Downregulation of hypocretin/orexin after H1N1 Pandemrix vaccination of adolescent mice.

Narcolepsy type 1 (NT1), characterized by the loss of hypocretin/orexin (HCRT) production in the lateral hypothalamus, has been linked to Pandemrix vaccination during the 2009 H1N1 pandemic, especially in children and adolescents. It is still unknown why this vaccination increased the risk of developing NT1. This study investigated the effects of Pandemrix vaccination during adolescence on Hcrt mRNA expression in mice. Mice received a primary vaccination (50 µL i.m.) during prepubescence and a booster vaccination during peri-adolescence. Hcrt expression was measured at three-time points after the vaccinations. Control groups included both a saline group and an undisturbed group of mice. Hcrt expression was decreased after both Pandemrix and saline injections, but 21 days after the second injection, the saline group no longer showed decreased Hcrt expression, while the Pandemrix group still exhibited a significant reduction of about 60% compared to the undisturbed control group. This finding suggests that Pandemrix vaccination during adolescence influences Hcrt expression in mice into early adulthood. The Hcrt mRNA level did not reach the low levels known to induce NT1 symptoms, instead, our finding supports the multiple-hit hypothesis of NT1 that states that several insults to the HCRT system may be needed to induce NT1 and that Pandemrix could be one such insult.

The glycosylation defect in solute carrier SLC35A2/SLC35A3 double knockout cells is rescued by SLC35A2-SLC35A3 and SLC35A3-SLC35A2 hybrids.

SLC35A2 and SLC35A3 are homologous proteins with postulated nucleotide sugar transporting activities. Unlike SLC35A2, whose specificity for UDP-Gal is well-established, the UDP-GlcNAc transporting activity initially attributed to SLC35A3 has recently been put into question. In this study, we constructed two hybrid proteins (SLC35A2-SLC35A3 and SLC35A3-SLC35A2) and expressed them in a previously generated SLC35A2/SLC35A3 double knockout HEK293T cell line. Our idea was to force equivalent stoichiometry of the two proteins in the cells in order to reproduce the behavior of the SLC35A2/SLC35A3 complexes in the Golgi membrane. The hybrid proteins were able to fully restore glycosylation in the double knockout. In contrast, the expression of SLC35A3 alone in these cells improved galactosylation only to a limited extent. Our study shows that the proper glycosylation requires a balanced cooperation between SLC35A2 and SLC35A3.