AN IMMUNOLOGICAL STUDY OF BACILLUS INFLUENZAE

Area of Science:

• Microbiology
• Pathogenesis
• Immunology

Background:

• Influenza bacilli exhibit variable pathogenicity in humans and animal models.
• Understanding the differences between virulent and non-virulent strains is crucial for disease control.

Purpose of the Study:

• To investigate the differences in virulence, serological characteristics, and autolysis of influenza bacilli from various pathological sources.
• To assess the antibody response in rabbits inoculated with different strains and their protective immunity.

Main Methods:

• Isolation of influenza bacilli from human pathological samples.
• Assessment of animal pathogenicity, primarily in rabbits.
• Serological testing including agglutination, complement deviation, and opsonification.
• Evaluation of bacterial autolysis and antibody production in inoculated rabbits.

Main Results:

• Influenza bacilli strains varied significantly in their virulence for rabbits, with strains from leptomeninges and blood being more pathogenic than respiratory tract isolates.
• Despite virulence differences, serological tests (agglutination, complement deviation, opsonification) did not distinguish between virulent and non-virulent strains.
• Virulent strains showed nearly complete autolysis with turbid supernatant, while non-virulent strains produced abundant sediment and clear supernatant.
• Non-virulent strains induced lower antibody production in rabbits, resulting in sera with low antibody content and poor protection against subsequent virulent strain inoculation.

Conclusions:

• Influenza bacilli exhibit a spectrum of virulence but are serologically indistinguishable, suggesting a single class or race.
• Differences in autolysis and antibody response correlate with virulence but do not define distinct serological types.
• Animal models, like rabbits, can reveal virulence variations and immune responses, aiding in understanding influenza bacilli pathogenesis.