The chick embryo neutralization test in the assay of meningococcal antibody. 2. Response of the embryo to meningococcal endotoxin and to infection

A previous report described the infection of the chick embryo with Neisseria meningitidis. Although death of embryos was preceded by multiplication of the organisms, the possibility exists that death is caused by the endotoxin contained in the inoculum or released by the bacteria lysing in vivo. A second important condition for the establishment of a satisfactory sero-protection test is that the embryo should act as a host and not merely as a growth medium for N. meningitidis.Results of tests with cortisone-treated embryos show that the pathogenic effect of live meningococcal challenge is mainly due to infection elicited by the meningococci and not to toxaemia. Also, the rate of clearance of meningococci from the blood of the embryo, increased by the addition of meningococcal immune serum, suggests that at this stage of embryonic development (12 days) the phagocytes are active in combating meningococcal infection.

The chick embryo neutralization test in the assay of meningococcal antibody. 1. Infection of the embryo with Neisseria meningitidis

Present methods of controlling meningococcal cerebrospinal meningitis have failed to contain the disease. This has led to the search for effective vaccines and to the development of methods for assaying the potency of these vaccines, as well as for measuring the immune response of the individual. The feasibility of using the sero-protection test in embryonated eggs for the assay of meningococcal antibody has been investigated. The paper describes detailed investigations of the infectious process established by injecting Neisseria meningitidis by various challenge routes. Embryos, even 10-12 days old, showed high susceptibility to meningococci injected via the yolksac or chorioallantoic vein, and lesser susceptibility when injected via the intra-allantoic and chorioallantoic routes. The deaths of intravenously inoculated embryos coincided with the multiplication of the organisms and ensuing septicaemia. A study of the infection in embryos which had died, or were killed, 18-24 hours after inoculation showed a specific localization of the organisms in the brain.