Nasal and Pharyngeal Mucosal Immunity to Poliovirus in Children Following Routine Immunization With Inactivated Polio Vaccine in the United States

Abstract

Background: Although polioviruses (PVs) replicate in lymphoid tissue of both the pharynx and ileum, research on polio vaccine-induced mucosal immunity has predominantly focused on intestinal neutralizing and binding antibody levels measured in stool.

Methods: To investigate the extent to which routine immunization with intramuscularly injected inactivated polio vaccine (IPV) may induce nasal and pharyngeal mucosal immunity, we measured PV type-specific neutralization and immunoglobulin (Ig) G, IgA, and IgM levels in nasal secretions, adenoid cell supernatants, and sera collected from 12 children, aged 2-5 years, undergoing planned adenoidectomies. All participants were routinely immunized with IPV and had no known contact with live PVs.

Results: PV-specific mucosal neutralization was detected in nasal and adenoid samples, mostly from children who had previously received 4 IPV doses. Across the 3 PV serotypes, both nasal (Spearman ρ ≥ 0.87, P ≤ .0003 for all) and adenoid (Spearman ρ ≥ 0.57, P ≤ .05 for all) neutralization titers correlated with serum neutralization titers. In this small study sample, there was insufficient evidence to determine which Ig isotype(s) was correlated with neutralization.

Conclusions: Our findings provide policy-relevant evidence that routine immunization with IPV may induce nasal and pharyngeal mucosal immunity. The observed correlations of nasal and pharyngeal mucosal neutralization with serum neutralization contrast with previous observations of distinct intestinal and serum responses to PV vaccines. Further research is warranted to determine which antibody isotype(s) correlate with polio vaccine-induced nasal and pharyngeal mucosal neutralizing activity and to understand the differences from intestinal mucosal immunity.

Keywords: mucosal immunity; nasal cavity; pharynx; poliovirus; vaccines.

Figure 1.

Correlations between poliovirus (PV) type-specific neutralization titers in nasal sponge samples, adenoid cell supernatants, and serum. Correlation coefficients are estimated from Spearman rank correlations. Undetectable log₂ neutralization titers were recorded as 1. Red circles, PV1; blue triangles, PV2; green squares, PV3.

Figure 2.

Distribution of poliovirus (PV) type-specific neutralization titers in nasal sponge samples, adenoid cell supernatants, and serum, stratified by the number of inactivated polio vaccine (IPV) doses previously received. Undetectable log₂ neutralization titers were recorded as 1. Red circles, PV1; blue triangles, PV2; green squares, PV3. Horizontal bars indicate the median levels. Children per dose of IPV received: 2 doses (n = 1), 3 doses (n = 4), 4 doses (n = 7).

Figure 3.

Correlations between poliovirus (PV) type-specific neutralization titers from nasal sponge samples, adenoid cell supernatants, and serum and the time since the last dose of inactivated polio vaccine (IPV) received (in days). Correlation coefficients are estimated from Spearman rank correlations. Undetectable log₂ neutralization titers were recorded as 1. Red circles, PV1, blue triangles, PV2, and green squares, PV3. Large shaded symbols, 4 doses of IPV; large open symbols, 3 doses of IPV; small open symbols, 2 doses of IPV.