The Interaction of Antibodies and Viruses

Canonical biological functions of antibodies. Fig.1 Canonical biological functions of antibodies. (Dimitrov, 2020)

Immunity to viral infection is caused by a variety of specific and nonspecific mechanisms. When the immune system recognizes a pathogen, one of its most important responses is releasing something called antibodies. Virus and/or virus-infected cells can stimulate B lymphocytes to produce antibodies (specific for viral antigens) that fight off invaders and keep us healthy. Everyone has more than 10 billion different kinds of antibodies.

Antibodies Response Against Viruses

Antibodies serve as critical barriers to viral infection. At the tips of antibodies are the unique sites where they bind with a matching site on antigens and destroy them. After binding to antigens on the pathogen, antibodies can diminish viral dissemination by direct action involving both their antigen-binding activity and the effector functions borne by their Fc fragment. Antibodies are efficiently recognized by both the complement and the Fcγ receptors (FcγRs) borne by many cells of the immune system.

Antibody-Dependent Enhancement

Antibody-dependent enhancement (ADE) of infection represents a paradoxical phenomenon in host-pathogen biology, in which, antibody, an important pillar of the host defense against invading pathogen, actually allows entry of the pathogen into host territory. Suboptimal neutralizing or non-neutralizing cross-reactive antibodies bind to viruses and facilitate FcγRs or complement receptor-mediated enhanced entry into host cells, followed by its replication, and thus increasing the cellular viral load. ADE is a major obstacle in vaccine development.

Mechanisms of ADE of viral infections. Fig.2 Mechanisms of ADE of viral infections. (Smatti, 2018)

How Antibodies Fight Viruses

The role of antibodies in preventing virus infection and reinfection is unquestionable. Antibodies have several mechanisms to prevent infections. They can either neutralize viruses directly to prohibit their entry into the host cell, or they can crowd around a virus to increase its visibility to other immune cells. Once bound to a virus, antibodies can also tag the virus for phagocytes, which in turn ingest and destroy the pathogen. Antibodies fight viruses in different ways as follows:

  • Neutralization. Viruses have proteins on their surface which they need to enter the host cell in order to replicate and spread. Antibodies can bind to viruses making them harmless.
  • Agglutination. Sometimes the many antibodies can bind to the same free antigen to cross-link them. Agglutinated viruses make an easier target for immune cells than single viral particles. Agglutination of virions can then be destroyed by effector cells.
  • Cell toxicity. The antibody binds to the antigen on an intruder or an abnormal/infected cell. This acts as a flag for other immune cells that can produce chemicals that kill the unwanted target cell.
  • Activation of phagocytes. A virus-bound antibody binds to FcγR on the surface of phagocytic cells and triggers a mechanism known as phagocytosis, by which the cell engulfs and destroys the virus.
  • Activation of complement. Antibodies can also activate the complement system, which opsonizes and promotes the phagocytosis of viruses. Complement can also damage the envelope (phospholipid bilayer) that is present on some types of viruses.

The antiviral activities of antibodies. Fig.3 The antiviral activities of antibodies. (Burton, 2001)

Creative Biolabs has extensive expertise in the development of antibodies. All our ViroAntibody products listed in one place for easy searching and find the correct product faster and easier. There are both monoclonal and polyclonal antibodies, primary antibodies and secondary antibodies, labeled antibodies and unlabeled antibodies. If you have any questions, please don’t hesitate to contact us.

References

  1. Dimitrov, J.D.; Lacroix-Desmazes, S. Noncanonical functions of antibodies. Trends in immunology. 2020, 41(5): 379-393.
  2. Smatti, M.K.; et al. Viral-induced enhanced disease illness. Frontiers in microbiology. 2018, 9: 2991.
  3. Burton, D.R. Antibodies, viruses and vaccines. Nature Reviews Immunology. 2002, 2 (9): 706-713.
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