Variability of Low-Molecular-Weight, Heat-Modifiable Outer Membrane Proteins of Neisseria meningitidis

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Abstract
Analysis of major outer membrane protein (MOMP) profiles of various meningococci by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of 0-2 low MW, heat-modifiable MOMP (MW, 25,000-32,000) and 1-3 high MW MOMP (MW, 32,000-46,000). Heat modifiability was investigated by comparing MOMP profiles after heating in SDS solutions at 100.degree. C for 5 min or at 40.degree. C for 1 h. Low MW MOMP shifted to higher apparent MW after being heated at 100.degree. C. Heat modifiability of high MW MOMP varied among strains; whenever modified these proteins shifted to lower apparent MW after complete denaturation. Variability of low MW, heat-modifiable MOMP was demonstrated when MOMP profiles were compared of isolates from index cases and associated cases and carriers among contacts, different isolates from the same individual, and isolates from a small epidemic caused by serogroup W-135. In some cases high MW MOMP revealed quantitative differences among related strains. The observed variability and quantitative differences indicate that MOMP serotyping and typing on the basis of SDS-PAGE profiles (PAGE typing) need careful reevaluation.