Objective: This study was performed to evaluate the avidity maturation and IgG isotype distribution of antibodies after vaccination with a meningococcal B OMV vaccine using two different vaccination schedules and adjuvants. In earlier studies using Hib and Men C conjugate vaccines it was shown that the presence of high avidity antibodies can be considered as a surrogate marker for induction of memory. Furthermore, isotype of IgG antibodies is important regarding to the difference in functional activity of these antibodies, such as complement binding.
Methods: Pre and post sera from a clinical phase II trial were analysed for antibody avidity and IgG isotype distribution using ELISA methods.
In this trial 134 healthy toddlers (2-3 years of age) were immunised with a monovalent meningococcal B OMV (7b,4) vaccine absorbed with AlPO4 or Al(OH)3. Vaccinations were given 3 times with an interval of 3-6 weeks or twice with an interval of 6-10 weeks. A booster was given after 20-40 weeks.
Results: Antibody avidity increased significantly after the booster vaccination. No differences in avidity were seen between the two vaccination schedules and adjuvants. After vaccination, IgG1was the predominant IgG isotype, followed by IgG3. No IgG2 or IgG4 could be detected.
Conlusions: Antibody maturation occurs after vaccination with a monovalent meningococcal B OMV vaccine, especially after boostering. This suggests that
immunological memory has been generated.
Vaccination mainly induced IgG1 and IgG3 isotypes, which are considered to be most important for protection of disease.