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Background: Assessing immune response after rotavirus vaccination consists in measuring serum or plasma IgA and IgG antibodies, but these assays provide very little information about the mucosal immune response. Thus the development of assays for detection of mucosal immune response following rotavirus vaccination is essential. We evaluate to assess circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immune responses to rotavirus vaccine. Methods: 372 subjects, aged 6 weeks, were enrolled in the study. All the subjects were assigned to receive two doses of Rotarix® vaccine. Using a micro-modified whole blood-based ELISPOT assay, circulating rotavirus type-specific IgA- and IgG-ASCs, including gut homing β7+ ASCs, were enumerated on week 6 before the first dose of Rotarix vaccination at 7 weeks of age and week 18 after the second vaccination at 17 weeks of age. Plasma samples collected before vaccination, and after two doses of Rotarix® vaccination were tested for plasma rotavirus IgA titers. Results: Two doses of Rotarix® provided to induce sero-protective titer of ≥ 20 Units in 35% of subjects. Total blood IgA- ASC responses were detected in 26.4% of subjects who were non-responder before vaccination. Among responders, 47% of the subjects also have sero-protective plasma IgA titers. Discussion: Our results suggest that virus-specific blood gut homing ASCs were detected and provide insight into mucosal immune response after rotavirus vaccination. Further studies are needed to evaluate the duration of such immune responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the rotavirus immunization program.

Background: The final endgame strategy of global polio eradication initiative includes switching from trivalent oral poliovirus vaccines (tOPV) to bivalent oral polio vaccine (bOPV), and introduction of inactivated poliovirus vaccine (IPV). This study compares IPV with tOPV week 39 boost in Indian infants. Methods: Starting 28 March 2012, we enrolled 372 Indian infant-mother pairs from Kolkata, India in an open-label, block-randomized, controlled trial comparing a 39 week tOPV to an IPV boost among infants immunized with three doses of tOPV. The primary outcome was mucosal immunity to poliovirus as measured by fecal polio virus shedding after OPV challenge. The secondary outcome was humoral response as defined by >1:8 titers for neutralizing antibodies at week 40. Seroconversion was measured by change in level of antibody titers from week 18 to week 40. The analyses were performed by both intention-to-treat (ITT) and per-protocol (PP) comparing the occurrences of outcomes between the arms of the study. Findings: Both the study arms provided equivalent mucosal immunity at 52 weeks with a total shedding prevalence of 28%. Vaccination with IPV resulted in significantly higher seroconversion rates for Polio type 2 (p = 0.03) and Polio type 3 (p < 0.01). Conclusions: This study indicates that an IPV boost at week 39 is equivalent to tOPV in intestinal immunity, and provides higher seroconversion compared to tOPV. The major limitation of the study was the additional OPV doses receive by infants during pulse polio immunization resulted in additional mucosal boosting, diminishing the impact of IPV or tOPV boost at week 39. However, IPV for OPV boost should prove to be a step forward in the global polio eradication initiative to reduce the problem of circulating vaccine-derived poliovirus (cVDPV).