Group B Neisseria meningitidis Vaccine Shows Promise

An investigational vaccine may represent a strong lead in the fight against group B Neisseria meningitidis according to results of a phase 2 study published online in the Lancet

Administered in 3 doses over the course of 6 months a new bivalent vaccine was well tolerated and induced a strong immune response against multiple strains of the potentially deadly bacterium in approximately 90 of participants in the vaccine group

Although strainspecific meningococcal serogroup B vaccines are currently used to control localized outbreaks in countries such as Cuba and New Zealand the development of a multiplestrain vaccine has been hampered by the variability of capsular antigens

To address the issue researchers developed the bivalent vaccine using lipoprotein 2086 a surfaceexposed and immunogenetic factor H binding protein hSBA that is present in at least 98 of all meningococcal group B strains An equal number of variants from families A and B were included in the vaccine

quotOur data suggest that this vaccine is a promising and broadly protective meningococcal serogroup B vaccine candidate If additional studies show similar immunogenicity and tolerability this vaccine might help to reduce the global burden of invasive meningococcal diseasequot write lead author Peter Richmond MBBS from the University of Western Australia School of Paediatrics and Child Health Vaccine Trials Group Telethon Institute for Child Health Research Princess Margaret Hospital for Children Subiaco and colleagues

As previously reported by Medscape Medical News a similar multicomponent serogroup B vaccine is currently under development by Novartis and has been tested in almost 2000 healthy infants

Bivalent Vaccine Tested in More Than 500 Healthy Adolescents

To test the safety and immunogenicity of the lipoprotein 2086 vaccine researchers recruited 539 healthy adolescents from 25 sites across Australia Poland and Spain

Participants were randomly assigned to receive 1 of 3 vaccine doses 60 amp956g 120 amp956g or 200 amp956g or a placebo injection administered at 0 2 and 6 months 511 participants received all 3 doses

Serum bactericidal assays which are accepted as a surrogate assay for vaccine efficacy were used to detect antibody responses against a panel of 8 serogroup B strains that express different alleles of hSBA families A and B The primary endpoint was seroconversion rates for the 2 indicator strains PMB1745 A05 and PMB 17 B02

Immunogenetic titer was defined as the level of serum dilution needed to achieve a 50 decrease in bacterial counts relative to placebo

Results showed that all 3 doses produced an immune response in 80 to 100 of participants depending on the dose and strain tested

The 120amp956g and 200amp956g vaccine doses were similarly effective seroconversion rates for the PMB1745 chain were 928 and 940 respectively vs placebo 55 Corresponding response rates for the PMB17 chain were 866 and 848 vs placebo 13

Seroconversion rates in the 60amp956g group were also high and typically similar to those achieved by higher doses after the second and third vaccinations 895 and 810 respectively

Adverse Events Mild to Moderate in Severity and SelfLimited

Adverse events were reported in 389 and 472 of participants receiving 120amp956g and 200amp956g vaccine doses respectively and 446 of those receiving placebo

Mild to moderate injection site pain was common and occurred more frequently among participants receiving the vaccine lasting a mean of 2 to 3 days The most common systemic events were mild to moderate fatigue fever and headache that lasted 1 to 3 days Adverse event incidence and severity did not increase with subsequent vaccinations

Only 1 serious adverse event was considered related to the study vaccine A boy aged 13 years experienced a sudden severe headache and vomiting within an hour of the third dose He was treated with epinephrine to counter a drop in blood pressure and his symptoms resolved with no additional treatment

Although the study tested a limited number of meningococcal serogroup B strains the authors note that those included were epidemiologically relevant and represent 4 of 6 hSBA strains

quotThe choice of the strains for future serum bactericidal assays should also account for global and local epidemiological distributions of the alleles that encode factor H binding proteinquot write MuhamedKheir Taha MD and AlaEddine Deghmane MD from the Pasteur Institute in Paris France in an accompanying comment

quotSurveillance of meningococcal isolates and typing should continue and include sequencing of genes that encode factor H binding protein to monitor the emergence or expansion of any escape variantsquot the commentators add

Death in a Laboratory Worker

quotThe high proportion of hSBA response to all test strainssuggests that bivalent recombinant lipoprotein 2086 is a broadly protective vaccine and that two or three doses are sufficient to confer high seroprotectionquot the authors write

Large phase 3 trials are needed to define the reactogenicity breadth of coverage and duration of immunological protection afforded by the vaccine The overall risktobenefit profile suggests that a 120amp956g dose may be optimal

quotDevelopment of a vaccine against N meningitidis serogroup B is a major unmet medical need because this serogroup is the most prevalent in many regionsquot including Europe North America and Oceania comment Dr Taha and Dr Deghmane

A 25yearold man in California died last week from sepsis potentially related to his work with meningococcal bacteria According to the San Francisco Chronicle the Veterans Affairs researcher began feeling ill on Friday evening and died after arriving at the hospital the next morning

quotIn his case the time between the onset of symptoms and death was 17 hours Thats not uncommon with this diseasequot said Harry Lampiris MD chief of infectious disease at the San Francisco VA in the article explaining that initial symptoms tend to be vague

Investigators are working to determine whether the strain that killed the researcher came from the laboratory

quotWe cant rule out the possibility it was acquired in the communityquot Dr Lampiris said noting that 10 to 15 cases of meningococcal infection are reported in San Francisco each year and that current vaccines are not effective against this particular bacterial strain

Date : 09 May, 2012
Reference : www.medscape.com/viewarticle/763530

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