Pathological Effect On Pregnant Balb/c Mice Experimentally Infected With Schistosoma Mansoni And Subsequent Immunological Implications On The Offspring

Abstract

Parasitic worms of the genus Schistosoma cause schistosomiasis. It has been shown that pregnancy has no effect on schistosome infection and that infection during pregnancy confers protection to offsprings born to infected mothers in human beings and C57BL/6 mice. However, the pathological effect of Schistosoma mansoni infection in pregnant BALB/c mice and the subsequent immunological implications on the offsprings has not been studied. This work therefore sought to compare pathology in experimentally infected pregnant BALB/c mice and the subsequent immunological implications on the offsprings. A pilot experiment (1) was done to determine the appropriate time when to mate the mice after infecting them (group A), and of infecting offsprings from infected mothers (group E) and those from uninfected mothers (group F). Mice, six weeks old, were randomly placed into four groups W, X, Y and Z. They were all infected at week 1 but mated at one week interval i.e. week 1, 2, 3, and 4 for W, X, Y, and Z respectively. Perfusion was done at week 7 to recover adult worms. Gross pathology and histopathology of the liver tissue were studied at week 4 and 7. Results for mice in group Wand Z consistently conformed to the expected disease pattern with regard to presence of adult worms at week five and mild pathology by week 7. However mating was done at week 1post infection as for W instead of week 4 post infection as for Z so that perfusion is done when mice have given birth after the gestation period of 21 days. Mice born to infected mothers were weaned at 3 weeks post delivery and bled for serum at two week intervals between week 4 and 16 post delivery. ELISA results failed to show a specific downward trend in schistosome antibody levels with time as expected. However, week 12 was set for infecting mice in group E and F because the antibody level was lower than that at week 10, and week 16. In the second (IT) experiment, mice in group A were infected and mated (the pregnant group) while those in group B were infected and not mated (positive control). Mice in group C were not infected (negative control). but were mated. The in vitro proliferative responses to schistosome antigens, IgG antibody levels, gross pathology as well as histopathology were studied. Antigen-stiinulated 'proliferative responses showed that pregnancy suppressed' cellular immune responses butt not humoral responses. Lymph node and spleen cells responses were lower in group A than B while ELISA showed higher antibody levels in group B than A. More worms were recovered from group A than group B at week 6 and 7. Granuloma diameter in A was smaller than that in B. In the third (III) experiment, infants born to infected mothers in group A were used as group E and their pathology compared with those born to uninfected mice in group C of experiment II (as group F). Infection was done at week 12 after birth in both groups. Results showed that mice born to infected mothers were better protected from S. mansoni infection than those born to naive mothers with regard to the adult worm