534 F. M. BURNET 



reactions and for much epidemiological work the complement fixation test 

 can be taken as a usefid index of recent infection. 



C. Fluorescent Antibody Techniques 



An immunological teclmique which is rapidly extending its usefulness in 

 virology is the use of fluorescent antibody as a histochemical reagent. This 

 was introduced by Coons and has been applied extensively by his group to 

 the examination of experimental lesions of influenza and mumps virus infec- 

 tions (Coons et al., 1950; Watson and Coons, 1954). There is evidence that 

 both soluble complement fixation antigen and somatic viral antigen can be 

 located with this method; one of the most interesting findings has been the 

 demonstration claimed by Watson and Coons that the first antigen to 

 appear in the infected cell is of the soluble complement fixation type and is 

 located in the nucleus. Another interesting development has been its use to 

 detect a production of viral material in cells resisting infection in the ordinary 

 sense. Prince and Ginsberg (1957) have shown that Ehrhch ascites tumor 

 cells infected in vitro with Newcastle disease virus and then returned to the 

 mouse peritoneal cavity failed to develop infectivity, hemagglutinin, or 

 complement fixation antigen, but did develop strong cj^oplasmic fluores- 

 cence when stained with treated anti-Newcastle disease virus serum. Wecker 

 and Schafer (1957), using separate fluorescent sera for soluble complement 

 fixation antigen and hemagglutinin of fowl plague virus, found that the 

 S antigen begins to appear in the nucleus at three hours, and an hour later 

 hemagglutinin antigen is found in the cytoplasm. More appHcations of this 

 versatile technique to studies of this general type can be expected in the 

 future. 



IV. The Process of Virus Neutralization 



A. Neutralization of Bacterial Viruses 



Bacterial viruses, particularly those of the large particle C16-T2 group 

 (Adams, 1952) are readily neutralized by immune sera; a great deal of work 

 has been devoted to the elucidation of the reaction. In recent years, discussion 

 of the process has largely centered on the finding that union of phage particle 

 to the susceptible bacterial cell takes place by the tip of the phage tail 

 (Anderson, 1953). At the present time, there is much to suggest that the agent 

 that actually attaches to the bacterial cell wall is contained m fibrils, which 

 are probably womid spirally aroimd an inactive core, and frayed ends of 

 which can often be seen in electron micrographs at the tip of the tail ( WiUiams 

 and Frazer, 1956; Evans, 1956). 



