Chemoattractant factors and the control of human immunodeficiency virus replication

Identification of Host PDZ-Based Interactions with the SARS-CoV-2 E Protein in Human Monocytes

Proteins containing PDZ (post-synaptic density, PSD-95/disc large, Dlg/zonula occludens, ZO-1) domains assemble signaling complexes that orchestrate cell responses. Viral pathogens target host PDZ proteins by coding proteins containing a PDZ-binding motif (PBM). The presence of a PBM in the SARS-CoV-2 E protein contributes to the virus's pathogenicity. SARS-CoV-2 infects epithelia, but also cells from the innate immune response, including monocytes and alveolar macrophages. This process is critical for alterations of the immune response that are related to the deaths caused by SARS-CoV-2. Identification of E-protein targets in immune cells might offer clues to understanding how SARS-CoV-2 alters the immune response. We analyzed the interactome of the SARS-CoV-2 E protein in human monocytes. The E protein was expressed fused to a GFP tag at the amino terminal in THP-1 monocytes, and associated proteins were identified using a proteomic approach. The E-protein interactome provided 372 partners; only 8 of these harbored PDZ domains, including the cell polarity protein ZO-2, the chemoattractant IL-16, and syntenin. We addressed the expression and localization of the identified PDZ proteins along the differentiation of primary and THP-1 monocytes towards macrophages and dendritic cells. Our data highlight the importance of identifying the functions of PDZ proteins in the maintenance of immune fitness and the viral alteration of inflammatory response.

Enhancing of anti-viral activity against HIV-1 by stimulation of CD8+ T cells with thymic peptides

HIV-1 can be neutralized by soluble factors produced and secreted by activated CD8+ T cells. Production of such anti-viral CD8 factors (including chemokines) can be induced with IL-2 or phytohaemagglutinin (PHA). In addition to PHA or IL-2, we have co-stimulated CD8+ T cells with PHA/IL-2 and a mixture of thymic peptides (TP) of molecular weights below 10 kD. For the activation, CD8+ T cells were purified from peripheral blood mononuclear cells of HIV-1- individuals and any resultant anti-viral activity was monitored using an HIV-1 neutralization assay. Using HIV-1 isolates highly resistant to chemokine inhibition we detected significantly higher levels of HIV-1 neutralizing activity in CD8+ T cell culture supernatants which had been co-activated with TP. When the TP-induced anti-viral activity was monitored, neutralization of both non-syncytia-inducing (NSI) and syncytia-inducing (SI) patient isolates was enhanced by 38% (NSI, PHA +/- TP), 66% (SI, PHA +/- TP), 28% (NSI, IL-2 +/- TP), and 57% (SI, IL-2 +/- TP) compared with the anti-viral activity present in supernatants from CD8+ T cell cultures stimulated only with PHA or IL-2. Peptide sequence analysis of purified TP showed that the TP mixture predominantly contains peptides with homology to human histone and collagen sequences. Our data demonstrate that CD8+ T cells are additionally activated by a mixture of TP. In this way, the production of HIV-1 neutralizing CD8 factors can be enhanced.