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Immunological and molecular characterization of three variant subtype P1.14 strains of Neisseria meningitidis
N B Saunders1, B L Brandt, R L Warren
1Department of Bacterial Diseases, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA. Dr._Nancy_Saunderss@wrsmtp-ccmail.army.mil
Abstract:
Epidemic outbreaks of group B meningococcal disease exhibit a clonal nature consisting of a common serotype-subtype. Subtype-specific monoclonal antibodies (MAbs) directed toward two variable regions (VR1 and VR2) of the class 1 protein of Neisseria meningitidis are used in this classification scheme. A new MAb was developed to classify a nonsubtypeable (NST) strain of N. meningitidis, 7967. This MAb bound to both the NST strain and the prototype subtype P1. 14 strain, S3446, by dot blot analysis. However, a MAb produced to the prototype P1.14 strain did not bind to strain 7967. Sixteen additional strains were further identified as P1.14 with the prototype MAb; of these, 15 strains bound both MAbs. Differences in the characteristics of binding of both antibodies to the three apparently diverse P1.14 strains were studied further by using outer membrane complex proteins, immobilized peptides, and soluble peptides. Deduced amino acid analysis suggested that both MAbs bind to VR2 and that single amino acid changes within VR2 (KM, NM, or KK) might explain the differences in binding characteristics. These results demonstrated that minor variations which exist within subtype variable regions may be clearly identified only by a combination of molecular and immunologic testing. The impact of subtype variation will become more evident as subtype-specific vaccines are developed and tested for efficacy.
Insights
Minor variations in Neisseria meningitidis subtypes can be identified using combined molecular and immunologic testing. This is crucial for developing effective subtype-specific vaccines against group B meningococcal disease.
Area of Science:
- Microbiology
- Immunology
- Vaccinology
Background:
- Epidemic outbreaks of group B meningococcal disease are often clonal, defined by serotype-subtype.
- Subtype classification relies on monoclonal antibodies (MAbs) targeting variable regions (VR1, VR2) of the Neisseria meningitidis class 1 protein.
Purpose of the Study:
- To develop and characterize a new MAb for classifying a nonsubtypeable (NST) strain of N. meningitidis.
- To investigate minor variations within the P1.14 subtype and their impact on MAb binding.
Main Methods:
- Dot blot analysis using a novel MAb against NST strain 7967 and prototype P1.14 strain S3446.
- Binding assays with outer membrane complex proteins, immobilized peptides, and soluble peptides.
- Deduced amino acid analysis of variable regions.
Main Results:
- A new MAb bound to both NST strain 7967 and prototype P1.14 strain S3446.
- Most P1.14 strains (15/16) bound both the prototype MAb and the new MAb.
- Single amino acid changes (KM, NM, KK) within VR2 likely explain differential MAb binding characteristics.
Conclusions:
- Minor variations within N. meningitidis subtype variable regions require combined molecular and immunologic testing for accurate identification.
- Understanding these variations is critical for the development and efficacy testing of subtype-specific vaccines.