Immunology: Plant-derived CoVLP COVID-19 vaccine candidate proven successful in phase 1 trial

The plant-derived candidate vaccine against COVID-19 known as ‘CoVLP’ was well tolerated and elicited an immune response both with two different adjuvants and without, according to a phase 1 clinical trial published in Nature Medicine. After two doses of CoVLP with an adjuvant, participants developed neutralizing-antibody levels at least comparable to those seen in people recovering from COVID-19.

Several vaccines against COVID-19 have received approval, but no single vaccine can be produced in sufficient quantities to address the global need fast enough, and different formulations may be required for varied populations and environments. One such formulation is CoVLP, a virus-like-particle candidate vaccine that incorporates the SARS-CoV-2 spike protein, produced in the plant, Nicotiana benthamiana.

Brian Ward and colleagues designed an observer-blinded, dose-escalation, randomized controlled study to determine the effective dosage and success of CoVLP in eliciting neutralizing antibodies and cellular responses. Between 13 July and 9 August 2020, 180 adults (from 18 to 55 years of age) received two doses of CoVLP—separated by 21 days—alone or with either AS03 or CpG1018 adjuvants, at random. An adjuvant is a substance used to increase the potency of a vaccine. On day 42, the authors observed that without an adjuvant, CoVLP elicited a modest immune response. However, the presence of either adjuvant enhanced the response markedly. On day 42, participants who received CoVLP with AS03 produced neutralizing antibodies at levels 10 times higher than those seen in patients recovering from COVID-19.

The authors conclude that further development of this CoVLP formulation with AS03 should be supported. On the basis of the available data, a two-dose schedule of CoVLP at 3.75 µg per dose with AS03 has entered into a large phase 2/3 studies in Canada, the UK, Brazil and the USA, with planned expansion to further countries in Latin America and Europe.