BackgroundSeveral soluble factors have been reported to have the capacity of inhibiting HIV replication at different steps of the virus life cycle, without eliminating infected cells and through enhancement of specific cellular mechanisms. Yet, it is unclear if these antiviral factors play a role in the protection from HIV infection or in the control of viral replication. Here we evaluated two cohorts: i) one of 58 HIV-exposed seronegative individuals (HESNs) who were compared with 59 healthy controls (HCs), and ii) another of 13 HIV-controllers who were compared with 20 HIV-progressors. Peripheral blood, oral and genital mucosa and gut-associated lymphoid tissue (GALT) samples were obtained to analyze the mRNA expression of ELAFIN, APOBEC3G, SAMHD1, TRIM5α, RNase 7 and SerpinA1 using real-time PCR.ResultsHESNs exhibited higher expression of all antiviral factors in peripheral blood mononuclear cells (PBMCs), oral or genital mucosa when compared with HCs. Furthermore, HIV-controllers exhibited higher levels of SerpinA1 in GALT.ConclusionsThese findings suggest that the activity of these factors is compartmentalized and that these proteins have a predominant role depending on the tissue to avoid the infection, reduce the viral load and modulate the susceptibility to HIV infection.
Human immunodeficiency virus type-1 (HIV-1) infection represents one of the biggest public health problems worldwide. The immune response, mainly the effector mechanisms mediated by CD8 T cells, induces the selection of mutations that allows the virus to escape the immune control. These mutations are generally selected within CD8 T cell epitopes restricted to human leukocyte antigen class I (HLA-I), leading to a decrease in the presentation and recognition of the epitope, decreasing the activation of CD8 T cells. However, these mutations may also affect cellular processing of the peptide or recognition by the T cell receptor. Escape mutations often carry a negative impact in viral fitness that is partially or totally compensated by the selection of compensatory mutations. The selection of either escape mutations or compensatory mutations may negatively affect the course of the infection. In addition, these mutations are a major barrier for the development of new therapeutic strategies focused on the induction of specific CD8 T cell responses.
The CT26 model is one of the most widely tested systems for cancer immunotherapy. Over 70% of the CD8+ CTL responses in CT26 tumors are directed against two peptides: SPSYVYHQF (AH1) presented by H-2Ld, or GGPESFYCASW (GSW11) presented by H-2Dd. Both peptides derive from the ecotropic murine leukaemia virus gp70 envelope glycoprotein, which is the highest expressed gene in CT26, and have relative low affinity values for their respective MHC-I. However, there is a lack of knowledge about other CTL specificities in CT26, the relationship between abundance and affinity of such peptides, and their roles in tumor rejection.
We identified 96 potential epitopes restricted by MHC-I molecules in BALB/c mice based on previously published immuno-transcriptomic data. We used a mathematical algorithm integrating the peptides relative affinity to MHC-I measured by NetMHC4.0, and their abundance in the proteome, which resulted in a prediction of the likelihood of peptide presentation.
Screening was performed in splenocytes from Treg-depleted CT26-challenged mice via IFNγ intracellular cytokine staining and T cell proliferation assays. Our approach led to the identification of a novel CTL specificity restricted by H-2Kd (Kd34), which shows moderate IFNγ responses in splenocytes from mice responding to the therapy. Moreover, using Kd34-specific dextramers, we were able to detect a small population of tumor-infiltrating lymphocytes (TILs) specific for this peptide, with similar phenotypic traits to AH1- and GSW1-specific TILs. The identification of such novel CD8+ T cell specificities will improve the understanding about the relationship between immunodominance and epitope abundance/affinity to better tailor vaccine strategies in cancer.
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