COVID-19 and
Your Immune System

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COVID-19 is caused by the SARS-COV-2 virus.​

A viral infection like COVID-19 occurs when a virus uses your body’s cellular machinery to make lots of copies of itself. Those viral copies then spread to other cells, and if enough cells are infected you can experience symptoms like fever, headache, and loss of taste or smell. And if the infection spreads too far too fast, it can kill you.

A virus is made up of a number of different proteins, each of which plays a role in its function. For instance, some proteins bundle up the RNA that is the “formula” for making copies of the virus, others create the outer shell that protects the virus from its environment. One specialized protein – the spike or “S” protein – is expressed on the surface of the virus and is used to “dock” with human cells, the first step in the infection process. The spike protein is a critical part of the COVID-19 story, and the focus of a new class of vaccines, the mRNA vaccines from Pfizer and Moderna.

Antibodies are specialized proteins produced by your immune system to fight off viral infections.​

When a cell is infected, or when a virus is recognized by the immune system, signals are sent to your lymphatic system to begin the search for an antibody that can bind to the virus. Antibodies are highly specialized proteins that bind very specifically to invading antigens, whether those invaders are viruses, bacteria, fungi, toxins, or other chemicals.

Infections are a “war” between the attacking pathogen and your body’s immune system. Like any good army, your immune system has many weapons at its disposal. The frontline defenses of the innate immune system can slow or even stop the virus before the infection begins, and T-cells are like guided weapons, able to both identify and destroy the attacking pathogens. Antibodies, which are produced by B-cells, are not responsible for killing pathogens but rather neutralize them by attaching to key locations that prevent viral entry to the cell, or mark them for destruction by white blood cells that are always looking for invaders to kill.

Immunoglobulin G (IgG) is a type of antibody.​

There are several varieties of antibodies, also known as immunoglobulins or Igs. The three key types of antibodies active in the fight against viral infection are IgA, IgM, and IgG. IgA are largely deployed in mucosal tissues like the lungs or intestines. IgM is a “rapid response” antibody – early to respond to an invading pathogen, IgM helps your body slow down the progress of the infection as your immune system tries to develop a more specialized and specific antibody through a process of trial-and-error. While IgM levels rise early in an infection, their concentration tends to drop as other more specific antibodies like IgG are produced.

Immunoglobulin G, or IgG, are antibodies that circulate through the blood and are selected for their ability to identify a pathogen with great specificity. Having an antibody that binds to the pathogen and only the pathogen is critical to prevent the immune system from destroying healthy tissue. IgG is produced by B-cells in your body’s germinal centers (lymph nodes, spleen, tonsils, etc.), and some of those B-cells are retained for a rapid response should you be exposed to the pathogen again. These retained cells are called memory B-cells and are part of your immune memory.

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Measuring IgG concentration is a way to monitor your immune system's status.​

Your immune system is the most important asset you have for fighting off an infectious disease. Even strategies such as vaccination, antiviral drugs, and monoclonal antibodies are designed to either buy time for, enhance, or “prime” your body’s own immune response. Most viral infections are ultimately beaten back by your own immune system. And each time it emerges triumphant, your immune system can “remember” the way it achieved victory, increasing the odds of prevailing against future invaders. When your immune system becomes sufficiently activated and engaged to generated IgG antibodies, you are referred to as having “seroconverted.”

However, because everyone’s biological makeup and history of infection is different, it is impossible to know how your immune system will respond to an infection, vaccination, or therapeutic without testing. IgG concentration in your blood is one indicator of how your body has responded, and can be used therefore to guide decisions about future actions, such as whether and when to get vaccinated, whether to avoid high-risk situations because you failed to seroconvert, or whether you had an asymptomatic infection in the past.

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IgG concentration could inform many clinical decisions if a quantitative test was readily available.

Traditional rapid antibody tests use a technology called LFA, or lateral flow assays. While these tests can give you some information in certain situations, in general they are of low utility because they are a “qualitative” tests – that is, they give you a “Positive” or “Negative” readout.

But making decisions like whether or when to get a booster shot requires a level of accuracy and precision that is not feasible with a qualitative test like LFA. And while there are traditional lab tests that can provide a semi-quantitative readout of IgG, these tests require a venipuncture and take days to report results. Finally, even those lab tests were not able to report standardized units because an international standard was only recently developed by the World Health Organization for COVID-19 antibodies.

We believe one reason that people have not actively managed their immune status is because there has not been a fast, easy, accurate, quantitative test that can give them the information they need. Brevitest’s Quantimmune™ System addresses that need, making is possible for your important decisions to be informed decisions.