- Multiple sclerosis (MS) is an autoimmune disease, typically treated by quelling the activity of immune system cells, such as B lymphocytes.
- COVID-19 vaccines work by stimulating the immune system to generate antibodies to the virus responsible for the disease.
- Anti-CD20 drugs help combat the progression of MS by limiting the activity of B cells.
- In 20 people taking anti-CD20 drugs for MS, there was still a robust T cell response to vaccination for COVID-19.
MS is a chronic autoimmune disease that affects the central nervous system’s ability to communicate efficiently. According to the National Multiple Sclerosis Society (NMSS), about one million people in the United States are living with the disease.
Health experts consider MS to be an inflammatory disease. It affects the myelin sheath, a fatty insulating layer surrounding the nerve cells that helps them transmit electrical impulses rapidly.
It is unclear why, but in people with MS, the B cells of their immune system attack the myelin sheath. This gradually erodes nerve impulse transmission. Individuals with this progressive disease experience debilitating symptoms such as numbness, tremor, fatigue, or blurred vision.
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Many people with MS have experienced significant relief from the progression of their disease by using modern drugs called anti-CD20 monoclonal antibodies. Specifically, these drugs target B cells, limiting their ability to attack the myelin sheath to slow or even halt the progression of MS.
Because they work by limiting the activity of the immune system, health experts consider people taking anti-CD20 drugs as immunocompromised.
Does vaccination work when the immune system is compromised?
The immune system is complex, featuring multiple cell types. A recent study in Nature Medicine investigated whether the immune systems of MS patients on anti-CD20 therapy would respond to vaccination with a COVID-19 mRNA vaccine such as Pfizer or Moderna.
Vaccines work by provoking immune system responses among B cells and T cells. Since many people are dependent on anti-B cell therapy to control the progression of their condition, it was unclear if the COVID-19 vaccine would provoke an appropriate immune response among MS patients.
Amit Bar-Or, M.D., a Penn Medicine physician, served as lead investigator. “In this study, we looked at antibody and cellular responses,” said Dr. Bar-Or. “Even among people with decreased [B cell-mediated] antibody levels, we saw robust T cell responses, in some cases even stronger [than among people not on anti-CD20 therapy].”
“In other words, while not an ‘optimal’ response, involving both B cells and T cells, the response is ‘adequate.’”
While the study was small, with just 20 MS patients, an ongoing investigation involving 600 participants will assess the effectiveness of administering additional vaccine doses to MS patients.
Dr. Bar-Or noted that his team’s study was inspired, in part, by emerging research among patients receiving immunotherapy to treat cancer. Despite being immunocompromised, “they’re getting robust T cell responses […] [The COVID-19 vaccine] is indeed protective among these patients,” he said.
Although MS patients made fewer antibodies to the virus compared to people not on immune-suppressing drugs, their T cell responses were markedly robust. This shows that vaccination is likely to provide ample protection against SARS-CoV-2 infection.
According to the NMSS, people on anti-CD20 drug therapy should get vaccinated, as they may expect at least “some immunity.”
While this is good news for cancer patients and clinicians, it is also of academic interest to researchers who study the immune system. “This teaches us about human immune responses,” Dr. Bar-Or noted.
The present study is “already having an impact on guidance for immunocompromised patients,” said Dr. Bar-Or, citing recent changes adopted by the NMSS.
The National Multiple Sclerosis Society weighs in
The study “sheds light on the fundamental mechanisms underlying the development of multiple sclerosis,” said Dr. Bruce Bebo, Executive Vice President, Research, for the NMSS. This kind of research is helping NMSS “focus research investments,” he added.
“We’re getting closer to cures and treatments for MS. We have good treatments for the relapsing or remitting form of MS, but we don’t have them for the hard-to-treat progressive form.”
Part of the reason for that has been a lack of understanding of the fundamental mechanisms driving the more aggressive, progressive form of MS. “The fundamental biology [behind these two forms of MS] is related,” Dr. Bebo said, “but distinct.”
Thanks to the present study and related research, “there’s a tremendous amount of excitement in the research community […] We’re getting closer to cures and treatments for MS.”
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