Coronaviruses (CoV) are able to infect the human respiratory tract and subtypes 229E, NL63, HKU-1 or OC43 are frequently detected during common colds. Other CoV strains infect animals but recent history has seen two cases of animal-to-human transitions, leading to the epidemic of Severe Acute Respiratory Syndrom (SARS) in 2003 and in recent years to outbreaks of Middle-East-Respiratory-Syndrome (MERS).
We tested the antiviral hydroalcoholic extract (65% V/V) of freshly harvested Echinacea purpurea herb and roots (Echinaforce®, EF) on Coronavirus 229E and also the highly pathogenic MERS-type. CoV 229E (105 tissue culture infectious dose, TCID50) and MERS-CoV (1.6x104 TCID50) were incubated with 0, 1, 10 and 50 μg/ml EF for 1 h and remaining infectivity assessed by determining TCID50 on HuH-7 and Vero cells. EF showed a dose dependent reduction of CoV 229E infectivity with an IC50 = 9 +/-3 μg/ml. Complete neutralization was achieved with 50 μg/ml. Similar inhibition was observed for MERS-CoV, where 10 μg/ml EF reduced > 99.9 % and 50 μg/ml fully blocked infectivity. Interestingly, virus inhibition was only seen upon direct exposition of virus to the extract. Corresponding tests with other viruses showed that membranous RNA-viruses such as Influenza, Yellow fever virus were also neutralized by EF, while infectivity of DNA-viruses such as Parvo- and Vaccinia virus were not altered by EF.
In summary, pre- and post-incubation experiments show that EF has the potential of inhibiting infection rather than the dissemination of Coronaviruses. Our data are in agreement with the results of a placebo controlled study, where 4-months Echinaforce® prevention significantly reduced membranous virus infections overall (p = 0.0114), and Coronavirus infections in particular: 33 infections in N=362 with placebo i.c. to 21 infections in N=355 with EF [1].
[1] Jawad M, et al. ECAM. 2012: 841315. Epub 2012 Sep 16.