Researchers have developed an intranasal anti-viral treatment for Covid-19 that decreases the amount of SARS-CoV-2 shed from infected animals and limits transmission of the virus.
By the time people test positive for Covid-19, the SARS-CoV-2 virus has already taken up residence in their respiratory system. With each breath, people expel invisible viral particles into the air -- a process known as viral shedding.
Existing drugs aimed at treating Covid-19 address symptoms of the virus but do little to quell viral shedding.
Researchers at Gladstone Institutes in the US previously developed a novel approach for treating infectious diseases: a single-dose, intranasal treatment that protects against severe SARS-CoV-2 infection.
In a new study published in the journal Proceedings of the National Academy of Sciences, they show that this treatment, called a therapeutic interfering particle (TIP), also decreases the amount of virus shed from infected animals and limits transmission of the virus.
"Historically, it has been exceptionally challenging for antivirals and vaccines to limit the transmission of respiratory viruses, including SARS-CoV-2," said Gladstone investigator Leor Weinberger, senior author of the new research.
"This study shows that a single, intranasal dose of TIPs reduces the amount of virus transmitted, and protects animals that came into contact with that treated animal," Weinberger said.
The researchers noted that it is the only single-dose antiviral that reduces not only symptoms and severity of Covid-19, but also shedding of the virus.
Weinberger and Sonali Chaturvedi, a research investigator at Gladstone and first author of the research, treated hamsters infected with SARS-CoV-2 with the antiviral TIPs and then measured, daily, the amount of virus in the animals' noses.
Compared to hamsters that had not received the TIPs (called control animals), treated animals had less virus in their nasal passages at every time point.
By day 5, all control animals were still shedding high levels of virus, while the virus was undetectable in four out of five TIP-treated animals, the researchers said.
"We know that the amount of virus shed is proportional to how infectious someone is," said Weinberger.
"If viral shedding can be reduced, the number of secondary contacts likely to become infected will also very likely be reduced, which will in turn decrease overall virus dissemination and help keep vulnerable individuals safe," he said.
When the SARS-CoV-2infected animals were housed in cages with uninfected animals, treatment of the infected animals with TIPs did not fully prevent the transmission of Covid-19, the researchers said.
However, it did lead to significantly lower viral loads and milder symptoms of infection in the newly exposed animals, they said.
"This particular laboratory setting is known to generate much more efficient transmission than typically seen in humans, even in household settings, because the hamsters not only transmit via aerosols, but also through bodily fluids and by climbing over and grooming each other for many hours," said Weinberger.
"So, being able to reduce SARS-CoV-2 transmission in this animal setting is quite promising for being able to reduce human-to-human transmission," he added.