Prevalence of Coxiella burnetii in bovine bulk milk samples in southern Iran

One hundred (100) bovine bulk milk samples were tested for the presence of Coxiella burnetii and the detection of associated risk factors. Of the tested samples, 11% tested positive for C. burnetii. There was no correlation between the presence of C. burnetii in bulk milk samples and the kind of dairy herd the samples were taken from the number of cows in each site, and the variety of water and food. The only association that was found corresponded with seasonal samples.     

Frequency of anti-Coxiella burnetii antibodies in cattle with reproductive disorders

In this serological study, Q fever was detected in dairy cattle with reproductive problems. A total of 161 sera (74 samples from 9 dairy cattle with reproductive problems and 87 sera from 10 apparently healthy cattle herds) were collected randomly. The CHEKIT Q fever ELISA kit (IDEXX) was used to identify specific antibodies against Coxiella burnetii in dairy cattle. The results showed that 51.35% of dairy cattle with reproductive problems and 10.3% cattle without problems were positive (P?<?0.05). This first serosurvey suggests coxiellosis is an important cause in cattle with reproductive problems, and the disease may cause abortion and other reproductive problems in cattle.     

Investigation of <Emphasis Type="Italic">Coxiella burnetii</Emphasis> in Iranian camels

Coxiella burnetii is a zoonotic, obligate intracellular bacterium that caused Q fever. Antibodies to this organism have been reported in a wide range of animals including mammals, reptiles, amphibians, and birds. This study is aimed to detect C. burnetii in camel by polymerase chain reaction (PCR). Blood samples from 130 camels were collected between August and September 2011 then examined in laboratory conditions. Detection of the presence of C. burnetii DNA was carried out using a PCR assay with specific primers (Coc-F and Coc-R) targeting the 16S ribosomal RNA gene (242 bp). In this study, a total of 14 (10.76 %) camel blood samples were found PCR positive for C. burnetii. This result proves that camels are an important reservoir of C. burnetii infection. This study showed relatively high positivity of C. burnetii in Iranians camels, and accordingly, it seems necessary to evaluate the prevalence for this microorganism in Iran.     

Emergence of Q Fever Arthritis in France

Osteoarticular infection is an uncommon presentation of Q fever. Positron emission tomography (PET) scanning is a valuable tool for the diagnosis of Coxiella burnetii graft prosthesis infection and endocarditis. Our objective was to test a series of culture-negative osteoarticular samples using molecular assays for Coxiella burnetii. We tested for C. burnetii by molecular assays targeting the IS1111 and the IS30A spacer regions, using culture-negative osteoarticular samples obtained in our laboratory between January 2011and December 2012. We examine a total of 1,410 osteoarticular samples, and we observed two cases of arthritis and subacromial bursitis caused by C. burnetii. The infections were localized using PET scanning, and the diagnosis was confirmed through serology. For one, a C. burnetii strain with a multispacer sequence type 8 genotype was isolated from synovial fluid culture. Q fever articular infections could be undiagnosed because of the long evolution of articular attack, and patients with high antibody titers against C. burnetii should be tested using PET scanning to localize the site of infection.     

Characterization of a Lipopolysaccharide-Targeted Monoclonal Antibody and Its Variable Fragments as Candidates for Prophylaxis against the Obligate Intracellular Bacterial Pathogen Coxiella burnetii

Our previous study demonstrated that treatment of Coxiella burnetii with the phase I lipopolysaccharide (PI-LPS)-targeted monoclonal antibody (MAb) 1E4 significantly inhibited C. burnetii infection in mice, suggesting that 1E4 is a protective MAb. To determine whether passive transfer of antibodies (Abs) can provide protection against C. burnetii natural infection, we examined if passive transfer of 1E4 would protect SCID mice against C. burnetii aerosol infection. The results indicated that 1E4 conferred significant protection against aerosolized C. burnetii, suggesting that 1E4 may be useful for preventing C. burnetii natural infection. To further understand the mechanisms of 1E4-mediated protection and to test the possibility of using humanized 1E4 to prevent C. burnetii infection, we examined whether the Fab fragment of 1E4 (Fab1E4), a recombinant murine single-chain variable fragment (muscFv1E4), and a humanized single-chain variable fragment (huscFv1E4) retained the ability of 1E4 to inhibit C. burnetii infection. The results indicated that Fab1E4, muscFv1E4, and huscFv1E4 were able to inhibit C. burnetii infection in mice but that their ability to inhibit C. burnetii infection was lower than that of 1E4. In addition, treatment of C. burnetii with Fab1E4, muscFv1E4, or huscFv1E4 can block C. burnetii infection of macrophages. Interestingly, treatment of C. burnetii with huscFv1E4 can significantly reduce C. burnetii infectivity in human macrophages. This report provides the first evidence to demonstrate that the humanized variable fragments of an LPS-specific MAb can neutralize C. burnetii infection and appears to be a promising step toward the potential use of a humanized MAb as emergency prophylaxis against C. burnetii exposure.     

Neutrophils Play an Important Role in Protective Immunity against Coxiella burnetii Infection

Coxiella burnetii is an obligate intracellular Gram-negative bacterium that causes the zoonotic disease Q fever. Although Q fever is mainly transmitted by aerosol infection, study of the immune responses in the lung following pulmonary C. burnetii infection is lacking. Neutrophils are considered the first immune cell to migrate into the lung and play an important role in host defense against aerosol infection with microbial pathogens. However, the role of neutrophils in the host defense against C. burnetii infection remains unclear. To determine the role of neutrophils in protective immunity against C. burnetii infection, the RB6-8C5 antibody was used to deplete neutrophils in mice before intranasal infection with C. burnetii. The results indicated that neutrophil-depleted mice developed more severe disease than their wild-type counterparts, suggesting that neutrophils play an important role in host defense against C. burnetii pulmonary infection. We also found that neither CXC chemokine receptor 2 (CXCR2) nor interleukin-17 (IL-17) receptor (IL-17R) deficiency changed the severity of disease following intranasal C. burnetii challenge, suggesting that keratinocyte-derived chemokine and IL-17 may not play essential roles in the response to C. burnetii infection. However, significantly higher C. burnetii genome copy numbers were detected in the lungs of IL-1R^−/− mice at 14 days postinfection. This indicates that IL-1 may be important for the clearance of C. burnetii from the lungs following intranasal infection. Our results also suggest that neutrophils are involved in protecting vaccinated mice from C. burnetii challenge-induced disease. This is the first study to demonstrate an important role for neutrophils in protective immunity against C. burnetii infection.     

Role of B Cells in Host Defense against Primary Coxiella burnetii Infection

Despite Coxiella burnetii being an obligate intracellular bacterial pathogen, our recent study demonstrated that B cells play a critical role in vaccine-induced immunity to C. burnetii infection by producing protective antibodies. However, the role of B cells in host defense against primary C. burnetii infection remains unclear. In this study, we investigated whether B cells play an important role in host defense against primary C. burnetii infection. The results showed that peritoneal B cells were able to phagocytose virulent C. burnetii bacteria and form Coxiella-containing vacuoles (CCVs) and that C. burnetii can infect and replicate in peritoneal B1a subset B cells in vitro, demonstrating a potential role for peritoneal B cells in host defense against C. burnetii infection in vivo. In addition, the results showing that B1a cells secreted a high level of interleukin-10 (IL-10) in response to C. burnetii infection in vitro suggest that B1a cells may play an important role in inhibiting the C. burnetii infection-induced inflammatory response. The observation that adoptive transfer of peritoneal B cells did not significantly affect the severity of C. burnetii infection-induced diseases in both severe combined immunity-deficient (SCID) and μMT mice indicates that peritoneal B cells alone may not be able to control C. burnetii infection. In contrast, our finding that C. burnetii infection induced more-severe splenomegaly and a higher bacterial burden in the spleens of B1a cell-deficient Bruton''s tyrosine kinase x-linked immunity-deficient (BTK^xid) mice than in their wild-type counterparts further suggests that B1a cells play an important role in host defense against primary C. burnetii infection.     

Coxiella burnetii in non-Hodgkin lymphoma tissue samples: Innocent until proven otherwise?

Purpose

Coxiella burnetii has been suggested as a potential cause of B-cell non-Hodgkin lymphoma (B-NHL), as C. burnetii was detected in B-NHL tissues. To further investigate this potential relationship, we hypothesized that among subjects previously exposed to C. burnetii, the bacterium is more frequently detectable in tissues of patients with B-NHL (cases) compared to patients without B-NHL (controls).

Comparative study for the detection of antibodies to Neospora caninum in milk and sera in dairy cattle in southern Romania

The study aimed to assess the within-herd Neospora caninum exposure in dairy cattle in southern Romania, based on the detection of specific antibodies in milk and serum. A total of 104 paired samples of milk and serum were collected from four dairy farms. Individual samples were analyzed for N. caninum antibodies by ELISA: IDEXX Neospora Ab (Idx) (three farms: A, B, C; n = 60) and ID-VET Lab (Idv) (farm D; n = 44). Additionally, four pooled milk samples, one per each farm (A, B, C) and a composed one (A+B+C), were analyzed with Idx ELISA. Optimized cut-off values for milk samples were determined by receiver operating characteristic (ROC) analysis, with serum results considered as true status. The agreement was expressed by K values. The overall seroprevalence of N. caninum infection was 45% in the farms tested by Idx ELISA and 56.8% in the farm tested by Idv ELISA. A good agreement between serum and milk was obtained for both ELISA kits (K = 0.72 and 0.77, respectively). The specificity and sensitivity at optimized cut-off of S/P>0.704 for Idx and S/P%>7.966% for Idv were 100% and 70.37% for Idx and 89.47% and 88% for Idv. Testing pooled milk samples, there were identified as N. caninum positive the dairy farms with a 15% or higher within-herd seroprevalence at the cut-off value of S/P>0.51. This is the first study in Romania in which milk samples were tested to determine the N. caninum infection status in dairy farms, providing a base for further researches.     

High Coxiella burnetii DNA Load in Serum during Acute Q Fever Is Associated with Progression to a Serologic Profile Indicative of Chronic Q Fever

PCR is very effective in diagnosing acute Q fever in the early stages of infection, when bacterial DNA is present in the bloodstream but antibodies have not yet developed. The objective of this study was to further analyze the diagnostic value of semiquantitative real-time PCR (qPCR) in diagnosing acute Q fever in an outbreak situation. At the Jeroen Bosch Hospital, in 2009, qPCR testing for Coxiella burnetii DNA was performed for 2,715 patients suspected of having acute Q fever (positive, n = 385; negative, n = 2,330). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the qPCR assay were calculated for patients with negative qPCR results with a follow-up sample obtained within 14 days (n = 305) and qPCR-positive patients with at least one follow-up sample (n = 369). The correctness of the qPCR result was based on immunofluorescence assay results for samples submitted for qPCR and follow-up testing. The sensitivity of the Q fever qPCR assay was 92.2%, specificity 98.9%, PPV 99.2%, and NPV 89.8%. Patients who later developed serologic profiles indicative of chronic Q fever infection had significantly higher C. burnetii DNA loads during the acute phase than did patients who did not (P < 0.001). qPCR testing is a valuable tool for the diagnosis of acute Q fever and should be used in outbreak situations when the onset of symptoms is <15 days earlier. Special attention is needed in the follow-up monitoring of patients with high C. burnetii DNA loads during the acute phase, as this might be an indicator for the development of a serologic profile indicative of chronic infection.     

Role of CD4+ and CD8+ T Cells in Clearance of Primary Pulmonary Infection with Coxiella burnetii

The mechanisms of the primary adaptive immune response to Coxiella burnetii are not well known. Following inoculation of the lungs with C. burnetii Nine Mile phase I (NMI), SCID mice developed pneumonia and splenomegaly and succumbed to infection, whereas wild-type mice cleared the infection by 24 days. SCID mice reconstituted with either CD4⁺ T cells or CD8⁺ T cells alone were able to control the infection, indicating that the presence of either type of T cells was sufficient to control infection, and B cells were not necessary for primary immunity. Similarly, wild-type mice depleted of either CD4⁺ T cells or CD8⁺ T cells controlled infections in their lungs, but these mice were highly susceptible if they were depleted of both types of T cells. However, compared to CD4⁺ T-cell-dependent protection, CD8⁺ T-cell-dependent protection resulted in less inflammation in the lungs and less growth of bacteria in the spleens.Coxiella burnetii, the etiologic agent of Q fever, is thought to be a widely underdiagnosed cause of pneumonia. Acute infections with this organism commonly result in a self-limiting, febrile illness with pulmonary involvement, reflecting the typical acquisition of the infection by the aerosol route. Complications associated with such infections include development of a chronic phase in certain susceptible individuals which presents as endocarditis and has a high fatality rate in the absence of appropriate treatment. Interest in this organism has recently been piqued by its inclusion on the list of potential bioterror agents. Notwithstanding the relatively low mortality rate associated with C. burnetii infections, this organism is highly infectious and has the capacity to cause significant morbidity (16, 23).Two phase variants C. burnetii have been found; phase I is highly virulent and is the naturally occurring variant, and phase II occurs following repeated passage through cell cultures. The two phases differ in lipopolysaccharide (LPS) structure. Phase I C. burnetii encodes a complete LPS with an O side chain, while phase II C. burnetii expresses a truncated LPS lacking the O side chain and some additional sugar residues (10). Andoh et al. (2) examined the comparative virulence of the two variants in SCID and immunocompetent mice using the intraperitoneal (i.p.) route of inoculation and demonstrated that some replication of C. burnetii Nine Mile phase II (NMII) took place in immunocompromised mice but not in immunocompetent mice. This finding suggests that an acquired immune system is required for control of infection with this organism (3).Aerosols are thought to be the most common cause of transmission of Coxiella to humans and other mammals. However, very little is known about the effects of this route of infection at the cellular level. To date, most studies using animal models of C. burnetii infection have utilized the intraperitoneal (i.p.) route of inoculation, and while these studies have provided important data, this route of infection may not entirely reproduce the pulmonary sequelae of most human infections (3). Studies of pulmonary Coxiella infection in guinea pigs (15) and in BALB/c and SCID mice (21) demonstrated that lymphocytes accumulate early during primary lung infection. However, the subsets of lymphocytes elicited in the primary pulmonary response and the role of each subset were not clearly defined. The availability of a protective vaccine against C. burnetii has enabled studies of the immune response to postvaccine Coxiella challenge, which showed that the adaptive immune response is involved in successful resolution of postvaccination Coxiella infections. Indeed, studies using vaccination models have suggested that the predominant immune response to i.p. infection is T cell mediated (12). Immunized B-cell-deficient mice are capable of clearing i.p. delivered C. burnetii NMI, although the mice exhibit histopathological changes, suggesting that B cells may be important for controlling inflammatory damage during a secondary response, possibly through production of interleukin-10 (IL-10) (3).     

Bacteriological and molecular investigation of B. melitensis in dairy cows in Iran

It is extremely important to investigate the presence of Brucella melitensis as a nonspecific and heterogeneous agent in dairy cows in Iran due to mixed populations of sheep, goats, and cattle. B. melitensis from infected sheep or goat herds may be introduced into the cattle population in this area. Hence, it is essential to obtain epidemiological data on the probable existence of B. melitensis as a different source of the infection or new exotic Brucella phenotypes development in dairy cow herds in Iran. The purpose of this study was to investigate the presence of B. melitensis infection in cows, using both traditional bacteriological tests and polymerase chain reaction (PCR)-based assay. Traditional biotyping and PCR results of 42 Brucella spp. isolates from Tehran and Fars (northern and southern) provinces of Iran identified five (11.9%) and 37 (88.1%) as B. melitensis (four biovar 1 and one biovar 2) and 37 (88.1%) Brucella abortus biovar 3. This study demonstrated that B. melitensis infection in dairy cows of Iran is still present at a low level. However, the Iranian Veterinary Organization should be careful to have dairy cow herds free of B. melitensis infection as a nonspecific agent of brucellosis, since this type of brucellosis may be extended and act as a potential source of severe infection in humans.     

Fluorescence in situ hybridization for detecting Coxiella burnetii in tissue samples from chronic Q fever patients

ObjectiveDetection of the intracellular bacterium Coxiella burnetii, causative agent of chronic Q fever, is notoriously difficult. Diagnosis of and duration of antibiotic treatment for chronic Q fever is partly determined by detection of the bacterium with polymerase chain reaction (PCR). Fluorescence in situ hybridization (FISH) might be a promising technique for detecting C. burnetii in tissue samples from chronic Q fever patients, but its value in comparison with PCR is uncertain. We aim to assess the value of FISH for detecting C. burnetii in tissue of chronic Q fever patients.MethodsFISH and PCR were performed on tissue samples from Dutch chronic Q fever patients collected during surgery or autopsy. Sensitivity, specificity, and overall diagnostic accuracy were calculated. Additionally, data on patient and disease characteristics were collected from electronic medical records.ResultsIn total, 49 tissue samples from mainly vascular walls, heart valves, or placentas, obtained from 39 chronic Q fever patients, were examined by FISH and PCR. The sensitivity and specificity of FISH compared to PCR for detecting C. burnetii in tissue samples from chronic Q fever patients was 45.2% (95% confidence interval (CI), 27.3% – 64.0%) and 84.6% (95% CI, 54.6% – 98.1%), respectively. The overall diagnostic accuracy was 56.8% (95% CI, 42.2% - 72.3%). Two C. burnetii PCR negative placentas were FISH positive. Four FISH results (8.2%) were deemed inconclusive because of autofluorescence.ConclusionWith an overall diagnostic accuracy of 57.8%, we conclude that FISH has limited value in the routine diagnostics of chronic Q fever.     

Q Fever in the Greek Island of Crete: Detection, Isolation, and Molecular Identification of Eight Strains of Coxiella burnetii from Clinical Samples

Over a period of 6 years (1989 to 1995), serum samples from 3,300 patients suspected to be infected by Coxiella burnetii were assayed for the presence of antibodies against antigen phase II of the microorganism by the indirect immunofluorescence antibody technique (IFAT). One hundred fifty-two cases were recorded, and blood samples from 17 patients were cultured for the isolation of the pathogen. By a centrifugation shell vial technique, eight strains were isolated from patients suffering from acute Q fever. The microorganism was detected in the cultures by IFAT, by Gimenez staining, and by the cytopathogenic effect on Vero and human embryonic lung (HEL) cells. PCR followed by restriction fragment length polymorphism analysis was used to confirm the diagnosis and identify the Coxiella burnetii strains within the cell cultures as well as to compare them with reference strains. In order to avoid time-consuming cultures, to achieve direct detection of Coxiella burnetii in clinical samples (blood, buffy coat, etc.), and to increase the specificity and sensitivity of the detection, nested PCR was performed. The first step of DNA extraction was performed with the QIAamp blood kit 250. For the second step of the PCR assays, the conditions of temperature and times of recycling were properly modified, and the microorganism was detected within 4 h. Our study demonstrates that Q fever is an endemic disease in Crete and that the diagnosis of Coxiella burnetii infection can be rapidly achieved by the detection of the microorganism in buffy coat samples by nested PCR. Although the presenting symptoms of the disease in this study differed from those in other studies, the Cretan strains do not differ genotypically from the reference strains (Nine Mile and Q212).     

Formalin-Inactivated Coxiella burnetii Phase I Vaccine-Induced Protection Depends on B Cells To Produce Protective IgM and IgG

To further understand the mechanisms of formalin-inactivated Coxiella burnetii phase I (PI) vaccine (PIV)-induced protection, we examined if B cell, T cell, CD4⁺ T cell, or CD8⁺ T cell deficiency in mice significantly affects the ability of PIV to confer protection against a C. burnetii infection. Interestingly, compared to wild-type (WT) mice, PIV conferred comparable levels of protection in CD4⁺ T cell- or CD8⁺ T cell-deficient mice and partial protection in T cell-deficient mice but did not provide measurable protection in B cell-deficient mice. These results suggest that PIV-induced protection depends on B cells. In addition, anti-PI-specific IgM was the major detectable antibody (Ab) in immune sera from PIV-vaccinated CD4⁺ T cell-deficient mice, and passive transfer of immune sera from PIV-vaccinated CD4⁺ T cell-deficient mice conferred significant protection. These results suggest that T cell-independent anti-PI-specific IgM may contribute to PIV-induced protection. Our results also suggested that PIV-induced protection may not depend on complement activation and Fc receptor-mediated effector functions. Furthermore, our results demonstrated that both IgM and IgG from PIV-vaccinated WT mouse sera were able to inhibit C. burnetii infection in vivo, but only IgM from PIV-vaccinated CD4⁺ T cell-deficient mouse sera inhibited C. burnetii infection. Collectively, these findings suggest that PIV-induced protection depends on B cells to produce protective IgM and IgG and that T cell-independent anti-PI-specific IgM may play a critical role in PIV-induced protection against C. burnetii infection.     

Serological follow-up in patients with aorto-iliac disease and evidence of Q fever infection

The aim of this study was to provide data on the risk of developing chronic Q fever in patients with aorto-iliac disease and evidence of previous Q fever infection. Patients with an aortic and/or iliac aneurysm or aorto-iliac reconstruction (aorto-iliac disease) and evidence of previous Q fever infection were included. The presence of phase I and II Coxiella burnetii IgG antibodies was assessed periodically using immunofluorescence assay. A total of 111 patients with aorto-iliac disease were divided into three groups, based upon the serological profile [mean follow-up: 16?±?9 months (mean?±?standard deviation)]. Group 1 consisted of 30 patients with a serological trace of C. burnetii infection (negative IgG phase I, IgG phase II titer of 1:32). Of these, 36.7 % converted to serological profile matching past resolved Q fever. Group 2 included 49 patients with negative IgG phase I titer and IgG phase II titer ≥1:64. No patients developed chronic Q fever, but 14.3 % converted to a positive IgG phase I titer. Group 3 consisted of 32 patients with positive IgG phase I and positive IgG phase II titers, of which 9.4 % developed chronic Q fever (significantly different from group 2, p?=?0.039). The IgG phase I titer increased in 28.1 % of patients (from 1:64 to 1:4,096). The risk of developing chronic Q fever in patients with aorto-iliac disease and previous Q fever infection with a positive IgG phase I titer was 9.4 %. The IgG phase I titer increases or becomes positive in a substantial number of patients. A standardized serological follow-up is proposed.     

Clinical Evaluation of a New PCR Assay for Detection of Coxiella burnetii in Human Serum Samples

A nested PCR method was developed for the detection of Coxiella burnetii in human serum samples. Two pairs of oligonucleotide primers were designed to amplify a 438-bp fragment of the com1 gene encoding a 27-kDa outer membrane protein of C. burnetii. The primers amplified the predicted fragments of 21 various strains of C. burnetii but did not react with DNA samples from other microorganisms. The 438-bp amplification products could be digested with restriction enzymes SspI and SalI. The utility of the nested PCR was evaluated by testing human serum samples. The com1 gene fragment was amplified from 135 (87%) of 155 indirect immunofluorescence test (IF)-positive serum samples and from 11 (11%) of 100 IF-negative serum samples. The nested PCR with primers targeted to the com1 gene appeared to be a sensitive, specific, and useful method for the detection of C. burnetii in serum samples.     

Coxiella burnetii Effector Proteins That Localize to the Parasitophorous Vacuole Membrane Promote Intracellular Replication

The intracellular bacterial pathogen Coxiella burnetii directs biogenesis of a parasitophorous vacuole (PV) that acquires host endolysosomal components. Formation of a PV that supports C. burnetii replication requires a Dot/Icm type 4B secretion system (T4BSS) that delivers bacterial effector proteins into the host cell cytosol. Thus, a subset of T4BSS effectors are presumed to direct PV biogenesis. Recently, the PV-localized effector protein CvpA was found to promote C. burnetii intracellular growth and PV expansion. We predict additional C. burnetii effectors localize to the PV membrane and regulate eukaryotic vesicle trafficking events that promote pathogen growth. To identify these vacuolar effector proteins, a list of predicted C. burnetii T4BSS substrates was compiled using bioinformatic criteria, such as the presence of eukaryote-like coiled-coil domains. Adenylate cyclase translocation assays revealed 13 proteins were secreted in a Dot/Icm-dependent fashion by C. burnetii during infection of human THP-1 macrophages. Four of the Dot/Icm substrates, termed Coxiella vacuolar protein B (CvpB), CvpC, CvpD, and CvpE, labeled the PV membrane and LAMP1-positive vesicles when ectopically expressed as fluorescently tagged fusion proteins. C. burnetii ΔcvpB, ΔcvpC, ΔcvpD, and ΔcvpE mutants exhibited significant defects in intracellular replication and PV formation. Genetic complementation of the ΔcvpD and ΔcvpE mutants rescued intracellular growth and PV generation, whereas the growth of C. burnetii ΔcvpB and ΔcvpC was rescued upon cohabitation with wild-type bacteria in a common PV. Collectively, these data indicate C. burnetii encodes multiple effector proteins that target the PV membrane and benefit pathogen replication in human macrophages.     

Low-dose priming before vaccination with the phase I chloroform-methanol residue vaccine against Q fever enhances humoral and cellular immune responses to Coxiella burnetii

Although the phase I Coxiella burnetii cellular vaccine is completely efficacious in humans, adverse local and systemic reactions may develop if immune individuals are inadvertently vaccinated. The phase I chloroform-methanol residue (CMRI) vaccine was developed as a potentially safer alternative. Human volunteers with no evidence of previous exposure to C. burnetii received a subcutaneous vaccination with the CMRI vaccine in phase I studies under protocol IND 3516 to evaluate the safety and immunogenicity of the vaccine. This clinical trial tested escalating doses of the CMRI vaccine, ranging from 0.3 to 60 μg, followed by a booster dose of 30 μg, in a placebo-controlled study. Although priming doses of the CMRI vaccine did not induce a specific antibody detectable by enzyme-linked immunosorbent assay, booster vaccination stimulated the production of significant levels of anti-C. burnetii antibody. Peripheral blood cells (PBCs) of vaccinees responded to C. burnetii cellular antigen in vitro in a vaccine dose-dependent manner. After the booster dose, PBCs were activated by recall antigen in vitro, regardless of the priming dose. These findings suggest that vaccination with the CMRI vaccine can effectively prime the immune system to mount significant anamnestic responses after infection.