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Previous Article | Next Article 
Clinical and Diagnostic Laboratory Immunology, November 1998, p. 845-855, Vol. 5, No. 6
Division of Medical Biology,
Received 22 May 1998/Returned for modification 7 August
1998/Accepted 28 August 1998
Neisseria meningitidis isolates are conventionally
classified by serosubtyping, which characterizes the reactivities of
the PorA outer membrane protein variable-region (VR) epitopes with monoclonal antibodies (MAbs). A newer method (PorA VR typing) uses
predicted amino acid sequences derived from DNA sequence analysis. The
resulting classification schemes are not standardized, offering
conflicting and sometimes irreconcilable data from the two methods. In
this paper, we propose a standardization of the PorA VR typing
nomenclature that incorporates serologic information from traditional
PorA serosubtyping with molecular data from predicted VR sequences.
We performed a comprehensive literature and database search, generating
a collection of strains and DNA sequences that reflects the diversity
within PorA that exists to date. We have arranged this information in a
comprehensive logical model that includes both serosubtype and PorA VR
type assignments. Our data demonstrate that the current panel of
serosubtype-defining MAbs underestimates PorA VR variability by at
least 50%. Our proposal for VR typing is informative because amino
acid sequence and serologic information, when serosubtype-defining MAbs
are available, can be deduced simultaneously from the PorA VR
designation. This scheme will be useful in future classification and
applied epidemiologic studies of N. meningitidis,
being a systematic way of selecting PorA vaccine candidates and
analyzing vaccine coverage and failure.
Epidemiologic investigators of
meningococcal disease use classification schemes based on antigenic
diversity among Neisseria meningitidis cell envelope
antigens. All meningococci express either a class 2 or a class 3 outer
membrane protein (OMP), and most strains also express a class 1 OMP
(P1 protein) (14, 30, 31). The class 1 OMP has been
named PorA, and its gene has been designated porA
(16). Similarly, the class 2 and class 3 OMPs have been
named PorB and their gene has been designated porB (5, 9, 16). The amino acid sequences of PorB and PorA do not vary
within an isolate, but sequence differences may be used to differentiate strains. The antigenic variety of meningococcal PorB and
PorA proteins forms the basis of serotyping and serosubtyping, respectively (1, 2, 14).
Serosubtyping is especially important for group B strains, in which
immunity may be serosubtype specific. PorA-specific monoclonal antibodies (MAbs) used for serosubtyping of meningococci are highly bactericidal in vitro, and animals challenged with virulent bacteria were protected when they were first passively immunized with those MAbs
(25). In addition, strains devoid of PorA poorly induced bactericidal antibodies in mice. Transfer of one porA gene
to and its expression in a heterologous strain induced a full
bactericidal response in the recipient strains against the donor
serosubtype (32). Considered together, these results make
the PorA protein an attractive vaccine candidate.
The composition of such a vaccine depends on accurate estimates of PorA
serosubtype distribution and prevalence within a given geographic
region. This information is also used to determine or predict
meningococcal vaccine efficacy and analyze the mechanisms for vaccine
failure (6, 20-22). A comprehensive and reproducible determination of PorA sequence and topology is needed as a scientific basis for these studies. A two-dimensional secondary structure containing eight exposed surface loops (loops I to VIII) has been predicted for PorA and PorB proteins (12, 17, 31). Most variability between PorA proteins resides in two variable regions (VRs), VR1 and VR2, which correspond to loops I and IV, respectively. Serosubtype-defining MAbs react with peptide epitopes located in
these loops (17-19, 31). Two additional regions of more
limited variability in loops V and VI are referred to as semivariable regions 1 and 2 (SVR1 and SVR2). The application of molecular techniques, such as direct porA nucleotide sequence
determination, permits characterization of meningococcal PorA VR
sequences by their predicted amino acid sequences (PorA VR typing).
The choice of PorA epitopes to be included in an OMP vaccine
has, therefore, depended largely on MAb serosubtyping data. However, the lack of MAbs that recognize particular sequences has increased the
importance of PorA VR typing in meningococcal characterization (8,
19, 28, 35). PorA VR typing allows more detailed analysis of
potentially protective epitopes and thus allows estimations of
vaccine efficacy as well as accurate strain identification for
epidemiologic investigations.
Several investigators have either classified PorA VR types (7, 19,
28, 29) or proposed models for PorA VR nomenclature (13,
28). However, the system of designations for PorA VR types is not
standardized and identical VR sequences have been named differently by
different authors. Furthermore, there is no consensus about whether a
PorA VR type designation should also carry information describing
antibody reactivity; serosubtypes and PorA VR types are also sometimes
misinterpreted as each other.
The goal of this study was to combine serologic data from traditional
PorA serosubtyping with molecular data from predicted PorA VR amino
acid sequences in order to propose a standardized PorA VR typing
nomenclature. These data (i) establish the nucleotide sequences of the
porA genes present in representative strains, (ii) estimate
the degree of sequence variation present in each predicted PorA VR
family, (iii) assign or predict the reactivities of all available
serosubtype-defining MAbs with all PorA VR types described, and (iv)
provide the framework for our proposal of a unified nomenclature for
PorA VR typing.
Bacterial strains and serotyping.
Seventy-nine N. meningitidis strains, including serotype and serosubtype reference
strains (n = 27) and additional strains (n = 52), were obtained from M. Achtman, Max-Planck-Institut für Molekulare Genetik, Berlin, Germany; O. L. Frøholm, National
Institute of Public Health (Folkehelsa), Oslo, Norway; P. Kriz,
National Institute of Public Health, Prague, Czech Republic; F. E. Ashton, Laboratory Center for Disease Control, Tunney's Pasture,
Ottawa, Canada; and the Adolfo Lutz Institute, São Paulo, Brazil
(Table 1).
All strains were serosubtyped by dot blotting of whole-cell suspensions
(33) with the MAbs listed in Table
2.
PCR.
The PCR primers P14 (this study) and P22
(17), based on porA nucleotide sequence accession
no. X12899, were predicted to amplify a porA gene product of
1,236 bp (Table 3). This product, 120 bp
longer than that obtained with primers P21 and P22 described by Maiden
et al. (17), includes the start codon. Each final reaction
mixture (100 µl) contained 5 U of Expand DNA polymerase (Boehringer
Mannheim); 10 µl of whole-cell suspension as a template; 10 mM
Tris-Cl (pH 8); 50 mM KCl; 1.5 mM MgCl2; 200 µM (each)
dATP, dCTP, dGTP, and dTTP; and 0.4 µM concentrations of each primer. Reaction mixtures were first incubated for 5 min at 95°C. Then five
cycles of 1 min at 94°C, 2 min at the annealing temperature of
65°C, and 20 s at 72°C were performed. This was followed by 25 cycles of 30 s at 90°C, 20 s at 65°C, and 20 s at
72°C. Reaction mixtures were then incubated at 72°C for a further 5 min. PCR products were purified with a High Pure PCR product
purification kit (Boehringer Mannheim).
1071-412X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Proposed Standardization of Neisseria
meningitidis PorA Variable-Region Typing Nomenclature
ABSTRACT
Top
Abstract
Introduction
Materials & Methods
Results & Discussion
References
INTRODUCTION
Top
Abstract
Introduction
Materials & Methods
Results & Discussion
References
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials & Methods
Results & Discussion
References
TABLE 1.
Serotype, serosubtype, and PorA VR type characteristics
of N. meningitidis strains analyzed
TABLE 2.
Serosubtype-defining MAbs and their identification
and epitope locations
TABLE 3.
Nucleotide sequences of primers used for porA
gene amplification and sequencing
Sequences of porA genes. To assess the genetic diversity of porA genes, 92 porA sequences (9 from serotype or serosubtype reference strains) were obtained from the GenBank database. porA nucleotide sequences were determined for a further 70 meningococcal strains chosen to represent additional serosubtypes or additional isolates of a serosubtype (n = 52) and serotyping reference strains (n = 18) (Table 1). For sequencing, we used 14 primers (7 forward and 7 reverse) designed to be complementary to the conserved regions of the porA gene (Table 3). Sequencing was performed by using a Taq Dye-deoxy terminator cycle sequencing kit (Applied Biosystems, Foster City, Calif.). Sequencing products were purified by using Centri-Sep spin columns (Princeton Separations, Adelphia, N.J.) and resolved on a 5% acrylamide-8 M urea gel with an Applied Biosystems model 373S automated DNA sequencing system. The DNA sequences obtained were aligned and edited, and consensus sequences were determined with the University of Wisconsin Genetics Computer Group software package (10). When a novel nucleotide sequence for any VR was found, the porA gene amplification and sequencing were repeated. Amino acid alignments were obtained by translating nucleotide sequences. Distance matrices were calculated by using the Distances program of the Genetics Computer Group package (10). An exact amino acid match was scored as 1.5, and any other residue was scored as 0.
Nucleotide sequence accession numbers. The sequences of porA genes obtained during the study have been submitted to the GenBank database and assigned the accession numbers listed in Table 1.
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RESULTS AND DISCUSSION |
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Top
Abstract
Introduction
Materials & Methods
Results & Discussion
References
|
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We propose a standardization of PorA VR typing nomenclature that builds on that of Suker et al. (28). A full description of the proposed nomenclature is presented in Table 4. Briefly, PorA VR types have been defined based on PorA VR sequences predicted from the nucleotide sequences of porA genes, while serosubtypes have been defined based on reactivities of serosubtype-defining MAbs with PorA VR epitopes. Some of these definitions have been proposed previously (13, 14, 18, 19, 28, 29, 35), and we have retained these designations or historical names whenever practical.
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Our proposal differs from that of Feavers et al. (13) in that we combine serologic data from traditional PorA serosubtyping with molecular sequence data from predicted PorA VR amino acid sequences. Our PorA VR type designation system carries information describing the reactivity with serosubtype-defining MAbs. We believe it is important to include the enormous body of available serologic data because of its value in understanding meningococcal disease epidemiology.
PorA types. PorA VR types were defined based on predicted amino acid sequences present in exposed loops I (VR1) and IV (VR2) of the PorA protein according to the structural model of class 1 OMPs (31). PorA VR amino acid sequences were located in relation to the position of the translated porA gene of strain MC50 (accession no. X12899) at amino acids 43 to 56 (VR1) and 195 to 208 (VR2) (5). According to our proposal, the PorA VR type composition of a particular strain is designated P1 followed by a period and two underlined capital letters describing the families of VR1 and VR2 (e.g., P1.A,C). PorA VR types are underlined to avoid misinterpretation of serosubtypes and PorA VR types as each other.
If an available MAb recognizes an epitope in a particular PorA VR type, the number designation of that MAb is also used to designate that VR amino acid sequence, e.g., P1.7,A (VR1 carries the epitope for serosubtype-defining MAb 7). Sequential letters were used for those VR sequences for which no MAbs are currently available. For those PorA VR types previously designated serosubtypes (numbers) that are not recognized by any available MAb, we changed the designations from numbers to letters in order of elucidation; e.g., VR2-24 (13) was renamed VR2-D (Table 5) because there is no serosubtype-defining MAb 24 available.
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PorA VR family. As previously described (28, 29), PorA VR families were defined as all VR types with at least 80% amino acid sequence identity with the prototype VR. The prototype of the VR family was defined as that VR type sequence, of the serosubtype reference strain, that carries the epitope for a particular serosubtype-defining MAb; the prototype then receives the serosubtype-defining MAb name (number). For a PorA VR family not recognized by any available MAb, the prototype was defined as the VR amino acid sequence of the strain first sequenced in that family and was designated with a capital letter. The family and its prototype sequence received the same designation (letter or number). The 81 PorA VR types obtained (5 of which are newly described in this study) were grouped into 34 amino acid sequence families (Table 5).
PorA VR family variant. The accumulation of mutations in the serosubtype-encoding regions of the porA gene results in VR families that comprise related amino acid sequences (28). These amino acid variant sequences in a VR family were designated as proposed by Suker et al. (28, 29). Distinct members of the same family were distinguished from the prototype VR and from other variants by lowercase letters given in order of elucidation; e.g., VR1-5b is a related variant in the VR1-5 family. A VR amino acid sequence variant with less than 80% sequence relatedness to the prototype of any family was assigned to a new family, in order of elucidation.
In three of the previously described families of related sequences, the VR1-5, VR2-10, and VR2-13 families, a total of five variants showed no reactivity with the corresponding serosubtype-defining MAb (8, 13, 29, 35). Our results showed that those variants display less than 80% amino acid sequence identity to the prototype family sequence as follows: VR1-5b (66%), VR2-10b (73%), VR2-10d (72%), VR2-10f (66%), and VR2-13d (77%). Therefore, we assigned those variants to new families (Table 5). We did not change the original designations, except where a specific sequence had more than one name in the literature. In these cases, only one designation was retained or a new one was given in order of elucidation (Table 5). For instance, VR2-15b (12) was also named VR2-15c (19). The designation VR2-15b was maintained because the VR2-15 family possesses only the prototype sequence (VR2-15) and two variant sequences (VR2-15a and VR2-15b). Since the detection of PorA VR family variants is not made by immunochemical reactions, we propose the use of additional letters only as part of the PorA VR typing system and not as part of the serosubtyping designation.PorA VR1-7 family. The amino acid sequence ASGQ has previously been identified as the epitope for the serosubtype-defining MAb P1.7 (18). This epitope is present as part of six different PorA VR1 sequences, members of the VR1-7 family, which were designated VR1-7, -7a, -7b, -7c, -7d, and -7e in the present study (Table 5). VR1-7b has previously been shown to contain a 3-amino-acid deletion at the carboxy-terminal side of the epitope (34). As a result, the amino acid sequence ASGQ on VR1-7b may be inaccessible for antibody binding when intact cells are examined by dot blotting or enzyme-linked immunosorbent assay (ELISA) methods (34). In this study we demonstrate that VR1-7a also contains this 3-amino-acid deletion at the carboxy-terminal side of the epitope as well as a 2-amino-acid insertion at the amino-terminal side of the epitope (Table 5). Both changes are consistent with the ASGQ epitope being shifted down the side of loop I somewhat closer to the outer membrane, thus masking the epitope with the other loops or with other molecules such as lipopolysaccharide (19, 34).
In this study, we found that four of eight PorA VR1-7b strains reacted weakly with P1.7 MAb by dot blotting. The only PorA VR1-7a strain tested was negative with the P1.7 MAb by dot blotting; however, the P1.7 epitope was demonstrated on an immunoblot after denaturation of the cells with sodium dodecyl sulfate (SDS) (data not shown). Given that two members of the VR1-7 family present a masked P1.7 epitope and that a reaction with P1.7 MAb in dot blots can present different degrees of reactivity, we suggest caution in the serosubtype designation of strains with such epitopes and care in interpretation of dot blotting results with P1.7 MAb. Additional investigation, such as denaturation of the cells with SDS and PorA VR typing, can be used to identify masked P1.7 epitopes.SVRs. PorA SVR amino acid sequences were located in relation to the position of the translated porA gene of strain MC50 (accession no. X12899) at amino acids 247 to 261 (SVR1) and 299 to 302 (SVR2) (5). Because SVR1 had previously been thought to contribute to the specificity of serosubtype-defining MAb P1.6 (MN19D6-13 [19]), we included SVR1 and SVR2 in our analysis (Table 4). We studied the correlation between serosubtype-defining MAb P1.6 reactivity and amino acid sequences of SVR1 families.
A distance matrix of amino acid sequences for each of these two regions identified 18 distinct PorA SVR types, 15 and 3 of which were located in SVR1 and SVR2, respectively (Table 5). The 18 PorA SVR types obtained were grouped into five amino acid sequence families as described above for PorA VR types (Table 5). Our data indicate that SVR1 is related to the location of P1.6 specificity. The SVR1-6 family consists of three members, SVR1-6, SVR1-6a, and SVR1-6b. All strains with P1.6 MAb reactivity possessed either SVR1-6 or SVR1-6a amino acid sequences. The SVR1-6b variant differs from the prototype SVR1-6 sequence by 2 amino acids close to the apex on loop V, which may explain the lack of reactivity with serosubtype-defining MAb P1.6. No other MAb reactivity was found to be related to SVR1 or SVR2 sequences. Our results confirmed that amino acid variation in SVR1 and SVR2 is limited, indicating that diversity in these regions may not be a source of serosubtype differences among strains (19). We have chosen not to incorporate SVRs and MAb P1.6 into our proposed scheme of designations at this time, even though we show that MAb P1.6 correlates with epitopes at SVR1. We and others believe that insufficient evidence to confirm their usefulness in epidemiologic investigation exists at this time (13, 19). PorA SVR typing may be valuable for comparative studies dealing with the complete PorA protein (8).Serosubtype-defining MAbs and PorA VR diversity. Epitope-mapping studies have shown that most of the epitopes recognized by serosubtype-defining MAbs are linear moieties located at the apex of either loop I (VR1) or loop IV (VR2) of PorA. This should, in theory, generate two potential serosubtype specificities within each class 1 protein (18, 19). In practice, many isolates remain non- or only partially serosubtypeable.
To further estimate the diversity of PorA VR types and correlate the types with the current serosubtyping MAb panel, we typed a total of 79 strains representing additional serosubtypes or additional isolates of a serosubtype and serotyping reference strains (Table 1). Our data demonstrate that this panel of 17 MAbs that define serosubtypes detects only 48% (n = 39 [of the total 81]) of known PorA VR types (12 types at VR1 and 27 types at VR2) and 50% (n = 17 [of the total 34]) of the PorA VR families (7 families at VR1 and 10 families at VR2) (Table 5). MAbs for 17 VR families are not available, and 13 VR family variants within some families are not recognized by the current panel of serosubtype-defining MAbs (Table 5). Furthermore, we demonstrated complete correlation between serosubtyping and PorA VR typing with no ambiguity. New serosubtype-defining MAbs may improve the sensitivity of this method by resolving a number of formerly nonserosubtypeable strains. Predicted PorA VR amino acid sequences can be used to make synthetic peptides as immunogens to prepare new MAbs tailored to regions where no MAbs currently exist. We estimate that approximately 30 additional new MAbs (for 17 families and 13 VR family variants) are needed to cover the diversity of PorA VR1 and VR2 so far characterized (Table 5). Surveillance will need to continue in order to detect the appearance of new variants. We propose to sequence the porA genes of strains thought to represent new serosubtypes and to compare the predicted PorA VR or SVR nucleotide sequences with those described in this article to avoid misinterpreted designations for new serosubtype-defining MAbs.Future directions in PorA characterization. The present work represents the most complete and integrated set of PorA VR sequences (n = 167) and MAb reactivities of meningococci produced to date and serves as a guide for nucleotide or amino acid VR classification. To our knowledge, this collection reflects the diversity of N. meningitidis PorA sequences to date.
This proposed standardization of PorA VR typing nomenclature unifies the system of designations for PorA VR typing while remaining consistent with previously described PorA and PorB VR typing nomenclature (13, 24, 29, 30). Our proposal for VR typing is informative because an amino acid sequence and usually serologic information can be deduced simultaneously from a PorA VR designation. Thus, historical epidemiologic serosubtyping data can be related to results of future studies that will use only the PorA VR typing method. Furthermore, new PorA VR types can be incorporated systematically. We recommend the continuation of serology as a screening method for PorA epitope characterization, particularly for screening large numbers of samples during epidemics or in field situations lacking specialized equipment. We have found the specificity of serosubtyping comparable to that of PorA VR typing. Strains that fail to react with any available MAb can be referred to specialized laboratories for determination of VR types by direct sequencing. In our hands, direct DNA sequencing produced no ambiguities in assignment of PorA type, unlike the situation described by Feavers et al. (13) in which DNA hybridization was used to estimate PorA diversity. PorA VR typing allows for a more systematic way to evaluate vaccine failures and provides a rational framework for understanding the mechanisms by which these vaccines confer protection, based on a knowledge of the primary sequences. PorA VR typing complements serosubtyping results, and a combination of both methods may be used to completely characterize potential PorA VR epitopes of meningococcal strains.| |
ACKNOWLEDGMENTS |
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We thank J. Suker of the NIBSC, L. O. Frøholm of the SIFF, W. D. Zollinger of the WRAIR, and J. T. Poolman of the NIPH for providing some of the MAbs and strains used in this work. We gratefully acknowledge the constructive criticism of E. Wedege.
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FOOTNOTES |
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* Corresponding author. Present address: Meningitis and Special Pathogens Branch, Mailstop D-11, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA 30333. Phone: (404) 639-2822. Fax: (404) 639-4421. E-mail: cls9{at}cdc.gov.
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REFERENCES |
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Top
Abstract
Introduction
Materials & Methods
Results & Discussion
References
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| 1. | Abdillahi, H., and J. T. Poolman. 1988. Definition of meningococcal class 1 outer membrane protein subtyping antigens by monoclonal antibodies. FEMS Microbiol. Immunol. 47:139. |
| 2. | Abdillahi, H., and J. T. Poolman. 1988. Neisseria meningitidis group B serosubtyping using monoclonal antibodies in whole-cell ELISA. Microb. Pathog. 4:27-32[Medline]. |
| 3. | Arhin, F. F., F. Moreau, J. W. Coulton, and E. L. Mills. 1997. Subtyping of Neisseria meningitidis strains isolated in Quebec, Canada: correlation between deduced amino acid sequences and serosubtyping techniques. Can. J. Microbiol. 43:234-238[Medline]. |
| 4. | Arhin, F. F., F. Moreau, J. W. Coulton, and E. L. Mills. 1998. Sequencing of porA from clinical isolates of Neisseria meningitidis defines a subtyping scheme and its genetic regulation. Can. J. Microbiol. 44:56-63[Medline]. |
| 5. | Barlow, A. K., J. E. Heckels, and I. N. Clarke. 1989. The class 1 outer membrane protein of Neisseria meningitidis: gene sequence and structural and immunological similarities to gonococcal porins. Mol. Microbiol. 3:131-139[Medline]. |
| 6. | Boslego, J., J. Garcia, C. Cruz, et al. 1995. Efficacy, safety, and immunogenicity of a meningococcal vaccine group B (15:P1.3) outer membrane protein vaccine in Iquique, Chile. Chilean National Committee for Meningococcal Disease. Vaccine 13:821-829[Medline]. |
| 7. | Brooks, J. L., E. Rosenqvist, G. Bjune, P. R. Lambden, and J. E. Heckels. 1994. Comparasion of the class-1 outer membrane protein from B:15:P1.16 Neisseria meningitidis strains isolated from patients previously immunized with a serogroup B outer membrane vaccine in Norway. Microb. Pathog. 17:425-430[Medline]. |
| 8. | Brooks, J. L., R. J. Fallon, and J. E. Heckels. 1995. Sequence variation in class 1 outer membrane protein in Neisseria meningitidis isolated from patients with meningococcal infection and close household contacts. FEMS Microbiol. Lett. 128:145-150[Medline]. |
| 9. | Butcher, S., M. Sarvas, and K. Runeberg-Nyman. 1991. Class-3 porin protein of Neisseria meningitidis: cloning and structure of the gene. Gene 105:125-128[Medline]. |
| 10. | Devereux, J. P., P. Haeberli, and O. Smithies. 1984. A comprehensive set of sequence analysis programs for the VAX. Nucleic Acids Res. 12:387-395. |
| 11. | Feavers, I. M., A. B. Heath, J. A. Bygraves, and M. C. J. Maiden. 1992. Role of horizontal genetic exchange in the antigenic variation of the class 1 outer membrane protein of Neisseria meningitidis. Mol. Microbiol. 6:489-495[Medline]. |
| 12. |
Feavers, I. M.,
J. Suker,
A. J. McKenna,
A. B. Heath, and M. C. J. Maiden.
1992.
Molecular analysis of the serotyping antigens of Neisseria meningitidis.
Infect. Immun.
60:3620-3629 |
| 13. | Feavers, I. M., A. J. Fox, S. Gray, D. M. Jones, and M. C. J. Maiden. 1996. Antigenic diversity of meningococcal outer membrane protein PorA has implications for epidemiological analysis and vaccine design. Clin. Diagn. Lab. Immunol. 3:444-450[Abstract]. |
| 14. | Frasch, C. E., W. D. Zollinger, and J. T. Poolman. 1985. Serotype antigens of Neisseria meningitidis and a proposed scheme for designation of serotypes. J. Infect. Dis. 7:504-510. |
| 15. | Guillen, G., A. Alvarez, G. Lemos, T. Paredes, R. Silva, and A. Mart. 1993. Comparison of the DNA sequence of nine different genes for the class 1 outer membrane protein from Neisseria meningitidis. Biotecnol. Apl. 10:108-113. |
| 16. | Hitchcock, P. J. 1989. Unified nomenclature for pathogenic Neisseria species. Clin. Microbiol. Rev. 2:S64-S65. |
| 17. | Maiden, M. C., J. Suker, A. J. McKenna, J. A. Bygraves, and I. M. Feavers. 1991. Comparison of the class 1 outer membrane proteins of eight serological reference strains of Neisseria meningitidis. Mol. Microbiol. 5:727-736[Medline]. |
| 18. |
McGuinness, B. T.,
A. K. Barlow,
I. N. Clarke,
J. E. Farley,
A. Anilionis,
J. T. Poolman, and J. E. Heckels.
1990.
Deduced amino acid sequences of class 1 protein (PorA) from 3 strains of Neisseria meningitidis: synthetic peptides define the epitopes responsible for serosubtype specificity.
J. Exp. Med.
171:1871-1882 |
| 19. | McGuinness, B. T., P. R. Lambden, and J. E. Heckels. 1993. Class 1 outer membrane protein of Neisseria meningitidis: epitope analysis of the antigenic diversity between strains, implications for subtype definition and molecular epidemiology. Mol. Microbiol. 7:505-514[Medline]. |
| 20. | Moraes, J. C., B. A. Perkins, M. C. C. Camargo, et al. 1992. Protective efficacy of a serogroup B meningococcal vaccine in São Paulo, Brazil. Lancet 340:1074-1078[Medline]. |
| 21. | Peeters, C. C. A. M., H. C. Rumke, L. C. Sundermann, E. M. Rouppe van der Voort, J. Meulenbelt, M. Schuller, A. J. Kuipers, P. van der Ley, and J. T. Poolman. 1996. Phase I clinical trial with a hexavalent PorA containing meningococcal outer membrane vesicle vaccine. Vaccine 14:1009-1015[Medline]. |
| 22. | Perkins, B. A., K. Jonsdottir, H. Briem, et al. 1998. Immunogenicity of two efficacious outer membrane protein-based serogroup B meningococcal vaccines among young adults in Iceland. J. Infect. Dis. 177:683-691[Medline]. |
| 23. | Rosenqvist, E., E. A. Høiby, E. Wedege, D. A. Caugant, L. O. Frøholm, B. T. McGuinness, J. Brooks, P. R. Lambden, and J. E. Heckels. 1993. A new variant of serosubtype P1.16 in Neisseria meningitidis from Norway, associated with increased resistance to bactericidal antibodies induced by a serogroup B outer membrane protein vaccine. Microb. Pathog. 15:197-205[Medline]. |
| 24. | Sacchi, C. T., A. P. S. Lemos, A. M. Whitney, C. A. Solari, M. E. Brandt, C. E. A. Melles, C. E. Frasch, and L. W. Mayer. 1998. Correlation between serological and sequencing analyses of the PorB outer membrane protein in the Neisseria meningitidis serotyping system. Clin. Diagn. Lab. Immunol. 5:348-354[Abstract]. |
| 25. | Saukkonen, K., H. Abdillahi, J. T. Poolmam, and M. Leinonem. 1987. Protective efficacy of monoclonal antibodies to class 1 and 3 outer membrane proteins of Neisseria meningitidis B:15:P1.16 in infant rat infection model: new prospects for vaccine development. Microb. Pathog. 3:261-267[Medline]. |
| 26. | Saunders, N. B., W. D. Zollinger, and V. B. Rao. 1993. A rapid and sensitive PCR strategy employed for amplification and sequencing of porA from a single colony-forming unit of Neisseria meningitidis. Gene 7:153-162. |
| 27. |
Saunders, N. B.,
B. L. Brandt,
R. L. Warren,
B. D. Hansen, and W. D. Zollinger.
1998.
Immunological and molecular characterization of three variant subtype P1.14 strains of Neisseria meningitidis.
Infect. Immun.
66:3218-3222 |
| 28. | Suker, J., I. M. Feavers, M. Achtman, G. Morelli, J.-F. Wang, and M. C. J. Maiden. 1994. The porA gene in serogroup A meningococci: evolution stability and mechanism of genetic variation. Mol. Microbiol. 12:253-265[Medline]. |
| 29. | Suker, J., I. M. Feavers, and M. C. J. Maiden. 1996. Monoclonal antibody recognition of members of the meningococcal P1.10 variable region family: implications for serological typing and vaccine design. Microbiology 142:63-69[Abstract]. |
| 30. |
Tsai, C. M.,
C. E. Frasch, and L. F. Mocca.
1981.
Five structural classes of major outer membrane proteins in Neisseria meningitidis.
J. Bacteriol.
146:69-78 |
| 31. |
van der Ley, P.,
J. E. Heckels,
M. Virji,
P. Hoogerhout, and J. T. Poolman.
1991.
Topology of outer membrane porins in pathogenic Neisseria spp.
Infect. Immun.
59:2963-2971 |
| 32. |
van der Ley, P.,
J. van der Biezen,
P. Hohenstein,
C. Peeters, and J. T. Poolman.
1993.
Use of transformation to construct antigenic hybrids of the class 1 outer membrane protein in Neisseria meningitidis.
Infect. Immun.
61:4217-4224 |
| 33. | Wedege, E., E. A. Høiby, E. Rosenqvist, and L. O. Frøholm. 1990. Serotyping and subtyping of Neisseria meningitidis isolates by co-agglutination, dot-blotting and ELISA. J. Med. Microbiol. 31:195-201[Abstract]. |
| 34. | Wedege, E., R. Dalseg, D. A. Caugant, J. T. Poolman, and L. O. Frøholm. 1993. Expression of an inaccessible P1.7 subtype epitope on meningococcal class 1 proteins. J. Med. Microbiol. 38:23-28[Abstract]. |
| 35. | Wedege, E., J. Kolberg, A. Delvig, E. A. Høiby, E. Holten, E. Rosenqvist, and D. A. Caugant. 1995. Emergence of a new virulent clone within the electrophoretic type 5 complex of serogroup B meningococci in Norway. Clin. Diagn. Lab. Immunol. 2:314-321[Abstract]. |
| 36. | Wedege, E., D. A. Caugant, and W. D. Zollinger. 1996. P1.19 specificity of a previous P1.15 reference monoclonal antibody demonstrated by blotting methods, porA sequencing and peptide mapping, abstr. 202, p. 538. In Abstracts of the Tenth International Pathogenic Neisseria Conference 1996. |
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