The controversial circumstances relating to the classification of the benign Theileria species from Japan, Australia and Britain, which are frequently referred to as T. sergenti/buffeli/orientalis group parasites, was reviewed. Our recent systematic comparisons suggest a possibility that the Japanese T. sergenti (minor piroplasm in common parlance) might be a new species and the Australian T. buffeli and British T. orientalis might belong to one and the same species. The necessity for the review of the genus name for these benign Theileria species was also briefly discussed after the morphological studies
of their schizogony.
A panel of monoclonal antibodies has been produced against the protozoan parasite Cryptosporidium parvum which is a major cause of diarrhoeal disease in man and other animals. C. parvum oocysts from both a human and a bovine case of cryptosporidiosis were used as immunogens. A total of 11 different monoclonal antibodies were obtained which could bind to formalin-fixed oocysts. One was IgA but the remainder were all of IgM isotype. The reactivity of these monoclonal antibodies against a series of C. parvum oocysts obtained from 25 patients in Chile was examined using indirect immuno-fluorescence. Although a mixture of all of the 11 antibodies would have detected oocysts in each of the samples, no one monoclonal antibody recognised all oocysts. Each antibody showed a different recognition pattern. Thus by using these monoclonal antibodies we have demonstrated that there is tremendous antigenic variability among C. parvum oocysts. These antibodies should prove most useful in examining the epidemiology of C. parvum infections.
Merozoite surface antigen 2 (MSA2) is a Plasmodium falciparum vaccine candidate. Antibody responses to MSA2 in Melanesians naturally exposed to P. falciparum were investigated by ELISA using the recombinant MSA2 protein known as Ag 1609 and 65 overlapping synthetic peptides spanning predominantly the conserved N and C terminal regions of MSA2. Significant differences were obtained between control and malaria exposed subjects in the ability of sera to bind to Ag 1609. The median absorbance obtained with control sera was 0.36 whereas that obtained with sera from malaria exposed subjects was 1.8. The sera of ninety-five percent of malaria exposed subjects reacted significantly with Ag 1609. The percentage reactivity of the control sera with Ag 1609 was 39%. Overall the serological responses to the synthetic peptides were low and well defined B epitope regions were not delineated. The median absorbances were in general higher for the malaria exposed group than the controls with these differences being significant for five N terminal peptides and 14 C terminal peptides. One peptide (KECTDGNK) at the conserved C terminal end was identified for further investigation as a possible immunodiagnostic epitope. Immunisation of mice with an allelic form of Ag 1609 (namely Ag 1615) produced antibodies to the conserved C terminal of MSA2 but not to the N terminal.
Anti-Babesia rodhaini monoclonal antibodies (mAb), namely: 1-E7, 2-H2 and 3-B8, significantly suppressed the development of high parasitemia in BALB/c mice infected with B. rodhaini and all mAb-treated mice survived the infection. While, only monoclonal antibody 3-B8 showed some inhibitory effect against Babesia microti, with mice showing high parasitemia of 18.04 ± 2.69 %, at 9 days post-exposure. Westernblot analysis of B. rodhaini and B. microti parasite extract reacted with anti-B. rodhaini monoclonal antibodies showed cross-reactive bands of molecular weights 62 and 55 kilodaltons. Comparison of the antigenic components of B. rodhaini and B. microti using polyspecific sera revealed several shared or common parasite antigens of molecular weights 62, 55, 45-47, 41, 30-31 and 26-28 kilodaltons.
Isoenzyme electrophoresis is described in the literature as a useful tool for the differentiation of Sarcocystis (S.) species. Isoenzyme patterns of Sarcocystis cystozoites were studied by Atkinson and Collins (1981), Ford (1986), O'Donoghue et al. (1986), and Ford et al. (1987) in order to characterize and compare isolates of different Sarcocystis species.
The purpose of our study was to investigate, whether S. arieticanis, S. ovicanis, S. capracanis, and S. hircicanis could be distinguished by the isoenzyme profiles of their sporozoites, which are life-cycle stages present in the definitive carnivorous hosts. Isoenzyme electrophoresis was performed on polyacrylamide gels, since this gel matrix was reported to give an improved resolution of bands compared with starch gels (Freese and Markus, 1990). In addition, an enzyme screening assay is described, which was performed in order to identify detectable enzyme activities in the samples prior to the isoenzyme electrophoresis.