A team of scientists has made an important discovery that helps explain why some people suffer long-lasting joint pain after being infected with a mosquito-borne virus called chikungunya.
Chikungunya virus, often shortened to CHIKV, is spread by mosquitoes and affects people in more than 110 countries. Most people who get infected experience symptoms similar to the flu. These can include fever, tiredness, rash, and joint pain. For many, these symptoms improve within a few weeks.
However, for some people, the joint pain does not go away. Instead, it can last for months or even years, becoming a chronic condition that affects daily life. Until now, scientists have not fully understood why this happens.
Researchers at the La Jolla Institute for Immunology in the United States set out to investigate this mystery. Their study, published in the scientific journal Cell Reports Medicine, focused on how the body’s immune system responds to the virus.
The immune system is designed to protect us from infections. It uses different types of cells to recognize and destroy viruses and bacteria. One important group of cells is called T cells. These cells help the body remember past infections and respond more quickly if the same virus appears again.
There are different types of T cells, including CD4+ T cells and CD8+ T cells. CD8+ T cells usually play a direct role in killing infected cells, while CD4+ T cells help guide and support the immune response.
In this study, the researchers examined blood samples from people in Colombia who had previously been infected with chikungunya. They wanted to see how their immune cells reacted to small pieces of the virus.
What they found was surprising. The CD4+ T cells showed a very strong and long-lasting response to the virus. Even six years after infection, 87 percent of the patients still had these virus-specific CD4+ T cells in their blood. In comparison, only 13 percent had CD8+ T cells related to the virus.
This pattern is unusual for viral infections. Normally, CD8+ T cells play a bigger role in fighting viruses. However, the pattern seen in this study is more similar to what scientists observe in autoimmune diseases, such as rheumatoid arthritis.
Autoimmune diseases happen when the immune system mistakenly attacks the body’s own tissues. In rheumatoid arthritis, this leads to ongoing inflammation and joint damage.
The researchers believe that something similar may be happening in people with long-term chikungunya symptoms. The CD4+ T cells may continue to stay active even after the virus is gone, causing ongoing inflammation in the joints.
The study also found that these CD4+ T cells often produced a specific inflammatory substance called TNF-alpha. This substance helps the body fight infections, but when it remains active for too long, it can cause damage.
In patients with chronic joint pain, the T cells were mostly producing only TNF-alpha instead of a mix of different signals. This type of response is called “monofunctional,” and it is often linked to long-term inflammation.
This finding may help explain why the pain continues long after the infection has cleared. It also suggests a possible way to treat the condition. Medicines that block TNF-alpha are already used to treat autoimmune diseases like rheumatoid arthritis. These treatments might also help people suffering from long-term joint pain after chikungunya infection.
The researchers are now exploring why certain groups of people are more affected than others. Early findings suggest that women in their 40s may be more likely to develop chronic symptoms. Scientists are studying whether the immune system in these individuals may be more likely to attack the body’s own tissues.
This research is part of a larger effort to understand how viral infections can lead to long-term health problems. Other viruses, including dengue and the virus that causes COVID-19, have also been linked to lasting symptoms in some people.
Scientists are increasingly recognizing that infections do not always end when the virus disappears. In some cases, the immune system may continue to react in ways that cause ongoing illness.
Although more research is needed, this study is an important step forward. It helps explain why some people experience long-term joint pain after chikungunya and points to possible treatments that could improve their quality of life.
The study was published in Cell Reports Medicine and highlights the growing understanding of how the immune system can sometimes contribute to disease instead of protecting against it.
If you care about arthritis, please read studies about extra virgin olive oil for arthritis, and pomegranate: A natural treatment for rheumatoid arthritis.
For more information about arthritis, please see recent studies about how to live pain-free with arthritis, and results showing medical cannabis may help reduce arthritis pain, back pain.
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