Extensive HLA class I allele promiscuity among viral CTL epitopes.

Promiscuous binding of T helper epitopes to MHC class II molecules has been well established, but few examples of promiscuous class I-restricted epitopes exist. To address the extent of promiscuity of HLA class I peptides, responses to 242 well-defined viral epitopes were tested in 100 subjects regardless of the individuals' HLA type. Surprisingly, half of all detected responses were seen in the absence of the originally reported restricting HLA class I allele, and only 3% of epitopes were recognized exclusively in the presence of their original allele. Functional assays confirmed the frequent recognition of HLA class I-restricted T cell epitopes on several alternative alleles across HLA class I supertypes and encoded on different class I loci. These data have significant implications for the understanding of MHC class I-restricted antigen presentation and vaccine development.

De novo generation of escape variant-specific CD8+ T-cell responses following cytotoxic T-lymphocyte escape in chronic human immunodeficiency virus type 1 infection.

Human immunodeficiency virus type 1 (HIV-1) evades CD8(+) T-cell responses through mutations within targeted epitopes, but little is known regarding its ability to generate de novo CD8(+) T-cell responses to such mutants. Here we examined gamma interferon-positive, HIV-1-specific CD8(+) T-cell responses and autologous viral sequences in an HIV-1-infected individual for more than 6 years following acute infection. Fourteen optimal HIV-1 T-cell epitopes were targeted by CD8(+) T cells, four of which underwent mutation associated with dramatic loss of the original CD8(+) response. However, following the G(357)S escape in the HLA-A11-restricted Gag(349-359) epitope and the decline of wild-type-specific CD8(+) T-cell responses, a novel CD8(+) T-cell response equal in magnitude to the original response was generated against the variant epitope. CD8(+) T cells targeting the variant epitope did not exhibit cross-reactivity against the wild-type epitope but rather utilized a distinct T-cell receptor Vbeta repertoire. Additional studies of chronically HIV-1-infected individuals expressing HLA-A11 demonstrated that the majority of the subjects targeted the G(357)S escape variant of the Gag(349-359) epitope, while the wild-type consensus sequence was significantly less frequently recognized. These data demonstrate that de novo responses against escape variants of CD8(+) T-cell epitopes can be generated in chronic HIV-1 infection and provide the rationale for developing vaccines to induce CD8(+) T-cell responses directed against both the wild-type and variant forms of CD8 epitopes to prevent the emergence of cytotoxic T-lymphocyte escape variants.

HLA-B63 presents HLA-B57/B58-restricted cytotoxic T-lymphocyte epitopes and is associated with low human immunodeficiency virus load.

Several HLA class I alleles have been associated with slow human immunodeficiency virus (HIV) disease progression, supporting the important role HLA class I-restricted cytotoxic T lymphocytes (CTL) play in controlling HIV infection. HLA-B63, the serological marker for the closely related HLA-B*1516 and HLA-B*1517 alleles, shares the epitope binding motif of HLA-B57 and HLA-B58, two alleles that have been associated with slow HIV disease progression. We investigated whether HIV-infected individuals who express HLA-B63 generate CTL responses that are comparable in breadth and specificity to those of HLA-B57/58-positive subjects and whether HLA-B63-positive individuals would also present with lower viral set points than the general population. The data show that HLA-B63-positive individuals indeed mounted responses to previously identified HLA-B57-restricted epitopes as well as towards novel, HLA-B63-restricted CTL targets that, in turn, can be presented by HLA-B57 and HLA-B58. HLA-B63-positive subjects generated these responses early in acute HIV infection and were able to control HIV replication in the absence of antiretroviral treatment with a median viral load of 3,280 RNA copies/ml. The data support an important role of the presented epitope in mediating relative control of HIV replication and help to better define immune correlates of controlled HIV infection.

Anti-viral activity of human antithrombin III.

Soluble inhibitory factors produced by CD8+ T-cells have been shown to inhibit HIV-1 replication and may play a critical role in vivo in anti-viral host defense. CD8+ T-cell-modified antithrombin III (ATIII) accounts for some of the described CD8+ T-cell anti-viral activity. We demonstrate that CD4+ T-cells, CD8+ T-cells, and natural killer cells react to an ATIII gradient by cell migration. Furthermore, exogenously added ATIII induced a G-protein-coupled signal transduction process in CD4+ T-cells and inhibited TNF-alpha-induced NF-kappaB activation. Heat and/or heparin treatment prior to the anti-viral inhibition test increased the anti-HIV activity up to 1000-fold. Our data indicate that anti-viral inactive ATIII can be activated having promising anti-viral properties as complementary candidate for the treatment of HIV infection.

HIV-1 antiviral activity of recombinant natural killer cell enhancing factors, NKEF-A and NKEF-B, members of the peroxiredoxin family.

CD8(+) T-cells are a major source for the production of non-cytolytic factors that inhibit HIV-1 replication. In order to characterize further these factors, we analyzed gene expression profiles of activated CD8(+) T-cells using a human cDNA expression array containing 588 human cDNAs. mRNA for the chemokine I-309 (CCL1), the cytokines granulocyte-macrophage colony-stimulating factor and interleukin-13, and natural killer cell enhancing factors (NKEF) -A and -B were up-regulated in bulk CD8(+) T-cells from HIV-1 seropositive individuals compared with seronegative individuals. Recombinant NKEF-A and NKEF-B inhibited HIV-1 replication when exogenously added to acutely infected T-cells at an ID(50) (dose inhibiting HIV-1 replication by 50%) of approximately 130 nm (3 microg/ml). Additionally, inhibition against dual-tropic simian immunodeficiency virus and dual-tropic simian-human immunodeficiency virus was found. T-cells transfected with NKEF-A or NKEF-B cDNA were able to inhibit 80-98% HIV-1 replication in vitro. Elevated plasma levels of both NKEF-A and NKEF-B proteins were detected in 23% of HIV-infected non-treated individuals but not in persons treated with highly active antiviral therapy or uninfected persons. These results indicate that the peroxiredoxin family members NKEF-A and NKEF-B are up-regulated in activated CD8(+) T-cells in HIV infection, and suggest that these antioxidant proteins contribute to the antiviral activity of CD8(+) T-cells.