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Genomic Analysis of Meningococcal Serogroup W

Genomic Analysis of Meningococcal Serogroup W. Xin Wang, Ph.D Meningitis Laboratory CDC. Introduction. N. meningitidis. Human commensal bacterium and also one of the common pathogens causing bacterial meningitis.

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Genomic Analysis of Meningococcal Serogroup W

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  1. Genomic Analysis of Meningococcal Serogroup W Xin Wang, Ph.D Meningitis Laboratory CDC

  2. Introduction

  3. N. meningitidis • Human commensal bacterium and also one of the common pathogens causing bacterial meningitis. • 12 serogroups based on the structure and chemical composition of cell surface associated capsular polysaccharide. • Only six serogroups (A, B, C, W, X, and Y) are associated with most invasive disease.

  4. N. meningitidis • Frequent horizontal gene transfer events and vaccine-induced immune selection • Antigenically and genetically diverse • Dynamic population structure • Common typing methods to determine genetic/antigentic variations • Multilocus sequence typing (MLST) • Typing of outer membrane protein (OMP) encoding genes (porA, fetA, fHbp, nadA, and nhbA) • Pulse-Field Gel Electrophoresis (PFGE)

  5. MLST • Targets the internal region (400-500 bps) of the 7 house-keeping genes/loci • For each locus, an allele number is assigned to each unique nucleotide sequence. • A sequence type (ST) is defined by the allelic profile of the seven loci. • Strains that have at least four alleles in common are usually defined as the same clonal complex (CC). Maiden, M., et al. 1998. PNAS

  6. OMP typing • PorA (for porin A) • Class 1 transmembrane protein with 8 loops • Major component of OMV-based vaccines • Two hypervariable regions, VR1 (loop 1) and VR2 (loop 4). • Nomenclature: P1.5-2,16-2 • VR1 & VR2 are targeted by the bactericidal antibodies and are thus under selective pressure. • FetA (ferric enterobactin transport) • Formerly FrpB (iron-repressed protein B) • 13 surface-exposed loops • One variable region: F3-3 • B vaccine immunogens • FHbp, NadA and NhbA

  7. Strain genotypes with significant changes between 2000-05 and 2006-10, ABCs (Wang et al unpublished)

  8. Meningococcal disease • Significant public health concern due to its high mortality rate world-wide. • Meningococcal meningitis epidemics were reported in many other countries in North America, Asia, Europe and South America. • Shift in the global epidemiology of meningococcal disease in post-vaccine era

  9. Meningitis epidemics in the meningitis belt • highest incidence (up to 1000 per 100, 000 population) found in the belt • occur in cycles of 8-10 years • predominately caused by serogroup A pre-MenAfriVac http://wwwnc.cdc.gov/travel/yellowbook/2012/

  10. Eradication of serogroup A meningitis epidemics • MenAfriVac, an affordable serogroup A conjugate vaccine developed for African countries • Introduction in Burkina Faso, Mali and Niger in 2010 • No serogroup A detected among vaccinated population http://www.thegatesnotes.com/Topics/Health/The-MenAfriVac-Vaccine-an-Amazing-Success-Story-in-Global-Health http://www.meningitis.org/assets/x/53978

  11. Post-MenAfriVac • Followed the implementation of MenAfriVac, serogroup W becomes the most prevalent strain causing meningococcal disease in vaccinated countries. • There is an increase in serogroup W disease in the vaccinated countries such as Burkina Faso and Mali. • This is extremely concerning because serogroup W strains currently circulating in Africa may have the potential to cause epidemics and large outbreaks.

  12. NmW and outbreaks

  13. Hajj outbreak • The first large NmWoutbreak occurred during the Hajj pilgrimage in Saudi Arabia in 2000 • More than 300 cases were reported • Caused by a strain of CC11 with a PorA type of P1.5,2, PFGE pattern 40, and 16S type 31 • This strain is known as the Hajj clone

  14. Hajj associated outbreak • Intercontinental spread of serogroupW (the Hajj clone) since Hajj outbreak: European, Asian, Middle East, North African countries and the United States. • A large outbreak involving nine European countries (the UK, France, the Netherlands, Germany, Finland, Sweden, Belgium, Switzerland, and Norway) was reported immediately following the Hajj outbreak in 2000. • A phylogenetic analysis indicated the Hajj outbreak and associated strains collected from Saudi Arabia, France, Singapore, Finland and the United States in 2000 had identical PFGE pattern (40), 16S type (31) and PorA type (P1.5,2), and belonged to the CC11 (ST-11)/ET-37 complex (ET-27).

  15. NmW strains from 1970-2000 that were not epidemiologically linked to the Hajj outbreak • Diverse genetic background • Some strains were genetically identical to the Hajj clone by PFGE, MLEE and PorAtyping; 16S type differs by 3 nucleotides • The Hajj-related clone circulating in different regions before 2000; • Due to the recombining nature of N. meningitidis, genetic variation occurred during the transmission • The Hajj outbreak led to the global transmission of this clone.

  16. NmW in the US • Accounts for <5% of invasive meningococcal disease in the United States • 14 W cases in South FL, 2008-9 (6 cases during 2004-7) • CC11/ST11, and similar to the Hajj clone by PFGE (Wang et al unpublished)

  17. NmW in Africa • CC11/ET-37 complex has been present in Africa since at least 1993 • In 2002, a serogroup W epidemic was reported in Burkina Faso, which affected 12,000 people and caused 1400 deaths. • Caused by a CC11 strain, showing similarity to the Hajj clone • This clonal complex continues to spread in African countries after the 2002 Burkina Faso epidemic and remains to be the prevalent genotype. • Clonal complex 175 emerged between 2002 and 2010.

  18. NmW strains in the meningitis belt between 2004 and 2010, Pre-MenAfriVac Caugant DA, Kristiansen PA, Wang X, Mayer LW, et al. (2012) PLoSONE 7(9): e46019.doi:10.1371/journal.pone.0046019

  19. Project Objectives

  20. To determine the genetic similarity and difference of NmW strains from different geographic locations, and the genetic relatedness of these strains to the Hajj clone • To identify genetic markers associated with epidemics and outbreaks. • To determine whether capsule switching has occurred between serogroups W and C.

  21. PorA, FetA, 16S, FHbp, NadA, NhbA etc?

  22. Strain collection

  23. Strain collection Submission type Epidemic vs Endemic Outbreak vs sporadic Serogroup W A X

  24. Strain collection

  25. Nov 18-28, 2013 March 6, 2013 Nov 12-14, 2013 unpublished

  26. Capsular Switching Allelic exchange of serogroup-specific gene (Swartleyet al 1997) A capsule switching event is defined as an isolate of a certain serogroup belonging to a clonal complex that is commonly associated with a different serogroup. A possible mechanism to escape the host immune system

  27. The cap locus of N. meningitidis Genogroup-specific Capsule Biosynthesis Genogroup Capsule Transport tex ctrD ctrB ctrA cssA cssB cssC B csb galE ctrC tex ctrD ctrB ctrA cssA cssB C cssC galE ctrC csc Y tex ctrD ctrB ctrA cssB cssC csy galE ctrC cssA W tex ctrD ctrB ctrA cssA cssB cssC csw galE ctrC tex ctrD ctrB ctrA csxA csxB csxC X ctrC galE tex ctrD ctrB ctrA csaA csaB csaC A galE ctrC csaD tex NG galE …other genetic mutations possible

  28. Capsular switching events among the US isolates from 2006-10, ABCs • SerogroupB to C (n=56) • Switching from C to B (n=10) • Switching between Y and W in both directions (n=10). • Switching from B/C to Y/W (n=4) and Y/W to B/C (n=7) • Switching from B, C, Y and W to other serogroups (n=9)

  29. Capsular Switching between C and W • CC11/ET-37 complex is usually associated with serogroup C. • Capsule switching might have occurred between serogroups W and C, but when and in which direction is not known

  30. Acknowledgement CDC MVPDB Meningitis Laboratory CDC MVPDB epidemiology team National Reference Laboratories (CHUP-CDG, CHU-YO, CHU-SS, and CM, Burkina Faso) National Reference Laboratory, Mali Dr. Pierre Nicolas, former WHO CC, France

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