Individuals who appear to have Long COVID may exhibit a variety of symptoms lasting weeks or even years. The latest estimates are that about 10-20% of people infected with SARS-CoV-2 virus will also experience the effects of long COVID. It can be severe. Symptoms include brain fog, fatigue, and intense pain possibly lasting a minimum of three months once the individual has been infected. Although at this point the disorder affects approximately 65 million individuals globally, very little is known about the disease and no treatments are available.
About the Symptoms
The symptoms may mimic those of other illnesses following a pattern of emerging, resolving, and reemerging. Long COVID patients tend to have a wide variety of symptoms ranging from mild to extremely severe.
During the studies, antibodies were isolated from long COVID individuals and transferred to mice causing increased pain and reduced movement in those animals. This was a signal to the researchers that antibodies may be responsible for some of long COVID’s symptoms.
Admittedly, it is still unclear how this occurs. Results must be replicated in much larger studies. However, immunologist Resia Pretorius at South Africa’s Stellenbosch University suggested that this paper provides further understanding of long COVID.
About Autoantibodies
• One area under consideration when delving into long COVID would be autoantibodies. They are a type of protein. These rogue antibodies have been identified through previous research as potentially being responsible for the disease. Rogue antibodies are initially created by a person then proceed to go on the attack against his or her own tissues or immune system.
• Other considerations are that long COVID is the result of SARS-CoV-2’s persistence in the body.
• Small blood clots are a concern as they limit the exchange of oxygen in a person’s body
• And lastly the list includes the autoantibody hypothesis.
About the Research
The team worked with IgG antibodies taken from 34 individuals averaging 43 years of age. The antibodies were the type most commonly found in human fluids. The participants had developed mild cases of SARS-CoV-2 within two years after the start of the pandemic. The next step was to separate the participants according to concentrations of inflammatory proteins found in the individual’s blood and inject each mouse from one of the pools. The effects on motor activity and pain perception were observed.
Noticeable differences were found between mice who had long COVID versus those who had recovered. When the first group of mice were pricked on the paw, they reacted with strong sensitivity. Whereas when the second group of mice who had recovered from COVID-19 were pricked, they were not as sensitive. Also of interest was the researchers’ discovery that motor function was not affected in either group.
A Wider Range of Symptoms
Antibodies taken from people in a third group who had long COVID were tested. In this segment researchers observed that mice walking for 30 minutes covered only 60% of the same distance covered by the controls. However, the level of sensitivity to pain remained the same for both groups of mice.
The inference is that antibodies found in people who had long COVID may cause symptoms by attacking healthy tissue.
IgG Antibodies and Pain Sensitivity
Last month a webinar presented by the non-profit Solve M.E. of Glendale, CA, discussed a small study whereby researchers injected IgG antibodies into mice that were taken from participants who had long COVID. The result was an increase in pain sensitivity. Again, an opposite response was observed from mice injected with antibodies from healthy people.
This brought about suggestions that people with long COVID be excluded from making blood donations. On the contrary, the study might also suggest that it may have presented a new model with which to study animals with long COVID.
In conclusion, an Imperial College immunologist, Danny Altmann, tends to be skeptical. He suggests that long COVID is hard to replicate in animal models. Altmann said that it is not clear how well symptoms that appear in mice reflect similarities in humans and points out that there is little interest in building these models. However, he is hopeful that these small studies will help.
