Alterations in the human plasma lipidome in response to Tularemia vaccination

Abstract

31Tularemia is a rare but highly contagious and potentially fatal disease caused by bacteria 32 Francisella tularensis where as few as ten inhaled organisms can lead to an infection, making it 33 one of the most infectious microorganisms known and a potential bioweapon. To better 34 understand the response to a live, attenuated tularemia vaccine and the biological pathways 35 altered post-vaccination, healthy adults were vaccinated by scarification and plasma was 36 collected pre-and post-vaccination for longitudinal lipidomics studies. Using tandem mass 37 spectrometry, we identified and quantified individual lipid molecular species within 38 representative lipid classes in plasma to characterize alterations in the plasma lipidome during 39 the vaccine response. Separately, we targeted oxylipins, a subset of lipid mediators involved in 40 inflammatory pathways. We identified 14 differentially abundant lipid species from eight lipid 41 classes. These included 5-Hydroxyeicosatetraenoic acid (5-HETE), an eicosanoid produced 42 following arachidonic acid liberation and epoxygenation, which is indicative of lipoxygenase 43 activity and, subsequently, inflammation. Results suggest that 5-HETE was metabolized to a 44 dihydroxyeicosatrienoic acid (DHET) by Day 7 post-vaccination, shedding light on the kinetics 45 of the 5-HETE-mediated inflammatory response. In addition to 5-HETE and DHET, we 46 observed pronounced changes in 34:1 phosphatidylinositol, anandamide, oleamide, ceramides, 47 16:1 cholesteryl ester, and several glycerophospholipids, several of these changes in abundance 48 were correlated with serum cytokines and T cell activation. These data provide new insights into 49 alterations in plasma lipidome post tularemia vaccination, potentially identifying key mediators 50 and pathways involved in vaccine response and efficacy. 51 52 53Vaccines initially trigger innate immune responses that result in development of an adaptive 54 immune response with establishment of immunological memory (1). This process is 55 incompletely understood but is probably best detailed for the Yellow Fever vaccine (2). This 56 vaccine is highly effective and elicits a wide range of immune responses, resulting in greater than 57 30 years of protection from yellow fever. Previously published research has shown that the 58 vaccine produces a biologic signature identified by transcriptomics, cytokine analyses and flow 59 cytometry (3). Such biologic signatures may correlate with immunogenicity to predict the 60 efficacy of novel vaccines. Lipids are key stress-response and immune signaling molecules and 61 changes in their circulating concentrations reflect a host of immune processes(4) (5) (6). Thus, 62 lipids play a critical role in inflammation. Accordingly, performing lipidomics analysis is a key 63 element in the systems-wide multi-omic platform approaches leveraging data from 64 transcriptomics, metabolomics, and proteomics to obtain a comprehensive picture of the vaccine 65 response. 67Tularemia, caused by the intracellular ...

Proteomic Analysis of Human Immune Responses to Live-Attenuated Tularemia Vaccine

“…In addition, the activation of PPARγ can shift production from pro- to anti-inflammatory mediators [ 40 ]. Interestingly, lipidomic analyses of plasma samples derived from the same subjects revealed increased metabolism (decreased abundance) of the pro-inflammatory 5-hudroxyeicosatetraenoic acid (5-HETE, an eicosanoid) lipid by Day 7 post-vaccination, associated with an apparent compensatory increase in dihydroxyeicosatetraenoic acid (DHET) lipid levels [ 23 ]. The pro-inflammatory function of 5-HETE is known to be regulated through conversion to its inactive and less active metabolites, DHET lipids by the Cytochrome P450F family of proteins.…”

“…Related transcriptomic analyses demonstrated that gene CYP4F22 was upregulated on Day 2 post-vaccination (1.7-fold increase), Day 7 post-vaccination (1.5-fold increase), and Day 14 post-vaccination (1.8-fold increase). Several Cytochrome P450 family genes, including CYP1B1 and CYP4V2 , were also differentially expressed [ 23 ]. Because cytochrome P450 genes are important for the conversion of pro-inflammatory 5-HETE into inactive DHET metabolites, the transcriptomic results further supported the conclusion that 5-HETE is induced early in the acute response to live tularemia vaccination, followed by the induction of Cytochrome P450 gene expression and the subsequent conversion of 5-HETE into inactive DHET species.…”

“…In parallel, a LC-MS/MS approach was carried out on PBMC lysates after trypsin digestion, followed by protein identification and relative abundance calculation using a label-free quantification method to determine differential protein abundance. Samples from the same subjects were also studied by microarrays [ 15 ], RNAseq (unpublished data) and metabolomics [ 23 ], as well as lipidomics [ 23 ], to determine changes in gene expression, lipids, and metabolites (results of these other omic platforms are reported separately).…”

Transcriptomic and Metabolic Responses to a Live-Attenuated Francisella tularensis Vaccine

“…They can be activated by fatty acids of the 5-hudroxyeicosatetraenoic acid (5-HETE) family [ 57 ]. Interestingly, lipidomic analyses of the same samples in our related study revealed increased metabolism (decreased abundance) of the pro-inflammatory 5-hudroxyeicosatetraenoic acid (5-HETE) lipid by day 7 post-vaccination, associated with a compensatory increase in dihydroxyeicosatetraenoic acid (DHET) lipid levels [ 23 ]. The pro-inflammatory function of 5-HETE is known to be regulated through conversion to its inactive and less active metabolites, DHET lipids, by the Cytochrome P450F family of proteins.…”

“…In both experiments, blood from day 0 (pre-vaccination) and from days 1, 2, 7, and 14 post-vaccination was sampled and processed. We also performed proteomics and lipidomics experiments on the same cohort and time points, which are described in referenced materials [ 22 , 23 ] and are cross-referenced in the discussion section.…”