40 S. G. ANDERSON 



II. Particulate Hemagglutinin with no Eluting Enzyme 



A. Arthropod-borne Encephalitides 



1. Historical 



In 1936, Burnet found that chick embryos inoculated on the chorioallan- 

 tois with louping ill virus and showing visceral lesions regularly contained 

 virus attached to the red blood cells. This seems to be the first indication of 

 the capacity of a member of the arthropod-borne virus group to attach to 

 erythrocytes. 



Hemagglutination by this group of viruses was first described by Sabin 

 and Buescher (1950) with Japanese B, West Nile, and far eastern encephalitis 

 viruses. Sabin (1951) later added St. Louis and possibly western equine 

 encephalitis, and Sweet et al. (1953) dengue 1 and dengue 2. Macdonald (1952) 

 described hemagglutination by Murray Valley encephalitis. Casals and 

 Brown (1953) confirmed West Nile, dengue 1, dengue 2, and Japanese B, 

 and added Ilheus, Ntaya, and yellow fever (Asibi). Clarke and Theiler (1955) 

 found Semliki Forest and Bunyamwera agglutinins in mouse serum. Some 

 neurotropic viruses are reported to lose their hemagglutinin after many 

 mouse passages (Sabin, 1951). 



2. Cells Agglutinated 



Japanese B virus is typical of these viruses in agglutinating red cells from 

 day-old chickens, but generally not from adult fowls, nor from humans nor 

 rhesus monkeys (Sabin and Buescher, 1950). Both Murray Valley encephalitis 

 virus and Japanese B virus agglutinate red cells from adult pigeons 

 (Macdonald, 1952). Russian far eastern encephalitis agglutinates sheep cells 

 at pH 7.5, West Nile agglutinates baby chicken and sheep cells at pH 7.3, 

 and St. Louis virus agglutinates baby chicken cells at pH 6.5 to 7.0 (Sabin, 

 1951). 



3. Preparation of Hemagglutinin 



The hemagglutinin may be extracted from 21 -day-old (Sabin and Buescher, 

 1950) or suckling mouse brains (Macdonald, 1952; Casals and Brown, 1953) 

 at appropriate hydrogen ion and salt concentrations. Physiologically normal 

 saline will extract Japanese B and Murray Valley hemagglutinins, which 

 should then be centrifuged at 20,000 g for 60 minutes, and may be stored for 

 long periods at 4°C. in the liquid state, or preferably lyophilized or frozen at 

 — 20°C. (Casals and Brown, 1954). In the liquid state, at 5°C. the hemag- 

 glutinin increased in titer over a period of 3 to 10 days (Sabin and Buescher, 

 1950). No hemagglutinin has so far been found in extracts of virus infected 

 chorioallantoic membrane. 



