Antigenic and genotypic changes in some parasites as a result to development in different hosts

Abstract

The efficacy of Hydatid cyst (HC) antigen in diagnosis of infection is still affected by the host from which the HC developed and extracted. This mainly due to the ability of each HC-Genotypes to develop in a special host. The present study investigates the diagnostic efficacy of HC protoscolices somatic antigens (HCPsS-Ag) extracted from HC obtained from different hosts in diagnosis of zoonotic hydatidosis. The study concluded the suitability of HCPsS-Ag of animal origin to replace that of human origin was affected by the animal species. HC of sheep origin appeared more compatible with that extracted from human than that of equine as a source of antigen to use in diagnosis of zoonotic hydatidosis. Comparing the antigenic similarity of these antigens on genotype bases revealed that HC-G6 genotypes extracted from infected patients contain eight polypeptide fractions react specifically versus HC-G6 infected patient’s sera. Five of them (28,32,38,59 and 89 Kilo Dalton (KDa) and two of them (28 KDa and 45 KDa) reacted versus HC-G1 and HC-G4 infected sheep and equine sera, respectively. Six fractions in HCPsS-Ag-G1 of sheep react versus HC-G1sheep infected sera, four (28,32,52 and 58 KDa) and two of them reacted versus HC-G6 and HC-G4 infected patient and equine sera, respectively. Two fractions in HCPsS-Ag-G4 of equine only reacted versus infected human sera and sheep sera. This part concluded that HCPsS-Ag from HC genotypes that developed in humans and animals as HC-G6 and HC-G1 can substitute each other for diagnosis of infection than antigens extracted from non-zoonotic HC-G4 of equine. The protein fraction at MW 28 KDa proved as non-host dependant fraction, extracted from any HC-genotype and showing the same sensitivity, specificity and contain the same number of specific polypeptides in diagnosis of Anti-HC-Ab in sera of any infected host. The variations in the parasite genotypes concerning infected hosts were further investigated in Giardia intestinalis as another example. After amplification and sequencing of a 292 bp fragment of 16S-rRNA ribosomal unit from 20 children and 28 calves Giardia isolates using nested PCR, the study proved infection of calves by zoonotic Giardia (Assemblage A) and by non-zoonotic (Assemblage E). The first assemblage (A) is common in buffalo calve, easily distributed by these animals elsewhere and infect the surrounding human as this assemblage (A) was isolated from both diarrheic children and their close contact calves. The study succeeded to identify a protein fraction at the molecular weight (MW) of 29-34KDa as specific