Identification and characterization of alphavirus host factors determining human tissue tropism

• Applicant: Professorin Dr. Gisa Gerold
• Subject Area: Virology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452467953

Virus emergence and re-emergence is an increasing public health problem as globalization and climate change promote the spread of infectious disease. This is particularly true for mosquito-borne infections as mosquitoes continue to spread to new geographic regions. Alphaviruses such as Chikungunya virus (CHIKV) and Venezuelan equine encephalitis virus (VEEV) belong to the group of mosquito-borne viruses, which cause pathology in humans. The re-emerging CHIKV is causing long-lasting arthritis like symptoms, while VEEV infection leads to encephalitis. Why the two viruses from the same family cause pathologies in different tissues, i.e. joints versus central nervous system (CNS), is unclear to date. This gap of knowledge is reflected by the fact that few host factors for CHIKV and VEEV are known.Here we capitalize on our findings that the phosphatidylserine (PS) receptor T cell immunoglobulin mucin receptor 1 (TIM-1) and a tetraspanin are host factors for CHIKV. We hypothesize that (a) VEEV also hijacks PS receptors and tetraspanins to infect human cells, (b) TIM-1 and the tetraspanin interact with additional proteins to promote infection with CHIKV and possibly VEEV and (c) that a subset of these host factors contribute to tissue tropism of CHIKV and VEEV.To test our hypothesis we will initially use unbiased state of the art quantitative proteomics methods to identify entry factors and receptors of CHIKV and VEEV. Next we will screen PS receptors and all 33 human tetraspanins for their role in VEEV infection by RNA interference in human cells. TIM-1 and Tetraspanin associated proteins will be identified by proximity labeling in conjunction with high-resolution affinity enrichment mass spectrometry. Finally we will investigate the contribution of the identified host factors to tissue tropism of CHIKV and VEEV using proteomics, single cell sequencing and virological methods. Specifically, we will infect skin organotypic raft cultures and determine the predominantly infected cell type as well as expression levels of identified host factors in the susceptible versus refractory cells. Additionally we will integrate expression data from online repositories and measure proteomes of relevant cell types including fibroblasts and neuronal cells. Using feature selection approaches, we will identify host factors, which likely contribute to the distinct tissue tropism and pathologies caused by CHIKV and VEEV. These host factors will be systematically knocked out first in relevant cell types and then in mice to delineate the contribution to disease manifestation in vitro and in vivo.Taken together, this research program aims at providing mechanistic insight into the infection processes caused by two important human pathogens, CHIKV and VEEV. The results will help understand disease mechanisms and may ultimately reveal drug targets for therapeutic intervention with Chikungunya fever and Venezuelan equine encephalitis.

• DFG Programme: Research Grants
• International Connection: Austria, France
• Cooperation Partner: Professor Dr. Felix Rey