Dendritic cells from HIV-1 infected individuals are less responsive to toll-like receptor (TLR) ligands

We compared TLR responsiveness in PBMC from HIV-1-infected and uninfected individuals using the TLR agonists: TLR7 (3M-001), TLR8 (3M-002), and TLR7/8 (3M-011). Activation and maturation of plasmacytoid dendritic cells (pDC) were measured by evaluating CD86, CD40, and CD83 expression and myeloid dendritic cell (mDC) activation was measured by evaluating CD40 expression. All agonists tested induced activation and maturation of pDC in PBMC cultures of cells from HIV+ and HIV- individuals. The TLR7 agonist induced significantly less pDC maturation in cells from HIV+ individuals. Quantitative assessment of secreted IFN-alpha and pro-inflammatory cytokines at the single cell level showed that pDC from HIV+ individuals stimulated with TLR7 and TLR7/8 induced IFN-alpha. TLR8 and TLR7/8 agonists induced IL-12 and COX-2 expression in mDC from HIV+ and HIV- individuals. Understanding pDC and mDC activation and maturation in HIV-1 infection could lead to more rational development of immunotherapeutic strategies to stimulate the adaptive immune response to HIV-1.     

Loss of NK stimulatory capacity by plasmacytoid and monocyte-derived DC but not myeloid DC in HIV-1 infected patients

Dendritic cells (DC) are potent inducers of natural killer (NK) cells. There are two distinct populations in blood, myeloid (mDC) and plasmacytoid (pDC) but they can also be generated In vitro from monocytes (mdDC). Although it is established that blood DC are lost in HIV-1 infection, the full impact of HIV-1 infection on DC-NK cell interactions remains elusive. We thus investigated the ability of pDC, mDC, and mdDC from viremic and anti-retroviral therapy-treated aviremic HIV-1+ patients to stimulate various NK cell functions. Stimulated pDC and mdDC from HIV-1+ patients showed reduced secretion of IFN-α and IL-12p70 respectively and their capacity to stimulate expression of CD25 and CD69, and IFN-γ secretion in NK cells was also reduced. pDC activation of NK cell degranulation in response to a tumour cell line was severely reduced in HIV-1+ patients but the ability of mDC to activate NK cells was not affected by HIV-1 infection, with the exception of HLA-DR induction. No differences were observed between viremic and aviremic patients indicating that anti-retroviral therapy had minimal effect on restoration on pDC and mdDC-mediated activation of NK cells. Results from this study provide further insight into HIV-1 mediated suppression of innate immune functions.     

Compartmental imbalance and aberrant immune function of blood CD123+ (plasmacytoid) and CD11c+ (myeloid) dendritic cells in atopic dermatitis

Atopic dermatitis (AD) is a pruritic, chronically relapsing skin disease in which Th2 cells play a crucial role in cutaneous and extracutaneous immune reactions. In humans, CD11c+CD123- myeloid dendritic cells (mDC) and CD11c-CD123+ plasmacytoid DC (pDC) orchestrate the decision-making process in innate and acquired immunity. Since the number and function of these blood dendritic cell (DC) subsets reportedly reflect the host immune status, we studied the involvement of the DC subsets in the pathogenesis of AD. Patients with AD had an increased DC number and a low mDC:pDC ratio with pDC outnumbering mDC in the peripheral blood compared with normal subjects and psoriasis patients (a Th1 disease model group). The mDC:pDC ratio was correlated with the total serum IgE level, the ratio of IFN-gamma-producing blood cells:IL-4-producing blood cells, and the disease severity. In vitro allogeneic stimulation of naive CD4+ cells with atopic DC showed that the ability of pDC for Th1 induction was superior or comparable to that of mDC. In skin lesions, pDC infiltration was in close association with blood vessels expressing peripheral neural addressins. Therefore, compartmental imbalance and aberrant immune function of the blood DC subsets may deviate the Th1/Th2 differentiation and thus induce protracted allergic responses in AD.     

Severe CD4+ T-cell depletion in gut lymphoid tissue during primary human immunodeficiency virus type 1 infection and substantial delay in restoration following highly active antiretroviral therapy

Gut-associated lymphoid tissue (GALT) harbors the majority of T lymphocytes in the body and is an important target for human immunodeficiency virus type 1 (HIV-1). We analyzed longitudinal jejunal biopsy samples from HIV-1-infected patients, during both primary and chronic stages of HIV-1 infection, prior to and following the initiation of highly active antiretroviral therapy (HAART) to determine the onset of CD4(+) T-cell depletion and the effect of HAART on the restoration of CD4(+) T cells in GALT. Severe depletion of intestinal CD4(+) T cells occurred during primary HIV-1 infection. Our results showed that the restoration of intestinal CD4(+) T cells following HAART in chronically HIV-1-infected patients was substantially delayed and incomplete. In contrast, initiation of HAART during early stages of infection resulted in near-complete restoration of intestinal CD4(+) T cells, despite the delay in comparison to peripheral blood CD4(+) T-cell recovery. DNA microarray analysis of gene expression profiles and flow-cytometric analysis of lymphocyte homing and cell proliferation markers demonstrated that cell trafficking to GALT and not local proliferation contributed to CD4(+) T-cell restoration. Evaluation of jejunal biopsy samples from long-term HIV-1-infected nonprogressors showed maintenance of normal CD4(+) T-cell levels in both GALT and peripheral blood. Our results demonstrate that near-complete restoration of mucosal immune system can be achieved by initiating HAART early in HIV-1 infection. Monitoring of the restoration and/or maintenance of CD4(+) T cells in GALT provides a more accurate assessment of the efficacy of antiviral host immune responses as well as HAART.     

Discordance between frequency of human immunodeficiency virus type 1 (HIV-1)-specific gamma interferon-producing CD4(+) T cells and HIV-1-specific lymphoproliferation in HIV-1-infected subjects with active viral replication

One hallmark of uncontrolled, chronic human immunodeficiency virus type 1 (HIV-1) infection is the absence of strong HIV-1-specific, CD4(+) T-cell-proliferative responses, yet the mechanism underlying this T helper (Th)-cell defect remains controversial. To better understand the impact of HIV-1 replication on Th-cell function, we compared the frequency of CD4(+) Th-cell responses based on production of gamma interferon to lymphoproliferative responses directed against HIV-1 proteins in HIV-1-infected subjects with active in vivo viral replication versus those on suppressed highly active antiretroviral therapy (HAART). No statistically significant differences in the frequencies of cytokine-secreting, HIV-1-specific CD4(+) T cells between the donor groups were found, despite differences in viral load and treatment status. However, HIV-1-specific lymphoproliferative responses were significantly greater in the subjects with HAART suppression than in subjects with active viral replication. Similar levels of HIV-1 RNA were measured in T-cell cultures stimulated with HIV-1 antigens regardless of donor in vivo viral loads, but only HIV-1-specific CD4(+) T cells from subjects with HAART suppression proliferated in vitro, suggesting that HIV-1 replication in vitro does not preclude HIV-1-specific lymphoproliferation. This study demonstrates a discordance between the frequency and proliferative capacity of HIV-1-specific CD4(+) T cells in subjects with ongoing in vivo viral replication and suggests that in vivo HIV-1 replication contributes to the observed defect in HIV-1-specific CD4(+) T-cell proliferation.     

Abnormal humoral immune response to influenza vaccination in pediatric type-1 human immunodeficiency virus infected patients receiving highly active antiretroviral therapy

Given that highly active antiretroviral therapy (HAART) has been demonstrated useful to restore immune competence in type-1 human immunodeficiency virus (HIV-1)-infected subjects, we evaluated the specific antibody response to influenza vaccine in a cohort of HIV-1-infected children on HAART so as to analyze the quality of this immune response in patients under antiretroviral therapy. Sixteen HIV-1-infected children and 10 HIV-1 seronegative controls were immunized with a commercially available trivalent inactivated influenza vaccine containing the strains A/H1N1, A/H3N2, and B. Serum hemagglutinin inhibition (HI) antibody titers were determined for the three viral strains at the time of vaccination and 1 month later. Immunization induced a significantly increased humoral response against the three influenza virus strains in controls, and only against A/H3N2 in HIV-1-infected children. The comparison of post-vaccination HI titers between HIV-1+ patients and HIV-1 negative controls showed significantly higher HI titers against the three strains in controls. In addition, post vaccination protective HI titers (defined as equal to or higher than 1:40) against the strains A/H3N2 and B were observed in a lower proportion of HIV-1+ children than in controls, while a similar proportion of individuals from each group achieved protective HI titers against the A/H1N1 strain. The CD4+ T cell count, CD4/CD8 T cells ratio, and serum viral load were not affected by influenza virus vaccination when pre- vs post-vaccination values were compared. These findings suggest that despite the fact that HAART is efficient in controlling HIV-1 replication and in increasing CD4+ T cell count in HIV-1-infected children, restoration of immune competence and response to cognate antigens remain incomplete, indicating that additional therapeutic strategies are required to achieve a full reconstitution of immune functions.     

Residual Viral Replication during Antiretroviral Therapy Boosts Human Immunodeficiency Virus Type 1-Specific CD8+ T-Cell Responses in Subjects Treated Early after Infection

Human immunodeficiency virus type 1 (HIV-1)-infected subjects treated early after infection have preserved HIV-1-specific CD4+ T-cell function. We studied the effect of highly active antiretroviral therapy (HAART) on the frequency of HIV-1-specific CD8+ T cells in patients treated during early (n = 31) or chronic (n = 23) infection. The degree of viral suppression and time of initiation of treatment influenced the magnitude of the CD8+ T-cell response. HIV-1-specific CD8+ T cells can increase in number after HAART in subjects treated early after infection who have episodes of transient viremia.     

Severe and persistent depletion of circulating plasmacytoid dendritic cells in patients with 2009 pandemic H1N1 infection

Background

Dysregulation of host immune responses plays a critical role in the pathogenesis of severe 2009 pandemic H1N1 infection. Whether H1N1 virus could escape innate immune defense in vivo remains to be investigated. The aim of this study was to evaluate the pattern of innate immune response during human 2009 H1N1 infection. We performed the enumeration of circulating myeloid dendritic cells (mDC) and plasmacytoid DC (pDC) in blood from patients with H1N1 pneumonia shortly after the onset of symptoms and during follow-up at different intervals of time. The analysis of CD4 and CD8 count, CD38 T-cell activation marker and serum cytokine/chemokine plasma levels was also done.

Methodology/Principal Findings

Blood samples were collected from 13 hospitalized patients with confirmed H1N1-related pneumonia at time of admission and at weeks 1, 4, and 16 of follow-up. 13 healthy donors were enrolled as controls. In the acute phase of the disease, H1N1-infected patients exhibited a significant depletion in both circulating pDC and mDC in conjunction with a decrease of CD4 and CD8 T cell count. In addition, we found plasmatic hyperproduction of IP-10 and RANTES, whereas increase in T-cell immune activation was found at all time points. When we assessed the changes in DC count over time, we observed a progressive normalization of mDC number. On the contrary, H1N1-infected patients did not achieve a complete recovery of pDC count as values remained lower than healthy controls even after 16 weeks of follow-up.

Conclusions

H1N1 disease is associated with a profound depletion of DC subsets. The persistence of pDC deficit for several weeks after disease recovery could be due to H1N1 virus itself or to a preexisting impairment of innate immunity.     

Plasmacytoid dendritic cells synergize with myeloid dendritic cells in the induction of antigen-specific antitumor immune responses

Plasmacytoid dendritic cells (pDC) are capable of producing high levels of type I IFNs upon viral stimulation, and play a central role in modulating innate and adaptive immunity against viral infections. Whereas many studies have assessed myeloid dendritic cells (mDC) in the induction of antitumor immune responses, the role of pDC in antitumor immunity has not been addressed. Moreover, the interaction of pDC with other dendritic cell subsets has not been evaluated. In this study, we analyzed the capacity of pDC in stimulating an Ag-specific T cell response. Immunization of mice with Ag-pulsed, activated pDC significantly augmented Ag-specific CD8(+) CTL responses, and protected mice from a subsequent tumor challenge. Immunization with a mixture of activated pDC plus mDC resulted in increased levels of Ag-specific CD8(+) T cells and an enhanced antitumor response compared with immunization with either dendritic cell subset alone. Synergy between pDC and mDC in their ability to activate T cells was dependent on MHC I expression by mDC, but not pDC, suggesting that pDC enhanced the ability of mDC to present Ag to T cells. Our results demonstrate that pDC and mDC can interact synergistically to induce an Ag-specific antitumor immune response in vivo.     

Naive T-cell depletion related to infection by X4 human immunodeficiency virus type 1 in poor immunological responders to highly active antiretroviral therapy

The reasons for poor CD4+ T-cell recovery in some human immunodeficiency virus (HIV)-infected subjects despite effective highly active antiretroviral therapy (HAART) remain unclear. We recently reported that CXCR4-using (X4) HIV-1 could be gradually selected in cellular reservoirs during sustained HAART. Because of the differential expression of HIV-1 coreceptors CCR5 and CXCR4 on distinct T-cell subsets, the residual replication of R5 and X4 viruses could have different impacts on T-cell homeostasis during immune reconstitution on HAART. We examined this hypothesis and the mechanisms of CD4+ T-cell restoration by comparing the virological and immunological features of 15 poor and 15 good immunological responders to HAART. We found a high frequency of X4 viruses in the poor immunological responders. But the levels of intrathymic proliferation of the two groups were similar regardless of whether they were infected by R5 or X4 virus. The frequency of recent thymic emigrants in the poor immunological responders was also similar to that found in the good immunological responders, despite their reduced numbers of na?ve CD4+ T cells. Our data, rather, suggest that the na?ve T-cell compartment is drained by a high rate of mature na?ve cell loss in the periphery due to bystander apoptosis or activation-induced differentiation. X4 viruses could play a role in the depletion of na?ve T cells in poor immunological responders to HAART by triggering persistent T-cell activation and bystander apoptosis via gp120-CXCR4 interactions.     

Identification of human endogenous retrovirus-specific T cell responses in vertically HIV-1-infected subjects

Human endogenous retrovirus (HERV)-specific T cell responses in HIV-1-infected adults have been reported. Whether HERV-specific immunity exists in vertically HIV-1-infected children is unknown. We performed a cross-sectional analysis of HERV-specific T cell responses in 42 vertically HIV-1-infected children. HERV (-H, -K, and -L family)-specific T cell responses were identified in 26 of 42 subjects, with the greatest magnitude observed for the responses to HERV-L. These HERV-specific T cell responses were inversely correlated with the HIV-1 plasma viral load and positively correlated with CD4(+) T cell counts. These data indicate that HERV-specific T cells may participate in controlling HIV-1 replication and that certain highly conserved HERV-derived proteins may serve as promising therapeutic vaccine targets in HIV-1-infected children.     

Blood myeloid dendritic cells from HIV-1-infected individuals display a proapoptotic profile characterized by decreased Bcl-2 levels and by caspase-3+ frequencies that are associated with levels of plasma viremia and T cell activation in an exploratory study

Reduced frequencies of myeloid and plasmacytoid dendritic cell (DC) subsets (mDCs and pDCs, respectively) have been observed in the peripheral blood of HIV-1-infected individuals throughout the course of disease. Accumulation of DCs in lymph nodes (LNs) may partly account for the decreased numbers observed in blood, but increased DC death may also be a contributing factor. We used multiparameter flow cytometry to evaluate pro- and antiapoptotic markers in blood mDCs and pDCs from untreated HIV-1-infected donors, from a subset of infected donors before and after receiving antiretroviral therapy (ART), and from uninfected control donors. Blood mDCs, but not pDCs, from untreated HIV-1-infected donors expressed lower levels of antiapoptotic Bcl-2 than DCs from uninfected donors. A subset of HIV-1-infected donors had elevated frequencies of proapoptotic caspase-3(+) blood mDCs, and positive correlations were observed between caspase-3(+) mDC frequencies and plasma viral load and CD8(+) T-cell activation levels. Caspase-3(+) mDC frequencies, but not mDC Bcl-2 expression, were reduced with viral suppression on ART. Apoptosis markers on DCs in blood and LN samples from a cohort of untreated, HIV-1-infected donors with chronic disease were also evaluated. LN mDCs displayed higher levels of Bcl-2 and lower caspase-3(+) frequencies than did matched blood mDCs. Conversely, LN pDCs expressed lower Bcl-2 levels than their blood counterparts. In summary, blood mDCs from untreated HIV-1-infected subjects displayed a proapoptotic profile that was partially reversed with viral suppression, suggesting that DC death may be a factor contributing to blood DC depletion in the setting of chronic, untreated HIV disease.     

Safety and immunogenicity of ALVAC vCP1452 and recombinant gp160 in newly human immunodeficiency virus type 1-infected patients treated with prolonged highly active antiretroviral therapy

In order to boost immune responses in persons in whom highly active antiretroviral therapy (HAART) was initiated within 120 days of the onset of symptoms of newly acquired human immunodeficiency virus type 1 (HIV-1) infection, we administered vaccines containing a canarypox virus vector, vCP1452, with HIV-1 genes encoding multiple HIV-1 proteins, and recombinant gp160. Fifteen HIV-1-infected subjects who achieved sustained suppression of plasma viremia for at least 2 years were enrolled. While continuing antiretroviral therapy, each subject received at least four intramuscular injections of the vaccines on days 0, 30, 90, and 180. Adverse events were mild, with the most common being transient tenderness at the vCP1452 injection site. Of the 14 patients who completed vaccination, 13 had significant increases in anti-gp120 or anti-p24 antibody titers, and 9 had transient augmentation of their T-cell proliferation responses to gp160 and/or p24. HIV-1-specific CD8(+) T cells were quantified using an intracellular gamma interferon staining assay. Among 11 patients who had increased CD8(+) T-cell responses, seven had responses to more than one HIV-1 antigen. In summary, vaccination with vCP1452 and recombinant gp160 appears safe and immunogenic in newly HIV-1-infected patients on HAART.     

Natural killer cells in perinatally HIV-1-infected children exhibit less degranulation compared to HIV-1-exposed uninfected children and their expression of KIR2DL3, NKG2C, and NKp46 correlates with disease severity

NK cells play an integral role in the innate immune response by targeting virally infected and transformed cells with direct killing and providing help to adaptive responses through cytokine secretion. Whereas recent studies have focused on NK cells in HIV-1-infected adults, the role of NK cells in perinatally HIV-1-infected children is less studied. Using multiparametric flow cytometric analysis, we assessed the number, phenotype, and function of NK cell subsets in the peripheral blood of perinatally HIV-1-infected children on highly active antiretroviral therapy and compared them to perinatally exposed but uninfected children. We observed an increased frequency of NK cells expressing inhibitory killer Ig-like receptors in infected children. This difference existed despite comparable levels of total NK cells and NK cell subpopulations between the two groups. Additionally, NK cell subsets from infected children expressed, with and without stimulation, significantly lower levels of the degranulation marker CD107, which correlates with NK cell cytotoxicity. Lastly, increased expression of KIR2DL3, NKG2C, and NKp46 on NK cells correlated with decreased CD4+ T-lymphocyte percentage, an indicator of disease severity in HIV-1- infected children. Taken together, these results show that HIV-1-infected children retain a large population of cytotoxically dysfunctional NK cells relative to perinatally exposed uninfected children. This reduced function appears concurrently with distinct NK cell surface receptor expression and is associated with a loss of CD4+ T cells. This finding suggests that NK cells may have an important role in HIV-1 disease pathogenesis in HIV-1-infected children.     

Reversal of HIV-1 latency with anti-microRNA inhibitors

Human immunodeficiency virus type 1 (HIV-1) latency is achieved when host cells contain integrated proviral DNA but do not produce viral particles. The virus remains in resting CD4 T-lymphocytes, evading host immune surveillance and antiviral drugs. When resting cells are activated, infectious viral particles are produced. Latency is critical for the survival of all HIV-1 strains in vivo. Recently, it has been reported that a cluster of cellular microRNAs (miRNAs) enriched specifically in resting CD4+ T-cells suppresses translation of most HIV-1-encoded proteins in the cytoplasm, sustaining HIV-1 escape from the host immune response. Complementary antisense miRNA inhibitors block the inhibitory effect of miRNAs and drive viral production from the resting T-lymphocytes without activating the cells. Therefore, inhibition of these HIV-1-specific cellular miRNAs is of great therapeutic significance for eliminating the HIV-1 reservoir in HIV-1-infected individuals receiving suppressive highly active antiretroviral therapy (HAART).     

HIV-1-specific memory CD4+ T cells are phenotypically less mature than cytomegalovirus-specific memory CD4+ T cells

HIV-1-specific CD4(+) T cells are qualitatively dysfunctional in the majority of HIV-1-infected individuals and are thus unable to effectively control viral replication. The current study extensively details the maturational phenotype of memory CD4(+) T cells directed against HIV-1 and CMV. We find that HIV-1-specific CD4(+) T cells are skewed to an early central memory phenotype, whereas CMV-specific CD4(+) T cells generally display a late effector memory phenotype. These differences hold true for both IFN-gamma- and IL-2-producing virus-specific CD4(+) T cells, are present during all disease stages, and persist even after highly active antiretroviral therapy (HAART). In addition, after HAART, HIV-1-specific CD4(+) T cells are enriched for CD27(+)CD28(-)-expressing cells, a rare phenotype, reflecting an early intermediate stage of differentiation. We found no correlation between differentiation phenotype of HIV-1-specific CD4(+) T cells and HIV-1 plasma viral load or HIV-1 disease progression. Surprisingly, HIV-1 viral load affected the maturational phenotype of CMV-specific CD4(+) T cells toward an earlier, less-differentiated state. In summary, our data indicate that the maturational state of HIV-1-specific CD4(+) T cells cannot be a sole explanation for loss of containment of HIV-1. However, HIV-1 replication can affect the phenotype of CD4(+) T cells of other specificities, which might adversely affect their ability to control those pathogens. The role for HIV-1-specific CD4(+) T cells expressing CD27(+)CD28(-) after HAART remains to be determined.     

Higher homologous and lower cross-reactive Gag-specific T-cell responses in human immunodeficiency virus type 2 (HIV-2) than in HIV-1 infection

Human immunodeficiency virus type 2 (HIV-2) infection results in slower CD4⁺ T-cell decline, lower plasma viral load levels, and hence slower progression of the disease than does HIV-1 infection. Although the reasons for this are not clear, it is possible that HIV-2 replication is more effectively controlled by host responses. We used aligned pools of overlapping HIV-1 and HIV-2 Gag peptides in an enhanced gamma interferon enzyme-linked immunospot assay to compare the levels of homologous and cross-reactive Gag-specific T-cell responses between HIV-1- and HIV-2-infected patients. HIV-2-infected patients showed broader and stronger homologous Gag-specific T-cell responses than HIV-1-infected patients. In contrast, the cross-reactive T-cell responses in HIV-2-infected patients were both narrower and weaker than those in HIV-1-infected patients, in line with overall weaker correlations between homologous and heterologous T-cell responses among HIV-2-infected patients than among HIV-1-infected patients. Cross-reactive responses in HIV-2-infected patients tended to correlate directly with HIV-1/HIV-2 Gag sequence similarities; this was not found in HIV-1-infected patients. The CD4⁺ T-cell counts of HIV-2-infected patients correlated directly with homologous responses and inversely with cross-reactive responses; this was not found in HIV-1-infected patients. Our data support a model whereby high-level HIV-2-specific T-cell responses control the replication of HIV-2, thus limiting viral diversification and priming of HIV-1 cross-reactive T-cell responses over time. However, we cannot exclude the possibility that HIV-2 replication is controlled by other host factors and that HIV-2-specific T-cell responses are better maintained in the context of slow viral divergence and a less damaged immune system. Understanding the nature of immune control of HIV-2 infection could be crucial for HIV vaccine design.     

Clinical significance of circulating dendritic cells in patients with systemic lupus erythematosus

Dendritic cells are a complex group of mainly bone-marrow-derived leukocytes that play a role in autoimmune diseases. The total number of circulating dendritic cells (tDC), and their plasmacytoid dendritic cell (pDC) and myeloid dendritic cell (mDC1 and mDC2) subpopulations were assessed using flow cytometry. The number of tDC and their subsets were significantly lower in systemic lupus erythematosus patients than in the control group. The count of tDC and their subsets correlated with the number of T cells. The number of tDC and pDC subpopulation were lower in the patients with lymphopenia and leukopenia than in the patients without these symptoms. Our data suggest that fluctuations in blood dendritic cell count in systemic lupus erythematosus patients are much more significant in pDC than in mDC, what may be caused by their migration to the sites of inflammation including skin lesions. Positive correlation between dendritic cell number and TCD4+, TCD8+ and CD19+ B cells, testify of their interactions and influence on SLE pathogenesis. The association between dendritic cell number and clinical features seems to be less clear.     

HIV-induced T-cell activation/exhaustion in rectal mucosa is controlled only partially by antiretroviral treatment

Peripheral blood T-cells from untreated HIV-1-infected patients exhibit reduced immune responses, usually associated with a hyperactivated/exhausted phenotype compared to HAART treated patients. However, it is not clear whether HAART ameliorates this altered phenotype of T-cells in the gastrointestinal-associated lymphoid tissue (GALT), the main site for viral replication. Here, we compared T-cells from peripheral blood and GALT of two groups of chronically HIV-1-infected patients: untreated patients with active viral replication, and patients on suppressive HAART. We characterized the T-cell phenotype by measuring PD-1, CTLA-4, HLA-DR, CD25, Foxp3 and granzyme A expression by flow cytometry; mRNA expression of T-bet, GATA-3, ROR-γt and Foxp3, and was also evaluated in peripheral blood mononuclear cells and rectal lymphoid cells. In HIV-1+ patients, the frequency of PD-1(+) and CTLA-4(+) T-cells (both CD4+ and CD8+ T cells) was higher in the GALT than in the blood. The expression of PD-1 by T-cells from GALT was higher in HIV-1-infected subjects with active viral replication compared to controls. Moreover, the expression per cell of PD-1 and CTLA-4 in CD4(+) T-cells from blood and GALT was positively correlated with viral load. HAART treatment decreased the expression of CTLA-4 in CD8(+) T cells from blood and GALT to levels similar as those observed in controls. Frequency of Granzyme A(+) CD8(+) T-cells in both tissues was low in the untreated group, compared to controls and HAART-treated patients. Finally, a switch towards Treg polarization was found in untreated patients, in both tissues. Together, these findings suggest that chronic HIV-1 infection results in an activated/exhausted T-cell phenotype, despite T-cell polarization towards a regulatory profile; these alterations are more pronounced in the GALT compared to peripheral blood, and are only partiality modulated by HAART.     

Correlates of delayed disease progression in HIV-1-infected Kenyan children

Without treatment most HIV-1-infected children in Africa die before their third birthday (>89%) and long-term nonprogressors are rare. The mechanisms underlying nonprogression in HIV-1-infected children are not well understood. In the present study, we examined potential correlates of delayed HIV disease progression in 51 HIV-1-infected African children. Children were assigned to progression subgroups based on clinical characterization. HIV-1-specific immune responses were studied using a combination of ELISPOT assays, tetramer staining, and FACS analysis to characterize the magnitude, specificity, and functional phenotype of HIV-1-specific CD8(+) and CD4(+) T cells. Host genetic factors were examined by genotyping with sequence-specific primers. HIV-1 nef gene sequences from infecting isolates from the children were examined for potential attenuating deletions. Thymic output was measured by T cell rearrangement excision circle assays. HIV-1-specific CD8(+) T cell responses were detected in all progression groups. The most striking attribute of long-term survivor nonprogressors was the detection of HIV-1-specific CD4(+) Th responses in this group at a magnitude substantially greater than previously observed in adult long-term nonprogressors. Although long-term survivor nonprogressors had a significantly higher percentage of CD45RA(+)CD4(+) T cells, nonprogression was not associated with higher thymic output. No protective genotypes for known coreceptor polymorphisms or large sequence deletions in the nef gene associated with delayed disease progression were identified. In the absence of host genotypes and attenuating mutations in HIV-1 nef, long-term surviving children generated strong CD4(+) T cell responses to HIV-1. As HIV-1-specific helper cells support anti-HIV-1 effector responses in active disease, their presence may be important in delaying disease progression.