Persistence mechanisms in 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 1000 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.

http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=19967928&retmode=ref&cmd=prlinks
PMID: 19967928  [PubMed – in process]

Onderstepoort J Vet Res. 2009 Mar;76(1):53-8.

Persistence mechanisms in tick-borne diseases.

Barbet AF.

Department of Infectious Diseases & Pathology, College of Veterinary Medicine,
University of Florida, Gainesville, Florida, USA.