Effect of pain management on immunization efficacy in mice

Immunization with complete Freund adjuvant (CFA) or incomplete Freund adjuvant (IFA) is commonly viewed as painful, yet rodents may not receive analgesics due to concerns that these drugs affect the desired immune responses. Here we tested the hypothesis that pain associated with immunization with CFA or IFA in mice can be relieved without compromising the effectiveness of the immune response. After subcutaneous immunization in the leg with antigen in CFA or IFA, mice were assessed for signs of pain by using behavioral tests, including unrestricted locomotion in an open field, forced running on an automated treadmill, and voluntary wheel running. Effects of the analgesics acetaminophen, meloxicam, and buprenorphine on behavioral and antibody responses were assessed after primary and secondary immunization with the model antigen ovalbumin and after repeated immunization with a limiting dose of recombinant protective antigen from Bacillus anthracis. Open field activity and the distance traveled during forced gait analysis and voluntary wheel running both decreased after immunization. Treatment with each of the analgesics normalized some but not all of these behaviors but did not decrease the mean or maximal antibody titer after primary or repeated immunization with a moderate dose of ovalbumin or after repeated immunization with a limiting dose of protective antigen. In summary, after immunization with CFA or IFA, mice showed behavioral responses suggestive of pain. Acetaminophen, meloxicam, and buprenorphine attenuated these effects without decreasing antibody responses. Therefore, the use of these analgesics for managing rodent pain associated with CFA- or IFA-containing vaccines can be encouraged.