24Infection with Coxiella burnetii, the causative agent of Q fever, can result in life-threatening 25 persistent infection. Reactogenicity hinders worldwide implementation of the only licensed 26 human Q fever vaccine. We previously demonstrated long-lived immunoreactivity in individuals 27 with past symptomatic and asymptomatic Coxiella infection (convalescents) to promiscuous 28 HLA-class II C. burnetii epitopes, providing the basis for a novel T-cell-targeted subunit 29 vaccine. Here we investigated in a cohort of 22 individuals with persistent infection (chronic Q 30 fever) whether they recognize the same set of epitopes, or distinct epitopes that could be 31 candidates for a therapeutic vaccine or aid in the diagnosis of persistent infection.
32Individuals with chronic Q fever showed strong class II epitope-specific cultured ELISpot 33 responses largely overlapping with the peptide repertoire identified previously for convalescents.
34Five additional peptides were recognized more frequently by chronic subjects, but there was no 35 combination of epitopes uniquely recognized by or non-reactive in chronic Q fever subjects.
36Consistent with more recent/prolonged exposure, we found, however, stronger direct ex vivo 37 responses to whole-cell C. burnetii and individual peptides in direct ELISpot than in 38 convalescents.
39In conclusion, we have validated and expanded a previously published set candidate epitopes for 40 a novel T-cell targeted subunit Q fever vaccine in the context of chronic Q fever patients and 41 demonstrated that they successfully mounted a T-cell response comparable to that of 42 convalescents. Finally, we demonstrate that individuals treated for chronic Q fever mount a 43 broader ex vivo response to class II epitopes than convalescents, which could be explored for 44 diagnostic purposes. 45 46 Q fever is a zoonotic disease that is endemic in many countries worldwide. It is caused by the 47 environmentally highly stable small Gram-negative coccobacillus Coxiella burnetii, which is 48 transmitted to humans predominantly by aerosol from infected ruminants such as goats, sheep 49 and cattle (1). Outbreaks usually occur in the occupational setting including the livestock 50 industry and deployed military personnel (1). Coxiella outbreaks can also occur in the general 51 population, the largest to date being the outbreak in the Netherlands from 2007-2010 with an 52 estimated 40,000 infections at the center of the epidemic area alone (2). While infection remains 53 asymptomatic in an estimated 50-60% of individuals and acute symptomatic infection is readily 54 treatable with antibiotics, a large proportion (10-20%) of individual with acute Q fever later 55 develop Q fever fatigue syndrome. Further, 1-5% of (often asymptomatically) infected 56 individuals progress to persistent infection also known as chronic Q fever. Chronic Q fever has a 57 poor prognosis and manifests as endocarditis, infected aneurysms or vascular prosthesis infection 58 in individuals with specific risk factors (1, 3).5...