Impact of SARS-CoV-2 vaccination on systemic immune responses in people living with HIV.

Despite the development of vaccines, which protect healthy people from severe and life-threatening Covid-19, the immunological responses of people with secondary immunodeficiencies to these vaccines remain incompletely understood. Here, we investigated the humoral and cellular immune responses elicited by mRNA-based SARS-CoV-2 vaccines in a cohort of people living with HIV (PLWH) receiving anti-retroviral therapy. While antibody responses in PLWH increased progressively after each vaccination, they were significantly reduced compared to the HIV-negative control group. This was particularly noteworthy for the Delta and Omicron variants. In contrast, CD4+ Th cell responses exhibited a vaccination-dependent increase, which was comparable in both groups. Interestingly, CD4+ T cell activation negatively correlated with the CD4 to CD8 ratio, indicating that low CD4+ T cell numbers do not necessarily interfere with cellular immune responses. Our data demonstrate that despite the lower CD4+ T cell counts SARS-CoV-2 vaccination results in potent cellular immune responses in PLWH. However, the reduced humoral response also provides strong evidence to consider PLWH as vulnerable group and suggests subsequent vaccinations being required to enhance their protection against COVID-19.

A Bioassay for the Determination of Lipopolysaccharides and Lipoproteins.

The availability of convenient assays for the detection and quantification of pathogen-associated molecular patterns (PAMPs) is limited. In the case of lipopolysaccharide (LPS) the so-called LAL (limulus amebocyte lysate) test is available, an assay that is performed with the lysate of the blood of the horse shoe crab. Although a sensitive and convenient assay, it lacks specificity, since it is affected by other endotoxins like, for instance, fungal cell walls as well. Here, we describe a bioassay that can be used to detect and quantitate PAMPs in environmental samples. More specific we demonstrate the usage of TLR2 and TLR4/CD14/MD2 transfected Hek293 cells to quantitatively determine bacterial lipoproteins and LPS, respectively. We show the usefulness of these assays to measure LPS in tobacco before and after combustion.