Each year, 1000 to 4000 children in the U.S. are born with mitochondrial disease. Because symptoms may present at any age, it is not surprising that a temporal association with vaccination may occur. However, little is known about the clinical and immune response to vaccines in patients with mitochondrial disorders. Mitochondria play an important role in T cell activation;we therefore propose a pilot study of the administration of trivalent, inactivated influenza vaccine (TIV) to a group of 15 adolescent and adult patients with MELAS syndrome, a specific mitochondrial disorder, to describe solicited adverse events, detailed metabolic responses and an in-depth evaluation of immune responses to TIV. These responses will be compared with those of healthy control volunteers 18-30 yrs of age. Blood samples on all subjects will be taken prior to immunization, at 6h, 5-7 days and 25-28 days following immunization. In Aim 1, biomarkers of mitochondrial function in blood will be described to determine if TIV causes oxidative stress. This will include GC and tandem mass spectrometric assays for metabolomic profiling in plasma with measurement of reduced (GSH) and oxidized (GSSG) glutathione, organic acids, amino acids, acylcarnitines and other metabolites;FACS assays for intracellular GSH, intracellular reactive oxygen species, intracellular reactive nitrogen species and surface thiols. In Aim 2, immune response will be examined to assess if traits change with mitochondrial dysfunction and age, which traits correlate with a robust or poor antibody immune response and whether antibody and T cell responses are affected by mitochondrial dysfunction. This will be accomplished by analysis of 42 cytokines in serum using the Luminex system, white blood cell subsetting into 15 separate categories, gene expression studies performed on RNA using the Agilent 44K microarray, lymphocyte proliferation studies in the different T cell subsets with cytokine analysis of supernatants, influenza-specific T cell responses with measurement of cytokines, and multiplex cell signaling using phosphoflow assays. This proposal is unique in that it examines for the first time the effects of immunization on the metabolic status of patients who are at risk for metabolic decompensation following oxidative stress, and whether MELAS syndrome affects the T cell and antibody response to TIV. Analysis of these results will allow for selection of certain assays that can be tested in subsequent studies of younger patients where smaller blood volumes limit the number of assays that can be done. PUBLIC HEALTH RELEVANCE: This proposed pilot study will provide important new information about how patients with MELAS syndrome, a form of mitochondrial disease, tolerate immunization with flu vaccine in comparison with healthy young adult controls. Special studies of biomarkers in the blood will tell us if immunization causes oxidative stress in these groups and if so, whether this might be related to adverse events. Lastly, intense evaluation of immune responses in these groups will look for biomarkers that predict protective responses to influenza vaccine and that might be affected by this mitochondrial disorder.