Properties of virus associated with subacute myelo-optico-neuropathy

Reappraisal of modified neutralization test for Inoue-Melnick virus

Ito et al. (1992) reported an improved modification of the neutralization (NT) test for Inoue-Melnick Virus (IMV) by prolonged 90 min incubation of the mixture of the virus and serum. For confirmation, we compared the results of the NT test by 90 and 60 min incubation. Against human sera, the NT test by 90 min incubation was significantly more sensitive than the test by 60 min incubation. By 90 min incubation, the NT titers increased by 3 to 6 times and approximately 6% of antibody-negative adult sera previously determined in the tests by 60 min incubation turned to positive (more than 1:10). However, antibody-negative sera of Japanese children examined previously in the tests by 60 min incubation remained negative after the 90 min tests. On the other hand, against rabbit immune sera, no significant difference of NT titers was observed between the two NT tests for 90 and 60 min incubation. Also we reinvestigated Japanese adult sera for type 2 IMV infection by the NT test for 90 min incubation, but did not find any serum of type 2 or intermediate type infection. Therefore, it is not necessary to change the previous conclusion that in Japan IMV infections are mostly of type 1.

Direct isolation of Inoue-Melnick virus from human colorectal carcinoma tissues but not from stomach carcinoma tissues

Inoue-Melnick virus (IMV) was isolated directly from all of the seven human colorectal adenocarcinoma tissues studied, whereas IMV was not isolated from five human stomach carcinoma tissues. Seven isolates from the Japanese colorectal carcinoma tissues were identified as type 1 IMV by the neutralization test and were sensitive to phosphonoacetic acid, a growth inhibitor of IMV. Furthermore, type 1 IMV-antibody was detected in six of seven sera of the patients whose colorectal carcinoma tissues were positive for virus isolation. In contrast, IMV-antibody was not detected in the five sera of the patients whose stomach carcinoma tissues were tested and found negative for IMV.

Endogenous production of infectious Inoue-Melnick virus in a human meningioma cell line

We investigated continuous production of Inoue-Melnick virus (IMV) in the MG-1 cell line, established from human meningioma. The infectious virus, identified as a type 1 virus, was mostly recovered extracellularly. Assay of MG-1 cells as infective centers indicated that most of the cells were capable of producing infectious virus. By immunofluorescence, more than 90% of the cells were found to have IMV-associated cytoplasmic antigen(s) (IMCA).

Factors influencing the assay of Inoue-Melnick virus

We describe factors influencing the assay of Inoue-Melnick virus (IMV) and practical comments for its assay. MRC-5 cells at a population doubling level (PDL) of more than 32 were more sensitive than younger cells for demonstrating cytopathic effect (CPE) of the virus. The PDL of MRC-5 cells also influenced the virus yield, particularly when the amount of viral inoculum was small. Cells at younger PDL produced less virus. The appearance of CPE and the virus yield were inhibited by increasing the concentration of NaHCO3 to 0.14% in the maintenance medium. The release of the virus into the medium was also inhibited as NaHCO3 was increased.

Inhibitory effect of acyclovir on the growth of Inoue-Melnick virus isolated from cerebrospinal fluid

Inoue-Melnick virus (IMV) was isolated from the cerebrospinal fluid of patients with chronic neurologic disorders. The effect of acyclovir (ACV), 9-(2-hydroxyethoxymethyl)-guanine, on the growth of IMV was studied in human diploid cell cultures. ACV markedly inhibited the multiplication of all three IMV serotypes in vitro with the same inhibitory effect. By passage of IMV in the presence of ACV in the medium, ACV-resistant mutants of three IMV serotypes were easily isolated.

Characterization of IM virus, which is frequently isolated from cerebrospinal fluid of patients with multiple sclerosis and other chronic diseases of the central nervous system

A transmissible agent, the IM virus, antigenically related to the Japanese subacute myelo-optico-neuropathy virus, has been isolated from several human cerebrospinal fluids obtained from American patients with multiple sclerosis and other chronic diseases of the central nervous system. The isolates were propagated in human diploid fibroblast (MRC5) cells, and virus was released into the culture medium in the absence of overt cytolysis. Infection of MRC5 cells resulted in a subtle alteration in the normal growth pattern of the cells. In unstained cultures, the cell changes were so mild that it was necessary to carry out all virus assays under code to eliminate bias. Cells in late passages were more susceptible than vigorously growing cells in early passages. Analysis of the kinetics of replication revealed that newly synthesized progeny virus was first detected about 12 h postinfection, that maximal virus release occurred by 48 h postinfection, and that virus production was persistent throughout an 8-day period. Several inhibitors of DNA synthesis were effective in blocking viral replication, including cytosine arabinoside, iododeoxyuridine, and phosphonoacetic acid. A substantial decrease in infectivity was observed upon treatment of IM virus with ether, suggesting that a lipid-containing structure is essential for infectivity. Ultrafiltration studies approximated the size (diameter) of IM virus to be between 100 and 200 nm.

Classification of Inoue-Melnick virus into three antigenic types

Antigenic analysis of Inoue-Melnick virus, formerly called SMON virus, showed that isolates from patients with subacute myelo-optico-neuropathy (SMON) in Japan, thus far tested, belonged to a single antigenic type (type 1). However, Inoue-Melnick virus isolates obtained so far in the United States chiefly from patients with multiple sclerosis could be classified into three types: type 1, type 2, and an intermediate type. At the present state of knowledge, the virus has not been proven to be the causative agent of disease, hence its provisional designation as IMV.

Effects of phosphonoacetic acid on subacute myeloopticoneuropathy virus in vitro and in vivo

The effect of phosphonoacetic acid (PAA) in vitro and in vivo on subacute myeloopticoneuropathy (SMON) virus isolated from the spinal fluid of SMON patients was studied. PAA inhibited multiplication of SMON virus in cultures, but it did not show a direct effect on the virus. The drug did not influence the disease when the medication was started from 10 days after infection of suckling mice. However, the drug did elicit a delay in the incubation period.