National Seroprevalence of Coxiella burnetii in Chile, 2016–2017

Abstract

Coxiella burnetii is an intracellular bacterium and the cause of the zoonotic infection, Q fever. National surveillance data on C. burnetii seroprevalence is currently not available for any South American country, making efforts of public health to implement strategies to mitigate infections in different at-risk groups within the population extremely challenging. In the current study, we used two commercial anti-C. burnetii immunoassays to screen sera collected from a sample of the Chilean population as part of a 2016–2017 national health survey (n = 5166), nationwide and age-standardized. The seroprevalence for C. burnetii for persons ≥ 15 years was estimated to be 3.0% (95% CI 2.2–4.0), a level similar to national surveys from The Netherlands (2.4%) and USA (3.1%), but lower than Australia (5.6%). A linear increase of C. burnetii seropositivity was associated with an individual’s age, with the peak seroprevalence 5.6% (95% CI 3.6–8.6) observed in the ≥65 years’ group. C. burnetii seropositivity was significantly higher in the southern macro-zone 6.0% (95% CI 3.3–10.6) compared to metropolitan region 1.8% (95% CI 0.9–3.3), the former region being home to significant livestock industries, particularly dairy farming. These data will be useful to inform targeted strategies for the prevention of Q fever in at-risk populations in Chile.

Identification of Immunogenic Linear B-Cell Epitopes in C. burnetii Outer Membrane Proteins Using Immunoinformatics Approaches Reveals Potential Targets of Persistent Infections

“…As previously shown in Table 4, between 20% and 33% of responders to the epitopes OMP-H (51)(52)(53)(54)(55)(56)(57)(58)(59) , OMP-H (91-106) , Com-1 (57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76) , Com-1 (191)(192)(193)(194)(195)(196)(197)(198)(199)(200)(201)(202)(203)(204)(205)(206) , and OMP-P1 (215-227) presented high levels of specific antibodies. Aiming to explore these data, we compared the clinical features of high responders (HR: RI > 2), low responders (LR: 1 > RI ≤ 2), and nonresponders (NR: RI ≤ 1) to each studied peptide.…”

“…Moreover, in the C. burnetii-reactive group, the frequencies of response against the epitopes OMP-H (51-59) (65%), OMP-H (91-106) (50%), Com-1 (57-76) (58%), Com-1 (191-206) (58%), and OMP-P1 (215-227) (15 responders; 58%) were higher than 50%. Moreover, the frequency of response to OMP-P1 (197-209) (23%) was statistically lower than the frequencies of response to OMP-H (51-59) (p = 0.0047), Com-1 (57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76) , Com-1 (191)(192)(193)(194)(195)(196)(197)(198)(199)(200)(201)(202)(203)(204)(205)(206) , and OMP-P1 (215-227) (p = 0.0227) (Figure 2b). Despite these differences, we 2c).…”

“…Based on this, seroprevalence surveys arise as a potential way to evaluate the real prevalence of C. burnetii [19]. However, despite studies in the Netherlands [59,60], Australia [61], the USA [62], Bhutan [63], Northern Ireland [64], Cyprus [65], and South America [66,67], the true global prevalence of C. burnetii infections is still unknown due to the dearth of representative national seroprevalence surveys in the world. In this scenario, the identification of linear B-cell epitopes arises as a potential approach to improve and accelerate the development of novel diagnostic tests that could allow effective C. burnetii seroprevalence surveys.…”

“…The antigenicity of predicted linear epitopes was evaluated using the VaxiJen algorithm. Based on this evaluation, eight predicted epitopes were considered antigenic, among which were the four sequences predicted as linear B-cell epitopes by the three used algorithms (OMP-H (51)(52)(53)(54)(55)(56)(57)(58)(59) , OMP-H (98)(99)(100)(101)(102)(103)(104)(105)(106) , Com-1 (57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76) , and Com-1 (191)(192)(193)(194)(195)(196)(197)(198)(199)(200)(201)(202)(203)(204)…”

“…Regarding the exposition of epitopes on protein quaternary structures, predicted epitopes OMP-H (51)(52)(53)(54)(55)(56)(57)(58)(59) and OMP-H (91-106) (Figure 1a,b), Com-1 (191-206) (Figure 1c,d), and OMP-P1 (197)(198)(199)(200)(201)(202)(203)(204)(205)(206)(207)(208)(209) and OMP-P1 (215-227) (Figure 1e,f) were exposed on the trimer surface, and did not interact with other chains in the oligomeric structure; meanwhile, the epitopes Com-1 (57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76) , Com-1 (26-34) (Figure 1d), and OMP-P1 (98-106) (Figure 1e) presented, 25%, 78%, and 56%, respectively, of their sequences interacting with other chains when the predicted OMP trimeric structure was analyzed. Therefore, predicted epitopes Com-1 (26-34) (Figure 1d…”