Leucocytozoon caulleryi is an etiological protozoan of chicken leucocytozoonosis commonly found in various Asian countries. Leucocytozoon caulleryi is transmitted by Culicoides biting midges and shows high infectivity and pathogenicity to chickens. The severity of clinical symptoms and mortality depend on the number of sporozoites inoculated. Severely infected chickens often die of hemorrhage, almost all of the chickens challenged with sporozoites after a primary infection at various ages show complete resistance to reinfection and the acquired immunity is expressed against the second generation of schizogony. Soluble antigens are found in the sera of chickens between the 10th and 15th day after sporozoite inoculation. These antigens originate from second-generation schizonts. Antibodies against the antigens of each developmental stage of L. caulleryi are recognized in the sera of infected chickens. Each stage is antigenically distinct.
The occurrence and distribution of circumsporozoite (CS) protein of Plasmodium yoelii 17X (lethal) was observed during sporogonic development in Anopheles stephensi mosquitoes. The CS protein was visualized by using a polyclonal antibody against synthetic peptides (QGPGAP) 4 of the immunodominant repeats of the CS protein and immunogold labeling. The CS protein is synthesized in immature oocysts from day 5 after infective blood meal when sporozoite formation has not yet started. The CS protein appears on the plasmalemma of oocysts and associates with the surface of sporoblasts and budding sporozoites. Micronemes and the pellicle of mature sporozoites were immunolabeled.
The binding capacity of C1q onto Toxoplasma gondii (T. gondii) parasites at each infectious stage was examined by using the immunofluorescence assay (IFA) with purified human C1q, rabbit anti-human C1q antibodies and fluorescein -isothiocynate conjugated goat anti-rabbit IgG antibodies in parallel with the IgM-binding to the parasite.
Any possibly contaminated natural antibodies to the parasite were completely removed from the anti-human C1q-preparations by repeated absorption with the parasite in advance. Parasites incubated with C1q before adding anti-C1q antibodies have shown the specific fluorescence on their outer surface membrane, whereas those without any addition of C1q have no specific fluorescence. The intensity of fluorescence differed in stages, and cystozoites and trophozoites seemed to have significantly higher C1q-binding activities than sporozoites. Furthermore, C1q-binding sites have been differently located from IgM-binding sites, or anterior poles, on the parasite.
These observations indicate that T. gondii parasite has the antibody- independent binding capacity to human C1q on its outer surface membrane.
Interactions between parasites and host sells play an important role in the infection process. The adhesive protein fibronectin has been shown to be involved in the interaction between Trypanosoma cruzi and host cells. Trypanosoma cruzi epimastigotes grown in axenic culture bound 125I-fibro-nictin in an energy-dependent manner. Initial binding induced the expression/activation of further fibronectin receptors or activation of a fibronectin-specific uptake system. This binding could be inhibited by fixing the parasites with formalin, metabolic inhibitors (e.g. dinitrophenol), changes in temperature and by an excess of unlabeled fibronectin. The binding was not inhibited by EDTA nor by the peptide Arg-Gly-Asp-Ser (RGDS), which is the recognition sequence from the major cell binding domain of fibronectin.
A pooled blood sample collected from wild deer (Cervus nippon yesoensis) in Hokkaido prefecture was inoculated to sika deer. Large and small type piroplasms were detected from the blood smear of inoculated deer. The form of large type piroplasm was oval, ring, amoeba or binary fission, and paired pyriforms. The size of this type was 1.00-3.50 um in length, and 0.80-1.50 um in width. The form of the small type piroplasm was like dot, comma, oval or bayonet forms and quadruple fission with the formation of a cross. The size of this type was 1.20-2.50 um in length, and 0.50-1.00 um in width. Clinical signs of fever, anemia and hemoglobinemia occurred with appearance of the large type-piroplasm in peripheral blood, only fever and anemia occurred by the small type-piroplasm. It was considered from morphological features and clinical signs that the large type resembles Babesia sp. and the small type Theileria sp. The two haemoprotozoa did not infect cattle. Bebesia sp. were transovary transmitted by Haemaphysalis longicornis to the deer.