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Differential gene expression in laboratory strains of human head and body lice when challenged with Bartonella
1Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA, USA.
Abstract:
Human head and body lice are obligatory hematophagous ectoparasites that belong to a single species, Pediculus humanus. Only body lice, however, are vectors of the infectious Gram-negative bacterium Bartonella quintana. Because of their near identical genomes, yet differential vector competence, head and body lice provide a unique model system to study the gain or loss of vector competence. Using our in vitro louse-rearing system, we infected head and body lice with blood containing B. quintana in order to detect both differences in the proliferation of B. quintana and transcriptional differences of immune-related genes in the lice. B. quintana proliferated rapidly in body lice at 6 days post-infection, but plateaued in head lice at 4 days post-infection. RNAseq and quantitative real-time PCR validation analyses determined gene expression differences. Eight immunoresponse genes were observed to be significantly different with many associated with the Toll pathway: Fibrinogen-like protein, Spaetzle, Defensin 1, Serpin, Scavenger receptor A and Apolipoporhrin 2. Our findings support the hypothesis that body lice, unlike head lice, fight infection from B. quintana only at the later stages of its proliferation.
Insights
Human body lice, unlike head lice, support rapid Bartonella quintana proliferation and exhibit distinct immune gene expression, suggesting differential immune responses to bacterial infection. This research offers insights into vector competence in Pediculus humanus.
Area of Science:
- Parasitology
- Genomics
- Immunology
Background:
- Human head and body lice (Pediculus humanus) are closely related ectoparasites.
- Only body lice transmit the bacterium Bartonella quintana.
- Differential vector competence between head and body lice presents a model for studying host-pathogen interactions.
Purpose of the Study:
- To investigate differences in Bartonella quintana proliferation in head versus body lice.
- To identify transcriptional changes in immune-related genes in lice infected with B. quintana.
- To understand the molecular basis for differential vector competence in Pediculus humanus.
Main Methods:
- In vitro louse-rearing system for controlled infection.
- Infection of head and body lice with blood containing B. quintana.
- RNA sequencing (RNAseq) and quantitative real-time PCR for gene expression analysis.
Main Results:
- Bartonella quintana proliferated rapidly in body lice, plateauing earlier in head lice.
- Significant differences in the expression of eight immune response genes were detected.
- Several differentially expressed genes, including Fibrinogen-like protein and Toll pathway components, were identified.
Conclusions:
- Body lice exhibit a different immune response to B. quintana compared to head lice.
- Immune gene expression, particularly related to the Toll pathway, likely contributes to differential vector competence.
- Findings suggest body lice mount an immune defense against B. quintana later in the infection cycle.
