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.