Antigenic relationship between the Tokyo and the Miami strains of equine influenza subtype 2 virus.
Abstract: The first outbreak of equine influenza (EI) infection in Japan was recognized during the period December 1971 to January 1972 [1, 6]. No evidence of the disease had been found before then [2,6]. The etiological agent of this epizootic was identified by hemagglutination-inhibition (HI) and neutralization tests with chicken or ferret antiserum as the subtype 2 of EI virus (6, 7). However, the isolate, A/equine/Tokyo/71 (Tokyo) strain, was not completely identical to the prototypic A/equine/Miami /63 (Miami) strain of the subtype 2, since antibody responses of convalescent horses were 2 to 16 times higher against Tokyo strain than against Miami strain used in the HI tests [6, 7]. The same phenomenon was also demonstrated on the EI virus (Heq2 Neq2) strain isolated during the course of epizootics occurred in Brazil in 1969, by means of the HI tests with postinfection horse sera. At that time it was reported that a significant antigenic drift might have occurred within the EI subtype 2 viruses [9]. In the present study, the antigenic relationship between the Tokyo and Miami strains was assessed by cross HI tests with antisera of the immunized rabbits with these strains.
The A/Hong Kong/68 strain of human influenza virus is also included for comparative purposes because of its well-known close relation of antigenicity of the subtype 2 of EI virus [4, 5].
HI test was performed by microtiter method using a 2-fold dilution of serum, 8 hemagglutinating units of virus antigen in 0.025 ml each, and 0.5% chicken erythrocytes in 0.05 ml volume. The serum samples used for the test were treated with M/60 potassium periodate (1.5 volumes: 1 volume of inactivated serum at 56°C for 80 minutes) at 20°C for 1 hour, and excess periodate was neutralized with 6% glycerol saline (0.5 volume) at room temperature for 30 minutes. An additional treatment was performed with commercial Receptor Destroying Enzyme concentrated 8 times (1 volume: 3 volumes of periodate-treated serum) at 37°C overnight. The treated serum was inactivated again at 56°C for 30 minutes and absorbed with chicken erythrocytes to remove natural agglutinins against the cells. The HI antigen was fresh allantoic fluids from 10-day-old embryonating chicken eggs infected with the virus strains used.
Publication Date: 1977-10-01 PubMed ID: 21985DOI: 10.1292/jvms1939.39.571Google Scholar: Lookup
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- Comparative Study
- Journal Article
Summary
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This study investigates the antigenic relationship between the Tokyo and Miami strains of equine influenza (EI) subtype 2 virus. Notably, it uncovers discrepancies in the antibody responses of convalescent horses to the two strains.
Background and Objective
- The study was conducted on the backdrop of Japan’s first recognized outbreak of EI infection from December 1971 to January 1972. The virus behind this epidemic was identified as the subtype 2 of EI virus, specifically the A/equine/Tokyo/71 (Tokyo) strain.
- The Tokyo strain garnered attention due to deviations from the prototypic A/equine/Miami/63 (Miami) strain. Convalescent horses had 2 to 16 times higher antibody responses to the Tokyo strain than the Miami strain in hemagglutination-inhibition (HI) tests.
- This led to speculations of a significant antigenic drift within the EI subtype 2 viruses. Antigenic drift is the phenomena where the virus mutates over time, leading to changes in the surface proteins, which cause antibodies to no longer recognize and combat the virus effectively.
- In light of this, the study aimed to examine the antigenic relationship between the Tokyo and Miami strains by conducting cross HI tests with the rabbit antisera of these strains.
Methodology
- Additionally, the A/Hong Kong/68 strain of human influenza virus was included for comparison due to its close antigenic relation with EI virus subtype 2.
- The research conducted the HI test using the microtiter method. The process involved a 2-fold dilution of serum, 8 hemagglutinating units of virus antigen in 0.025 ml each, and 0.5% chicken erythrocytes in 0.05 ml volume.
- The serum samples used in the test were treated with several chemicals in a stepwise manner including M/60 potassium periodate, 6% glycerol saline, and commercial Receptor Destroying Enzyme to prepare them for the experiment.
- The sample was then once again inactivated and absorbed with chicken erythrocytes to remove natural agglutinins.
- The HI antigen used was fresh allantoic fluids from 10-day-old embryonating chicken eggs infected with the virus strains under study.
Implications and Next Steps
- The study does not provide the results or outcomes of the investigation. Accordingly, it is important for future publications or continuations of this research to reveal the findings from these practices.
- The value of this investigation lies in uncovering the antigenic relations between different strains of EI, which could be critical for effective vaccination and outbreak control efforts.
Cite This Article
APA
Goto H, Shimizu K.
(1977).
Antigenic relationship between the Tokyo and the Miami strains of equine influenza subtype 2 virus.
Nihon Juigaku Zasshi, 39(5), 571-574.
https://doi.org/10.1292/jvms1939.39.571 Publication
Researcher Affiliations
MeSH Terms
- Antigens, Viral / analysis
- Florida
- Influenza A virus / immunology
- RNA Viruses / immunology
- Tokyo
Citations
This article has been cited 2 times.- Goto H, Shimizu K, Taya Y, Noda H, Tokunaga T. Antibody responses of horses to equine influenza viruses during a postepizootic period in Japan. Can J Comp Med 1982 Jan;46(1):27-32.
- Ogawa Y, Goto H, Hirano T, Shimizu K, Ohno Y, Kuroda H, Hongo H. Sero-epizootiological study on swine influenza in a prefecture of Japan. J Hyg (Lond) 1983 Jun;90(3):403-6.
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