PN-3659 



A technician operates a shadow casting instrument so that virus preparations can be viewed as three-dimensional objects. 



antigen relationships. They study the mechanism 

 of virus synthesis and its inhibition in tissue 

 culture and cell-free systems by biological and 

 chemical methods, using radiobiological tracers. 



Immunological 



Scientists in immunological investigations 

 check the response of animals infected with or 

 vaccinated against disease agents and they con- 

 duct research on the antibodies that protect 

 against disease. Serum from these animals is 

 separated into elemental components, and these 

 are then analyzed by serological, chemical, and 

 animal- testing techniques. They also study anti- 

 gens or viruses that cause the disease. 



Another function of this group is the develop- 

 ment and testing of vaccines appropriate for 

 possible use if established disease-eradication 

 procedures should fail to control invasions of 

 foreign diseases. These studies include chemical 

 inactivation of virus and development of critical 

 tests to determine the safety and potency of 

 vaccines produced. Such research requires the 



vaccination of many animals and the study of 

 their immunity by serological and challenge 

 methods. 



Cytological 



Scientists in cytological investigations study 

 viral inhibitory substances, changes in viruses 

 caused by environmental conditions, and growth 

 of viruses in cell cultures. They have found that 

 treatment of cells with certain chemicals stimu- 

 lates the production of inhibitory substances 

 effective to a limited extent against foot-and- 

 mouth disease virus. They are investigating the 

 possibility that these substances may be useful 

 in the prevention of the disease. 



Other scientists are attempting to change the 

 foot-and-mouth disease virus by various proce- 

 dures so that it no longer produces disease and 

 thus might be used as a live attenuated virus 

 vaccine. 



Work in the cytological group also includes 

 investigations on the viral susceptibility of 

 various types of cell cultures and factors that 



