StemCell Therapy

A great deal of discussion is taking place regarding antibody testing for the COVID-19 coronavirus. A basic discussion of immunology is helpful to understand the value of such testing.

What are antibodies? How do we develop antibodies? How do antibodies work? What is an antibody test? What are the clinical and public health benefits of antibody testing?

Antibodies are specialized humoral proteins made by the immune system. They help the body fight against infections and disease by "recognizing" viruses, bacteria and infected cells. Each antibody binds to a specific antigen associated with a danger signal in the body. This antigen is also known as the antibody's target. When a foreign protein like a virus enters the body, the immune system responds to this antigen. Specific proteins are developed to fight off and hopefully neutralize or kill the invader. This is technically called humoral immunity.

There are three ways to obtain immunity to various disease agents. Each of these will play a role as an antibody test for the COVID-19 coronavirus becomes widely used.

First is natural active immunity. This immunity is derived by naturally becoming infected by a pathogen, such as a virus or a bacteria. When infection occurs, humoral immunity kicks in, developing antibodies specific to this disease. When the body is exposed to this same pathogen (antigen) in the future, the immune system releases those specific antibodies to attack the pathogen before infection can take place. An example is a person developing a case of measles from exposure to the virus in the natural environment. This type of immunity is usually long-lasting. Unfortunately, not every infection with a pathogen results in developing antibodies that are protective or "neutralizing." For example, infection with the bacteria that causes Lyme Disease does not result in the development of protective antibodies, thus we can become reinfected with this bacteria upon repeated exposure.

Second is artificial active immunity. This type of immunity is developed by artificially exposing a person to a pathogen and causing the immune system to actively develop antibodies against this specific pathogen. This is accomplished through the process of immunization or vaccination. A vaccine, which is either a killed or very weakened version of the pathogen is introduced into a person, via injection, orally, nasal mist etc. When the vaccine (antigen) enters the body, the immune system actively begins to develop protective neutralizing antibodies against this specific pathogen (antigen). Normally, immunity begins about two weeks after immunization. With immunization, it may take multiple doses of the vaccine over time to develop a sufficient level of antibodies to confer full immunity. This type of immunity may not be long-lasting, requiring booster immunizations in the future. An example is tetanus, where after the initial series if immunizations to develop adequate immunity, this immunity may wane over the years requiring a booster "shot" every 10 years.

Third, and the least used method of providing immunity, is artificial passive immunity. This type of immunity is obtained when a serum collected from individuals who were naturally infected by and recovered from a specific disease and contains the antibodies against that disease, is administered to a non-immune person. The individual receiving this serum does not actively produce their own antibodies, but passively accepts and uses the artificially introduced antibodies from the donors serum to attack the pathogen and prevent infection. An example is the administration of immune globulin to susceptible individuals exposed to Hepatitis A. If given soon after exposure, this immune globulin containing antibodies against Hepatitis A will prevent infection and disease. This type of immunity is shorted-lived, usually providing only a few months of protection.

Each of these three methods of gaining immunity are being and will be utilized in various ways to combat the COVID-19 pandemic once a reliable antibody test is widely available to the medical and public health community. The FDA has recently licensed a number of these tests. The test must reliably be able to detect antibodies to the COVID-19 coronavirus, and that the level of antibodies in the person tested is sufficient to provide immunity. It usually takes about four weeks after infection to develop detectable antibodies to the COVID-19 coronavirus. Since this virus is so new, it is not yet fully understood how long such immunity will remain active, and if it will protect against the virus as it changes. If this virus behaves like similar coronaviruses, it is expected that immunity will develop for some period of time and that it will also be conferred against a changing virus.

The antibody test is already being used to identify individuals whom have developed immunity to COVID-19. This information will allow individuals, especially those in critical occupations such as health care, first responders and public safety to return to work more safely and quickly after infection and recovery. This will be expanded to other occupations as the testing becomes more widely used, to allow greater re-opening of the economy.

The test is also being used to identify individuals with antibodies to the COVID-19 coronavirus who would donate serum to be used to develop an immune globulin as described above. This serum globulin is being administered to critically ill COVID-19 patients to reduce symptoms and prevent death. Once available on a larger scale, more people with COVID-19 coronavirus antibodies will be recruited to donate serum to make larger quantities of this immune globulin that could be administered to susceptible individuals exposed to the virus, such as health care workers treating COVID-19 patients.

This antibody test will be used for public health surveillance and to determine how widely the COVID-19 epidemic has spread throughout the nation. Studies called sero prevalence studies will be conducted by testing large numbers of blood samples taken from people across the nation to better understand how much immunity to this virus exists. Blood will be tested from samples taken at blood donation centers, other clinical settings, and by recruiting a sufficiently large representative sample of the nation to volunteer. This information will determine which parts of the country have lower rates of immunity and may be more at risk if a second wave of disease strikes. This would provide information that will be used to prepare these at-risk areas before a second wave becomes a reality. This will allow better targeting and stockpiling of needed supplies and equipment in the areas where it may be most needed.

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Lastly, the antibody test will be used to evaluate the effectiveness of any vaccine developed for the Covid-19 coronavirus. As trial vaccines move through the safety and effectiveness stages for final approval, humans will be administered the trial vaccine on a voluntary basis. The antibody test will be used to determine if these trial vaccines develop sufficient protective antibodies to safely prevent infection. The test will also be used to determine how many doses of the vaccine will be required, at what intervals will doses be administered, how long immunity lasts, and if booster "shots" will be required and, if so, how long after initial immunization.

Unfortunately, all these steps will be taking place for at least the next year or two. We must expand diagnostic testing for the virus, conduct contract tracing to identify sources of community transmission, isolate cases and quarantine contacts. Face coverings must be required for everyone working or entering public places of business, and good hand hygiene must be maintained. In the meantime we will need to live with reasonable but necessary limits on our daily lives. The better we manage the crisis now, the better of we will be down the road.

Rich DiPentima of Portsmouth spent more than 30 years as a public health official and epidemiologist, including service as deputy public health director in Manchester and chief of communicable disease epidemiology at the New Hampshire Division of Public Health. His column on coronavirus will appear weekly in Seacoast Health during the coronavirus public health crisis.

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Coronavirus This Week: What is antibody testing and how it may impact the COVID-19 pandemic - Foster's Daily Democrat

This entry was posted on April 24, 2020 at 5:48 pm and is filed under Immune System. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |