THE EGYPTIAN JOURNAL OF MEDICAL SCIENCES. VOL. 17-No 2-DECEMBER 1996 (ISSN: 1110-0540) Egypt. J. Med. Sci. 17 (2) December, 1996: 637-651 IMMUNOLOGICAL EFFECTS OF NHN VACCINE, A CHEMICALLY MODIFIED BIOMPHAL4RIA ALEXANDRINA SNAIL ANTIGEN By Azza S., Elhamshary, Amany F. Elfakahany, El-Sayed A. El-Tahawy, Mahmoud M. Elfouly, Abo El-Hamed M. Elhawary and Magda H. Mekky Departments of Parasitology, Pharmacology & Therapeutics, and Pathology, Benha Faculty of Medicine, Zagazig University Benha, Egypt ABSTRACT The development of a vaccine that brings schistosomiasis under immunological control has been the goal of many investigators all over the world for decades. This study was designed to test the effect of NHN vaccine which contains chemically modified Biomphalaria alexandrina Snail antigen on reducing the worm burden, inducing body immune response through raising the IgG titre and on reducing the incidence of pathological changes in organs of mice vaccinated then infected compared to mice infected without vaccination (prophylactic effect). Statistical analysis of the results showed that NHN dose-dependently raised the IgG titre in the vaccinated mice. The number of worms recovere from mice pre-injected with the vaccine then challenged with schistosome cercariae was about 10% of the number recovered from mice challenged without pre-vaccination. Vaccination with NHN significantly reduced the incidence of pathological changes in livers and intestines in challenged mice. These results suggest a possible potent effect of the compound tested (NHN vaccine) in preventing and even curing the pathological consequences of schistosomiasis infection. INTRODUCTION Despite the remarkable progress achieved in combating schistosomiasis in certain parts of the world (Chen, 1989; Anon 1992), the World Health Organization recently concluded (WHO 1993) that the global number shows no Egypt. J. Med. Sci. 17 (2) 1996