Inflammatory response of Haemophilus influenzae biotype aegyptius causing Brazilian Purpuric Fever

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Brazilian Purpuric Fever (BPF) mimics meningococcal sepsis and is linked to Haemophilus influenzae biogroup aegyptius.
• The specific virulence factors of H. influenzae biogroup aegyptius causing BPF remain largely unknown.

Purpose of the Study:

• To investigate the role of the las gene in BPF pathogenesis.
• To explore horizontal gene transfer as a mechanism for virulence acquisition in H. influenzae.

Main Methods:

• Constructed a las gene fusion with an ermAM cassette in virulent Neisseria meningitidis strains.
• Transferred the las gene construct via DNA transfer to non-BPF H. influenzae strains.
• Analyzed cytokine expression (TNF-α and IL-10) in Hec-1B cells infected with transformed H. influenzae mutants.

Main Results:

• Successful transfer of the las gene to non-BPF H. influenzae strains was achieved.
• Transformed H. influenzae mutants showed significantly increased expression of TNF-α and IL-10 cytokines (eight log scale folding change).
• This suggests the las gene contributes to the inflammatory response associated with BPF.

Conclusions:

• The las gene, when transferred from N. meningitidis, can enhance the virulence of H. influenzae.
• Horizontal intergeneric gene transfer is a plausible mechanism for the emergence of virulent strains like those causing BPF.
• This study provides the first molecular evidence for the role of the las gene in BPF pathogenesis through horizontal transfer.