Dynamic gene expression in salivary glands of the cat flea during Rickettsia felis infection

Abstract

The cat flea, Ctenocephalides felis, is an arthropod vector capable of transmitting several human pathogens including Rickettsia species. Earlier studies identified Rickettsia felis in the salivary glands of the cat flea and transmission of rickettsiae during arthropod feeding. The saliva of hematophagous insects contains multiple biomolecules with anticlotting, vasodilatory, and immunomodulatory activities. Notably, the exact role of salivary factors in the molecular interaction between flea-borne rickettsiae and their insect host is still largely unknown. To determine if R. felis modulates gene expression in the cat flea salivary gland, cat fleas were infected with R. felis and transcription patterns of selected salivary gland-derived factors, including antimicrobial peptides and flea-specific antigens, were assessed. Salivary glands were microdissected from infected and control cat fleas at different time points after exposure and total RNA was extracted and subjected to reverse-transcriptase quantitative PCR for gene expression analysis. During the experimental 10 day feeding period, a dynamic change in gene expression of immunity-related transcripts and salivary antigens between the two experimental groups was detected. The data indicated that defensin-2 (Cf-726), glycine-rich antimicrobial peptide (Cf-83), salivary antigens (Cf-169 and Cf-65), and deorphanized peptide (Cf-75) are flea-derived factors responsive to rickettsial infection.

Unpacking the intricacies of Rickettsia–vector interactions

“…However, a sialotranscriptome of the cat flea revealed several flea molecules that may be influenced by rickettsial infection, including AMPs and targets of the Toll or IMD pathways [78]. Furthermore, the synergistic or regulatory activities of flea salivary gland secreted molecules during rickettsial infection and transmission to vertebrate hosts are in the early stages of characterization [79]. With both R. typhi and R. felis detected within salivary glands of infected fleas, further investigation is warranted to determine the impact of flea saliva on transmission.…”

Using Proteomic Approaches to Unravel the Response of Ctenocephalides felis felis to Blood Feeding and Infection With Bartonella henselae

“…The goal of this study was to identify and characterize the proteomic response of the cat flea, C. felis, to feeding of uninfected cat blood and blood from cats experimentally instance, the responses of X. cheopis' digestive tract to infection by Y. pestis (Bland et al, 2020), C. felis' midgut to Rickettsia felis (Dreher-Lesnick et al, 2010), and C. felis' salivary glands to R. typhi (Danchenko et al, 2021) have been previously reported. Herein, we used proteomic approaches to investigate if: i.)…”

“…A vaccine targeting both flea fitness and pathogen competence is an attractive choice requiring the identification of flea proteins/metabolites with a dual effect. Even though recent developments in vector and pathogen omics have advanced the understanding of the genetic factors and molecular pathways involved at the tickpathogen interface, leading to discovery of candidate protective antigens (de la Fuente et al, 2007a;de la Fuente et al, 2007b), only a few studies have focused on the interaction between fleas and flea-borne pathogens (Dreher-Lesnick et al, 2010;Brown, 2019;Bland et al, 2020;Danchenko et al, 2021;Laukaitis and Macaluso, 2021).…”

The role of cofeeding arthropods in the transmission of Rickettsia felis

“…Newly emerged cat fleas were obtained from Elward II (Soquel, CA) and maintained on defibrinated bovine blood (HemoStat Laboratories, Dixon, CA) within an artificial dog feeding unit [23]. Prior to use in bioassays, genomic DNA (gDNA) was extracted from a portion of fleas and confirmed Rickettsia-negative by quantitative real-time PCR (qPCR) [24,25]. In order to generate R. felis-infected donor cat fleas, newly emerged cat fleas were pre-fed HI bovine blood for 24 hrs, starved for 5-6 hrs, then exposed to the R. felis-infected bloodmeal (3 × 10 10 rickettsiae/700 μl) for 24 hrs [8].…”

“…Assessment of rickettsial infection by qPCR was performed with a LightCycler 480 Real-Time PCR system (Roche, Indianapolis, IN). The plasmid pCR4-TOPO-RfelB was used as a standard template to create serial 10-fold dilutions and matched with RfelB primers and probe as previously described [24,25]. For An.…”