Antibody responses in NCP-positive ICU patients
To understand the possible defect in ICU patients that have prolonged
NCP antigenemia (after 8 days of COVID-19), ICU patients were grouped
into those with NCP levels above and those below the cutoff, and the S1-
and NCP-specific antibody responses were analyzed. ICU patients without
detectable antigenemia had antibodies against S1 (Fig. 2A) and NCP (Fig.
2B) with ratios similar to non-ICU patients, suggesting normal antibody
responses. In contrast, ICU patients with antigenemia after day 8 of
COVID-19 had significantly lower S1-specific antibodies compared to ICU
patients without antigenemia. This difference was restricted to
S1-specific antibodies, while no difference was found for IgG against
NCP (Fig. 2B). Thus, the prolonged NCP antigenemia in COVID-19 patients
on ICU was associated with decreased antibody responses against S1, but
not NCP.