Eilat virus induces both homologous and heterologous interference

Abstract

Most alphaviruses are mosquito-borne and exhibit a broad host range, infecting many different vertebrates including birds, rodents, equids, and humans. Occasionally, alphaviruses can spill over into the human population and cause disease characterized by debilitating arthralgia or fatal encephalitis. Recently, a unique alphavirus, Eilat virus (EILV), was described that readily infects mosquito but not vertebrate cell lines. Here, we investigated the ability of EILV to induce superinfection exclusion. Prior infection of C7/10 (Aedes albopictus) cells with EILV induced homologous and heterologous interference, reducing the virus titers of heterologous superinfecting viruses (SINV, VEEV, EEEV, WEEV, and CHIKV) by ~10-10,000 fold and delaying replication kinetics by 12-48h. Similar to in vitro infection, prior in vivo EILV infection of Aedes aegypti mosquitoes delayed dissemination of chikungunya virus for 3 days. This is the first evidence of heterologous interference induced by a mosquito-specific alphavirus in vitro and in vivo.

Keywords: Alphavirus; Eilat virus; Superinfection.

Figure 1

Experimental design to investigate homologous and heterologous interference by Eilat virus in vitro.

Figure 2

EILV-eRFP infection of C7/10 cells at an MOI of 10 PFU/cell. Phase contrast and fluorescent field micrographs were taken at 24 hpi.

Figure 3

EILV-induced homologous interference in C7/10 mosquito cells determined via eRFP expression. Phase contrast and fluorescent photographs were taken at 24 and 72 hrs post-superinfection.

Figure 4

EILV-induced heterologous interference in C7/10 cells, (A) SINV-eGFP and (B) VEEV-TC83-eGFP. Heterologous virus replication was measured via fluorescent microscopy. Phase contrast and fluorescent micrographs were taken at 24 and 72 hrs post-superinfection.

Figure 5

EILV-induced heterologous interference in C7/10 cells, (A) SINV and (B) VEEV-TC83. Heterologous virus titers were determined via plaque assay. Each time point represents average of triplicate infections. Bars indicate standard deviations for each time point. p-values <0.02 are indicated with *.

Figure 6

EILV-induced heterologous interference in C7/10 cells, (A) EEEV-NA, (B) VEEV-IC, (C) WEEV-McM, and (D) CHIKV-JKT. Heterologous virus titers were determined via plaque assay. Each time point represents average of triplicate infections. Bars indicate standard deviations for each time point. p-values <0.04 are indicated with *.

Figure 7

EILV-induced heterologous interference in A. aegypti mosquitoes. (A) Outline of experimental design; (B) EILV infection in mosquitoes 7 dpi and CHIKV blood meal titer, and; (C) CHIKV-SL07 superinfection of mosquitoes 3, 5, and 7 dpi. Bold indicates p-value = 0.003.