The determinants of Respiratory Syncytial Virus tropism
Summary
The primary hosts of RSV are humans. Other species that can be infected with hRSV are for example primates, rats, mice, and hamsters. Infection of these species is significantly less efficient in comparison to infection in human, and requires exposure to higher titers of virus. In agreement with this, cell lines with human origin seem to be more susceptible to RSV on average than other cell lines. Still, over the years many different types of cells have been used to culture RSV including cell line originating from other species. During a normal RSV infection in a human host, the virus is mainly limited to the ciliated epithelial cells in the respiratory tract. Other cells that can get infected in vivo are alveolar macrophages and virus can be isolated from PBMCs. On the other hand, in vitro studies have shown RSV to be well able to infect cell lines originating from several other tissues. Being able to infect so many different cell types in vitro could indicate that RSV is hardly specific in its cell tropism. Yet, over the last decades only a handful of studies have reported systemic spread of RSV to the heart, liver, or cerebrospinal fluid. Somehow, while RSV occasionally exits the pulmonary tract, and has the potential to infect many cell types in vitro, the virus hardly spreads to other compartments in the body at all in vivo. In this review we will discuss what is known about potential factors that could influence RSV host cell tropism.