Analysis of human serum immunoglobulin G against O-acetyl-positive and O-acetyl-negative serogroup W135 meningococcal capsular polysaccharide.

The capsular polysaccharide of Neisseria meningitidis serogroup W135 is expressed in both O-acetyl-positive (OA+) and O-acetyl-negative (OA-) forms. This study investigates the impact of OA status (OA+ versus OA-) on serological measurements of anti-W135 immunoglobulin G (IgG) antibodies in immunized adults. W135-specific serum antibody assignments were made for 28 postimmunization sera from adults by enzyme-linked immunosorbent assay using the meningococcal standard reference serum CDC1992.

Genetics of capsule O-acetylation in serogroup C, W-135 and Y meningococci.

Capsular polysaccharides of serogroup C, W-135 and Y meningococci were previously reported to be O-acetylated at the sialic acid residues. There is evidence that O-acetylation affects the immunogenicity of polysaccharide vaccines. We identified genes indispensable for O-acetylation of serogroup C, W-135 and Y meningococci downstream of the capsule synthesis genes siaA-D.

Avidity maturation following vaccination with a meningococcal recombinant hexavalent PorA OMV vaccine in UK infants.

To date, there are no data assessing the utility of avidity indices as a surrogate marker for the induction of immunological memory following meningococcal serogroup B outer membrane vesicle (OMV) vaccination. We studied infants who had been immunized with three doses of a recombinant hexavalent PorA OMV vaccine at ages 2-4 months, together with a fourth dose at age 12-18 months. A control group had received a single dose of the same vaccine at age 12-18 months.

O-Acetylation status of the capsular polysaccharides of serogroup Y and W135 meningococci isolated in the UK.

At a time when tetravalent conjugate vaccines for meningococcal serogroups A/C/Y/W135 are being formulated the O-acetylation status of their respective capsular polysaccharides has not previously been studied in the UK for all components. Although this has been elucidated for serogroup C, little is known about the O-acetylation status of serogroups W135 and Y. Meningococcal serogroup W135 (n=181) and Y (n=90) isolates submitted to the PHLS Meningococcal Reference Unit in 1996, 2000 and 2001 were investigated for O-acetylation capsular status by dot blot assay.

Reduced antibody response to revaccination with meningococcal serogroup A polysaccharide vaccine in adults.

Widespread use of meningococcal A and C polysaccharide (MACP) vaccines has raised concerns about induction of hyporesponsiveness to these polysaccharides. Immunological hyporesponsiveness to C polysaccharide has been clearly documented in infants, children and adults but only limited data from Gambian children are available for A polysaccharide. We investigated whether a second dose of MACP, given 6 months after an initial dose affected the immunological response as measured by the serum bactericidal assay (SBA) and enzyme-linked immunosorbent assay (ELISA), to serogroup A meningococci in young adults (university students, n=36).

Prevalence of de-O-acetylated serogroup C meningococci before the introduction of meningococcal serogroup C conjugate vaccines in the United Kingdom.

Meningococcal serogroup C conjugate (MCC) vaccines have been introduced in the UK to combat the rise in serogroup C meningococcal disease. Serogroup C meningococci may occur naturally expressing either O-acetylated (Oac(+)) or de-O-acetylated (Oac(-)) polysaccharide capsules. In a small study in the USA in the 1970s 15% of serogroup C meningococcal case isolates were reported to be Oac(-) though the prevalence of these Oac(-) isolates has not been recorded in the UK.

Meningococcal serogroup C-specific IgG antibody responses and serum bactericidal titres in children following vaccination with a meningococcal A/C polysaccharide vaccine.

In the UK, a co-ordinated series of phase II studies is being undertaken with meningococcal serogroup C conjugate (MCC) vaccines. The use of meningococcal A/C polysaccharide (MACP) vaccines in control arms in young children has been avoided because of the well recognised short comings of these vaccines. Following a cluster of serogroup C disease centred on a day nursery, intervention by MACP vaccination was performed as an outbreak control measure.