The genetic structure of Neisseria meningitidis populations in Cuba before and after the introduction of a serogroup BC vaccine

VA-MENGOC-BC Vaccination Induces Serum and Mucosal Anti Neisseria gonorrhoeae Immune Responses and Reduces the Incidence of Gonorrhea

BACKGROUND

Overall, there are over 30 different sexually transmitted infections with Neisseria gonorrhoeae being the third most frequent with a reported 78 million cases per year. Gonococcal infection causes genital inflammation, which can be a risk factor for others sexually transmitted infections, particularly human immunodeficiency virus. Gonorrhea is a treatable disease, but recently an increase in antibiotic resistance has been of concern. There are currently no vaccines available. However, parenteral vaccination with anti N. meningitidis serogroup B vaccine has been reported to decrease the incidence of gonococcal burden in New Zealand and in Cuba despite the fact that parenteral vaccination is not deemed to induce mucosal IgA. Here we explore possible mechanisms of protection against gonococcal infection through parenteral meningococcal B vaccination.

METHODS

Ninety-two serum, saliva and oropharyngeal swabs samples of young adults (healthy and Neisseria carriers) of the internal higher school were obtained. They have been vaccinated with VA-MENGOC-BC (MBV) during their infancy and boosted with a third dose during this study. Serum and saliva samples were analyzed by ELISA and Western blot to measured IgG and IgA antibodies against N. meningitidis and N. gonorrhoeae antigens. N. meningitidis carriers were determined by standard microbiologic test. In addition, we reviewed epidemiologic data for N. meningitidis and N. gonorrhoeae infections in Cuba.

RESULTS

Epidemiologic data show the influence of MBV over gonorrhea incidence suggesting to be dependent of sexual arrival age of vaccines but not over syphilis. Laboratorial data permit the detection of 70 and 22 noncarriers and carriers of N. meningitidis, respectively. Serum anti-MBV antigens (PL) responses were boosted by a third dose and were independent of carriage stages, but saliva anti-PL IgA responses were only present and were significant induced in carriers subjects. Carriers boosted with a third dose of MBV induced similar antigonococcal and -PL saliva IgA and serum IgG responses; meanwhile, serum antigonococcal IgG was significantly lower. In saliva, at least 2 gonococcal antigens were identified by Western blot. Finally, gonococcal-specific mucosal IgA antibody responses, in addition to the serum IgG antibodies, might contributed to the reduction of the incidence of N. gonorrhoeae. We hypothesize that this might have contributed to the observed reductions of the incidence of N. gonorrhoeae.

CONCLUSION

These results suggest a mechanism for the influence of a Proteoliposome-based meningococcal BC vaccine on gonococcal incidence.

The Global Meningococcal Initiative meeting on prevention of meningococcal disease worldwide: Epidemiology, surveillance, hypervirulent strains, antibiotic resistance and high-risk populations

INTRODUCTION

The 2018 Global Meningococcal Initiative (GMI) meeting focused on evolving invasive meningococcal disease (IMD) epidemiology, surveillance, and protection strategies worldwide, with emphasis on emerging antibiotic resistance and protection of high-risk populations. The GMI is comprised of a multidisciplinary group of scientists and clinicians representing institutions from several continents.

AREAS COVERED

Given that the incidence and prevalence of IMD continually varies both geographically and temporally, and surveillance systems differ worldwide, the true burden of IMD remains unknown. Genomic alterations may increase the epidemic potential of meningococcal strains. Vaccination and (to a lesser extent) antimicrobial prophylaxis are the mainstays of IMD prevention. Experiences from across the globe advocate the use of conjugate vaccines, with promising evidence growing for protein vaccines. Multivalent vaccines can broaden protection against IMD. Application of protection strategies to high-risk groups, including individuals with asplenia, complement deficiencies and human immunodeficiency virus, laboratory workers, persons receiving eculizumab, and men who have sex with men, as well as attendees at mass gatherings, may prevent outbreaks. There was, however, evidence that reduced susceptibility to antibiotics was increasing worldwide.

EXPERT COMMENTARY

The current GMI global recommendations were reinforced, with several other global initiatives underway to support IMD protection and prevention.

Cross-protection induced by VA-MENGOC-BC® vaccine

I would like to comment on the article “Commentary: Impact of meningococcal group B OMV vaccines, beyond their brief”, DOI: 10.1080/21645515.2017.1381810. The author states that meningococcal group B OMVs vaccines –such as VA-MENGOC-BC®– may induce moderate protection against Neisseria gonorrhoeae. I agree. However, the author states that “there was no evidence of effectiveness in the younger children.” The effectiveness of VA-MENGOC-BC® in heterologous contexts has been higher than 80% in individuals older than 4 years old, but the effectiveness in younger children should not be undervalued; it has usually been higher than 60%, and results markedly higher when evaluated based on mortality rates. There is strong evidence that VA-MENGOC-BC® may induce cross-protection against heterologous N. meningitidis strains and N. gonorrhoeae.

Potential impact of the 4CMenB vaccine on oropharyngeal carriage of Neisseria meningitidis

The analysis of the potential impact of the meningococcal vaccines in asymptomatic carriers has become one of the key aspects in the evaluation of new vaccines and of their impact on disease control. An important step in this direction is provided by the analysis of the sequence variability and surface-exposure of the 4CMenB (Bexsero®) vaccine antigens, as well as the cross-reactivity of vaccine induced antibodies, in isolates from healthy carriers. The Spanish Reference Laboratory, in collaboration with the University Hospital Marqués de Valdecilla in Santander (Spain), carried out a meningococcal carrier survey between May 2010 and April 2012 (population aged 4 to 19 years). The present study was done on 60 meningococcal carrier strains representative of the overall strain panel obtained and compared to invasive strains isolated in Spain in the same time. We found quantifiable levels of fHbp and NHBA expression and immunologic cross-reactivity in 10% and 75% of analyzed carrier strains, respectively, so the potential impact of the 4CMenB vaccine on Spanish asymptomatic carrier strains is expected to be mediated by the NHBA antigen.

Using multilocus sequence typing to study bacterial variation: prospects in the genomic era

Multilocus sequence typing (MLST) indexes the sequence variation present in a small number (usually seven) of housekeeping gene fragments located around the bacterial genome. Unique alleles at these loci are assigned arbitrary integer identifiers, which effectively summarizes the variation present in several thousand base pairs of genome sequence information as a series of numbers. Comparing bacterial isolates using allele-based methods efficiently corrects for the effects of lateral gene transfer present in many bacterial populations and is computationally efficient. This 'gene-by-gene' approach can be applied to larger collections of loci, such as the ribosomal protein genes used in ribosomal MLST (rMLST), up to and including the complete set of coding sequences present in a genome, whole-genome MLST (wgMLST), providing scalable, efficient and readily interpreted genome analysis.

Pathogen typing in the genomics era: MLST and the future of molecular epidemiology

Multi-locus sequence typing (MLST) is a high-resolution genetic typing approach to identify species and strains of pathogens impacting human health, agriculture (animals and plants), and biosafety. In this review, we outline the general concepts behind MLST, molecular approaches for obtaining MLST data, analytical approaches for MLST data, and the contributions MLST studies have made in a wide variety of areas. We then look at the future of MLST and their relative strengths and weaknesses with respect to whole genome sequence typing approaches that are moving into the research arena at an ever-increasing pace. Throughout the paper, we provide exemplar references of these various aspects of MLST. The literature is simply too vast to make this review comprehensive, nevertheless, we have attempted to include enough references in a variety of key areas to introduce the reader to the broad applications and complications of MLST data.

Clonal analysis of Neisseria meningitidis serogroup B strains in South Africa, 2002 to 2006: emergence of new clone ST-4240/6688

From August 1999 through July 2002, hyperinvasive Neisseria meningitidis serogroup B (MenB) clonal complexes (CCs), namely, ST-32/ET-5 (CC32) and ST-41/44/lineage 3 (CC41/44), were predominant in the Western Cape Province of South Africa. This study analyzed MenB invasive isolates from a national laboratory-based surveillance system that were collected from January 2002 through December 2006. Isolates were characterized by pulsed-field gel electrophoresis (PFGE) (n = 302), and multilocus sequence typing (MLST) and PorA and FetA typing were performed on randomly selected isolates (34/302, 11%). In total, 2,400 cases were reported, with the highest numbers from Gauteng Province (1,307/2,400, 54%) and Western Cape Province (393/2,400, 16%); 67% (1,617/2,400) had viable isolates and 19% (307/1,617) were identified as serogroup B. MenB incidence remained stable over time (P = 0.77) (average incidence, 0.13/100,000 population [range, 0.10 to 0.16/100,000 population]). PFGE (302/307, 98%) divided isolates (206/302, 68%) into 13 clusters and 96 outliers. The largest cluster, B1, accounted for 25% of isolates (76/302) over the study period; its prevalence decreased from 43% (20/47) in 2002 to 13% (8/62) in 2006 (P < 0.001), and it was common in the Western Cape (58/76, 76%). Clusters B2 and B3 accounted for 10% (31/302) and 6% (19/302), respectively, and showed no significant change over time and were predominant in Gauteng. Randomly selected isolates from clusters B1, B2, and B3 belonged to CC32, CC41/44, and the new CC4240/6688, respectively. Overall, 15 PorA and 12 FetA types were identified. MenB isolates were mostly diverse with no single dominant clone; however, CC32 and CC41/44 accounted for 35% and the new CC4240/6688 was the third most prevalent clone.

Evolutionary and genomic insights into meningococcal biology

Epidemic disease caused by Neisseria meningitidis, the meningococcus, has been recognized for two centuries, but remains incompletely controlled and understood. There have been dramatic reductions in serogroup A and C meningococcal disease following the introduction of protein-polysaccharide conjugate vaccines, but there is currently no comprehensive vaccine against serogroup B meningococci. Genetic analyses of meningococcal populations have provided many insights into the biology, evolution and pathogenesis of this important pathogen. The meningococcus, and its close relative the gonococcus, are the only pathogenic members of the genus Neisseria, and the invasive propensity of meningococci varies widely, with approximately a dozen 'hyperinvasive lineages' responsible for most disease. Despite this, attempts to identify a 'pathogenome', a subset of genes associated with the invasive phenotypes, have failed; however, genome-wide studies of representative meningococcal isolates using high-throughput sequencing are beginning to provide details on the relationship of invasive phenotype and genotype in this fascinating organism and how this relationship has evolved.

Epidemiology and prevention of meningococcal disease: a critical appraisal of vaccine policies

Meningococcal disease is characterized by a marked variation in incidence and serogroup distribution by region and over time. In several European countries, Canada and Australia, immunization programs, including universal vaccination of infants or toddlers with catch-up campaigns in children and adolescents, aimed at controlling disease caused by meningococcal serogroup C have been successful in reducing disease incidence through direct and indirect protection. More recently, meningococcal conjugate vaccines targeting disease caused by serogroups A, C, W-135 and Y have been licensed and are being used in adolescent programs in the USA and Canada while a mass immunization campaign against serogroup A disease has been implemented in Africa. Positive results from clinical trials using vaccines against serogroup B disease in various age groups suggest the possibility of providing broader protection against serogroup B disease than is provided by the currently used outer membrane vesicle vaccines. The purpose of our review of meningococcal epidemiology and assessment of existing policies is to set the stage for future policy decisions. Vaccination policies to prevent meningococcal disease in different regions of the world should be based on quality information from enhanced surveillance systems.