Culicoides-specific fitness increase of vesicular stomatitis virus in insect-to-insect infections

Authors: Drolet, Barbara; ROZO-LOPEZ, PAULA - University Of Tennessee

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Vesicular stomatitis (VS) is an arthropod-borne viral disease affecting livestock. In the United States, sporadic VS outbreaks result in significant disease and economic losses in western and southwestern states every 5-10 years. Culicoides biting midges act as biological vectors and significantly contribute to the geographic spread of outbreaks in the absence of animal movement. Additionally, surprisingly efficient venereal transmission of VSV occurs between Culicoides females and males which indicates a possible overwintering role for outbreaks that re-emerge a second year. This efficiency suggests that VSV within the midge may have increased fitness for replication in midge cells, facilitating midge-to-midge transmission. To determine if insect-derived VSV is better adapted for Culicoides infection than mammalian-derived VSV, three viral isolates of VSV propagated in pig or Culicoides cell lines were used to evaluate infection patterns of laboratory reared C. sonorensis midges. Both mammalian- and insect-derived VSV replicated well in midges when high titers were inoculated via intrathoracic injection. However, midge midguts exposed via ingestion to only a few virus particles derived from midge cells had significantly higher replication titers and subsequent dissemination rates than when exposed to pig-derived viruses. Genome sequencing of midge-derived and pig-derived viruses showed amino acid changes affecting polarity and/or hydrophobicity in four of the five VSV proteins. Our research suggests that VSV replication in Culicoides cells increases the viral fitness for efficient replication in midge vectors which may help explain the highly efficient venereal transmission seen in midges. This study highlights the importance of cell line specificity and limitations in investigating VSV-vector interactions and emphasizes the importance of Culicoides midges in VSV maintenance and transmission dynamics.