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| Hemagglutination-inhibition. Acetone-ether and sucrose-acetone extracted mouse brain and serum antigens were prepared and tested for hemagglutination properties according to the method of Clarke and Casals, with negative results. |
| Complement-fixation. The acetone-ether extracted brain was used as a complement-fixing antigen in a screen test (1:8 dilution of antigen tested against 1:4 dilution of serum in the presence of 2 exact units of complement) against about 70 hyperimmune mouse serum. No positive reactions were found except with homologous systems [1] . |
| Neutralization. None of about 70 specific immune sera available at the RML (see [1] ) gave any demonstrable protection, whereas, the homologous sera neutralized at least 3 dex of virus. |
| In CF tests by Jordi Casals at the Rockefeller Foundation Laboratories, negative results were obtained in tests with Hughes antigen against immune sera of 15 strains representing 10 different tick agents, including Ganjam, Bhanja, Wanowrie, and Silverwater [1] . |
| Later studies at YARU have shown a relationship by CF test of Hughes virus with Soldado and with other viruses including CalAr 913, Farallon, Zirqa and Punta Salinas [4] . |
| Puffin Island virus, presently unregistered, is antigenically related to but distinct from Hughes virus and other members of HUG serogroup [10] . |
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