Overview: A natural defense emerging from the pig nose
Respiratory viral diseases pose a substantial threat to animal health and global food security, especially in intensive pig farming. Viruses such as porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), pseudorabies virus (PRV), and porcine epidemic diarrhea virus (PEDV) can sweep through herds, causing high piglet mortality, reproductive failures in sows, and enormous economic losses. Traditional vaccines have struggled to keep pace with viral mutations, providing only partial and sometimes short-lived protection. In this context, researchers at Nanjing Agricultural University report a promising, natural antiviral strategy: a wild-type strain of Bacillus subtilis, NS12, residing in the nasal mucosa of outdoor pigs that can actively block viral infections at the entry point.
The nasal probiotic shield: how NS12 works
Field epidemiology showed that pigs with outdoor access harbored fewer respiratory viruses, a finding linked to an enrichment of Bacillus subtilis in the nasal cavity. By isolating NS12, scientists demonstrated that this strain can persist in the nasal mucosa for up to two weeks and secrete potent antiviral metabolites. These secretions form a direct barrier against a broad panel of enveloped viruses, reducing the chance that viruses will successfully attach and enter host cells.
In controlled experiments, NS12 protected piglets against PRRSV and PEDV infections, lowering viral loads, mitigating tissue damage, and improving survival. A parallel mouse study showed strong protection against PRV, indicating that the antiviral effect crosses species barriers and may have broad relevance beyond swine health.
Two key antiviral metabolites: surfactin derivatives and piceatannol
The researchers identified two main antiviral metabolites produced by NS12 that work together to defend the nasal mucosa:
- Novel surfactin derivatives (C16/C17) — These cyclic lipopeptides disrupt viral envelope phospholipid dynamics and prevent membrane fusion with host cells. Importantly, these derivatives are reported to be safer and less cytotoxic than standard surfactin, making them more suitable for continuous mucosal exposure.
- Piceatannol — A hydroxylated stilbene phenolic compound that binds viral envelope lipids, increases membrane saturation, and reduces fluidity. By altering the envelope properties, piceatannol hinders viral entry without destroying the virus itself or damaging host tissue.
Together, NS12-secreted metabolites create a “molecular firewall” on the nasal surface, offering a broad-spectrum antiviral barrier against enveloped respiratory viruses.
Implications for vaccination and disease control
This study presents a paradigm shift in managing respiratory viruses in livestock. Unlike vaccines that target specific viral antigens, NS12 acts at the level of the viral envelope—a feature derived from host cells—making resistance through mutation less likely. The nasal mucosa, as the first line of defense, provides a strategic target for preventing viral invasion before systemic infection occurs.
Potential applications include intranasal probiotic sprays, functional feed additives, or next-generation veterinary antivirals. The concept of a natural nasal probiotic offering broad protection could complement existing vaccines, reduce antibiotic reliance, and contribute to sustainable farming practices.
Broader relevance: possible human health implications
While the current work focuses on pigs, the envelope-directed mechanism may translate to human respiratory viruses such as influenza and coronaviruses. If safety and efficacy are demonstrated in humans, similar nasal probiotic strategies could complement vaccination, particularly in populations with limited vaccine coverage or during emerging outbreaks.
Looking ahead: where science and farming intersect
Professor Qian Yang and colleagues see NS12 as a versatile tool for controlling respiratory diseases in livestock while offering a blueprint for stress-tested, naturally derived antivirals. As researchers pursue clinical trials, regulatory evaluations, and scalable production methods, NS12 could become part of an integrated approach to animal health that emphasizes the microbiome as a frontline defender against pathogens.
Bottom line
Natural nasal probiotics like Bacillus subtilis NS12 hold promise for broad-spectrum antiviral protection in pigs by deploying two antiviral metabolites that disrupt viral envelopes. This strategy could complement vaccines and help safeguard animal health and food security in the face of evolving respiratory viruses.
