Targetomes of infection-specific small RNAs of Bartonella bacilliformis

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Bartonella bacilliformis (Bb) is a highly-virulent, sand fly-vectored bacterium responsible for Carrión’s disease in humans. This chronically-neglected tropical disease is re-emerging in endemic regions of the Andes and expanding into non-endemic areas (i.e., lower altitudes and more diverse habitats) of Peru, Ecuador and Colombia. An estimated two million people in an area of ~145,000 square-km in South America are at risk of infection by Bb, and incidence rates of 12.7 / 100 person-years have been reported in endemic regions. Bb infections are potentially life-threatening, with fatality rates as high as 88% if left untreated, and ~10% fatality rates following antimicrobial intervention. In non-endemic regions, Carrión’s disease manifests as an acute febrile illness with an ~80% reduction in erythrocyte hematocrit (Oroya fever), whereas in endemic regions, angiomatous skin lesions (verruga peruana) and chronic bacteremia are most common, effectively creating a human reservoir for the pathogen. Our long-term goal is to elucidate how Bb regulates expression of gene products required to survive in the sand fly vector and human host, with overarching objectives of: a) generating information that can be applied to the eventual eradication of Carrión's disease and b) providing a model of virulence gene regulation in Bartonella and other arthropod-vectored, pathogenic bacteria. Our discovery of 24 human-infection-specific sRNAs and 8 sand fly-specific sRNAs (from a total of 160 Bb sRNAs identified) suggests that sRNAs are used to post-transcriptionally control translation in the host and vector, respectively. We hypothesize that human-infection-specific, trans-acting sRNAs regulate transcripts for gene products that are required for Bb survival in humans. The hypothesis will be addressed by two specific aims. In aim 1, we will characterize the mRNA targetomes of three prominent sRNAs through crosslink-Seq analysis of live Bb. In aim 2, we will confirm and analyze the identified sRNA-mRNA interactions using EMSAs and reporter constructs. Results of the study will provide a foundational analysis of the regulons for three dominant, infection- specific sRNAs of Bb. More broadly, the research will also establish a model for elucidating sRNA regulons in arthropod-vectored bacterial pathogens.