Inactivated whole virion vaccine protects K18-hACE2 Tg mice against the Omicron SARS-CoV-2 variant via cross-reactive T cells and nonneutralizing antibody responses.

COVID-19 is a systemic inflammatory disease initiated by SARS-CoV-2 virus infection. Multiple vaccines against the Wuhan variant of SARS-CoV-2 have been developed including a whole virion beta-propiolactone-inactivated vaccine based on the B.1.1 strain (CoviVac). Since most of the population has been vaccinated by targeting the original or early variants of SARS-CoV-2, the emergence of novel mutant variants raises concern over possible evasion of vaccine-induced immune responses. Here, we report on the mechanism of protection by CoviVac, a whole virion-based vaccine, against the Omicron variant. CoviVac-immunized K18-hACE2 Tg mice were protected against both prototype B.1.1 and BA.1-like (Omicron) variants. Subsequently, vaccinated K18-hACE2 Tg mice rapidly cleared the infection via cross-reactive T-cell responses and cross-reactive, non-neutralizing antibodies recognizing the Omicron variant Spike protein. Thus, our data indicate that efficient protection from SARS-CoV-2 variants can be achieved by the orchestrated action of cross-reactive T cells and non-neutralizing antibodies.

Reverse Genetics Applied to Immunobiology of Tumor Necrosis Factor, a Multifunctional Cytokine.

Tumor necrosis factor (TNF) is one of many cytokines - protein molecules responsible for communication between the cells of immune system. TNF was discovered and given its grand name because of its striking antitumor effects in experimental systems, but its main physiological functions in the context of whole organism turned out to be completely unrelated to protection against tumors. This short review discusses "man-made" mouse models generated by early genome-editing technologies, which enabled us to establish true functions of TNF in health and certain diseases as well as to unravel potential strategies for improving therapy of TNF-dependent diseases.

SARS-CoV-2 Binding and Neutralization Properties of Peptides Derived from N-Terminus of Human ACE2.

The binding properties of synthetic and recombinant peptides derived from N-terminal part of ACE2, the main receptor for SARS-CoV-2, were evaluated. Additionally, the ability of these peptides to prevent virus entry in vitro was addressed using both pseudovirus particles decorated with the S protein, as well as through infection of Vero cells with live SARS-CoV-2 virus. Surprisingly, in spite of effective binding to S protein, all linear peptides of various lengths failed to neutralize the viral infection in vitro. However, the P1st peptide that was chemically "stapled" in order to stabilize its alpha-helical structure was able to interfere with virus entry into ACE2-expressing cells. Interestingly, this peptide also neutralized pseudovirus particles decorated with S protein derived from the Omicron BA.1 virus, in spite of variations in key amino acid residues contacting ACE2.

Will Peptides Help to Stop COVID-19?

Peptides are widely used for the diagnostics, prevention, and therapy of certain human diseases. How useful can they be for the disease caused by the SARS-CoV-2 coronavirus? In this review, we discuss the possibility of using synthetic and recombinant peptides and polypeptides for prevention of COVID-19 via blocking the interaction between the virus and its main receptor ACE2, as well as components of antiviral vaccines, in particular, against new emerging virus variants.

SlyD-deficient Escherichia coli strains: A highway to contaminant-free protein extraction.

Binding of native bacterial protein SlyD to metal affinity matrices remains a major problem in affinity purification of His-tagged recombinant proteins from Escherichia coli cells. In this study, four novel E. coli strains that lack the expression of SlyD/SlyX, were engineered using λ-red mediated chromosomal deletion. The resultant mutant E. coli strains allow us to obtain SlyD-free proteins immediately after metal affinity chromatography, and eliminate additional purification processes. As a model protein, bispecific antibodies composed of anti-F4/80 VHH module and anti-TNF VHH module (MYSTI-2) were used. Using this protein we have shown that the SlyD/SlyX-deficient E. coli strains allow us to obtain a fully functional protein.

Making anti-cytokine therapy more selective: Studies in mice.

Cytokines are involved in a wide range of functions shaping the normal immune response, yet inflammatory changes in the immune system due to dysregulated cytokine signaling may lead to the induction of autoimmunity. Cytokine inhibitors have revolutionized the treatment of many autoimmune diseases in recent years. Systemic cytokine ablation, however, is often associated with the development of adverse side effects and some patients simply do not respond to therapy. TNF, IL-1 and IL-6 are the best characterized proinflammatory cytokines considered as the main therapeutic targets for the treatment of several autoimmune and inflammatory diseases. But can anti-cytokine therapy become more selective and thus more efficient? This mini-review discusses several recently emerging paradigms and summarizes current experimental attempts to validate them in mouse studies.

Phenotypic Changes in T and NK Cells Induced by Sputnik V Vaccination.

A highly effective humoral immune response induced by the Sputnik V vaccine was demonstrated in independent studies, as well as in large-scale post-vaccination follow-up studies. However, the shifts in the cell-mediated immunity induced by Sputnik V vaccination are still under investigation. This study was aimed at estimating the impact of Sputnik V on activating and inhibitory receptors, activation and proliferative senescence markers in NK and T lymphocytes. The effects of Sputnik V were evaluated by the comparison of PBMC samples prior to vaccination, and then three days and three weeks following the second (boost) dose. The prime-boost format of Sputnik V vaccination induced a contraction in the T cell fraction of senescent CD57+ cells and a decrease in HLA-DR-expressing T cells. The proportion of NKG2A+ T cells was down-regulated after vaccination, whereas the PD-1 level was not affected significantly. A temporal increase in activation levels of NK cells and NKT-like cells was recorded, dependent on whether the individuals had COVID-19 prior to vaccination. A short-term elevation of the activating NKG2D and CD16 was observed in NK cells. Overall, the findings of the study are in favor of the Sputnik V vaccine not provoking a dramatic phenotypic rearrangement in T and NK cells, although it induces their slight temporal non-specific activation.

Induced antigen-binding polyreactivity in human serum IgA.

Previous studies have shown that polyreactive antibodies play an important role in the frontline defense against the dissemination of pathogens in the pre-immune host. Interestingly, antigen-binding polyreactivity can not only be inherent, but also acquired post-translationally. The ability of individual monoclonal IgG and IgE antibodies to acquire polyreactivity following contact with various agents that destabilize protein structure (urea, low pH) or have a pro-oxidative potential (heme, ferrous ions) has been studied in detail. However, to the best of our knowledge this property of human IgA has previously been described only cursorily. In the present study pooled human serum IgA and two human monoclonal IgA antibodies were exposed to buffers with acidic pH, to free heme or to ferrous ions, and the antigen-binding behavior of the native and modified IgA to viral and bacterial antigens were compared using immunoblot and ELISA. We observed a dose-dependent increase in reactivity to several bacterial extracts and to pure viral antigens. This newly described property of IgA may have therapeutic potential as has already been shown for pooled IgG with induced polyreactivity.

Distinguishing acute from chronic hepatitis C virus (HCV) infection based on antibody reactivities to specific HCV structural and nonstructural proteins.

Currently available serological assays for detection of antibodies to hepatitis C virus (HCV) cannot reliably discriminate acute from chronic HCV infection. We developed a multiplexed, flow-cytometric microsphere immunoassay to measure anti-HCV-IgG reactivities to the core, NS3, NS4, and NS5 HCV recombinant proteins and applied it to 99 serum samples from 24 anti-HCV seroconverters and 141 anti-HCV-IgG and HCV RNA-positive plasma specimens from chronically infected people. Differences in the geometric means or means of signal/cutoff ratios between the two sample sets were statistically significant for all the antigens tested. A multivariate logistic regression model correctly classified the samples in two groups, with a cross-validation accuracy of 90.8% for the acute group and 97.2% for the chronic group. The immunoassay described has the potential to distinguish acute from chronic HCV infection.

The structure of myeloid cell-specific TNF inhibitors affects their biological properties.

Spatial organization and conformational changes of antibodies may significantly affect their biological functions. We assessed the effect of mutual organization of the two VH H domains within bispecific antibodies recognizing human TNF and the surface molecules of murine myeloid cells (F4/80 or CD11b) on TNF retention and inhibition. TNF-neutralizing properties in vitro and in vivo of MYSTI-2 and MYSTI-3 antibodies were compared with new variants with interchanged VH H domains and different linker sequences. The most effective structure of MYSTI-2 and MYSTI-3 proteins required the Ser/Gly-containing 'superflexible' linker. The orientation of the modules was crucial for the activity of the proteins, but not for MYSTI-3 with the Pro/Gln-containing 'semi-rigid' linker. Our results may contribute toward the development of more effective drug prototypes.