The CDC has updated their variants of concern (VOC) list to include two more strains of COVID-19.
Please see my previous article, “What COVID-19 Variants are Out There?” for information on other VOC’s that were listed earlier in the year.
The CDC has now acknowledged two new “home-grown” VOC’s, both first detected in California. These are the B.1.427 and B.1.429 variants, detected for the first time in January 2021, and added to the CDC’s list on March 24, 2021.
Increased transmissibility is the hallmark of VOC’s, and the California strains are no exception, with up to 24% higher transmissibility than the baseline. These two forms are collectively referred to as the “California variant”, although they are two separate strains, genetically. Both B.1.427 and B.1.429 share many similarities, including two specific gene mutations– D614G and L452R–both affecting the function of the spike protein, which is responsible for interacting with human cells to initiate infection. The D614G mutation is also found in the South African and Brazilian variants, indicating its well-conserved efficacy in increasing transmission. The convergent evolution of several variants is concerning, since it shows that mutation reliably gives the virus an evolutionary advantage.
The California variant has also been shown to evade human immune response more efficiently than the original variant. Monoclonal antibodies, used in treatment of severe COVID-19, are less effective against it. In fact, the U.S government no longer supplies three states– California, Nevada, and Arizona– with the drug bamlanivimab, due to the prevalence of the variant there and the inefficacy of monoclonal antibody treatments against it. Specifically, the L452R mutation seems to be driving this immune evasion.
Monoclonal antibodies are lab-grown antibodies designed to mimic the action of the body’s naturally produced ones. Drugs based on monoclonal activity to treat severe COVID-19 will be less effective as a result. This new variant is more successful at evading immune response than the ones preceding it, and since mRNA vaccines (like the ones used to prevent COVID-19) are responsible for generating antibodies to combat the virus, they may not be as effective against this variant, although researchers do not believe they will be totally ineffective, either.
The viral load in patients with the California variant is also seen to be significantly higher than that of other variants, with twice as many viral particles present in their nasal passages; another clear sign of increased transmissibility.
The prevalence of this variant is concerning, now with 56% of documented cases in California being one of the two sister variants. The increasing conservation of genes relating to higher transmissibility and increased immune evasion genes is concerning, especially as we see the Brazilian variant re-infecting a population of people who have already had and recovered from COVID-19. This unexpected spike in reinfection indicates that antibodies produced naturally as a response to original lineages of COVID-19 may not have an effect against the new Brazilian variant–and the California variant, with its similar mutations, might show the same worrying traits.