LB-12. Memory B cell responses following immunisation with polysaccharide and conjugate quadrivalent meningococcal ACYW-135 vaccines in healthy adult volunteers
Session: Poster Abstract Session: Late Breaker Posters
Saturday, October 22, 2011
Room: Poster Hall B1
Background

Neisseria meningitidis is a leading cause of meningitis and septicaemia. The development of quadrivalent protein-polysaccharide conjugate vaccines against serogroups A, C, W135 & Y offers the possibility of broader protection against the organism across all age groups.

Methods

We conducted an open-label randomised clinical trial in 150 healthy adult volunteers aged 18-70. Participants were randomised to receive either 2 doses of a conjugate quadrivalent ACWY vaccine 28 days apart (MenConj-MenConj),  or one dose of a polysaccharide quadrivalent ACWY vaccine followed by one dose of a conjugate quadrivalent ACWY vaccine 28 days later (MenPS-MenConj). Meningococcal polysaccharide-specific memory B cells were enumerated in peripheral blood at days 0, 28 and 56 by cultured EliSpot assay.

Results

Median memory cell numbers were similar at baseline in the two groups (medians of 1.0-3.0 cells per million cultured lymphocytes). By 56 days, median memory cell numbers were higher in the MenConj-MenConj group than in the MenPS-MenConj group  (7.0, 8.0, 3.0 and 3.0 cells per million cultured lymphocytes for serogroups A, C, W135 & Y respectively  vs. 4.5, 3.0, 2.0 and 2.0).

Conclusions

Two doses of conjugate vaccine generate larger memory responses than conjugate vaccine preceded by polysaccharide vaccine. This probably represents polysaccharide driven hypo-responsiveness, but might indicate differences in the magnitude or phenotype of  cells responding  to the two different vaccines.  Notably,  the serogroup A component of the vaccines appears to behave in the same way as  other polysaccharides despite prior data indicating that it  may act as a T-dependent antigen.


Subject Category: E. Innate and adaptive immunity to infections, including vaccine immunology

Maheshi N Ramasamy, MBBChir, MRCP1, Kathryn Haworth1, Jaclyn Bowman1, Elizabeth Clutterbuck, PhD1, Theresa Nickells, MBBS1, Matthew Snape, FRACP1, Tessa John1, Geraldine Blanchard-Rohner, MBBS, DPhil2 and Andrew Pollard, FRCPCH, PhD1, (1)Paediatrics, Oxford Vaccine Group, University of Oxford, Oxford, United Kingdom, (2)Paediatrics, University Hopsital of Geneva, Geneva, Switzerland

Disclosures:

M. N. Ramasamy, None

K. Haworth, None

J. Bowman, None

E. Clutterbuck, None

T. Nickells, None

M. Snape, Novartis Vaccines: Collaborator, Assistance from Novartis Vaccines to attend scientific meetings and has had travel and accommodation expenses paid by Novartis Vaccines while working in collaboration with Novartis Vaccines in Siena
GSK Pharmaceuticals: Collaborator, Assistance from GSK Pharmaceuticals to attend scientific meetings

T. John, None

G. Blanchard-Rohner, None

A. Pollard, Novartis Vaccines: Collaborator and acts as chief and principal investigator for clinical trials conducted on behalf of Oxford University, sponsored by vaccine manufacturers including Novartis Vaccines, but does not receive any personal payment from them, Industry-sourced honoraria for consultancy, lecturing, or writing and travel expenses and grants for educational activities are paid directly to an educational/administrative fund held by the Department of Paediatrics, University of Oxford.
GSK Pharmaceuticals: Collaborator and acts as chief and principal investigator for clinical trials conducted on behalf of Oxford University, sponsored by vaccine manufacturers including GSK pharmaceuticals, but does not receive any personal payment from them, Industry-sourced honoraria for consultancy, lecturing, or writing and travel expenses and grants for educational activities are paid directly to an educational/administrative fund held by the Department of Paediatrics, University of Oxford.

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