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Objectives: HIV controllers (HICs) are rare HIV-infected individuals able to maintain undetectable viremia in the absence of antiretroviral treatment. Although HIV-specific cytotoxic T cells have been well deciphered in HIC, γδ T lymphocytes remain largely uncharacterized. The aim of this study was to analyse phenotypic and functional characteristics of γδ T cells and their relationship with immune activation, which remains abnormally elevated and associated with comorbidities in HICs., Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from 16 HICs, 16 patients with untreated chronic HIV infection (UT-CHI) and 20 healthy donors. Surface marker expression and cytokine production by γδ T cells were analysed by flow cytometry., Results: Despite normal frequencies of total γδ T cells, the Vδ2/Vδ2 ratio was significantly reduced in HIC, albeit to a lesser extent than UT-CHI patients. Of note, nine HICs showed elevated Vδ2 γδ T cells, as patients with UT-CHI, which was associated with higher CD8 T-cell activation. Interleukin (IL)-17-production by γδ T cells (Tγδ17) was better preserved in HIC than in UT-CHI patients. Proportion of total γδ T cells positively correlated with CD8 T-cell activation and HIV-DNA, IP-10 and sCD14 levels. Conversely, Tγδ17 cells negatively correlated with CD8 T-cell activation and plasma sCD14 levels. Moreover, transforming growth factor (TGF)-β producing Vδ2 T cells were as dramatically depleted in HIC as in UT-CHI patients., Conclusion: The relative preservation of IL-17-producing γδ T cells in HIC and their negative association with immune activation raise the hypothesis that Tγδ17 cells - potentially through prevention of microbial translocation - may participate in the control of chronic systemic immune activation.

Objective: Persistent immune activation plays a central role in the pathogenesis of HIV disease. Besides natural regulatory T cells (nTregs), 'double negative' T cells shown to exhibit regulatory properties could be involved in the control of harmful immune activation. The aim of this study was to analyze, in patients with primary HIV infection (PHI), the relationship between CD4(+)CD25(+)CD127(low)FoxP3(+) nTregs or CD3(+)CD4(-)CD8(-) double negative T cells and systemic immune activation., Design: A prospective longitudinal study of patients with early PHI., Methods: Twenty-five patients were included. Relationships between frequency of Treg subsets and T-cell activation, assessed on fresh peripheral blood mononuclear cells, were analyzed using nonparametric tests. Cytokine production by double negative T cells was assessed following anti-CD3/anti-CD28 stimulation., Results: No relationship was found between T-cell activation and frequencies of nTregs. In contrast, a strong negative relationship was found at baseline between the proportion of double negative T cells and the proportion of activated CD8 T cells coexpressing CD38 and HLA-DR (P = 0.005) or expressing Ki-67 (P = 0.002). In addition, the frequency of double negative T cells at baseline negatively correlated with the frequency of HLA-DR(+)CD38(+)CD8(+) T cells at month 6, defining the immune activation set point (P = 0.031). High proportions of stimulated double negative T cells were found to produce the immunosuppressive cytokines transforming growth factor-β1 and/or IL-10., Conclusion: The proportion of double negative T cells at baseline was found to be predictive of the immune activation set point. Our data strongly suggest that double negative T cells may control immune activation in PHI. This effect might be mediated through the production of TGF-β1/IL-10 known to downmodulate immune activation.

Objective: In this article, we studied the effect of acetyl-11-keto-beta-boswellic acid (AKbetaBA), a natural inhibitor of the proinflammatory transcription factor NF-kappaB on the development of atherosclerotic lesions in apolipoprotein E-deficient (apoE-/-) mice., Methods and Results: Atherosclerotic lesions were induced by weekly LPS injection in apoE-/- mice. LPS alone increased atherosclerotic lesion size by approximately 100%, and treatment with AKbetaBA significantly reduced it by approximately 50%. Moreover, the activity of NF-kappaB was also reduced in the atherosclerotic plaques of LPS-injected apoE-/- mice treated with AKbetaBA. As a consequence, AKbetaBA treatment led to a significant downregulation of several NF-kappaB-dependent genes such as MCP-1, MCP-3, IL-1alpha, MIP-2, VEGF, and TF. By contrast, AKbetaBA did not affect the plasma concentrations of triglycerides, total cholesterol, antioxidized LDL antibodies, and various subsets of lymphocyte-derived cytokines. Moreover, AKbetaBA potently inhibited the IkappaB kinase (IKK) activity immunoprecipitated from LPS-stimulated mouse macrophages and mononuclear cells leading to decreased phosphorylation of IkappaB alpha and inhibition of p65/NF-kappaB activation. Comparable AKbetaBA-mediated inhibition was also observed in LPS-stimulated human macrophages., Conclusions: The inhibition of NF-kappaB activity by plant resins from species of the Boswellia family might represent an alternative for classical medicine treatments for chronic inflammatory diseases such as atherosclerosis.

Objectives: Human thymus can be infected by HIV-1 with potential consequences on immune regeneration and homeostasis. We previously showed that CD4 thymocytes preferentially replicate CXCR4 tropic (X4) HIV-1 dependently on interleukin (IL)-7. Here we addressed the susceptibility of thymic dendritic cells (DC) to HIV-1 infection., Methods: We investigated the replication ability of CXCR4 or CCR5 (R5) tropic HIV-1 in thymic micro-explants as well as in isolated thymic CD11clowCD14- DC, CD11chighCD14+ DC and plasmacytoid DC subsets., Results: Thymic tissue was productively infected by both X4 and R5 viruses. However, X4 but not R5 HIV-1 replication was enhanced by IL-7 in thymic micro-explants, suggesting that R5 virus replication occurred in cells other than thymocytes. Indeed, we found that R5 HIV-1 replicated efficiently in DC isolated from thymic tissue. The replicative capacity of X4 and R5 viruses differed according to the different DC subsets. R5 but not X4 HIV-1 efficiently replicated in CD11chighCD14+ DC. In contrast, no HIV-1 replication was detected in CD11clowCD14- DC. Both X4 and R5 viruses efficiently replicated in plasmacytoid DC, which secreted interferon-alpha upon HIV-1 exposure. Productive HIV-1 infection also caused DC loss, consistent with different permissivity of each DC subset., Conclusions: Thymic DC sustain high levels of HIV-1 replication. DC might thus be the first target for R5 HIV-1 infection of thymus, acting as a Trojan horse for HIV-1 spread to thymocytes. Furthermore, DC death induced by HIV-1 infection may affect thymopoiesis.

Background: Despite multiple exposure to HIV-1, some individuals remain uninfected. This resistance has been associated with homozygosity for a 32 base pair deletion in the gene for the CCR5 receptor. This variant occurs frequently in Caucasians but is extremely rare in Asians or Africans., Objective: To identify variations in CCR5 receptor gene that affect susceptibility to HIV infection in non-Caucasians., Methods: CCR5 coding region polymorphisms were screened in three groups of Vietnamese subjects: 47 HIV-1 infected intravascular drug users, 50 highly HIV-1-exposed but seronegative intravascular drug users and 37 HIV-1-unexposed seronegative individuals. DNA was analysed by denaturing high performance liquid chromatography; this was followed by examination of the biochemical and HIV coreceptor properties of the coding regions., Results: Five CCR5 coding region variants were identified in this Vietnamese population. The S185R, I254T and C269F mutations have not been previously described; G106R and R223Q have already been found in other Asian populations, but the functional properties of G106R is not known. These variants differed in biochemical and HIV coreceptor properties. S185R and I254T variants had receptor and coreceptor activities comparable to that of the wild type, whereas C269F and G106R behaved differently. This latter pair are poorly expressed at the cell surface, weakly bind macrophage inflammatory protein 1beta (CCL4) and RANTES (CCL5), and display reduced HIV-1 coreceptor efficiency., Conclusions: Among the five CCR5 variants found in this Vietnamese population, G106R and C269F displayed significant modifications of their receptor and coreceptor properties, which may contribute to susceptibility to HIV-1 infection and/or disease progression within this population.

Objective: Expression of human apolipoprotein (h-apo) A-IV in apoE-deficient (apoE(0)) mice (h-apoA-IV/E(0)) reduces susceptibility to atherosclerosis. Chronic infection mimicked by exposure to lipopolysaccharide (LPS) increases the size of atherosclerosis lesions in apoE(0) mice. Thus, we used h-apoA-IV/E(0) mice to determine whether h-apoA-IV plays a protective role after LPS administration., Methods and Results: We injected apoE(0), h-apoA-IV/E(0), and C57Bl/6 (wild-type) mice intraperitoneally with either LPS or phosphate-buffered saline (PBS) every week for 10 weeks. Atherosclerotic lesions were significantly smaller in h-apoA-IV/E(0) mice treated with LPS than in their apoE(0) counterparts. The titers of IgG2a and IgG2b autoantibodies to oxidized low-density lipoprotein (LDL) were higher in the LPS-group of h-apoA-IV/E(0) mice than in apoE(0) mice, suggesting that the Th1 response is stronger in the presence of h-apoA-IV. Lymphocytes from the blood, liver, spleen, and thymus of h-apoA-IV/E(0) mice treated with LPS produced less IL-4, INF-gamma, and TNF-alpha proinflammatory cytokines than their apoE(0) counterparts. Furthermore, we demonstrated that recombinant h-apoA-IV blocks the LPS-induced stimulation of monocytes., Conclusions: The expression of h-apoA-IV in apoE(0) mice reduces the susceptibility to atherogenesis and decreases the secretion of proinflammatory cytokines after LPS administration.

Objective: To identify mechanisms of resistance to HIV-1 infection in exposed uninfected individuals., Design: We examined in-vitro cell susceptibility to HIV-1 infection in highly exposed Vietnamese intravascular drug users (IDU) who, despite a history of more than 10 years of drug use and a high prevalence of other blood-borne viral infections, remain apparently HIV uninfected., Methods: Forty-five exposed uninfected IDU and 50 blood donors were included in the study. Peripheral blood mononuclear cells (PBMC) or CD4 cell susceptibilities to HIV infection were evaluated using three HIV-1 isolates with different tropisms. Polymerase chain reaction analysis of HIV-1-DNA replication intermediates was used to characterize the restriction of HIV-1 replication in CD4 cells. Homologous CD8 cells were mixed with infected CD4 cells to evaluate their role in virus suppression., Results: We observed a relative resistance to PBMC infection with HIV-1 in 21 out of 45 exposed uninfected IDU, but only in five out of 50 unexposed controls (P < 0.001). PBMC resistance was related either to an inhibition of HIV-1 replication in CD4 cells or to CD8 cell-mediated viral suppression. HIV-1 replication in CD4 cells was restricted at the early stages of the viral cycle., Conclusion: Reduced PBMC susceptibility to HIV-1 infection was associated with resistance to infection in exposed uninfected IDU. Distinct mechanisms are involved in in-vitro resistance and may contribute to the apparent protection from HIV-1 transmission in this systemically exposed population.

Spleen cells from B6C3F1 hybrid mice pretreated i.v. with 5 X 10(7) C3H spleen cells seven days earlier (C3H-pretreated B6C3F1) suppress the in vitro B6 anti-B6C3F1 proliferative and cytotoxic responses, when they are added to cultures of B6 responding and B6C3F1 stimulating spleen cells. This suppression is mediated by a Thy-1+Lyt-1+2+ cell of C3H origin that is radiosensitive at 2000 rads. This suppressor cell is not induced by the injection to B6C3F1 hybrids of spleen cells from the other parent strain (B6) or an allogeneic strain (D2). It does not suppress either the response of the other parent (C3H) or an allogeneic strain (D2) to B6C3F1 antigens, or the response of B6 cells to an allogeneic strain (D2). Its induction depends upon the number and the subpopulation of C3H spleen cells injected since suppression is observed after the injection of more than 2.5 X 10(7) C3H cells, and the suppression inducing cells have the phenotype Thy-1+Lyt-1+2+. This phenomenon is not limited to the C3H-B6C3F1 genetic combination, since it has been observed in all parent hybrid combinations tested to date.

B6D2F1 hybrid mice pretreated i.v. with 5 X 10(7) spleen cells from B6 donors seven days earlier (B6-pretreated B6D2F1 hybrids) develop resistance to local GVHR induced by the subcutaneous injection of spleen cells of either B6 (GVHR-B6) or D2 (GVHR-D2) origin. This resistance has specific and a nonspecific components that concern the GVHR-B6 and the GVHR-D2, respectively. The two types of resistance to GVHR are neither induced under the same conditions nor mediated by the same mechanism. Specific resistance to GVHR is observed in B6D2F1 hybrids pretreated with unseparated, anti-Lyt-1.2+C' treated or 1000 rads-irradiated B6 cells, but not in B6D2F1 hybrids pretreated with anti-Thy-1.2+C' or anti Lyt-2.2+C'-treated B6 cells. In contrast, nonspecific resistance to GVHR is induced only by pretreatment with unseparated B6 cells. Treatment of B6 cells with anti-Thy-1.2, anti-Lyt-1.2, or anti-Lyt-2.2 moAb plus C', or their irradiation at 1000 rads completely abolishes their capacity to induce the nonspecific resistance to GVHR. Moreover, specific resistance to GVHR can be transferred to normal B6D2F1 mice by injection of nylon-adherent, anti-Thy-1.2+C'-treated or 2000-rads-irradiated, but not unseparated or nylon-nonadherent, B6-pretreated B6D2F1 spleen cells. Treatment of nylon-adherent B6-pretreated B6D2F1 cells with anti H-2d antiserum plus C' does not affect their capacity to transfer specific resistance to GVHR. Nonspecific resistance to GVHR can be transferred by unseparated, anti-Lyt-1.1+C' or anti Lyt-2.1+C'-treated, but not by anti-Thy-1.2+C' anti-Lyt-1.2+C', anti-Lyt-2.2+C'-treated or 2000-rads-irradiated B6-pretreated B6D2F1 spleen cells. Both types of resistance are observed in B6D2F1 hybrids pretreated with more than 2.5 X 10(7) B6 spleen cells.

Pretreatment of B6D2F1 hybrids by injection of B6 spleen cells by subcutaneous or intravenous routes induces specific resistance to the local graft versus host reaction provoked by s.c. engraftment of B6 spleen cells. This resistance has been attributed to the presence in the pretreated F1 hybrids of cytotoxic T lymphocytes directed against receptors that recognize the D2 alloantigens (anti-D2-receptor CTL). However, this hypothesis would seem to be challenged, at least partially, by our previously published results showing that a) when tested before induction of GVHR, the anti-D2-receptor CTL are detectable in F1 hybrids pretreated only by the s.c. route but not by the i.v. route; and b) specific resistance to GVHR observed in i.v.-pretreated F1 hybrids is mediated by a nylon-adherent, Thy-1-, radioresistant (2000 rads) suppressor cell of B6 origin that does not manifest any anti-D2-receptor CTL activity. However, these results did not allow us to exclude the possibility of the presence, in the i.v.-pretreated F1 hybrids, of anti-D2-receptor precursor CTL that could be reactivated during the GVHR by the D2-receptors expressed on the proliferating clone of grafted B6 cells, then differentiate to the receptor-specific CTL effectors that control the development of the GVHR. That is why we have studied in the present work the CTL activity developed against D2-receptors after induction of GVHR in either normal or resistant F1 hybrids. Our results show that F1 hybrids protected against GVHR by i.v. pretreatment with B6 cells or by a transfer of nylon-adherent spleen cells from i.v.-pretreated syngeneic F1 mice do not manifest enhanced anti-D2-receptor CTL activity. When considered along with our previous observations, these results favor our hypothesis that anti-D2-receptor CTL are not involved in the specific resistance to GVHR observed in the i.v.-pretreated F1 hybrids.