In his introduction, Oluf Andersen presented a historical exposé on changing ideas on the involvement of infections in MS pathogenesis, with emphasis on the search for viable hypotheses.

Arno Hänninen reviewed the relationship between the innate system and infections through the eyes of an immunologist.

The hygiene hypothesis, suggesting that low exposure to pathogens early in life can increase the risk for immune-mediated diseases, may explain the increased incidence of allergy and autoimmune diseases in industrialized countries. As Marte Wendel-Haga could not attend the symposium due to illness, Elisabeth Celius gave the presentation.

JCV infects up to about 90 % of the normal adult population, establishing life-long persistent infections but only causing disease in immunocompromised individuals. Jean-Luc Murk described the virus and how it interacts with humans from a clinical microbiologist’s viewpoint.

Herpes viruses have been implicated as one of the causal factors in MS onset but its role in disease progression is still uncertain. Tomas Bergström reviewed the current knowledge.

Human endogenous retroviruses are retroviral elements in the genome that were originally derived from exogenous retroviruses, which they closely resemble. Tove Christensen reviewed how they are associated with MS and may be involved in MS pathogenesis.

Eero Rissanen reviewed microglial pathophysiology and explained how MR and PET imaging can evaluate microglial activation.

Henrik Zetterberg reviewed fluid biomarkers for microglial activation and neuronal injury that may find use for investigating the relationship between infections and CNS diseases, focussing on astroglial markers and neurofilament light. He also presented a new assay for measuring neurofilament light in blood.

Recent clinical and experimental studies indicate that MS develops as a consequence of failed interplay between genetic (‘nature’) and environmental (‘nurture’) factors. Hartmut Wekerle argued that MS is most probably an autoimmune disease that is kindled in the gut, before discussing nurture-centred ways to modulate the disease in experimental animal models.

Annette Bang Oturai outlined the possibilities of modifying gut microbiota composition.