London, Nov 21 (IANS): A plant-based antiviral treatment for Covid-19 has found to be effective at treating all strains of Covid-19, even the highly infectious Delta variant.

Scientists at the University of Nottingham in the UK found that the Delta variant, compared with other recent strains, 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 also showed that a novel natural antiviral drug called thapsigargin (TG), recently discovered by the same group of scientists to block other viruses, including the original SARS-CoV-2, was just as effective at treating all of the newer SARS-CoV-2 variants, including the Delta variant.

In their previous studies, the team showed that the plant-derived antiviral, at small doses, triggers a highly effective broad-spectrum host-centred antiviral innate immune response against three major types of human respiratory viruses, including SARS-CoV-2.

In this latest study, published in the journal Virulence, the team 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- where cells are infected with two variants at the same time.

The team also wanted to know just 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.

Notably, 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 per cent relative to controls.

Likewise, TG was effective in inhibiting each variant during active infection.

"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," said lead author Professor Kin Chow Chang at the School of Veterinary Medicine and Science at the University.

"Together, these results point to the antiviral potential of TG as a post-exposure prophylactic and an active therapeutic agent," Chang added.