An epidemic of hand, foot and mouth disease (HFMD) occurred in Gifu Prefecture in 1973. Virological and serological investigation were performed.
Those involved ranged from 0 to 23 years of age, and 71.4% of them were under 4 years. Symptoms of the central nervous system (CNS) were observed concomitantly in 20 of 42 cases.
Viruses were isolated from 22 of 38 cases (57.9%). The types of isolated viruses with the number of cases of isolation are as follows: enterovirus 71 (16 cases; 42.1%), Coxsackievirus (Cox.) B5 (8 cases; 21.1%), Cox. A9 (2 cases; 5.2%), and unidentified virus (one case; 2.6%). Cox. A16 was not isolated at all. Eighteen strains of enterovirus 71 were isolated in Vero cells. One strain was isolated in suckling mice. The viruses isolated from cases of HFMD with CNS symptoms were identified as enterovirus 71 and Cox. B5.
In the cross-neutralization test, the isolated strains of enterovirus 71 showed a cross reaction to the prototype strain of enterovirus 71, but were antigenically broader than this strain. They showed no cross reaction to the prototype strain of Cox. A16.
A significant rise of neutralization antibody titer was found in 25% of 24 cases against enterovirus 71, 13% of 23 cases against Cox. B5, 4% of 24 cases against Cox. A 16, and 17% of 6 cases against Cox. A9.
It was supposed that the main causative agent of HFMD epidemic in Gifu Prefecture in 1973 might be enterovirus 71. The roles of the other viruses isolated, however, can not be neglected in the etiology of HFMD.

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Rubella-specific IgM antibody in the serum of patients with natural rubella was investigated by the absorption of IgG with Staphylococcus aureus Cowan 1 (S. aureus) reported by Ankerst et al. and by sucrose density gradient centrifugation. The method of detection of rubella-specific IgA antibody was studied by a combination of the two methods mentioned above.
The present investigation confirmed that serum IgG was specifically removed by the absorption with S. aureus, but that an excess amount of S. aureus removed IgM and IgA nonspecifically from serum. An adequate amount of S. aureus that could remove most IgG from serum without affecting the IgM and IgA content was 0.1g (wet volume) in 0.3ml of serum diluted 1:8 with kaolin treatment or 0.2g of S. aureus in 0.3ml of serum diluted 1:8 without kaolin treatment.
Rubella HI antibodies were not demonstrated after the absorption with S. aureus in the serum of subjects having suffered from infection more than 5 years before, but in the serum of subject having recent infection, i.e., the serum obtained during a period from 3 to 115 days after the onset of rash. These results were coincident with the presence of rubella-specific IgM HI antibodies demonstrated by sucrose density gradient centrifugation. Rubella-specific IgA HI antibody in serum could be estimated by the fractionation of sucrose density gradient centrifugation after the absorption with S. aureus.

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It is of great importance to determine by immunological methods whether pregnant women had a recent or a remote rubella infection. In the previous report the presence of rubella-specific IgM antibody was suggested to indicate a recent rubella infection. The persistence of the specific IgM antibody, however, was not sufficiently clarified.
In the present study 374 serum specimens were obtained from 137 cases over a period of 540 days after the onset of rubella rash. They were tested for rubella-specific IgM plus IgA HI antibodies, IgM antibodies, and IgA antibodies by using the staphylococcal absorption method, fractionation by sucrose density gradient centrifugation, and a combination of both methods mentioned above, respectively. Specific IgM and IgA antibodies appeared in the acute stage of rubella. IgM antibody persisted for 10 months and IgA antibody up to one year and a half after infection. In some cases both antibodies disappeared 3 months after infection.
The interpretation of the residual rubella HI antibody titers in the serum after absorption with S. aureus was as follows: Titers of 1: 32 and higher indicated a recent infection within 3 months, but any titer of less than 1:8 did not. Titers of 1:8 and 1:16 did not explain the time of infection. Specific JgM and IgA antibodies appearing after natural rubella infection persisted longer than those reported previously. So that for the serological diagnosis the efficacy of the staphylococcal absorption method was limited to the detection of a recent rubella infection.

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Gp70-related molecules in the serum were heavily deposited in the lupus kidney and vascular lesions as an immune complex in New Zealand mice. They were characterized biochemicallyby using affinity chromatography and SDS-PAGE analysis. Isolated gp70-related molecules in the serum consisted of three glycoprotein fragments with an approximate molecular weight of 53, 000, 45, 000 and 32, 000 daltons, respectively. In contrast, gp70 isolated from the cell surface affected with mouse leukemia, E_??_G₂, was shown to be a single glycoprotein molecule with a molecular weight of approximately 70, 000 daltons.
The major gp70 activity in the serum fractionated by Sephadex gel filtration was found to be in a range of molecular weight from 120, 000 to 140, 000. The minor gp70 activity was found to be of the same size as serum albumin. All the results obtained suggest that the three glycoprotein fragments of serum gp70 described in this study might have resulted either from specific transcriptional, translational, or post-translational process, or from nonspecific proteolysis at susceptible sites. It is possible that a gp70-related molecule in the serum may be a specific envelope-related glycoprotein which consists of three glycoprotein fragments with a molecular weight of 53, 000, 45, 000 and 32, 000 daltons, respectively. The alternative is that serum gp70 may be either associated with host cellular components or present as a dimer.
Pooled B/WF₁ mouse sera from 2 age groups were fractionated by Sephadex gel filtration. The major gp70 activity of 2-month-old B/WF₁ serum was found in fractions with a molecular weight in a range from 120, 000 to 140, 000 daltons. In contrast, the gp70 activity of 9-month-old B/WF₁ serum eluted for the most part at the void volume. The ¹²⁵I-labeled gp70-anti-gp70 immune complex prepared in vitro eluted also at the void volume. It was suggested that gp70-related molecules in the serum of aged B/WF₁ mice were present largely as immune complexes.
In attempts to identify directly the molecule(s) bearing the antigenic determinants for endogenous antibody to MuLV, or Gross natural antibody (GNA), ¹²⁵I-E_??_G₂ MuLV proteins were subjected to immunoprecipitation with GNA-positive mouse sera. SDS-PAGE analysis of the resulting precipitates revealed that the major molecule bearing antigenic determinants for GNA is p (85), the precursor polyprotein of the MuLV core structural proteins, p 30, p 15, and p 10.

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