Affiliation:
1. University of South Dakota, Sanford School of Medicine, Division of Basic Biomedical Sciences , 414 E. Clark Street, Vermillion, SD 57069 , USA
Abstract
ABSTRACT
Background
The human body louse (Pediculus humanus humanus) is a host-specific hematophagous ectoparasite that frequently infests populations experiencing a breakdown of hygienic conditions. Body lice are also vectors for several bacterial human pathogens, including Bartonella quintana, the agent of trench fever. However, the factors that influence immunity and infection in body lice are poorly understood. Human infection with B. quintana is associated with alcoholism and homelessness and can coincide with elevated circulating levels of the cytokine IL-10 and the inflammatory marker neopterin. Hematophagous arthropods are capable of responding physiologically and immunologically to a variety of biomolecules present in the blood of their hosts. Therefore, we sought to investigate whether ingestion of alcohol, its metabolic product acetaldehyde, IL-10 or neopterin could affect innate immunity and infection in the body louse.
Methods
Groups of lice were provisioned multiple blood meals containing physiological concentrations of alcohol, acetaldehyde, IL-10 or neopterin, and expression of six previously identified immunity-related genes (Defensin 1, Defensin 2, Prophenoloxidase, Hemocytin, Noduler and Dual Oxidase) was examined by qRT-PCR.
Results
Alcohol, acetaldehyde and IL-10 had no significant effects on gene expression relative to blood-fed controls while ingestion of neopterin significantly downregulated expression of Defensin 1 and Defensin 2. Nonetheless, ingestion of neopterin concurrent with B. quintana had no significant effect on the load of infection, indicating that neopterin-induced repression of Defensin expression is insufficient to reduce resistance to the pathogen.
Conclusions
Our findings demonstrate that the immune system of body lice can be affected by factors present in the blood of their human hosts and suggest potential conservation of the function of some immune molecules from human host to ectoparasite. Further, the discord between the effects of neopterin on immunity-related gene expression and B. quintana load highlights the complexity of the regulation of pathogen infection in the louse vector.
Funder
University of South Dakota Sanford School of Medicine
Publisher
Oxford University Press (OUP)
Subject
Infectious Diseases,Public Health, Environmental and Occupational Health,General Medicine,Parasitology
Reference39 articles.
1. Where are we with human lice? A review of the current state of knowledge;Amanzougaghene;Front Cell Infect Microbiol,2020
2. Human louse-transmitted infectious diseases;Badiaga;Clin Microbiol Infect,2012
3. Seroprevalence of Bartonella quintana infection: a systematic review;Mai;J Glob Infect Dis,2022
4. Risk factors for human lice and bartonellosis among the homeless, San Francisco, California, USA;Bonilla;Emerg Infect Dis,2014
5. Zoonotic and vector-borne infections among urban homeless and marginalized people in the United States and Europe, 1990-2014. Vector Borne Zoonotic Dis;Leibler,2016