الفهرس 
Introduction
Species distinction: traditional and modern approachesOnly 14 pages are availabe for public view
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Abstract
The current study clarified the antigenic similarity between S. haematobium, S. mansoni, F. hepatica and hydatid cyst from the aspect of molecular weight using SDS-PAGE and from the aspect of immune reaction using Westren Blot (WB) technique against S. mansoni serum. The crude protein extracts were used instead of purified ones. Although complex mixes of proteins are difficult to proteomic analysis, the examination of these crude extracts had the advantage of increasing the chance of detecting the most abundant common proteins expressed by these parasites and that could be relevant with respect to the aim of our study.
The differences in the number and MWs of bands detected on SDS-PAGE fractionation of the antigens used in the present study compared to those observed in previous studies could be due to differences in the extract preparation or in the sensitivity of the staining used to reveal the protein bands. Also, the decreased number of polypeptide bands detected by WB technique might be due to decreased sensitivity of the test by repeated freezing and thawing of the used serum.
The SDS-PAGE analysis of antigens of S. mansoni (AWA, SEA), S. haematobium (AWA, SEA), F. hepatica (TSE, AWV) and Hydatid cyst (CHF) was conducted and the gel was stained with Commassie brilliant blue. It was noticed that, the polypeptides ranged from 73- 68 kDa and that ranged from 42-38 kDa were shared with the AWA, SEA of both examined schistosomes and CHF. Bands ranged from 58-55 kDa were common in S. mansoni AWA, S. haematobium (AWA, SEA) and F. hepatica AWV. Bands within the range of 52- 47 kDa and 26-22 kDa were detected in all tested antigens. Bands with MW of 34-31 kDa were observed in S. mansoni (AWA, SEA), S. haematobium SEA and CHF. Bands ranged between 15- 17 kDa were shared with all tested antigens except for F. hepatica AWV.
It was valuable to note that, not all these shared polypeptides bands were recognized by western blotting of the antigens against S. mansoni serum (diluted 1:25). The protein bands with MW of about 60 kDa crossly reacted with S. mansoni serum and detected in antigens of S. mansoni (AWA, SEA), S. haematobium (AWA, SEA), F. hepatica (TSE, AWV) and CHF. Bands at MW of 54-55 kDa were common in S. mansoni SEA and F. hepatica AWV. The polypeptides bands 50- 52 kDa were detected in S. mansoni AWA, S. haematobium antigens (AWA, SEA) and TSE of F. hepatica. These immunoreactive proteins could be used to develop dual vaccine against human schistosomes and fascioliasis. Also, the polypeptide bands of rang from 38-40 kDa shared with AWA, SEA of both schistosoma spp. and CHF. Again these immunoreactive proteins could be prepared as a common vaccine against S. mansoni, S. haematobium and hydatid disease.
The explanation of the detected cross reactivity in the examined parasites antigens when immunoblotted against S. mansoni serum may be due to the fact that, F. hepatica and S. mansoni have evolved in similar ways to avoid the immune responses of their hosts. Therefore, it was not surprising that several of the common proteins identified between F. hepatica and S. mansoni antigens as they have biological functions related to immune evasion mechanisms. Another explanation for the cross reactivity among these parasites is that, the chronic parasite diseases produce a discharge of highly immunogenic substances into the host. These substances elicit cross reactive or non specific immune response such as in case of the schistosomiasis, fascioliasis and hydatidosis.
On the other hand, It was significant to point out that an immunologic fraction with MW of 31-32 kDa was considered to be the most frequently documented fraction in S. mansoni AWA and it was specifically reacted with the S. mansoni serum. Thus it is considered of high diagnostic importance and therefore could be used as a serologic marker.
The genetic characterization of S. mansoni, S. haematobium, F. hepatica and hydatid cyst is useful to achieve the basic information necessary the field control and may have implications for the diagnosis and control of the diseases caused by these parasites. To understand the genetic variability and population and for reconstruct and investigate the phylogenic relationships of the examined parasites, the ITS markers were used. These genetic markers were popularly used in molecular systematics world over in different organisms for determing out species origin and classification. The ITS sequences allow the accurate characterization of species to solve a number of taxonomic problems where morphological features are limited or when the parasitic materials is disturbed or incompletely bodied.
Herein, adult specimens of S. mansoni, S. haematobium, F. hepatica and hydatid cyst were characterized on the bases of sequences of ITS (1 and 2) regions; in fact, previous studies have shown that these sequences provide reliable genetic markers for the accurate differentiation and identification of platyhelminths. For each examined parasite, reference ITS (1 and 2) sequences were recovered from GenBank and used for sequence alignments and phylogenic tree construction.
The ITS1 and ITS2 sequences of S. mansoni, S. haematobium showed 1-2 base difference along with those previously published in GenBank. These differences may be due to sequence error and to a lesser extent may be as a result of hybridization between the different Schistosoma spp. At the same time, F. hepatica ITS1 and ITS2 showed 100% identity with no base differences along with those reported on GenBank regardless to their locality or to their hosts, indicating no impact of the locality on the sequence of ITS regions. Also, no sequence variation were identified in ITS regions could be attributed to variation in the host.
On the other hand comparison of the ITS1 and ITS2 sequences of the examined hydatid cyst with those on GenBank data base indicated high mismatches at least 40/447 bases differences were noticed. The high diversity of the ITS sequences found in examined hydatid specimen, highlights the fact that, Echinococcus spp. maybe not a uniform population possibly exhibiting several phenotypic differences. It would be interesting to see if the parasites from different linage exhibit any epidemiological or biological traits in terms of pathology, host compatibility and treatment efficacy as increased genetic diversity has been noted to possibly have an effect on such characteristics.