Thresholds were calculated while previously published (Pacyga et al

Thresholds were calculated while previously published (Pacyga et al.2020) by counting the mean of all results within the given group. == Results == == Some Polish individuals possess pre-pandemic immunity against SARS-CoV-2 nucleocapsid == The western blot analysis of the immunoreactivity of pre-pandemic human being individual sera against SARS-CoV-2 lysate, probed with secondary anti-IgA antibodies, revealed one protein band (Fig.1A). antibody, SR 3576 humoral immunity, epitope mapping, nucleocapsid Manuscript shows possible sources of cross-reactivity of pre-pandemic sera with SARS-CoV-2 proteins. == Intro == SARS-CoV-2 is definitely a member of the Betacoronavirus genus in the Coronaviridae family (Gorbalenya et al.2020). SR 3576 There are two seasonal coronaviruses in the same genus, namely HCoV-HKU1 and HCoV-OC43, and two more in theAlphacoronavirusgenus, HCoV-229E and HCoV-NL63 (Killerby et al.2018). Usually, infections with seasonal coronaviruses are frequent but mild, and the acquired immunity is definitely short-term. There are four main structural proteins that make up the SARS-CoV-2 virion: nucleocapsid (N), spike (S), membrane (M), and envelope (E) proteins (Chen et al.2020). N protein is used for viral genome packaging, offers conserved amino acid sequence among the Coronaviridae family, and is highly immunogenic and indicated in great amounts during the illness. Infected individuals are producing excessive amounts of N-specific antibodies. N-protein was already identified as efficient diagnostic tool for detection of SARS-CoV-2 illness and was suggested to be an interesting vaccine antigen (Bai et al.2021). There are already multiple yet often conflicting reports concerning pre-pandemic immunity against SARS-CoV-2 (Sealy and Hurwitz2021). Around 20% of individuals possess SARS-CoV-2 pre-pandemic cross-reactive serum antibodies, mostly against nucleocapsid. The high cross-reactivity of anti-SARS-CoV-2 antibodies along with other coronaviruses was shown in sub-Saharan Africa pre-pandemic samples (Tso et al.2021), in which the nucleocapsid was the dominant cross-recognized antigen. COVID-19 burden is much reduced sub-Saharan Africa than in the USA and coincides with higher levels of serological cross-reactivity of plasma samples from Tanzania and Zambia comparing to the ones from the USA (Tso et al.2021). Sagar et al. showed that individuals with a recent and documented history of common chilly HCoV illness have improved rates of survival when acquired SR 3576 COVID-19 (Sagar et al.2021). In contrast, other studies demonstrated that past illness with seasonal coronavirus does not provide a protecting immunity against SARS-CoV-2 (Anderson et al.2021, Gombar et al.2021). The explanation of these variations is important due to possible immunopathological effects of SARS-CoV-2. Another query is definitely whether past seasonal illness is the only source of SARS-CoV-2 cross-reactive antibodies. There are studies that indicate a link between influenza vaccination and reduced incidence or severity of COVID-19 (Conlon et al.2021, Tayar et al.2023). Whether this is related to the production of cross-reactive antibodies has not been clearly established, although there are common elements between the influenza and coronavirus, e.g. sialic acids (Matrosovich et al.2015). In this study, we evaluated the pre-pandemic sera in terms of their cross-reactivity with SARS-CoV-2 proteins and recognized nucleocapsid as one of the most recognized proteins. Next, we analysed the sera of acute and convalescent LAMC2 COVID-19 individuals sera in terms of anti-N antibodies. Finally, we performedin silicoand empirical epitope mapping of N-protein. The obtained results shed fresh light within the possible source of pre- and post-infection immunity and cross-reactivity, which should be taken into account when designing fresh N-protein centered vaccine antigens. == Methods == == Human being blood sera == Blood was from individuals with confirmed SARS-CoV-2 illness (moderate and severe instances) and admitted to the Infectious Diseases Admission Space of J. Gromkowski Hospital in Wrocaw between November 2020 and April 2021. Blood was drawn on admission to the hospital (acute COVID-19) and 3 weeks after the last symptoms of illness experienced ceased (COVID-19 convalescents). Serum from healthy volunteers was collected prior to the pandemic and was previously used in our studies (Razim et al.2018,2021). Individual or pooled sera were used for the experiments. For each patient, a written educated consent was acquired for the study, and the experiment itself was authorized by the bioethical committee no. KB-683/2020 (Bioethical Committee in the Medical University or college of Wrocaw). Experiments were conducted in accordance with the Helsinki Declaration, 1975. == Western blots == For sodium dodecyl-sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) , the 4%20% Mini-PROTEAN TGX Precast Protein Gels (Bio-Rad, USA) were used. 7 g of SARS-CoV-2 lysate (cat. NAT41605-500, The Native Antigen Organization, UK) was put on each lane. 2 l of Precision Plus Protein Dual Colour Requirements (Bio-Rad, USA) were used as protein mass marker..