Enteric viral infections in pre-school children in Karachi, Pakistan.

A prospective study was conducted in Karachi, Pakistan on the virology of enteropathogens excreted by children with acute gastroenteritis and the results were compared with a control group of healthy children. Rotavirus and Adenovirus detection was done using ELISA techniques, while enterovirus isolation was done by virus culture. In 1990, 12.3% children with acute watery diarrhoea excreted rotavirus, as compared to 24.4% children in 1991. None of the healthy children excreted adenovirus 40 and 41. Preliminary results of 1992 revealed that rotavirus was seen in 13% of children with acute watery diarrhoea and adenovirus in 10% of children. Enteroviruses were isolated in the same frequency in all three groups i.e. children with acute watery diarrhoea, children with poliomyelitis and healthy children. Non-polio enteroviruses were excreted in 50-52% in all the 3 groups. The rate of enterovirus excretion is much higher than seen in other developed countries and is the same in children with diarrhoea and healthy children.

Hepatitis A, B and C seroprevalence in Pakistan.

A cross sectional study was conducted to determine the seroprevalence of Hepatitis A, B, and C virus in healthy Pakistani children. HAV IgG antibody was assayed in 258 subjects and it was found that 94% children by 5 years of age had HAV IgG-antibody. The overall seroprevalence of HAV IgG antibody was 55.8% and IgM 5.3%. HBVsAb levels assayed in 236 healthy children showed a seroprevalence of 2.97%. Similarly, HCV antibody seroprevalence was found to be a low 0.44% in healthy children. HAV is a major cause of Hepatitis, as compared to HBV and HCV which are of low endemicity.

Purification of Gnathostoma spinigerum larval antigens by monoclonal antibody affinity chromatography.

An immunoaffinity column was prepared by coupling a partially purified Gnathostoma spinigerum-specific IgG1, MAb SK-6C4 (5 mg/ml) to CNBr-activated Sepharose 4B. Ten milliliters of approximately 0.3 mg/ml of crude soluble G. spinigerum larval antigens (GsAL3) were loaded onto the affinity column at a flow rate of about 5 ml/hour. Elution of the bound antigens was accomplished using 50 mM diethylamine-HCI containing 0.15 M NaCL, pH 11.5. The average amount of eluted antigens obtained by one passage of crude GsAL3 (1-4 mg) through 4 to 8 ml of column matrix was 143 micrograms (range, 67 - 414 micrograms). The minimal amount of purified GsAL3 detectable by ELISA using MAb SK - 6C4 (100 micrograms/ml) was 50 ng/ml. The SK - 6C4 affinity-purified GsAL3 was found to be relatively pure and immunologically specific as determined by SDS-PAGE and Western blotting, respectively.

Immunohistochemical localization of Gnathostoma spinigerum larval antigens by monoclonal antibodies: I. Light microscopy.

Immunohistochemical localization of antigens in advanced third-stage larvae of Gnathostoma spinigerum (GsAL3) was studied by indirect enzyme immunostaining using 7 G. spinigerum specific monoclonal antibodies, FS-3D11, SS-5H5, SK-6C4, SK-4E1, SK-7G6, SD-8D4 and SA-9B5. All these MAb belong to the IgG1 subclass and only FS-3D11 and SS-5H5 recognize carbohydrate determinants. Each MAb exhibited a different reaction pattern and staining intensity in sectioned GsAL3. FS-3D11 bound primarily to the intestinal brush border whereas SS-5H5 reacted with various tissues of the parasite including intestinal epithelium and brush border, lateral cords, muscle, pseudocoel, and cuticle. SK-6C4 predominantly stained muscle, however, SK-4E1 and SK-7G6 exhibited a lack of labeling. SD-8D4 bound to the cuticle and the lateral cords whereas SA-9B5 reacted primarily with the pseudocoel. These results suggest that antigens sharing common epitopes are present in various structures of the larvae with the intestine being the most antigenic site. The present data also suggest that certain GsAL3 antigens recognized by the MAb obtained in this study are sensitive to formalin fixation and/or paraffin embedding since for 2 out of the 7 MAb staining was negative.