Natural Exposure- and Vaccination-Induced Profiles of Ex Vivo Whole Blood Cytokine Responses to Coxiella burnetii

Abstract

Q fever is a zoonotic disease caused by the highly infectious Gram-negative coccobacillus, Coxiella burnetii (C. burnetii). The Q fever vaccine Q-VAX® is characterised by high reactogenicity, requiring individuals to be pre-screened for prior exposure before vaccination. To date it remains unclear whether vaccine side effects in pre-exposed individuals are associated with pre-existing adaptive immune responses to C. burnetii or are also a function of innate responses to Q-VAX®. In the current study, we measured innate and adaptive cytokine responses to C. burnetii and compared these among individuals with different pre-exposure status. Three groups were included: n=98 Dutch blood bank donors with unknown exposure status, n=95 Dutch village inhabitants with known natural exposure status to C. burnetii during the Dutch Q fever outbreak of 2007-2010, and n=96 Australian students receiving Q-VAX® vaccination in 2021. Whole blood cytokine responses following ex vivo stimulation with heat-killed C. burnetii were assessed for IFNγ, IL-2, IL-6, IL-10, TNFα, IL-1β, IP-10, MIP-1α and IL-8. Serological data were collected for all three cohorts, as well as data on skin test and self-reported vaccine side effects and clinical symptoms during past infection. IFNγ, IP-10 and IL-2 responses were strongly elevated in individuals with prior C. burnetii antigen exposure, whether through infection or vaccination, while IL-1β, IL-6 and TNFα responses were slightly increased in naturally exposed individuals only. High dimensional analysis of the cytokine data identified four clusters of individuals with distinct cytokine response signatures. The cluster with the highest levels of adaptive cytokines and antibodies comprised solely individuals with prior exposure to C. burnetii, while another cluster was characterized by high innate cytokine production and an absence of C. burnetii-induced IP-10 production paired with high baseline IP-10 levels. Prior exposure status was partially associated with these signatures, but could not be clearly assigned to a single cytokine response signature. Overall, Q-VAX® vaccination and natural C. burnetii infection were associated with comparable cytokine response signatures, largely driven by adaptive cytokine responses. Neither individual innate and adaptive cytokine responses nor response signatures were associated retrospectively with clinical symptoms during infection or prospectively with side effects post-vaccination.

Cytometry profiling of ex vivo recall responses to Coxiella burnetii in previously naturally exposed individuals reveals long-term changes in both adaptive and innate immune cellular compartments

“…Overall, of the bulk cytokine responses evaluated, IFNγ and IL-2 were the most informative for inferring prior exposure. Innate cytokines TNFα and IL-1β also showed some association with prior exposure by natural infection, consistent with previous results ( 43 ), but elevation was more marginal and restricted to specific subgroups of pre-exposed individuals.…”

“…In our study, using CyTOF we also identified a population of C. burnetii -specific CD4 T cells (CD137 + CD154 + CD69 + IFNγ + IL-2 + TNFα + ) that was significantly increased in IGRA-positive individuals, particularly those who had exhibited clinical symptoms and remained seropositive. Co-production of these cytokines by specific cell subsets is consistent with data from a prior study looking at bulk cytokine responses to C. burnetii in individuals with prior exposure to C. burnetii ( 43 ), which showed that individuals with prior exposure and high IFNγ production also produce high amounts of IL-2. Notably, the CD137 + CD154 + CD69 + IFNγ + IL2 + TNFα + CD4 T cell cluster C11 and the corresponding lineage-negative innate cell cluster C19 were the only two cell populations showing clear IFNγ production based on the expression-normalized CyTOF data used for unsupervised clustering.…”

“…Moreover, while stronger adaptive responses in Groups 3 and 5 could theoretically be a result of re-exposure, this in unlikely the case for all individuals in these cohorts since no large outbreaks have been reported after 2010. Of note, trained innate immunity is generally a property of live attenuated whole cell vaccines (67) and indeed we found no evidence for enhanced innate responses following vaccination with the killed whole cell vaccine Q-VAX (43). If such responses indeed are relevant to protection from or future infection, approaches should be considered to combine future C. burnetii vaccines with amplifiers of trained immunity, such as BCG (67).…”

“…We also observed a trend for increased whole blood release of IL-6 and TNFα, which did not reach significance. This is likely due to the small number of individuals assessed in this analysis, since in a previously published study with considerable larger groups from the same village cohort, release of both IL-6 and TNFα from C. burnetii antigen-stimulated whole blood was significantly higher in IGRA-positive individuals compared to controls ( 43 ). CyTOF analysis of C. burnetii antigen-stimulated PBMCs revealed an increased proportion of two innate (CD3 - CD20 - ) clusters in individuals with prior exposure.…”

QuilA® adjuvanted Coxevac® sustains Th1-CD8+-type immunity and increases protection in Coxiella burnetii-challenged goats

“…Increased levels of IL10 , TNFα and IL1β were previously described in peripheral blood of infected pregnant goats before or after parturition 9 . IL1β, IL6 and TNFα production were higher in naturally infected individuals compared to vaccinated ones 46 . Increased levels of inflammatory cytokines (i.e.…”