Endogenous tick viruses and modulation of tick-borne pathogen growth.

Houssam Attoui,Lesley Bell-Sakyi

doi:10.3389/fcimb.2013.00025

Abstract

Ticks transmit a wide range of viral, bacterial and protozoan pathogens, many of which can establish persistent infections of lifelong duration in the vector tick and in some cases are transmitted transovarially to the next generation. In addition many ixodid and argasid tick cell lines and, by inference the parent ticks from which they were derived, harbor endogenous viruses (ETV) of which almost nothing is known. In general, low level persistent infections with viral pathogens (arboviruses) are not known to have a deleterious effect on tick survival and fitness, suggesting that they can strike a balance with the tick innate immune response. This tolerance of arbovirus infection may be modulated by the permanent presence of ETV in the host cell. In mosquito cells, temporary or permanent silencing of the genes of an endogenous virus by RNA interference can result in changes in replication rate of a co-infecting arbovirus. We propose that tick cell lines offer a useful model system for in vitro investigation of the modulatory effect of ETV on superinfecting pathogen survival and replication in ticks, using the molecular manipulation techniques applied to insect cells.

Highlights

Ticks are haematophagous parasitic arthropods that feed on a wide range of mammalian, avian, reptilian and amphibian hosts
We propose that tick cell lines offer a useful model system for in vitro investigation of the modulatory effect of endogenous tick viruses (ETV) on superinfecting pathogen survival and replication in ticks, using the molecular manipulation techniques applied to insect cells
St Croix River virus (SCRV) was passaged successfully alongside the bacterial pathogen Ehrlichia ruminantium from IDE8 (Bell-Sakyi et al, 2000) to ISE6 cells, passaged 5 weeks and several subcultures later from the ISE6 cells to the Rhipicephalus sanguineus cell line RSE8 (Kurtti et al, 1982), and virus was demonstrated in RSE8 cells 2 months later by PCR amplification of a portion of the SCRV segment 2 as described previously (Alberdi et al, 2012), indicating that SCRV can replicate in cells from at least three different tick species

Summary

Introduction

Ticks are haematophagous parasitic arthropods that feed on a wide range of mammalian, avian, reptilian and amphibian hosts. SCRV was passaged successfully alongside the bacterial pathogen Ehrlichia ruminantium from IDE8 (Bell-Sakyi et al, 2000) to ISE6 cells, passaged 5 weeks and several subcultures later from the ISE6 cells to the Rhipicephalus sanguineus cell line RSE8 (Kurtti et al, 1982), and virus was demonstrated in RSE8 cells 2 months later by PCR amplification of a portion of the SCRV segment 2 as described previously (Alberdi et al, 2012), indicating that SCRV can replicate in cells from at least three different tick species (authors’ unpublished results).

Results

Conclusion