Sin Nombre Virus-Specific Immunoglobulin M and G Kinetics in Hantavirus Pulmonary Syndrome and the Role Played by Serologic Responses in Predicting Disease Outcome

Background. Sin Nombre virus (SNV) is the primary cause of hantavirus pulmonary syndrome (HPS) in the United States. Although other studies have demonstrated a possible association between neutralizing antibody titers and the severity of HPS, the exact nature of serologic responses and their association with outcomes have not been fully characterized. Methods. We examined immunoglobulin M (IgM) and immunoglobulin G (IgG) serologic responses in 94 clinical samples from 81 patients with confirmed HPS. We further compared a subset of 31 patients with fatal HPS and 20 surviving patients for whom samples were available within a week after the onset of HPS. Results. SNV-specific IgM antibodies displayed a trend suggesting an early peak, whereas IgG antibody values peaked later. Among individuals with samples from the first week after the onset of HPS, all surviving patients had SNV-specific IgG responses, compared with <50% of patients with fatal HPS, and the distribution of IgG responses was significantly higher in surviving patients. Conclusions. Production of SNV-specific IgM antibodies occurs early during the clinical course of HPS, whereas production of IgG antibodies may be more protracted. The presence and overall distribution of higher IgG antibody titers in surviving patients with HPS suggests that production of SNV-specific IgG may be a strong predictor of favorable outcomes.