Beware of host immune responses towards bacteriophages potentially impacting phage therapy.

The rising spread of antimicrobial resistance challenges animal welfare, productivity and food supply with respect to bacterial infections in different livestock species. Bacteriophages offer alternative means to control infections with resistant bacteria. This work investigated the host immune responses towards lytic bacteriophages K and T1, acting respectively on Gram-positive or Gram-negative bacteria. We employed an ex vivo platform to decipher various immune responses elicited by primary blood cells of eight outbred cattle. Bacteriophage K was not recognized whereas bacteriophage T1 induced a profound immune response. Therefore, prior characterization of host immune responses towards therapeutic phages should be considered before therapy starts.