extracting this molecule from the egg white, new anti-listeria agent

INRA scientists from the poultry research unit have discovered the OVAX protein, a molecule with anti-listeria property. It is present in the egg white of chicken eggs and its function had remained unclear until now. The scientists set up a method to isolate the OVAX protein without modifying its antimicrobial properties.

Jaune et blanc d'un  OEUF  cassé. © MAITRE Christophe
Updated on 01/06/2016
Published on 04/05/2013

Listeria monocytogenes is a foodborne bacterium, responsible for listeriosis, a deadly microbial food-poisoning fatality especially dangerous for pregnant women, as it can cause miscarriage or stillbirth, newborn infants, the elderly and people with compromised immune systems. Infections with L. monocytogenes occur through ingestion of contaminated food (raw milk, deli meat, unpasteurized products, soft cheeses) even stored at 4°C. Symptoms can take up to two months to appear and include fever, muscle aches, gastrointestinal disorders, headaches, stiff neck, loss of balance and even convulsions. Listeriosis displays a high hospitalization rate (97%) and mortality rate (25%) of the patients. Although listeriosis incidence has declined in developed countries, listeria outbreaks are reported each year in the US and Europe and continue to kill. The antibiotic treatments available (penicillin, streptomycin, sulfamids, etc.) are difficult to bear and healing depends on the immune status of the patient. In addition, the development of resistance to antibiotics in some Listeria species and other microbes stresses the need for new strategies to fight this sanitary threat.

INRA’s scientists have discovered a molecule with anti-listeria property. The protein, hereafter “OVAX” (for ovalbumin-related protein X), is present in chicken eggs and more particularly in the egg white. Researchers set up a method based on heparin-sepharose affinity chromatography to eliminate the ovalbumin - the major ingredient in egg white - and isolate a fraction with antimicrobial activity. OVAX accounts for 50% of all proteins in the isolated fraction. The scientists have purified the OVAX protein which was further identified by mass spectrometry.

Although already reported as a component of the egg white (concentration estimated at 0.5 mg/ml of egg white), the function of the OVAX protein remained unknown. INRA’s scientists then assessed the activity of purified OVAX solutions (at different concentrations) on bacteria growth:

  • OVAX solutions reduce the growth of pathogenic Listeria monocytogenes strain EGD
  • there is a dose-dependent effect of the purified OVAX solutions on listeria growth
  • growth reduction effects are observed at concentrations comprised between 25µg/ml - 60 µg/ml
  • the solutions display long-lasting anti-listeria activities on pathogen growth: up to 25 h incubation with the pathogen

Same results were obtained using the heparin-binding fraction of the egg white.

Anti-listeria activity of both the heparin-binding fraction and the OVAX solutions is conserved after treatment with the digestive enzymes trypsin and chymotrypsin which are found in the stomach of human and in the duodenum of ruminant animals, respectively. Recent results demonstrated that OVAX protein also reduces the growth of Salmonella enterica Enteritidis. Currents studies are conducted to investigate the breadth of the antibacterial spectrum of OVAX and its mechanism of action.

The patented invention (WO2011/151407) deals with a new anti-listeria molecule and methods to purify it. This antibacterial agent has a real potential in food safety and for non-food applications, similar to lyzozyme, another antimicrobial substance isolated from egg white.

Contact(s)
Scientific contact(s):

  • Sophie Réhault-Godbert INRA - UR83 Poultry Research Unit, Function and Regulation of Egg Proteins, 37380 Nouzilly, France
INRA Transfert ; 28 rue du Dr Finlay, 75015 Paris, France - Licensing-out officer:
Alice AGASSE (+33 (0) 142 759 354)