Search

In this study, both digestive and hermaphrodite glands in Biomphalaria alexandrina snails were examined by light microscope (LM) and scanning electron microscopy (SEM) in a trial to clarify its immunological role as defense mechanism against the parasite infection. B. alexandrina snails used were exposed individually to Schistosoma mansoni miracidia; according to their responsq they were classified into infected snails (shed cercariae) and non-infected snails (failed to shed cercariae). Snails not exposed to S. mansoni miracidia used as control. LM showing great histological alteration in tissues, of the both glands in infected snails, these changes represented by degenerated both oocyte and spermatocyte in hermaphrodite gland in addition to degenerated digestive gland while non-infected snails showing mild degenerated ova with normal spermatocytes also degenerated miracidia. inside granuloma like structure with concentric layers of fibroblast and haemocyte could be observed. By SEM we could detect extensively damaged and fibrosed non-motile cilia with exfoliation of tegumental surface in in- fected B.alexandrina while non-infected ones showing attached numerous cilia with some ballooning of the folds.

Schistosomiasis is a public health problem, in many developing: countries including Egypt, Determination of the antigenic relationship between S mansoni and its intermediate snail host (IMH) Biomphalaria alexandrina can open a new field for diagnosis and control of the dis- ease. In the present study infected and non-infected B. alexandrina foot and visceral hump tissue as well as S. mansion crude Ag (SWAg) were fractionated using SDS-PAGE. It's specific and cross reacted protein fractions were determine using EITB versus experimentally prepared mice hyper immune sera (HIS) versus each antigen. After treatment of fractionated S.mansoni crude worm antigens (SWAg) versus HIS produced after vaccination of mice by the same Ag, 8 kda protein fractions ranged from 35-140 kda were reacted specifically. Treatment of fractionated B.alexandrina infected and non-infected foot and visceral hump Ag versus previous HIS revealed presence of common polypeptides bands between SWAg and non-infected snail antigens. The fraction at 135 kda, 68 kda, were detected in all cases, while that at 40-42 kda and that at 35 kda was diagnosed in SWAg and that of infected snails only. The fraction at 68 kda was reacted specifically between SWAg and all tested fractionated snail antigens either that of foot or visceral hump when they treated separately by HIS of mice vaccinated by each snail A eparately. The fraction at 135 kda was common between SWAg and snail (infected and non-infected) visceral hump antigen. The fraction at the level of 110 kda was diagnosed inSWAg, in non-infected foot antigen and visceral hump Ag. The fraction at the level of 46-48 (da are common between SWAg and snail foot and visceral hump Ag after treated by HIS of mice vaccinated by foot Ag, Presence of common antigenic fractions between snail tissues and Schistosoma species can prefer an easily source of antigen valuable for diaguosis or vaccination as well as can be considered as new tool for determination to the snail IMH of new discovered trematode Darasites.

The present study documents that in Bioniphalaria alexandrina coordinated responses to Schistosoma mansoni infection are modulated by receptor-mediated opioid signals. Rather comprehensive tests in susceptible and resistant snails have demonstrated: I- the presence of an endogenaus opioids in the snail hemolymph (in particular, Leu-enkephalin-like material). II- in vitro treatment of snail hemocytes with synthetic Leu-enkephalin analogue (DADLE) resulted in the modulation of cellular adherence, and phagocytic activity. III- the addition of Naloxone, either alone or in combination whith DADLE, generally reduced hemocyte activity indicating opioid-receptor-mediated mechanism. V- the presence of DADLE or Naloxone modulated the level of IL-2-, TNF-gamma- and FNF-alpha-like molecules in S. mansoni resistant and susceptible snails. Specifically, DADLE and DADLE in combination with Naloxone generally were found to be capable of modulating resistant snail hemocytes at concentrations of 10(-6) and 10(-8) M. Similar actions after incubation with the same concentrations were not detected in the susceptible snails. These observations demonstrate the existence of a complete opioid system in B. alexandrina, associated with susceptibility and resistance to S. mansoni infection, the results suggest the role of such opioid system in molecular signaling within the host and in host-parasite interactions.

The first generation of 3 morphologically different forms of B. glabrata collected from Giza were compared for LC50 values susceptibility to bayluscide and copper sulphate (chemical molluscicides) and Anagallis arvensis and Calendula micrantha (plant molluscicides) and to Schistosoma mansoni infection. Form (2) as juvenile and adult were less sensitive to C. micrantha and A. arvensis. Form (3) as juvenile and form (1) as adult were least sensitive to CuSO4. Approximately the same susceptibility to bayluscide was observed in the 3 forms either as juvenile or adult. The sublethal concentrations of the molluscicides on B. glabrata 3 forms showed no significant difference in the growth or survival rate in between. Form (2) was significantly higher in the egg lying capacity. The total protein concentration was not affected except in certain cases where the increase was primarily due to the increase in the globulin concentrations which indicate with the marked increase observed in the urea concentration and marked increase or inhibition in the activity of either AST or ALT that the digestive gland of the 3 forms of snails is seriously affected by molluscicides. The 3 forms of B. glabrata showed low susceptibility to infection with the local strain of S. mansoni.

Distribution pattern of Schistosoma mansoni miracidia level of host susceptility/resistance and the basic cellular responses brought into play during the parasite development. Several snail stocks showed a wide spectrum of host reaction to the parasite. From the present study, a vigorous "resistant-type" cellular response to invading miracidia is seen in the histological sections of non-susceptible snails. In this respect, they were classified in our study as "resistant snails". B. alexandrina experimentally infected with S. mansoni exhibit a wide range of histopathological and immunological changes. The rate of phagocytosis as well as the actual number of hemocytes were determined in different groups of snails during the infection cycle. The significant fluctuation (increase and/or decrease) in circulating hemocyte number was only correlated with a shift in hemocyte populations in the first two days after exposure to the infective stage. The in vitro phagocytic activity of resistant snail hemocytes was found to be higher than that observed in susceptible snails. The observed phagocytic activity indicates that susceptible snail hemocytes were capable of recognizing parasite antigen in vitro, despite of that, they were not able to clear the infection in vivo. Thus suggesting the presence of endogenous factors preventing the immune system of susceptible snails from destroying the developed parasite larvae. Therefore, the mechanism underlying the susceptibility of the snails should be investigated by studying the host-parasite interactions.

Mice were immunized (2x) subcutaneously at zero and 21st day with different antigen preparations. Splenocytes and mesenteric lymph nodes (MLN) cells were obtained from both immunized and control groups at 14th 21st and 42nd day post the 2nd immunization. The direct immunofluorescent assay was applied using anti mouse CD3+, D4+, CD8+, and IgG monoclonal antibodies to detect panel T-cells, T-cell subsets and B-cells respectively. The observations revealed that the splenic CD3+ T-cells did not show any considerable interrelation either between experimental groups or different time intervals post-immunization (P.I.). Meanwhile, UV-irradiated and PZQ-treated groups showed slight increase at the 2nd and 4th week P.I. as compared with the control group. The UV- and gamma-irradiated groups showed a significant elevation in CD4+ T-cells when compared with control group throughout the time of experiment, whereas, PZQ-treated group showed a significant increase at the 2nd and 4th week P.I. only. The frequency of CD8+ T-cells was elevated in all the experimental groups as compared with control group at 2nd, 4th and 6th week P.I. The MLN CD3+, CD4+ and CD8+ T-cells did not reveal any considerable changes between the experimental groups and control throughout the time of the experiment. A gradual decrease was observed in all the experimental groups by proceeding the time of the experiment. Splenic and MLN B-cells did not show considerable changes between the experimental groups and control group during the course of the experiment. It is concluded that these antigens could possibly stimulate cellular immune response upon their use as a protective antigens.

It can be safely said that up till now, no method of vaccination (including recent genes encoding vaccines) has yet proved to be totally effective since they gave partial and low levels of protection against S. mansoni infection. The objective of this work is to try testing the immunogenic effect of two purified non infected B. alexandrina hepatopancreas through histopathological changes in liver of Swiss albino mice (15-20 gm). Gel filtration chromatography was used to fractionate the crude antigen into five fractions followed by re-fractionation and determination of their molecular weights by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Four dilutions of Fiv (20000-29000 daltons) and Fv (20000-24000 daltons) were injected in two groups of mice (33 each) at weekly intervals and another control group was injected with phosphate buffer saline (PBS) in the same manner. Sacrification was done seven weeks from infection with 100 S. mansoni cercariae through immersion method. The results revealed that there is marked histopathological changes in liver of the control group in comparison to the two vaccinated groups which appear more or less normal with slight inflammatory infiltrate.

Current stratigies for the control of schistosomiasis are based primarily on chemotherapy but successful vaccination against infection has been also demonstrated in several host parasite models. In this study, the immunogenic effect of two purified antigens (Fiv 20-29 000 daltons & Fv 20-24 000 daltons) extracted from non infected hepatopancreas of B. alexandrina as measured by worm load, state of copulation and viability of ova in tissues. The antigens were prepared using gel filtration chromatography and their molecular weights were estimated through sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Four dilutions from each antigen were prepared and injected in two groups (33 each) of Swiss albino mice at weekly intervals. A control group was injected with phosphate buffer saline (PBS) in the same manner. All mice were injected with 100 cercariae using immersion method. Sacrification was done regularly after 7 weeks of injection. On the basis of worm load, Fiv gave protection of 44% while Fv gave only 36%. The number of worms in copula was significantly reduced and they became delicate, fragile, stunted and malformed. Both antigens gave a significant reduction in total viable eggs in tissues.