Abstract
Half of the human population is at risk of infection by an arthropod-borne virus. Many of these arboviruses, such as West Nile, dengue, and Zika viruses, infect humans by way of a bite from an infected mosquito. This infectious inoculum is insect cell-derived giving the virus particles distinct qualities not present in secondary infectious virus particles produced by infected vertebrate host cells. The insect cell-derived particles differ in the glycosylation of virus structural proteins and the lipid content of the envelope, as well as their induction of cytokines. Thus, in order to accurately mimic the inoculum delivered by arthropods, arboviruses should be derived from arthropod cells. Previous studies have packaged replicon genome in mammalian cells to produce replicon particles, which undergo only one round of infection, but no studies exist packaging replicon particles in mosquito cells. Here we optimized the packaging of West Nile virus replicon genome in mosquito cells and produced replicon particles at high concentration, allowing us to mimic mosquito cell-derived viral inoculum. These particles were mature with similar genome equivalents-to-infectious units as full-length West Nile virus. We then compared the mosquito cell-derived particles to mammalian cell-derived particles in mice. Both replicon particles infected skin at the inoculation site and the draining lymph node by 3 hours post-inoculation. The mammalian cell-derived replicon particles spread from the site of inoculation to the spleen and contralateral lymph nodes significantly more than the particles derived from mosquito cells. This in vivo difference in spread of West Nile replicons in the inoculum demonstrates the importance of using arthropod cell-derived particles to model early events in arboviral infection and highlights the value of these novel arthropod cell-derived replicon particles for studying the earliest virus-host interactions for arboviruses.
Highlights
Arthropod-borne viruses are transmitted between arthropod vectors, such as ticks and mosquitos, and their vertebrate hosts
We found that West Nile replicon particles derived from mosquito cells were significantly reduced in spread to distant sites compared to those derived from mammalian cells
Our goal was to produce West Nile viruses (WNV) replicon particles (RPs) packaged in mosquito cells to better mimic mosquito transmission for in vivo studies
Summary
Arthropod-borne viruses are transmitted between arthropod vectors, such as ticks and mosquitos, and their vertebrate hosts. Mosquito-borne flaviviruses, such as dengue, Zika, and West Nile viruses (WNV), are responsible for a variety of debilitating pathologies, including hemorrhagic fever, encephalitis, flaccid paralysis, and microcephaly. Human cases of WNV have been documented on all continents except Antarctica making it the most widespread viral cause of encephalitis (reviewed in [2]) and an important pathogen for study. Three structural proteins make up the virion: capsid (C), premembrane/membrane (prM/M), and envelope (E). C protein packages the genome into a nucleocapsid, which buds into the ER membrane containing E and prM and forms an immature particle (reviewed in [3]). Mature particles are formed when prM is cleaved by host cell proteases in the Golgi, resulting in M and E in the viral envelope and structural rearrangement of the particle, prior to release from the host cell [4]
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