AGE-STRATIFIED SEROPREVALENCE OF NEUTRALIZING ANTIBODIES TO ASTROVIRUS TYPE-1 TO TYPE-7 IN HUMANS IN THE NETHERLANDS

Astroviruses are a new family of positive-stranded RNA viruses that ca use gastroenteritis in a wide range of animals and in humans. Seven ty pes of astrovirus, tentatively considered serotypes, have been disting uished by enzyme-linked immunosorbent assays (ELISA) or immunoelectron microscopy, but it is unclear whether the serotype designation is use d properly. To test human sera for the presence of neutralizing antibo dies and to type field strains, neutralization tests (NT) using CaCo2 tissue-culture-adapted astrovirus strains 1 to 7 and the corresponding rabbit reference sera were developed. In rabbits, neutralizing antibo dies were predominantly serotype specific, with the exception of low-l evel cross-reactivity in astrovirus serotype 4 reference serum with as trovirus serotype 1 virus. Similarly, in humans, no evidence of cross- reactivity was found for the serotype combinations tested (all except the combination 1 and 7 and the combination 6 add 7). Typing by NT was concordant with typing by ELISA and genotyping, with one exception. T he seroprevalence rates of neutralizing antibodies in an age-stratifie d sample of the population in Utrecht Province (n = 242) were 91% for astrovirus serotype 1, 69% for astrovirus serotype 3, 56% for astrovir us serotype 4, 36% for astrovirus serotype 5, 31% for astrovirus serot ype 2, 16% for astrovirus serotype 6, and 10% for astrovirus serotype 7. Acquisition of antibodies was slower among persons seropositive for astrovirus serotype 5 than among those seropositive for astrovirus se rotypes 1 to 4, suggesting that the epidemiology of serotype 5 astrovi rus is different from that of astrovirus serotypes 1 to 4.