Genetic diversity within one gene enables the bacterium that causes syphilis to escape notice by the human immune system, ScienceAlert reports.
To understand how syphilis can cause repeated infections in the same person, researchers from the University of Washington compared the genomes of two Treponema pallidum samples obtained from the same patient, years apart. As they report in PLOS Neglected Tropical Diseases, they found that the two T. pallidum samples were highly similar, except for one gene where they exhibited a high degree of variability. Deep sequencing of the tprK gene further found a high level of intra-isolate heterogeneity.
"Across the about 1.1 million bases that make up the bacteria's genome there were about 20 changes total. That's very low," senior author Alex Greninger, assistant professor of laboratory medicine at the UW School of Medicine, says in a statement. "But on this one gene, we saw hundreds of changes."
This gene, tprK, encodes a protein found on the bacterial surface, and such proteins are often what is recognized by the host immune system, and the researchers say the diversity seen in this gene could help T. pallidum avoid sparking an immune response.