De Meio and Walker were the first who recognized the antibody elevation against Sendai virus with mumps infections. The work to be reported here was conducted one to confirm their results and another to test the usefulness of soluble antigens of respective virus in serodiagnosis, in an effort to differentiate these two kind of infections.
The results obtained so far will be summarized as follows:
1) From 19 mumps children living in Sendai, paired serum specimens were obtained and tested for their antibody titer by means of hemagglutination inhibition (HAT) and complement fixation tests (CFT) with both viral and soluble antigens of respective virus. Antibody elevation in HAI as well as in CFT-V and-S was evident with all of these pairs, when mumps virus (Habel strain) was used as antigen.
2) When these paired specimens were tested with antigens of Sendai virus, significant elevation of HAI titer was shown with 7 pairs (37%). However total 13 pairs among 19 (68%) revealed the positive HAI titer against Sendai virus including the pairs with a little or no elevation. The fact may suggest the possibility that mumps virus antigen is highly related to that of Sendai virus, particularly in HAI test. The fact that even in acute phase, some patients revealed HAI antibody titer against Sendai virus comparative to or higher than the titer against mumps virus was the main interest here evoked. Parallel elevation against heterologus antigen here pointed out, however, did not hold true with all of the tested pairs. Elucidation of this fact was left in a future.
3) With complement fixation test using antigens derived from Sendai virus, some cross reaction was also observed at least when V antigen was used. But the correlation rate with mumps antigen was rather low when compared to the result obtained in HAT test.
4) Any specimens examined here did not reveal antibody titer against soluble antigen of Sendai virus. This fact was thought to be useful, in differentiating mumps patients from infection of Sendai virus.

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To test the possibility of recent outbreak of Sendai virus infections among the population of Sendai, this serological survey was intended. Proposal of the work was originally made from the result reported in the previous paper, where most sera obtained from mumps patients at acute stag revealed high antibody titer against Sendai virus when tested in hemagglutination inhibition reaction.
An explanation of the fact was the shared antigen between these 2 viruses. An alternative idea was the anamestitic elicitation of Sendai virus antibody with mumps virus. However, both possibilities may finally lead to the same conclusion of shared antigen.
Serum specimens were obtained from 260 healthy people in Sendai and divided into two groups, i.e. one of children under 15 years, another of adult over 16 years old. The results obtained so far revealed the following conclusion.
1) 73% of children and 89% of adult did not have any antibody titer against Sendai virus when examined on hemagglutination inhibition test.
2) High distribution of antibody was found only among children between 4 and 10 years old. Antibody titer of these specimens was also high.
3) From 71 healthy children of 6 years old, new serum specimen were obtained to test the cross relationship of Sendai virus with mumps virus. 52% of the tested specimens had the titer against Sendai virus and 82% against mumps virus. Among 37 specimens positive against Sendai, 36 specimens (97%) had the significant titer against mumps virus. Whereas among 58 specimens positive agaiast mumps, 36 (62%) was positive against Sendai virus. Taken together, HAI titer revealed here against Sendai virus was anticipated to have the character provoked by mumps virus. However, critical analysis of this observation was left for further studies

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Common antigens shared by Sendai and mumps viruses was suggested in the former two experiments, where the first observation was made with clinical materials obtained from mumps patients and the second one was obtained in the field serological survey. Then the third experiment was conducted here in experimental animals, where antibody responses of both chicken and guinea pig against both Sendai and mumps viruses were examined every week for 5 weeks. In chicken, single intravenous administration was the choice of immunization procedure and obtained specimens were examined for their antibody titer on hemagglutination inhibition (HAI) and neutralization tests. In guinea pigs, the inoculum virus was given by instillation and the serum drawn every week was tested in HAI and complement fixation tests (CFT) with both viral and soluble antigens of each virus.
Obtained results will be summarized as follows:
1) In chicken, when mumps virus was used as an immunogen, antibody response against homologous virus was obtained in a uniform fashion with all tested chickens. Whereas one out of three, revealed parallel antibody shift against Sendai virus. In this case antibody titers were proved both in HAI and neutralization tests. When Sendai virus was used as an antigen, HAI titer against mumps virus was elicited with all three chickens examined so far.
2) In guinea pigs, when mumps virus was used for intranasal inoculation. HAI titer against Sendai virus as well as against homologous virus was proved with tested 4 guinea pigs. However, in CFT, no heterologous antibody was provable. On the other hand, when Sendai virus was used as an immunogen, any response against mumps virus was not provable.
In summary, shared antigenicity was provable between these two viruses not only with human specimens but also in animal experiments.

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Six viral agents were isolated in cultures of bovine embryonic renal cells from feces of apparently healthy cattle. These agents were concidered to represent strains of a single virus. The properties of the virus are as follows:
(1) The virus proliferates with cytopathogenic effect in cultures of kidneys, spleens, testicles, and ovaries of cattle, kidneys and lungs of bovine embryos, kidneys of pigs, rabbits, and guinea pigs, chicken embryo tissues, and HeLa cells. However, the virus demonstrates neither evidence of multiplication nor cytopathogenesis in cultures of horse, dog, and cat kidney cells.
(2) The virus is readily filtered through Berkefeld N and W.
(3) The virus is not completely inactivated by heating at 56°C for 120 minutes or at 60°C for 60 minutes, but its infectivity is completely lost at 65°C in 20 minutes.
(4) Storage at 37°C inactivated the virus in 42 days. The virus is very stable when stored at 4°, -20° or -80°C.
(5) Infectivity of the virus is maintained unchanged when the virus is frozen and thawed ten times.
(6) The virus is resistant to ethylether and trypsin.
(7) Infected materials are capable of agglutinating erythrocytes of sheep and horses at 4°C
(8) The virus has little clinical effect on suckling mice, but is serially maintained by intracerebral passages in this host.
(9) The virus has no pathogenecity to adult mice, and guinea pigs. Chicken embryos seem to support the virus multiplication but no pathological lesions are produced.
(10) Calves inoculated with the virus intracerebrally, intratracheally, intravenously, intraperitoneally, or perorally showed no clinical signs. However, further studies seem necessary regarding the pathogenecity of the virus in cattle.
(11) The six isolates are not distinguishable from each other by neutralization test. The virus shows no cross reaction in neutralization test with ECBO virus of Kunin and Minuse.
We have been unable to relate this virus to presently known viruses recovered from cattle and believe that it represents a hitherto undescribed virus. Hence, we designated it tentatively as the BF 1 virus. A wide dissemination of the virus among Japanese cattle was indicated by high incidence of neutralizing antibodies for BF 1 virus; 12% of 49 Holstein cattle in Hokkaido Pref., 71% of 31 cattle of Japanese breed in Shimane Pref., and 94% of 16 Jersey cattle inported from Australia had neutralizing antibodies.

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BF 1 virus was found to have activity of hemagglutination (HA) and various conditions involved in the reaction and properties of agglutinin were investigated.
(1) Culture fluids obtained from bovine kidney, porcine kidney and chick embryo tissue cultures infected with this virus show hemagglutination.
(2) The viral materials agglutinates erythrocytes of the sheep and horse at 4°C in Ringer solution, but no agglutination is observed with erythrocytes of the cattle, pig, goat, guinea pig, rat, mouse, rabbit, pigeon and chicken.
(3) HA reaction occurs in a very low titer in physiologic saline or that buffered with phosphate or McIlvaine buffer. HA reaction is of very high titer in solutions of divalent cations such as those of CaCl₂. MgCl₂ or BaCl₂, while no reaction is observed in solutions of NaCl, LiCl or KCl. The highest titer is obtained with horse blood cells in solutions of divalent cations such as CaCl₂. The optimal concentration of CaCl₂ is 0.1M and this concentration can be reduced to 0.05M if NaCl is added to maintain the solution isotonic.
(4) The optimal pH is 8.0-6.0 in Ringer solution and 7.2-6.0 in CaCl₂ solution.
(5) The optimal temperature is 4°C. The titer of the reaction is very low at room temperature and no reaction occurs at 37°C.
(6) HA titer is inversely proportionate to concentration of erythrocytes.
(7) hemagglutinin is adsorbed on to erythrocytes within 10 minutes at 4°C in Ringer or CaCl₂ solution, and about 50% of adsorbed hemagglutinin is eluted from cells at 37°C in Ringer or CaCl₂ solution. Elution takes place when completely agglutinated cells are kept at 4°C in KCl or NaCl solution. Elution takes place slowly in about 2 hours.
(8) Since under the same condition virus infectivity is likewise adsorbed on to and eluted from erythrocytes, there may be a possibility that the agglutinin and infective particle represent a single particle, but this is to be determined.
(9) Alternate repetition of adsorption at 4°C and elution at 37°C exerts no changes in agglutinative abilities of erythrocytes and hemagglutinin.
(10) Hemagglutinin is rather heat-resistant; no reduction of activity takes place by heating at temperature equal or lower than 65°C for 24 hours. Complete inactivation occurs within 3 hours at 70°C, within 5 minutes at 100°C. Hemagglutinin resists to ultraviolet irradiation and treatment with ethylether (50%, 4°C, 24 hours). Trypsin (1%, 37°C, 60 minutes, pH 7.2) seems to inactivate some what hemagglutinin.
(11) In infectivity titration of the virus in cell cultures, hemagglutinin is produced in all the tubes showing cytopathogenesis, while no hemagglutinin is detected in tubes with no cytopathogenesis.
(12) In cultures of bovine embryo kidney infectivity begins to increase in 6 hours and reaches the maximum titer in 36 hours. hemagglutinin is first detectable about 24 hours after inoculation and its titer increases rapidly in parallel to infective titer, reaching at the peak 36 hours after inoculation.
(13) HA reaction is specifically inhibited by immune serum for BF 1 virus. Non-specific inhibitor in bovine sera can be eliminated by aceton treatment.

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An outbreak of an acute respiratory infection with fever of short duration and nasal secretion occurred among colts at a farm in Aomori Prefecture, Japan.
Nasal secretions obtained from 19 sick colts were inoculated into horse kidney cell cultures and 12 viral strains of the same properties including antigenicity were isolated. Increase in titers of complement fixation and neutralization against the isolated virus as well as the Kentucky D strain of equine abortion virus was clearly demonstrated after the illness in all of the colts from which the materials for virus isolation were obtained.
These isolated agents were considered to be equine abortion virus on the bases of formation of intranuclear inclusions in horse kidney cells in culture, physico-chemical properties, behavior in various cell cultures and complement fixation reaction. However, the isolates, as, the H-45 strain isolated from aborted fetus in Hokkaido, Japan, were found to differ from the Kentucky strain isolated in U.S.A; The isolated and the H-45 strain could be readily differentiated by neutralization test from the American strain, although some cross-reaction was noted, and failed to infect hamsters.
These findings provide etiological evidence for the presence of respiratory infection with equine abortion virus among Japanese colts.

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