First Molecular detection of Theileria annulata in Bangladesh.

In South Asia, Theileria annulata is known to be less pathogenic to local breeds of Bos indicus cattle comparing to Bos taurus cattle and some of mix breeds between them. Seroepidemiological surveys have revealed high sero-prevalence of T. annulata in asymptomatic local breeds of cattle in Bangladesh. Therefore, these asymptomatic infection in local breeds can be infectious sources to more sensitive breeds. In this study, 59 bloods of cattle showing no symptom were screened by species specific PCRs for hemoto-protozoan parasites, to prove the existence of T. annulata parasite in asymptomatic cattle in Bangladesh. The T. annulata infection was confirmed along with other parasitic species, and this is the first report of T. annulata DNA detection in Bangladesh.

Stochastic induction of Theileria annulata merogony in vitro by chloramphenicol.

Theileria annulata inhabits the cytoplasm of bovine leukocytes where it can be found as a multinucleated schizont. The schizont is the pathogenic stage of the life cycle and by interfering with host signalling pathways, it induces unlimited host cell proliferation and protection against apoptosis. In the infected animal, the schizont differentiates to the merozoite life cycle stage in a process called merogony. This takes place within the host leukocyte, resulting in the production of merozoites that are subsequently released by leukocyte lysis. In established cultures of T. annulata-transformed cells, merogony does not spontaneously occur, but the process can be activated by a shift in temperature. In this study we show that chloramphenicol induces schizont differentiation in proliferating T. annulata-transformed cells. We demonstrate that chloramphenicol-induced merogony is inherently asynchronous and has a quantitative basis. The process is accompanied by the down-regulation of schizont-specific surface proteins, de novo expression of merozoite-specific markers such as Tamr1 and Tams1 and the morphological hallmarks of merogony. Chloramphenicol-induced parasite differentiation was found to be associated with diminished proliferation potential and extensive morphological changes of the host cell, including increased numbers of pseudopodia. Significantly, chloramphenicol treatment can accelerate merogony induced by elevated temperature, supporting postulation that the differentiation event is a stochastic process that can be manipulated to alter the outcome of parasitic infection.

Disruption of synchrony between parasite growth and host cell division is a determinant of differentiation to the merozoite in Theileria annulata.

The multinucleated macroschizont stage of the protozoon Theileria annulata is an intracellular parasite of bovine leukocytes. The parasite induces the host cell to proliferate, and divides in synchrony with the immortalised host cell. Differentiation to the next stage occurs within the host cell culminating in the release of merozoites and destruction of the leukocyte. In this study clones of Theileria annulata macroschizont-infected cell lines were isolated by limiting dilution and tested for differentiation to the merozoite stage (merogony). Two cloned cell lines underwent differentiation with enhanced efficiency, while two others were of lower efficiency. Quantification was carried out using monoclonal antibodies, which showed that over 90% of the cells in an enhanced cloned cell line could be induced to differentiate. By carrying out induction at 41 degrees C for limited periods of time followed by culture at 37 degrees C evidence was obtained that differentiation to the merozoite is a two-step process: a preliminary reversible phase, followed by a second irreversible phase of differentiation. Analysis of the nuclear number of the macroschizont and the growth rate of the cloned cell lines showed that the ability to differentiate was associated with an increase in nuclear number (size) of the macroschizont, generated by a disruption in the synchrony between parasite growth and host cell division. We believe that these results reveal a relationship between a reduction in parasite division and differentiation, and that there are similarities between stage differentiation in parasites and cellular differentiation in higher eukaryotes.