Evaluation of Measles Vaccine Virus as a Vector to Deliver Respiratory Syncytial Virus Fusion Protein or Epstein-Barr Virus Glycoprotein gp350

Mok, Hoyin; Cheng, Xing; Xu, Qi; Zengel, James R; Parhy, Bandita; Zhao, Jackie; Wang, C. Kathy; Jin, Hong

To confirm that these recombinant measles viruses expressed the desired antigens, the expression of the inserts in infected Vero cells was examined by Western blotting analysis. In addition to MV N protein that was detected in infected cell lysate (Fig. 1B) , RSV F and EBV gp350 were detected in the culture supernatant of the infected cells (Fig. 1B) , indicating the production of secreted form of RSV F and EBVgp350 proteins from virus infected cells. The observation of lower MV N expression in Vero cells infected with sF1 compared to other viruses may be attributed to the insertion of RSV F proximal to the MV N gene, which moved the MV N gene to the 2 nd position of the genome and reduced its mRNA transcript level. The relative expression of RSV F to MV N, however, was shown to be higher for sF1 compared to sF3. This is consistent with the observation that genes proximal to 3' end of the genome are transcribed more abundantly than those downstream and more RSV F was produced from sF1 than sF3 per virion. Viral replication efficiency of these recombinant viruses was assessed by growth kinetics in Vero cells. Both recombinant EZ (rEZ) and EZ vaccine viruses grew to a peak titer of 7.9 log 10 PFU/mL on day 5 (Fig. 3A) . rEZ with either RSVF (Fig. 2A) or EBVgp350 (Fig. 2B) inserts had comparable growth kinetics but slightly lower (between 0.1-0.7 log 10 lower) than rEZ. The peak titers between the viruses were not statistically different. sF3 had a faster growth kinetics and reached peak titer on day 3 instead of day 5. Therefore, insertion of RSV F or EBV gp350 into the genome of EZ did not significantly reduce viral growth in vitro.