Figure 2.

Serotypes associated with German OT uveitis patients. A and B, Toxoplasma dye-test-negative serum samples (n = 50) were tested using a panel of 5 strain-specific peptides to determine the specificity and empiric threshold values for negative serum samples in the serotyping assay. Peptide names were abbreviated as follows: “6” denoting peptides from GRA6; “7” from GRA7; “I/III” or “II” indicating the archetypal strain from which the peptide allele was derived; and “d” indicating a truncated diagnostic peptide. Reactivity at SAG1 indicates the presence of anti-Toxoplasma antibodies. Type I/III strain infections produce allele-specific antibodies that react with 1 or both of the 6-I/III and d6-I/III peptide epitopes. Type II infections produce antibodies that react with at least 1 of the 6-II, d6-II, and 7-II peptide epitopes. “Atypical” serotypes identified strain-specific antibodies that reacted with both the Type I/III and Type II strain-typing peptides or did not react (“Nonreactive” [NR]) with any of the allele-specific peptides. Red circles depict individual serum sample results for uveitis patients without OT; black diamonds depict individual sera results for OT patients. Strong reactivity against single-diagnostic peptides (with no reactivity against any other peptides, including recombinant SAG1 [rSAG1]) was considered false-positive. False reactivity generally occurs in <2% of samples [27]. C, Fourteen patients had specific reactivity against the 6-I/III peptide and rSAG1 protein, consistent with infection by a Type I or III strain. D, The majority of serum samples (86/170 or 51%) reacted with both rSAG1 and 1 or more of the Type II allelic peptides designated 6-II, d6-II, and 7-II, consistent with infection by Type II strains. E, Sixteen serum samples possessed Atypical serotypes that reacted strongly with both Type II and Type I or III peptides as well as rSAG1. F, 54/170 (32%) serum samples only reacted with rSAG1 and were peptide-NR. Abbreviation: OT, ocular toxoplasmosis.