Insect-Specific Virus Discovery: Significance for the Arbovirus Community

Abstract

Arthropod-borne viruses (arboviruses), especially those transmitted by mosquitoes, are a significant cause of morbidity and mortality in humans and animals worldwide. Recent discoveries indicate that mosquitoes are naturally infected with a wide range of other viruses, many within taxa occupied by arboviruses that are considered insect-specific. Over the past ten years there has been a dramatic increase in the literature describing novel insect-specific virus detection in mosquitoes, which has provided new insights about viral diversity and evolution, including that of arboviruses. It has also raised questions about what effects the mosquito virome has on arbovirus transmission. Additionally, the discovery of these new viruses has generated interest in their potential use as biological control agents as well as novel vaccine platforms. The arbovirus community will benefit from the growing database of knowledge concerning these newly described viral endosymbionts, as their impacts will likely be far reaching.

Keywords: arbovirus; evolution; insect-specific virus; vaccine; vector competence.

Figure 1

Timeline demonstrating dramatic increase in insect-specific virus discovery.

Figure 2

Flaviviruses: Maximum-likelihood analysis of select members of the genus flavivirus. Scale bars indicate amino acid substitutions/site. Branch labels indicate virus abbreviation. Additional virus isolate information is contained in a supplemental file.

Figure 3

Rhabdovirus: Maximum-likelihood (ML) analysis of rhabdovirus L protein sequences. Horizontal branch lengths are drawn to a scale of amino acid substitutions/site, and all bootstrap support values ≥85% are indicated by an asterisk. Cytorhabdovirus, novirhabdovirus and nucleorhabdovirus outgroup sequences were excluded from the tree as they were too divergent to establish a reliable rooting. The tree is therefore rooted arbitrarily on one of two basal clades (genera Almendravirus and Bahiavirus) that comprise viruses isolated from mosquitoes. Branch labels indicate virus abbreviation. Additional virus isolate information is contained in a supplemental file. (Adapted from [73]).

Figure 4

Mesoniviruses: Maximum-likelihood analysis of conserved protein domains of ORF1ab (3CLpro, RdRp, HEL1). Scale bars indicate amino acid substitutions/site. Branch labels indicate virus abbreviation/strain. Additional virus isolate information is contained in a supplemental file. (Adapted from [44]).

Figure 5

Negeviruses: Maximum likelihood analysis of select negeviruses. The region of the genome corresponds to the nt 4316–7309 (Negev E0239), which corresponds to the RNA-dependent RNA-polymerase of the genome. Branch labels indicate virus abbreviation/strain. Additional virus isolate information is contained in a supplemental file.

Figure 6

Togaviruses: Maximum likelihood analysis of select togaviruses. Phylogenetic tree based on nucleotide sequences of the alphavirus structural ORF. Branch labels indicate virus abbreviation/strain. Additional virus isolate information is contained in a supplemental file.

Figure 7

Mosquito vector competence for arboviruses can be affected by external and internal factors.