Vaccine Candidate Antigen Sm20.8: Immunological Studies By Peripheral Blood Mononuclear Cells From Patients With Schistosomiasis

¹Khalifa E. Khalifa, ²Salwa A. Fouad, ³Magdy M. Mohamed, ¹Manal I. Moustafa, ²Karim A. Kamal, ³Amr M. Karim and ¹Adel El-Missiry

¹Parasitology Department, Bilharzial and Medical Research Center, Faculty of Medicine, Ain Shams University, ²Naval American Medical Research Unit No.3 (NAMRU-3) Abbassia, ³Biochemistry Department, Faculty of Science, Ain Shams University, Cairo Egypt.

We have previously demonstrated that nacked DNA vaccination with Schistosoma mansoni Sm20.8 kDa confers 30% reduction in the number of worms upon challenge infection into naïve mice. Sera from animals immunized with the recombinant protein (rSm 20.8kDa) mediated killing of 3h schistosomula in vitro complement mediated cytotoxicity assay. We conducted the present study to investigate the immunogenicity of this recombinant protein when used to stimulate cytokine production by peripheral blood mononuclear cells (PBMC) from hepatointestinal (HI) and hepatosplenic (HS) patients. Cells from patients with the HI or HS responded with elevated IL-4 levels (62.7±11 and 57.6± 6.9 pg/ml respectively) when in vitro stimulated with rSm 20.8 as compared to uninfected controls (35±9.4 pg/ml). However, no significant difference was observed when the levels of IL-4 were compared between the two clinical stages of the disease. Similar trend towards increased secretion of IL-4 by ConA-stimulated cells from patients with HI or HS was observed. No significant changes in ConA-and rSm 20.8-induced gamma interferon levels were noticed in cells from HI and HS patients; although cells from both group displayed significant higher level of gamma interferon over the control group (P<0.05). Sera from patients with HI mounted significant level (P=0.01) of schistosome specific IgG4 (O.D= 2.5±0.4) as compared to those displayed by patients with HS (O.D=1.3±0.2) or control subjects (O.D= 0.1±0.01). Together these data demonstrate that recombinant Sm20.8 induce humoral and Th2 cellular immune responses and is likely to contribute as a candidate epitope to a subunit vaccine designed to stimulate protective responses.