Transovarial transmission of a core virome in the Chagas disease vector Rhodnius prolixus

Abstract

Triatomine assassin bugs comprise hematophagous insect vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Although the microbiome of these species has been investigated to some extent, only one virus infecting Triatoma infestans has been identified to date. Here, we describe for the first time seven (+) single-strand RNA viruses (RpV1-7) infecting Rhodnius prolixus, a primary vector of Chagas disease in Central and South America. We show that the RpVs belong to the Iflaviridae, Permutotetraviridae and Solemoviridae and are vertically transmitted from the mothers to the progeny via transovarial transmission. Consistent with this, all the RpVs, except RpV2 that is related to the entomopathogenic Slow bee paralysis virus, established persistent infections in our R. prolixus colony. Furthermore, we show that R. prolixus ovaries express 22-nucleotide viral siRNAs (vsiRNAs), but not viral piRNAs, that originate from the processing of dsRNA intermediates during viral replication of the RpVs. Interestingly, the permutotetraviruses and sobemoviruses display shared pools of vsiRNAs that might provide the basis for a cross-immunity system. The vsiRNAs are maternally deposited in the eggs, where they likely contribute to reduce the viral load and protect the developing embryos. Our results unveil for the first time a complex core virome in R. prolixus and begin to shed light on the RNAi-based antiviral defenses in triatomines.