Influence of Route of Injection on Efficacy and Side Effects of Immunisation

Immunisation experiments are performed on a large scale in laboratory animals e.g. for the production of antibodies. Depending on the immunisation protocol, severe discomfort may be induced. In several countries, guidelines for the immunisation of laboratory animals were drafted to refine immunisation protocols. One of the aspects that effects the immune response as well as the side effects is the route of injection. Careful selection of the route of injection is therefore crucial to refine immunisation protocols. In several papers the influence of the route of injection on the immune response is studied but generally the induced discomfort in the animals is not evaluated.In several comparative experiments we studied the influence of the route of injection on efficacy and side effects. The most widely used routes of injection were compared in rabbits (subcutaneous and intramuscular injection) and in mice (subcutaneous and intraperitoneal injection). After the injection of several adjuvant- (Freund's adjuvant, TiterMax, RIBI, Specol, or Montanide ISA50) and antigen- (synthetic peptide, glycolipid, or particulate antigen) combinations by different routes, we studied antibody production to evaluate efficacy of the injection and clinical-, physiological- and behavioural parameters and pathology (macroscopy/microscopy) to compare the induced side effects. In both rabbits and mice minimal differences in antibody titers were found between the two routes under study. However, differences in the severity of the induced side effects did occur. In rabbits, no significant differences were found in clinical, physiological and behavioural parameters but severe pathological changes were found depending on the route of injection. In mice, the intraperitoneal injection induces significant discomfort as compared to subcutaneous injection as shown by the severity of the pathological changes in the peritoneum and by the decreased activity of the animals. Important disadvantages of intramuscular and intraperitoneal injections are that these injections are difficult to perform properly and that the injection site is hard to monitor. Since minimal differences in antibody production were found between the two routes of injection, we concluded that the subcutaneous route of injection is preferred for the induction of polyclonal antibodies in rabbits and mice when an adjuvant is applied.