Bacteriophage neutralization in vivo involves the complement system
The complement system is a key component of the innate (non-specific) immune response. It is present in human and other mammals’ sera at high concentrations and it has been found ‘to complement’ the action of antibody directed against pathogens. Since the complement system has been shown as active in neutralizing many viruses, we have investigated its potential to neutralize bacteriophages.
We compared phage circulation in complement-deficient mice (C1q knock-out: B6N(Cg)-C1qa/3J) and in normal mice in blood and in selected tissues. Mice were investigated both as naïve individuals or pre-immunized with a non-essential phage capsid protein (gpHoc). Hoc-specific IgM was confirmed by ELISA. We also compared the ability to neutralize bacteriophages in vitro by normal sera (active complement) and inactivated sera (inactive complement).
In vitro, serum complement was able to decrease phage viability, however this effect was detected only in the presence of specific antibodies. The decrease was two orders of magnitude (p<0.05). In accordance with this observation, active phage concentration in the blood of the complement-deficient mice was significantly higher than that in normal mice. The difference was significant (p<0.05) in mice pre-immunized with gpHoc: approx. one order of magnitude 2h and 5h after phage application. Interestingly, phage concentration in kidneys and liver was also increased.
According to these observations, the classical, antibody-dependent pathway of serum complement can reduce phage viability. Thus, phage may be neutralized by a similar immune response as eukaryotic viruses are, in spite of the fact that phages do not naturally target mammals. Phages lack a lipid outer layer, thus similarities cannot be extrapolated from any eukaryotic viruses, but rather from Adenoviruses or adenoviral vectors: complement and opsonins play a contributory role in their clearance by Kupffer cells in liver.
This work was supported by the National Science Centre in Poland grant no. UMO-2012/05/E/NZ6/03314 and by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014-2018.
We compared phage circulation in complement-deficient mice (C1q knock-out: B6N(Cg)-C1qa
In vitro, serum complement was able to decrease phage viability, however this effect was detected only in the presence of specific antibodies. The decrease was two orders of magnitude (p<0.05). In accordance with this observation, active phage concentration in the blood of the complement-deficient mice was significantly higher than that in normal mice. The difference was significant (p<0.05) in mice pre-immunized with gpHoc: approx. one order of magnitude 2h and 5h after phage application. Interestingly, phage concentration in kidneys and liver was also increased.
According to these observations, the classical, antibody-dependent pathway of serum complement can reduce phage viability. Thus, phage may be neutralized by a similar immune response as eukaryotic viruses are, in spite of the fact that phages do not naturally target mammals. Phages lack a lipid outer layer, thus similarities cannot be extrapolated from any eukaryotic viruses, but rather from Adenoviruses or adenoviral vectors: complement and opsonins play a contributory role in their clearance by Kupffer cells in liver.
This work was supported by the National Science Centre in Poland grant no. UMO-2012/05/E/NZ6/03314 and by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014-2018.
Reference:
Phage 3-T13-Oft-03
Session:
Phage therapy 3: Applications of phage based products
Presenters:
Joanna Majewska
Session:
Phage therapy 3: Applications of phage based products
Presentation type:
Offered talk - 15 min
Room:
Main Auditorium
Chair/s:
Jason Clark
Date:
Thursday, 21 July 2016
Time:
16:10 - 16:25