Could HIV drugs help treat multiple sclerosis?

"Could MS patients be treated with HIV drugs?" ask the Mail Online and The Independent, after a new study discovered people with HIV were almost two-thirds less likely (62%) to develop multiple sclerosis (MS) than those who did not have the virus.

The study was prompted by the case of a patient who had HIV and MS, but stayed clear of any MS symptoms for more than 12 years.

Data from the medical records of about 21,000 people with HIV in the UK was analysed to see how many developed the condition, which affects the brain and spinal cord.

Researchers suggest the HIV infection itself and the antiretroviral drugs used to treat it may protect the body's immune system from developing MS.

Their two theories are:

immunodeficiency caused by HIV may stop the body attacking itself
antiretroviral therapy may suppress other viruses in the body, such as those suggested as being responsible for causing MS

This is a well-conducted study, with a large sample size and very large number of controls. But as it is a cohort study, it can only show an association and cannot prove cause and effect.

The authors acknowledge their findings "should be regarded as speculative rather than definitive".

Overall, this interesting study paves the way for clinical trials to be conducted on the use of antiretroviral medication for people with MS.

Where did the story come from?

The study was carried out by researchers from the Prince of Wales Hospital in Sydney, Australia, and Queen Mary University of London and the University of Oxford in the UK. Funding was not reported.

It was published in the peer-reviewed Journal of Neurology, Neurosurgery and Psychiatry on an open access basis, which means it is free to read online.

In general the media covered the study accurately.

What kind of research was this?

This was a cohort study looking at the proportion of people with HIV compared with the proportion of people without HIV who develop MS.

The researchers aimed to investigate the theory that HIV is associated with a reduced risk of developing MS. As this was a cohort study, it can only show an association and cannot prove cause and effect.

In the autoimmune disorder MS, the body attacks the myelin covering of nerves. This causes symptoms such as loss of vision, muscle stiffness, difficulties with balance and fatigue.

In the majority of cases, these symptoms occur during flare-ups and can last for a few days to a few months and then resolve. Eventually, however, many people develop secondary progressive MS, where the symptoms do not resolve and gradually get worse.

The cause of MS is not known, but research has shown links with human endogenous retroviruses (HERVs). There is no cure at present, but treatments include steroids and other drugs aimed at dampening down the immune response.

A case study was previously published about a patient with MS and HIV whose MS symptoms resolved completely for more than 12 years after starting antiretroviral drugs for HIV.

A Danish cohort study then looked for an association between HIV and a reduced risk of developing MS. Although the incidence of MS was lower in patients with HIV compared with people without HIV, the difference was not statistically significant.

The researchers involved in the current study suggest this was because the number of people in the previous cohort study was too small, so they performed a similar cohort study on a larger sample.

What did the research involve?

Using the English Hospital Episode Statistics (HES) data, all people in England with HIV who had been discharged from an NHS inpatient or outpatient clinic for any reason between 1999 and 2011 were identified. The earliest episode of contact for each patient was used for the analysis.

A control group without HIV was identified from people who required hospital treatment for a minor medical or surgical condition or injury between 1999 and 2011. The earliest episode of contact for the condition or injury was used for the analysis.

Both groups were followed up to see if there was a diagnosis of MS in their medical records.

The researchers excluded anyone from either group who already had a diagnosis of MS or who had a first diagnosis of MS and HIV at the same time. The personal identification of the data was then made anonymous to the study team.

They then analysed the results, accounting for age, sex, region of residence and socioeconomic region.

What were the basic results?

The researchers analysed the data from 21,207 people with HIV and 5,298,496 people without HIV. People involved spanned all age groups from birth to over the age of 85.

The average number of days they followed people in the HIV group was 2,454 days (6.7 years), and 2,756 days (7.6 years) for people in the other group.

The incidence of MS was significantly lower in the HIV group. People with HIV were two-thirds (62%) less likely to develop MS than people without HIV (95% confidence interval 0.15 to 0.79).

Excluding people over the age of 70 made little impact on the result.

How did the researchers interpret the results?

The researchers conclude that, "HIV infection is associated with a significantly decreased risk of developing MS".

They say this might be a result of the "immunosuppression induced by chronic HIV infection and antiretroviral medications", but they acknowledge their findings "should be regarded as speculative rather than definitive".

They also report the first clinical trial using the antiretroviral drug Raltegravir for people with relapsing-remitting MS is currently recruiting participants in the UK.

Conclusion

This large cohort study indicates people with HIV appear to be at a lower risk of developing MS. It is not known what causes this association, but possible reasons put forward by the researchers include:

immunodeficiency caused by HIV may stop the body attacking itself in the autoimmune condition MS
antiretroviral therapy may suppress other viruses in the body, such as those that have been suggested as causing MS

Strengths of the study include the large sample size and the very large number of controls, which would limit any bias by confounding factors.

However, the study did have a few limitations:

Although the overall study period was 12 years, people were recruited to the study at any point during this time, so the follow-up period for some would have been very short.
The development of MS usually occurs between the ages of 20 and 40, but both cohort groups encompassed people of all ages.
Data was lacking on the use of antiretroviral medication, such as the type and length of time of the treatment.
There was limited data on ethnicity and this therefore couldn't fully be adjusted for. However, the researchers report the reduction in risk doesn't seem to be limited to one ethnic group.