PASSIVE LOCAL IMMUNOTHERAPY OF EXPERIMENTAL STAPHYLOCOCCAL PNEUMONIA WITH HUMAN INTRAVENOUS IMMUNOGLOBULIN

Staphylococcus aureus remains a life-threatening agent of nosocomial p neumonia in immunocompromised patients. The increasing incidence of st rains exhibiting wide-spectrum resistance to antibiotics, such as meth icillin-resistant S. aureus (MRSA), requires new therapeutic strategie s. There is renewed interest in passive immunization with human plasma -derived immunoglobulins (IVIG) as antiinfective agents. The efficacy of IVIG was tested in an experimental model of staphylococcal pneumoni a, using both an MRSA clinical isolate and reference strain Cowan III, in mice immunosuppressed with cyclophosphamide. Efficient antistaphyl ococcal activities were obtained with IVIG administered intravenously or intranasally. IVIG saturated with protein A or its F(ab')2 fragment s were as efficient as intact IVIG, suggesting that protection did not require opsonization through IgG Fc-phagocyte Fcgamma-receptor intera ctions. Thus, topical administration of IVIG may replace a local antib ody response to S. aureus in an immunocompromised host and may be usef ul in prophylaxis and treatment of nosocomial S. aureus pneumonia.