Schistosoma Mansoni: Partial Molecular Characterization of the Gene Encoding Zinc Finger Protein of the Lung Stage (7-Days Schistosomula)

Schistosomiasis is a serious parasitic disease with world-wide distribution, causing
an estimated 200 000 deaths per year. Despite the fact that the global distribution of
schistosomiasis has changed significantly in the past 50 years, particularly in regions
where control strategies have been successfully employed, the disease remains
endemic in over 70 developing countries and more than 200 million people are
estimated to be harboring the disease. Chemotherapy, although effective, it does not
prevent re-infection, and in addition, partial drug resistance may occur. Hence,
immunological intervention in the form of a vaccine would contribute to the success
of the present efforts. Most of the trials in the development of anti-schistosomiasis
vaccine were involving membrane-associated antigens contained in the adult
Schistosoma mansoni (S. mansoni) tegument because they are capable of
stimulating protective immunity. In the current study, a trial to obtain antigen
varieties which could be vaccine candidates by incorporating internal antigens of the
lung stage of S. mansoni (7-days schistosomula) in addition to the tegumental
antigens was done. The soluble extract of the lung stage was obtained by sonicating
the whole parasite, then, coupled to Sepharose-4B column for affinity purification of
pooled sera collected from chronically infected patients. The purified sera were used
to immunoscreen λgt 11 cDNA library of 7-days schistosomula. The plaques
purification after three rounds of immunoscreening gave a number of cDNA clones.
one of the isolated clones (clone 2-4) was amplified by PCR using λgt 11
forward and reverse primers, then ,cloned in a plasmid vector (PCRTMII). The
cloned insert was partially sequenced 270 bp from the 5/- end using Sp6 primer as
well as 187 bp from the 3/-end using T7 primer. The sequenced part of the clone
showed it has two open reading frames (ORFs) with 31-36% homology to the gene
that encodes Zinc Finger protein (the transcriptional regulatory protein) from a
number of eukaryotic species including human , rat and mice.