Cellular and molecular response of human macrophages exposed to Aggregatibacter actinomycetemcomitans leukotoxin

Aggregatibacter (Actinobacillus) actinomycetemcomitans is a facultative anaerobic gram-negative bacterium associated with severe forms of periodontitis. A leukotoxin, which belongs to the repeats-in-toxin family, is believed to be one of its virulence factors and to have an important role in the bacterium's pathogenicity. This toxin selectively kills human leukocytes by inducing apoptosis and lysis. Here, we report that leukotoxin-induced cell death of macrophages proceeded through a process that differs from the classical characteristics of apoptosis and necrosis. A. actinomycetemcomitans leukotoxin-induced several cellular and molecular mechanisms in human macrophages that led to a specific and excessive pro-inflammatory response with particular secretion of both interleukin (IL)-1β and IL-18. In addition, this pro-inflammatory cell death was inhibited by oxidized ATP, which indicates involvement of the purinergic receptor P2X(7) in this process. This novel virulence mechanism of the leukotoxin may have an important role in the pathogenic potential of this bacterium and can be a target for future therapeutic agents.

Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters

Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.

Transcriptional profiling of the peripheral blood response during tularemia

Tularemia is a febrile disease caused by the highly contagious bacterium Francisella tularensis. We undertook an analysis of the transcriptional response in peripheral blood during the course of ulceroglandular tularemia by use of Affymetrix microarrays comprising 14,500 genes. Samples were obtained from seven individuals at five occasions during 2 weeks after the first hospital visit and convalescent samples 3 months later. In total, 265 genes were differentially expressed, 95 of which at more than one time point. The differential expression was verified with real-time quantitative polymerase chain reaction for 36 genes (R(2)=0.590). The most prominent changes were noted in samples drawn on days 2-3 and a considerable proportion of the upregulated genes appeared to represent an interferon-gamma-induced response and also a proapoptotic response. Genes involved in the generation of innate and acquired immune responses were found to be downregulated, presumably a pathogen-induced event. A logistic regression analysis revealed that seven genes were good predictors of the early phase of tularemia. This is the first description of the transcriptional host response to ulceroglandular tularemia and the study has identified gene subsets relevant to the pathogenesis of the disease and subsets that may serve as early diagnostic biomarkers.

A case of Q fever acquired in Sweden and isolation of the probable ethiological agent, Coxiella burnetii from an indigenous source

Serologically verified indigenous Q fever is described in a 52-y-old male, who presented with persistent fever, muscle and joint pain, headache and non-purulent cough. Institution of doxycycline resulted in prompt recovery. Coxiella burnetii was isolated from mouldy hay in a barn. The strain differs from previously isolated ones in Sweden.

V gamma 9V delta 2 T cells in human legionellosis

In humans, expansion of circulating Vgamma9Vdelta2 T cells seems to be a pathophysiological denominator shared by protozoan and intracellular bacterial diseases. The assumption was tested here on legionellosis, a condition conforming to the category but not yet described with respect to gammadelta T cells. Levels of Vgamma9Vdelta2 T cells in peripheral blood were measured at various intervals in 14 subjects undergoing a Pontiac fever-like disease, shown by serological investigation to be caused by Legionella micdadei. In samples obtained 4 to 6 days after the onset of the disease, the mean percentage (+/- the standard deviation) of Vgamma9Vdelta2+ T cells among CD3+ cells was 1.0% +/- 0.5%, compared to 5.0% +/- 3.9% in healthy control subjects (P < 0.001). Thereafter, a pronounced increase occurred and at 2 to 7 weeks after onset, mean peak levels were as high as approximately equal to 15%. During the next 6 months, values slowly declined, although without reaching the normal range. Percentages of gammadelta+ T cells expressing tumor necrosis factor alpha or gamma interferon in response to phorbol myristate acetate were assayed in vitro. At 14 to 16 days after the onset of disease, the expression of both cytokines was increased (P < 0.01), whereas at 5 to 7 weeks, the expression of tumor necrosis factor alpha was decreased (P < 0.05), possibly reflecting modulation of an inflammatory response. In conclusion, Pontiac fever was found to be associated with a pronounced and long-lasting expansion of Vgamma9Vdelta2 T cells, implying that the subset may also be pathophysiologically important in a mild and transient form of intracellular bacterial diseases. Surprisingly, the expansion was preceded by a depletion of circulatory Vgamma9Vdelta2 T cells. Possibly, Vgamma9Vdelta2 T cells are initially recruited to a site of infection before they expand in response to antigen and occur in high numbers in blood.

Extensive allelic variation among Francisella tularensis strains in a short-sequence tandem repeat region

Members of the genus Francisella and the species F. tularensis appear to be genetically very similar despite pronounced differences in virulence and geographic localization, and currently used typing methods do not allow discrimination of individual strains. Here we show that a number of short-sequence tandem repeat (SSTR) loci are present in F. tularensis genomes and that two of these loci, SSTR9 and SSTR16, are together highly discriminatory. Labeled PCR amplification products from the loci were identified by an automated DNA sequencer for size determination, and each allelic variant was sequenced. Simpson's index of diversity was 0.97 based on an analysis of 39 nonrelated F. tularensis isolates. The locus showing the highest discrimination, SSTR9, gave an index of diversity of 0.95. Thirty-two strains isolated from humans during five outbreaks of tularemia showed much less variation. For example, 11 of 12 strains isolated in the Ljusdal area, Sweden in 1995 and 1998 had identical allelic variants. Phenotypic variants of strains and extensively cultured replicates within strains did not differ, and, for example, the same allelic combination was present in 55 isolates of the live-vaccine strain of F. tularensis and another one was present in all 13 isolates of a strain passaged in animals. The analysis of short-sequence repeats of F. tularensis strains appears to be a powerful tool for discrimination of individual strains and may be useful for a detailed analysis of the epidemiology of this potent pathogen.

Francisella tularensis induces cytopathogenicity and apoptosis in murine macrophages via a mechanism that requires intracellular bacterial multiplication

The murine macrophage-like cell line J774.A1 ingests and allows intracellular growth of Francisella tularensis. We demonstrate that, after 24 h of infection, a pronounced cytopathogenicity resulted and the J774 cells were undergoing apoptosis. Despite this host cell apoptosis, no decrease in bacterial numbers was observed. When internalization of bacteria was prevented or intracellularly located F. tularensis bacteria were eradicated within 12 h, the progression of host cell cytopathogenicity and apoptosis was prevented.

Long-lasting recall response of CD4+ and CD8+ alphabeta T cells, but not gammadelta T cells, to heat shock proteins of francisella tularensis

Decades after recovery from tularemia, circulating alphabeta T cells are known to still recognize a variety of membrane proteins of Francisella tularensis. We studied the T cell response to 3 cytoplasmic heat shock proteins of the organism: DnaK, chaperone-60 (Cpn-60) and Cpn-10. Determination of subpopulations of responding T cells was of special interest as it has been suggested that homologs of these conserved proteins may be recognized by human gammadelta T cells. Compared with reference subjects with no history of tularemia or tularemia vaccination, subjects who had been infected with tularemia 10-30 y earlier showed a significantly (p = 0.01) higher proliferative T cell response to all 3 heat shock proteins. In general, the magnitude of responses of CD4 T cells was higher than that of CD8 T cells. By flow cytometry, blast cells were shown to express the alphabeta T cell receptor. Under conditions that allowed vigorous expansion of gammadelta T cells in response to a phosphorylated non-peptide antigen, no expansion of gammadelta T cells occurred in response to DnaK or Cpn60 of F. tularensis. In conclusion, a long-lasting recall response to heat shock proteins of F. tularensis was demonstrated in alphabeta T cells but not in gammadelta T cells. The results support the assumption that human alphabeta T cells recognize bacterial proteins irrespective of the nature or localization of the proteins in the bacterial cell and thereby contribute to the maintenance of a long-lasting broad T cell response based on a wide variety of specificities.

Sequencing of the Francisella tularensis strain Schu 4 genome reveals the shikimate and purine metabolic pathways, targets for the construction of a rationally attenuated auxotrophic vaccine

Francisella tularensis is the etiological agent of tularemia, a serious disease in several Northern hemisphere countries. The organism has fastidious growth requirements and is very poorly understood at the genetic and molecular levels. Given the lack of data on this organism, we undertook the sample sequencing of its genome. A random library of DNA fragments from a highly virulent strain (Schu 4) of F. tularensis was constructed and the nucleotide sequences of 13,904 cloned fragments were determined and assembled into 353 contigs. A total of 1.83 Mb of nucleotide sequence was obtained that had a G+C content of 33.2%. Genes located on plasmids pOM1 and pNFL10, which had been previously isolated from low virulence strains of F. tularensis, were absent but all of the other known F. tularensis genes were represented in the assembled data. F. tularensis Schu4 was able to grow in the absence of aromatic amino acids and orthologues of genes which could encode enzymes in the shikimate pathway in other bacteria were identified in the assembled data. Genes that could encode all of the enzymes in the purine biosynthetic and most of the en- zymes in the purine salvage pathways were also identified. This data will be used to develop defined rationally attenuated mutants of F. tularensis, which could be used as replacements for the existing genetically undefined live vaccine strain.

Evaluation of PCR-based methods for discrimination of Francisella species and subspecies and development of a specific PCR that distinguishes the two major subspecies of Francisella tularensis

Previous studies have demonstrated that the four subspecies of the human pathogen Francisella tularensis, despite showing marked variations in their virulence for mammals and originating from different regions in the Northern Hemisphere, display a very close phylogenetic relationship. This property has hampered the development of generally applicable typing methods. To overcome this problem, we evaluated the use of PCR for discrimination of the subspecies using various forms of long arbitrary primers or primers specific for repetitive extragenic palindromic sequences (REP) or enterobacterial repetitive intragenic consensus (ERIC) sequences. Patterns generated by use of REP, ERIC, or long arbitrary primers allowed differentiation at the species level and of the four subspecies of F. tularensis. With each of these three methods, similar or identical clustering of strains was found, and groups of strains of different geographical origins or differing in virulence showed distinct patterns. The discriminatory indices of the methods varied from 0.57 to 0.65; thus, the patterns were not sufficiently discriminatory to distinguish individual strains. The sequence of a fragment generated by amplification with an arbitrary primer was determined, and a region showing interstrain heterogeneity was identified. Specific primers were designed, and a PCR was developed that distinguished strains of F. tularensis subsp. holarctica from strains of other F. tularensis subspecies, including strains of the highly virulent F. tularensis subsp. tularensis. Notably, one European isolate showed the genetic pattern typical of the highly virulent F. tularensis subsp. tularensis, generally believed to exist only in North America. It is proposed that a combination of the specific PCR together with one method generating subspecies-specific patterns is suitable as a rapid and relatively simple strategy for discrimination of Francisella species and subspecies.

Cytocidal and apoptotic effects of the ClyA protein from Escherichia coli on primary and cultured monocytes and macrophages

Cytolysin A (ClyA) is a newly discovered cytolytic protein of Escherichia coli K-12 that mediates a hemolytic phenotype. We show here that highly purified ClyA and ClyA-expressing E. coli were cytotoxic and apoptogenic to fresh as well as cultured human and murine monocytes/macrophages.

The proportion of circulating gammadelta T cells increases after the first week of onset of tularaemia and remains elevated for more than a year

In various human intracellular bacterial diseases, an increase of the proportion of circulating Vgamma9Vdelta2 T cells has been observed. The prevalence of the finding among infected subjects and the time course of the elevation remain to be investigated. In the present study, comprising blood samples from a large number of cases of ulceroglandular tularaemia, the percentage of Vgamma9Vdelta2 T cells within the first week of onset of disease (5.3 +/- 0.7% (mean +/- s.e.m.)) did not differ from that of control subjects (5.3 +/- 0. 8%). Thereafter, percentages increased rapidly and within the interval of 8-40 days mean levels were > 20% (P < 0.001). Of 45 individuals sampled within 3 months of onset, 42 showed a percentage of Vgamma9Vdelta2 T cells of > 10%. Significantly increased levels were still recorded at 18 months (13.8 +/- 2.4%; P < 0.05) but not at 24 months (10.2 +/- 2.1%; P > 0.10). Thus, a consistent increase of circulating Vgamma9Vdelta2 T cells was demonstrated in tularaemia. The initial delay and the prolonged course of elevation may suggest a role in immunoregulation and/or immunological memory. Furthermore, the percentage of gammadelta T cells expressing tumour necrosis factor-alpha in response to phorbol myristate acetate was decreased during the first week and up to 40 days after onset, possibly reflecting the modulation of an inflammatory response.

Ciprofloxacin for treatment of tularemia in children

BACKGROUND

Children with tularemia are, irrespective of severity of disease, usually subjected to parenteral treatment with aminoglycosides. Based on available susceptibility testing, quinolones might be effective oral alternatives of parenteral therapy. These drugs cause arthropathy in immature animals, but this risk is currently regarded to be low in humans.

PATIENTS AND METHODS

In 12 patients (median age, 4 years; range, 1 to 10) with ulceroglandular tularemia, a 10- to 14-day course of oral ciprofloxacin, 15 to 20 mg/kg daily in 2 divided doses, was prescribed. Microbiologic investigations included identification of the infectious agent by PCR and culture of wound specimens, as well as determination of antibiotic susceptibility of isolates of Francisella tularensis.

RESULTS

Defervescence occurred within 4 days of institution of oral ciprofloxacin in all patients. After a median period of 4.5 days (range, 2 to 24), the patients were capable of outdoor activities. In 2 cases, treatment was withdrawn after 3 and 7 days because of rash. In both cases a second episode of fever occurred. All children recovered without complications. In 7 cases F. tularensis was successfully cultured from ulcer specimens and tested for susceptibility to ciprofloxacin. MIC values for all isolates were 0.03 mg/l.

CONCLUSION

In our sample of 12 patients ciprofloxacin was satisfactory for outpatient treatment of tularemia in children.

Comparative analysis of PCR versus culture for diagnosis of ulceroglandular tularemia

PCR and culture were comparatively evaluated for their abilities to demonstrate Francisella tularensis in wound specimens from tularemia patients during an outbreak in Sweden in 1998. For transport of the specimens used for PCR, a buffer solution containing a nuclease inhibitor was used, and for transport of the specimens used for culture, a commercial transport system was selected after experimental comparison of various systems. Of 40 patients with culture- and/or serology-verified ulceroglandular tularemia, PCR detected F. tularensis DNA in 30 (75%) patients, whereas culture detected bacterial growth in 25 (62%) patients. Compared to data from a previous study, the present inclusion of a nuclease inhibitor in the transport medium did not improve the sensitivity of the PCR, whereas the sensitivity of the culture procedure was significantly increased by selection of the system used for transport. Among eight patients with clinically suspected tularemia but with negative serology and culture, specimens from four patients showed detectable DNA. In three of these patients the diagnosis was verified by the demonstration of an F. tularensis-specific T-cell response in vitro. In conclusion, PCR was more sensitive than culture for demonstration of F. tularensis in wound specimens. Besides, we showed that tularemia may proceed without development of serum antibodies, and in these patients, PCR may be of special importance for verification of the diagnosis.

Early cytokine induction in mouse P388D1 macrophages infected by Coxiella burnetii

Q-fever is caused by Coxiella burnetii, which is an obligate intracellular bacterium with a broad spectrum of host cells, including macrophages. Cytokines produced from macrophages infected by intracellular bacteria play a critical role in the expression of innate immune responses as well as in the subsequent triggering of protective acquired cell-mediated immunity. We followed the induction and secretion of the pro-inflammatory cytokines interleukin 1 alpha (IL-1alpha), tumor necrosis factor alpha (TNF-alpha), and interleukin 12 (IL-12) in the macrophage-like mouse cell line P388D1 during the initial phase of an in vitro infection by virulent C. burnetii Nine Mile. Secretion of IL-1alpha and TNF-alpha were observed within 3 h post-inoculation. IL-12, however, was not detected in cell supernatants. Two forms of C. burnetii exist, virulent phase I and avirulent phase II organisms. To determine whether the cytokine response was dependent on the form of C. burnetii, the induction of IL-1alpha and TNF-alpha in infected P388D1 cells was compared. Both cytokines were produced by macrophages early after infection with Phase I bacteria. A similar induction of TNF-alpha was observed after infection with the avirulent Phase II bacteria, but no IL-1alpha induction could be detected. As the only difference identified between the two forms of C. burnetii is the composition of their lipopolysaccharides (LPS), the ability of each of the purified LPS from the two variants to induce IL-1alpha was investigated. Purified C. burnetii LPS induced a moderate IL-1alpha response in comparison to that induced by the efficient stimulator E. coli LPS. Furthermore, there was no significant difference in action between Phase I and Phase II LPS preparations. We thus postulate that factors other than LPS differ between the two variants of C. burnetii, and these differences may account for differences in IL-1alpha induction.

Rapid local expression of interleukin-12, tumor necrosis factor alpha, and gamma interferon after cutaneous Francisella tularensis infection in tularemia-immune mice

Francisella tularensis LVS is an effective live vaccine strain used for cutaneous vaccination against tularemia in man. In mice, injection of LVS causes invasive disease and subsequent development of immunity that is characterized by effective control of otherwise lethal doses of the organism. In the present investigation, it is shown that LVS-immune mice controlled an intradermal infection much more effectively than did naive mice; bacterial counts in skin samples were 1.5 to 2.0 log10 lower 24 h after injection and 6 log10 lower 72 h after injection in immune mice. Moreover, in contrast to naive mice, no bacteria were demonstrated in samples from livers and spleens of immune mice. By immunohistochemistry, skin samples from immune mice showed an intense staining for interleukin-12 (IL-12) and a moderate staining for tumor necrosis factor alpha (TNF-alpha) at 24 h postinoculation, after which staining for both cytokines faded. In naive mice, the staining for IL-12 was weak at all time points and no staining for TNF-alpha was observed. No staining for gamma interferon (IFN-gamma) was observed in any group before 72 h. At that time point, skin samples from immune mice showed moderate staining and skin samples from naive mice showed weak staining. Reverse transcriptase PCR showed an induction of mRNA of the three cytokines in the skin within the first day after injection. A quantitative analysis demonstrated higher IFN-gamma and TNF-alpha mRNA levels in immune mice at 24 h postinoculation. In conclusion, immunization with F. tularensis LVS conferred a capability to respond to cutaneous reinfection, with rapid local expression of IL-12, TNF-alpha, and IFN-gamma, and this expression was paralleled by containment and mitigation of the infection. The cytokine response may be part of a local barrier function of the skin, important to host protection against tularemia.

Expansion of Vgamma9 Vdelta2 T cells is triggered by Francisella tularensis-derived phosphoantigens in tularemia but not after tularemia vaccination

Tularemia is a disease caused by the facultative intracellular bacterium Francisella tularensis. Here we demonstrate that during the first weeks of infection, a significant increase in levels of Vgamma9 Vdelta2 cells occurred in peripheral blood: in 13 patients analyzed 7 to 18 days after the onset of disease, these lymphocytes represented, on average, 30.5% of CD3+ cells and nearly 100% of gammadelta+ T cells. By contrast, after vaccination with the live vaccine strain (LVS) of F. tularensis, only a minor increase occurred. Eleven days after vaccination, gammadelta T cells represented an average of 6.7% and Vgamma9 Vdelta2 cells represented an average of 5.3% of T cells, as in control subjects. Since derivatives of nonpeptidic pyrophosphorylated molecules, referred to as phosphoantigens, are powerful stimuli for Vgamma9 Vdelta2 cells, this observation prompted an investigation of phosphoantigens in F. tularensis strains. The F. tularensis phosphoantigens triggered in vitro a proliferative response of human Vgamma9 Vdelta2 peripheral blood leukocytes as well as a cytotoxic response and tumor necrosis factor release from a Vgamma9 Vdelta2 T-cell clone. Quantitatively similar phosphoantigenic activity was detected in acellular extracts from two clinical isolates (FSC171 and Schu) and from LVS. Taken together, the chemical nature of the stimulus from the clinical isolates and the significant increase in levels of Vgamma9 Vdelta2 cells in peripheral blood of tularemia patients indicate that phosphoantigens produced by virulent strains of F. tularensis trigger in vivo expansion of gammadelta T cells in tularemia.

Genotypic and phenotypic characterization of two Swedish isolates and two prototypic strains of Coxiella burnetii

Two Swedish isolates of Coxiella burnetii and the two prototype strains of the species, Nine Mile and Priscilla, were characterized with regard to their multiplication and cytopathic effect on BGM cells and by PCR-based amplification of repetitive element DNA and the C. burnetii-specific plasmids QpH1 and QpRS. Moreover, 1330 bp of each 16S rRNA gene were sequence-determined. All four strains multiplied at virtually the same rate and displayed the same type of vacuoles in the BGM cells. Genetic homogeneity was observed inasmuch as the 16S rDNA sequences were identical and the strains showed identical PCR amplification patterns using primers specific to enterobacterial repetitive intragenic consensus DNA sequences. The two Swedish strains and the Priscilla strain also showed identical patterns after PCR amplification of repetitive extragenic palindromic DNA sequences, whereas the Nine Mile strain demonstrated a similar, but not identical pattern. Thus, the investigated strains demonstrated very similar phenotypic and genotypic characteristics. This finding is discussed in view of the very rare occurrence of domestic Q fever in Sweden.

Infrequent manifestations of tularaemia in Sweden

Since 1931, when tularaemia was first recognized in Sweden, the annual incidence has varied widely. Except for a few cases, ulceroglandular and respiratory tularaemia have been the only forms of the disease observed. Here, cases from Sweden of oropharyngeal tularaemia and of tularaemia septicaemia and meningitis, are reviewed. Since the cases occurred outside manifest outbreaks, diagnostic difficulties were encountered and the diagnosis was reached more by chance than due to clinical suspicion. Possibly, cryptic cases of tularaemia may be more frequent than what appears from clinical reports.

Identification of proteins of Francisella tularensis induced during growth in macrophages and cloning of the gene encoding a prominently induced 23-kilodalton protein

The adaptation of facultative intracellular bacteria to host macrophages involves regulation of the synthesis of bacterial proteins. We analyzed the protein synthesis of Francisella tularensis LVS growing intracellularly in the macrophage-like murine cell line J774 and extracellularly in culture medium. After pulse-labeling with [35S] methionine and separation by one- and two-dimensional polyacrylamide gel electrophoresis, induction of a few proteins during intracellular growth was demonstrated. One of them, a 23-kDa protein, was prominently induced in the macrophages and also when extracellularly growing F. tularensis was exposed to hydrogen peroxide. After isolation of the 23-kDa protein from a preparative two-dimensional gel, a 22-amino-acid N-terminal peptide and two peptides obtained by trypsin digestion were sequenced. Based on the sequences, degenerate oligonucleotides were constructed for use as primers in a PCR. Hybridization of amplified DNA to XbaI-digested LVS DNA identified the gene of the 23-kDa protein in a 1.3-kb DNA fragment. Nucleotide sequence analysis revealed an open reading frame encoding a putative protein of a calculated molecular mass of 22.2 kDa. The open reading frame was preceded by a sequence typical of ribosome-binding sites in Escherichia coli. The amplified gene was successfully expressed by the pTrc99A vector in E. coli under control of the trc promoter. The gene product showed the same mobility and immunoreactivity as the 23-kDa protein of F. tularensis. The deduced amino acid sequence showed no significant homology with protein sequences in current data banks. Thus, intracellular growth of F. tularensis in macrophages was associated with prominent upregulation of a novel 23-kDa protein.

Characterization of the nucleotide sequence of the groE operon encoding heat shock proteins chaperone-60 and -10 of Francisella tularensis and determination of the T-cell response to the proteins in individuals vaccinated with F. tularensis

The groE operon of Francisella tularensis LVS, encoding the heat shock proteins chaperone-10 (Cpn10) and Cpn60, was sequenced and characterized, and the T-cell response of LVS-vaccinated individuals to the two proteins and the third major chaperone, Ft-DnaK, was assayed. The cpn10 and cpn60 genes were amplified by PCR with degenerate oligonucleotides derived from the N-terminal sequence of the two proteins. The sequence analysis revealed the expected two open reading frames, encoding proteins with estimated Mrs of 10,300 and 57,400. The deduced amino acid sequences closely resembled Cpn10 and Cpn60 proteins of other prokaryotes. The genes constituted a bicistronic operon, the cpn10 gene preceding the cpn60 gene. Upstream of the cpn10 gene, an inverted repeat and motifs similar to -35 and -10 sequences of sigma70-dependent but not of sigma32-dependent promoters of Escherichia coli were found. The inverted repeat of the operon resembled so-called hairpin loops identified in other characterized prokaryotic groE operons lacking sigma32-dependent promoters. Primer extension analysis disclosed one and the same transcription start, irrespective of the presence or absence of heat or oxidative stress. After separation of lysates of the F. tularensis LVS organism by two-dimensional gel electrophoresis, DnaK, Cpn60, and Cpn10 were extracted and used as antigens in T-cell tests. When compared to those from nonvaccinated individuals, T cells from individuals previously vaccinated with live F. tularensis LVS showed an increased proliferative response to DnaK and Cpn60 but not to Cpn10. The present data will facilitate further studies of the involvement of the heat shock proteins in protective immunity to tularemia.

Detection of Francisella tularensis in ulcers of patients with tularemia by PCR

The diagnosis of human cases of tularemia is usually confirmed by the demonstration of an antibody response to Francisella tularensis, which occurs about 2 weeks after the onset of disease. Due to a high risk of infection in the laboratory, cultivation of the causative agent tends to be avoided. During an outbreak in Sweden, the use of PCR for diagnosing the ulceroglandular form of tularemia was evaluated. Extraction and preparation of F. tularensis DNA from swab samples from the wounds of patients with tularemia involved the use of the nuclease inhibitor guanidine thiocyanate. The DNA was detected by multiplex PCR targeting the 16S rRNA gene and a 17-kDa lipoprotein gene of F. tularensis. In 29 of 40 (73%) patients with serologically confirmed tularemia, F. tularensis DNA was successfully amplified. Considering the limitations of current diagnostic procedures, PCR may become useful for the early diagnosis of tularemia.

Specific detection of Coxiella burnetii through partial amplification of 23S rDNA

A previously published sequence of the 23S rRNA gene of Coxiella burnetii has been reported to contain an intervening sequence of 444 base pairs (bp). The sequence information on the intervening sequence and the 23S rRNA gene was exploited to develop a specific PCR-based assay for C. burnetii. A primer set was designed that amplified a 477-bp fragment encompassing part of the intervening sequence and part of the 23S rDNA. From all of nine C. burnetii strains tested, a fragment of the expected size was amplified. As predicted from the published sequence, restriction endonuclease digestion of the PCR product from the Coxiella strains with RsaI produced two distinct fragments approximately 210- and 270-bp in size. The PCR-based method showed a detection limit of 10(2) bacteria as determined by visualization of the amplicon on an agarose gel. When experimentally infected blood was analyzed, the detection limit was 10(3) bacteria. No visible amplicons were observed when 41 bacterial strains, representing 29 species other than C. burnetii, were tested. The presence of the DNA in all bacterial samples was confirmed by amplification of a 350-bp fragment of the 16S rDNA using two universal primers. The described method proved to be specific for C. burnetii and may become a rapid and sensitive diagnostic assay for C. burnetii. The results also demonstrate that the intervening sequence within the 23S rRNA gene is generally found among isolates of C. burnetii.

Maternal origin of inv dup(15) chromosomes in infantile autism

Six male patients with infantile autism and an extra inverted duplicated chromosome 15[inv dup(15)] were reported in a previous study. These patients had four copies of the chromosome region 15pter-q13, or an inv dup(15)(pter-->q13; q13-->pter). In this new study, DNA from the families of four of the patients were analysed using Southern based RFLPs and microsatellite polymorphisms from the region. In all four cases the inv dup(15) chromosome was of maternal origin. Furthermore, the data suggests that it originated in the maternal meiotic process rather than in an early mitosis in the developmental process of the embryo. The extra chromosome contained material from both of the maternally derived 15-chromosomes. Based on the molecular data presented here, a model for the origin of chromosome markers of this type is proposed.

Amplification and restriction endonuclease digestion of a large fragment of genes coding for rRNA as a rapid method for discrimination of closely related pathogenic bacteria

By use of primers specific to conserved regions of the rRNA gene cluster, a discrete amplicon of approximately 5 kb was amplified by PCR from all 21 bacterial genera investigated. Subsequent endonuclease digestion of the PCR product with HaeIII distinguished between the three species of the human pathogen Francisella spp. on the one hand and four clinically relevant genomic groups of Acinetobacter spp. on the other hand. The described technique has the potential as a rapid method for discriminating between closely related species that are of clinical importance.

Orchestration of the protective immune response to intracellular bacteria: Francisella tularensis as a model organism

Francisella tularensis is used as a model organism in studies of mechanisms behind the induction of a protective T-cell response in the mammalian host. Protective immunity is associated with a CD4 and CD8 T-cell response towards a mosaic of proteins of F. tularensis and due to HLA restriction, each individual selects her own mosaic. No single protein has so far been shown to be immunodominant. Only live F. tularensis affords effective host protection. Subcellular antigen preparations induce only a marginal protective response even when combined with potent adjuvants such as immunostimulating complexes (ISCOMs). In mice, intradermal injection of live F. tularensis but not of killed bacteria results in an early cytokine expression in the infected liver, including interleukin-12, tumor necrosis factor-alpha, and interferon-gamma. This cytokine response seems to be a prerequisite for effective priming of T cells to an array of proteins of F. tularensis to occur.

Cytokine expression in the liver of mice infected with a highly virulent strain of Francisella tularensis

Cytokine mRNA expression was determined in the liver of mice subcutaneously inoculated with a lethal dose of the highly virulent strain FSC 041 of Francisella tularensis subvar, tularensis or a sublethal dose of the live vaccine strain of F. tularensis subvar. palaearctica. Expression of mRNA for TNF-alpha, IL-12, IFN-gamma, and IL-10 was demonstrated within 48 h of inoculation, the kinetics being similar irrespective of bacterial strain used. Thus, the expression of a cytokine response believed to be important in the early host defence against live vaccine strain seemed insufficient to prevent the lethality of a more virulent strain.

Fixation of femoral neck fracture. A randomized 2-year follow-up study of hook pins and sliding screw plate in 222 patients

We compared fixation with hook pins or sliding screw plate in a prospective randomized study of 222 patients with a cervical hip fracture. Radiographic evidence of early redisplacement, nonunion, or late segmental collapse was found in 43 of 122 patients operated on with two hook pins and in 40 of 100 patients operated on with the sliding screw plate. According to the actuarial method, the failure rate after 2 years was 38% with hook pins and 46% with screw plates, which not is a significant difference. Due to early redisplacement, reoperation with an endoprosthesis was performed within 0.5 (2) years in 11 (22) patients in the hook-pin group and in 4 (17) patients in the sliding-screw plate group.

Adjuvanticity of ISCOMs incorporating a T cell-reactive lipoprotein of the facultative intracellular pathogen Francisella tularensis

Immunostimulating complexes (ISCOMs) are known to be highly effective adjuvants for envelope antigens of viral agents, but have not been evaluated for use with antigens of intracellular bacteria. Balb/c mice were subcutaneously immunized with ISCOMs into which the T cell-reactive membrane protein TUL4 of Francisella tularensis had been incorporated. Spleen cells from the immunized mice responded in vitro to TUL4 and to heat-killed F. tularensis live vaccine strain (LVS) with proliferation and production of gamma-interferon, whereas spleen cells from control mice immunized with TUL4 only did not respond to the antigens. When mice immunized with TUL4 ISCOMs were challenged with F. tularensis LVS, bacterial counts in spleen and liver were lower than in non-immunized mice. Again, TUL4 had no effect when used without ISCOMs. When proteins of a total membrane preparation of F. tularensis LVS were incorporated in ISCOMs and used for immunization, a decrease in bacterial counts was obtained which was similar in magnitude to that of TUL4 ISCOMs. Generally, the adjuvant effects demonstrated did not compare with the excellent protective effect of live tularaemia vaccine. Nonetheless, ISCOMs provide a means whereby protective antigens of F. tularensis can be tested.

Cytokine expression in the liver during the early phase of murine tularemia

Cytokine expression was determined in the livers of mice inoculated subcutaneously with Francisella tularensis LVS. During the first 48 h of infection, there was a logarithmic increase of bacteria in the liver, with a doubling time of 2.5 h. Within 48 h, tumor necrosis factor alpha (TNF-alpha), interleukin 10 (IL-10), IL-12, and gamma interferon (IFN-gamma) mRNAs were expressed, and production of TNF-alpha and IFN-gamma was demonstrated. There was no expression within 96 h of mRNA from IL-2, IL-3, or IL-4. After subcutaneous inoculation of heat-killed LVS, no expression of any of the cytokine mRNAs and no increase in the levels of TNF-alpha or IFN-gamma occurred. The expression of TNF-alpha, IL-12, and IFN-gamma is held to be important to evoke an early T-cell-independent host defense against F. tularensis as well as to drive the expansion of a protective Th1 cell response.

CD4+ and CD8+ T-cell-dependent and -independent host defense mechanisms can operate to control and resolve primary and secondary Francisella tularensis LVS infection in mice

Immunity to experimental infection with the facultative intracellular bacterium Francisella tularensis is generally considered an example of T-cell-mediated, macrophage-expressed immunity. However, the results of the present study indicate that T-cell-independent mechanisms are also important in anti-Francisella defense. They show that mice selectively depleted of CD4+, CD8+, or both T-cell populations by treatment with T-cell subset-specific monoclonal antibodies remained capable of controlling and partly resolving a primary sublethal Francisella infection. Similarly, it was found that Francisella-immune mice depleted of either or both subsets of T cells retain a high degree of acquired immunity to reinfection. Together, these findings imply that resistance to primary and secondary tularemia can be mediated by cells other than CD4+ and CD8+ T cells.

Persistence of cell-mediated immunity and decline of humoral immunity to the intracellular bacterium Francisella tularensis 25 years after natural infection

The humoral and cell-mediated immune responses to the facultative intracellular pathogen Francisella tularensis were studied in subjects who had tularemia 25 years earlier. Serum agglutinin titers were low. Of 53 subjects, only 2 had a titer > 40. The F. tularensis-induced T cell response, on the other hand, was vigorous and in fact similar in magnitude to the response to purified protein derivative (PPD) of Mycobacterium tuberculosis. T cells from 44 of 52 subjects showed a significant (P < .05) proliferative response in vitro to each of four membrane proteins of F. tularensis. Only 2 subjects did not respond to any of the proteins. In most cultures from 18 subjects tested, interferon-gamma was produced in response to the proteins. During the last 25 years, tularemia has been reported only rarely in the region where the subjects lived, suggesting that an antigen-specific T cell response may persist after tularemia independently of reexposure to F. tularensis.

Neutrophils are critical for host defense against primary infection with the facultative intracellular bacterium Francisella tularensis in mice and participate in defense against reinfection

It is generally believed that immunity to experimental infection with the facultative intracellular bacterium Francisella tularensis is an example of T-cell-mediated immunity that is expressed by activated macrophages and mediated by Francisella-specific T cells. According to the results presented herein, neutrophils are also essential for defense against primary infection with this organism. It is shown that mice depleted of neutrophils by treatment with the granulocyte-specific monoclonal antibody RB6-8C5 are rendered defenseless against otherwise sublethal doses of F. tularensis LVS inoculated intravenously or intradermally. In neutrophil-depleted mice, the organism grew progressively in the livers, spleens, and lungs to reach lethal numbers, whereas infection was resolved in normal mice. Although neutrophils were found to resistance to reinfection, their participation was less important. The results suggest that neutrophils are needed for defense against primary infection because they serve to restrict the growth of F. tularensis before it reaches numbers capable of overwhelming a developing specific immune response. The exact way that neutrophils achieve this is not clear at this time, although it is probable that they contribute in ways other than by ingesting and killing the bacterium.

Bone mineral content and fixation strength of femoral neck fractures. A cadaver study

We measured the bone mineral content (BMC) of 21 human femoral autopsy specimens using Radiographic Attenuation Technique (RAT). The specimens were then tested for stiffness in a material-testing machine. Osteosynthesis was performed after medial femoral neck osteotomy, using 1 of 3 different pinning methods: 2 hook pins (LIH), 2 cannulated screws (Uppsala), and 3 cannulated screws (CHP). The specimens were allocated to each method by grouping them in triplets with similar BMC. Cyclic loading at 500-1000 N and 1 Hz was performed during 50 minutes. The amount of axial compression during loading was measured. Finally, loading to failure was done and post-fixation stiffness and ultimate compression strength recorded. With one exception, all cases failed where the BMC was less than 0.4 g/cm2. No differences between the methods of osteosynthesis were found. The fixation strength was mostly dependent on the strength of the bone, i.e., the degree of osteoporosis.

Analysis of 16S ribosomal DNA sequences of Francisella strains and utilization for determination of the phylogeny of the genus and for identification of strains by PCR

The 16S ribosomal DNAs (rDNAs) of two strains of Francisella tularensis and one strain of Francisella philomiragia were sequenced. On the basis of phylogenetic analysis data, the genus Francisella was placed in the gamma subclass of the Proteobacteria. The most closely related organism was the intracellular bacterium Wolbachia persica. The sequenced 16S rDNA molecules of the Francisella species exhibited very high levels of similarity (98.5 to 99.9%). Two variable regions, comprising 390 to 450 nucleotides of the 16S rDNA molecules of 17 additional Francisella strains, including members of the species F. tularensis and F. philomiragia, were also sequenced. At most, six nucleotide differences were observed among the sequences of the F. tularensis strains. The sequence of Francisella novicida was virtually identical to the sequences of the F. tularensis strains, thereby supporting the hypothesis that these organisms are members of the same species. On the basis of the observed differences, primer pairs were designed to distinguish strains by using the PCR at the genus, species, and subspecies levels. This permitted sensitive identification of strains belonging to the genus Francisella and discrimination of the species F. tularensis and F. philomiragia.

Increased synthesis of DnaK, GroEL, and GroES homologs by Francisella tularensis LVS in response to heat and hydrogen peroxide

The response of the facultative intracellular bacterium Francisella tularensis LVS to stress was assayed by pulse-labeling with [35S]methionine followed by two-dimensional gel electrophoresis and autoradiography. A temperature increase from 37 to 42 degrees C or exposure to 5 mM hydrogen peroxide induced increased syntheses of at least 15 proteins. Among these proteins were a 75-, a 60-, and a 10-kDa protein. By N-terminal sequence analysis, these three proteins were found to be extensively homologous to the highly conserved chaperone proteins DnaK, GroEL, and GroES of Escherichia coli. Antibodies specific to the DnaK homolog of E. coli reacted with the 75-kDa protein, and antibodies to the GroEL homolog of Legionella micdadei reacted with the 60-kDa protein. A readiness to respond to hydrogen peroxide with synthesis of the chaperone components may be fundamental to the intracellular survival of pathogens such as F. tularensis, which are exposed to oxidative stress while invading the host macrophages.

Immunogenicity and toxicity of lipopolysaccharide from Francisella tularensis LVS

Lipopolysaccharide (LPS) from the live vaccine strain of Francisella tularensis (F. tularensis LVS) was isolated and purified. The LPS did not stimulate lymphocytes from previously tularaemia-vaccinated individuals or lymphocytes from non-primed individuals. However, serum antibodies from tularaemia vaccinees reacted with the LPS whereas virtually no reactivity was found with antibodies from individuals not exposed to F. tularensis LVS. Antibodies of immunoglobulin class M displayed the antibody reactivity predominantly. The LPS failed to induce the mononuclear cell-derived cytokine interleukin-1 and only low levels of tumour necrosis factor were detected. Furthermore, no LPS endotoxin properties were found in galactosamine-treated mice or in the Limulus amoebocyte lysate assay. From these results it can be concluded that F. tularensis LVS possesses a lipopolysaccharide-like molecule, which does not exhibit properties of a classical endotoxin.

The 17 kDa lipoprotein and encoding gene of Francisella tularensis LVS are conserved in strains of Francisella tularensis

A T-cell-stimulating 17 kDa protein of the vaccine strain Francisella tularensis LVS has previously been cloned, sequenced and shown to be a lipoprotein. In the present study, it was investigated whether the protein, denoted TUL4, and its gene are present in various strains of the genus Francisella. By Western blot analysis, it was demonstrated that a TUL4-specific monoclonal antibody bound to a protein present in each of the Francisella strains. The immunoreactive proteins had an M(r) of 17 kDa in all F. tularensis strains and in the strain Francisella novicida, whereas the M(r) in strains of Francisella philomiragia was 20 kDa. When genomic preparations were probed with a radioactive DNA fragment of F. tularensis LVS encoding TUL4, hybridization was demonstrated in all strains of Francisella, although the F. philomiragia strains did not hybridize under conditions of high stringency. The hybridizing chromosomal DNA fragment of the F. philomiragia strains was larger than that of the other Francisella strains. No hybridization or Western blot reactivity was seen when various other Gram-negative and Gram-positive bacteria were probed. In summary, the 17 kDa lipoprotein of F. tularensis LVS appears to be Francisella-specific and present in the species F. tularensis and F. novicida, whereas an immunologically related protein is present in F. philomiragia.

Various membrane proteins of Francisella tularensis induce interferon-gamma production in both CD4+ and CD8+ T cells of primed humans

Tularaemia is an intracellular infection, which is controlled by the host as a result of an immunospecific T-cell response. A crucial product of the responding T cells is interferon-gamma (IFN-gamma), which acts by enhancing the microbicidal activity of macrophages. T cells of tularaemia-vaccinated individuals respond in vitro to a multitude of protein antigens of the vaccine strain Francisella tularensis LVS. In the present study, the responses to four of these antigens were shown to be confined mostly to the CD45RO+ memory T-cell subset. To characterize further the phenotype of the responding cells, purified CD4+ and CD8+ T cells were stimulated with the antigens. CD4+ T cells, but not CD8+ T cells, proliferated and produced IFN-gamma. However, when CD8+ T cells were isolated from bulk cultures of lymphocytes, which had been stimulated with antigen for 3 days, they responded to an extent similar to that of CD4+ T cells. Purified CD8+ T cells also responded when they were supplemented with interleukin-2 (IL-2). There was a direct quantitative correlation between the proliferative response of CD4+ and CD8+ T cells and their production of IFN-gamma. IL-2 was produced in the cultures, the amounts being higher in the cultures of CD4+ than in those of CD8+ cells. IL-4 was not detected in the culture medium of any of the T-cell subsets. Seventeen human alpha beta + CD4+ CD8- CD3+ T-cell clones, specific to antigens of F. tularensis, were raised. When proliferating, these clones did invariably produce IL-2 and IFN-gamma but no IL-4. In conclusion, both CD4+ and CD8+ T cells of tularaemia-vaccinated individuals respond with proliferation to various protein antigens of F. tularensis, and the proliferative response is strictly associated with IFN-gamma production. The CD8+ T-cell response seems to depend on cytokines supplied by proliferating CD4+ T cells.

Humoral and cell-mediated immunity in mice to a 17-kilodalton lipoprotein of Francisella tularensis expressed by Salmonella typhimurium

A 17-kDa lipoprotein, TUL4, of the facultative intracellular bacterium Francisella tularensis is one of several membrane proteins that induce an in vitro response in T cells from F. tularensis-primed humans. A DNA fragment of the live vaccine strain F. tularensis LVS encoding TUL4 was cloned into Salmonella typhimurium chi 4072, an attenuated delta cya delta crp mutant. Expression of the protein by the recombinant S. typhimurium chi 4072 (pTUL4-15) was maintained after passage in BALB/cJ mice. When mice were immunized with S. typhimurium chi 4072(pTUL4-15), some animals showed an antibody response and a T-cell response to TUL4. When the immunized mice were challenged with the live vaccine strain F. tularensis LVS, bacterial counts in the liver and spleen were lower than in animals immunized with S. typhimurium chi 4072. Immunization with F. tularensis LVS caused a much stronger protection against the challenge than did immunization with S. typhimurium chi 4072(pTUL4-15). The present study demonstrated that the 17-kDa lipoprotein TUL4 of F. tularensis is involved in a protective immunity to tularemia. Possibly, several T-cell-reactive proteins of the organism have to contribute for optimal protection to be achieved.