126 ALICK ISAACS 



eclipse phase, although the findings of Stoker and Ross (1958) are in favor of 

 an eclipse phase for herpes virus. More decisive evidence, particularly for 

 vaccinia virus, will be provided by experiments along the lines of Rubin et al. 

 (1955) with isolated cells, or if recovery of virus in the lag period is found to be 

 low compared with the "plating efficiency," i.e., the ratio of infective virus 

 count to total virus particle count. 



Nevertheless, the trend of the findings favors the idea of the eclipse phase 

 as a general phenomenon among animal viruses. Morgan's (1956) experiments 

 with psittacosis virus are very difficult to interpret except on the assumption 

 that the virus is in a noninfective phase in the starved cell and that it resumes 

 its development when the cell is supplied with certain essential metabolites. 

 The studies by Dulbecco and Vogt (1955) and Dulbecco (1957) on the sensi- 

 tivity of poliomyelitis virus in infected cells to ultraviolet irradiation (based 

 on the work of Luria and Latarjet (1947) on bacteriophages) also imply a 

 change of state of the virus on entering the cells; from the evidence on 

 influenza viruses, a change of state to a noninfective phase seems to be the 

 fate of the majority of infecting virus particles. 



III. Development within Infected Cells of Antigens Associated 

 with Virus Multiplication 



The development of fully mature virus in infected cells may be preceded 

 or accompanied by the development of associated viral antigens. These 

 antigens have excited interest and speculation as to the possibility that some 

 of them might be building blocks which are later assembled to make mature 

 virus. Unfortunately, although there are many published studies of the 

 development of associated viral antigens, attempts to inculpate them as 

 viral precursors have been carried out mainly with influenza and related 

 viruses, with which, therefore, this section is mainly concerned. 



A. The 30 S Complement- Fixing (Soluble) Antigen of Influenza and 



Related Viruses 



During the growth of influenza and related viruses there develops in 

 infected cells an antigen detectable by the complement fixation test, of much 

 smaller particle size than the mature virus particle (Hoyle and Fairbrother, 

 1937). This antigen has a sedimentation constant of 30 S, compared with 

 about 700 S for the virus particle, and is often called the influenza soluble 

 antigen or S, as opposed to the viral antigen or V. The viral antigen has a 

 greater serological specificity than the soluble antigen, and influenza A 

 viruses with widely divergent antigenic characters are said to have a common 

 soluble antigen. However, observations on complement fixation with the 



