Vitamin E-deficient diets enriched with fish oil suppress lethal Plasmodium yoelii infections in athymic and scid/bg mice

Mice fed vitamin E-deficient diets containing omega-3 fatty acids survive infection with lethal Plasmodium yoelii. The current study sought to determine if antimalarial T- and B-cell responses were required for such dietary-mediated protection. In the first set of experiments, nu/nu mice (which lack alphabeta T-cell-receptor-positive T cells and do not produce antimalarial antibody) and nu/+ mice were fed casein-based diets containing 4% menhaden oil, with or without vitamin E supplementation, for 4 weeks prior to infection with lethal P. yoelii. All mice fed diets containing vitamin E developed fulminating parasitemias and quickly died, whereas both nu/nu and nu/+ mice fed diets deficient in vitamin E controlled their parasitemias for the first 18 days of infection. Thereafter, the nu/nu mice became anemic and died, whereas the nu/+ mice produced antimalarial antibodies and survived. In the second set of experiments, scid/scid.bg/bg mice (which lack B cells and alphabeta and gammadelta T cells and have reduced NK-cell activity) were fed the experimental diet for 6 weeks and then infected with the less virulent 17XNL strain of P. yoelii. Mice fed vitamin E-containing diets quickly died, whereas those fed the vitamin E-deficient diet survived without developing detectable parasitemias. Results from these experiments show that under prooxidant dietary conditions, mice were able to control and even survive malaria in the absence of malaria-primed T cells and antimalarial antibody. These results emphasize the importance of cellular oxidative processes in parasite elimination.

Effects of pyran copolymer on host resistance of mice to Plasmodium yoelii

Female B6C3F1 mice treated with 25 mg/kg pyran intravenously (i.v.) on days -4 and -3 were more susceptible to nonlethal Plasmodium yoelii 17XNL or lethal Plasmodium berghei ATCC-30090 than untreated mice or mice treated intraperitoneally (i.p.). Female B6C3F1 mice treated with pyran i.p. displayed enhanced resistance to Listeria monocytogenes as compared to untreated mice or mice given pyran i.v. Peritoneal exudate cells (PEC) primed by pyran i.p. possessed enhanced ability to kill Listeria but impaired ability to destroy Plasmodium. Phagocytosis of Covaspheres by PEC was greater for mice given pyran i.p. than those given pyran i.v. Chemiluminescence evoked by zymosan was less for PEC from mice given pyran i.v. than for those from untreated mice or those given pyran i.p. Chemiluminescence was greater for adherent splenocytes from mice treated with pyran i.p. than for those from untreated mice or those from mice treated i.v. Pyran administered i.v. is less effective in modulating the host immune response than pyran administered i.p. Immunomodulatory agents such as pyran have adverse as well as beneficial effects depending upon the route of administration.

Susceptibility of hamsters to caecal amoebiasis by oral infection

A method is described for successfully establishing caecal amoebiasis in hamsters which were not fed and which were pretreated with 1 ml of magnesium sulphate every 24 hours for three days and then given 12 x 10(5) trophozoites of the HM-1 axenic strain or 18 x 10(5) trophozoites of the HK-9 axenic strain of Entamoeba histolytica by the oral route. All the animals developed diarrhoea within 24 hours of infection. When the animals were killed on the fifth day after infection the caecum was swollen and fused. Large macroscopic ulcers full of pus could be seen in the caecum. None of the control animals showed any of the changes mentioned above.

A study of Giardia infection in irradiated and thymectomized mice

Thymectomized and irradiated mice were infected with Giardia cysts obtained from a human source. The animals were killed on the third, sixth, ninth, 12th and 15th days post-infection. The intestinal contents were collected and a count of motile trophozoites was made. The results were compared with an infected control group of animals which were similar to the experimental group in age, sex, weight and species. There was a considerable increase in the trophozoites counts in the experimental group on the third, sixth, ninth and 12th days of the experiment with the differences from the control group being highly significant (P less than 0.001) on each comparable day of study. However, no such difference was observed on the 15th day post-infection. Both groups of animals showed an initial rise in the trophozoite counts with the peak on the 9th day post-infection followed by a fall in the counts on the 12th and 15th day. The difference on each successive day of experiment was highly significant. Six out of 30 (20%) mice in the experimental group died, with all the deaths occurring within the first 6 days post-infection. On the other hand, there were no deaths in the control group and in the uninfected thymectomized and irradiated group. These observations were further substantiated by the more severe histological changes in the villi and lymphocyte infiltration in the experimental group than in the control group. Therefore it is surmised that the intensity of Giardia infection in mice with depressed cell mediated immunity is considerably increased. However, it is interesting to note that these animals show a definite trend towards recovery as do normal animals with Giardia infection.