Cross-protection between Actinobacillus pleuropneumoniae biotypes-serotypes in pigs

Area of Science:

• Veterinary Immunology
• Swine Infectious Diseases
• Bacteriology

Background:

• Actinobacillus pleuropneumoniae (A. pleuropneumoniae) causes significant economic losses in the swine industry.
• RTX toxins (ApxI, ApxII, ApxIII) produced by A. pleuropneumoniae are key virulence factors.
• Understanding cross-protection between different serotypes and biotypes is crucial for effective vaccination strategies.

Purpose of the Study:

• To investigate the protective immune mechanisms against Actinobacillus pleuropneumoniae challenge.
• To evaluate the role of RTX toxin neutralizing antibodies in cross-protection.
• To assess the efficacy of immunization with different A. pleuropneumoniae strains.

Main Methods:

• Four groups of pigs were intranasally inoculated with different strains of A. pleuropneumoniae or saline.
• Pigs were subsequently challenged endobronchially with an A. pleuropneumoniae biotype 1-serotype 2 strain.
• Clinical signs, lung lesions, and RTX toxin neutralizing antibody titers were assessed post-challenge.

Main Results:

• Pigs immunized with A. pleuropneumoniae biotype 1-serotype 10 and biotype 2-serotype 2 strains showed partial protection against challenge.
• Control pigs and some immunized pigs exhibited severe clinical signs and lung lesions.
• Antibodies neutralizing ApxI, ApxII, or both ApxII and ApxIII were present in sera of pigs immunized with specific strains.

Conclusions:

• Immune mechanisms beyond RTX toxin neutralizing antibodies contribute to cross-protection against A. pleuropneumoniae.
• Partial cross-protection was observed in pigs immunized with specific A. pleuropneumoniae strains.
• Further research is needed to elucidate the complex immune responses involved in swine respiratory disease.