July 11, 2014
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High levels of pre-existing norovirus antibodies predicts protection from infection

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High levels of pre-existing, type-specific norovirus serum immunoglobulin antibodies in children with gastroenteritis indicate protection from norovirus infection based on strain, according to study findings in the Journal of Infectious Diseases.

Maria Malm, PhD, of Tampere University Hospital in Tampere, Finland, and colleagues analyzed norovirus-specific immunoglobulin (IgG) antibody levels and blocking potential of acute serum among 666 children, aged less than 15 years, who presented to Tampere University Hospital with acute gastroenteritis.

Approximately 17% of children who presented with gastroenteritis tested positively for norovirus. The first positive cases of norovirus were detected in December 2009. An estimated 75% of those with norovirus were aged younger than 2 years; this age group accounted for 58% of those with gastroenteritis.

Of the 43 children with norovirus who provided serum samples, 62.8% had genotype-II-4 and 37.2% had other genotypes within the genotype-II group.

Overall, 55.6% of children aged younger than 1 year and 35.7% of children aged 1 to 2 years had low pre-existing serum endpoint antibodies against all tested norovirus genotypes. All children aged older than 2 years had high levels of norovirus-specific antibodies that protected against at least one norovirus genotype.

Children with genotype-II-4 New Orleans had significantly lower levels of pre-existing genotype-II-4 New Orleans-specific IgG compared with children who had other genotype-II genotypes. However, children with other genotypes had significantly higher pre-existing antibody titers of genotype-II-4 New Orleans.

Genotype-specific seroconversion corresponded with an increase in blocking antibody potential. The researchers also observed seroconversion to genotype-II-4-1999, but it was not related to an increase in specific blocking antibody titer.

“Data presented here indicate positive correlation between high pre-existing genotype-specific serum IgG titers and blockade of [virus-like particles] binding to [histo-blood group antigen] receptors to protection from infection, addressing the relevance of serum IgG responses in children. Our data support the prevailing understanding that induction of broad, high titer serum IgG levels with good blocking potential are necessary for protection from [norovirus] infections,” the researchers concluded.

Disclosure: The researchers have no relevant financial disclosures.