Most vaccines under development have been modelled on the original D-strain of the virus, which was predominant among the sequences published early in the pandemic.

However, the virus’ main strain globally is now the G-strain (accounting for around 85% of published SARS-CoV-2 genomes): a result of a mutation on the main protein on the surface of the virus.

In a study published this month in npj Vaccines​, researchers say there is no evidence this D614F mutation would adversely impact the efficacy of vaccine candidates – important as the majority of candidates target the spike protein.

Biomolecular models 

The study from CSIRO, Australia’s national science agency, vaccinated ferrets with Inovio Pharmaceutical’s DNA vaccine candidate INO-4800 against virus strains both with and without the D614G mutation (This was done in parallel to the pre-clinical trial of INO-4800).

It also created biomolecular models to visualise interactions between vaccine and virus.

The vaccinated ferrets were found to have developed a ‘good B-cell response in terms of neutralising antibodies against SARS-CoV-2 strains’, while researchers are also looking at the T-cell response for long-term efficacy.

They also found that, given the positioning of the G614 variant, a ‘lack of adverse effects on neutralisation efficiency of antibodies generated following vaccination with D614-derived vaccines is not unexpected’.​  

COVID-19 vaccine candidates primarily target the trimeric ‘spike’ (S) glycoprotein, as this factor enables binding to the ‘angiotensin-converting enzyme 2’ (ACE2) host surface receptors and facilitates virus entry into the cells.

In recent months, an Aspartate-to-Glycine amino acid change has arisen at position 614 of the S protein (resulting from a single A-to-G nucleotide change at position 23,403 in the Wuhan-Hu-1 reference genome).

This mutation has led scientists to suggest that the D614G mutation gives the virus a structural advantage; and led to speculation that the efficacy of vaccines and countermeasures which target the S protein could be adversely affected, requiring frequent vaccine matching.

However, the CSIRO study says there is no evidence for this.  

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