Characterization of the Measles Virus Isolated from the Brain of a Patient with Immunosuppressive Measles Encephalitis

Two strains of measles virus with different biologic properties were isolated from the brain of a patient with immunosuppressive measles encephalitis. One strain (Oita-l) grew extremely slowly in Vero cells and did not produce any cell-free virions. The other strain (Oita-2) replicated well, and a small amount of cell-free virus was detected from the culture medium and the freeze-thawed homogenate. Neurovirulence of the Oita-l strain to mice was, however, stronger than that of the Oita-2 strain. Synthesis of the M protein by the Oita-Z strain was not demonstrable in the infected cells when they were labeled for 24 hr; however, a new protein moiety that was smaller in molecular weight than the M protein and that was not precipitated with monoclonal antibody to M protein was demonstrated by pulse-labeling for I hr. Antibodies to the M protein, as well as to other proteins, were detected (by immunoprecipitation) in the serum and cerebrospinal fluid of the patient.