Adverse events and association with age, sex and immunological parameters of Q fever vaccination in patients at risk for chronic Q fever in the Netherlands 2011

Q fever immunology: the quest for a safe and effective vaccine

Q fever is an infectious zoonotic disease, caused by the Gram-negative bacterium Coxiella burnetii. Transmission occurs from livestock to humans through inhalation of a survival form of the bacterium, the Small Cell Variant, often via handling of animal parturition products. Q fever manifests as an acute self-limiting febrile illness or as a chronic disease with complications such as vasculitis and endocarditis. The current preventative human Q fever vaccine Q-VAX poses limitations on its worldwide implementation due to reactogenic responses in pre-sensitized individuals. Many strategies have been undertaken to develop a universal Q fever vaccine but with little success to date. The mechanisms of the underlying reactogenic responses remain only partially understood and are important factors in the development of a safe Q fever vaccine. This review provides an overview of previous and current experimental vaccines developed for use against Q fever and proposes approaches to develop a vaccine that establishes immunological memory while eliminating harmful reactogenic responses.

Factors associated with Q fever vaccination in Australian wildlife rehabilitators

Australian wildlife rehabilitators (AWR) are at risk of contracting Q fever, a serious zoonotic disease caused by Coxiella burnetii. Despite Australian government recommendations for AWR to receive Q fever vaccination (QFV), and the availability of a safe and effective vaccine in Australia, shortfalls in vaccine uptake have been observed in AWR. This study aimed to determine factors associated with QFV status and describe AWR attitudes and potential barriers towards QFV. Data were obtained from a nationwide, online, cross-sectional survey of AWR undertaken in 2018. Approximately-three quarters (200/265; 75.5 %) of those that had heard of Q fever were also aware of the Q fever vaccine, and of those, 25.5 % (51/200) were vaccinated. Barriers to QFV, among unvaccinated respondents who had also heard of Q fever and the vaccine (149/200; 74.5 %), included concerns regarding the safety, efficacy, and importance of the Q fever vaccine. Complacency toward vaccination, convenience of vaccination, and a lack of Q fever knowledge were also notable barriers. Only 27.7 % (41/148) of respondents reported having had vaccination recommended to them. Multivariable logistic regression identified that vaccinated AWR were more likely to be aged ≤ 50 years (OR 4.51, 95 % CI: 2.14-10.11), have had a university level education (OR 2.78, 95 % CI: 1.39-5.73), have resided in New South Wales/Australian Capital Territory and Queensland than in other Australian jurisdictions (OR 2.9, 95 % CI: 1.10-8.83 and OR 4.82, 95 % CI: 1.64-16.00 respectively) and have attended an animal birth (OR 2.14, 95 % CI: 1.02-4.73). Knowledge gaps regarding Q fever and QFV in AWR demonstrated the need for interventions to raise the awareness of the potential health consequences of C. burnetii exposure and Q fever prevention. Education programs to allow AWR to develop an informed perspective of Q fever and QFV, coupled with improvements in vaccine affordability and the implementation of programs to enhance accessibility, may also increase vaccine uptake.

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

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.

Evaluation of a Human T Cell-Targeted Multi-Epitope Vaccine for Q Fever in Animal Models of Coxiella burnetii Immunity

T cell-mediated immunity plays a central role in the control and clearance of intracellular Coxiella burnetii infection, which can cause Q fever. Therefore, we aimed to develop a novel T cell-targeted vaccine that induces pathogen-specific cell-mediated immunity to protect against Q fever in humans while avoiding the reactogenicity of the current inactivated whole cell vaccine. Human HLA class II T cell epitopes from C. burnetii were previously identified and selected by immunoinformatic predictions of HLA binding, conservation in multiple C. burnetii isolates, and low potential for cross-reactivity with the human proteome or microbiome. Epitopes were selected for vaccine inclusion based on long-lived human T cell recall responses to corresponding peptides in individuals that had been naturally exposed to the bacterium during a 2007-2010 Q fever outbreak in the Netherlands. Multiple viral vector-based candidate vaccines were generated that express concatemers of selected epitope sequences arranged to minimize potential junctional neo-epitopes. The vaccine candidates caused no antigen-specific reactogenicity in a sensitized guinea pig model. A subset of the vaccine epitope peptides elicited antigenic recall responses in splenocytes from C57BL/6 mice previously infected with C. burnetii. However, immunogenicity of the vaccine candidates in C57BL/6 mice was dominated by a single epitope and this was insufficient to confer protection against an infection challenge, highlighting the limitations of assessing human-targeted vaccine candidates in murine models. The viral vector-based vaccine candidates induced antigen-specific T cell responses to a broader array of epitopes in cynomolgus macaques, establishing a foundation for future vaccine efficacy studies in this large animal model of C. burnetii infection.

Immunogenicity and Reactogenicity in Q Fever Vaccine Development

Coxiella burnetii is an obligate intracellular bacterium which, in humans, causes the disease Q fever. Although Q fever is most often a mild, self-limiting respiratory disease, it can cause a range of severe syndromes including hepatitis, myocarditis, spontaneous abortion, chronic valvular endocarditis, and Q fever fatigue syndrome. This agent is endemic worldwide, except for New Zealand and Antarctica, transmitted via aerosols, persists in the environment for long periods, and is maintained through persistent infections in domestic livestock. Because of this, elimination of this bacterium is extremely challenging and vaccination is considered the best strategy for prevention of infection in humans. Many vaccines against C. burnetii have been developed, however, only a formalin-inactivated, whole cell vaccine derived from virulent C. burnetii is currently licensed for use in humans. Unfortunately, widespread use of this whole cell vaccine is impaired due to the severity of reactogenic responses associated with it. This reactogenicity continues to be a major barrier to access to preventative vaccines against C. burnetii and the pathogenesis of this remains only partially understood. This review provides an overview of past and current research on C. burnetii vaccines, our knowledge of immunogenicity and reactogenicity in C. burnetii vaccines, and future strategies to improve the safety of vaccines against C. burnetii.

Recent Advances on the Innate Immune Response to Coxiella burnetii

Coxiella burnetii is an obligate intracellular Gram-negative bacterium and the causative agent of a worldwide zoonosis known as Q fever. The pathogen invades monocytes and macrophages, replicating within acidic phagolysosomes and evading host defenses through different immune evasion strategies that are mainly associated with the structure of its lipopolysaccharide. The main transmission routes are aerosols and ingestion of fomites from infected animals. The innate immune system provides the first host defense against the microorganism, and it is crucial to direct the infection towards a self-limiting respiratory disease or the chronic form. This review reports the advances in understanding the mechanisms of innate immunity acting during C. burnetii infection and the strategies that pathogen put in place to infect the host cells and to modify the expression of specific host cell genes in order to subvert cellular processes. The mechanisms through which different cell types with different genetic backgrounds are differently susceptible to C. burnetii intracellular growth are discussed. The subsets of cytokines induced following C. burnetii infection as well as the pathogen influence on an inflammasome-mediated response are also described. Finally, we discuss the use of animal experimental systems for studying the innate immune response against C. burnetii and discovering novel methods for prevention and treatment of disease in humans and livestock.

Whole Blood Interferon γ Release Is a More Sensitive Marker of Prior Exposure to Coxiella burnetii Than Are Antibody Responses

For the zoonotic disease Q fever, serological analysis plays a dominant role in the diagnosis of Coxiella burnetii infection and in pre-screening for past exposure prior to vaccination. A number of studies suggest that assessment of C. burnetii-specific T-cell IFNγ responses may be a more sensitive tool to assess past exposure. In this study, we assessed the performance of a whole blood C. burnetii IFNγ release assay in comparison to serological detection in an area of high Q fever incidence in 2014, up to seven years after initial exposure during the Dutch Q fever outbreak 2007-2010. In a cohort of >1500 individuals from the Dutch outbreak village of Herpen, approximately 60% had mounted IFNγ responses to C. burnetii. This proportion was independent of the Coxiella strain used for stimulation and much higher than the proportion of individuals scored sero-positive using the serological gold standard immunofluorescence assay. Moreover, C. burnetii-specific IFNγ responses were found to be more durable than antibody responses in two sub-groups of individuals known to have sero-converted as of 2007 or previously reported to the municipality as notified Q fever cases. A novel ready-to-use version of the IFNγ release assay assessed in a subgroup of pre-exposed individuals in 2021 (10-14 years post exposure) proved again to be more sensitive than serology in detecting past exposure. These data demonstrate that C. burnetii-induced IFNγ release is indeed a more sensitive and durable marker of exposure to C. burnetii than are serological responses. In combination with a simplified assay version suitable for implementation in routine diagnostic settings, this makes the assessment of IFNγ responses a valuable tool for exposure screening to obtain epidemiological data, and to identify previously exposed individuals in pre-vaccination screens.

Frequency of Adverse Events Following Q Fever Immunisation in Young Adults

Q fever is a zoonosis of concern in many countries. Vaccination is the most effective means of prevention, and since 1989, Australia has had a licensed Q fever vaccine, Q-VAX^®. This vaccine was also used in the Netherlands in 2011 following the largest recorded Q fever outbreak globally. There is a paucity of available data regarding adverse events following immunisation (AEFI) for young adult females. Such data are important for informing future vaccination recommendations both within Australia and internationally. This study collected Q fever vaccine (Q-VAX^®) AEFI data in veterinary and animal science students at Australian universities. Students were enrolled at the time of vaccination and were emailed a link to an online AEFI survey one week later. Of the 60% (499/827) that responded, 85% were female and the median age was 18 years. Local injection site reactions (ISRs) occurred in 98% (95%; CI 96–99%) of respondents, of which 30% (95% CI 24–32%) were severe. Systemic AEFI occurred in 60% (95%; CI 55–64%) of respondents within the seven days following immunisation. Medical attention was sought by 19/499 (3.8%) respondents, of whom one sought treatment at a hospital emergency department. Females were more likely than males to experience any local ISR (odds ratio [OR] 9.3; 95% CI 2.5–33.8; p < 0.001), ISRs of greater severity (OR 2.5; 95% CI 1.5–4.2; p < 0.001), and any systemic AEFI (OR 1.9; 95% CI 1.1–3.1; p = 0.016). These safety data suggest that a high frequency of adverse events following immunisation should be expected in young adults, particularly females. However, the consequences of Q fever disease are potentially far more debilitating.

Willingness of veterinarians in Australia to recommend Q fever vaccination in veterinary personnel: Implications for workplace health and safety compliance

Q fever vaccine uptake among veterinary nurses in Australia is low, suggesting veterinarians are not recommending the vaccination to veterinary personnel. This study aimed to determine the willingness of veterinarians to recommend Q fever vaccination to veterinary personnel and to identify factors influencing Q fever vaccine uptake by veterinary nurses in Australia. An online cross sectional survey targeted veterinarians and veterinary nurses in Australia in 2014. Responses were analysed using multivariable logistic regression. Factors significantly (p<0.05) associated with a willingness to recommend the vaccination, expressed by 35% (95% CI 31-38%) of veterinarians (n = 828), were (1) being very concerned for colleagues regarding Coxiella burnetii (OR 4.73), (2) disagreeing the vaccine is harmful (OR 3.80), (3) high Q fever knowledge (OR 2.27), (4) working within small animal practice (OR 1.67), (5) disagreeing the vaccine is expensive (OR 1.55), and (6) age, with veterinarians under 39 years most likely to recommend vaccination. Of the veterinary nursing cohort who reported a known Q fever vaccination status (n = 688), 29% (95% CI 26-33%) had sought vaccination. This was significantly (p<0.05) associated with (1) agreeing the vaccine is important (OR 8.34), (2) moderate/high Q fever knowledge (OR 5.51), (3) working in Queensland (OR 4.00), (4) working within livestock/mixed animal practice (OR 3.24), (5) disagreeing the vaccine is expensive (OR 1.86), (6) strong reliance on work culture for biosecurity information (OR 2.5), (7) perceiving personal exposure to Coxiella burnetii to be at least low/moderate (OR 2.14), and (8) both agreeing the vaccine is safe and working within a corporate practice structure (OR 4.28). The study identified the need for veterinarians to take greater responsibility for workplace health and safety promotion, and calls for better education of veterinary personnel to raise awareness of the potential for occupational exposure to C. burnetii and improve the perception of the Q fever vaccine as being important, safe and cost-effective.

Q fever in Spain: Description of a new series, and systematic review

BACKGROUND

Forms of presentation of Q fever vary widely across Spain, with differences between the north and south. In the absence of reported case series from Galicia (north-west Spain), this study sought to describe a Q-fever case series in this region for the first time, and conduct a systematic review to analyse all available data on the disease in Spain.

METHODS

Patients with positive serum antibodies to Coxiella burnetii from a single institution over a 5-year period (January 2011-December 2015) were included. Patients with phase II titres above 1/128 (or documented seroconversion) and compatible clinical criterial were considered as having Q fever. Patients with clinical suspicion of chronic Q-fever and IgG antibodies to phase I-antigen of over 1/1024, or persistently high levels six months after treatment were considered to be cases of probable chronic Q-fever. Systematic review: We conducted a search of the Pubmed/Medline database using the terms: Q Fever OR Coxiella burnetii AND Spain. Our search yielded a total of 318 studies: 244 were excluded because they failed to match the main criteria, and 41 were discarded due to methodological problems, incomplete information or duplication. Finally, 33 studies were included.

RESULTS

A total of 155 patients, all of them from Galicia, with positive serological determination were located during the study period; 116 (75%) were deemed to be serologically positive patients without Q fever and the remaining 39 (25%) were diagnosed with Q fever. A potential exposure risk was found in 2 patients (5%). The most frequent form of presentation was pneumonia (87%), followed by isolated fever (5%), diarrhoea (5%) and endocarditis (3%). The main symptoms were headache (100%), cough (77%) and fever (69%). A trend to a paucisymptomatic illness was observed in women. Hospital admission was required in 37 cases, and 6 patients died while in hospital. Only 2 patients developed chronic Q-fever. Systematic review: Most cases were sporadic, mainly presented during the winter and spring, as pneumonia in 37%, hepatitis in 31% and isolated fever in 29.6% of patients. In the north of Spain, 71% of patients had pneumonia, 13.2% isolated fever and 13% hepatitis. In the central and southern areas, isolated fever was the most frequent form of presentation (40%), followed by hepatitis (38.4%) and pneumonia (17.6%). Only 31.7% of patients reported risk factors, and an urban-environment was the most frequent place of origin. Overall mortality was 0.9%, and the percentage of patients with chronic forms of Q-fever was 2%.

CONCLUSIONS

This is the first study to report on a Q-fever case series in Galicia. It shows that in this region, the disease affects the elderly population -even in the absence of risk factors- and is linked to a higher mortality than reported by previous studies. While pneumonia is the most frequent form of presentation in the north of the country, isolated fever and hepatitis tend to be more frequent in the central and southern areas. In Spain, 32% of Q-fever cases do not report contact with traditional risk factors, and around 58% live in urban areas.

From Q Fever to Coxiella burnetii Infection: a Paradigm Change

Coxiella burnetii is the agent of Q fever, or "query fever," a zoonosis first described in Australia in 1937. Since this first description, knowledge about this pathogen and its associated infections has increased dramatically. We review here all the progress made over the last 20 years on this topic. C. burnetii is classically a strict intracellular, Gram-negative bacterium. However, a major step in the characterization of this pathogen was achieved by the establishment of its axenic culture. C. burnetii infects a wide range of animals, from arthropods to humans. The genetic determinants of virulence are now better known, thanks to the achievement of determining the genome sequences of several strains of this species and comparative genomic analyses. Q fever can be found worldwide, but the epidemiological features of this disease vary according to the geographic area considered, including situations where it is endemic or hyperendemic, and the occurrence of large epidemic outbreaks. In recent years, a major breakthrough in the understanding of the natural history of human infection with C. burnetii was the breaking of the old dichotomy between "acute" and "chronic" Q fever. The clinical presentation of C. burnetii infection depends on both the virulence of the infecting C. burnetii strain and specific risks factors in the infected patient. Moreover, no persistent infection can exist without a focus of infection. This paradigm change should allow better diagnosis and management of primary infection and long-term complications in patients with C. burnetii infection.

Tolerability of 2 doses of pandemic influenza vaccine (Focetria®) and of a prior dose of seasonal 2009-2010 influenza vaccination in the Netherlands

In the Netherlands, people indicated for seasonal influenza vaccination are divided in 3 risk groups, i.e. those less than 60 y (y) with comorbidity and those 60 y and over with and without comorbidity. Those risk groups were also eligible for pandemic vaccination during the 2009 influenza A(H1N1) pandemic. We assessed tolerability of seasonal influenza vaccination and 2 doses of pandemic influenza A(H1N1) vaccine, adjuvanted with MF-59, administered 2 and 5 weeks after seasonal 2009-2010 vaccination among adults. Vaccinees were asked to return questionnaires on local and systemic adverse events (AEs) after each of 3 consecutive vaccinations given at the office of their General Practitioner. Sex- and risk group-specific AE-frequencies were calculated. Generalized Linear Mixed Model with seasonal vaccination as reference was used to calculate odds ratios (ORs) for AEs of the 2 pandemic doses. 5553 questionnaires (3251 vaccinees) were returned. Vaccinees reported any local AE after seasonal vaccination and both pandemic doses in 34%, 23%, and 18%, respectively. These percentages were 29%, 25%, and 16% for any systemic AE. Men reported fewer local and systemic AEs then women (p<0.0001). The risk of local (OR range 0.34-0.63) and systemic (OR range 0.39-0.99) AEs (overall, stratified by risk group and by sex) was lower after both pandemic doses compared to seasonal vaccination. This decreased risk was more pronounced after the second pandemic dose than after the first. Therefore, we conclude that MF59-adjuvanted pandemic vaccine given after seasonal vaccination was well tolerated.

Coverage of the 2011 Q fever vaccination campaign in the Netherlands, using retrospective population-based prevalence estimation of cardiovascular risk-conditions for chronic Q fever

Background

In 2011, a unique Q fever vaccination campaign targeted people at risk for chronic Q fever in the southeast of the Netherlands. General practitioners referred patients with defined cardiovascular risk-conditions (age >15 years). Prevalence rates of those risk-conditions were lacking, standing in the way of adequate planning and coverage estimation. We aimed to obtain prevalence rates retrospectively in order to estimate coverage of the Q fever vaccination campaign.

Methods

With broad search terms for these predefined risk-conditions, we extracted patient-records from a large longitudinal general-practice research-database in the Netherlands (IPCI-database). After validation of these records, obtained prevalence rates (stratified for age and sex) extrapolated to the Q fever high-incidence area population, gave an approximation of the size of the targeted patient-group. Coverage calculation addressed people actually screened by a pre-vaccination Q fever skin test and serology (coverage) and patients referred by their general practitioners (adjusted-coverage) in the 2011 campaign.

Results

Our prevalence estimate of any risk-condition was 3.1% (lower-upper limits 2.9-3.3%). For heart valve defects, aorta aneurysm/prosthesis, congenital anomalies and endocarditis, prevalence was 2.4%, 0.6%, 0.4% and 0.1%, respectively. Estimated number of eligible people in the Q fever high-incidence area was 11,724 (10,965-12,532). With 1330 people screened for vaccination, coverage of the vaccination campaign was 11%. For referred people, the adjusted coverage was 18%. Coverage was lowest among the very-old and highest for people aged 50–70 years.

Conclusion

The estimated coverage of the vaccination campaign was limited. This should be interpreted in the light of the complexity of this target-group with much co-morbidity, and of the vaccine that required invasive pre-vaccination screening. Calculation of prevalence rates of risk-conditions based on the IPCI-database was feasible. This procedure proved an efficient tool for future use, when prevalence estimates for policy, implementation or surveillance of subgroup-vaccination or other health-care interventions are needed.

Genetic Variation in Pattern Recognition Receptors and Adaptor Proteins Associated With Development of Chronic Q Fever

BACKGROUND

Q fever is an infection caused by Coxiella burnetii. Persistent infection (chronic Q fever) develops in 1%-5% of patients. We hypothesize that inefficient recognition of C. burnetii and/or activation of host-defense in individuals carrying genetic variants in pattern recognition receptors or adaptors would result in an increased likelihood to develop chronic Q fever.

METHODS

Twenty-four single-nucleotide polymorphisms in genes encoding Toll-like receptors, nucleotide-binding oligomerization domain-like receptor-2, αvβ3 integrin, CR3, and adaptors myeloid differentiation primary response protein 88 (MyD88), and Toll interleukin 1 receptor domain-containing adaptor protein (TIRAP) were genotyped in 139 patients with chronic Q fever and in 220 controls with cardiovascular risk-factors and previous exposure to C. burnetii. Associations between these single-nucleotide polymorphisms and chronic Q fever were assessed by means of univariate logistic regression models. Cytokine production in whole-blood stimulation assays was correlated with relevant genotypes.

RESULTS

Polymorphisms in TLR1 (R80T), NOD2 (1007fsX1), and MYD88 (-938C>A) were associated with chronic Q fever. No association was observed for polymorphisms in TLR2, TLR4, TLR6, TLR8, ITGAV, ITGB3, ITGAM, and TIRAP. No correction for multiple testing was performed because only genes with a known role in initial recognition of C. burnetii were included. In the whole-blood assays, individuals carrying the TLR1 80R-allele showed increased interleukin 10 production with C. burnetii exposure.

CONCLUSIONS

Polymorphisms in TLR1 (R80T), NOD2 (L1007fsX1), and MYD88 (-938C>A) are associated with predisposition to development of chronic Q fever. For TLR1, increased interleukin 10 responses to C. burnetii in individuals carrying the risk allele may contribute to the increased risk of chronic Q fever.