Humoral responses in Rhodnius prolixus: bacterial feeding induces differential patterns of antibacterial activity and enhances mRNA levels of antimicrobial peptides in the midgut.

Cecilia Stahl Vieira,Peter J Waniek,Patrícia Azambuja,Norman A Ratcliffe,Cícero B Mello,Débora P Mattos,Daniele P Castro,Eloi S Garcia

doi:10.1186/1756-3305-7-232

Abstract

BackgroundThe triatomine, Rhodnius prolixus, is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. It has a strictly blood-sucking habit in all life stages, ingesting large amounts of blood from vertebrate hosts from which it can acquire pathogenic microorganisms. In this context, the production of antimicrobial peptides (AMPs) in the midgut of the insect is vital to control possible infection, and to maintain the microbiota already present in the digestive tract.MethodsIn the present work, we studied the antimicrobial activity of the Rhodnius prolixus midgut in vitro against the Gram-negative and Gram-positive bacteria Escherichia coli and Staphylococcus aureus, respectively. We also analysed the abundance of mRNAs encoding for defensins, prolixicin and lysozymes in the midgut of insects orally infected by these bacteria at 1 and 7 days after feeding.ResultsOur results showed that the anterior midgut contents contain a higher inducible antibacterial activity than those of the posterior midgut. We observed that the main AMP encoding mRNAs in the anterior midgut, 7 days after a blood meal, were for lysozyme A, B, defensin C and prolixicin while in the posterior midgut lysozyme B and prolixicin transcripts predominated.ConclusionOur findings suggest that R. prolixus modulates AMP gene expression upon ingestion of bacteria with patterns that are distinct and dependent upon the species of bacteria responsible for infection.

Highlights

The triatomine, Rhodnius prolixus, is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease in Latin America
Results with lysozyme at 1 days after feeding (DAF) showed that lysozyme A (LysA) was significantly upregulated in the anterior midgut after S. aureus infection (p < 0.01) while lysozyme B (LysB) was significantly downregulated after E. coli infection (Figure 7A and 7C; p < 0.01)
Phylogenetic analyses indicate that R. prolixus LysA groups with lysozymes that play a digestive role in other triatomine bugs [31,54,55], our results showed that LysA was strongly induced after S. aureus feeding and it was possible to detect a slight increase of LysA after infection with E. coli, indicating an immunological role for this lysozyme

Summary

Introduction

The triatomine, Rhodnius prolixus, is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease in Latin America It has a strictly blood-sucking habit in all life stages, ingesting large amounts of blood from vertebrate hosts from which it can acquire pathogenic microorganisms. In this context, the production of antimicrobial peptides (AMPs) in the midgut of the insect is vital to control possible infection, and to maintain the microbiota already present in the digestive tract. The immune system in insects, unlike vertebrates, lacks the classical response to pathogens mediated by memory cells and immunoglobulin, but relies solely on an extremely efficient innate immune response [4]. AMP production is triggered by activation of different immune signalling pathways including Toll, Imd and Jak/STAT after recognition of non-self molecules known as the pathogen associated molecular patterns (PAMPs) [5,11]

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