EXPRESSION OF ACQUIRED-IMMUNITY TO HELIGMOSOMOIDES-POLYGYRUS IN MICE CONCURRENTLY INFECTED WITH TRYPANOSOMA-CONGOLENSE

The effects of concurrent Heligmosomoides polygyrus and Trypanosoma co ngolense infection on the expression of acquired resistance to homolog ous nematode challenge mere studied in female outbred TO mice. Mice we re infected with 500 infective larvae (L-3) of H. polygyrus and the in fection was terminated by anthelminthic treatment on Day 12, when the worms were adults, Eight days Later sub-groups of these pre-exposed mi ce, and of similar mice which had not experienced the previous infecti on with H. polygyrus, were either simultaneously infected with 500 L-3 of H. polygyrus and 10(4) bloodstream forms of T. congolense, or with only one of these parasites, or mere not infected. The experiment was monitored by routine parasitological and immunological techniques, in cluding. quantitative assessment of worm burden, trypanosome parasitae mia, growth of nematodes and measurement of the parameters reflecting pathological and antibody responses for 30 days after immunization, Co ncurrent H. polygyrus and T. congolense infection resulted in abrogati on of the partial immunity against challenge infection with H. polygyr us in the pre-exposed mice, and in depressed humoral antibody response s following infection, Mortality mas greatly reduced in pre-exposed mi ce infected with T. congolense alone compared to naive mice, The growt h of male H. polygyrus worms was not affected by either the immune or infection status of their host, Although the increased size of the fem ale worms from pre-exposed and then concurrently infected mice compare d to similar mice infected only with H. polygyrus was significant, the egg production per worm was not affected. (C) 1997 Australian Society for Parasitology, Published by Elsevier Science Ltd.