SEA). Proliferation and IL-2Rα up-regulation on SEA-stimulated CD4⁺and CD8⁺T cells in whole blood were reduced in HIV⁺ subjects with CD4 counts < 500, compared with controls. Neither addition of IL-2, IL-12 or phorbol myristate acetate (PMA) nor neutralization of endogenous IL-10, tumour necrosis factor-alpha (TNF-α), TNF-β or transforming growth factor-beta (TGF-β) could restore the decreased activation by SEA. Possible intrinsic T cell defects were studied by presenting SEA on HLA-DR-transfected Chinese hamster ovary (CHO) cells, co-expressing LFA3 and/or CD80, to purified T cells. In this system CD8⁺T cells from most HIV⁺ patients were hyporesponsive with regard to IL-2 production, IL-2Rα up-regulation and proliferation, whereas clearly reduced responses were only shown in CD4⁺T cells from AIDS patients. Similarly, apoptosis was increased in CD8⁺T cells from all patients, but only in CD4⁺T cells from AIDS patients. During HIV infection, the responses to TCR triggering through SEA are deficient in both T cell subsets. The intrinsic defect appears earlier during disease progression in purified CD8⁺T than in CD4⁺T cells, it occurs in conjunction with both CD2 and CD28 costimulation, and it is correlated with increased levels of apoptosis.     

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.     

NK cells are primed by ANRS MVAHIV‐infected DCs,via a mechanism involving NKG2D and membrane‐bound IL‐15, to control HIV‐1 infection in CD4+ T cells

Natural killer (NK) cells are the major antiviral effector cell population of the innate immune system. It has been demonstrated that NK‐cell activity can be modulated by the interaction with dendritic cells (DCs). The HIV‐1 vaccine candidate Modified Vaccinia Ankara encoding an HIV polypeptide (MVA_HIV), developed by the French National Agency for Research on AIDS (ANRS), has the ability to prime NK cells to control HIV‐1 infection in DCs. However, whether or not MVA_HIV‐primed NK cells are able to better control HIV‐1 infection in CD4⁺ T cells, and the mechanism underlying the specific priming, remain undetermined. In this study, we show that MVA_HIV‐primed NK cells display a greater capacity to control HIV‐1 infection in autologous CD4⁺ T cells. We also highlight the importance of NKG2D engagement on NK cells and DC‐produced IL‐15 to achieve the anti‐HIV‐1 specific priming, as blockade of either NKG2D or IL‐15 during MVA_HIV‐priming lead to a subsequent decreased control of HIV‐1 infection in autologous CD4⁺ T cells. Furthermore, we show that the decreased control of HIV‐1 infection in CD4⁺ T cells might be due, at least in part, to the decreased expression of membrane‐bound IL‐15 (mbIL‐15) on DCs when NKG2D is blocked during MVA_HIV‐priming of NK cells.     

Human antigen‐specific CD4+CD25+CD134+CD39+ T cells are enriched for regulatory T cells and comprise a substantial proportion of recall responses

Human Ag‐specific CD4⁺ T cells can be detected by their dual expression of CD134 (OX40) and CD25 after a 44 hours stimulation with cognate Ag. We show that surface expression of CD39 on Ag‐specific cells consistently identifies a substantial population of CD4⁺CD25⁺CD134⁺CD39⁺ T cells that have a Treg‐cell‐like phenotype and mostly originate from bulk memory CD4⁺CD45RO⁺CD127^lowCD25^highCD39⁺ Treg cells. Viable, Ag‐specific CD25⁺CD134⁺CD39⁺ T cells could be expanded in vitro as cell lines and clones, and retained high Forkhead Box Protein 3, CTLA‐4 and CD39 expression, suppressive activity and Ag specificity. We also utilised this combination of cell surface markers to measure HIV‐Gag responses in HIV⁺ patients before and after anti‐retroviral therapy (ART). Interestingly, we found that the percentage of CD39^? cells within baseline CD4⁺ T‐cell responses to HIV‐Gag was negatively correlated with HIV viral load pre‐ART and positively correlated with CD4⁺ T‐cell recovery over 96 weeks of ART. Collectively, our data show that Ag‐specific CD4⁺CD25⁺CD134⁺CD39⁺ T cells are highly enriched for Treg cells, form a large component of recall responses and maintain a Treg‐cell‐like phenotype upon in vitro expansion. Identification and isolation of these cells enables the role of Treg cells in memory responses to be further defined and provides a development pathway for novel therapeutics.     

γδ T lymphocyte responses to HIV

Natural immunity may be involved in controlling viral spread in hosts infected with HIV. A panel of γδ T cell receptor-positive lymphocyte clones was isolated from the peripheral blood of healthy HIV⁻ donors and tested for anti-HIV cytotoxic responses. Twelve of 30 (40%) Vγ9⁺Vδ2⁺ T cell clones, but none of seven Vδ1⁺ T cell clones, displayed lytic activity against HIV-infected cells. The Vγ9⁺/Vδ2⁺ clones cytotoxic for HIV-infected cells also lysed Daudi cells. However, not all Vγ9⁺/Vδ2⁺ clones which lysed Daudi targets had the capacity to lyse HIV-infected cells. Some of the γδ T cell clones were also investigated for potential proliferative responses to HIV-infected cells. One Vγ9⁺/Vδ2⁺ T cell clone (ME8-7) and one Vδ1⁺ T cell clone (ME18-2) demonstrated proliferative responses toward HIV-infected cells. Another Vγ9⁺/Vδ2⁺ clone (VM39) proliferated in response to cell-free HIV. Taken together, these results provide direct evidence of anti-HIV γδ T cell responses in healthy, HIV⁻ persons.     

The effect of timing of antiretroviral therapy on CD4+ T-cell reconstitution in the intestine of HIV-infected patients

Whether and to what extent gut mucosal CD4⁺ T cells of HIV-infected patients can be restored by combination antiretroviral therapy (cART) is not yet fully resolved. We studied absolute numbers, differentiation, and activation of mucosal CD4⁺ T cells at different stages of HIV infection and assessed the effect of timing of cART initiation on this cell population. Mucosal CD4⁺ T-cell numbers were severely reduced at all stages of chronic infection, but normal in patients with acute infection. In patients with initiation of cART during chronic HIV infection, mucosal CD4⁺ T cells restored to less than half of the numbers in controls. However, in patients who initiated cART during acute HIV infection, mucosal CD4⁺ T-cell numbers were fully preserved and markers of microbial translocation and inflammation reversed to normal. The proportion of mucosal effector memory CD4⁺ T cells normalized only if cART was initiated at >350 CD4⁺ T cells per μl blood but not with delayed treatment. In conclusion, mucosal CD4⁺ T-cell numbers can be preserved if cART is initiated in acute HIV infection. In chronically HIV-infected patients, early cART improves mucosal CD4⁺ T-cell differentiation but cannot prevent the persistent lack of total CD4⁺ T cells.