Rotavirus Inhibitor and Recovery in Raw Bovine Milk

Area of Science:

• Veterinary Virology
• Food Safety
• Immunology

Background:

• Raw bovine milk can potentially transmit viruses to the human gut.
• Detecting rotavirus in raw milk is challenging due to an inherent antiviral substance.
• Understanding this inhibitor is crucial for accurate food safety assessments.

Purpose of the Study:

• To investigate the rotavirus inhibitory activity in raw bovine milk.
• To identify the nature of the antiviral substance present in milk.
• To develop an improved method for sensitive rotavirus detection in raw milk.

Main Methods:

• Assessed rotavirus inhibition in milk samples from cows near Toulouse, France.
• Utilized protein G affinity chromatography to isolate the inhibitor.
• Employed enzymatic immunoassay to identify the inhibitor as immunoglobulin G (IgG).
• Developed a detection method involving pre-treatment with HCl (pH 3) and dithiothreitol (0.01 M).

Main Results:

• Most milk samples exhibited significant rotavirus inhibition (up to 5 × 10^6 PFU/ml).
• Variability in inhibitory activity was observed among individual cows and over time.
• The inhibitor was confirmed to be the immunoglobulin G (IgG) fraction.
• The new detection method enhanced the rotavirus detection threshold by 1,000-fold and recovery by 300-fold.

Conclusions:

• Immunoglobulin G (IgG) in raw bovine milk acts as a potent rotavirus inhibitor.
• The developed HCl and dithiothreitol treatment method significantly improves rotavirus detection sensitivity in raw milk.
• This improved method is vital for accurate monitoring of rotavirus contamination in the dairy supply chain.