SAG-related sequence SRS34A, Toxoplasma gondii (P22)

The T. gondii SAG2 locus has been widely used for strain identification. This gene encodes a major protein, P22. Studies of SAG2 gene using the restrictive endonuclide fragment length polymorphism (RFLP) method of HhaI restriction endonuclide found that there are two alleles at this site, including toxicity specificity and non-toxicity specificity. Studies have shown that SAG2, together with another surface antigen molecule P30(encoded by the SAG1 locus), plays an important role in the invasion of host cells by T. gondii tachyzoites. Antibodies that recognize SAG2 molecules cause the accumulation of tachyzoites on host cell membranes. When the antibodies are removed, this colony of parasites enters the host cell, resulting in an overall enhancement of the invasion.SAG2 is also used in serological diagnostics and vaccine development.