Comparison of PorA VR types and porA promoter sequence from Neisseria meningitidis B isolated from non-immunised children and vaccine failures immunised with a serogroup B outer membrane protein vaccine (original) (raw)
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Journal of Medical Microbiology, 2008
Identification of Neisseria meningitidis PorA types remains important, as the PorA protein is a major immunogenic component of several meningococcal vaccines under development. In this study, 191 N. meningitidis serogroup B isolates collected in Argentina through active laboratory-based surveillance from 2001 to 2003 were serosubtyped. Nucleotide sequences of the porA variable region 1 (VR1) and VR2 regions were determined in 52 non-serosubtypeable isolates. A substantial number of distinct VR types were identified, and a new VR2 variant from the P1.16 family was described. This is the first report describing PorA types in N. meningitidis serogroup B isolates in Argentina. Furthermore, the wide diversity of subtypes detected by serosubtyping and genosubtyping reveals the difficulty in designing a useful outer-membrane vaccine applicable in this country. A possible mechanism responsible for altered PorA expression was analysed in two PorA types.
Vaccine Research
Introduction: Neisseria meningitidis is a major causative agent of bacterial septicemia and meningitis in human. PorA is a major component of the outer membrane of N. meningitidis and functions as a cationic Porin. This study aimed to clone and determine the expression of PorA as the first step for producing a proper antigen in a vaccine study against N. meningitidis. Methods: An approximately 1200-bp fragment of porA gene was amplified by PCR using N. meningitidis serogroup A genomic DNA and then cloned into prokaryotic expression vector pET-28a. The resulting construct (pET28a-porA plasmid) was transformed into competent E.coli BL21 cells for expression of recombinant protein. The proper overexpression of the recombinant protein was verified by SDS-PAGE and Western Blotting. Results: Cloning of porA was confirmed by colony-PCR and enzymatic digestion. The nucleotide sequence homology of the cloned porA gene was 97% , compared to the reference gene (NCBI GenBank accession number AL157959.1). The prokaryotic expression system (pET28a-porA-BL21) could produce our 45-kDa target recombinant protein, efficiently. Conclusion: The prokaryotic expression system and conditions used in this study provides an applicable method for producing recombinant PorA and possibly many other bacterial outer membrane proteins for future vaccine studies.
Clinical and diagnostic laboratory immunology, 1996
The currently used serological subtyping scheme for the pathogen Neisseria meningitidis is not comprehensive, a proportion of isolates are reported as not subtypeable (NST), and few isolates are fully characterized with two subtypes for each strain. To establish the reasons for this and to assess the effectiveness of DNA-based subtyping schemes, dot blot hybridization and nucleotide sequence analyses were used to characterize the genes encoding antigenic variants of the meningococcal subtyping antigen, the PorA protein. A total of 233 strains, including 174 serologically NST and 59 partially or completely subtyped meningococcal strains, were surveyed. The NST isolates were chosen to be temporally and geographically representative of NST strains, isolated in England and Wales, and submitted to the Meningococcal Reference Unit in the period 1989 to 1991. The DNA-based analyses demonstrated that all of the strains examined possessed a porA gene. Some of these strains were serologically...
Journal of medical …, 2004
The PorA protein is a potential candidate as a vaccine component against meningococcal disease. However, this protein experiences antigenic variation and is subject to phase variations to evade immune selective pressure. In this study, the mechanisms responsible for altered expression of the PorA protein were analysed in 50 non-subtypable strains isolated from patients with meningococcal disease in Spain. The porA gene was amplified from 47 of the 50 strains. The majority of isolates were not recognized by the subtyping panel, as a result of non-synonymous base changes in the variable regions of the porA gene. Two of these strains revealed a premature stop codon before the variable region VR1 of PorA due to a single base-pair substitution at position 109 of the porA coding region. Another two presented a homopolymeric tract of eight adenine residues in the coding region, producing a DNA strand-slippage mechanism and PorA phase variation.
Genetic and immunologic characterization of a novel serotype 4, 15 strain of Neisseria meningitidis
FEMS Immunology & Medical Microbiology, 2000
The porin proteins of Neisseria meningitidis are important components of outer membrane protein (OMP) vaccines. The class 3 porin gene, porB, of a novel serogroup B, serotype 4, 15 isolate from Chile (Ch501) was found to be VR1^4, VR2^15, VR3^15 and VR4^15 by porB variable region (VR) typing. Rabbit immunization studies using outer membrane vesicles revealed immunodominance of individual PorB (class 3) VR epitopes. The predominant anti-Ch501 PorB response was directed to the VR1 epitope. Anti-PorB VR1 mediated killing was suggested by the bactericidal activity of Ch501 anti-sera against a type 4 strain not expressing PorA or class 5 OMPs. Studies that examine the molecular epidemiology of individual porB VRs, and the immune responses to PorB epitopes, may contribute to the development of broadly protective group B meningococcal vaccines.
2001
In this study, we determined the prevalence of serosubtypes of MenB isolated in 10 Brazilian states and the Federal District during 1997 and 1998 and investigated the extent of PorA VR sequence variation among the most prevalent serosubtypes to evaluate the possible use of an outer membrane vesicle (OMV)-, PorA-based vaccine to prevent meningococcal disease in Brazil. During this period, a total of 8,932 cases of meningococcal disease were reported. Only 42% (n ؍ 3,751) of the reported cases were laboratory confirmed, and about 60% (n ؍ 2,255) of those were identified as MenB. Among 1,297 MenB strains selected for this study, the most prevalent serosubtypes were P1.19,15 (66%), P1.7,1 (11%), and P1.7,16 (4%). PorA VR typing showed that 91% of the P1.19,15 strains analyzed had VR1 and VR2 sequences identical to those of the prototype strain. No sequence variation was detected among the 40 strains representing all isolated MenB P1.7,16 strains in the three southern states, where this serosubtype accounts for 75% of the serosubtypes identified. Similarly, all P1.7,1 strains were identified by PorA typing as P1.7-1,1. Although further improvements in the reporting of cases and collection of strains in Brazil are needed, our data suggest that a trivalent OMV-based vaccine prepared with PorA types P1.19,15, P1.7-1,1, and P1.7,16 may be appropriate to control serogroup B meningococcal disease in most of the Brazilian states.
PorA typing of Neisseria meningitidis isolates from Iranian children for vaccine design
Vaccine Research
Introduction: As the causative agent of meningitis, Neisseria meningitidis has different serogroups. The purpose of this study was to investigate the molecular properties of N. meningitidis strains among Iranian cases. Methods: 450 samples were collected from children under 5 years of age. Detection of Neisseria genus was done by phenotypic and genotypic methods. Multiplex PCR was used to identify the serogroups of N. meningitides. The sequencing of variable regions of porA gene was performed for detection of the subserogroups. Results: From 137 (30.44%) Neisseria isolates, 4 isolates (0.88%) belonged to N. meningitidis and 133 isolates (29.55%) belonged to other species. Multiplex PCR results showed that one isolate belonged to serogroup A while 3 belonged to serogroup B. The analysis of amplified VR1 and VR2 variable regions of porA showed 100% identity of the serogroup A strain with strain BZ83N and the serogroup B strains with strain 528 of N. meningitidis. In accordance with other findings in Asia, serogroups A and B were the most prevalent serogroups of N. meningitidis. Sequencing of variable regions of porA could identify the subserogroups of the isolates. Conclusion: sequencing of porA could be a valuable method for identification of N. meningitidis strains to be used in epidemiological studies as well as improved vaccine designs.
The porA gene in serogroup A meningococci: evolutionary stability and mechanism of genetic variation
Molecular Microbiology, 1994
Molecular analyses were applied to the genes encoding variants of the serosubtyping antigen, the class 1 outer membrane protein (PorA), from 55 serogroup A Neisseria meningitidis strains. These genes were evolutionarily stable and exhibited a limited range of genetic variation, primarily generated by recombination. Translation of the gene sequences revealed a total of 19 distinct amino acid sequences in the variable regions of the protein, 6 of which were not recognized by currently available serosubtyping monoclonal antibodies. Knowledge of these amino acid sequences permitted a rationai re-assignment of serosubtype names. Comparison of the compiete genes with porA gene sequences from serogroup B and C meningococci showed that serogroup A possessed a iimited number of the possible porA genes from a globaiiy distributed gene pool. Each serogroup A subgroup was characterized by one of four porA gene types, probabiy acquired upon subgroup divergence, which was stabie over periods of decades and during epidemiological spread. Comparison with other variable genes (pil and iga) indicated that the three alleles were independently assorted within the subgroup, suggesting that their gene types were older than the subgroups in which they occurred.