As the COVID-19 pandemic approaches its second year, we still don't know much and we still have a lot to learn about the antibodies that we produce in response.
How long does the body keep the proteins made by the immune system, which gives us some protection against the virus, for? How do different coronavirus variants affect antibodies? And how does vaccination-based immunity compare to antibodies that were produced from prior infections?
A new study by scientists from the UK has provided some new insights to help us address these unanswered questions.
First, some good news. The data shows that the antibodies in blood from people who were infected during the first wave pandemic, and then recovered, can be retained for at least 10 months after onset of symptoms (POS).
"Initial concerns were that SARS-CoV-2's antibody response might mimic other human endemic coronaviruses such as 229E for which antibody responses can be short-lived, and re-infections occur," says Liane Dupont, first author of the paper.
"Our data, along with other studies, show that even though neutralizing antibody levels decline from an initial peak reaction, strong neutralizing activity can still be detected at up to 10 month POS in convalescent sera."
Dupont and co-researchers examined convalescent sera of 38 people in a new study. This was a mixed group of patients and healthcare workers who were all infected with wave 1.
An earlier study by the same team revealed that SARS-CoV-2 antibody concentrations began to decline after peaking at approximately three to five weeks POS. It wasn't clear if this drop continued beyond the three-month point.
The newer data shows some encouraging signs. First, convalescent sera still contained neutralizing antibodies for up to 10 years after the end of the study.
There was evidence that SARS-CoV-2 variants could be cross-neutralized. This means that people who have been exposed to only the original wild type SARS-CoV-2 may still have some protection against later, mutated versions, but at lower levels.
Researchers write that wave 1 sera had neutralizing activity against B.1.1.7 [aka Alpha variant], P.1[Gamma]and B.1.351 [Beta] but at a lower level for B.1.1.7 or B.1.351."
Other results indicated that infection with SARS-CoV-2 variants, including B.1.617.2, aka Delta, "generates an effective cross-neutralizing antibody reaction that is effective against parental virus, but has reduced neutralization towards divergent lineages", according to the researchers. They also note that vaccines made using spike protein from the original virus will likely provide the strongest antibody response against current variants and new lineages.
It is worth noting, however, that laboratory experiments measuring antibody activity under glass are not the same as testing people's ability against the virus in real-life. However, there are still promising results here, which could be used for vaccine research and design.
Researchers write that "Sustained neutralization against infecting SARS CoV-2 variants is critical, but efficacious cross-neutralizing activities are essential for long-term protection from emerging SARS CoV-2 variants."
"Observations indicate that COVID-19 vaccine booster could be an important step to increase both neutralization breadth as well as vaccine efficacy against the newly emerging SARS/CoV-2 variants.
Nature Microbiology reports the findings.