Persistence mechanisms in tick-borne diseases : tick-borne diseases

The use of new, highly sensitive diagnostic methods has revealed persistent infections to be a common feature of different tick-borne diseases, such as babesiosis, anaplasmosis and heartwater. Antigenic variation can contribute to disease persistence through the continual elaboration of new surface structures, and we know in several instances how this is achieved. Known or suspected mechanisms of persistence in babesial parasites include cytoadhesion and rapid variation of the adhesive ligand in Babesia bovis and genetic diversity in several merozoite stage proteins of different Babesia spp. In Anaplasma, extensive variation in the pfam01617 gene family accompanies cycling of organism levels in chronic infection. One result from the pioneering research at Onderstepoort is the definition of a related polymorphic gene family that is likely involved in immunity against heartwater disease. We are beginning to understand the sizes of the antigenic repertoires and full definition is close, with the possibility of applying simultaneous high-throughput sequencing to the order of 1 000 small genomes. We also, for the first time, can consider modifying these genomes and looking at effects on persistence and virulence. However, important biological questions remain unanswered; for example, why we are seeing a new emerging Anaplasma infection of humans and is infection of endothelial cells by Anaplasma significant to persistence in vivo

Cross reacting determinants in trypanosome surface antigens

Meeting: Conference on Recent Advances in the Knowledge of Pathogenicity of Trypanosomes, 20-23 Nov. 1978, Nairobi, KEIn IDL-329

varDB: common ground for a shifting landscape

Antigenic variation is a phylogenetically widespread phenomenon thought to lead to survival benefits for the pathogen. Although governed by genetic mechanisms, antigenic variation is ultimately manifested in variant proteins. The varDB database is an attempt to gain an overview of common structures and functions of variant proteins related to enhanced survival. varDB provides a wealth of sequence data and several tools to facilitate their analysis, but current limitations preclude achievement of its full promise. A critique of this database and how it could serve the scientific community is provided here