immunopathological study of the fungus cryptococcus neoformans in mice 1Mahmood F.A and 2Alwan M.J

Abstract

The study aimed to investigate the effect of cryptococcal sonicated antigen and chitosan on the infection with this fungus which isolated from human skin lesions. Isolate of Cryptococcus neoformans was used to prepare the sonicated antigen, also 60 white mice from both sexes, at average age 8-10 weeks were getted and divided randomly into 4 groups equally and treated as following: First group: fifteen mice were immunized with 0.5ml of whole sonicated  Ags(Wsc Ag) (protein concentration14mg/ml) subcutaneous two doses, one week interval.Second group: fifteen mice were fed diet supplemented with chitosan 1g/kg diet for 6 weeks.Third group: Mice were immunized as 1st group and at the same time fed diet supplemented with chitosan as 2nd group. Fourth group: Mice, which seted as control positive group.

At day 28-30 post-immunization, delayed hypersensitivity  and  indirect  passive  haemagglutination  tests  were done, then 1^st, 2^nd, 3^rd and 4th groups were administrated  intraperitoneally with  0.3 ml of fungal suspension containing 1X107 fungal cells, all animals were sacrificed at day 30 post-infection. The results showed that the immunized animals and fed diet containing chitosan had values of delayed hypersensitivity test(1.99±0.02 at 24hours and 2.11±0.03 at 48 hours)and value of antibodies(160±29.6) higher than that of immunized animals only(1.75±0.03 at 24 hours and 1.81±0.03 at 48 hours)and value of antibodies(136±28.2).The immunized animals with whole sonicated cryptococcal antigens (1st group) expressed high values of delayed type hypersensitivity and high levels of Abs titer, as well as the chitosan stimulate the immune system in the second group and the best results of immunization were getted in the third group while all animals of control positive(fourth group)  were died at  the first week post-infection.

The current study showed that all the non-immunized and infected animals of the fourth group  were died during the first  2 weeks post-infection with severe fungal cells isolated from internal organs  and severe  suppurative  inflammatory  reaction in the examined organs  during early stage of infection  with granulomatous lesions appear at day 14 post-infection while no mortality  rate was seen in animal fed diet supplement with chitosan  with or without immunization(2nd and 3rd groups)  moderate fungal isolation and granulomatous lesions were recorded in the examined organs of  animals sacrificed at day 30 post-infection while  the immunized animals and fed diet containing chitosan showed that there is no fungal isolation and nor fungal cells in the histological sections with few histological degeneration  and small granulomatous lesions and sometimes absence of them in the examined organs. It concluded that cryptococcal sonicated antigen and chitosan have important role in protective immunity against C.neoformans infection.