Antibody complement-dependent bacteriolysis in experimentally induced pasteurellosis in mice

Area of Science:

• Immunology
• Veterinary Medicine
• Microbiology

Background:

• Bovine immunoglobulins play a crucial role in host defense against bacterial pathogens.
• Pasteurella haemolytica is a significant cause of respiratory disease in cattle.

Purpose of the Study:

• To investigate the bacteriolytic activity of different bovine immunoglobulin isotypes against Pasteurella haemolytica.
• To evaluate the protective efficacy of bovine immunoglobulins in a murine model of pasteurellosis.

Main Methods:

• In vitro bacteriolysis assays using purified bovine immunoglobulin isotypes (IgM, IgG1, IgG2, IgA) and complement.
• Passive immunization of C57BL/6 mice with bovine immunoglobulins followed by experimental Pasteurella haemolytica challenge.
• Assessment of bacterial clearance and survival rates in immunized mice, with and without complement depletion.

Main Results:

• Bovine IgM and IgG1 demonstrated significant bacteriolytic activity against Pasteurella haemolytica via both classical and alternative complement pathways.
• IgG2 showed greater bacteriolysis than IgA, with activities varying between complement pathways.
• Passive administration of bovine immunoglobulins conferred protection against experimental pasteurellosis in mice, with IgM and IgG showing comparable efficacy.
• Complement depletion reduced bacterial clearance, indicating a crucial role for the complement system in antibody-mediated protection.

Conclusions:

• Bovine immunoglobulins, especially IgM and IgG1, are potent bacteriolytic agents against Pasteurella haemolytica, acting through complement-dependent mechanisms.
• Passive immunotherapy with bovine immunoglobulins offers a viable strategy for preventing and treating pasteurellosis.
• The intact complement system is essential for optimal efficacy of antibody-mediated protection against Pasteurella haemolytica infections.