Figure 1.
Intravenously injected virus does not exist as cell-free particles. We injected 5 × 108 pfu of VSV intravenously into C57Bl/6 immunocompetent mice. At 2, 30, and 60 minutes after injection, we sampled either cell-free plasma or the packed cell fraction from harvested blood for infectious virus. Within 2 minutes, most of the detectable virus was in the packed cell fraction. By 30 minutes postinjection, only virus associated with cells was detectable. These data suggest that viral particles associate rapidly with cells in the circulation which subsequently either neutralize the virus or, in some cases, act as carriers for distribution around the body.