Weak anti-HIV CD8(+) T-cell effector activity in HIV primary infection.

HIV-specific CD8(+) T cells play a major role in the control of virus during HIV primary infection (PI) but do not completely prevent viral replication. We used IFN-gamma enzyme-linked immunospot assay and intracellular staining to characterize the ex vivo CD8(+) T-cell responses to a large variety of HIV epitopic peptides in 24 subjects with early HIV PI. We observed HIV-specific responses in 71% of subjects. Gag and Nef peptides were more frequently recognized than Env and Pol peptides. The number of peptides recognized was low (median 2, range 0-6). In contrast, a much broader response was observed in 30 asymptomatic subjects with chronic infection: all were responders with a median of 5 peptides recognized (range 1-13). The frequency of HIV-specific CD8(+) T cells among PBMC for a given peptide was of the same order of magnitude in both groups. The proportion of HIV-specific CD8(+)CD28(-) terminally differentiated T cells was much lower in PI than at the chronic stage of infection. The weakness of the immune response during HIV PI could partially account for the failure to control HIV. These findings have potential importance for defining immunotherapeutic strategies and establishing the goals for effective vaccination.

Direct evidence to support the role of antigen-specific CD8(+) T cells in melanoma-associated vitiligo.

Vitiligo is a cutaneous pigmentary disorder characterized by the loss of melanocytes. An autoimmune mechanism is strongly suspected to be involved in this affection given that it is frequently associated with autoimmune hormonal disorders, and because antibodies directed against melanocytic antigens are found in the serum of patients with vitiligo. We examined the role of cellular immunity in melanoma-associated vitiligo by expanding infiltrating lymphocytes from fresh biopsy specimens of vitiligo patches in melanoma patients. The vitiligo-infiltrating lymphocytes were almost exclusively T lymphocytes, and most were CD8(+). Following in vitro expansion, vitiligo-infiltrating lymphocytes remained predominantly CD8(+) and expressed the cutaneous homing receptor CLA. Furthermore, vitiligo-infiltrating lymphocytes had a clonal or oligoclonal T cell receptor profile, possibly reflecting specific antigenic stimulation. Finally, vitiligo- infiltrating lymphocytes specifically recognized differentiation antigens shared by normal melanocytes and melanoma cells. This direct demonstration of CD8(+) T cell involvement in vitiligo suggests that, in melanoma patients, vitiligo may be a visible effect of a spontaneous antitumoral immune response.

Spontaneous and Fas-induced apoptosis of low-grade MDS erythroid precursors involves the endoplasmic reticulum.

Spontaneous apoptosis of bone marrow erythroid precursors accounts for the anemia that characterizes most low-grade myelodysplastic syndromes (MDS). We have shown that death of these precursors involved the Fas-dependent activation of caspase-8. To explore the pathway leading from caspase-8 activation to apoptosis, we transduced MDS bone marrow CD34(+) cells with a lentivirus encoding wild-type (WT) or endoplasmic reticulum (ER)-targeted Bcl-2 protein before inducing their erythroid differentiation. Both WT-Bcl-2 and ER-targeted Bcl-2 prevented spontaneous and Fas-dependent apoptosis in MDS erythroid precursors. ER-targeted Bcl-2 inhibited mitochondrial membrane depolarization and cytochrome c release in MDS erythroid precursors undergoing apoptosis, indicating a role for the ER in the death pathway, upstream of the mitochondria. MDS erythroid precursors demonstrated elevated ER Ca(2+) stores and these stores remained unaffected by ER-targeted Bcl-2. The ER-associated protein Bcl-2-associated protein (BAP) 31 was cleaved by caspase-8 in MDS erythroid precursors undergoing apoptosis. The protective effect of ER-targeted Bcl-2 toward spontaneous and Fas-induced apoptosis correlated with inhibition of BAP31 cleavage. A protective effect of erythropoietin against Fas-induced BAP31 cleavage and apoptosis was observed. We propose that apoptosis of MDS erythroid precursors involves the ER, downstream of Fas and upstream of the mitochondria, through the cleavage of the ER-associated BAP31 protein.

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-gamma-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.

Broad, intense anti-human immunodeficiency virus (HIV) ex vivo CD8(+) responses in HIV type 1-infected patients: comparison with anti-Epstein-Barr virus responses and changes during antiretroviral therapy.

The ex vivo antiviral CD8(+) repertoires of 34 human immunodeficiency virus (HIV)-seropositive patients with various CD4(+) T-cell counts and virus loads were analyzed by gamma interferon enzyme-linked immunospot assay, using peptides derived from HIV type 1 and Epstein-Barr virus (EBV). Most patients recognized many HIV peptides, with markedly high frequencies, in association with all the HLA class I molecules tested. We found no correlation between the intensity of anti-HIV CD8(+) responses and the CD4(+) counts or virus load. In contrast, the polyclonality of anti-HIV CD8(+) responses was positively correlated with the CD4(+) counts. The anti-EBV responses were significantly less intense than the anti-HIV responses and were positively correlated with the CD4(+) counts. Longitudinal follow-up of several patients revealed the remarkable stability of the anti-HIV and anti-EBV CD8(+) responses in two patients with stable CD4(+) counts, while both antiviral responses decreased in two patients with obvious progression toward disease. Last, highly active antiretroviral therapy induced marked decreases in the number of anti-HIV CD8(+) T cells, while the anti-EBV responses increased. These findings emphasize the magnitude of the ex vivo HIV-specific CD8(+) responses at all stages of HIV infection and suggest that the CD8(+) hyperlymphocytosis commonly observed in HIV infection is driven mainly by virus replication, through intense, continuous activation of HIV-specific CD8(+) T cells until ultimate progression toward disease. Nevertheless, highly polyclonal anti-HIV CD8(+) responses may be associated with a better clinical status. Our data also suggest that a decrease of anti-EBV CD8(+) responses may occur with depletion of CD4(+) T cells, but this could be restored by highly active antiretroviral treatment.

Evolution of cytotoxic T lymphocyte responses to human immunodeficiency virus type 1 in patients with symptomatic primary infection receiving antiretroviral triple therapy.

The impact of highly active antiretroviral treatment (HAART) on anti-human immunodeficiency virus (HIV) cytotoxic T lymphocytes (CTL) was studied in 17 patients with recent symptomatic HIV-1 primary infection receiving triple combination therapy. Anti-HIV CTL were initially detected in 15 patients. In 6, CTL disappeared rapidly and persistently after initiation of therapy. Most of them had a rapid and sustained decrease in plasma HIV RNA to undetectable levels. Conversely, in 6 other patients, CTL remained detectable, which was associated with a less efficient control of viral replication. In 3 others, CTL disappeared only transiently, without clear correlation with the virologic profile. Altogether, despite individual variations, there was a positive correlation between viral replication and anti-HIV-1 cytotoxicity in most subjects, suggesting that the persistence of viral antigens is the main determinant for the maintenance of CTL activity. This raises the question of the potential benefit of anti-HIV CTL induction by immunotherapy in acute seroconverters treated by HAART.