Production and Characterization of F(Ab’)2 Fragments Obtained by Enzymatic Digestion from Murine Anti-MRSA PBP2a Monoclonal Antibodies

Monoclonal antibody anti-PBP2a protects mice against MRSA (methicillin-resistant Staphylococcus aureus) infections

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant bacterium responsible for serious nosocomial and community-acquired infections worldwide. Since few antibiotics are effective for treating MRSA infections, the development of new therapies is of great importance. Previous studies demonstrated that PBP2a is a target that generates protective antibodies against MRSA. A murine monoclonal antibody (MAb) that recognizes PBP2a from MRSA strains was previously isolated and characterized. In this report, we evaluated the biodistribution of this MAb in blood and tissues, as well as the extent of protection conferred using prophylactic and therapeutic assays compared to vancomycin treatment. Biodistribution was evaluated 12–96 h after MAb administration. It predominantly remained in the serum, but it was also detectable in the kidneys, lungs, and spleen at low concentrations (about 4.5% in the kidneys, 1.9% in the lungs, and 0.7% the spleen) at all observed timepoints. Prophylactic studies in a murine model demonstrated a significant bacterial load reduction in the kidneys of the groups treated with either with IgG (greater than 3 logs) or F(ab’)₂ (98%) when compared to that of the control groups (untreated). Mice were challenged with a lethal dose, and the survival rate was higher in the treated mice. Treatment with the MAb resulted in a bacterial load reduction in the kidneys similar to that of mice treated with vancomycin, and a MAb/vancomycin combination therapy was also effective. These results demonstrate that an anti-PBP2a MAb may be a promising therapeutic for treating MRSA infections.

Antibody-Based Agents in the Management of Antibiotic-Resistant Staphylococcus aureus Diseases

Staphylococcus aureus is a human pathogen that can cause a wide spectrum of diseases, including sepsis, pneumonia, arthritis, and endocarditis. Ineffective treatment of a number of staphylococcal infections with antibiotics is due to the development and spread of antibiotic-resistant strains following decades of antibiotic usage. This has generated renewed interest within the scientific community in alternative therapeutic agents, such as anti-S. aureus antibodies. Although the role of antibodies in the management of S. aureus diseases is controversial, the success of this pathogen in neutralizing humoral immunity clearly indicates that antibodies offer the host extensive protection. In this review, we report an update on efforts to develop antibody-based agents, particularly monoclonal antibodies, and their therapeutic potential in the passive immunization approach to the treatment and prevention of S. aureus infections.