Genetic and phenotypic analysis of Tunisian Theileria annulata clones

Abstract

Many parasite species are known to show high levels of genetic diversity, yet the consequences of this diversity for host-parasite interactions are not well understood. Variation in phenotypic traits such as growth rates and the ability to form transmission stages are raw material for natural and artificial selection to act upon with consequences for the evolution of the parasite species and disease control. In order to study genetic and phenotypic diversity amongst Theileria annulata parasites, a collection of 52 parasite clones was generated from cattle isolates and tick material recently collected in Tunisia. Genetic diversity was assessed using PCR-RFLP and monoclonal antibody markers, and genetically distinct clones selected for further study. Clones varied significantly in their growth rates in culture at 37 degrees C, their viability after a period of culture at 41 degrees C and their differentiation rates into transmission stages after culturing at 41 degrees C. The viability of a clone after culturing at 41 degrees C could not be predicted from its growth rate at 37 degrees C, but across clones, differentiation rates were positively correlated with growth rates at 37 degrees C. All 3 in vitro measures are likely to have relevance to parasite-host interactions in animals with clinical theileriosis, and should be acted on by within-host and between-host selection.

Dynamics of Multiple Infection and Within‐Host Competition in Genetically Diverse Malaria Infections

“…Not only do our results suggest that competitive suppression is genotype-specific and that levels of strain-transcending and strain-specific immunity depend on the exact clones infecting the host, we have even demonstrated that competitive hierarchies can be completely reversed depending on which clone infects the host first. Interestingly, such a mosaic of competitive interactions and reversal of competitive dominance could explain why in many diseases (e.g., Chotivanich et al 2000;Nevils et al 2000;Taylor et al 2003) virulence polymorphisms are maintained (Mackinnon and Read 2004). They indeed suggest that, contrary to theoretical expectations, avirulent parasites may play a larger role in nature than we have up till now granted them.…”

Sequence Polymorphism of Cytochrome b Gene in Theileria annulata Tunisian Isolates and Its Association with Buparvaquone Treatment Failure

“…Moreover, the multiclonal character of T . annulata isolates collected from such clinical cases [ 26 – 27 ], prompted us to clone the isolates by limiting dilution which allowed us to analyse a greater number of sequences and to identify a larger number of mutation.…”

Competitive suppression in mixed-clone parasite cultures

“…Stock cultures of the four clones were maintained separately in exponential growth in RPMI medium (Brown 1987;Taylor et al 2003).…”

“…The four clones were different parasite genotypes (based on polymerase chain reaction/restriction fragment length polymorphism and monoclonal antibody analysis) cultured in host cells from the same cow (Taylor et al 2003). Stock cultures of the four clones were maintained separately in exponential growth in RPMI medium (Brown 1987;Taylor et al 2003).…”

“…Three replicates were conducted, providing six cultures of each two-clone mixture and single-clone control. Live cell density was determined by FACScan analysis using 40 ml of the culture and fluorescent beads of a known concentration (Taylor et al 2003). (a) Data analysis Replication rate characteristics for each single-clone culture were estimated assuming logistic growth.…”