Cavity Of Embryos Research Articles

A Capillary Tube Agglutination Test for Detecting Antibodies against Ornithosis in Turkey Serum

Summary and Conclusions A capillary tube agglutination test using a Giemsa-stained, buffered suspension of elementary bodies prepared from a toxigenic turkey strain of ornithosis virus propagated in the allantoic cavity of chicken embryos was compared with the indirect complement fixation test, and the results were promising. The CTA test seemed to be more sensitive in the first week or two after infection, and thereafter the two tests seemed equally sensitive. Both were a little more sensitive than the direct complement fixation test when the test material was turkey serum. In the CTA test false positive reactions were encountered, usually in low serum dilutions, but occasionally in dilutions as high as 1:32, when the serum was hemolyzed, contaminated or contained residual fibrin. Reactions at dilutions of 1:16 or higher constituted good presumptive evidence of infection or of some previous encounter with ornithosis agents; reactions at dilutions of less than 1:16 were less specific and were interpreted cautiously. Preliminary testing of serum from infected parrots and pigeons indicated that the CTA test can detect ornithosis antibodies in these species. The CTA test is economical and simple to perform. According to the results of these tests it could be a useful flock test, of value in epizootiologic surveys, and a rapid screening test of flocks before marketing in enzootic or epizootic areas. Flocks undergoing acute or subacute epizootics of ornithosis, the most dangerous from the standpoint of public health, could be detected easily.

STUDIES ON HOST-VIRUS INTERACTIONS IN THE CHICK EMBRYO-INFLUENZA VIRUS SYSTEM

The role of inactivated influenza virus in the von Magnus phenomenon has been studied by exposing standard virus preparations in vitro to 37 degrees C. for periods up to 6 or more days. The rate of inactivation of the infectious property of the line of PR8 virus employed was found to be approximately 1.1 log(10) unit per day, denoting a half-life of 6(1/2) hours. The rate of inactivation was similar in the allantoic cavity of chick embryos. On allantoic passage of such heated seeds without dilution it was seen that with a decrease in the infectivity of the inocula proportionately less infectious virus was found in the harvests. The yields of hemagglutinins were much less affected, and thus ID(50)/HA ratios of as low as 10(1.0) were observed in the 24 hour harvests. The ratios of the yields always equalled or were higher than those of the inocula. On 100- or 1000-fold dilution of the heated seeds standard virus was obtained. Growth curves in intact chick embryos or in deembryonated eggs (differential yields) revealed that non-infectious hemagglutinins appeared in the tissues or were liberated therefrom as soon as any virus activity became detectable. Furthermore, once maximal liberation had been established, infectious virus and non-infectious hemagglutinins were released for extended periods of time at nearly constant rates and in unchanging proportions, the latter depending upon the seed employed. Heated standard virus and undiluted passage seeds (von Magnus), selected on the basis of similar ID(50) and HA concentrations, failed to yield similar results in differential growth curves in deembryonated eggs. Although the hemagglutinin titers in the 2-hourly harvests were nearly identical, the undiluted passage seeds produced as little as 1 per cent of the infectious virus which was derived from the heated inocula. Thus considerable differences exist between the 2 types of seeds.

The Incorporation of Radioactive Phosphorus into Influenza Virus

Summary Studies have been presented on the labelling of influenza virus with P32 during propagation in the allantoic cavity of chick embryos. The labelled virus has been purified routinely by 2 cycles of adsorption onto and elution from chicken red cells with intermittent dialysis against large volumes of phosphate buffered saline solution. The degree of radioactivity of the virus progeny could be improved by an increase in the dose of P32 used, by prolongation of the interval between injection of the isotope and infection, and by a reduction in the age of the embryos employed. The ratio between counts per minute and hemagglutinin units of the yields could be increased further by the use of deembryonated eggs instead of intact chick embryos. It has not been possible to separate the radioactivity from the virus particles by various biological, physical and chemical means. Chemical fractionation of labelled virus revealed most of the radioactivity in the lipid and nucleic acid fractions.

Cultivation of Viruses of the Psittacosis Group in the Allantoic Cavity of Chick Embryos.

Many of the viruses of the psittacosis group have been cultivated successfully in fertile hens'eggs, the yolk sac being most satisfactory for this purpose. Using this particularly susceptible tissue, preparation of large amounts of virus has been possible. Such preparations cannot be regarded as ideal for some purposes, however, such as attempts at purification of the virus or for production of antigens, because of the large amount of admixed tissue debris and yolk material, removable only with difficulty. It occurred to us that the allantois, being embryologically similar to the yolk sac, might also show special susceptibility to the viruses of this group. The allantoic cavity has been extremely useful in cultivation of influenza virus, and the advantages in the case of the latter virus might be expected to hold for others as well. After our first attempts to adapt mouse pneumonitis virus, one of the agents of this group, to the allantoic cavity, the publication of Williams appeared, in which he reports successful cultivation of psittacosis virus in the allantoic cavity and in greater amounts than obtained in the yolk sac. We have been able to confirm his finding and have extended the study to other viruses of the group. The present preliminary report records the successful cultivation of a strain of psittacosis, human pneumonitis (SF), and meningopneumonitis (F-97) virus in the allantoic cavity. The few attempts made so far to adapt mouse pneumonitis virus to the allantoic cavity have not been successful. Williams reported failure to cultivate lymphogranuloma venereum virus in this tissue. The strains of virus used in the present experiments have been employed in previous work in this laboratory and their sources have been recorded. The first inoculations into allantoic cavities were made with emulsions of infected mouse tissue or yolk sac, and subsequent passages were made with 0.25 cc quantities of undiluted allantoic fluid.