Reduced Infectivity in Cattle for an Outer Membrane Protein Mutant of Anaplasma marginale
ABSTRACTAnaplasma marginaleis the causative agent of anaplasmosis in cattle. Transposon mutagenesis of this pathogen using theHimar1system resulted in the isolation of anomp10operon insertional mutant referred to as theomp10::himar1mutant. The work presented here evaluated if this mutant had morphological and/or growth rate defects compared to wild-typeA. marginale. Results showed that the morphology, developmental cycle, and growth in tick and mammalian cell cultures are similar for the mutant and the wild type. Tick transmission experiments established that tick infection levels with the mutant were similar to those with wild-typeA. marginaleand that infected ticks successfully infected cattle. However, this mutant exhibited reduced infectivity and growth in cattle. The possibility of transformingA. marginaleby transposon mutagenesis coupled within vitroandin vivoassessment of altered phenotypes can aid in the identification of genes associated with virulence. The isolation of deliberately attenuated organisms that can be evaluated in their natural biological system is an important advance for the rational design of vaccines against this species.