Background: The impact of inactivated polio vaccines (IPVs) on intestinal mucosal immune responses to live poliovirus is poorly understood.
Methods: In a 2014 phase 2 clinical trial, Panamanian infants were immunized at 6, 10, and 14 weeks of age with bivalent oral polio vaccine (bOPV) and randomized to receive either a novel monovalent high-dose type 2-specific IPV (mIPV2HD) or a standard trivalent IPV at 14 weeks. Infants were challenged at 18 weeks with a monovalent type 2 oral polio vaccine (mOPV2). Infants' intestinal immune responses during the 3 weeks following challenge were investigated by measuring poliovirus type-specific neutralization and immunoglobulin (Ig) A, IgA1, IgA2, IgD, IgG, and IgM antibodies in stool samples.
Results: Despite mIPV2HD's 4-fold higher type 2 polio D-antigen content and heightened serum neutralization profile, mIPV2HD-immunized infants' intestinal immune responses to mOPV2 challenge were largely indistinguishable from those receiving standard IPV. Mucosal responses were tightly linked to evidence of active infection and, in the 79% of participants who shed virus, robust type 2-specific IgA responses and stool neutralization were observed by 2 weeks after challenge.
Conclusions: Enhancing IPV-induced serum neutralization does not substantively improve intestinal mucosal immune responses or limit viral shedding on mOPV2 challenge.
Clinical trials registration: NCT02111135.
Keywords: human challenge; inactivated vaccine; live oral vaccine; mucosal immunity; poliovirus.
© The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America.