Raquel Abad

Predicted strain coverage of a meningococcal multicomponent vaccine (4CMenB) in Europe: a qualitative and quantitative assessment.

BACKGROUND A novel multicomponent vaccine against meningococcal capsular group B (MenB) disease contains four major components: factor-H-binding protein, neisserial heparin binding antigen, neisserial adhesin A, and outer-membrane vesicles derived from the strain NZ98/254. Because the public health effect of the vaccine, 4CMenB (Novartis Vaccines and Diagnostics, Siena, Italy), is unclear, we assessed the predicted strain coverage in Europe. METHODS We assessed invasive MenB strains isolated mainly in the most recent full epidemiological year in England and Wales, France, Germany, Italy, and Norway. Meningococcal antigen typing system (MATS) results were linked to multilocus sequence typing and antigen sequence data. To investigate whether generalisation of coverage applied to the rest of Europe, we also assessed isolates from the Czech Republic and Spain. FINDINGS 1052 strains collected from July, 2007, to June, 2008, were assessed from England and Wales, France, Germany, Italy, and Norway. All MenB strains contained at least one gene encoding a major antigen in the vaccine. MATS predicted that 78% of all MenB strains would be killed by postvaccination sera (95% CI 63-90, range of point estimates 73-87% in individual country panels). Half of all strains and 64% of covered strains could be targeted by bactericidal antibodies against more than one vaccine antigen. Results for the 108 isolates from the Czech Republic and 300 from Spain were consistent with those for the other countries. INTERPRETATION MATS analysis showed that a multicomponent vaccine could protect against a substantial proportion of invasive MenB strains isolated in Europe. Monitoring of antigen expression, however, will be needed in the future. FUNDING Novartis Vaccines and Diagnostics.

A generic mechanism in Neisseria meningitidis for enhanced resistance against bactericidal antibodies

The presence of serum bactericidal antibodies is a proven correlate of protection against systemic infection with the important human pathogen Neisseria meningitidis. We have identified three serogroup C N. meningitidis (MenC) isolates recovered from patients with invasive meningococcal disease that resist killing by bactericidal antibodies induced by the MenC conjugate vaccine. None of the patients had received the vaccine, which has been successfully introduced in countries in North America and Europe. The increased resistance was not caused by changes either in lipopolysaccharide sialylation or acetylation of the α2-9–linked polysialic acid capsule. Instead, the resistance of the isolates resulted from the presence of an insertion sequence, IS1301, in the intergenic region (IGR) between the sia and ctr operons, which are necessary for capsule biosynthesis and export, respectively. The insertion sequence led to an increase in the transcript levels of surrounding genes and the amount of capsule expressed by the strains. The increased amount of capsule was associated with down-regulation of the alternative pathway of complement activation, providing a generic mechanism by which the bacterium protects itself against bactericidal antibodies. The strains with IS1301 in the IGR avoided complement-mediated lysis in the presence of bactericidal antibodies directed at the outer membrane protein, PorA, or raised against whole cells.

Effectiveness of meningococcal serogroup C vaccine programmes.

Since the introduction of monovalent meningococcal serogroup C (MenC) glycoconjugate (MCC) vaccines and the implementation of national vaccination programmes, the incidence of MenC disease has declined markedly as a result of effective short-term vaccination and reduction in acquisition of MenC carriage leading to herd protection. Monovalent and quadrivalent conjugate vaccines are commonly used vaccines to provide protection against MenC disease worldwide. Studies have demonstrated that MCC vaccination confers protection in infancy (0-12 months) from the first dose but this is only short-term. NeisVac-C(®) has the greatest longevity of the currently licensed MCC vaccines in terms of antibody persistence, however antibody levels have been found to fall rapidly after early infant vaccination with two doses of all MCC vaccines - necessitating a booster at ∼12 months. In toddlers, only one dose of the MCC vaccine is required for routine immunization. If herd protection wanes following catch-up campaigns, many children may become vulnerable to infection. This has led many to question whether an adolescent booster is also required.

Interlaboratory Standardization of the Sandwich Enzyme-Linked Immunosorbent Assay Designed for MATS, a Rapid, Reproducible Method for Estimating the Strain Coverage of Investigational Vaccines

ABSTRACT The meningococcal antigen typing system (MATS) sandwich enzyme-linked immunosorbent assay (ELISA) was designed to measure the immunologic cross-reactivity and quantity of antigens in target strains of a pathogen. It was first used to measure the factor H-binding protein (fHbp), neisserial adhesin A (NadA), and neisserial heparin-binding antigen (NHBA) content of serogroup B meningococcal (MenB) isolates relative to a reference strain, or “relative potency” (RP). With the PorA genotype, the RPs were then used to assess strain coverage by 4CMenB, a multicomponent MenB vaccine. In preliminary studies, MATS accurately predicted killing in the serum bactericidal assay using human complement, an accepted correlate of protection for meningococcal vaccines. A study across seven laboratories assessed the reproducibility of RPs for fHbp, NadA, and NHBA and established qualification parameters for new laboratories. RPs were determined in replicate for 17 MenB reference strains at laboratories A to G. The reproducibility of RPs among laboratories and against consensus values across laboratories was evaluated using a mixed-model analysis of variance. Interlaboratory agreement was very good; the Pearson correlation coefficients, coefficients of accuracy, and concordance correlation coefficients exceeded 99%. The summary measures of reproducibility, expressed as between-laboratory coefficients of variation, were 7.85% (fHbp), 16.51% (NadA), and 12.60% (NHBA). The overall within-laboratory measures of variation adjusted for strain and laboratory were 19.8% (fHbp), 28.8% (NHBA), and 38.3% (NadA). The MATS ELISA was successfully transferred to six laboratories, and a further laboratory was successfully qualified.

W135 invasive meningococcal strains spreading in South America: significant increase in incidence rate in Argentina.

In Argentina, the incidence rate of meningococcal disease is 0.6 cases per 105 inhabitants, representing around 250 cases declared every year. The number of meningococcal strains received annually at the Reference Laboratory for Meningococci of the National Institute for Infectious Diseases (INEI-

The epidemiology of invasive meningococcal disease in EU/EEA countries, 2004–2014

BACKGROUND Invasive meningococcal disease (IMD) is a major cause of bacterial meningitis and septicaemia although infection by some serogroups may be prevented through vaccination. We aimed to describe the epidemiology of IMD in EU/EEA countries during 2004-2014 to monitor serogroup- and age-specific trends, and compare country trends by the period of meningococcal C conjugate (MCC) vaccine introduction. METHODS We analysed IMD surveillance data by age, gender, serogroup, country and outcome. We estimated the percentage change in annual notification rate (NR), using linear regression analysis of the log of the annual NR. We grouped countries by the year they introduced MCC vaccination into their routine immunisation programmes. RESULTS The overall NR was 0.9/100 000 population, and decreased 6.6% (95%CI: -8.0%;-5.1%) annually. Infants had the highest NR (16.0/100 000), and there were decreasing trends in all age groups <50years. Serogroup B (SgB) caused 74% of all cases, and the majority of cases in all age groups. There were decreasing trends in SgB and serogroup C (SgC) and an increasing trend in serogroup Y. Countries that introduced MCC vaccination before, and between 2004 and 2014, had decreasing trends in NR of SgC, but not countries without routine MCC vaccination. CONCLUSIONS Our findings support evidence that routine MCC vaccination was the driving force behind the decreasing SgC trend. Vaccinating against SgB in the first year of life could help reduce the burden of IMD due to this serogroup. Changing serogroup-specific NR trends highlight the need for high-quality surveillance data to accurately assess the changing epidemiology of IMD, the effectiveness and impact of implemented vaccines, and the need for future vaccines.

A multi-country evaluation of Neisseria meningitidis serogroup B factor H-binding proteins and implications for vaccine coverage in different age groups.

Background: Recombinant vaccines containing factor H–binding protein (fHBP) have been developed for the purpose of protection from invasive meningococcal serogroup B disease. Neisseria meningitidis fHBP sequences can be divided into 2 genetically and immunologically distinct subfamilies (A and B); thus, cross protection is conferred within but not between subfamilies. A comprehensive understanding of fHBP epidemiology is required to accurately assess the potential vaccine impact when considering different vaccination implementation strategies. Methods: Systematically collected invasive meningococcal serogroup B isolates from England, Wales, Northern Ireland, the United States, Norway, France and the Czech Republic were previously characterized for fHBP sequence. This study expanded the evaluation with additional meningococcal serogroup B disease isolates from Spain (n = 346) and Germany (n = 205). This expanded set (n = 1841), collected over a 6-year period (2001 to 2006), was evaluated for fHBP sequence and fHBP subfamily relative to patient age. Results: All 1841 isolates contained fhbp. fHBP sequences from Spain and Germany fell within the previously described subfamilies, with 69% of isolates belonging to subfamily B and 31% to subfamily A; prevalent sequence variants were also similar. Stratification of data by age indicated that disease in infants <1 year of age was caused by a significantly higher proportion of isolates with fHBP subfamily A variants than that seen in adolescents and young adults 11–25 years (47.7% versus 19.5%, P < 0.0001, respectively). Conclusions: These observations highlight a difference in epidemiology of fHBP subfamilies in different age groups, with fHBP subfamily A strains causing more disease in vulnerable populations, such as infants, than in adolescents.

Detection of three stable genetic clones of CTX-M-15-producing Klebsiella pneumoniae in the Barcelona metropolitan area, Spain

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Molecular characterization of invasive serogroup Y Neisseria meningitidis strains isolated in the Latin America region

OBJECTIVES To improve the understanding of serogroup Y invasive meningococcal disease (IMD) in Latin America, particularly IMD molecular epidemiology; 166 Y serogroup isolates received at the National Reference Laboratories of Argentina, Brazil, Chile, Colombia, and Costa Rica during 2000-2006 were characterized by their molecular markers. METHODS This analysis included serological assays to determine serogroup/serotype/serosubtype, DNA sequencing and genotyping of the porB and/or porA genes, multilocus sequence typing (MLST) and fetA allele determination. RESULTS Sixteen different antigenic combinations were observed. Sixty-two (37.3%) isolates were NT:P1.5 and 36 (21.7%) isolates were 14:NST. Thirty-two different STs appeared, but 3 STs (ST-1624, ST-23, and ST-5770) accounted for 69.9% (116) of the strains. Most of the IMD isolates belonged to the ST-23, ST-167 clonal complexes or the group composed by ST-5770 and related STs. CONCLUSIONS Isolates obtained in Colombia and Costa Rica were similar to that of the United States, in that most sequence types belonged to the ST-23 clonal complex. IMD isolates found in Argentina appear to be the result of an independent event and did not spread from nearby countries, being the sequence type ST-1624 (ST-167 clonal complex) the most frequently found. We were unable to correlate an antigenic shift of outer membrane proteins with an increase of serogroup Y meningococcal cases in our collection of isolates.

Multicenter Study for Defining the Breakpoint for Rifampin Resistance in Neisseria meningitidis by rpoB Sequencing

ABSTRACT Identification of clinical isolates of Neisseria meningitidis that are resistant to rifampin is important to avoid prophylaxis failure in contacts of patients, but it is hindered by the absence of a breakpoint for resistance, despite many efforts toward standardization. We examined a large number (n = 392) of clinical meningococcal isolates, spanning 25 years (1984 to 2009), that were collected in 11 European countries, Argentina, and the Central African Republic. The collection comprises all clinical isolates with MICs of ≥0.25 mg/liter (n = 161) received by the national reference laboratories for meningococci in the participating countries. Representative isolates displaying rifampin MICs of <0.25 mg/liter were also examined (n = 231). Typing of isolates was performed, and a 660-bp DNA fragment of the rpoB gene was sequenced. Sequences differing by at least one nucleotide were defined as unique rpoB alleles. The geometric mean of the MICs was calculated for isolates displaying the same allele. The clinical isolates displaying rifampin MICs of >1 mg/liter possessed rpoB alleles with nonsynonymous mutations at four critical amino acid residues, D542, H552, S548, and S557, that were absent in the alleles found in all isolates with MICs of ≤1 mg/liter. Rifampin-susceptible isolates could be defined as those with MICs of ≤1 mg/liter. The rpoB allele sequence and isolate data have been incorporated into the PubMLST Neisseria database (http://pubmlst.org/neisseria/ ). The rifampin-resistant isolates belonged to diverse genetic lineages and were associated with lower levels of bacteremia and inflammatory cytokines in mice. This biological cost may explain the lack of clonal expansion of these isolates.