Neutralizing antibody response variation against dengue 3 strains

To evaluate the neutralizing antibody activity of a human sera panel against seven strains of the homotypic virus. Sera were collected from DENV-3 immune individuals. Two DENV-3 genotypes and strains isolated at different time-points during the 2000 and 2001-2002 Havana epidemics were included. A panel of 20 late convalescent sera collected 16-18 months after acute illness from DF and DHF patients are studied. These individuals were infected during the 2001-2002 Havana DENV-3 epidemic. All but four sera collected from DF cases had a secondary DENV-1/DENV-3 infection. Sera neutralizing antibody titer against the seven DENV-3 strains were determined by plaque reduction neutralization technique. Sera samples were tested simultaneously. Studied sera showed higher levels of neutralizing antibodies to DENV-3 strains of genotype III compared to genotype V. Interesting, higher levels of neutralizing antibodies were detected to DENV-3 strain isolated at the end of the epidemic 2001-2002. An increased tendency of GMT of neutralizing antibodies according to epidemic evolution was observed for the 2001-2002 outbreak. In general, antibody levels in sera collected from DF cases were higher. Differences in the neutralization capacity of immune DENV-3 sera tested against two homologous genotypes including strains of the same genotype are demonstrated. Observed results suggest that virus changed in the course of the epidemic. The implications of this finding in terms of dengue pathogenesis and vaccine development need to be considered.