Effect of long-term infection with nef-defective attenuated HIV type 1 on CD4+ and CD8+ T lymphocytes: increased CD45RO+CD4+ T lymphocytes and limited activation of CD8+ T lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4+ T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4+ and CD8+ T lymphocytes in these subjects, including the immunologically important naive (CD45RA+CD62L+), primed (CD45RO+), and activated (CD38+HLA-DR+ and CD28-) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4+ and CD8+ T lymphocytes, but had primed CD45RO+ CD4+ T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8+ T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1 RNA had normal levels of activated CD8+ T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4+ T lymphocyte subsets in vivo, and minimal activation of CD8+ T lymphocytes.     

Chronic colitis associated with HIV infection can be related to intraepithelial infiltration of the colon by CD8+ T lymphocytes

Gastrointestinal complications in AIDS patients with diarrhoea are common clinical manifestations, frequently diagnosed by colonoscopy as non-specific colitis. We retrospectively study colon biopsies diagnosed as chronic colitis associated with HIV (CCH). Biopsies were sorted as patients with AIDS (serum CD4 <200 cell/mm3) but without any clear infectious process (n = 12) and patients without HIV infection (n = 24). There are low numbers of CD4+ T lymphocytes in lamina propria of AIDS patients, but CD8+ T populations in this area appear to be similar in all studied groups, regardless of HIV infection or laboratory evidence of a specific agent. We found the clear evidence of CD8+ T cells infiltration in colonic mucosa in HIV patients with microscopic colitis. An imbalance of lymphocyte subpopulations in the colon, both in the lamina propria and epithelium, could result in an intraepithelial CD8 infiltration, involved in the pathogenesis of CCH in AIDS patients.     

New CD4+ and CD8+ T cell responses induced in chronically HIV type-1-infected patients after immunizations with an HIV type 1 lipopeptide vaccine

We showed that an anti-HIV lipopeptide vaccine injected to HIV-uninfected volunteers was well tolerated and able to induce a specific CD4(+) and CD8(+) T cell responses. The same vaccine was injected in HIV-1 chronically infected patients controlled by HAART to evaluate its immunogenicity. In this trial, 24 patients were immunized three times with a mixture of six lipopeptides (Nef 66-97, Nef 117-147, Nef 182-205, Gag 183-214, Gag 253-284, and Env 303-335) at 0, 3, and 6 weeks. We studied the HIV-1-specific CD4(+) T cell proliferative responses. The IFN-gamma secretion by activated CD8(+) T cells was evaluated, using an ex vivo ELISpot assay and 60 CD8(+) T cell epitopes derived from the vaccine. Before immunization (W0), anti-HIV CD4(+) T cell responses to Gag, Nef, and Env large peptides were detected in 7/23 (30%) analyzable patients. After three injections, 17/23 (74%) patients had a proliferative response and 16 of them induced new specific CD4(+) T cell responses. At W0, CD8(+) T cell responses to HIV-1 epitopes were detected in 6/23 (26%) patients. After vaccination, 16/23 (70%) patients showed CD8(+) T cell responses and 13 of these patients induced new T cell responses to 25 different HIV-1 epitopes. These HIV-1 epitopes were detected in patients with various HLA class I molecules (HLA-A2, -A3/A11, -A24, -B7 superfamily, -B8), as found in the majority of the white population. Lipopeptides induce new anti-HIV T cell responses in vaccinated infected patients and could be used as a new immunotherapy strategy. The majority of these responders induced specific new CD4(+) and CD8(+) T cell responses.     

Acquisition of HIV type 1 resistance by beta-chemokine-producing CD4+ T cells.

The CD4+ T cell is a major target cell type for human immunodeficiency virus type 1 (HIV-1) infection. In this study, we provide evidence that the susceptibility to HIV-1 infection is variable in individual CD4+ T cells. Five CD4+ T cell clones were isolated from an HIV-1-seronegative donor and were investigated for their susceptibility to HIV-1 infection. Four CD4+ T cell clones were resistant to infection by a macrophage-tropic (R5) HIV-1 isolate whereas one clone was fully permissive. The level of susceptibility to HIV-1 correlated inversely with beta-chemokine production, including RANTES (regulated on activation, normally T cell expressed and secreted), macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta. Resistance to HIV-1 infection was abrogated by the combined use of neutralizing antibodies against these three beta-chemokines. Interestingly, a complete inhibition of HIV-1 infection was observed in peripheral blood mononuclear cells on infection induced by adding the culture supernatant or a small number of HIV-1-resistant cell clones. Our results suggest the presence of a clonal self-defense mechanism within the CD4+ T cell population in vivo that involves the secretion of beta-chemokines.     

CD8+ cytotoxic T lymphocyte responses to lytic proteins of human herpes virus 8 in human immunodeficiency virus type 1-infected and -uninfected individuals

T cell immunity to lytic proteins of herpesviruses is important in host control of infection. We have characterized the cytotoxic T lymphocyte (CTL) response to 5 human herpesvirus 8 (HHV-8) homologues of lytic proteins in HHV-8-seropositive individuals. HLA class I-restricted, CD8(+) CTL responses to >/=1 HHV-8 lytic protein were detected in all 14 HHV-8-seropositive study subjects tested, with or without human immunodeficiency virus type 1 (HIV-1) infection, but not in any of 5 HHV-8-seronegative individuals. Seven of these study subjects with both HHV-8 and HIV-1 infection had greater anti-CTL reactivity to glycoprotein H (open-reading frame 22) than did the 7 study subjects infected only with HHV-8. Moreover, there was a strong, inverse correlation between HIV-1 load and glycoprotein H-specific CTL lysis in the study subjects infected with both viruses. CTL reactivity to HHV-8 lytic proteins may be involved in host control of HHV-8-related diseases, such as Kaposi's sarcoma.     

Propagation of CD4+ T cells specific for HIV type 1 envelope gp120 from chronically HIV type 1-infected subjects

HIV-specific CD4+ T cell responses, in particular to the HIV envelope antigen gp120, are often undetectable in the peripheral blood of HIV-infected individuals. The failure to detect these cells poses a significant impediment to studying the T cell populations that are considered to be essential for controlling HIV infection and has led to speculation that these cells are entirely depleted during HIV infection. This study was designed to test whether gp120-specific CD4+ T cells exist in HIV-infected subjects and can be expanded from peripheral blood mononuclear cells by in vitro stimulation with the gp120 antigen, allowing better characterization of these cells. Although gp120-specific T cell responses were barely observed in patient cells ex vivo before antigenic stimulation, CD4+ T cells specific for gp120 were successfully propagated from the blood of each asymptomatic chronically HIV-infected subject studied. The dominant epitopes recognized by gp120-specific CD4+ T cells from these HIV-infected subjects were mapped to well-conserved sites in the C1 and C2 domains of gp120. Two CD4+ T cell lines recognizing these two regions were subsequently established. The CD4+ T cell lines proliferated and produced interferon gamma in response to the specific epitopes, and the responses were MHC class II restricted. These T cell lines also exhibited cross-reactivity with gp120 from T cell line-adapted HIV-1 strains IIIB and MN, as well as with gp120 from primary isolates SF33 (subtype B), CA1 (subtype A), and CA10 (subtype A/E). The data demonstrate that CD4+ T cells specific for gp120 are not entirely depleted from the peripheral blood of chronically HIV-infected subjects; these cells are present in low numbers but can be expanded after antigenic stimulation in vitro.     

CD4+ and CD8+ lymphocytes and HIV RNA in HIV infection: high baseline counts and in particular rapid decrease of CD8+ lymphocytes predict AIDS

OBJECTIVE: To study the progression of HIV infection in relation to immunological and virological variables with emphasis on the role of CD8+ lymphocytes. DESIGN: Prospective follow-up from October 1991 of patients observed for at least 18 months allowing nucleoside analogue monotherapy. Peripheral CD4+ and CD8+ lymphocyte counts, HIV RNA, and soluble CD8 were analysed by statistics allowing the evaluation of serial data, avoiding time points with concurrent infections. SETTING: Tertiary university clinic. PATIENTS: Forty-nine patients were followed for 52.6 months, baseline CD4+ count of 300 x 10(6)/l, sample interval of 5.9 months (medians). MAIN OUTCOME MEASURES: AIDS, death, and CDC groups B- or C-related events. RESULTS: AIDS developed in 28% of patients. Baseline CD8+ counts above the median were significantly associated with AIDS development; the best Cox model included CD8+ cells and the log10RNA/CD4 ratio. A decline in CD8+ counts relative to baseline most significantly predicted AIDS, along with higher baseline RNA and actual CD4+ counts of less than 200 x 10(6)/l. Levels of soluble CD8 in the blood relative to total CD8+ cells significantly increased in patients developing AIDS. Death occurred in 16% of the patients, and was only predicted by high CD8+ cell counts at baseline. CDC B- and C-related events occurred in 35% of the patients and were best predicted by high baseline CD8+ counts and high RNA levels. CONCLUSIONS: The serial quantitation of CD8+ lymphocytes gave highly significant predictive information on the natural progression of HIV infection in patients with moderate to severe immune deficiency. Our data suggest that the hyperactivation of CD8+ lymphocytes is an important factor leading to a numerical decrease of CD8+ lymphocytes in progressive HIV infection.     

HIV type 1-infected dendritic cells induce apoptotic death in infected and uninfected primary CD4 T lymphocytes

In addition to their essential role in adaptive immunity, dendritic cells (DCs) participate in innate immunity. In the context of measles virus (MV) or cytomegalovirus infections, they develop cytotoxic functions that may contribute in vivo to the elimination of virus-infected cells, but that also kill infected and noninfected T lymphocytes. Because the human immunodeficiency virus (HIV) induces T cell depletion through mechanisms that are still obscure, we investigated its ability to trigger DC cytotoxicity. When incubated with HIV, monocyte-derived DCs induced apoptosis in MDA-231 cells, which are sensitive to MV-induced DC cytotoxicity, and in uninfected as well as HIV-infected H9 CD4+ T cell lines. This apoptosis was inhibited by a mixture of FasL, TRAIL, TNF-alpha, and TWEAK inhibitors. Indeed, HIV infection induced or enhanced sensitivity to TRAIL, TNF-alpha, and TWEAK in H9 cells. Moreover, dendritic cells incubated with HIV-1 BAL or a wildtype HIV-1 isolate induced apoptosis in autologous primary CD4+ T lymphocytes, infected or not with a wild-type HIV-1 isolate. Therefore, induction of DC cytotoxicity by HIV may be relevant to in vivo HIV infection. Induction of cytotoxicity in DCs by HIV might contribute to HIV-associated T cell depletion through induction of apoptosis, especially in the early stages of infection. It may also contribute to elimination of infected cells in vivo, thereby enhancing cross-presentation of HIV by DCs. Therefore this new cytotoxic function of DCs may play an important role in innate and adaptive immunity during HIV infection.     

Low expression of inhibitory natural killer receptors in CD8 cytotoxic T lymphocytes in long-term non-progressor HIV-1-infected patients

We investigated whether a different pattern of HLA-specific inhibitory natural killer receptor (iNKR) expression on peripheral blood mononuclear cells (PBMC) of long-term non-progressor (LTNP) patients explained their benign course of HIV-1 infection. The surface expression of p70, p140 and CD94/NKG2A in their CD3+CD8+ PBMC was comparable to that of uninfected donors. The lack of iNKR-mediated functional inhibition of HIV-1-specific cytotoxic T lymphocytes in vitro could provide an additional mechanism for the efficient control of virus spread in LTNP patients.     

HIV感染者/AIDS患者外周血CD38 HLA-DR分子在CD4+ CD8+T淋巴细胞上的表达

目的　观察国内艾滋病病毒 (HIV)感染者 /艾滋病 (AIDS)患者外周血CD38、HLA DR分子在CD+4 、CD+8T淋巴细胞上表达的变化 ,并探讨这些变化的临床意义。方法　用流式细胞仪检测 5 1例正常对照、14例HIV感染者和 3 6例AIDS患者的外周血CD+4 、CD+8T淋巴细胞表面的CD38、HLA DR分子的表达 ,用分枝DNA(bDNA)法检测 11例HIV感染者和 18例AIDS患者的血浆病毒载量。结果　CD+4 HLA DR+细胞百分比显示 ,AIDS组显著高于正常组及HIV组 ;CD+8HLA DR+T细胞百分比显示HIV组与AIDS组间无差异 ,而它们均显著高于正常组。CD+8、CD38+细胞百分比则是AIDS组 >HIV组 >正常组 ,CD+8CD38+、CD+8HLA DR+、CD+4 HLA DR+细胞百分比与病毒载量显著正相关。结论　在HIV感染过程中 ,HLA -DR+、CD38+在CD+4 、CD+8T淋巴细胞上的表达均显著增加 ,反映T淋巴细胞异常激活 ;尤其是CD+8CD38+细胞百分比随着疾病进展逐渐升高 ,预示疾病进展程度。在评价HIV感染者和AIDS患者的免疫状况时 ,不仅要考虑免疫细胞数量和功能的变化 ,还应考虑免疫细胞的激活水平     

CD8+ T lymphocytes and progression to AIDS in HIV-infected men: some observations

The relationship between CD8+ lymphocyte counts and progression to AIDS was studied in 340 HIV-1-seropositive men participating in a population-based prospective study. Overall, the relative hazard for developing AIDS during 60 months of observation was slightly elevated (1.08, P = 0.003), indicating an 8% increase in risk of progression for every 100 CD8+ cell count increment. When the data were analyzed in relation to date of diagnosis, the relative hazard was depressed (0.90, P less than 0.001) for the period 6 months prior to diagnosis, but was close to 1.0 for the period 6-36 months prior to diagnosis. These findings suggest a complex relationship between CD8+ cell counts and progression to AIDS, with the possibility that various subsets of the CD8+ compartment play different roles.     

Regulation of lck degradation and refractory state in CD8+ cytotoxic T lymphocytes

After specific activation, CD8+ cytotoxic T lymphocytes (CTLs) enter a refractory state termed activation-induced nonresponsiveness (AINR) that is characterized by the inability of T cells to respond to a secondary stimulus. Here, we show that T cell receptor triggering results in rapid degradation of the src-family protein kinase lck through a mechanism that is proteasome- and lysosome-independent, sensitive to cysteine protease inhibitors, and distinct from the pathways involved in degradation of ZAP-70 kinase or zeta-chain of the CD3 complex. Pharmacologic blockade of lck degradation, as well as transfection of refractory cells with an lck expression vector, increased responsiveness of CTLs to repeated antigenic challenge. The development or maintenance of AINR was not affected by exogenously added IL-2, whereas IL-15 or IFN-alpha restored both lck expression and responsiveness of preactivated CTLs. Our results suggest that lck degradation plays an important role in the development of AINR in human CTLs and that this condition can be reverted by pharmacologic agents or lymphokines that prevent lck degradation or induce its expression.     

Cytomegalovirus rather than HIV triggers the outgrowth of effector CD8+CD45RA+CD27- T cells in HIV-1-infected children

OBJECTIVE: To analyse the effect of viral coinfections on immune reconstitution in HIV-1-infected children (< 18 years) taking highly active antiretroviral therapy (HAART). METHODS: Absolute lymphocyte numbers of various subsets of CD8 T cells were measured. RESULTS: Prior cytomegalovirus (CMV) infection correlated with an increased number of CD8 effector T cells (i.e., CD45RA+CD27-) at baseline (CMV-seropositive versus CMV-seronegative patients; P = 0.009), as well as an increased state of T cell activation as defined by HLA-DR and CD38 expression. The expansion of effector CD8 T cells persisted over time, independent of the HIV response to HAART. Numbers of CD8 effector T cells were significantly higher in patients with CMV replication as reflected by persistent urinary CMV shedding and periodic CMV DNAaemia (P = 0.02). These patients also showed an increase in CMV-specific antibodies compared with those without CMV shedding (P = 0.007). The number of CMV-specific interferon-gamma (IFN-gamma)-producing CD8 T cells was lower in children who persistently shed CMV compared with those who did not (P = 0.02). In contrast, CMV-specific CD4 T cell responses were detected at similar levels in both groups. CONCLUSIONS: In HIV-1-infected children, CMV infection correlated with the outgrowth of CD8+CD45RA+CD27- effector T cells. Activation of the immune system by persistent CMV secretion resulted in increasing CMV-specific IgG and higher numbers of CD8 effector T cells. Despite these increases, the CMV-specific IFN-gamma-producing CD8 T cell response was diminished, which could explain the inability to suppress CMV completely in 41% of HIV-1-infected children.     

Activation of HIV type 1 specific cytotoxic T lymphocytes from semen by HIV type 1 antigen-presenting dendritic cells and IL-12

Seminal HIV-1-specific cytotoxic T lymphocytes (CTLs) could provide an important immune defense against local HIV-1 infection, and be important in impeding the spread of HIV-1 infection. In this study, we demonstrate that autologous blood-derived dendritic cells (DCs) loaded in vitro with synthetic HIV-1 peptides representing known CTL epitopes activated HLA class I restricted, anti-HIV-1 CTLs and interferon gamma responses in seminal CD8+ T cells from subjects with chronic HIV-1 infection on antiretroviral therapy. CTLs specific for the same HLA-restricted epitopes were detected in semen and blood of the same individuals by stimulation with peptide-loaded DCs. Anti-HIV-1 CTL responses from semen were enhanced by stimulation with DCs loaded with HIV-1 peptides and interleukin 12. Our results suggest that blood-derived DCs have HIV-1 antigen-presenting capacity for seminal CTL in HIV-1-infected subjects. The DC-T cell system can serve as a model for immunotherapy of HIV-1 infection in the local genital tract as well as systemic blood circulation.     

The law of mass action governs antigen-stimulated cytolytic activity of CD8+ cytotoxic T lymphocytes.

An analysis of the initial antigen-recognition step in the destruction of target cells by CD8+ cytolytic T lymphocytes (CTLs) shows that a relationship in the form of the law of mass action can be used to describe interactions between antigen-specific receptors on T cells (TCRs) and their natural ligands on target cells (peptide-major histocompatibility protein complexes, termed pepMHC complexes), even though these reactants are confined to their respective cell membranes. For a designated level of lysis and receptor affinities below about 5 X 10(6) M-1, the product of the required number of pepMHC complexes per target cell ("epitope density") and TCR affinity for pepMHC complexes is constant; therefore, over this range TCR affinities can be predicted from epitope densities (or vice versa). At higher receptor affinities ("affinity ceiling") the epitope density required for half-maximal lysis reaches a lower limit of less than 10 complexes per target cell.     

Primary induction of human CD8+ cytotoxic T lymphocytes and interferon-gamma-producing T cells after smallpox vaccination

This study measured the ability of a standard smallpox vaccine, given by scarification (by bifurcated needle), to induce primary human vaccinia virus-specific cytotoxic and interferon (IFN)-gamma-producing T lymphocyte responses. Because protection against smallpox may be mediated in part by T cell memory responses induced by vaccination, an analysis of the induction of primary human cytotoxic T lymphocytes (CTL) and IFN-gamma-producing T cell responses was performed. Although smallpox is no longer an epidemic threat under natural conditions, vaccination is still recommended for persons working with vaccinia viruses in the laboratory and for those who may be at risk from the potential use of smallpox virus as a bioterrorism agent. The results demonstrate that smallpox vaccine given by bifurcated needle induces strong vaccinia virus-specific CD8(+) CTL and IFN-gamma-producing T cell responses and provide baseline information useful for planning the immunologic assessment of future smallpox vaccines.