Ten thiadiazine derivatives were tested in vitro for antiparasitic effects against both extracellular promastigotes and intracellular amastigotes of Leishmania amazonensis. The results showed that the evaluated compounds exhibited a strong antiproliferative activity on all developmental stages of the parasite. The minimal inhibitory concentration and the 50 % effective concentration values against the promastigote were 2.1-5.1 microg/ml and 0.6-1.8 microg/ml, respectively. The tested compounds caused an irreversible inhibition of the promastigote growth either after 1 h of treatment with 10 microg/ml or after 24 h with 1 microg/ml. Also, the thiadiazine derivatives were active against amastigotes producing between 12 and 89 % of reduction of infection at 100 ng/ml. However, the compounds exhibited high toxicity and provoked inhibition of the phagocytosis in the murine host cell.

Toxoplasmic encephalitis (TE) is a mayor cause of central nervous system infection in patients with acquired immunodeficiency syndrome (AIDS). Toxoplasma antibodies were detected in 56 of 79 patients with AIDS (71%), in the present study. Fourteen out of 57 seropositive patients developed TF (25%) and had Toxoplasma gondii antigen detected in their urine. For this, most of them received an effective therapy, with the subsequent disappearance of the symptoms and discontinuity of excretion of the T. gondii antigens. Our results suggest that the monitoring of T. gondii antigen in the urine of AIDS patients may be useful to decide on the proper time for therapy, as well as to avoid the beginning of neurologic signs in these patients.

A longitudinal study was performed with sera and urine of patients with acquired immune deficiency syndrome (AIDS), taken before, during and after clinicallyToxoplasma gondii is recognized as an important pathogen during pregnancy and the perinatal period (Remington & Desmont 1983). It has recently gained additional interest as a cause of life threatening opportunistic diseases in immunocompromised individuals, including patients with acquired immune deficiency syndrome (AIDS) and transplant recipients (Postman et al. 1988). Toxoplasmosis is a major opportunistic parasitic disease in AIDS patients. Toxoplasmic encephalitis (TE) can only be diagnosed very late since the classical serological tests based on the detection of anti-T. gondii IgG and IgM are inefficient in these patients (Luft & Remington 1988). More sensitive diagnostic tests for the early diagnosis of TE are needed.The detection of antigens or parasites of T. gondii in different biological fluids is an accurate and rapid diagnosis. Recently, some researchers have described the use of T. gondii DNA sequence for the diagnosis of toxoplasmosis using the polymerase chain reaction (PCR) (Dupcuy-Camet et al. 1993). We have reported the use of coagglutination assay to detect T. gondii antigens in the urine of infected mice (Fachado et al. 1990) and also in the urine of AIDS patients (Fachado et al. 1992 We have developed the coagglutination technique using urine of AIDS patients with acute cerebral toxoplasmosis. In order to confirm the toxoplasmic origin of the antigens detected by CoAToxo, the immunoblot was employed. The results also were correlated with clinical symptoms of toxoplasmosis, response to specific chemotherapy and anatomopathologic exam if the patient died. MATERIALS AND METHODSProduction of the soluble antigenic extract -A soluble antigenic extract was prepared from the RH strain of T. gondii. The trophozoites were taken from peritoneal exudates of mice, three days after infection. The exudate was centrifuged at 650xg for 10 min in 2 ml of 0.1M phosphate buffer saline (PBS), pH 7.2-7.4 to eliminate host cell residues. The supernatant was discarded and the pellet resuspended with 2ml PBS and repeatedly passed through a 26 gauge needle in order to break the macrophages. It was again centrifuged at 160xg during 10 min at 4ºC and the supernatant centrifuged at 650xg during 10 min at 4ºC. The pellet was washed three times in 50 ml PBS. The suspension was then sonicated at 4ºC to obtain the parasites antigens, and centrifuged at 650xg during 2 hr at 4ºC . The protein concentration of the T. gondii antigens suspension was determined by the method of Lowry et al. (1951).Production of antiserum -The anti-Toxoplasma antiserum was prepared by dilution of 0.5 ml of the T. gondii antigens (1.3 mg/ml of protein) in the same volume of PBS. The diluted antigenic solu-