500 W, SCHAFER 



The neuraminidase found in tlie myxovirus infective particles is most 

 likely newly formed in the host cell as a virus-specific product. This must 

 be assumed, smce such a component cannot be demonstrated in a normal, 

 noninfected animal cell. In regard to the function of the neuraminidase, the 

 following three possibilities come to nimd: (1) the enzyme can play a role in 

 the penetration of the virus into the host cell, (2) it could mediate the release 

 of the newly formed virus particle, (3) it could mediate both the penetration 

 and release of the infective particles. 



The presence of copper, flavin, and biotin in vaccinia virus would indicate 

 as Smadel and Hoagland (1942) mention, that some rudimentary system of 

 respiration may exist for this relatively highly organized virus "although 

 no substrate capable of sustained activation by these catalytic substances 

 has been found." 



As mentioned above nucleic acid and protein are found in all animal 

 viruses investigated to date. 



The paths of formation of the virus nucleic acid in the host cell has been 

 scarcely studied for the animal viruses. But the one study, carried out with 

 P^- labelmg in fowl plague virus (Wecker, 1957), suggests that P-containing 

 material of the host cell is not directly used in large amomits for the syn- 

 thesis of that virus nucleic acid. 



From studies of other types of virus (tobacco mosaic virus and phages) a 

 reasonable working hypothesis for the animal viruses is that the nucleic acid 

 is the most essential component for the multiplication. In accord with this 

 theory is the fact that the S antigen of poliovirus and the LS antigen of 

 vaccinia virus, both non-infectious, contam no nucleic acid. Further, pre- 

 parations of the incomplete forms of influenza, having a lower probability 

 of causing infection, seem to contam less RNA than the infective particles. 

 But there are also virus-specific products, hke the S and G antigens of fowl 

 plague and influenza virus, with a relatively high percentage of nucleic acid, 

 with which it has not yet betn possible to induce infection. However, one has 

 to consider that these particles may be too small to contain a full RNA 

 molecule of '^ 2 x 10^ molecular w^eight, which Gierer (1957) has shown to 

 be essential for the infectivity m tobacco mosaic virus. If we assume, as 

 Ada and co-workers (1952) claim for the S antigen of uifluenza, a particle 

 weight of 1.5 X 10^ and an RNA content of about 10 %, then the molecular 

 weight of the RNA from these units is only 150,000. One has to bear in mind 

 that the G antigen obtained by ether treatment of infective particles is 

 probably a degradation product dtrivtd from a ringlike structure that 

 contains the intact nucleic acid necessary for multiphcation. 



Initiated by the work with tobacco mosaic virus (Gierer and Schramm, 

 1956; Fraenkel-Conrat, 1956) some investigations have recently been done 

 with animal viruses to show that isolated RNA from these sources is also 



