Increasing the efficiency of virus infectivity assays: small inoculum volumes are as effective as centrifugal enhancement.

Improving the virus particle:infectious unit ratio is a continuing goal for animal virologists. It is demonstrated for an influenza A virus that decreasing the size of the inoculum volume to 10 microl per well of a 96-well plate was as effective as using centrifugal force with inoculum up to 250 microl. Both achieved a 7.5-fold increase in infectivity in monolayers of MDCK cells compared with standard conditions. The underlying principle of both methods is to bring virus particles into close contact with cell receptors.