Oral Circovirus Vaccines Studied
By Pork news staff
| Tuesday, September 23, 2008
Although effective commercial porcine circovirus type 2 vaccines are available to the nation’s pork industry, the study for even more protective vaccines continues. Efficacious oral vaccines that protect pigs against PCVAD would have a substantial impact on the swine industry.
If the use of these vaccines also allows differentiation between infected and vaccinated animals, producers will have a cost-effective method to deliver vaccines and monitor their usefulness.
Porcine circovirus type 2 has had a severe negative economic impact on the industry. However, conventional vaccines have proved a valuable and highly effective means of prevention. In order to make an even more effective vaccine, Wang, et. al explored the idea of using a vaccine delivery method that would induce immunity at the level of mucous membranes (such as the respiratory or intestinal tract), called mucosal immunity, and whole body immunity, called systemic immunity. An attractive candidate for such vaccine delivery is lactic acid bacteria.
Lactic acid bacteria are considered safe as they are neither pathogenic nor do they tend to spread. They can be given orally and will pass through the lining of the intestinal tract without causing known adverse effects. Experimental vaccines delivered using lactic acid bacteria are thought to be able to induce both mucosal and systemic immunity in the animal. Depending on the site of delivery of the vaccine, immunity may be altered and directed to the gastrointestinal, reproductive and respiratory tracts.
To develop the new vaccine, Wang’s group inserted PCV2 DNA molecules into the non-invasive, non-pathogenic lactic acid bacteria. Subsequently, the manipulated bacteria were used as an oral delivery system for the PCV2 “vaccine." The success of this technique was evaluated using a model that included administering the new vaccine to mice orally and later testing the animals for an immune response.
The researchers found that mice that had been given the bacteria with the PCV2 capsid protein had an immune response that was eight times greater than that of the controls. They concluded that transformed lactic acid bacteria show promise as a novel vehicle for oral vaccination and for inducing immunity to PCV2 proteins in animals. This technique may represent a new generation of vaccines where needles are never used.
Source: National Pork Board
