Oncolytic measles virus (OMV) is a promising antitumor agent.However,the presence of anti-measles neutralizing antibodies (NAbs) against the hemagglutinin (H) protein of OMV is a major barrier to the therapeutic application of OMV in clinical practice.In order to overcome this challenge,specific types of cells have been used as carriers for OMV.Differential loading strategies appear to result in different therapeutic outcomes;despite this,only few studies have reported practical ex vivo loading strategies required for effective treatment.To this end,we systematically evaluated the antitumor efficacy of OMV using different loading strategies;this involved varying the in vitro loading duration and loading dose of OMV.We found that improved oncolysis of carrier cells was achieved by a prolonged loading duration in the absence of NAbs.However,the enhanced oncolytic effect was abrogated in the presence of NAbs.Further,we found that the expression of H protein on the surface of carrier cells was predominantly determined by the loading duration rather than the loading dose.Finally,we showed that NAbs blocked viral transfer by targeting H protein prior to the occurrence of cell-to-cell interactions.Our results provide comprehensive information on the determinants of an effective loading strategy for carrier cell-based virotherapy;these results may be useful for guiding the application of OMV as an antitumor agent in clinical practice.