The long-term goal of this project is to understand the pathogenesis of relapsing fever and Lyme disease; the primary focus for the next project period is relapsing fever. The current model of relapsing fever is that changes of the polymorphic Vmp lipoproteins are the determinants of antigenic variation during infection, that changes in Vmp proteins are the result of intermolecular or intramolecular recombinations at the vmp expression site, and that some genetic switches are followed by a period during which further diversity is generated through templated partial gene conversions. The project's specific hypotheses are these: (i) Some if not all Vmp proteins differ in structure to the extent that not only are they distinctive with respect to the host's immune system but also with respect to their in situ associations with and effects on host tissues. (ii) The sequence of the transcriptionally active vmp gene at the expression site determines in part which of several possible vmp genes follows it during an infection. (iii) Post-switch mutations of newly- arranged vmp genes are the consequence of either epigenetic differences between otherwise identical vmp genes at different loci or transient differences between expression sites after intramolecular deletions and those after gene conversions.
The specific aims to address these hypotheses are the following: (1) Further characterize the function and structure of Vmp proteins by (a) identifying the mechanism(s) for entry by one serotype of B. turicatae into the central nervous system under conditions in which another serotype of the same strain is excluded, (b) quantitatively assessing the pathologic and functional effects of CNS invasion by borrelias, and (c) initiating investigations of the conformation of Vmp proteins. (2) Further define the relationship between the vmp repertoire's diversity and requirements for establishing an infection and avoiding the immune response by (a) continuing the identification of expressed and silent vmp genes and pseudogenes, (b) analyzing sequences of vmp genes and Vmp proteins with respect to their evolution, and (c) comparing by DNA sequence relapse serotypes resulting from infections with clonal populations of serotypes representing different vmp sub-families. (3) Further define the genetic mechanisms for changes at the expression site by (a) assessing whether more than one Vmp protein is expressed at a time by individual cells, (b) determining whether there are epigenetic differences between vmp genes and/or whether otherwise identical expression sites transiently differ consequent to the type of recombination that produced them, and (c) developing a genetic system whereby mutations or reporter genes are introduced into borrelias.
Showing the most recent 10 out of 85 publications
