Antigenic Relationships among Human Pathogenic Orientia tsutsugamushi Isolates from Thailand
Fig 2
An overview of antigenic mapping and genetic variation of O. tsutsugamushi Thai isolates.
Panel A: Antigenic map of indirect immunofluorescence titres in Table 3. Calculating the antigenic distance between points gives a measure of antigenic similarity allowing quantitative visualization of serological data for O. tsutsugamushi. Points close to each other are antigenically similar. Each circle represents an O. tsutsugamushi isolate, and each square represents a serum. The grid background of panel A indicates antigenic distance; the spacing between grid lines is 1 antigenic unit, corresponding to a twofold dilution of patient sera in the indirect immunofluorescence assay. The points are colored according to their genetic group, as determined in panel C. Panel B: A genetic map of the strains and sera in panel A, with additional prototype strains. The grid spacing is every 10 units of genetic distance (amino acid mutations). The genetic map was made using the same method as the antigenic map, but using the genetic distance (number of mutations) as opposed to a measure of antigenic distance. Panel C: A phylogenetic tree of the 56kDa protein amino acid sequences of O. tsutsugamushi strains and human sera used in this study, with bootstrap values on the nodes.