Dados do Trabalho

Título

An immunogenic cysteine-rich protein that regulates Rhipicephalus microplus tick's microbiota

Introdução

Rhipicephalus microplus tick causes severe infestations which can lead to significative harm to livestock animals, resulting in expressive economic losses in Brazil and other tropical and subtropical countries. The most common tick control strategies consist in the usage of chemical acaricides, which present several disadvantages, including the selection of resistant tick populations. Therefore, alternative control methods have been studied and employed along the last decades, and among the most studied approaches, are anti-tick vaccines, which presented satisfactory results against R. microplus parasitism in different countries. Nevertheless, until the present moment there is not efficient vaccine for Brazilian R. microplus populations, which means that new antigens might be evaluated. Thus, at the present work a high-throughput screening of immunogenic salivary proteins from R. microplus was carried out through the phage display technique, revealing several potential antigens for vaccinal formulations. Among them, a cysteine-rich protein containing a trypsin inhibitor-like (TIL) domain, named here as RmTIL. Proteins in TIL family were previously characterized as putative serine protease inhibitors and antimicrobials, playing an important role in tick feeding process and embryo protection. 

Objetivo (s)

The objective of the present work is to elucidate the role of RmTIL in tick physiology and microbiota regulation.

Material e Métodos

RmTIL gene expression in tick organs was evaluated, and the recombinant protein, produced in HEK293 mammalian cells, was tested as a serine protease inhibitor. RmTIL-encoding gene was silenced by RNAi in engorged females and their reproductive parameters were evaluated. Additionally, bacterial growth in knock-down females were also accessed, as well as the microbiome of eggs laid by RNAi silenced females, investigated through 16S rRNA metatranscriptomic analysis. 

Resultados e Conclusão

The present study revealed that the RmTIL-encoding gene is expressed in salivary glands and ovary of engorged females. Moreover, the expression was upregulated in ovary of females experimentally infected by gram-positive Staphylococcus aureus bacteria. RmTIL did not present significant enzymatic inhibition activity. After gene silencing by RNAi in engorged female ticks, bacterial 16S gene expression was increased in ovary. Additionally, the produced eggs showed a decrease in viability and presented an altered microbiota composition, suggesting that RmTIL could play an antimicrobial role.

Palavras Chave

Rhipicephalus microplus; cysteine-rich; Trypsin inhibitor-like; antimicrobial activity.