ACCURATE SERODIAGNOSIS OF B19 PARVOVIRUS INFECTIONS BY MEASUREMENT OFIGG AVIDITY

In an attempt to improve diagnosis of illnesses caused by parvovirus B 19 and to discriminate primary from secondary infections, a protein-de naturing assay for avidity of parvovirus-specific IgG antibodies was d eveloped. The assay used three types of purified recombinant antigens: a fusion protein containing the unique portion of the structural prot ein VP1, entire capsids made up of the major structural protein VP2 al one, or VP2 plus VP1. The avidity assays were evaluated by testing seq uential acute-phase serum samples from 61 well-characterized patients (34 were followed greater than or equal to 6 months), sera from 38 con trols with evidence of past infection, and sera from 388 seropositive patients studied for evidence of B19 infection during an epidemic. Par vovirus capsids consisting of VP2 alone yielded unusual IgG avidity an d IgG antibody responses. Three different IgG avidity assays based on VP1 protein antigens were highly sensitive and specific and were consi dered suitable for identification of recent primary infections by huma n parvovirus B19.