Phages and vaccination: towards new opportunities?

Bacteriophages, or phages, are ubiquitous microorganisms that only infect bacteria. They were briefly used, mainly in the West, in the early 20th century to treat human bacterial infections, before being replaced by antibiotics in the 1940s. In the 1970s, the phage display technology, which consists of presenting multiple copies of small polypeptides at the surface of the phage, led to consider phages as vaccine antigen producers. However, the technology potential for this use remains limited to small or truncated antigens that required the use of an adjuvant. Nowadays, phages are gaining a growing interest as vaccine antigen delivery vehicles. Evidence of the phage intrinsic adjuvant properties, which can be enhanced by targeting the particles to various eucaryotic cells, combined with a demonstrated inocuity in human and at low production cost make it possible to envisage in a near future the use of virus-based vaccines-like phagic particles (i.e. virus-like particles). This review describes, in a non-exhaustive way, some of the most promising technological approaches. In addition, there is a growing body of evidence from the literature showing that phages play a major role in the equilibrium of the human intestinal microbiota and protection against mucosal infection, opening new opportunities for vaccine research, targeting pathogens at the first natural host barrier protection.