T. gondii Pruigniund and RH strains were maintained in vitro as previously described [89] . Soluble toxoplasma antigen (sTAg) was prepared from RH strain tachyzoites as previously described [90] . The Pruigniud strain was used for in vitro tachyzoite infections at a ratio of 3:1. The Me49 strain of T. gondii was maintained in infected Swiss Webster and CBA/CaJ mice. For infection, brains from infected mice were removed placed in 3 ml sterile 16PBS and passed 3-5 times through an 18.5 gauge followed by 20.5 and 22.5 gauge needle. The number of cysts in a 30 ml aliquot was determined microscopically. Brain suspensions were adjusted to 100 cysts/ml and mice were infected each with 20 cysts intraperitoneally. Infection studies of C57Bl/6 and AMCase null mice were conducted at least four times with a minimum of 7 biological controls. C57Bl/6, CBA/CaJ (Jackson, Bar Harbor, ME) and Swiss Webster mice (Charles River, Wilmington, MA) were maintained in a pathogen free environment under IACUC established protocols at the University of California Riverside. AMCase-null mice were generated by targeting exon 5 using loxP/CRE recombination as previously described [85] . The AMCase gene deleted mice were of a mixed background, C57BL/6NTac:129SvEvBrd, and were backcrossed to C57/BL6 for at least 10 generations. These mice were generated and maintained under IACUC protocols established by Pfizer.