What is the mechanism of Palivizumab?

Palivizumab is a humanized monoclonal antibody that plays a critical role in the prevention of severe respiratory syncytial virus (RSV) infection, particularly in high-risk infants. The mechanism of action of Palivizumab revolves around its ability to target and neutralize the RSV virus, thereby preventing it from causing severe respiratory illness.

The RSV virus is a common respiratory pathogen that can lead to serious respiratory tract infections, particularly in infants, young children, and immunocompromised individuals. It is a major cause of bronchiolitis and pneumonia in infants, leading to significant morbidity and hospitalization rates during the RSV season, which typically occurs during the fall, winter, and early spring months in temperate climates.

Palivizumab specifically targets the fusion (F) protein of the RSV virus. The F protein is critical for the virus's ability to enter host cells. It facilitates the fusion of the viral membrane with the host cell membrane, a necessary step for the viral genome to enter the host cell and initiate infection. By binding to the F protein, Palivizumab neutralizes the virus and inhibits its ability to infect host cells.

The neutralization of the RSV virus by Palivizumab occurs through two primary mechanisms:
1. **Inhibition of Viral Fusion:** By binding to the F protein, Palivizumab prevents the conformational changes required for the fusion of the RSV envelope with the host cell membrane. This activity blocks the entry of the virus into the host cell, stopping the infection at its earliest stage.
2. **Opsonization and Phagocytosis:** The binding of Palivizumab to the RSV F protein can also enhance the opsonization of the virus, marking it for destruction by the host's immune system. This process involves the binding of antibodies to the surface of the virus, making it easier for immune cells, such as macrophages and neutrophils, to recognize, engulf, and destroy the virus.

Clinical studies have demonstrated the efficacy of Palivizumab in reducing the incidence of RSV-related hospitalizations in high-risk populations, including premature infants and those with congenital heart disease or chronic lung disease. Its administration is typically done via intramuscular injection, and the dosing schedule is once a month during the RSV season to ensure sustained levels of the antibody in the bloodstream, providing ongoing protection.

Overall, Palivizumab's mechanism of action is a targeted approach that offers significant protection against RSV by neutralizing the virus and preventing its ability to infect host cells. This targeted immunoprophylaxis has become an essential tool in managing and preventing severe RSV infections in vulnerable populations, offering a much-needed safeguard during the critical early months of life.