What is multiple sclerosis (MS)?

Multiple sclerosis is an autoimmune disease chronically affecting the central nervous system (CNS), which is the brain and the spinal cord. In MS, there is damage done due to inflammation where the immune system mistakenly attacks the myelin sheath which protects the nerve fibres around the neurons thereby leading to scar formation. The impact of MS varies among individuals and these include fatigue, difficulty walking, weakness leading to numbness, tremors, blurred and double vision, emotional changes and spasms.¹

What is adenovirus?

Adenoviruses are a frequent type of virus that can infect your nervous system, intestines, the lining of your eyes, lungs, and urinary tract. These viruses are extremely infectious and can lead to a variety of diseases, ranging from ordinary colds and other minor respiratory infections to more serious ailments like gastroenteritis, pneumonia, and bronchitis.² 

Adenovirus strains are diverse, with over 90 serotypes and seven species (A to G) identified. Some of the typical strains include:

• Adenovirus serotypes 2 and 5 are often employed as vectors in research, gene therapy, and vaccine production
• Acute respiratory disease (ARD) has been linked to adenovirus serotypes 4 and 7, especially among military recruits and in close quarters
• Gastroenteritis is caused by adenovirus serotypes 40 and 41, particularly in youngsters
• Serotype 14 adenovirus: This strain has been linked to epidemics of severe respiratory illnesses, especially in populated areas like military bases and college campuses

Although they can affect persons of all ages, adenovirus infections are more frequent in newborns and young children. In addition to respiratory droplets and touching infected items or surfaces, close human contact is another way that the virus spreads.

The exact strain and the area of the body afflicted determine the individual symptoms, which frequently include fever, sore throat, coughing, and lung congestion.³ Serious problems such as pneumonia can arise from severe cases of adenovirus infections.

Although adenovirus infections can happen at any time of year, they are most frequent in the late winter, early spring, and early summer. There are several ways that the virus might spread:

• Respiratory droplets: When an infected individual coughs or sneezes, respiratory droplets from their body are released into the air, making the adenovirus very infectious. People in the vicinity may inhale these droplets and become infected
• Close personal contact: Shaking hands or touching surfaces contaminated with the virus are examples of how close personal contact with an infected individual can transmit an adenovirus
• Faecal-oral pathway: The faecal-oral(from the anus to the mouth) route is one way that certain adenovirus strains, especially serotypes 40 and 41, can spread. This method frequently causes gastroenteritis outbreaks in nursery schools, schools and other crowded settings

Adenoviruses frequently cause the following infections:

• Adenovirus is responsible for several respiratory diseases, including bronchitis, pneumonia, croup, pharyngitis, and the common cold
• Pink eye, also known as conjunctivitis, is a condition when the lining of the eyes becomes infected by an adenovirus. Pink eye symptoms include redness, irritation, tears, and discharge from the eyes
• Gastroenteritis: Symptoms of gastroenteritis include vomiting, diarrhoea, fever, and stomach discomfort. Serotypes 40 and 41 of the adenovirus are particularly known to cause this condition
• Urinary tract infections: Urinary tract infections caused by adenoviruses can cause symptoms including urgency, frequency, and discomfort when urinating as well as hematuria, or blood in the urine

The hypothesised link between adenovirus and multiple sclerosis

Studies have indicated a possible connection between the onset of multiple sclerosis (MS) and adenovirus infection. While the precise cause of multiple sclerosis (MS) is still unclear, a mixture of genetic and environmental factors, including viral infections, is thought to be responsible ^[4]. Because adenovirus may both create a chronic infection and elicit an immunological response, it has been specifically studied as a possible MS trigger.

The connection between MS and adenovirus infection has been examined in a number of research. Although a clear relationship has not been demonstrated, several studies have discovered data that may be a pointer:

Human studies

• Detection of antibodies: Compared to healthy persons, MS patients' blood and cerebrospinal fluid were shown to contain greater levels of antibodies against adenovirus in several investigations. This implies that exposure to adenovirus may be more prevalent in MS patients
• DNA analysis: In the brains of MS patients, adenovirus DNA has been found, especially in regions with active demyelination (damage to the protective myelin coating surrounding nerve fibres)

Research on animals

• It has been demonstrated that an adenovirus infection can cause demyelination and an autoimmune reaction akin to multiple sclerosis

It's unclear exactly how an adenovirus infection might cause multiple sclerosis. Nonetheless, a number of theories have been put forth:

• Molecular mimicry: Adenoviruses have the potential to mimic some self-proteins. This activated the white blood cells in the host thereby setting off an immunological response. This - interacts with the myelin proteins and causes autoimmune myelin degradation in those who are vulnerable
• Epitope spreading: An immune response directed against myelin proteins by an adenovirus infection may reveal more myelin epitopes, aside the original epitope and broaden the autoimmune response
• Pro-inflammatory cytokine production can be induced by an adenovirus infection, which may be a factor in the inflammation and demyelination observed in multiple sclerosis

Even if there is evidence pointing to a possible relationship between adenovirus infection and the disease, additional study is required to completely understand the role of adenovirus in the onset and progression of MS.

Current state of understanding

Although there is evidence linking adenovirus infection to multiple sclerosis, the precise nature of this relationship is still unclear. Adenovirus infection in MS patients has been detected in certain studies but not in others. Furthermore, it's uncertain if an adenovirus infection causes MS directly or if it only makes those who are prone to the condition experience the start of the illness.

Research is now being conducted on the relationship between adenovirus and multiple sclerosis, since opinions in the scientific community remain divided on the matter. Some specialists believe that an adenovirus infection is one of the environmental factors that lead to the development of multiple sclerosis (MS), while others believe that it triggers the autoimmune reaction that leads to the condition.⁵

Further research is required to fully understand the relationship between adenovirus and multiple sclerosis (MS) and the underlying mechanisms via which viral infections may play a role in the development of autoimmune diseases like MS. Additionally, studies on the potential use of antiviral medications and vaccines to treat or prevent MS are also ongoing.

Summary

In summary, there is evidence pointing to a possible connection between adenovirus infection and multiple sclerosis (MS), however, it is still unclear exactly what this connection entails. The scientific community is split on the issue since some research has shown evidence of adenovirus infection in MS patients while others have not.

To ascertain whether an adenovirus infection causes multiple sclerosis directly or if it just sets off the autoimmune reaction that results in the illness, more research is required.

Furthermore, investigations on the possible use of vaccines and antiviral drugs to treat or prevent MS are still underway.