Rotavirus Inhibitor and Recovery in Raw Bovine Milk

Milk could be a vector for viruses contaminating the human gut, but detection of rotavirus in raw bovine milk is prevented by the presence of a very active antiviral substance. Rotavirus inhibition by various milk samples and the nature of the inhibitor were examined, and an improved method for rotavirus detection in raw bovine milk was designed. Most milk samples from cows near Toulouse, France, could inhibit 5 × 10⁶ PFU/ml of rotavirus, with wide variations among individuals and with time. The rotavirus inhibitor was bound on a protein G affinity column, and corresponded to the immunoglobulin G fraction (IgG) as shown by enzymatic immunoassay. The proposed method for rotavirus detection requires the action of HCl (pH 3) and dithiothreitol (0.01 M) for 10 min before PFU counts on cell cultures. This treatment improved the detection threshold 1,000-fold, and the recovery of rotavirus in raw bovine milk 300-fold.