Comparison of serological assays to titrate Hantaan and Seoul hantavirus-specific antibodies

BACKGROUND: Hantaan and Seoul viruses, in the Hantavirus genus, are known to cause hemorrhagic fever with renal syndrome (HFRS). The plaque reduction neutralization test (PRNT), as conventional neutralization test for hantaviruses, is laborious and time-consuming. Alternatives to PRNT for hantaviruses are required. METHODS: In this study, the methods for Hantaan and Seoul viruses serological typing including microneutralization test (MNT), pseudoparticle neutralization test (PPNT) and immunofluorescence assay based on viral glycoproteins (IFA-GP) were developed and compared with PRNT using a panel of 74 sera including 44 convalescent sera of laboratory confirmed HFRS patients and 30 patients sera of non-hantavirus infection. Antibody titres and serotyping obtained with different methods above were analyzed by paired-t, linear correlation, McNemar χ(2) and Kappa agreement tests. RESULTS: Antibody titres obtained with MNT(50), PPNT(50) and IFA-GP were significantly correlated with that obtained with PRNT(50) (p < 0.001). GMT determined by PPNT(50) was statistically higher than that determined by PRNT(50) (p < 0.001), while GMT determined by MNT(50) and IFA-GP were equal with (p > 0.05) and less than (p < 0.001) that obtained with PRNT(50) respectively. Serotyping obtained with MNT(50) and PRNT(50), PPNT(50) and PRNT(50) were highly consistent (p < 0.001), whereas that obtained with IFA-GP and PRNT(50) were moderately consistent (p < 0.001). There were no significant differences for serotyping between PRNT(50) and MNT(50), as well as PRNT(50) and PPNT(50) (p > 0.05). IFA-GP was less sensitive than PRNT(50) and MNT(50) for serotyping of hantaviruses infection (p < 0.05). However, for 79.5% (35/44) samples, serotyping determined by IFA-GP and PRNT(50) were consistent. CONCLUSIONS: MNT(50) and PPNT(50) both can be used as simple and rapid alternatives to PRNT(50), and MNT(50) is more specific while PPNT(50) is more sensitive than other assays for neutralizing antibody determination. So far, this work has been the most comprehensive comparison of alternatives to PRNT.