Immune parameters in hospitalized COVID-19 patients during SARS-CoV2 delta and omicron waves

Understanding immune mechanisms associated with COVID-19 severity remains important for interpreting clinical outcomes. We investigated virological and immunological profiles in 39-patients hospitalized with COVID-19 at InCor Hospital during the Delta and Omicron waves and included 28-non-hospitalized individuals with moderate COVID-19 as a comparator group for cytokine analyses. SARS-CoV-2 infection was confirmed by RT-PCR from nasopharyngeal swabs, and viral variants were identified by next-generation sequencing. RNAemia was assessed by RT-PCR and analyzed as a binary variable. Serum cytokines were quantified by cytometric bead array, while humoral responses were evaluated by anti-Spike RBD IgG levels using CLIA and a Wuhan-Hu-1-based pseudovirus neutralization assay. RNAemia was more frequent in ICU-admitted patients than in non-ICU patients, supporting an association with disease severity. Cytokine profiling showed increased IL-6, IL-8, TNF, IL-17 A and IL-10 levels in hospitalized patients compared with moderate COVID-19 individuals, but did not distinguish recovered from deceased patients. Neutralizing antibody titers measured against a Wuhan-Hu-1 spike pseudovirus were significantly higher in recovered individuals than decease patients, underscoring the relevance of antibody functionality. These data emphasize the relevance of viral dissemination and functional humoral immunity as potential biomarkers for COVID-19 progression and outcome, with RNAemia and neutralizing antibody levels showing a stronger exploratory association in this cohort.