Potential of recombinant CAV1-Fc in the treatment of ApxI toxin-induced damage by Actinobacillus pleuropneumoniae.

Currently, porcine contagious pleuropneumonia (PCP) caused by Actinobacillus pleuropneumoniae (APP), poses a significant threat to the pig breeding industry. There is an urgent need for effective therapeutic and prophylactic treatments, especially those that can overcome the limitations associated with vaccines and antibiotics. This includes the development of novel antitoxin agents, immunomodulatory therapies, and alternative strategies like phage therapy and herbal extracts. Our previous study has demonstrated membrane protein caveolin-1 (CAV1) is a key protein that acts as a functional receptor of APP ApxI toxin by binding to its acylated region. Here, we developed recombinant human N-CAV1-Fc fusion protein and C-CAV1-Fc fusion protein. Both fusion proteins could tightly bind to ApxI toxin. N-CAV1-Fc and C-CAV1-Fc fusion proteins efficiently blocked the interaction between ApxI toxin and immortalized porcine alveolar macrophages (iPAMs), thereby inhibiting cell apoptosis caused by APP ApxI toxin. Furthermore, prophylactic and therapeutic CAV1-Fc treatments effectively protected mice from ApxI toxin-induced damage, as determined by reduced weight loss, apoptosis factor transcription, and pathological changes in the lungs. The protective effects of N-CAV1-Fc and C-CAV1-Fc showed clear dose-dependent efficacy in vivo. Protein kinetics data indicated that N-CAV1-Fc has a relatively longer half-life in vivo compared to C-CAV1-Fc, making it an excellent candidate for prevention and treatment of APP infections.