![]() ![]() If the changes reduce virus survival, they will be selected against and lost from the population. Not all genetic mutations will result in antigenic changes depending on 1) their position in the triplet code (non-coding changes) or 2) if the change they produce does not affect the region of the protein recognized by the immune system. ![]() Consequently, they will often be surface proteins, like haemagglutinin (HA) or neuraminidase (NA) in the case of the influenza virus.Īntigenic drift is a natural process whereby mutations (mistakes) occur during replication in the genes encoding antigens that produce alterations in the way they appear to the immune system (antigenic changes) (Figure 1). ![]() And the main culprit for their headaches? Antigenic drift and antigenic shift.Īntigens are molecules that are recognized by the host immune system as foreign and induce an immune response. Even with careful research and probability modelling, a certain amount of educated guesswork is involved for manufacturers who select strains to incorporate into the annual vaccine. However, there is no guarantee that the strains predicted to be circulating that year will actually be the ones that do. Many people get their annual flu shots in the hope it will protect them from that year’s seasonal flu outbreaks. The real risk, however, is that two to three significant antigenic shifts could render existing molecular testing assays insufficient, rapid antigen tests useless, and mAbs and non-sterilizing vaccines ineffective.As part of the host-pathogen arms race, viruses are continually evolving to evade the host immune response, be it from previous infection or immunity acquired through vaccination. This begs the question, how many humans have an "inadequate immune response"? With XBB and BQ sublineages fighting for dominance, a new recombinant strain and/or a novel variant could crop up. Some hypothesize that although recombination events are a hallmark of coronaviruses, the Omicron antigenic shift may be from prolonged viral replication in the context of an inadequate immune response -facilitating further mutations. The XBB sublineage and its alarming antibody-evading properties mark a significant antigenic drift and potential shift in SARS-CoV-2. Typically only observed in viruses like influenza, an antigenic shift is an abrupt change in one or both surface antigens resulting in an entirely new variant. Antigenic drift refers to the gradual change in the antigenicity of viral proteins, driven by antibody selection of escape mutants (the mutated antigen 'drifts' from the original variant). With 14 mutations in addition to those found in BA.2, including 9 in the receptor-binding domain (RBD) and 5 in the N-terminal domain (NTD), the XBB sublineage is comparable to the antigenic drift made by the initial Omicron variant from its predecessors one year ago. As predicted, BA.2.75 merged with BA.2.10.1 and spawned XBB/XBB.1.5, street names Gryphon and Kraken. This allows the variants to interact during replication by mixing their genetic materials in the human body to survive.Īnalyzing SARS-CoV-2 patterns and data, we knew it was only a matter of time that BA.2.75 would find its ideal match to mix with and cause another wave of infection. In September of 2022, we blogged about Omicron's BA.2.75 subvariant, citing:Īs BA.2.75 and other subvariants BA.5 and BA.4 all try to outcompete one another, a recombinant strain may emerge due to multiple variants infecting the same person simultaneously. ![]()
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