Cloning of Toxoplasma gondii gene fragments encoding diagnostic antigens.

Two Toxoplasma gondii gene fragments, which encode polypeptides that can be used as diagnostic antigens in an enzyme-linked immunosorbent assay were cloned and their nucleotide sequence was determined. One of the fragments (derived from the H4 gene) is 682 bp long. The mRNA of the single-copy H4 gene is 1300 nt long. The fragment derived from the other gene, termed H11, is 197 bp long. The mRNA of the single-copy H11 gene is 1900 nt long. The native polypeptides encoded by the H4 and H11 genes are 25 and 41 kDa, respectively. Based on computer analysis of the deduced amino acid sequences of the polypeptides encoded by the gene fragments, both appear to be very hydrophilic and that encoded by the H11 fragment has a high antigenic index profile. These results are consistent with the diagnostic usefulness of the polypeptides encoded by the gene fragments.