The importance of in vivo studies is also supported by a recent report that showed that a gL-null RRV mutant still established persistent infection in the B cell compartment upon intravenous inoculation, while infection of B cells in vitro was drastically reduced [24], a finding that could be explained by the gL-independent usage of Plxdc1/2 for B cell infection in vivo. The gene discussed is PLXDC1; the disease is infection.