CCp5A Protein from Toxoplasma gondii as a Serological Marker of Oocyst-driven Infections in Humans and Domestic Animals

Abstract

Considering that the current immunoassays are not able to distinguish the infective forms that cause Toxoplasma gondii infection, the present study was carried out to evaluate the reactivity of two recombinant proteins (CCp5A and OWP1) from oocyst/sporozoite, in order to differentiate infections occurring by ingestion of oocysts or tissue cysts. The reactivity of the recombinant proteins was assessed against panels of serum samples from animals (chickens, pigs, and mice) that were naturally or experimentally infected by different infective stages of the parasite. Also, we tested sera from humans who have been infected by oocysts during a well-characterized toxoplasmosis outbreak, as well as sera from pregnant women tested IgM+/IgG+ for T. gondii, which source of infection was unknown. Only the sporozoite-specific CCp5A protein was able to differentiate the parasite stage that infected chickens, pigs and mice, with specific reactivity for oocyst-infected animals. Furthermore, the CCp5A showed preferential reactivity for recent infection by oocyst/sporozoite in pigs and mice. In humans, CCp5A showed higher reactivity with serum samples from the outbreak, compared with serum from pregnant women. Altogether, these findings demonstrate the usefulness of the CCp5A protein as a new tool to identify the parasite stage of T. gondii infection, allowing its application for diagnosis and epidemiological investigations in animals and humans. The identification of parasite infective stage can help to design effective strategies to minimize severe complications in immunocompromised people and, particularly, in pregnant women to prevent congenital infection.

Sixty Years (1957–2017) of Research on Toxoplasmosis in China—An Overview

“…Reference laboratories should be established to help local clinics and hospitals to get reliable test results for human samples. In addition to these, new diagnostic strategies, which can not only tell the infection status but also inform the source of infection (oocysts vs. tachyzoites/bradyzoites; Santana et al, 2015 ), may be needed for better risk factor association analysis.…”

Importance of serological cross-reactivity amongToxoplasma gondii, Hammondiaspp.,Neosporaspp.,Sarcocystisspp. andBesnoitia besnoiti

“…This study was the first to use a sporozoite protein, called T. gondii embryogenesis-related protein (TgERP) in a serologic test for T. gondii . In a recent study another sporozoite-derived protein called CCp5A was successfully used in an ELISA to identify oocyst-infected animals (Santana et al 2015); this test was able to identify antibodies in sera from humans, pigs, mice and chickens that were naturally or experimentally infected with T. gondii oocysts and discriminate between animals infected from ingestion of oocysts or by carnivorism. Further investigations are necessary for validation and to confirm whether the sporozoite proteins TgERP (Hill et al 2011) and CCp5A (Santana et al 2015) cross-react with sporozoite proteins derived from Hammondia spp.…”

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

“…Serological diagnosis pinpointing T. gondii cysts or oocysts as the mode of transmission by means of an ELISA using a recombinant protein, i.e. the sporozoite-specific embryogenesis-related protein (TgERP) [18], and more recently the CCp5A recombinant protein [19], has allowed differentiation between the two modes of infection.…”