Overview: a nasal probiotic shield against respiratory viruses
Respiratory viral diseases threaten pig health and global food security, especially in intensive farming. Classic vaccines against viruses like porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), pseudorabies virus (PRV), and porcine epidemic diarrhea virus (PEDV) often fail to deliver lasting protection due to viral mutations and coverage gaps. In this context, a breakthrough study from Nanjing Agricultural University identifies a natural bacterial strain that resides in the nasal mucosa and acts as a broad-spectrum antiviral barrier.
The discovery: NS12, a wild-type Bacillus subtilis from outdoor pigs
Researchers isolated a wild-type Bacillus subtilis strain, NS12, from the nasal passages of pigs with outdoor access. Epidemiological data linked outdoor living to lower nasal carriage of respiratory viruses, a pattern strongly associated with higher levels of B. subtilis in the nasal cavity. NS12 demonstrated a remarkable ability to persist on mucosal surfaces for up to two weeks and secrete antiviral metabolites capable of neutralizing a broad panel of enveloped viruses.
Evidence from animal models
In controlled experiments, NS12 provided protection to piglets against PRRSV and PEDV infections. Treated piglets showed reduced viral loads, mitigated tissue damage, and improved survival rates. Additional testing in a mouse model showed that NS12 treatment conferred strong protection against PRV challenge, suggesting genuine cross-species antiviral activity and broad-spectrum potential.
Dual antiviral metabolites: surfactin derivatives and piceatannol
Two key antiviral compounds secreted by NS12 drive its protective effects. First, novel surfactin derivatives (C16/C17) are safer and less cytotoxic than standard surfactin. These cyclic lipopeptides disrupt viral envelope phospholipid dynamics, hindering membrane fusion with host cells. Second, piceatannol—a hydroxylated stilbene phenolic compound—binds viral envelope lipids, increases membrane lipid saturation, and reduces fluidity, thereby blocking viral entry without dismantling the viral particle itself. Together, these metabolites create a “molecular firewall” on the nasal mucosa that resists infection by enveloped respiratory viruses.
Implications for sustainable antiviral strategies in pig farming
The study shows that a naturally occurring nasal probiotic can actively inhibit viral invasion through metabolite-mediated mechanisms. Unlike vaccines, which target specific viral antigens, NS12 acts at the level of the viral envelope—derived from host membranes—making it harder for viruses to escape via mutation. Professor Qian Yang, the study’s corresponding author, notes this approach could complement existing vaccines and reduce reliance on them in the long term.
Future directions: practical applications and human relevance
The researchers envision several practical implementations of NS12, including intranasal probiotic sprays, functional feed additives, or even next-generation veterinary antivirals. Because the mechanism targets the viral envelope, there is potential for application beyond pigs, possibly extending to human respiratory infections such as influenza and coronaviruses, though human studies would be required. If validated in broader settings, NS12-based products could help protect pig herds, reduce mortality, and contribute to more sustainable livestock production while addressing concerns about antiviral resistance.
Conclusion
NS12 represents a novel use of the nasal microbiome to combat respiratory viruses through a metabolite-based barrier. By combining safer surfactin derivatives with piceatannol, this Bacillus subtilis strain creates a durable, broad-spectrum antiviral effect at the site of viral entry. As the livestock industry seeks resilient, biology-based strategies, NS12 could become a cornerstone of next-generation antiviral interventions in animal health.
