CD8(+) cell noncytotoxic anti-human immunodeficiency virus response inhibits expression of viral RNA but not reverse transcription or provirus integration.

CD8(+) T cells from human immunodeficiency virus (HIV)-infected individuals can suppress HIV replication in CD4(+) cells by a noncytotoxic mechanism that inhibits the expression of viral RNA. The present study examined whether other step(s) in the virus replicative cycle could be affected by the CD8(+) cells. Culturing HIV-infected CD4(+) T cells with antiviral CD8(+) T cells did not significantly reduce the amounts of (i) early HIV DNA reverse transcripts (detected by LTR-U3/R), (ii) total nuclear HIV gag DNA, or (iii) integrated proviral DNA. However, exposure to the CD8(+) T cells did cause a reduction in the amount of multiply spliced tat and full-length gag mRNA expressed by the infected CD4(+) T cells, confirming previous observations. The levels of glyceraldehyde-3-phosphate dehydrogenase and interleukin-2 receptor-alpha mRNA were not affected. The results support the conclusion that the noncytotoxic anti-HIV response of CD8(+) T cells, demonstrable in vitro, does not affect any of the virus replication steps leading to the integration of proviral HIV, but specifically interrupts the expression of viral RNA.

HIV virions and HIV infection in vitro are unaffected by human granzymes A and B.

Granzymes are a family of serine proteinases commonly found in the granules of CD8+ T cells. In HIV infection, CD8+ cells show cytotoxic and noncytotoxic antiviral activities. The latter is mediated, at least in part, by a secreted CD8+ cell antiviral factor, CAF. Because of the antiviral nature of CD8+ cells, we examined the potential anti-HIV activity of free granzymes that can be found in CD8+ cell culture fluids. Pretreatment of CD4+ T cells with granzyme A or granzyme B had no effect on their susceptibility to infection with HIV, nor did incubation of the granzymes with HIV virions alter their infectivity. Continuous culture of acutely infected CD4+ T cells with granzyme A or B showed no effect on cell viability or the replication of HIV. The findings of this study suggest that free granzymes do not control HIV infection and spread in CD4+ T cells.

Lack of differences in nef alleles among HIV-infected asymptomatic long-term survivors and those who progressed to disease.

Sequences of the human immunodeficiency virus (HIV) nef gene in virus isolates from 12 long-term survivors (LTSs) and 7 progressors were compared to determine if any association existed between the sequences and the corresponding clinical status. The sequences of at least five clones were determined for each subject. Conceptual translations of the open reading frames (ORFs) were examined with respect to a consensus with a prototypic nef sequence (HIV-1SF2) and for conservation of functionally described motifs. Premature stops were observed at equivalent, yet low, frequencies among the different clinical groups: 2 of 60 (3.33%) and 1 of 45 (2.22%) respectively. No remarkable differences in protein motifs implicated in several activities ascribed to Nef were noted. An association between nef sequence characteristics and the clinical state was not found.

HLA compatibility requirements for CD8(+)-T-cell-mediated suppression of human immunodeficiency virus replication.

CD8(+) T cells from human immunodeficiency virus (HIV)-infected individuals can suppress HIV replication in cultured CD4(+) cells by a noncytotoxic mechanism. Efficient suppression of HIV replication (>90% reduction) does not require HLA class I or class II histocompatibility between the effector CD8(+) T cells and the infected target CD4(+) T cells. However, maximal control of HIV production occurs when the CD8(+) effector cells and CD4(+) target cells are syngeneic. In some cases, more than 20-fold fewer syngeneic CD8(+) T cells were required to achieve the same degree of HIV inhibition as HLA-mismatched CD8(+) T cells. The increased antiviral activity seen in the syngeneic setting did not map exclusively to either the HLA class I or class II locus. These findings suggest that genetic compatibility (potentially, but not necessarily, at the HLA class I and class II loci) regulates CD8(+) T-cell noncytotoxic antiviral activity against infected CD4(+) T cells.

Virological and immunological features of long-term human immunodeficiency virus-infected individuals who have remained asymptomatic compared with those who have progressed to acquired immunodeficiency syndrome.

Infection with the human immunodeficiency virus (HIV) leads to a decrease in CD4(+) T cells and disease progression within a decade of seroconversion. However, a small group of infected people, despite being infected by HIV for 10 or more years, remain clinically asymptomatic and have stable CD4(+) cell counts without taking antiretroviral medication. To determine why these individuals, known as long-term survivors (LTS), remain healthy, the hematological profiles, viral load and properties, HIV coreceptor genotype, and anti-HIV immune responses of these people were compared with those of individuals who have progressed to disease (Progressors) over the same time period. Unlike Progressors, LTS have a low circulating viral load and a low number of HIV-infected cells. These differences in the levels of the viral load were not associated with a dominant biologic viral phenotype, varying growth kinetics of the virus, mutation in the cellular CCR5 gene, or the presence of neutralizing antibodies. Importantly, the difference in viral load could be explained by the enhanced ability of CD8(+) cells from LTS to suppress HIV replication.

Do beta-chemokines have clinical relevance in HIV infection?

The role of beta-chemokines in HIV infection was evaluated. The kinetics of regulated upon activation of normal T cell expressed and secreted, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein 1beta production by stimulated T lymphocytes did not differ substantially between HIV-infected (asymptomatic and with AIDS) and uninfected subjects. Maximal production of these beta-chemokines by activated peripheral blood cells was higher in the infected individuals than in uninfected individuals, but no significant difference was observed between healthy infected subjects and AIDS patients. Evaluation of the effect of HIV replication on beta-chemokine production indicated that acute infection of CD4+ T cells with non-syncytia-inducing (NSI) viruses generally increased beta-chemokine production two to eightfold, whereas with SI strains, it led to decreased production. The sensitivity of an individual's virus to beta-chemokine-mediated inhibition correlated with the NSI virus phenotype and a healthy clinical state. 50% of the AIDS patients, however, had NSI viruses that were sensitive to beta-chemokines. Finally, anti-beta-chemokine-neutralizing antibodies caused a more rapid release of HIV by CD4+ T cells naturally infected by NSI, but not SI, viruses indicating that endogenously produced chemokines can affect HIV production in culture. These findings suggest that beta-chemokines may affect HIV replication when an NSI virus is involved, but provide little evidence that they substantially influence HIV infection and pathogenesis.

Derivation of herpesvirus saimiri-transformed CD8+ T cell lines with noncytotoxic anti-HIV activity.

Herpesvirus saimiri (HVS), strain 488-77, was used to derive continuously growing transformed human CD8+ T cell lines that can suppress HIV replication in CD4+ cells via the production of an antiviral factor(s). Transformed CD8+ cell lines were obtained by HVS infection of peripheral blood mononuclear cells or purified CD8- T cells from HIV-infected or uninfected individuals. Suppression of primary or laboratory isolates of HIV was mediated by factor permeation of a transwell membrane or by cell-free culture supernatants. Suppressing and nonsuppressing cell lines were IL-2-dependent for good growth and showed a similar activated cell surface phenotype. The cell lines produced varying amounts of the cytokines IL-8, IL-10, TNF-alpha, TNF-beta, RANTES, MIP-1 alpha, and MIP-1 beta, but not IFN-alpha. No correlation was observed between the level of any of these cytokines and the presence or absence of antiviral activity in cell line culture supernatants. These cell lines have become an important resource for studying antiviral factors produced by CD8+ T cells from HIV-infected individuals.