Mechanistic insights into influenza vaccine-associated narcolepsy.

We previously reported an increased frequency of antibodies to hypocretin (HCRT) receptor 2 in sera obtained from narcoleptic patients who received the European AS03-adjuvanted vaccine Pandemrix (GlaxoSmithKline Biologicals, s.a.) for the global influenza A H1N1 pandemic in 2009 [A(H1N1)pdm09]. These antibodies cross-reacted with a particular fragment of influenza nucleoprotein (NP) - one of the proteins naturally contained in the virus used to make seasonal influenza vaccine and pandemic influenza vaccines. The purpose of this commentary is to provide additional insights and interpretations of the findings and share additional data not presented in the original paper to help the reader appreciate the key messages of that publication. First, a brief background to narcolepsy and vaccine-induced narcolepsy will be provided. Then, additional insights and clarification will be provided on the following topics: 1) the critical difference identified in the adjuvanted A(H1N1)pdm09 vaccines, 2) the contributing factor likely for the discordant association of narcolepsy between the AS03-adjuvanted pandemic vaccines Pandemrix and Arepanrix (GlaxoSmithKline Biologicals, s.a.), 3) the significance of detecting HCRT receptor 2 (HCRTr2) antibodies in some Finnish control subjects, 4) the approach used for the detection of HCRTr2 antibodies in vaccine-associated narcolepsy, and 5) the plausibility of the proposed mechanism involving HCRTr2 modulation in vaccine-associated narcolepsy.