THE IMMUNOLOGY OF INFECTIOUS 

 LARYNGOTRACHEITIS 



By Charles S. Gibbs, 

 Research Professor of Veterinary Science 



In undertaking this study it was necessary first of all to determine whether 

 birds could be artificially immunized to infectious laryngotracheitis or not. After 

 having determined this point, and realizing that very little immunological work 

 has been done with birds, it was felt that some preliminary experiments under 

 controlled conditions in the laboratory would yield results more quickly than could 

 be expected in the field. This report shows that this anticipation has been ful- 

 filled and a foundation has been laid for attempting field work in an experimental 

 way as the next step forward in the investigation of this project. 



In the experiments reported, attempts were made to immunize birdsby inoculat- 

 ing the virus into some portion of the body other than the respiratory tract. 

 Naturally, the exudate and tissues containing the virus had to be modified to 

 facilitate inoculation, and this may have had some efifect upon the results, but 

 the general principle of keeping the virus away from the respiratory tract was 

 adhered to as much as possible. 



FEEDING EXPERIMENTS WITH UNFILTERED VIRUS ' 



On nine consecutive days, 36 chickens six weeks old were fed infectious laryngo- 

 tracheal exudate in gelatin capsules without any of them showing symptoms of 

 disease. Nine control chickens from the same flock, inoculated intratracheally 

 with the same virus, contracted the disease and seven of them died. Four weeks 

 after the feeding had been completed, the 36 chickens were inoculated intratrache- 

 ally with fresh infectious laryngotracheal exudate,' and all of them came down with 

 the disease, from which 29 died. This experiment indicates that no lasting im- 

 munity was stimulated by feeding chickens six weeks old with virulent infectious 

 laryngotracheitis virus for nine days. 



SEITZ FILTERED VIRUS 

 Intravenous Inoculation 



1. Single Inoculations of Diluted Virus 



An attempt was made to immunize birds by inoculation in the wing veins with 

 various dilutions of infectious laryngotracheitis virus which had been passed 

 through Seitz E. K. Schichten filters to remove bacteria. The first part of this 

 project, or the filtrations through the Seitz filters, was the most difficult to control, 

 because no satisfactory way of standardizing the virus had been discovered, and 

 the filtrates could not always be depended upon to contain sufficient virus to 

 produce the desired degree of immunity unless carefully checked by adequate 

 controls. When it was found by means of the controls that the virus did not pass 

 the Seitz filters in sufficient quantity to infect susceptible chickens, inoculated 

 intratracheally, the filtrations and inoculations were repeated with fresh virus 

 until satisfactory results were secured. 



Sixty-eight clucks, which had never been exposed to infectious laryngotrachei- 

 tis, were divided into four groups, each group consisting of fifteen chickens for in- 

 travenous inoculation and two for intratracheal inoculation or controls. Each 



