Interestingly, ferrets that received supplemented split BIIB057 with M2e5x VLP induced significant levels of vaccine virus specific antibody responses even after primary immunization, reaching HI titers of 40 to 80 (GMT = 53, day 21, Split+M2e5x, Fig. 2B). After two immunizations, the M2e5x VLP supplemented ferret group reached high levels of HI titers, ranged from 160 to 320 (GMT = 184 day 35, Fig. 2B). These results suggest that M2e5x VLPs appear to act as an adjuvant role in increasing HI titers of vaccine, reaching higher levels at early time points. The adjuvant effect of the M2e5x VLP was balanced by repeated administration of the split vaccine alone (Fig. 1). As HA neutralizing antibody is the best established correlate of protection for influenza, animals receiving split vaccine only were immunized until CA/08 HI titers reached HI levels comparable to those in animals receiving SplitM2e5x (Fig. 2B). Prior to challenge, ferrets in both the split and Split+M2e5x groups demonstrated CA/08 HI titers ranging from 80 to 320 with GMTs of 139 and 160, respectively, which is expected to confer protection against homologous virus.
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