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1.  Clinical and Serological Follow-Up of Patients with Human Granulocytic Ehrlichiosis in Slovenia 
An evaluation of the clinical outcome and the duration of the antibody response of patients with human granulocytic ehrlichiosis (HGE) was undertaken in Slovenia. Adult patients with a febrile illness occurring within 6 weeks of a tick bite were classified as having probable or confirmed HGE based on the outcome of serological or PCR testing. Thirty patients (median age, 44 years) were enrolled, and clinical evaluations and serum collection were undertaken at initial presentation and at 14 days, 6 to 8 weeks, and 3 to 4, 6, 12, 18, and 24 months. An indirect immunofluorescence assay (IFA) was performed, and reciprocal titers of ≥128 were interpreted as positive. Patients presented a median of 4 days after the onset of fever and were febrile for a median of 7.5 days; four (13.3%) received doxycycline. Seroconversion was observed in 3 of 30 (10.0%) patients, and 25 (83.3%) showed >4-fold change in antibody titer. PCR results were positive in 2 of 3 (66.7%) seronegative patients but in none of 27 seropositive patients at the first presentation. IFA antibody titers of ≥128 were found in 14 of 29 (48.3%), 17 of 30 (56.7%), 13 of 30 (43.4%), and 12 of 30 (40.0%) patients 6, 12, 18, and 24 months after presentation, respectively. Patients reporting additional tick bites during the study had significantly higher antibody titers at most time points during follow-up. No long-term clinical consequences were found during follow-up.
doi:10.1128/CDLI.8.5.899-903.2001
PMCID: PMC96168  PMID: 11527800
2.  Identity of Ehrlichial DNA Sequences Derived from Ixodes ricinus Ticks with Those Obtained from Patients with Human Granulocytic Ehrlichiosis in Slovenia 
Journal of Clinical Microbiology  1999;37(1):209-210.
Adult Ixodes ricinus (Acari: Ixodidae) ticks collected near Ljubljana, Slovenia, were tested for the agent of human granulocytic ehrlichiosis (HGE) by using PCR assays based on the 16S rRNA gene. Three (3.2%) of 93 ticks were found to contain granulocytic ehrlichiae. Nucleotide sequences of portions of the bacterial groESL heat shock operon amplified from these ticks were identical or nearly (99.8%) identical to those previously determined for human patients with HGE from Slovenia, providing additional evidence that the ticks were infected with the HGE agent. This study identified I. ricinus as the likely vector for these ehrlichial pathogens of humans in this part of Europe.
PMCID: PMC84210  PMID: 9854093
3.  Isolation and characterization of Ehrlichia chaffeensis strains from patients with fatal ehrlichiosis. 
Journal of Clinical Microbiology  1997;35(10):2496-2502.
Two new isolates of Ehrlichia chaffeensis (designated Jax and St. Vincent) were obtained from patients with fatal ehrlichial infections. Patients developed characteristic manifestations of severe disease due to E. chaffeensis, including marked thrombocytopenia, pulmonary insufficiency, and encephalopathy. Primary isolation was achieved in DH82 cells; the Jax and St. Vincent isolates were detected within 19 and 8 days postinoculation, respectively. The isolates were characterized by molecular evaluation of the 16S rRNA gene, the groESL heat shock operon, a 120-kDa immunodominant protein gene, and an incompletely characterized repetitive-motif sequence (variable-length PCR target [VLPT]). The sequences were compared with those of the corresponding molecular regions in the type isolate (Arkansas). St. Vincent contained one fewer repeat unit in both the 120-kDa protein gene and the VLPT compared with corresponding sequences of the Jax and Arkansas isolates. 16S rRNA gene sequences from the two new isolates had 100% identity to the corresponding sequences of the 91HE17 and Sapulpa isolates of E. chaffeensis, and to the corrected 16S rRNA gene sequence of the Arkansas isolate. The Jax isolate grew more slowly than the St. Vincent isolate in DH82 cells, and both of the new isolates grew more slowly than the extensively passaged Arkansas isolate. Although specific associations between ehrlichial pathogenicity and genotype were not identified from these comparisons, recovery of this organism from a spectrum of clinical presentations remains an integral step in understanding mechanisms of disease caused by E. chaffeensis.
PMCID: PMC229999  PMID: 9316896
4.  PCR amplification and comparison of nucleotide sequences from the groESL heat shock operon of Ehrlichia species. 
Journal of Clinical Microbiology  1997;35(8):2087-2092.
Degenerate PCR primers derived from conserved regions of the eubacterial groESL heat shock operon were used to amplify groESL sequences of Ehrlichia equi, Ehrlichia phagocytophila, the agent of human granulocytic ehrlichiosis (HGE), Ehrlichia canis, Bartonella henselae, and Rickettsia rickettsii. The groESL nucleotide sequences were less conserved than the previously determined 16S rRNA gene sequences of these bacteria. A phylogenetic tree derived from deduced GroEL amino acid sequences was similar to trees based on 16S rRNA gene sequences. Nucleotide sequences obtained from clinical samples containing E. equi, E. phagocytophila, or the HGE agent were very similar (99.9 to 99.0% identity), and the deduced amino acid sequences were identical. Some divergence was evident between nucleotide sequences amplified from samples originating from the United States (E. equi and the HGE agent) and sequences from the European species, E. phagocytophila. A single pair of PCR primers derived from these sequences was used to detect E. chaffeensis and HGE agent DNA in blood samples from human patients with ehrlichiosis.
PMCID: PMC229908  PMID: 9230387
5.  An indirect immunofluorescence assay using a cell culture-derived antigen for detection of antibodies to the agent of human granulocytic ehrlichiosis. 
Journal of Clinical Microbiology  1997;35(6):1510-1516.
An indirect immunofluorescence assay for the detection of human antibodies to the agent of human granulocytic ehrlichiosis (HGE) was developed and standardized. Antigen was prepared from a human promyelocytic leukemia cell line (HL-60) infected with a tick-derived isolate of the HGE agent (USG3). Suitable antigen presentation and preservation of cellular morphology were obtained when infected cells were applied and cultured on the slide, excess medium was removed, and cells were fixed with acetone. Use of a buffer containing bovine serum albumin and goat serum reduced background fluorescence, and use of an immunoglobulin G (gamma-specific) conjugate reduced nonspecific binding. The assay readily detected specific antibody from HGE patients and did not detect antibody from healthy individuals. No significant reactivity was noted in sera from patients with high titers of antibodies to other rickettsial species. We were able to identify antibodies reactive to USG3 antigen in samples from areas where HGE is endemic that had tested negative to other rickettsial agents. Animal sera reactive against Ehrlichia equi or Ehrlichia phagocytophila bound to the HGE antigen, indicating that the assay may be useful for veterinary use. Comparability between two different laboratories was assessed by using coded human sera exchanged between laboratories. Results from the two laboratories were similar, indicating that the assay can be easily integrated into use for routine testing for HGE. The assay was then compared to an assay using horse neutrophils infected with ehrlichiae. The two assays gave comparable results, indicating that the cell culture-derived antigen can be used for testing samples that have been previously tested with E. equi as an antigen. The new assay offers several advantages over other immunofluorescence methods that use animal-derived antigen and is suitable for use in testing for human antibodies to the HGE agent.
PMCID: PMC229776  PMID: 9163471
6.  Serologic and molecular detection of granulocytic ehrlichiosis in Rhode Island. 
Journal of Clinical Microbiology  1997;35(4):944-947.
A new indirect fluorescent-antibody (IFA) assay with antigen produced in vitro in the human promyelocytic leukemia cell line HL60 was used to identify the first recognized case of human granulocytic ehrlichiosis in Rhode Island. This IFA assay was used to detect granulocytic ehrlichiae in white-footed mice and in a dog inhabiting the area surrounding the patient's residence. Host-seeking Ixodes scapularis ticks found in the same habitat also were infected. I. scapularis ticks collected from other locations were fed on dogs and New Zealand White rabbits to assess the competency of these species as hosts of granulocytotropic Ehrlichia. Tick-induced infections of dogs were confirmed by serologic testing, tissue culture isolation, and PCR amplification, whereas several rabbits seroconverted but were PCR and culture negative. PCR amplification of the 16S rRNA gene and DNA sequencing of the PCR products or culture isolation was used to confirm granulocytic Ehrlichia infections in humans, dogs, white-footed mice, and ticks.
PMCID: PMC229705  PMID: 9157157
7.  Enzyme immunoassay for rabies antibody in hybridoma culture fluids and its application to differentiation of street and laboratory strains of rabies virus. 
Journal of Clinical Microbiology  1984;19(2):267-272.
A rapid and sensitive enzyme immunoassay is described for detecting rabies antibody in hybridoma culture fluids. Glass fiber filter disks were used to immobilize gamma-irradiated mouse neuroblastoma cells infected with street or laboratory strains of rabies virus. Bound rabies-specific antibody was detected by reaction with horseradish peroxidase-labeled goat anti-mouse immunoglobulin G. The assay was performed in a 96-well filtration device developed by Cleveland et al. (J. Clin. Microbiol. 15:402-407, 1982) for the typing of herpes simplex viruses. When partially disrupted cells were used, both internal and external viral antigens were available for reaction. The procedure is rapid (less than 4 h for completion) and requires only small amounts of fluid, and the gamma-irradiated antigen is noninfectious. When the procedure was used to screen 145 fluids from rabies-immune spleen-myeloma cell fusions, 132 were positive for rabies antibody. Other commonly used assays for the detection of rabies-specific antibody were less sensitive. Simultaneous analyses of many hybridoma fluids against a battery of street and laboratory strains of rabies virus are possible and allow rapid selection of useful monoclones.
PMCID: PMC271035  PMID: 6365963
8.  Ehrlichia chaffeensis expresses an immunoreactive protein homologous to the Escherichia coli GroEL protein. 
Infection and Immunity  1993;61(8):3536-3539.
A clone expressing a 58-kDa protein reactive with human convalescent-phase serum was isolated from a recombinant library of Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis. Sequencing identified two open reading frames, one encoding a 10.3-kDa polypeptide consisting of 94 amino acids and another encoding a 58-kDa polypeptide consisting of 550 amino acids. The sequences of the 10.3- and 58-kDa polypeptides were homologous to those of the Escherichia coli GroES and GroEL heat shock proteins, respectively.
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PMCID: PMC281035  PMID: 8101510
9.  Sickness and recovery of dogs challenged with a street rabies virus after vaccination with a vaccinia virus recombinant expressing rabies virus N protein. 
Journal of Virology  1992;66(5):2601-2604.
Dogs were vaccinated intradermally with vaccinia virus recombinants expressing the rabies virus glycoprotein (G protein) or nucleoprotein (N protein) or a combination of both proteins. The dogs vaccinated with either the G or G plus N proteins developed virus-neutralizing antibody titers, whereas those vaccinated with only the N protein did not. All dogs were then challenged with a lethal dose of a street rabies virus, which killed all control dogs. Dogs vaccinated with the G or G plus N proteins were protected. Five (71%) of seven dogs vaccinated with the N protein sickened, with incubation periods 3 to 7 days shorter than that of the control dogs; however, three (60%) of the five rabid dogs recovered without supportive treatment. Thus, five (71%) of seven vaccinated with the rabies N protein were protected against a street rabies challenge. Our data indicate that rabies virus N protein may be involved in reducing the incubation period in dogs primed with rabies virus N protein and then challenged with a street rabies virus and, of more importance, in subsequent sickness and recovery.
PMCID: PMC241012  PMID: 1560518
10.  Detection of the etiologic agent of human ehrlichiosis by polymerase chain reaction. 
Journal of Clinical Microbiology  1992;30(4):775-780.
Polymerase chain reaction (PCR) primers derived from a variable region of the 16S rRNA gene sequence were used to amplify DNA specifically from Ehrlichia chaffeensis (the recently proposed name for the etiologic agent of human ehrlichiosis). The 389-bp product defined by the specific primers was not detected when DNA samples from any of the other recognized species of Ehrlichia were used as amplification templates. When the PCR was applied to five suitable blood specimens obtained from patients subsequently shown to be serologically positive for E. chaffeensis, all five were positive. The same technique was applied to a total of six control blood specimens, three from febrile patients who had no serologic evidence of infection with Ehrlichia or Rickettsia species and three from patients diagnosed with Rocky Mountain spotted fever, and all six were negative. A chemiluminescent, group-specific oligonucleotide probe was shown to hybridize only with the PCR products obtained upon amplification of the five blood specimens from patients serologically diagnosed as having human ehrlichiosis. The results indicate that PCR, coupled with a nonisotopic method of confirming the identity of the PCR product, is a highly specific and efficient method of detecting the agent of human ehrlichiosis in blood. The results also suggest that E. chaffeensis is the sole etiologic agent of human ehrlichiosis in the United States. The technique was also applied to four ticks that were positive by direct immunofluorescence for Ehrlichia species, and one tick was PCR positive, indicating that E. chaffeensis DNA can be detected in ticks harboring this organism, although the sensitivity may be low.
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PMCID: PMC265160  PMID: 1374076
11.  Raccoon poxvirus recombinants expressing the rabies virus nucleoprotein protect mice against lethal rabies virus infection. 
Journal of Virology  1991;65(6):3400-3405.
Raccoon poxvirus (RCN) recombinants expressing the rabies virus internal structural nucleoprotein (RCN-N) protected A/WySnJ mice against a lethal challenge with street rabies virus (SRV). Maximum survival was achieved following vaccination by tail scratch and footpad (FP) SRV challenge. RCN-N-vaccinated mice inoculated in the FP with SRV were resistant to infection for at least 54 weeks postvaccination. Protection was also elicited by RCN recombinants expressing the rabies virus glycoprotein (RCN-G). Vaccination with RCN-G evoked rabies virus neutralizing antibody. Rabies virus neutralizing antibody was not detected in RCN-N-vaccinated mice prior to or following SRV infection. Radioimmunoprecipitation assays showed that sera from RCN-N-vaccinated mice which survived SRV infection did not contain antibody to SRV structural protein G, M, or NS. The mechanism(s) of N-induced resistance appears to correlate with the failure of peripherally inoculated SRV to enter the central nervous system (CNS). Support for this correlation with resistance was documented by the observations that SRV-inoculated RCN-N-vaccinated mice did not develop clinical signs of CNS rabies virus infection, infectious SRV was not detected in the spinal cord or brain following FP challenge, and all RCN-N-vaccinated mice died following direct intracranial infection of the CNS with SRV. These results suggest that factors other than anti-G neutralizing antibody are important in resistance to rabies virus and that the N protein should be considered for incorporation with the G protein in recombinant vaccines.
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PMCID: PMC241005  PMID: 2033678
12.  Rabies diagnostic reagents prepared from a rabies N gene recombinant expressed in baculovirus. 
Journal of Clinical Microbiology  1990;28(5):858-863.
A gene encoding the nucleoprotein (N) of rabies virus was inserted into the genome of the baculovirus Autographa californica nuclear polyhedrosis virus. Recombinant gene expression was controlled by the strong polyhedrin gene promoter. Insect cells (Spodoptera frugiperda) infected by a baculovirus recombinant containing the rabies virus N gene produced abundant amounts of a novel 55-kilodalton protein of a size comparable to that of the rabies virus N protein, as demonstrated by polyacrylamide gel electrophoresis. This new gene product possessed the antigenic and immunogenic properties of native viral N protein, as shown by the ability of the new protein to react in immunoprecipitation and immunofluorescence assays with antirabies antibodies, to serve as a substitute for infectious rabies virus in adsorbing suspensions for diagnostic tests, and to induce high-titered antiserum. The baculovirus expression system provides a safe, convenient, and inexpensive source of rabies virus N protein for the production of both antiserum and adsorbing suspensions for use in rabies diagnoses.
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PMCID: PMC267824  PMID: 2191008
13.  Microneutralization test for rabies virus based on an enzyme immunoassay. 
Journal of Clinical Microbiology  1987;25(12):2440-2442.
We have developed an enzyme immunoassay for rabies virus by using acetone-fixed infected cell cultures as the antigen. This test was used to demonstrate virus-neutralizing antibodies in human and animal sera and was as sensitive as and easier to perform than the rapid fluorescent-focus inhibition technique.
PMCID: PMC269515  PMID: 3323234
14.  Isolation of Legionella spp. from environmental water samples by low-pH treatment and use of a selective medium. 
Journal of Clinical Microbiology  1981;13(4):714-719.
A selective medium was developed and used successfully to isolate Legionella pneumophila and Legionella-like organisms from environmental specimens previously positive by animal inoculation methods. This medium consists of charcoal-yeast extract agar to which have been added cephalothin (4 micrograms/ml), colistin (16 micrograms/ml), vancomycin (0.5 microgram/ml), and cycloheximide (80 micrograms/ml). Pretreating of the environmental water samples with an acid buffer (pH 2.2), followed by plating on the selective medium, improved the rate of recovery of both Legionella and Legionella-like organisms relative to that with direct plating on selective media.
PMCID: PMC273865  PMID: 7229015

Results 1-14 (14)