Comparative study of three immunoassays for detection of immunoglobulin M antibodies against Toxoplasma gondii.

Immunoglobulin M antibodies against a major serological antigen (Mr 6 kD) were detected in human sera by indirect ELISA, antibody capture ELISA, and immunoblot test. In contrast to indirect ELISA, the immunoblot test gave no false positive reactions, not even with those sera containing a high level of rheumatoid factor. However, the immunoblot test gave false negative results with sera which gave positive results in both ELISA tests. The antibody capture ELISA gave no false negative reactions. All positive sera except one reacted specifically with Toxoplasma gondii antigens.

Serologic evidence of toxoplasmosis in captive and free-living wild mammals in Kenya.

Sera from 27 captive and 132 free-living mammals in Kenya were tested for antibodies to Toxoplasma by the Sabin-Feldman dye test. Of these 8 of 8 (100%) captive carnivores, 14 of 19 (74%) captive herbivores, 11 of 14 (79%) free-living carnivores and 97 of 118 (82%) free-living herbivores were found to have Toxoplasma antibodies. The feeding and drinking habits of the various herbivore species were considered as possibly facilitating exposure to Toxoplasma oocysts; also the feeding on prey in the wild and on meat in captivity as favoring exposure to the cyst form of Toxoplasma.

Response of white mice to inoculation of irradiated organisms of the Toxoplasma strain RH.

Chemotherapeutic agents available for use against toxoplasmosis are usually not suitable for prophylactic purposes because of their toxicity. The observed increasing number of activated latent infections with Toxoplasma, especially in immune suppressed patients, requires that safe techniques are available for use during the patient's regression period. Pretreatment of mice with Toxoplasma killed by irradiation appeared to induce resistance to challenge with virulent organisms. Survival times of six months have been observed to date. Increasing effectiveness was seen after more than one administration. Further investigation into the duration of effective resistance is needed; the question of at which intervals subsequent inoculations should be performed in order to acquire a booster effect, if any, has still to be solved before application to man can be recommended.

Investigation into the occurrence of toxoplasma in pharyngeal and palatine tonsils by inoculation of tonsillar tissues into mice.

Among randomly chosen persons in the age group one to seven years the generally accepted proportion of positive dye tests for Toxoplasma is about eight per cent. The 124 children in this age group studied by us represent a selected group in which a higher percentage is to be expected. The group included 63 boys and 61 girls, from whom no blood samples were available for serological investigation. An arbitrary percentage of twice the eight per cent would result in 20 cases with a positive dye test. In the four successful attempts to isolate Toxoplasma all four cases were boys. Among 20 persons aged 14 to 21 years in whom a positive dye test could actually be established, one attempt to isolate the organism in a girl of 16 years of age was successful. No generalized lymph node enlargements were mentioned in the history of the five successful cases, only relapsing laryngo-pharyngeal symptoms. In the five successful isolations the Toxoplasma organisms present in the tonsillar organs appeared not to be virulent for the mice used; the organism was recovered in the cystic form from the brains of the mice. In subsequent animal passages the virulence could be influenced by the number of cysts per inoculum.