Immunoglobulin A responses to Puumala hantavirus

Puumala hantavirus (PUUV) causes nephropathia epidemica (NE), a form of hae morrhagic fever with renal syndrome that occurs in northern and central Eur ope. The immunoglobulin A (IgA) response in NE patients was studied. The le vels of total serum IgA in acute-phase samples from NE patients were found to be significantly elevated when compared with the levels in healthy contr ols. ELISAs for detection of the IgA1 and IgA2 responses against each PUUV structural protein (N, G1 and G2) were developed and evaluated. Sequential sera from NE patients (acute, convalescent, 2-year) and 10-20 year NE-conva lescent sera were examined, Most patients developed detectable levels of Ig A1 against N and G2, while the G1 responses were low or undetectable. Seven of nine 10-20 year sera contained virus-specific IgA1, which may indicate the prolonged presence of viral antigens after the initial infection. PEPSC AN analysis revealed several IgA-reactive antigenic regions in the N protei n. Serum IgA and IgG was purified by affinity chromatography and examined b y a virus-neutralization assay. Three of five sera from acute-phase NE pati ents contained neutralizing IgA1, The diagnostic potential of the PUUV-spec ific IgA1 response was evaluated. The N and G2 assays showed specificities of 100% with sensitivities of 91 and 84%, respectively, compared with an Ig M mu-capture ELISA, Several NE patients, clinically diagnosed for acute PUU V infection, with borderline or undetectable levels of PUUV-specific IgM, w ere found to be highly positive for the presence of PUUV N-specific serum I gA1, proving the diagnostic value of IgA analysis as a complement to detect ion of IgM.