Repetitive Exposure to Bacteriophage Cocktails against Pseudomonas aeruginosa or Escherichia coli Provokes Marginal Humoral Immunity in Naïve Mice

Abstract

Phage therapy of ventilator-associated pneumonia (VAP) is of great interest due to the rising incidence of multidrug-resistant bacterial pathogens. However, natural or therapy-induced immunity against therapeutic phages remains a potential concern. In this study, we investigated the innate and adaptive immune responses to two different phage cocktails targeting either Pseudomonas aeruginosa or Escherichia coli—two VAP-associated pathogens—in naïve mice without the confounding effects of a bacterial infection. Active or UV-inactivated phage cocktails or buffers were injected intraperitoneally daily for 7 days in C57BL/6J wild-type mice. Blood cell analysis, flow cytometry analysis, assessment of phage distribution and histopathological analysis of spleens were performed at 6 h, 10 days and 21 days after treatment start. Phages reached the lungs and although the phage cocktails were slightly immunogenic, phage injections were well tolerated without obvious adverse effects. No signs of activation of innate or adaptive immune cells were observed; however, both active phage cocktails elicited a minimal humoral response with secretion of phage-specific antibodies. Our findings show that even repetitive injections lead only to a minimal innate and adaptive immune response in naïve mice and suggest that systemic phage treatment is thus potentially suitable for treating bacterial lung infections.

Phage therapy in lung infections caused by multidrug-resistant Pseudomonas aeruginosa – A literature review

“…Weissfuss et al. studied the immune responses following application of a phage cocktail (comprising DSM 19872/JG005 and DSM 22045/JG024) to naive mice [ 29 ]. The authors were able to show that phages injected intraperitoneally reached the systemic circulation of mice within six hours without inducing an increase of polymorphonuclear neutrophils in the blood.…”

“…Notably, no adverse effects due to phage application could be assessed. In summary, the authors concluded that phage cocktails constitute promising antibacterial treatment options for P. aeruginosa infections in the future [ 29 ].…”

“…While one study negated phage induced immunological reactions [ 30 ], the murine immune system responded to phage application with enhanced TNF-α and IL-6 levels [ 15 ] as well as phage-specific IgG and CD4 + T cells in another report [ 29 ]. However, it was asserted that alongside phages, the immune system incorporates the complement system [ 31 ] and neutrophilic granulocytes in the joint combat of P. aeruginosa infections.…”

Bacteriophages as a potential substitute for antibiotics: A comprehensive review

“…Repetitive dosage of phage cocktails may elicit a humoral response and may result in failure in the clinical trial. 61 Antibody production may be responsible for the failure of outcomes. A naive patient who has not been treated with phage may have pre-existing natural antibodies that resist the phage therapy results compared to a patient who has already undergone phage treatment.…”

“…Histopathological analysis shows no elicitation of innate or adaptive immunity but a slight humoral response. Repetitive dosage of phage cocktails may elicit a humoral response and may result in failure in the clinical trial 61 . Antibody production may be responsible for the failure of outcomes.…”