Experimental human infection with Haemophilus ducreyi

Area of Science:

• Infectious Diseases
• Immunology
• Dermatology

Background:

• Chancroid, a sexually transmitted infection caused by Haemophilus ducreyi (H. ducreyi), is a significant risk factor for HIV transmission.
• The pathogenesis and host immune response to H. ducreyi in humans remain incompletely understood.

Purpose of the Study:

• To investigate the clinical and immunological response to experimental human infection with H. ducreyi.
• To assess the safety and tolerability of controlled H. ducreyi inoculation.
• To explore the cellular immune response in developing chancroid lesions.

Main Methods:

• Four healthy subjects were experimentally infected with H. ducreyi via skin abrasion.
• Clinical observations, lesion biopsies, and serological tests were performed.
• Subjects were rechallenged after two months to assess secondary infection response.

Main Results:

• Localized skin lesions developed at inoculation sites; no systemic symptoms (fever, lymphadenopathy) were observed.
• Histopathology revealed epidermal pustules and dermal infiltrates of T cells and macrophages, indicating a delayed-type hypersensitivity response.
• Humoral immune responses to bacterial components were not detected after primary or secondary infections.
• H. ducreyi was recovered from lesion biopsies, with variable bacterial loads.

Conclusions:

• Experimental H. ducreyi infection in humans is safe and well-tolerated, causing localized cutaneous disease.
• The recruitment of T cells and macrophages into lesions suggests a role for cellular immunity in chancroid pathogenesis.
• Findings provide insights into the biological mechanisms potentially linking chancroid and increased HIV susceptibility.