Anti-SARS-CoV IgG response in relation to disease severity of severe acute respiratory syndrome.

BACKGROUND: The association between a robust or depressed antibody response and clinical severity of SARS remains unknown.

OBJECTIVES: To study seroconversion and the magnitude of IgG responses in a SARS cohort with different disease severities.

STUDY DESIGN AND METHOD: A retrospective analysis of all acute and convalescent-phase sera collected from a cohort of laboratory-confirmed SARS cases. Anti-SARS-CoV IgG antibody was detected using indirect immunofluorescence technique and quantified by two-fold serial dilutions. Characteristics of patients who seroconverted "early" (
RESULTS: A total of 325 laboratory-confirmed SARS cases were analyzed; of which 301 (92.6%) had anti-SARS-CoV IgG detected in their sera at the time of sampling. IgG was first detected on day 4 of illness; seroconversion occurred at a median of 16 days (range 4-35 days), and IgG peak levels were reached in the fourth week. Early seroconversion (
CONCLUSIONS: Severe SARS is associated with a more robust IgG response.