What is Multiple Sclerosis (MS)?

Multiple sclerosis (MS) is an autoimmune disease chronically affecting the central nervous system (CNS), which is the brain and the spinal cord. In MS, damage is done due to inflammation, where the immune system mistakenly attacks the myelin sheath, which protects the nerve fibres around the nerve cells, leading to scar formation. The impacts of MS vary among individuals, as a result, various symptoms, such as fatigue, difficulty walking, weakness leading to numbness, tremors, blurred and double vision, emotional changes, and spasms, can occur.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 including gastroenteritis, pneumonia, and bronchitis.² 

Adenovirus strains are diverse, with over 90 serotypes and seven species (A to G) to be identified. Several of the typical strains consist of:³

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

Adenovirus infections can happen at any time of the year, but they are most frequent in the late winter, early spring, and early summer. There are several ways that the virus might spread:³

• 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 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:³

• Adenovirus is responsible for many 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, which is blood in the urine.

The hypothesised link between adenovirus and Multiple Sclerosis

Different studies have indicated a possible connection between the onset of multiple sclerosis (MS) and diverse virus infections. While the precise aetiology of MS is still unclear, a confluence of genetic and environmental factors, including viral infections, is thought to be responsible.⁴ Because adenovirus may create a chronic infection, and elicit an immunological response, it has been specifically studied as a possible MS trigger.⁵

The connection between MS and viral infections has been examined in f literature research. However, a clear causal relationship has not been demonstrated.⁴ 

• Epidemiological research: Compared to healthy persons, MS patients' blood and cerebrospinal fluid were shown to contain higher levels of antibodies against adenovirus. This implies that viral exposure may be more prevalent in MS patients⁵
• Identification of viruses: 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)^4,5

It's unclear exactly how an adenovirus infection might cause MS. Nonetheless, some theories have been put forth:^4,5

• Molecular mimicry: Adenoviruses have the potential to set off an immunological response that causes autoimmune myelin degradation, in those who are vulnerable.
• Epitope spreading: An immune response directed against myelin proteins by an adenovirus infection that can cause an autoimmune response.
• The production of pro-inflammatory cytokines can be induced by an adenovirus infection, which may be a factor in the inflammation and demyelination observed in MS.

Overall, additional studies are required to completely understand the role of adenovirus, as well as other viruses in the onset and course of MS.

The current state of understanding

Although there is evidence linking adenovirus infection to MS, the precise nature of this relationship is still unclear. Adenovirus infection in MS patients has been detected in some 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.^4,5

Research is now being conducted on the relationship between different viruses, such as adenovirus, and MS 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 MS, while others believe that it triggers the autoimmune reaction that leads to the condition.^4,6 

Further research is required to fully understand 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.^4,6

Summary

In summary, there is evidence pointing to a possible connection between adenovirus infection and 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.

Furthermore, investigations on the possible use of vaccines and antiviral drugs to treat or prevent MS are still underway. All things considered, further study is required to completely comprehend the association between adenovirus and MS and its implications for both prevention and therapy.