SARS-CoV-2 infection aided by antibody-dependent enhancement

The coronavirus disease 2019 (COVID-19) pandemic spread rapidly around the world, leading to lockdowns, social distancing measures, and millions of deaths. However, with the help of mass vaccination campaigns and monoclonal antibody treatments, the transmission of the disease is beginning to slow down.

Vaccines rely on the immune systems ability to produce specific antibodies – most vaccines designed to effect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) target the receptor-binding domain (RBD) of the S1 subunit of the spike protein, as this is responsible for viral cell entry through binding to angiotensin-converting enzyme 2 (ACE2). However, some viruses (including SARS-CoV-2) have an alternative method of infection known as an antibody-dependent enhancement of infection (ADE). It is one of the most significant risks for both vaccines and monoclonal antibody treatment and is of special concern given the rise of variants of concern such as the Delta variant – which is known to evade vaccine-induced immunity.

A group of researchers from the University of Wisconsin-Madison has been investigating the mechanisms and impact of ADE in SARS-CoV-2. A preprint of the groups' findings can be found in the journal mBio published by the American Society For Microbiology.

In ADE an immune complex of virus and non-neutralizing or cross-reactive antibodies binds to receptor molecules called Fcy receptors (FcyRs) on macrophages and monocytes. These cells then internalize the complex, allowing the virus to enter the cell.

Both SARS-CoV-1 ad MERS-CoV showed the ability to enter cells through ADE, and several studies have confirmed that SARS-CoV-2 has the same ability using FcyRIIA. Still, it is unknown whether FcyRIA or FcyRIIIA are also involved.

The researchers generated baby hamster kidney (BHK) cells expressing the three FcyRs or ACE2. Wild-type BHK cells are not susceptible to infection by SARS-CoV-2, and as such, they make an ideal model to test whether the transfected proteins mediate ADE. BHK cells were infected with a luciferase-expressing vesicular stomatitis virus pseudotyped with SARS-CoV-2 spike (VSV-SARS2-S). Luciferase activity was evaluated 24 hours post-transfection. Only the BHK cells that were expressing ACE2 proved susceptible to VSV-SARSS2-S transfection. Following this, the scientists used 15 convalescent-phase plasma samples randomly selected from a total of 110 samples, and one sample from an uninfected individual. The transfected FcyR BHK cells were then infected with VSV-SARSS2-S that had been incubated with these samples. No luciferase signals were detected at all, suggesting none of the FcyRs mediate ADE in BHK cells.

ADE of SARS-CoV-2 infection is mainly mediated by FcγRIIA and FcγRIIIA. (A to E) Serially diluted convalescent-phase plasma from five individuals and two control plasma samples incubated with VSV-SARS2-S were used to infect the indicated cells that had been transfected with an hACE2 expression vector; the luciferase activity in the cell lysates was determined at 24 hpi. The experiment was performed with duplicate samples; means and standard deviations (SD) are shown. (F) Serially diluted convalescent-phase plasma from two individuals and two control plasma samples incubated with VSV-SARS2-S were used to infect the indicated cells, and the luciferase activity in the cell lysates was determined at 24 hpi. The experiments were performed in duplicate; means and SD are shown. Statistical analysis was performed using an unpaired t test. ***, P < 0.001; **, P < 0.01; *, P < 0.05.
ADE of SARS-CoV-2 infection is mainly mediated by FcγRIIA and FcγRIIIA. (A to E) Serially diluted convalescent-phase plasma from five individuals and two control plasma samples incubated with VSV-SARS2-S were used to infect the indicated cells that had been transfected with an hACE2 expression vector; the luciferase activity in the cell lysates was determined at 24 hpi. The experiment was performed with duplicate samples; means and standard deviations (SD) are shown. (F) Serially diluted convalescent-phase plasma from two individuals and two control plasma samples incubated with VSV-SARS2-S were used to infect the indicated cells, and the luciferase activity in the cell lysates was determined at 24 hpi. The experiments were performed in duplicate; means and SD are shown. Statistical analysis was performed using an unpaired t test. ***, P < 0.001; **, P < 0.01; *, P < 0.05.

However, in FcyR BHK cells transfected with ACE2, luciferase levels were significantly higher when infected with VSV-SARS2-S incubated with increasingly diluted plasma, indicating that the FcyR enhanced VSV-SARS2-S infection. Fortunately, this was only seen with FcyRIIA, and not the other two receptors. To further investigate the possibility of ADE in SARS-CoV-2 infection, the researchers explored the possibility that an association with the FcRy subunit was required for the function of FcyRIA and FcyRIIIA. They engineered the BHK cells expressing those receptors once again, this time in order to allow them to express FCERIG (the subunit involved) stably. There was a significant increase in luciferase signals for FcyRIIIA-FCER1G BHK cells – suggesting that the FCERIG was necessary for activation. As no ADE of infection was detected in hACE2-BHK cells, these data suggest that ADE can aid SARS-CoV-2 infection in humans. Upon expanding the testing to include convalescent-phase plasma obtained 1, 3, and 6 months post-diagnosis – all showed positive results. These tests were repeated with primary human macrophages, but no SARS-CoV-2 replication was found.

The researchers propose that their results prove that SARS-CoV-2 infection induces antibodies that can cause ADE-induced infection, and that these antibodies persist for six months post-infection at a minimum.

The authors highlight the importance of their study given the emergence of multiple variants of concern, especially as the risk of reinfection could trigger a worse prognosis. This is because the variants antigenicity is different from the original strain found in Wuhan, China.

So while an infected individual will still have a robust immune reaction, it will be less effective against the new strain – while also paving the way for ADE-induced infection. The authors' findings are backed up by several studies, including similar results for SARS-CoV-2 replication in macrophages and a finding of a correlation between ADE-inducing antibodies and COVID-19 severity. These results could not only help inform treatment and drug development for this pandemic and future coronavirus diseases but could also be beneficial to governments attempting to devise public health policy. Unfortunately, the worrisome variants of concern appear even more dangerous with this new information.

Journal reference:
Sam Hancock

Written by

Sam Hancock

Sam completed his MSci in Genetics at the University of Nottingham in 2019, fuelled initially by an interest in genetic ageing. As part of his degree, he also investigated the role of rnh genes in originless replication in archaea.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Hancock, Sam. (2021, September 30). SARS-CoV-2 infection aided by antibody-dependent enhancement. News-Medical. Retrieved on November 30, 2021 from https://www.news-medical.net/news/20210930/SARS-CoV-2-infection-aided-by-antibody-dependent-enhancement.aspx.

  • MLA

    Hancock, Sam. "SARS-CoV-2 infection aided by antibody-dependent enhancement". News-Medical. 30 November 2021. <https://www.news-medical.net/news/20210930/SARS-CoV-2-infection-aided-by-antibody-dependent-enhancement.aspx>.

  • Chicago

    Hancock, Sam. "SARS-CoV-2 infection aided by antibody-dependent enhancement". News-Medical. https://www.news-medical.net/news/20210930/SARS-CoV-2-infection-aided-by-antibody-dependent-enhancement.aspx. (accessed November 30, 2021).

  • Harvard

    Hancock, Sam. 2021. SARS-CoV-2 infection aided by antibody-dependent enhancement. News-Medical, viewed 30 November 2021, https://www.news-medical.net/news/20210930/SARS-CoV-2-infection-aided-by-antibody-dependent-enhancement.aspx.

Comments

  1. Alex Fake Alex Fake Canada says:

    Hi is there anyone who truly understands this information out there able to make it understandable to a layperson.

    • Nate Klingenstein Nate Klingenstein United States says:

      Antibodies can be infection-enhancing, non-neutralizing, or neutralizing.  This article describes one of the ways in which antibodies are infection-enhancing in SARS-CoV-2; it basically rides them into other immune cells to infect them and totally wreak havoc on the immune system once it does.  When infection-enhancing antibodies overwhelm neutralizing antibodies, clinical ADE occurs.

      Delta has already evolved complete resistance to neutralizing antibodies from vaccines targeting the NTD, one of two major targets for antibodies in SARS-CoV-2.  It has even evolved to enhance the activity of the infection-enhancing antibodies.

      Basically, the virus can abuse antibodies for its own benefit in multiple ways, not just dodge them.  Delta's doing that right now and here's (part of) how.

      • 192.168.0.13 192.168.0.13 Canada says:

        So does this mean that a previous immune response will allow the variants to infect for easily? If this is the case, how does the vaccine immune response compare to a natural infection immune response?

        • Anon Anon Anon Anon United States says:

          In short, yes; that is certainly a possibility.

          There are studies that can be searched that show Clinical ADE in animals when they tried to mRNA vaccinate them against viruses like SARS-CoV-2. Many of those studies showed high mortality rates of up to 85% or more.

          With the mRNA therapy, they send mRNA into your cells to program them to produce a certain antibody or a protein that will elicit your body to make an antibody against.

          With natural immunity, your body will produce many antibodies for different aspects of the virus including the different proteins on the surface of the envelope and the features of the capsid, and it will do it in a natural way that will reduce the risk of ADE.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
You might also like... ×
Scientists discover several factors influencing waning immunity with the Pfizer COVID Vaccine