Serotyping, host genes and cytokines response in human ocular toxoplasmosis.

In human ocular toxoplasmosis, serotype is related with greater severity. We analyzed Toxoplasma GRA6 serotype in 23 patients with ocular toxoplasmosis (13 confirmed, two co-infections- and eight unconfirmed cases) and 20 individuals chronically infected with Toxoplasma but without ocular involvement. In patients with ocular toxoplasmosis, we also studied host gene polymorphisms related to immune response (IL-1ß; IL-1α; IL-10; IFN-γ; TNF-α, IL-12), IL-17R, TLR-9, and P2RX7. Additionally, eight patients were studied for the production of TNFα, IL1-ß, IFN-γ and IL-10 by their peripheral leukocytes after ex vivo stimulation with soluble Toxoplasma antigens. There were no differences in the distribution of serotypes (GRA6-I versus GRA6 non-I) between infected individuals with- or without ocular involvement. Seropositivity for GRA6-I was associated with higher number of retinal lesions and higher levels of IL-1ß. Two polymorphisms were associated with specific clinical manifestations of ocular toxoplasmosis: IL-10 -819 C/T with bilateral lesions and IL-12 + 169,774 A/C with synechia. Higher levels of IL-10 were found in patients with the allele G/G at the polymorphic region IL-10 -1082. People with a GRA6 I serotype and possessing the allele G/G at the polymorphic region TNFα-857 suffered from an increased number of retinal lesions. We found a positive association between host cytokine genes polymorphisms and GRA6 serotypes correlated with specific clinical manifestations and immune response in ocular toxoplasmosis.

Serotyping of Toxoplasma gondii: striking homogeneous pattern between symptomatic and asymptomatic infections within Europe and South America.

Field isolates of Toxoplasma gondii in Europe and North America have been grouped into three clonal lineages that display different virulence in mice. Whether the genetic structure of the parasite is related to clinical expression in humans has not yet been demonstrated. We developed an enzyme-linked immunosorbent assay which uses lineage-specific, polymorphic polypeptides derived from the dense granule antigens, GRA5 and GRA6. Our goal was to compare serotypical patterns observed in asymptomatic versus symptomatic (ocular disease and severe infection in human immunodeficiency virus (HIV)-positive patients) infections among patients from Europe and South America. Independent of the clinical presentation of the disease, serotypes differed according to geographical origin, with a homogeneous distribution of serotype II in Europe and of serotypes I and III in South America. We conclude that GRA5-GRA6 serotyping is an interesting tool to study serotype prevalence in populations but it is not an accurate marker of pathogenicity of Toxoplasma infection in humans.

Serotyping of Toxoplasma gondii in chronically infected pregnant women: predominance of type II in Europe and types I and III in Colombia (South America).

Isolates of Toxoplasma gondii, which is responsible for a wide range of clinical manifestations are grouped into three clonal lineages of different virulence in mice. However, it is not clear whether this genotypic pattern is associated with the clinical profile of the disease in humans nor is the geographical distribution of the genotypes known. This is mainly due to difficulties in obtaining parasitic DNA from patients. The available data are therefore limited and originate from acute or congenital infections or from animals. A non-invasive assay is needed to address issues of strain type, geographical distribution and severity of clinical toxoplasmosis. To serotype T. gondii strains, we have developed an enzyme-linked immunosorbent assay (ELISA) that uses polymorphic polypeptides specific to the three clonal lineages and derived from two dense granule antigens, GRA5 and GRA6. Two hundred and fifty-two sera from chronically infected pregnant women from three different European countries and Colombia were investigated. The analysis of genotype-specific antibody response showed a homogeneous type II distribution in the European samples compared with types I and III but no type II in the Colombian population. Our data concord with those obtained from the genotyping of other isolates from Europe and South America. We demonstrated that, despite some limitation due to antigen and/or antibody specificity, serotyping is a promising assay to investigate the relationship between type of strain and severity of the disease.