Sequence variation in class 1 outer membrane protein in Neisseria meningitidis isolated from patients with meningococcal infection and close household contacts.

The meningococcal porA gene encodes the class 1 outer membrane protein which contains the VR1 and VR2 regions responsible for sero-subtype specificity. However, sequence variations may occur within these regions which are not recognised by the currently available subtype antibodies. Since this "silent" microheterogeneity represents a potential hidden source of information, in the current study we have used porA gene sequence analysis to study strains isolated from cases of meningococcal infection and close household contacts. With each of the three subtypes studied, the index cases could be differentiated from each other by sequence variations within at least one of the VR1, VR2 and SV1 regions. In addition, although isolates from close household contacts showed a high degree of homology significant differences could be detected within some family groups. These data demonstrate that it is possible to use sequence information to differentiate between potential sources of infection which appear identical using conventional serological methods.