Like all RNA viruses, SARS-CoV-2 is prone to mutations—adaptive changes that can alter a virus’ pathogenic potential and other characteristics. These mutations can create distinct variants of the virus, adding complexity to what has already become the most significant global public health challenge since the 1918 influenza pandemic.
On June 15, 2021, the World Health Organization (WHO) classified the Lambda strain (also called C.37) of SARS-CoV-2 as a variant of interest. Variants of interest carry mutations that may increase transmissibility and disease severity and have been detected in multiple countries.
The earliest documented samples of the Lambda variant were documented in Peru in August 2020. While the strain only accounts for roughly 1 percent of COVID-19 cases in the US as of October 2021, its rapid spread through South America, particularly in Chile, Peru, Ecuador, Colombia, and Argentina makes it worth watching closely.
What do the mutations in Lambda mean?
Lambda carries mutations that have several important public health implications, including the potential for increased transmissibility and increased resistance to neutralizing antibodies. The mutations are specific to the spike protein of the virus and include del247/253, G75V, T76I, L452Q, F490S, D614G, and T859N. The first mutation in the list represents a deletion while the rest represent the replacement of an amino acid, the building blocks of proteins, at the specific position in the spike protein of the virus (e.g., G75V represents a change from the amino acid glycine to valine at position 75 in the protein chain.)
Specifically, the T76I (a threonine in the protein structure replaced with isoleucine) and L452Q (a leucine amino acid replaced with glutamine) mutations are responsible for making Lambda highly infectious. Scientists are still working to understand the mechanisms that increase transmissibility for these specific mutations (and not others). Further studies will ultimately help scientists, doctors, and public health experts develop specific control and treatment measures to curb the infection.
Is the Lambda variant responsive to vaccines?
Neutralizing antibodies are produced as a part of the immune response to vaccinations or viral invaders. A neutralizing antibody might block interactions of the virus with host cells, or it might bind the virus in a manner that prevents it from expelling its nucleic acids into the host cells. After vaccinations or viral infections, neutralizing antibodies persist in the host to protect against future infections. A recent report showed that the Lambda variant was 1.5-fold more resistant to vaccination-induced neutralizing antibodies as compared with the wild-type strain of the virus.
However, these results do not mean the human immune system completely fails to respond to the virus. It also doesn’t mean that the COVID-19 vaccines do not work. A recent study of 13 US jurisdictions by the CDC showed that the rates of COVID-19 cases, hospitalizations, and deaths were substantially higher in people who were not fully vaccinated. Furthermore, another study showed that the Lambda variant could be neutralized using therapeutic monoclonal antibodies from Regeneron.
Do current tests detect Lambda?
While most tests on the market cannot definitively tell which SARS-CoV-2 variant a person has without genomic sequencing, Seegene’s PCR-based multiplex NovaplexTM SARS-CoV-2 Variants Assays are designed to detect multiple variant mutations in a single tube.
These assays are currently for Research Use Only (RUO) and therefore should not be used for diagnostic purposes in the United States. However, researchers studying the mechanisms of disease for SARS-CoV-2 variants can depend on our tests to detect variants of interest including the Lambda variant.
What should public health strategies look like?
Scientists are still on alert for more changes in the viral genome. As SARS-CoV-2 continues to spread, it has more opportunities to evolve. Thus, reducing transmission through established and proven disease control methods—such as those outlined in the COVID-19 Strategic Preparedness and Response Plan—should be a fundamental part of our global strategy to reduce the occurrence of mutations that have negative public health implications.
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