A new two-in-one medicine treats and prevents viral infections –– the first to accomplish both. So far, the so-called “quasi-vaccine” has only been tested on mice, but it could be instrumental in the event of another pandemic, especially if the virus is unknown or does not yet have an effective vaccine.
The quasi-vaccine, which contains tiny gold particles, works by targeting a virus’s glycan shield, blocking the virus from infecting the host while provoking an immune response, prompting the rapid creation of antibodies. In mice, the nanomedicine was effective against live porcine deltacoronavirus, which was studied as a proof of concept.
“This approach fully utilizes the viral inactivation mechanisms of nanomaterials and the antiviral immunity of the host,” said Zhen Liu, one of the quasi-vaccine’s developers and a professor at the State Key Laboratory of Analytical Chemistry for Life Science at Nanjing University, China.
Liu says that the current antivirals and vaccines have several major disadvantages that can be overcome using nanomaterials.
Nanomedicines as next-generation vaccines
Given the growing issue of multidrug resistance as well as the limited protection offered by conventional vaccines and mRNA vaccines, which must be routinely reformulated to keep up with virus evolution, new vaccine technologies that offer broad-spectrum protection against multiple viruses are needed.
These vaccines are typically injected into muscle and can take weeks to kick in. The quasi-vaccine developed by Liu and his team is inhaled through the nose and immediately takes effect when exposed to near-infrared light. Benefitting from the abundant immune cells in the respiratory tract, antibodies are secreted in response to pathogens. Intranasal medications are also non-invasive, painless, and self-administrable, with a reduced risk of cross-contamination.
As an alternative to conventional vaccines, gold nanoparticles are promising due to their antiviral and antibacterial properties. Not only does their size matter, but also their shape –– for example, nanoparticles in the form of spheres, triangles, stars, or rods have different properties. Gold nanorods are particularly effective at absorbing near-infrared light and have been used to treat tumors, killing cancer cells by overheating them.
Liu and his team harnessed this same effect –– heat generation –– to kill viruses.
Combined antiviral and vaccine-like effects
To design the quasi-vaccine, the researchers considered a vital part of the virus structure: the glycan shield. Viral glycan shields, especially the so-called high-mannose glycan modification, are found on the surfaces of many viruses, including HIV-1, influenza, and SARS-CoV-2, and serves as their main defense.
To target the high-mannose glycans on this shield, the researchers modified the surfaces of the gold nanorods with specific biomolecules, called aptamers, that can tightly bind to it. In mice, they tested its efficacy against live PDCoV virus, a novel intestinal coronavirus that normally affects pigs but carries the risk of cross-species transmission, including to humans.
The mice were exposed to the PDCoV virus through inhalation, and then the nanomedicine was applied to their nasal cavities. After 10 minutes of near-infrared light exposure, the nanorods heated to around 55 °C, splitting the bound virus into pieces and inactivating it in the process.
The nanomedicine’s vaccine-like effects arise from this inactivation process.
“It is not the nanomedicine itself that causes the virus long-term protection effect, but the viral fragments generated by the irradiation of near-infrared laser,” Liu explained.
Twenty-four hours after treatment, Liu and his team found that mice exposed to these viral fragments produced a variety of molecules that signal immune system activation. By 72 hours, their immune systems had returned to normal, demonstrating that the strategy not only activated immunity effectively but also avoided severe adverse reactions.
The mice that were boosted using the same protocol one week after the first treatment, and again two weeks after, had high concentrations of antibodies in their blood, demonstrating that the strategy had a vaccine-like effect.
A bold pandemic response strategy
In the event of a virus outbreak, time is critical, especially for healthcare workers on the frontlines who have a high risk of exposure. Liu and his team believe their immunization strategy would save valuable time, and possibly lives, in this scenario.
Similar to their immunization protocol in mice, after a person is exposed to a virus through inhalation, the nanomedicine could be delivered intranasally and then irradiated with the near-infrared laser. The inactivated virus fragments that remain in the respiratory system would activate the immune response and provide vaccine-like protection for potential future exposures. If necessary, the cycle could be repeated several times to maximize the immunization effect.
Even if an effective vaccine was already available, its protective effects would not be immediate, the researchers pointed out. The nanomedicine solves this issue, controlling virus invasion at its infancy, slowing the outbreak, and buying time for the development of other antiviral agents.
Although the initial toxicity studies conducted by Liu and his team show that the nanomedicine is biocompatible with mice, its biosafety needs to be evaluated in humans.
But first, studies in larger animals, such as dogs and non-primates, could be conducted to accelerate its clinical translation to humans, Liu said.
Ensuring that the antiviral immune response is sufficient while simultaneously preventing viral infection of the host is key, he emphasized.
Liu is optimistic that this new double-pronged approach will be widely adopted in the future.
“It is anticipated that, in the near future, broad-spectrum antiviral agents based on this platform will significantly alleviate the burden of viral infections on public health and contribute to the establishment of a more robust and secure public health defense system,” he said.
Reference: Jingran Chen et al. An Intranasal Nanomedicine Functions as Both Potent Broad-spectrum Viral Inhibitor and Quasi-Vaccine. Advanced Functional Materials (2025). DOI: 10.1002/adfm.202501533
