Seroprevalence of Aichi virus in a Spanish population from 2007 to 2008

Abstract

Viruses are among the most common causes of acute gastroenteritis. In recent years, new viruses causing outbreaks of acute gastroenteritis have been described. Among these, Aichi virus was identified in Japan in 1989. Aichi virus belongs to the Kobuvirus genus in the family Picornaviridae. This virus has been detected in outbreaks of gastroenteritis associated with oyster consumption and in pediatric stool samples, but little is known about its epidemiology or pathogenesis. In the present study, the prevalence of antibodies to Aichi virus in a Spanish population was determined between 2007 and 2008 by using an enzyme-linked immunosorbent assay (ELISA). As in previous studies, a high seroprevalence of antibodies to Aichi virus (70%) was observed, with levels differing according to age. We observed significant differences in titers of antibody to Aichi virus among different age groups, grouped by decades. We report high ELISA and neutralizing antibody titers, and both titers fitted a sigmoid curve significantly. However, this virus is seldom detected; therefore, further studies are needed to gain a better understanding of its importance as a pathogenic agent.

FIG. 1.

Aichi virus seroprevalence. Percentages of sera positive for antibodies against Aichi virus by age group in Valencia, Spain, between 2007 and 2008 are shown. Error bars indicate 95% confidence intervals.

FIG. 2.

Distribution of levels of antibodies to Aichi virus by age. Levels of IgG antibody against Aichi virus were quantified by calculating the PP for each sample. In the graph, the dots represent median values, and the error bars represent the 25th-to-75th-percentile intervals. The dotted line marks the cutoff level. Greek letters represent significant differences (by the Mann-Whitney U test with Bonferroni's correction for multiple comparisons) from the 2- to 4-year-old group (α), from the 5- to 9-year-old group (β), from the 10- to 14-year-old group (γ), and from the 15- to 19-year-old group (δ). The 0- to 2-year age group was not included in the statistical analysis due to the low number of samples.

FIG. 3.

Relationship between ELISA titers and seroneutralization titers. The ELISA titers and seroneutralization titers of 23 randomly selected serum samples were compared. The graphic representation of ELISA and neutralizing titers fits the sigmoid curve well. This relationship was assessed by analysis of variance (P < 0.0001; R² = 0.7046). Only 18 dots are shown, because several samples yielded the same values for ELISA and neutralizing titers.