A novel acute phase marker in cattle: lipopolysaccharide binding protein (LBP).

The host response to infection, the "acute phase response" is a highly conserved series of physiological reactions including marked changes in concentrations of plasma proteins. These proteins have been shown to participate in the immune response to infections. Several recent studies have elevated the role of acute phase proteins (APPs) as predictive markers in infection. APPs such as serum amyloid A and haptoglobin but not C-reactive protein (CRP) have been identified as markers of inflammation in cattle. In humans, lipopolysaccharide (LPS) binding protein (LBP) has certain biological functions in host defence and participates in acute phase reactions. We measured plasma levels of LBP in a group of 20 calves experimentally infected with Gram-negative Mannheimia haemolytica (Pasteurella) in comparison to haptoglobin, the most widely studied APP in cattle. In infected calves, LBP levels rose significantly 6 h after infection, reaching a maximum at 24 h. Haptoglobin concentrations significantly rose after 12 h, and peak responses were measured 48 h after infection. Thus, LBP may prove to be a diagnostic marker in cattle infection and is faster than haptoglobin in detecting sepsis.