Combination Immune Checkpoint Blockade Enhances IL-2 and CD107a Production from HIV-Specific T Cells Ex Vivo in People Living with HIV on Antiretroviral Therapy.

In people with HIV (PWH) on antiretroviral therapy (ART), immune dysfunction persists, including elevated expression of immune checkpoint (IC) proteins on total and HIV-specific T cells. Reversing immune exhaustion is one strategy to enhance the elimination of HIV-infected cells that persist in PWH on ART. We aimed to evaluate whether blocking CTL-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), T cell Ig domain and mucin domain 3 (TIM-3), T cell Ig and ITIM domain (TIGIT) and lymphocyte activation gene-3 (LAG-3) alone or in combination would enhance HIV-specific CD4+ and CD8+ T cell function ex vivo. Intracellular cytokine staining was performed using human PBMCs from PWH on ART (n = 11) and expression of CD107a, IFN-γ, TNF-α, and IL-2 was quantified with HIV peptides and Abs to IC. We found the following: 1) IC blockade enhanced the induction of CD107a and IL-2 but not IFN-γ and TNF-α in response to Gag and Nef peptides; 2) the induction of CD107a and IL-2 was greatest with multiple combinations of two Abs; and 3) Abs to LAG-3, CTLA-4, and TIGIT in combinations showed synergistic induction of IL-2 in HIV-specific CD8+ and CD107a and IL-2 production in HIV-specific CD4+ and CD8+ T cells. These results demonstrate that the combination of Abs to LAG-3, CTLA-4, or TIGIT can increase the frequency of cells expressing CD107a and IL-2 that associated with cytotoxicity and survival of HIV-specific CD4+ and CD8+ T cells in PWH on ART. These combinations should be further explored for an HIV cure.

Immunogenicity and tolerability of an inactivated and adjuvanted pandemic H1N1 influenza vaccine, in HIV-1-infected patients.

We evaluated the efficacy and tolerability of a single dose of the split virion AS03-adjuvanted pandemic H1N1 influenza vaccine (A/California/7/2009) in 84 HIV-1 infected individuals. Antibody titers were determined by hemagglutination inhibition assay and by microneutralization. Vaccine was well tolerated. At 21 days post vaccination, 56 (67%) patients had seroconverted. There was no correlation between baseline CD4 cell count (p=0.539) or HIV viral load (p=0.381) and immune response. Other vaccine strategies should be evaluated in this HIV population, to improve response rates.

Visualizing the course of antigen-specific CD8 and CD4 T cell responses to a growing tumor.

Spontaneous tumors frequently express antigens that can be recognized by the immune system but nevertheless manage to evade immune surveillance. To better understand the mechanism of evasion, we followed CD8 and CD4 T cells reacting against a subcutaneously growing tumor, modified to express influenza hemagglutinin (HA) as surrogate tumor antigen. Adoptive transfer of 8,000 antigen-specific CD8 T cells was sufficient to protect against challenge with 1x10(6) tumor cells, while larger numbers of T cells rejected established tumors. HA-specific CD4 T cells could not reject tumors on their own but helped rejection by CD8 T cells. Rejection of the tumor coincided with prolonged survival of expanded antigen-specific CD8 and CD4 T cells, while a failing anti-tumor response was accompanied by transient expansion followed by rapid elimination of antigen-specific T cells. Thus, a highly immunogenic tumor can evade immune surveillance because of an insufficient number of tumor-specific T cells and antigen overload, resulting in exhaustion of the immune response. In this scenario, adoptive immunotherapy rather than vaccination promises successful treatment.

Prevalent role of TCR alpha-chain in the selection of the preimmune repertoire specific for a human tumor-associated self-antigen.

The specificity of recognition of pMHC complexes by T lymphocytes is determined by the V regions of the TCR alpha- and beta-chains. Recent experimental evidence has suggested that Ag-specific TCR repertoires may exhibit a more V alpha- than V beta-restricted usage. Whether V alpha usage is narrowed during immune responses to Ag or if, on the contrary, restricted V alpha usage is already defined at the early stages of TCR repertoire selection, however, has remained unexplored. Here, we analyzed V and CDR3 TCR regions of single circulating naive T cells specifically detected ex vivo and isolated with HLA-A2/melan-A peptide multimers. Similarly to what was previously observed for melan-A-specific Ag-experienced T cells, we found a relatively wide V beta usage, but a preferential V alpha 2.1 usage. Restricted V alpha 2.1 usage was also found among single CD8(+) A2/melan-A multimer(+) thymocytes, indicating that V alpha-restricted selection takes place in the thymus. V alpha 2.1 usage, however, was independent from functional avidity of Ag recognition. Thus, interaction of the pMHC complex with selected V alpha-chains contributes to set the broad Ag specificity, as underlined by preferential binding of A2/melan-A multimers to V alpha 2.1-bearing TCRs, whereas functional outcomes result from the sum of these with other interactions between pMHC complex and TCR.