Abstract
BackgroundThe genus Flavivirus currently consists of approximately 80 single-strand positive-sense RNA viruses. These replicate in a range of hosts including myriad vertebrate, insect, and tick species. As a consequence of this broad host range, the majority of flaviviruses can be propagated in most vertebrate and insect cell cultures. This ability to infect arthropods and vertebrates usually is essential for maintenance of these viruses in nature. But recently, there has been the discovery of a number of flaviviruses that infect mosquitoes but not vertebrates. It remains largely unknown why certain flaviviruses infect vertebrates and mosquitoes while others infect mosquitoes or vertebrates exclusively.MethodsHere, we initiated in vitro host range studies of Rabensburg virus (RABV), an intermediate between the mosquito-specific and horizontally transmitted flaviviruses, to provide information on the factor(s) that underlie the varying host range of flaviviruses. RABV is an intermediate between the mosquito-specific and horizontally transmitted flaviviruses because it does not infect mammalian or avian cell cultures, house sparrows, or chickens, but it does share genetic characteristics with the Japanese Encephalitis serogroup of flaviviruses.ResultsIn vitro growth kinetic assays revealed the complete abrogation of RABV growth on Vero and E6 cells incubated at temperatures 35°C and higher, but surprisingly RABV infected, replicated efficiently, and displayed overt cytopathic effects (CPE) on Vero and E6 cell cultures incubated below 35°C. In contrast, RABV was fully viable, replicated efficiently, and displayed overt CPE on C6/36 cells incubated at 28°C or 37°C, thus implicating temperature as an important factor limiting the host range of RABV.ConclusionsThese data are critical for further study to more fully identify the determinants that mediate the evolution of biological transmission among flaviviruses. It also will be useful for studies that look to provide a comprehensive molecular definition of flavivirus-host cell interactions. And it will provide a cadre of information to design wet lab experiments to investigate the genetic changes that facilitate host switching, which may lead to new vertebrate pathogens or transmission pathways.
Highlights
The genus Flavivirus currently consists of approximately 80 single-strand positive-sense RNA viruses
We initiated in vitro host range studies of RABV97-103 and the most recent isolate, Rabensburg virus (RABV) strain 06–222 [16], to provide information on the factor(s) that underlie the varying host range of flaviviruses. It remains largely unknown which viral determinants are responsible for host cell tropism and vector specificity, i.e., why do certain flaviviruses infect mosquitoes and vertebrates and why are other flaviviruses not able to infect vertebrates or vertebrates exclusively? Here, we demonstrate that the factor limiting the ability of RABV to infect mammalian cell culture is temperature, and to our knowledge, this is the first demonstration of a member of the genus Flavivirus exhibiting a narrow host range as a result of temperature sensitivity
Influence of temperature on virus growth on mammalian cells Previously, we reported that RABV97-103 was unable to infect mammalian or avian cell cultures, house sparrows or chickens, but the virus efficiently infected mosquito cells [14], i.e., it displayed characteristics of a hostrestricted flavivirus
Summary
The genus Flavivirus currently consists of approximately 80 single-strand positive-sense RNA viruses. These replicate in a range of hosts including myriad vertebrate, insect, and tick species. As a consequence of this broad host range, the majority of flaviviruses can be propagated in most vertebrate and insect cell cultures. This ability to infect arthropods and vertebrates usually is essential for maintenance of these viruses in nature. The genus Flavivirus (family Flaviviridae) presently comprises approximately 80 single-strand positive-sense RNA viruses, and consists of four groups, each with a distinct host range. Our understanding of the significance of the ‘insect-specific’ flaviviruses and the implications for the evolution and transmission of viruses belonging to the genus Flavivirus currently is limited
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