Immunolocalization and pathological alterations following Strongyloides venezuelensis infection in the lungs and the intestine of MHC class I or II deficient mice

摘要

The present study, investigated the mechanisms involved in the immune responses of Major Histocompatibility Complex class I or class II knockout mice, following Strongyloides venezuelensis infection. Wild-type C57BL/6 (WT), MHC II(-/-) and MHC I(-/-) mice were individually inoculated with 3000 larvae (L3) of S. venezuelensis and sacrificed on days 1, 3, 5, 8, 13 and 21 post-infection (p.i.). Samples of blood, lungs and small intestines were collected. The tissue samples were stained with hematoxylin-eosin for the pathological analysis. The presence of the parasite was demonstrated by immunoperoxidase analysis. MHC II(-/-) mice presented a significantly higher number of adult worms recovered from the small intestine on day 5p.i. and presented elevated numbers of eggs in the feces. The infection by S. venezuelensis was completely eliminated 13 days after infection in WT as well as in MHC I(-/-) mice. In MHC II(-/-) mice, eggs and adult worms were still found on day 21p.i., however, there was a significant reduction in their numbers. In the lung, the parasite was observed in MHC I(-/-) on day 1p.i. and in MHC II(-/-) mice on days 1 and 5p.i. In the small intestine of WT mice, a larger number of parasites were observed on day 8p.i. and their absence was observed after day 13p.i. Through immunohistochemistry analysis, the parasite was detected in the duodenum of WT on days 5 and 8p.i., and in knockout mice on days 5, 8 and 13p.i.; as well as in posterior portions of the small intestine in MHC I(-/-) and MHC II(-/-) on day 13p.i., a finding which was not observed in WT mice. We concluded that immunohistochemistry analysis contributed to a more adequate understanding of the parasite localization in immunodeficient hosts and that the findings aid in the interpretation of immunopathogenesis in Strongyloides infection.