Therapeutic Effect in Guinea Pigs of Hyperimmune Epidemic Typhus Antiserum

Abstract

Although some studies 1 have been made of the properties of the sera of animals hyperimmunized with murine-typhus rickettsiae, it has only recently been possible to get enough epidemic-typhus rickettsiae for the preparation of a promising epidemic-typhus antiserum. A year ago we 2 pointed out that an antiserum of high neutralizing power could be produced by injecting rabbits with yolk-membrane suspensions from chick embryos infected with Breinl strain of typhus rickettsiae inoculated according to the method of Cox. 3 A similar serum 4 made by injecting horses and donkeys with epidemic-typhus-diseased mouse-lungs has also been described. The present note records some preliminary studies of the therapeutic value in guinea pigs of our rabbit antiserum.

Topping 5 has shown that a good Rocky Mountain spotted-fever antiserum has a clearly demonstrable therapeutic value when injected into infected guinea pigs and monkeys. His original serum was made with an antigen prepared from infected ticks, but we have found 2 that a serum of powerful neutralizing titer can be made from spotted fever-infected egg-membranes. It is easy to show that rabbit anti-serum prepared with this egg-propagated antigen has the same therapeutic value in guinea pigs that Topping 5 has described for the tick-antigen serum. Administration of these hyperimmune sera to guinea pigs infected with a virulent strain of Rocky Mountain spotted fever does not immediately suppress the febrile reaction and other clinical symptoms of the disease; instead, it shortens the febrile reaction and leads to prompt recovery of animals which otherwise would usually die. A similar modifying, rather than immediately curative, action is to be expected from the administration of typhus antiserum to epidemic typhus-diseased guinea pigs. Our experiments clearly demonstrate that such a positive therapeutic effect can be obtained.

In these experiments, guinea pigs have been infected by the intra-abdominal injection of typhus-diseased guinea-pig brain (Breinl strain^*).