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SARS-CoV-2 T cell responses are associated with COVID-19 recovery, and Class I- and Class II-restricted epitopes have been identified in the spike (S), nucleocapsid (N) and membrane (M) proteins and others. This prospective COVID-19 Health Action Response for Marines (CHARM) study enabled assessment of T cell responses in symptomatic and asymptomatic SARS-CoV-2 infected participants. At enrollment all participants were negative by qPCR; follow-up occurred biweekly and then bimonthly for the next 6 weeks. Study participants who tested positive by qPCR SARS-CoV-2 test were asked to enroll in an immune response sub-study. FluoroSpot interferon-gamma (IFN-{gamma}) and IL2 responses following qPCR-confirmed infection at enrollment (day 0), day 7 and 14 and more than 28 days later were measured using pools of 17mer peptides covering S, N, and M proteins, or CD4+CD8 peptide pools containing predicted epitopes from multiple SARS-CoV-2 antigens. Among 124 asymptomatic and 105 symptomatic participants, SARS-CoV-2 infection generated IFN-{gamma} responses to the S, N and M proteins that persisted longer in asymptomatic cases. IFN-{gamma} responses were significantly (p=0.001) more frequent to the N pool (51.4%) than the M pool (18.9%) among asymptomatic subjects; however, the difference was not statistically significant (p=0.06) for symptomatic subjects (N pool: 44.4%; M pool: 25.9%). In asymptomatic participants IFN-{gamma} responders to the CD4+CD8 pool responded more frequently to the S pool (55.6%) and N pool (57.1%), than the M pool (7.1%), but symptomatic participants, IFN-{gamma} responses were more frequent to the S pool (75.0%) than N pool (33.3%) and M pool (33.3%). The frequencies of IFN-{gamma} responses to the S and N+M pools peaked 7 days after the positive qPCR test among asymptomatic (S pool: 22.2%; N+M pool: 28.7%) and symptomatic (S pool: 15.3%; N+M pool 21.9%) participants and dropped by >28 days. Magnitudes of post-infection IFN-{gamma} and IL2 responses to the N+M pool were significantly correlated with IFN-{gamma} and IL2 responses to the N and M pools. These data further support the central role of Th1-biased cell mediated immunity IFN-{gamma} and IL2 responses, particularly to the N protein, in controlling COVID-19 symptoms, and justify T cell-based COVID-19 vaccines that include the N and S proteins.
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BackgroundThe risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) subsequent infection among seropositive young adults was studied prospectively. MethodsThe study population comprised 3,249 predominantly male, 18-20-year-old Marine recruits. Upon arrival at a Marine-supervised two-week quarantine, participants were assessed for baseline SARS-CoV-2 IgG seropositivity, defined as a 1:150 dilution or greater on receptor binding domain and full-length spike protein enzyme-linked immunosorbent (ELISA) assays. SARS-CoV-2 infection was assessed by PCR at initiation, middle and end of the quarantine. After appropriate exclusions, including participants with a positive PCR during quarantine, we performed three biweekly PCR tests in both seropositive and in seronegative groups once recruits left quarantine and entered basic training and baseline neutralizing antibody titers on all subsequently infected seropositive and selected seropositive uninfected participants. FindingsAmong 189 seropositive participants, 19 (10.1%) had at least one positive PCR test for SARS-CoV-2 during the six-week follow-up (1.1 cases per person-year). In contrast, 1,079 (48.0%) of the 2,247 seronegative participants tested positive (6.2 cases per person-year). The incidence rate ratio was 0.18 (95% CI 0.11-0.28, p<0.00001). Among seropositive recruits, infection was associated with lower baseline full-length spike protein IgG titers (p<0.0001). Compared with seronegative recruits, seropositive recruits had about 10-fold lower viral loads (ORF1ab gene, p<0.005), and trended towards shorter duration of PCR positivity (p=0.18) and more frequent asymptomatic infections (p=0.13). Among seropositive participants, baseline neutralizing titers were detected in 45 of 54 (83.3%) uninfected and in 6 of 19 (31.6%) infected participants during the 6 weeks of observation (ID50 difference p<.0001). InterpretationSeropositive young adults had about one-fifth the risk of subsequent infection compared with seronegative individuals. Although antibodies induced by initial infection are largely protective, they do not guarantee effective SARS-CoV-2 neutralization activity or immunity against subsequent infection. These findings may be relevant for optimization of mass vaccination strategies. FundingDefense Health Agency and Defense Advanced Research Projects Agency
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OBJECTIVE:To study the feasibility of bacterial endotoxin test for hepatocyte growth-promoting factors injection as a substitution for pyrogen test METHODS:According to China Pharmacopoeia(second part,2000),interference test was carried on endotoxin detection of hepatocyte growth-promoting factors injection with limulus lysate test agents produced by two different factories RESULTS:There was no interference with the reaction between bacterial endotoxin and limulus lysate test agent in hepatocyte growth-promoting factors injection in 10-fold dilution CONCLUSION:It is feasible to use the gelatine method in bacterial endotoxin test
