Immunization of mice with gamma-irradiated intramuscularly injected schistosomula of Schistosoma mansoni

Abstract

SUMMARYThe parameters involved in the induction of resistance against Schistosoma mansoni by injection of irradiated, artificially transformed schistosomula were studied in mice. Single intramuscular injections of 500 schistosomula exposed to radiation doses in the range 2·3 to 160 krad. resulted in significant protection (in the range 20 to 50% as assessed by reduced worm burdens) against a challenge infection administered at intervals from 3 to 24 weeks post-vaccination. However, schistosomula irradiated with 20 krad. consistently resulted in better protection than those exposed to either higher or lower radiation doses despite the persistence of stunted adults from the infections irradiated with 2·3 krad. Vaccination with 40 krad. schistosomula resulted in significant protection in terms of reduced worm and tissue egg burdens and increased survival following lethal challenge. Varying the number of irradiated schistosomula, the frequency and route of their administration, the site of challenge and the strain of host all failed to enhance the level of resistance. However, percutaneously applied, irradiated cercariae were found to be more effective in stimulating resistance (60%) than intramuscularly injected, irradiated schistosomula (40%).

Studies on the development of anti‐schistosomular surface antibodies by mice exposed to irradiated cercariae, adults and/or eggs of 5. mansoni

“…Significant levels of resistance were manifest in three of the four groups vaccinated with irradiated cercariae and also in the chronically infected group. As previously found, 20 krad-attenuated infections stimulated higher levels of resistance than 40 krad infections (Bickle et al 1979a) and double vaccination with either 20 or 40 krad cercariae stimulated greater resistance than a single dose.…”

Specific cross‐protection between Schistosoma bovis and S. haematobium induced by highly irradiated infections in mice

“…Attenuation of the immunizing infection by irradiation is well established in studies on immunity to schistosomes (Minard et al 1978, Bickle et al 1979a. It avoids the complications of egg-induced pathology and the use of hosts with varying and ill-defined degrees of susceptibility which may have enhanced immunity due to host nonpermissiveness.…”

Mechanisms of protective immunity against 5. mansoni infection in mice vaccinated with irradiated cercariae. VI. Influence of the major histocompatibility complex

“…Mice vaccinated with highly irradiated cercariae or schistosomula of Schistosoma Correspondence: Dr Alan Sher, Building 5, Room 112, NIH, Bethesda, MD 20205, USA. mansoni, develop resistance to subsequent challenge infection with unattenuated cercariae (Minard et al 1978, Bickle et al 1979). This resistance is first evident as early as 10 days after vaccination reaches peak levels at 4-6 weeks and then gradually wanes (Minard et al 1978).…”