Background: Viral and host immune kinetics during acute COVID-19 and after remission of acute symptoms need better characterization. Methods: SARS-CoV-2 RNA, anti-SARS-CoV-2 IgA, IgM, and IgG antibodies, and pro-inflammatory cytokines were measured in sequential samples among hospitalized COVID-19 patients during acute infection and 6 months following diagnosis. Results: 24 laboratory-confirmed COVID-19 patients with mild/moderate and severe COVID-19 were included. Most were males 83%, median age of 61 years. 21% were admitted to the ICU and 8 of them (33.3%) met criteria for severe COVID-19 disease. A delay in SARS-CoV-2 levels decline during the first 6 days of follow-up and viral load persistence until month 3 were related with severe COVID-19, but not viral load levels at the diagnosis. Higher levels of anti-SARS-CoV-2 IgA, IgM, IgG and the cytokines IL-6, IL-8 and MIP-1β at the diagnosis time were related with severe COVID-19 outcome. Higher levels of MIP-1β, IL-1β, MIP-1α and IFN-γ were observed at month 1-3 during mild/moderate disease compared to severe COVID-19. IgG persisted at low levels after 6 months of diagnosis. Conclusions: Higher concentrations of IgA, IgM, and IgG, and IL-6, IL-8 and MIP-1β are identified as early predictors of COVID-19 severity, but not SARS-CoV-2 RNA levels at diagnosis.

This work was supported by Plan Estatal de I+D+I 2013-2016 and 2017-2020 and cofinanced by Instituto de Salud Carlos III (ISCIII) - Subdirección General de Evaluación y Fomento de la investigación del Fondo Europeo de Desarrollo Regional (FEDER), Fondo COVID19 of Instituto de Salud Carlos III (COV20/00698), RETICS, Red de Investigación en SIDA [RD16/0025/0026]; and Fundación Biomédica Galicia Sur. E.R-M. was supported by Spanish Research Council (CSIC) and by the research grant CV20-85418 from the Consejería de Transformación Económica, Industria, Conocimiento y Universidades (Junta de Andalucía). A.G-V was supported by the Instituto de Salud Carlos III, cofinanced by the European Development Regional Fund (“A way to achieve Europe”), Subprograma Miguel Servet (CP19/00159). E.M.M. was supported by the Instituto de Salud Carlos III, cofinanced by the European Development Regional Fund (“A way to achieve Europe”), Subprogram PFIS (FI19/00304). C.K was supported by Fondo COVID19 of Instituto de Salud Carlos III (COV20/00823).

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