Safety and immunogenicity of a parenterally administered rotavirus VP8 subunit vaccine in healthy adults

Background: The P2-VP8 subunit vaccine for the prevention of rotavirus gastroenteritis is comprised of a truncated VP8 subunit protein from the rotavirus Wa strain (G1[P8]) fused to the tetanus toxin P2 epitope, and adsorbed on aluminum hydroxide for intramuscular administration. Methods: Three groups of 16 adults were randomized to receive three injections of P2-VP8 (12) or placebo (4) at doses of 10, 30 or 60. μg of vaccine. IgG and IgA antibodies to P2-VP8 were assessed by ELISA in serum and lymphocyte supernatant (ALS). Serum samples were tested for neutralizing antibodies to homologous and heterologous strains of rotavirus. Results: The vaccine was well-tolerated. All vaccine recipients demonstrated significant IgA responses and all but one demonstrated IgG responses; in the 60 μg cohort, geometric mean titers (GMTs) rose 70- and 80-fold for IgA and IgG, respectively. Homologous neutralizing antibody responses were observed in about half of participants in all three dose cohorts; in the 60 μg cohort, GMTs against Wa rose from 128 to 992. Neutralizing antibody responses were robust to P[8] strains, moderate to P[4] strains and negligible to P[6] strains. ALS IgA responses were dose dependent. Conclusions: The P2-VP8 subunit vaccine was well tolerated and evoked promising immune responses. Clinical trials registration: NCT01764256.