Boosters of a therapeutic HIV-1 vaccine induce divergent T cell responses related to regulatory mechanisms

AbstractTherapeutic human immunodeficiency virus (HIV) vaccines aim to reduce disease progression by inducing HIV-specific T cells. Vacc-4x are peptides derived from conserved domains within HIV-1 p24 Gag. Previously, Vacc-4x induced T cell responses in 90% of patients which were associated with reduced viral loads. Here we evaluate the effects of Vacc-4x boosters on T cell immunity and immune regulation seven years after primary immunization. Twenty-five patients on effective antiretroviral therapy received two Vacc-4x doses four weeks apart and were followed for 16 weeks. Vacc-4x T cell responses were measured by proliferation (CFSE), INF-γ, CD107a, Granzyme B, Delayed-Type Hypersensitivity test (DTH) and cytokines and chemokines (Luminex). Functional regulation of Vacc-4x-specific T cell proliferation was estimated in vitro using anti-IL-10 and anti-TGF-ß monoclonal antibodies.Vacc-4x-specific CD8+ T cell proliferation increased in 80% after either the first (64%) or second (16%) booster. Only 40% remained responders after two boosters with permanently increased Vacc-4x-specific proliferative responses (p=0.005) and improved CD8+ T cell degranulation, IFN-γ production and DTH. At baseline, responders had higher CD8+ T cell degranulation (p=0.05) and CD4+ INF-γ production (p=0.01), whereas non-responders had higher production of proinflammatory TNF-α, IL-1α and IL-1ß (p<0.045) and regulatory IL-10 (p=0.07).Notably, IL-10 and TGF-ß mediated downregulation of Vacc-4x-specific CD8+ T cell proliferation increased only in non-responders (p<0.001). Downregulation during the study correlated to higher PD-1 expression on Vacc-4x-specific CD8+ T cells (r=0.44, p=0.037), but was inversely correlated to changes in Vacc4x-specific CD8+ T cell proliferation (r=−0.52, p=0.012).These findings show that Vacc-4x boosters can improve T cell responses in selected patients, but also induce vaccine-specific downregulation of T cell responses in others. Broad surveillance of T cell functions during immunization may help to individualize boosting, where assessment of vaccine-related immune regulation should be further explored as a potential new parameter

Immunization with HIV protease peptides linked to syngeneic erythrocytes

New potent vaccine adjuvants are desirable for increasing the efficacy of novel vaccine modalities such as DNA and peptides. We therefore tested if syngeneic erythrocytes could serve as delivery vectors for selected HIV peptides and compared the potency of these constructs to immunization with peptides in phosphate buffered saline or in incomplete Freunds adjuvant. Immunization of mice with peptides in a low dose (5 ng) coupled to erythrocytes induced a weak immune response in mice. These peptides alone (5 μg) gave no immune responses, while formulating the peptides (50 μg) in IFA induced strong homologous immunity as well as prominent cross reactivity to a related mutant epitope. Thus, vaccine delivery using syngeneic erythrocytes, although attractive for clinical use, might be of limited value due to the low amount of antigen that can be loaded per erythrocyte

The receptors for gibbon ape leukemia virus and amphotropic murine leukemia virus are not downregulated in productively infected cells

<p>Abstract</p> <p>Background</p> <p>Over the last several decades it has been noted, using a variety of different methods, that cells infected by a specific gammaretrovirus are resistant to infection by other retroviruses that employ the same receptor; a phenomenon termed receptor interference. Receptor masking is thought to provide an earlier means of blocking superinfection, whereas receptor down regulation is generally considered to occur in chronically infected cells.</p> <p>Results</p> <p>We used replication-competent GFP-expressing viruses containing either an amphotropic murine leukemia virus (A-MLV) or the gibbon ape leukemia virus (GALV) envelope. We also constructed similar viruses containing fluorescence-labeled Gag proteins for the detection of viral particles. Using this repertoire of reagents together with a wide range of antibodies, we were able to determine the presence and availability of viral receptors, and detect viral envelope proteins and particles presence on the cell surface of chronically infected cells.</p> <p>Conclusions</p> <p>A-MLV or GALV receptors remain on the surface of chronically infected cells and are detectable by respective antibodies, indicating that these receptors are not downregulated in these infected cells as previously proposed. We were also able to detect viral envelope proteins on the infected cell surface and infected cells are unable to bind soluble A-MLV or GALV envelopes indicating that receptor binding sites are masked by endogenously expressed A-MLV or GALV viral envelope. However, receptor masking does not completely prevent A-MLV or GALV superinfection.</p