Abstract
The low antifibrinolytic titer† of most commercial anti-streptococcus serums 1 suggests the possibility that the specific antihuman fibrinolysin formed or secreted by certain strains of Streptococcus hemolyticus is not antigenic.
To test this possibility, active antifibrinolytic immunization was attempted with rabbits. The selected vaccines were (a) centrifugates from 24-hour broth cultures of fibrinolytic streptococci, and (b) lytic enzymes isolated from such cultures by the alcohol-precipitation technic. 2 Control injections were made with (c) heat-killed streptococci centrifuged free from lytic broth. There were also available for comparison (d) a series of rabbit precipitins for the Lancefield streptocarbohydrate A. This specific capsular sugar is apparently genetically linked with the antihuman fibrinolytic function. 3
Three methods of immunization were used with these rabbits. Six animals (Group A) received 3 subcutaneous, 3 intraperitoneal and 3 intravenous injections at 3 to 4-day intervals, followed by 6 intra-venous injections at weekly intervals, the injection dose being: (a) 1,000 arbitrary units of the lytic enzyme, (b) 1 cc. (about 100 lytic units) of the centrifugate, or (c) equivalent amounts of lysin-free streptococci. Six rabbits (Group B) received the same vaccines intradermally (divided doses). Six animals (Group C) were given only one vaccine, the alcohol-precipitate, this was administered by means of a stomach tube, duodenal tube or enteric capsule.
Antiserums were withdrawn from all animals 10 days after the final vaccine dose. The average antifibrinolytic titer of each group of antiserums thus obtained is recorded in Table I.
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