Marcadores antigênicos das fases recente, de transição e crônica da toxoplasmose humana: determinação da avidez de anticorpos IgG por immunoblotting

Abstract

We proposed to characterize antigenic markers recognized by human serum samples from patients presenting serologícal profiles I, || and III of Toxoplasma infection, by the determination of IgG antibody avidity, using a modified immunoblotting technique (avidity immunobíotting). This method includes the dissociation of the antigen-antibody interaction with 6M or 8M urea Solutions. Human serum samples from 20 patients presenting recent infection (profile I), 45 patients presenting toxoplasmosis transient phases (profile II) and 60 patients with chronic infection (profile III) were analyzed. Good antigenic markers were considered for those antigenic bands recognized by low avidity IgG and sítuaíed in the quadrant IV of immunoplot. lí was observed that antigenic bands p16, p32, p38, p43, p60 and p97 were more frequently recognized by low avidity IgG in recent infection and by high avidity IgG in chronic toxoplasmosis. From these antigenic bands, p38 can be characterized as an optimal antigenic marker of low avidity for recent form o f toxoplasmosis, due to significantly high decrease of their frequency (from 80% to 0%), after treatment with 6M urea solution. The bands p23, p54 and p60 were considered as good antigenic markers for the serologícal group of profile II. In addiíion, p60 also was characterized as antigenic marker of the toxoplasmosis chronic phases, because it was recognized profiles I and II. The p30 antigen was noí considered as a good marker to distinguish different phases of infection, since corresponding IgG antibodies were determined as high-avidity in all phases of the infection. Thus the avidity immunoblotting assay demonstrated to be a useful and adequate íool to determine antigenic markers of recent, transient and chronic phases of T. gond//infection.