IntroductionProtective immunity against pathogens relies on the production of high-affinity antibodies by long-lived plasma cells (PCs). Moreover, the ability to respond faster and with more potent antibodies to subsequent encounters with the same infectious agent depends on the generation of long-lived memory B cells. Both, high-affinity memory B cells and PCs differentiate from antigenspecific B cells that are recruited into the GC reaction during T cell-dependent immune responses (1). In GCs, B cells undergo clonal expansion, a process during which they accumulate mutations at high frequency within the Ig heavy and light chain variable (V) region genes. The highly dynamic nature of the GC reaction is characterized by repeated cycles of cell division, Ig somatic mutation, and strict selection based on the ability of B cells to capture and present antigen to T follicular helper cells (2). These processes occur within distinct areas of the GC reached by B cells through migratory paths regulated by chemokine gradients (1). The molecular determinants enabling cyclic reentry of B cells into the proliferating and mutating compartment of centroblasts, preventing terminal differentiation and the ensuing exit from the GC, remain poorly characterized.

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Background: Many publications have considered the exposure risk to COVID-19 of the general population and healthcare workers. However, no available papers have discussed the risk of exposure by family members of health care workers. Aims: The present study collected data on SARS-COV-2 positive family members (FM) of health care workers (HW) using serological rapid IgM/IgG tests (SRT), compared to positive HWs on SRT and serological quantitative IgG tests (SQT). Methods: The study was conducted from May 2 to 31, 2020. Thirty-eight HWs were tested by both SRT and SQT; 81 FMs were screened using SRT. Descriptive statistical analyses were used to summarize the data. Results: Of the 38 HWs, two (5,3%) showed an IgG line on SRT, confirmed by SQT. Thirty-two HWs decided on self-isolation from the family during the SARS-COV-2 spread. Out of 81 FMs, 26 (32,1%) were found IgG positive on SRT. Eleven (42%) of them had symptoms typical for COVID-19, during the study period. In two families, the HWs were the only negative cases. Conclusions: The general population's exposure to COVID-19 is less controlled than that of HWs. HWs experienced a lower infection rate than their families and did not represent a main transmission risk for relatives.

Background: Of many descriptive papers about healthcare workers’ (HW) COVID-19 infection, asymptomatic cases have not yet considered. Aims: The present study calculated the numbers of COVID-19 patients afferent to GI endoscopy and the number of positive HW using nasopharyngeal swabs (NS), serological rapid IgM/IgG tests (SRT) and serological quantitative IgG test (SQT).Methods: The study was conducted from 2ndto 30thApril 2020. All the recommended national and international indications on infection control measures were followed. Out of 1227 patients accepted, 1009 were included in the study. 38 HW were tested by NS, SRT and SQT. Descriptive statistical analyses were used to summarize the data.Results: 17 patients were diagnosed COVID-19 positive at NS. 9 patients were known positive at the time of the endoscopy and 8 were diagnosed COVID-19 positive after the procedure. Of the 38 HW, 2 were positive both to NS and SRT with IgM/IgG lines; 7 showed IgG line only at SRT, confirmed by SQT with negative NS. Other 7 HW showed not well-defined line of IgG at SRT, confirmed negative by SQT. The two cases positive to NS and IgM/IgG SRT were asymptomatic. The crude contagion’s rate (R0)was 0.41 and 1.7% of COVID-19 patients caused 19% of positive cases in HW.Conclusions: Not previously diagnosed COVID-19 patients expose HW to additional and incalculable risk of contamination. Association between different tests reduced the variability related to possible confounding factors and increases the accuracy. Since most cases in HW seem to go asymptomatic, large-scale tests using both NS and SRT for both HW and patients should be recommended to minimize the risk of in-hospital infection’s relapses.

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The outbreak of the SARS-CoV-2 in early 2020 found health authorities worldwide unprepared to control the pandemic. The adoption of accurate, rapid and inexpensive methods to identify infected subjects in the general population is of paramount relevance for the control of the disease. We evaluated one of the available serological tests, the Prima Lab Covid-19 IgG/IgM Rapid Tests, on 739 volunteers. We first assessed the test's reproducibility by administering it twice on the same day on 104 subjects obtaining and overall score of 93 percent. Since the intensity of the color in the test line regions varies depending on the concentration of Covid-19 antibodies in each sample and that the determination of the positivity depends strictly on the subjective assessment by the reader, after excluding the subjects whose color intensity was too tenuous to be deemed unquestionably positive by the reader the reproducibility increased to 96%. The test would not perform properly for 6 subjects for a very limited overall technical failure of 0.83%. For 138 subjects information was available regarding a previous Real Time PCR nasopharyngeal swab test performed elsewhere. The correspondence of positive results between the two tests was 90.58% (125/138). In spite of some limitation owing especially to the choice of a self selected population sample, we conclude that Prima Lab Covid-19 IgG/IgM Rapid Test represents a low-cost, easily applicable and reproducible tool in detecting SARS-Cov-2 diffusion in the general population.