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Background: The antivirally active MxA protein is induced by interferon (IFN) alpha/beta and inhibits the replication of single-stranded RNA viruses including measles virus (MV). The authors investigated whether the MxA gene contributed to the development of subacute sclerosing panencephalitis (SSPE) in Japanese individuals., Methods: Single-nucleotide polymorphisms (SNP) in the promoter region of the MxA gene were screened, association studies were performed between two SNP and SSPE, and then a functional difference in the promoter activities of the two SNP was investigated by a dual luciferase reporter assay., Results: Four SNP were found (-88 G/T, -123 C/A, -200 T/C, and -213 G/T), and SSPE patients exhibited a higher frequency of both the -88T allele and the -88TT genotype than controls (p = 0.040 and 0.003). The IFN-induced up-regulation of the MxA promoter activity of the sequence with -88T was found to be significantly higher than that with G., Conclusions: MxA promoter -88 G/T SNP may confer host genetic susceptibility to SSPE in Japanese individuals. The finding that homozygotes of the MxA -88T allele with a high MxA-producing capability were more frequently seen in SSPE patients suggests that the MxA protein promotes the establishment of persistent MV infection of neural cells.

We determined the nucleotide sequence of the fusion (F) gene of three strains (Osaka-1, -2, and -3) of nonproductive variants of measles virus (MV). These viral strains were isolated in Osaka, Japan, from brain tissues of patients with subacute sclerosing panencephalitis (SSPE). Phylogenetic analysis revealed a close relationship among the three strains of SSPE virus. The cytoplasmic tail of the F protein, predicted from sequence analysis of the gene, is altered in all three SSPE strains when compared to the MV field strains. However, the extent and mode of alteration are different in each strain. The F protein of the Osaka-1 strain has six nonconservative amino acid substitutions and a 29-residue elongation of its cytoplasmic tail. The F protein of the Osaka-3 strain has two nonconservative substitutions and a 5-residue truncation of its C-terminus. Although the termination codon is not altered in the F protein of the Osaka-2 strain, five or six amino acids are changed in the cytoplasmic tail of the F protein of the two sibling viruses of this strain. The significance of the altered cytoplasmic domain of the SSPE viruses in the SSPE pathogenesis is discussed.

The nucleotide sequences of nucleocapsid (N), phosphoprotein (P), matrix (M), fusion (F), and large protein (L) genes were partly determined for 19 wild strains of measles virus (MV) isolated over the past 10 years in Japan (nucleotide position N: 1301-1700, P: 1751-2190, M: 3571-4057, F: 6621-7210, L: 10381-11133) and also for a MV strain obtained from a patient with subacute sclerosing panencephalitis (SSPE) who had natural measles in 1980. The phylogenetic trees of these strains drawn for respective genes were very similar to each other and revealed that all the wild strains were classified chronologically into 3 subgroups, those isolated in 1984, 1984-1989, and 1990-1994. The SSPE strain was classified into the subgroup of 1984. Phylogenetic tree analyses including other strains in the world revealed that Japanese strains in 1984 were classified into a distinct lineage which might correlate with the European strains from late 1970s to mid 1980s. Japanese strains from 1984 to 1989 were almost identical to those of the United States isolated from 1989 to 1992, and Japanese strains in 1990s were related closely to some of the MV strains isolated in 1994 in the United States. Genetic recombination among the MV genes seemed not to have occurred.

We determined the nucleotide sequences of the coding region for the M gene in seven strains of measles virus (MV) that were isolated in Japan between 1984 and 1993. The mutation found among the seven differed from those of laboratory strains. Many of these mutations were the same as those that are characteristic of SSPE viruses. Thus, we suggest that the mutations that have been considered specific to SSPE virus are in fact consensus among prevailing MV.

A simple and sensitive method for the detection of measles virus genome was developed, amplifying the regions encoding the nucleocapsid (N) protein and hemagglutinin (H) protein of measles virus by reverse transcriptase-polymerase chain reaction (RT-PCR). We examined a variety of measles patients: 28 patients with natural infection, 4 with measles encephalitis and 1 with subacute sclerosing panencephalitis (SSPE). In 28 patients with natural measles infection a single step PCR amplifying the N region resulted in a high detection rate for all plasma samples (28/28) within 3 days of the onset of rash and 80% (20/25) even on day 7 of the onset of rash and later. Within 3 days of the onset of rash, 24/25 (96.0%) of nasopharyngeal secretions (NPS) and 27/28 (96.4%) of peripheral blood mononuclear cells (PBMC) were positive for the N region PCR and the positivity rate of PCR decreased in NPS and PBMC after 7 days of the rash. In acute measles infection, measles genome was detected in all cell fractions, CD4, CD8, B cells, and monocytes/macrophages by the H gene nested PCR. Measles genome was also detected from cerebrospinal fluids (CSF) in patients with measles encephalitis, SSPE, and acute measles by the H gene nested PCR. PCR products of the N and H regions were sequenced and we confirmed the presence of measles genome. Based on the sequence data, chronological sequence differences were observed over the past 10 years. The sequences obtained from the SSPE patient were closely related to those of the wild viruses that were circulating at the time when the patient initially acquired measles. RT-PCR for NPS, PBMC, CSF, and plasma provides a useful method for the diagnosis of measles and molecular epidemiological study in addition to virus isolation.