Objective: To investigate the relationship between Pseudomonas aeruginosa (P.aeruginosa) elastase and pulmonary surfactant protein A (SP-A) in host infected by P.aeruginosa.
Methods: C3H mice were intranasally infected with P.aeruginosa wild-type PAO1, ΔlasB mutant and genetic complement strain PDO240LasB to determine the difference of virulence between wide type and mutant. The ability to degrade SP-A in vitro by PAO1, ΔlasB and PDO240LasB was observed through co-incubation of equal bacteria and SP-A and detected by Western blotting. The susceptibility of bacteria to phagocytosis was assayed by in vitro experiment that bacteria treated with SP-A was incubated with mouse Raw264.7 macrophages.
Results: Compared with wide-type PAO1, the virulence of ΔlasB mutant was attenuated in the mouse model of P.aeruginosa infection because of the knock down of elastase expression. The ΔlasB mutant lost the ability to degrade SP-A when incubated with SP-A in vitro. The in vitro phagocytosis experiments showed that SP-A augmented the phagocytosis of ΔlasB mutant bacteria more efficiently than the wild-type PAO1.
Conclusion: P.aeruginosa elastase provides a protection from phagocytic cells by degrading SP-A.