Quantitation of norovirus-specific IgG before and after infection in immunocompromised patients.

Noroviruses (NoV) cause the majority of non-bacterial gastroenteritis cases worldwide, with genotype II.4 being the most common. The aim of our study was to quantitate norovirus-specific IgG in immunocompromised patients before and after laboratory-confirmed norovirus infection. A quantitative ELISA was developed by coating ELISA plates with recombinantly expressed P domain of GII.1 capsid protein. After testing mouse sera drawn before and after immunization with GII.1- and GII.4 P domain, sera from GII.1- and GII.4 infected patients were tested. The assay reliably detected preexisting NoV-specific IgG antibodies. Sera drawn after infection showed increased antibody concentrations. Antibodies elicited by GII.1- and GII.4 infections could be detected with coated GII.1 capsid protein. IgG levels remained constant during the first week and then increased in the second week after laboratory diagnosis. The results show that immunocompromised patients elicited IgG responses to NoV infections that could be reliably detected with our quantitative ELISA.