Page 38 - The autoimmune hypothesis of narcolepsy and its unexplored clinical features M.S. Schinkelshoek

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Chapter 2
One of the limitations in our study is that we have not been able to distinguish between post-H1N1 NT1 patients and healthy controls who encountered the H1N1 influenza virus and those who did not. We have data on H1N1 exposure and vaccination for only a small subset of all participants included, which can be found in Table 2.1. Given the fact that the H1N1 vaccination coverage in the Netherlands was 30% for the general population and 74% for children (Mereckiene et al., 2012), it is likely that at least a significant percentage of patients with symptom onset after 2009 had encountered the H1N1 virus or were vaccinated against H1N1 during the vaccination campaign. Another factor to consider is the hypothesized post-vaccination risk window, that is defined as a period of two years after the H1N1 vaccination campaign in which the risk of developing NT1 was increased (Sarkanen et al., 2018). Only a small group of participants in the current study were diagnosed in 2010 and 2011, which makes a separate analysis on this group unfeasible. Data on this group is reported in Supplementary table 2.2.
Our findings bridge the findings of studies in sporadic and post-H1N1. In addition to replicating HLA-associations reported in studies focusing on either sporadic NT1 or post-H1N1 NT1 patients, we show that these HLA-DQB1- associations can be found in both groups. Focusing on performing research on the autoimmune hypothesis of NT1 in NT1 patients shortly after symptom onset seems more promising than directing further research to the difference between sporadic and post-H1N1 NT1.
Conclusions
No differences in HLA-associations were found between NT1 patients with symptom onset before and those with symptom onset after the 2009 H1N1 pandemic. The positive association of HLA-DQ7 and negative associations of HLA-DQ2, HLA-DQB1*05:01 and DQB1*06:03 with both pre- and post- H1N1 described in other smaller studies were confirmed in this large Dutch cohort. These results therefore argue against considering sporadic and post- H1N1 NT1 to be separate entities.