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Title: Salivary IgA against sporozoite-specific embryogenesis-related protein (TgERP) in the study of horizontally transmitted toxoplasmosis via T. gondii oocysts in endemic settings

item MANGIAVACCHI, B - Universidade Estadual Do Norte Fluminense
item VIEIRA, F - Universidade Estadual Do Norte Fluminense
item BAHIA OLIVEIRA, L - Universidade Federal Do Rio De Janeiro
item Hill, Dolores

Submitted to: Epidemiology and Infection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2016
Publication Date: 5/20/2016
Citation: Mangiavacchi, B., Vieira, F., Bahia Oliveira, L.M., Hill, D.E. 2016. Salivary IgA against sporozoite-specific embryogenesis-related protein (TgERP) in the study of horizontally transmitted toxoplasmosis via T. gondii oocysts in endemic settings. Epidemiology and Infection. 12:1-10.

Interpretive Summary: Toxoplasmosis infection caused by the protozoan Toxoplasma gondii is widely distributed in humans in many parts of the world. In Brazil, its prevalence ranks among the highest in the world. A broad range of potential routes of T. gondii transmission has been developed by the parasite in the course of its evolution. Congenital toxoplasmosis in humans results from transmission of the parasite to the fetus during pregnancy, and constitutes a very dangerous mode of infection, causing stillbirth or a variety of disease syndromes, from chronic infection without apparent clinical symptoms, to blindness and mental retardation in children. Humans also become infected through ingestion of tissue cysts in undercooked or uncooked meat, or by ingesting food or water contaminated with sporulated oocysts (containing the infective sporozoite forms) from infected cat feces. The relative epidemiologic importance of different modes of infection with respect to horizontal transmission of T. gondii, namely if by ingestion of tissue cysts, or by ingesting food or water contaminated with sporulated oocysts, remains unknown. The ability to discriminate between the 2 modes of infection depends, besides other factors, on serological tests capable of discriminating both modes of infection. In epidemiological terms, using conventional serology, which recognizes antigens from tachyzoites, cannot be used to discriminate predominant routes (oocysts or tissue cysts) of transmission. Serologic diagnosis pinpointing T. gondii cysts or oocysts as the mode of transmission by means of an ELISA test using a recombinant protein, the sporozoite specific protein, TgERP, and more recently CCp5A recombinant protein has made possible the differentiation between the 2 modes of infection. We investigated T. gondii prevalence using conventional and TgERP ELISAs and found that salivary IgA against TgERP should be considered a biomarker of value to study horizontal Toxoplasma gondii infection transmitted by oocysts.

Technical Abstract: The prevalence of toxoplasmosis was investigated in endemic settings in Brazil, and calculated by measuring antibodies in two ELISA systems: 1) IgG and IgM from sera tested by commercial conventional ELISA, and 2) IgA, from saliva, and IgG from sera samples tested against a sporozoite-specific protein (TgERP) to pinpoint parasite transmission via oocysts. Individuals grouped by age and prevalence estimates in the TgERP versus the conventional ELISA varied among age groups. However, in subjects 15 to 21 years of age, similar values for T gondii prevalence was observed by conventional (69%) and anti TgERP IgA ELISA using two cutoff criteria (66,6%) and (66,7%). Anti-TgERP IgA from saliva for this age group presented the highest specificity (93,33%), sensitivity (93,94%), and likelihood (14.09) compared to other age groups. These data suggest that in endemic settings, horizontally transmitted toxoplasmosis can be characterized and better understood by measuring salivary IgA against TgERP in younger age groups or where transmission rates are high, which in the present study corresponded to 15 to 21 years. We propose that IgA anti-TgERP may be a good biomarker to study prevalence and incidence of waterborne toxoplasmosis in prospective cohorts and case-control studies.