Properties of tick-borne Langat virus during growth in Ixodes scapularis ISE6 cells and host proteome change following infection

Tick-borne flaviviruses may cause hemorrhagic fever and encephalitis when transmitted to humans via a bite of an infected tick (Family Ixodidae). Langat virus (LGTV) provides a model for the study of tick-borne flaviviruses and is antigenically similar to the highly virulent Tick-Borne Encephalitis Virus (TBEV), which causes thousands of encephalitis cases per year. Significant effort has been directed at understanding flavivirus infection within mammalian systems; however, little is known about flavivirus infection within the tick vector. We have used tick-borne LGTV (TP21 strain) and an Ixodes scapularis ISE6 embryonic cell line to evaluate the tick proteome following virus infection. We characterized LGTV growth in ISE6 cells and established that the minimum MOI for maximal infection of ISE6 cells with LGTV was ~10-13. Mass spectroscopy (LC-MS/MS) was conducted to analyze the peptide/protein profile of ISE6 cells exposed to LGTV, non-infectious UV-inactivated LGTV, and uninfected (MOCK) cells. Data were processed using a Proteome Discovery Pipeline (PDP) to identify peptides that were significantly differentially-expressed following infection. Protein identification was performed by comparison of protein/peptide sequences to the Ixodes scapularis WIKEL strain IscaW1.1 predicted protein set available at VectorBase. Proteins were categorized to predicted cellular functions, including roles in environmental information processing, metabolism, genetic information processing, organismal systems, and cellular processes. We identified a significant number of differentially-expressed proteins that are involved in specific metabolism pathways that are being pursued as candidates for functional analyses. The long term goal of our research is to develop new protein targets for development of novel antiviral treatments.