Persistent, triple-virus co-infections in mosquito cells

Abstract

BackgroundIt is known that insects and crustaceans can carry simultaneous, active infections of two or more viruses without showing signs of disease, but it was not clear whether co-infecting viruses occupied the same cells or different cells in common target tissues. Our previous work showed that successive challenge of mosquito cell cultures followed by serial, split-passage resulted in stabilized cultures with 100% of the cells co-infected with Dengue virus (DEN) and an insect parvovirus (densovirus) (DNV). By addition of Japanese encephalitis virus (JE), we tested our hypothesis that stable, persistent, triple-virus co-infections could be obtained by the same process.ResultsUsing immunocytochemistry by confocal microscopy, we found that JE super-challenge of cells dually infected with DEN and DNV resulted in stable cultures without signs of cytopathology, and with 99% of the cells producing antigens of the 3 viruses. Location of antigens for all 3 viruses in the triple co-infections was dominant in the cell nuclei. Except for DNV, this differed from the distribution in cells persistently infected with the individual viruses or co-infected with DNV and DEN. The dependence of viral antigen distribution on single infection or co-infection status suggested that host cells underwent an adaptive process to accommodate 2 or more viruses.ConclusionsIndividual mosquito cells can accommodate at least 3 viruses simultaneously in an adaptive manner. The phenomenon provides an opportunity for genetic exchange between diverse viruses and it may have important medical and veterinary implications for arboviruses.

Novel Flaviviruses Detected in Different Species of Mosquitoes in Spain

“…quinquefasciatus (Pesko and Mores 2009). In contrast, persistent triple-virus coinfections (DEN-2, densovirus, and JEV) of mosquito cells (C6/36) had also been described (Kanthong et al 2010). Moreover, the replication of an insect-only flavivirus (CxFV strain Izabal) had no effect on the infection, transmission, or dissemination of WNV in C6/36 cells or in Cx.…”

Espirito Santo Virus: a New Birnavirus That Replicates in Insect Cells

“…Such contamination would be even more serious in the case of vaccine development, where an unknown and therefore undetected virus could affect the growth of the target virus. Furthermore, if these two viruses can coexist in the same cells for long periods of time, it may be an indication that there may be an opportunity for genetic exchange (27). This may have significant medical and epidemiological implications for arboviruses.…”

“…It was described in early studies that some Aedes albopictus cell lines developed in the late 1960s presented contamination with multiple viruses, such as parvovirus, togavirus, and orbivirus-like particles (26). These persistent and innocuous viral infections were described to be common in insects and crustaceans as single, dual, or multiple coinfections (27).…”

Viral Interference and Persistence in Mosquito-Borne Flaviviruses

“…The evaluation of viral interference during flavivirus infection is relatively easy to detect in cell lines, and it has primarily been examined in mosquito C6/36 cells (from Aedes albopictus ) [ 12 , 23 , 30 , 31 , 35 , 39 , 41 – 48 ], TRA-171 (from Toxorhynchites amboinensis ) [ 32 ], Sf9 (from Spodoptera frugiperda ) [ 49 ], C7-10, and U4.4 cells (from Aedes albopictus ) [ 29 , 35 ]. Homologous or heterotypic, but not heterologous, viral interference is frequently observed during superinfections ( Table 2 ), and this condition is particularly evident in persistently infected cells [ 23 , 31 , 32 , 44 , 49 ].…”