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IgG1, IgG2 and IgM responses to two Haemophilus influenzae type b conjugate vaccines in young infants
D M Ambrosino1, S K Sood, M C Lee
1Laboratory of Infectious Diseases, Dana-Farber Cancer Institute, Boston, MA 02115.
Insights
Haemophilus influenzae type b (Hib) conjugate vaccines elicit different immune responses. PRP-OMPC provides an early antibody response, while HbOC requires more doses for a robust response, indicating varying vaccine efficacy.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Two conjugate vaccines for Haemophilus influenzae type b (Hib) exist: PRP-meningococcal outer membrane protein complex (PRP-OMPC) and oligosaccharide linked to variant diphtheria toxin (HbOC).
- These vaccines are licensed for infants starting at 2 months of age.
- Previous studies noted differences in serologic responses, with PRP-OMPC showing an early response and HbOC a higher response after a third dose.
Purpose of the Study:
- To characterize the distinct immune responses elicited by PRP-OMPC and HbOC Hib conjugate vaccines.
- To compare IgG1, IgG2, and IgM anti-Hib antibody concentrations after primary and booster doses of these vaccines.
Main Methods:
- Enzyme-linked immunosorbent assay (ELISA) was used to measure IgG1, IgG2, and IgM anti-Hib antibody concentrations.
- Infants received either PRP-OMPC or HbOC vaccine at 2, 4, and 6 months of age.
- A booster dose of PRP-OMPC was administered at 18 months to a subset of subjects.
Main Results:
- PRP-OMPC induced an IgM and IgG1 anti-Hib response after the initial dose at 2 months.
- HbOC showed increased IgG1 and IgM after two doses, with an IgG2 response occurring after the third dose at 6 months.
- Subjects previously primed with Hib vaccine had significantly higher IgG1 and IgG2 concentrations after an 18-month booster dose compared to those receiving only a primary dose.
Conclusions:
- Both Hib conjugate vaccines induce predominantly IgG1 anti-Hib antibody responses.
- The early immune response to PRP-OMPC at 2 months may be attributed to the adjuvant properties of the outer membrane protein complex (OMPC).
- Vaccine priming significantly enhances secondary antibody responses to Hib conjugate vaccines.
Abstract:
PRP-meningococcal outer membrane protein complex (PRP-OMPC) and oligosaccharide linked to variant diphtheria toxin (HbOC) Haemophilus influenzae type b (HIB) conjugate vaccines have both been licensed for United States infants at 2 months of age. Differences in serologic responses for these vaccines have been noted with PRP-OMPC producing an early response at 2 months of age and HbOC producing a higher response after a third dose at 6 months of age. To further characterize the nature of these distinct responses, we measured the IgG1, IgG2 and IgM anti-HIB concentrations by enzyme-linked immunosorbent assay after administration of both vaccines. PRP-OMPC produced an IgM and IgG1 anti-HIB response following the initial dose at 2 months of age. After two doses of HbOC an increase in IgG1 and IgM were noted and after a third dose at 6 months of age an IgG2 anti-HIB response occurred. In addition 33 study subjects were boosted with PRP-OMPC at age 18 months and compared with 34 subjects who received only a primary dose. The anti-HIB IgG1 and IgG2 concentrations following the booster dose were both significantly higher for the primed group (P = 0.0001 and P = 0.001, respectively). Both HIB conjugate vaccines produce predominantly IgG1 anti-HIB antibody responses. The early response to PRP-OMPC vaccine at 2 months of age may result from adjuvant characteristics of the OMPC.