Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infects healthy individuals, although the precise cause remains unclear. CA-MRSA produces
Panton-Valentine leukocidin (PVL), which often causes severe invasive
infection; however,
antitoxin drugs against PVL are limited.
Intravenous immunoglobulin (
IVIg) possesses
antitoxin activity, but unfortunately, the optimal dose is unknown. Here, we measured the PVL
neutralizing antibody titer in the plasma of Japanese individuals and sera of American donors. Next, we compared the cytotoxic effects of PVL on neutrophils in
phosphate buffered saline (PBS) or whole blood to determine the effect of the
neutralizing antibody. Finally, we evaluated the effective concentration of
IVIg required to neutralize PVL in PBS and whole blood. We observed that the titer of PVL
neutralizing antibody in healthy individuals polarized as high and low/none group. Additionally, the PVL
neutralizing antibody titer considerably affected the concentration at which
IVIg elicited its effect. This suggests that PVL-producing CA-MRSA might be involved in determining the severity of
infection in healthy individuals without
neutralizing antibody against PVL. The neutralizing effect of
IVIg was observed in both PBS and whole blood. However, the optimal concentration of
IVIg required for neutralizing PVL varied between PBS and whole blood. In addition, since the PVL-neutralizing activity of
IVIg also largely depends on blood composition, such as
neutralizing antibody concentration, the optimal dosage of
IVIg as an
antitoxin drug should be decided in a timely manner after considering the patient's medical background.