Ralph E. Duxbury

Trypanosoma congolense: immunization of mice, dogs, and cattle with gamma- irradiated parasites.

Abstract In a series of experiments involving 21 groups of mice, between 50 and 100 per cent of those inoculated with irradiated Trypanosoma congolense were completely protected from challenge inoculations of unirradiated T. congolense . Of 37 mice given a second or third challenge after 9 and 26 weeks, 23 remained parasite-free. Unimmunized control mice invariably developed parasitemias and most of them died as a result of the infection. Dogs and cattle failed to withstand challenge inoculations after they were treated with irradiated trypanosomes, though prepatency in these animals was longer than that of the controls.

Soluble antigen fluorescent antibody test (SAFA) for human filariasis.

Abstract A test was developed for the serologic diagnosis of bancroftian filariasis and onchocerchiasis by using soluble extracts of adult Dirofilaria uniformis, D. immitis , or Dipetalonema witei as antigen. The test is performed by immersing cellulose acetate filter paper discs in the antigen solution and allowing them to dry. The discs are then incubated in diluted serum, rinsed in a buffered saline solution, soaked in fluorescein-conjugated antiserum, rinsed again, and mounted on tape. The tape is placed on the drum of the chromatograph door of a fluorometer to determine objectively the degree of fluorescence of the individual discs. This technic was evaluated with 259 human sera from well-documented cases. Reactions were observed in 82% of sera from bancroftian filariasis patients and 86% from onchocerciasis patients, whereas 97% of sera from healthy controls gave negative results in the test. Most of the “false” negatives occurred in adolescents and all of them were in persons under 30 years of age. Few cross reactions were observed with sera from individuals with proven trematode, nematode, protozoan, mycotic, and bacterial infections and with sera from patients with lupus erythematosus. Occasional cross reactions were obtained with sera from individuals with schistosomiasis haematobia, leishmaniasis, and leprosy. Since these sera were collected in areas which are endemic for filariasis, it is possible that the reactions were specific. The degree of sensitivity and specificity of the test, the objectivity of mechanical reading, and the possible use of minute amounts of blood and antigen for testing suggest that this procedure may be useful in the serologic diagnosis of human filariasis and may provide means to apply quantitative immunologic technics to problems in endemic areas.

Experimental infections with African trypanosomes: IV. Immunization of cattle with gamma-irradiated Trypanosoma rhodesiense

Abstract Cattle immunized with gamma-irradiated Trypanosoma rhodesiense were protected against a challenge inoculation of unirradiated trypanosomes given 1 wk later. These animals were still resistant when rechallenged after 8 mo and some residual immunity persisted for 14 mo after immunization. Animals which had undergone self-cure after infection were resistant when challenged 14 mo later. No resistance was observed in animals challenged with a heterologous strain of T. rhodesiense. The infections observed in unprotected bovines were of a mild nature. Leukopenia and fever were common early in the course of infection, but no anemia was evident at any time.