Plant-derived antiviral drug could combat Delta variant

A novel antiviral drug called thapsigargin (TG) blocked COVID-19 infection in cells, including all new variants, in a pre-clinical study.

Blood test showing positive for COVID-19 Delta variant

Researchers at the University of Nottingham, UK, have discovered a plant-based antiviral treatment for COVID-19 that is just as effective at treating all variants of the virus SARS-CoV-2, including the highly infectious Delta variant.

The team found that the Delta variant, compared with other recent variants, showed the highest ability to multiply in cells, and was most able to directly spread to neighbouring cells. In co-infections with two different SARS-CoV-2 variants, the Delta variant also boosted the multiplication of its co-infected partners. The study, published in Virulence, also showed that a novel natural antiviral drug called thapsigargin (TG), was just as effective at treating all of the newer SARS-CoV-2 variants, including the Delta variant.

The team initially set out to find out how well the emergent Alpha, Beta and Delta variants of SARS-CoV-2 are able to multiply in cells relative to each other as single variant infections and in co-infections. They also investigated how effective TG was at blocking these emergent variants. 

Of the three, the Delta variant showed the highest ability to multiply in cells, and was most able to spread directly to neighbouring cells; its amplification rate at 24 hours of infection was over four times that of the Alpha variant and nine times more than the Beta variant. In co-infections, the Delta variant boosted the multiplication of its co-infected partners. Furthermore, co-infection with Alpha and Delta or Alpha and Beta conferred multiplication synergy, where total new virus output was greater than the sum of corresponding single-variant infections.

However, all SARS-CoV-2 variants were highly susceptible to TG treatment. A single pre-infection priming dose of TG effectively blocked all single-variant infections and every co-infection at greater than 95 percent relative to controls. Moreover, TG was effective in inhibiting each variant during active infection.

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“Our new study has given us better insights into the dominance of the Delta variant. Even though we have shown that this variant is clearly the most infectious and promotes production of other variants in co-infections, we are pleased to have shown that TG is just as effective against all of them,” commented lead author Professor Kin Chow Chang. “Together, these results point to the antiviral potential of TG as a post-exposure prophylactic and an active therapeutic agent.”