HIV and lower risk of multiple sclerosis: beginning to unravel a mystery

[natasa778]

http://jnnp.bmj.com/content/early/2014/07/16/jnnp-2014-307932.full

Objectives Even though multiple sclerosis (MS) and HIV infection are well-documented conditions in clinical medicine, there is only a single case report of a patient with MS and HIV treated with HIV antiretroviral therapies. In this report, the patient's MS symptoms resolved completely after starting combination antiretroviral therapy and remain subsided for more than 12 years. Authors hypothesised that because the pathogenesis of MS has been linked to human endogenous retroviruses, antiretroviral therapy for HIV may be coincidentally treating or preventing progression of MS. This led researchers from Denmark to conduct an epidemiological study on the incidence of MS in a newly diagnosed HIV population (5018 HIV cases compared with 50 149 controls followed for 31 875 and 393 871 person-years, respectively). The incidence rate ratio for an HIV patient acquiring MS was low at 0.3 (95% CI 0.04 to 2.20) but did not reach statistical significance possibly due to the relatively small numbers in both groups. Our study was designed to further investigate the possible association between HIV and MS.

Methods We conducted a comparative cohort study accessing one of the world’s largest linked medical data sets with a cohort of 21 207 HIV-positive patients and 5 298 496 controls stratified by age, sex, year of first hospital admission, region of residence and socioeconomic status and ‘followed up’ by record linkage.

Results Overall, the rate ratio of developing MS in people with HIV, relative to those without HIV, was 0.38 (95% CI 0.15 to 0.79).

Conclusions HIV infection is associated with a significantly decreased risk of developing MS. Mechanisms of this observed possibly protective association may include immunosuppression induced by chronic HIV infection and antiretroviral medications.

This report is the largest record linkage study undertaken to investigate a possible association between HIV and MS. Our investigation revealed that having HIV, and presumptively being on HAART, provided a significant and potentially protective effect in relation to the risk of development of MS. The magnitude of this effect (>60%) is at the highest level of any prognostic risk factor investigated to date. Nonetheless, there are inevitable methodological uncertainties in our study design and our findings should be regarded as speculative rather than definitive. We have had to make reasonable assumptions about the likelihood of our exposed HIV cohort being treated with cART during the period of observation. Further consideration may also be warranted on conducting other proof-of-concept studies on using antiretroviral drugs in patients with different types of MS. The first clinical study with Raltegravir in patients with relapsing remitting MS is already recruiting in the UK.20 Further investigation of our finding has the potential, after more than 170 years since MS was first described by Jean-Martin Charcot, to help reveal the aetiology of MS.