New Delhi: The Omicron variant, which has health authorities worried across the world, may have emerged from a patient with HIV/AIDS and a prolonged Covid-19 infection, South African scientists tracking the new coronavirus variant believe.
This, however, may not be the first time that such mutations have emerged.
Several cases through the pandemic have shown that prolonged infection, which allows the virus to replicate for a longer duration, along with a compromised immune response leads to the emergence of immune escape mutations — or mutations that make the virus less susceptible to antibodies.
Simply put, mutations are small errors or ‘typos’ in the genetic coding of the virus that occurs when the virus is replicating itself. Sometimes these changes in the genetic codes can change a protein in the virus that effectively improves one of its functions, such as its infectiousness or the disease severity.
In case of the coronavirus, this replication can only occur inside the body as viruses cannot replicate outside a host cell.
A prolonged infection, in the absence of a healthy immune system, thus can create the perfect environment for new mutations to emerge.
Not the first such case
A study published in the journal Nature February this year, for example, showed data from one immunocompromised patient who died after 102 days of being Covid positive.
By sequencing samples taken on 23 different days over a span of 102 days, a team from University of Cambridge in the UK showed that mutations that spread more easily and/or can escape antibodies can emerge in immunocompromised patients who stay Covid positive for prolonged periods.
In this case, the patient, over 70 years of age, was undergoing chemotherapy for lymphoma. Lymphoma is a cancer that begins in cells of the lymph system or the body’s disease-fighting network.
The patient was initially treated with two courses of Remdesivir over 57 days, but the medication failed.
The patient was then administered convalescent plasma, which at the time of the study was still an experimental therapy with the potential to treat Covid.
The team, however, observed that after the plasma therapy began, the virus started mutating more rapidly.
Researchers said it is likely that both chemotherapy and underlying lymphoma contributed to combined immunodeficiency of B and T cells — white blood cells that play a key role in the body’s immune response.
The Harvard case study
Last year, in a letter published in The New England Journal of Medicine (NEJM), researchers from Harvard Medical School described the case of an immunosuppressed Covid positive patient who was treated with a mix of anticoagulants, steroids, and antivirals.
During 152 days of persistent SARS-CoV-2 infection in the patient, the team identified as many as 12 mutation spikes in the spike protein, some of which were linked to immune evasion.
Based on several such reports reported through the pandemic, researchers from several institutions in the US had written in an article published in the NEJM, noting that there is a need to identify whether certain forms of immunosuppression are associated with an increased risk of giving rise to immune escape mutations, such as specific cancers or therapies, prolonged use of glucocorticoids, long-term chemotherapy, or radiotherapy.
“Similarly, organ transplant recipients and those with untreated or poorly controlled human immunodeficiency virus infection may also have prolonged SARS-CoV-2 infection and could constitute a reservoir of divergent escape variants that can spread in the general community,” the researchers said.
They explained that prolonged viral replication along with inadequate immune response facilitates the emergence of immune escape mutations.