Infection of Mosquito Cells (C6/36) by Dengue-2 Virus Interferes with Subsequent Infection by Yellow Fever Virus

Abstract

Dengue is one of the most important diseases caused by arboviruses in the world. Yellow fever is another arthropod-borne disease of great importance to public health that is endemic to tropical regions of Africa and the Americas. Both yellow fever and dengue viruses are flaviviruses transmitted by Aedes aegypti mosquitoes, and then, it is reasonable to consider that in a given moment, mosquito cells could be coinfected by both viruses. Therefore, we decided to evaluate if sequential infections of dengue and yellow fever viruses (and vice-versa) in mosquito cells could affect the virus replication patterns. Using immunofluorescence and real-time PCR-based replication assays in Aedes albopictus C6/36 cells with single or sequential infections with both viruses, we demonstrated the occurrence of viral interference, also called superinfection exclusion, between these two viruses. Our results show that this interference pattern is particularly evident when cells were first infected with dengue virus and subsequently with yellow fever virus (YFV). Reduction in dengue virus replication, although to a lower extent, was also observed when C6/36 cells were initially infected with YFV followed by dengue virus infection. Although the importance that these findings have on nature is unknown, this study provides evidence, at the cellular level, of the occurrence of replication interference between dengue and yellow fever viruses and raises the question if superinfection exclusion could be a possible explanation, at least partially, for the reported lack of urban yellow fever occurrence in regions where a high level of dengue transmission occurs.

Impact of simultaneous exposure to arboviruses on infection and transmission by Aedes aegypti mosquitoes

“…Alternatively (or possibly in addition), it may be that only a small number of cells are initially infected in the midgut35, rendering enhancement and/or superinfection exclusion during coinfection largely irrelevant. Furthermore, it remains unclear whether superinfection exclusion even occurs between these viruses since the literature is somewhat contradictory262728. In general, our results allow us to conclude that in most cases arbovirus infection of mosquito midguts is not altered by the presence of coinfecting arboviruses.…”

“…In contrast, CHIKV replicates and disseminates faster than the two flaviviruses22232425 and may thus directly outcompete DENV and ZIKV in vivo . Similarly, exposing mosquitoes to two closely related flaviviruses, DENV and ZIKV, could directly impact virus infection, dissemination and transmission through superinfection exclusion262728 or a similar mechanism. We thus hypothesized that infection of mosquitoes with multiple arboviruses would alter the vector competence for at least one of them.…”

What Does the Future Hold for Yellow Fever Virus? (I)

“…One or more of these viruses could potentially interfere with the spread of YFV through competition in coinfected mosquitoes and/or primates. They might also provide a cross-reactive immune background that reduces infection levels [3,48,63,89,129,174,[178][179][180]. Competitive exclusion between YFV and other flaviviruses could be tested experimentally in mosquitoes, and in mammalian hosts (rodents, NHPs).…”

“…This phenomenon could take place into the host (cross-protection) and/or the vector (outcompetition). However, both field and experimental data remain too sparse and sometimes diverge [129,130] and more investigations are definitely needed so that these assumptions can be discussed on a solid basis. Overall, the risk of urban spread of YFV due to the presence of dense populations of Aaa mosquitoes in numerous urban centres where most of the inhabitants are nonimmune remains a concern in multiple countries in South America [62, [131][132][133][134].…”

“… the relatively low incidence of yellow fever on the east coast of Africa when compared with central and west Africa [76,175]  the low vector competence of East African and also Asian populations of Ae aegypti [124, 174, 176, 177]  the presence of other flaviviruses, such as dengue virus and viruses in the Japanese encephalitis virus complex which might out-compete YFV or provide an immune background in Asian populations [3,48,63,89,129,174,[178][179][180]]  genetic resistance in Asian populations [2] It seems, from the plethora of factors cited above in the many publications, that the explanation for the absence of YFV in Asia is likely to be multifactorial. The nature of the interactions between YFV and its primary vector, domestic Ae aegypti, is probably the most important individual determinant of this distinctly different geographic distribution when compared with dengue, Zika, and chikungunya virus all of which share the same primary vector.…”