Schistosoma Mansoni: the Identification of Some Highly Immunogenic Surface Antigens of the Lung Stage Larvae as Promising Vaccine Candidates Against Schistosomiasis

Background: Schistosomiasis is a global health problem caused by several species of
schistosome blood flukes. It is endemic in 74 developing countries; 200 million people
are infected worldwide, causing an estimated 200.000 deaths / year. Chemotherapy,
although effective, it does not prevent re-infection, and in addition, partial drug
resistance may occur. This is why the development of long - lasting immunity through
vaccination may be the real solution to control the spread of the disease. Objective:
The molecules on the surface or associated with the tegument of the lung stage (7-
days schistosomules) of Schistosoma mansoni (S. mansoni) are the major target in
the present study as potential vaccine candidates. Materials and methods: Nonidet P-
40 (NP-40) extracted soluble surface proteins of 7-days schistosomules were
subjected to 12.5% Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis
(SDS-PAGE). The separated surface proteins were electrotransfered onto a
nitrocellulose membrane (PVDF), then, western blotting was performed. The non
specific binding sites on the membrane were blocked by 1% non-fat dry milk in
phosphate buffered saline (PSB), then, the membrane was incubated with pooled sera
(primary antibody) collected from S. mansoni chronically infected patients and
absorped to E. coli lysate. Anti-rabbit IgG conjugated with alkaline phosphatase was
used as the secondary antibody. Results: A number of different immunogenic
extracted surface antigens of 7-days schistosomules have been identified by the
antibodies in the sera of S. mansoni chronically infected patients of different
molecular weights, 18 kDa, 28 kDa, 33 kDa, 38 kDa, 40 kDa, 42 kDa, 45 kDa, 50
kDa, 62 kDa, 66 kDa, 81 kDa and 116 kDa. In conclusion: Progress in schistosome
genome research has offered a unique chance to move rapidly from genome
sequences to vaccine development. Proteins bound to the surface of parasites are
potential vaccine candidates, or they can be used for diagnosis. In the present study,
twelve surface proteins of the lung stage larva of S. mansoni with different degrees of
immunogenicity are identified; any one of these proteins could be a promising vaccine
candidate for S. mansoni.