Human hepatitis B virus polymerase interacts with the molecular chaperonin Hsp60

Previous studies showed that hepatitis B virus polymerase (HBV Pol) interacts with host factors such as the Hsp90 complex, which is a critical step in viral genome replication. In this report, we propose that another chaperone, Hsp60, interacts with human HBV Pol and that this is a very important step for maturation of human HBV Pol into the active state. In the immunoprecipitation of recombinant human HBV Pol expressed in insect cells with the recombinant baculovirus expression system, the 60-kDa protein was coimmunoprecipitated with Pol and the protein was identified as Hsp60 through peptide sequencing and immunogenic analysis with an anti-Hsp60 antibody. In vitro experiments showed that Hsp60 strongly affected human HBV Pol activity in that (i) blocking of Hsp60 by the protein-specific antibody reduced human HBV Pol activity, (ii) the activity was increased by addition of Hsp60 in the presence of ATP, and (iii) ATP synergistically activated human HBV Pol with Hsp60. In vivo experiments showed that inhibition of Hsp60 in cells by a mutant Hsp60, C Delta 540, resulted in the reduction of human HBV Pol activity. In summary, our results indicate that the interaction is significant for conversion of human HBV Pol into the active state.

A cofactor of tRNA synthetase, p43, is secreted to up-regulate proinflammatory genes

An auxiliary factor of mammalian multi-aminoacyl-tRNA synthetases, p43, is thought to be a precursor of endothelial monocyte-activating polypeptide II (EMAP II) that triggers proinflammation in leukocytes and macrophages. In the present work, however, we have shown that p43 itself is specifically secreted from intact mammalian cells, while EMAP II is released only when the cells are disrupted. Secretion of p43 was also observed when its expression was increased. These results suggest that p43 itself should be a real cytokine secreted by an active mechanism. To determine the cytokine activity and active domain of p43, we investigated tumor necrosis factor (TNF) and interleukin-8 (IL-8) production from human monocytic THP-1 cells treated with various p43 deletion mutants. The full length of p43 showed higher cytokine activity than EMAP II, further supporting p43 as the active cytokine. p43 was also shown to activate MAPKs and NFkappaB, and to induce cytokines and chemokines such as TNF, IL-8, MCP-1, MIP-1alpha, MIP-1beta, MIP-2alpha, IL-1beta, and RANTES. Interestingly, the high level of p43 was observed in the foam cells of atherosclerotic lesions. Therefore, p43 could be a novel mediator of atherosclerosis development as well as other inflammation-related diseases.

Molecular characterization of the cDNA encoding an acidic isoform of PR-1 protein in rice

Rice cDNA encoding an acidic type of pathogenesis-related protein-1 (PR-1a) was cloned and characterized. The deduced PR-1a protein consisted of 168 amino acid residues, including 24 hydrophobic signal sequences at the N-terminus. The predicted molecular mass of the PR-1a was 15,728 Da with a theoretical pI of 4.5, an indication of an acidic protein. The PR-la showed high homology to an acidic PR-1 of Zea mays (74%) and a previously identified basic type PR-1 of rice (64%). Both rice PR-1 and PR-1a genes were found to exist as small gene families through Southern blot hybridization analyses. The PR-1 mRNA was accumulated only in leaves, while the PR-1a transcript was accumulated throughout the plant at a low level. Expression of both PR-1 genes was induced by infections of the rice blast fungus, Magnaporthe grisea, or the bacterial leaf blight pathogen, Xanthomonas oryzae pv. oryzae, and the treatment of benzo (1, 2, 3) thiadiazole-7-carbothioic acid S-ethyl ester, H2O2, or CuSO4. The expression of both PR-1 genes was higher and more rapidly induced in an incompatible interaction than in a compatible interaction in the rice M. grisea interactions.

Heat shock protein 90 mediates protein-protein interactions between human aminoacyl-tRNA synthetases

Heat shock protein 90 (hsp90) is a molecular chaperone responsible for protein folding and maturation in vivo. Interaction of hsp90 with human glutamyl-prolyl-tRNA synthetase (EPRS) was found by genetic screening, co-immunoprecipitation, and in vitro binding experiments. This interaction was sensitive to the hsp90 inhibitor, geldanamycin, and also ATP, suggesting that the chaperone activity of hsp90 is required for interaction with EPRS. Interaction of EPRS with hsp90 was targeted to the region of three tandem repeats linking the two catalytic domains of EPRS that is also responsible for the interaction with isoleucyl-tRNA synthetase (IRS). Interaction of EPRS and IRS also depended on the activity of hsp90, implying that their association was mediated by hsp90. EPRS and IRS form a macromolecular protein complex with at least six other tRNA synthetases and three cofactors. hsp90 preferentially binds to most of the complex-forming enzymes rather than those that are not found in the complex. In addition, inactivation of hsp90 interfered with the in vivo incorporation of the nascent aminoacyl-tRNA synthetases into the multi-ARS complex. Thus, hsp90 appears to mediate protein-protein interactions of mammalian tRNA synthetases.

Affinity maturation of natural antibody using a chain shuffling technique and the expression of recombinant antibodies in Escherichia coli

The affinity of natural antibody (Ka = 8 x 10(6) M(-1)) recognizing preS1 of hepatitis B virus (HBV) was improved by replacing the heavy (H) chain gene with repertoires of VH genes, obtained from two nonimmunized donors. Two separate clones, 1C2 and 1E4, showed affinities of 2.3 x 10(7) and 5.2 x 10(7) M(-1), which were increased by factors of 2.8 and 6.5, respectively, compared to the parental clone. Recombinant scFvs (rscFvs) were expressed as fusion protein with minor coat protein, pIII, and secreted into medium after 3 h of induction with 1 mM IPTG. The expression level of functional rscFv capable of binding to preS1 reached a peak after 6-10 h (1C2) and 8-10 h (1E4) of IPTG induction, and afterwards decreased gradually. In order to achieve the overexpression of rscFv in E. coli, gene encoding scFv of 1C2 or 1E4 was inserted into pRSET vector. RscFvs were overexpressed as cytoplasmic inclusion bodies in E. coli BL 21 strain, which were denatured and carefully refolded using a continuous dialysis system. The purified recombinant fragments were pure when analyzed by SDS-PAGE and had the predicted size of 34 kDa. Clone 1E4 used the heavy chain gene belonging to family VII and subgroup III. Chain shuffling offers an alternative to random point mutation for affinity maturation of human antibody in vitro.

Catalytic peptide of human glutaminyl-tRNA synthetase is essential for its assembly to the aminoacyl-tRNA synthetase complex

Human glutaminyl-tRNA synthetase (QRS) is one of several mammalian aminoacyl-tRNA synthetases (ARSs) that form a macromolecular protein complex. To understand the mechanism of QRS targeting to the multi-ARS complex, we analyzed both exogenous and endogenous QRSs by immunoprecipitation after overexpression of various Myc-tagged QRS mutants in human embryonic kidney 293 cells. Whereas a deletion mutant containing only the catalytic domain (QRS-C) was targeted to the multi-ARS complex, a mutant QRS containing only the N-terminal appended domain (QRS-N) was not. Deletion mapping showed that the ATP-binding Rossman fold was necessary for targeting of QRS to the multi-ARS complex. Furthermore, exogenous Myc-tagged QRS-C was co-immunoprecipitated with endogenous QRS. Since glutaminylation of tRNA was dramatically increased in cells transfected with the full-length QRS, but not with either QRS-C or QRS-N, both the QRS catalytic domain and the N-terminal appended domain were required for full aminoacylation activity. When QRS-C was overexpressed, arginyl-tRNA synthetase and p43 were released from the multi-ARS complex along with endogenous QRS, suggesting that the N-terminal appendix of QRS is required to keep arginyl-tRNA synthetase and p43 within the complex. Thus, the eukaryote-specific N-terminal appendix of QRS appears to stabilize the association of other components in the multi-ARS complex, whereas the C-terminal catalytic domain is necessary for QRS association with the multi-ARS complex.

Localization of HSP90 binding sites in the human hepatitis B virus polymerase

The fact that HSP90 proteins and their chaperonin partners play an important role in epsilon RNA binding of duck HBV Pol protein during duck HBV replication has been reported. To elucidate the molecular basis of HBV Pol/HSP90 interaction, we have characterized the HSP90 interaction to HBV Pol. We found that human HBV Pol protein upon synthesis in rabbit reticulocyte lysate formed a complex with HSP90 in vitro as duck HBV Pol did. In addition, HSP90 protein was copurified with MBP/POL protein expressed in HepG2 cells, suggesting that human HBV Pol protein is associated with HSP90 in vivo. To localize the HSP90 interaction site region, several deletion mutants of HBV Pol translated in vitro were immunoprecipitated with anti-HSP90 antibody. The result indicates that C-terminal regions of the TP and RT domains interact with HSP90 independently.

Distinct physiological functions of thiol peroxidase isoenzymes in Saccharomyces cerevisiae

A new type of peroxidase ("thiol peroxidase"; TPx) having cysteine as the primary site of catalysis has been discovered from prokaryotes to eukaryotes. In addition to two yeast TPx isoforms (TSA I and TSA II/AHPC1) previously described, three additional TPx homologues were identified by analysis of the open reading frame data base for Saccharomyces cerevisiae. Three novel isoforms showed a distinct thiol peroxidase activity supported by thioredoxin, and appeared to be distinctively localized in cytoplasm, mitochondria, and nucleus. Each isoform was named after its subcellular localization such as cytoplasmic TPx I (cTPx I or TSA I), cTPx II, cTPx III (TSA II/AHPC1), mitochondrial TPx (mTPx), and nuclear TPx (nTPx). Their transcriptional activities suggest that cTPx I and cTPx III are the most predominant isoforms among the five type isoforms. Transcriptional activities of TPx isoenzymes during yeast life span were quite different from each other. Unlike other TPx null mutants, cTPx I null mutant was hypersensitive to various oxidants except for 4-nitroquinoline N-oxide. The null mutant was more resistant toward 4-nitroquinoline N-oxide and acidic culture than its wild type. The severe growth retardation of cTPx II mutant resulted in accumulation of G(1)-phased cells. Based on kinetic properties of five isoforms, their subcellular localizations, and distinct physiology of each null mutant, we discussed the physiological functions of five types of TPx isoenzymes in yeast throughout the full growth cycle.

Light chain of natural antibody plays a dominant role in protein antigen binding

Examinations of the contribution and the specificity of heavy (H) and light (L) chains of natural antibodies to antigen binding may help us to better understand antigen recognition and the development of naive B cells. We previously generated natural Fab antibody fragments reactive to preS1 of HBV using a naive, non-immunized Fab antibody library derived from peripheral B cells of a normal healthy volunteer. We now constructed expression vectors for the Fd (VH + CH1), L chain, and scFv fragments using the sequences encoding parental Fabs as a source of natural antibody genes. The recombinant antibody fragments were expressed as inclusion bodies in E. coli BL21 (DE) cells. When denatured and then refolded, the antibody fragments retained their binding properties. Recombinant L chains and scFvs exhibited three- to 40-fold higher affinities (in the order of 10(7) M(-1)) over the parental Fabs, whereas the affinities of Fds (in the order of 10(5) M(-1)) were much lower compared to the parental Fabs. The results obtained from sandwich ELISA revealed that the L chains bound the virus more efficiently than Fds. Additional experiments were performed to evaluate the specificity of the recombinant fragments for surface proteins of HBV. Fds and L chains were reactive towards HBsAg and the preS2 peptide as well as preS1 and showed patterns of epitope recognition quite different from those of parental Fabs. The data presented here demonstrate that the prominence of the L chain in determining protein binding activity is a property of natural antibodies and is quite unlike the antibodies induced by immunization, and that the specificity of Fab is not determined by the individual antibody chain but by the correct pairing of H and L chain.

Precursor of pro-apoptotic cytokine modulates aminoacylation activity of tRNA synthetase

Endothelial monocyte activating polypeptide II (EMAPII) is a cytokine that is specifically induced by apoptosis. Its precursor (pro-EMAPII) has been suggested to be identical to p43, which is associated with the multi-tRNA synthetase complex. Herein, we have demonstrated that the N-terminal domain of pro-EMAPII interacts with the N-terminal extension of human cytoplasmic arginyl-tRNA synthetase (RRS) using genetic and immunoprecipitation analyses. Aminoacylation activity of RRS was enhanced about 2.5-fold by the interaction with pro-EMAPII but not with its N- or C-terminal domains alone. The N-terminal extension of RRS was not required for enzyme activity but did mediate activity stimulation by pro-EMAPII. Pro-EMAPII reduced the apparent Km of RRS to tRNA, whereas the kcat value remained unchanged. Therefore, the precursor of EMAPII is a multi-functional protein that assists aminoacylation in normal cells and releases the functional cytokine upon apoptosis.

Generation and characterization of terahertz pulse trains from biased, large-aperture photoconductors

The saturation properties of terahertz emission from biased, large-aperture photoconductors excited by trains of amplified femtosecond optical pulses are presented. A direct comparison is made of the multiple-pulse saturation properties of terahertz emission from semi-insulating GaAs and low-temperature-grown GaAs emitters with different carrier lifetimes. When the carrier lifetime is less than or comparable with the interpulse spacing, a significant enhancement of the narrow-band terahertz output is observed. The enhancement is not observed for emitters with long carrier lifetimes, consistent with the results of a previously derived saturation theory [Opt. Lett. 18, 1340 (1993)].

Drug-resistant pulmonary tuberculosis in a tertiary referral hospital in Korea

OBJECTIVES

To estimate the resistance rate and to correlate the clinical characteristics of resistant tuberculosis with the patients of pulmonary tuberculosis who were referred to the university hospital.

METHODS

We prospectively performed sensitivity tests for all patients who were diagnosed as active tuberculosis by sputum smear or sputum culture from January, 1995 to June, 1996. Patients profile, previous treatment history, patterns of drug resistance, initial chest films and other clinical findings were analysed.

RESULTS

Overall, 24(26.0%) of the 92 patients had resistance to at least one drug and 8(8.6%) had resistance to isoniazid(INH) and rifampin(RFP). Among the 66 patients without previous tuberculosis therapy, 11(16.6%) were drug-resistant and 2(3.0%) were multi-drug resistant. Among the 26 patients with previous therapy, 13(50.0%) were drug-resistant and 6(23.0%) were multi-drug resistant. For all 92, resistance to INH was most common (19.5%), followed by RFP (9.7%) and ethambutol (9.7%). Drug resistance was significantly high in previously treated patients and in cavity-positive patients. Treatment failure was also high in previously treated patients with resistant tuberculosis. In patients with primary resistance, treatment failure was not observed.

CONCLUSION

Sensitivity tests are strongly recommended in all culture positive patients with previous therapy but, in patients with primary resistance, sensitivity tests are not required. Proper combination chemotherapy should be given under careful surveillance.

Generation of human Fab monoclonal antibodies against preS1 of hepatitis B virus using repertoire cloning

Human monoclonal antibodies (MAbs) have considerable potential in the prevention and treatment of many viral diseases. A combinatorial antibody library of heavy (Fd)- and light-chain genes derived from peripheral blood lymphocytes of a volunteer with high antibody titer to preS1 of HBV was constructed and expressed on the surface of filamentous phages. The library contained 7 x 10(9) independent clones. A phage antibody population from the third panning against preS1 was converted to one expressing soluble Fabs by removal of the g3 sequences from the pComb3 phagemid vector and subsequent transformation into E. coli TG1 cells. Screening of the library led to the identification of two clones, 3DW and 8GW, showing high reactivity toward preS1. The authenticity of the Fabs was confirmed by immunoblot analysis which yielded approximately 60 and approximately 30 kDa bands under nonreducing and reducing conditions, respectively. The soluble Fabs of 3DW and 8GW exhibited relative affinities of 6 x 10(5) and 8 x 10(6) M(-1), respectively. The sequencing results demonstrate that all Fd sequences belong to subgroup II and all light chain sequences belong to subgroup I. There are differences in CDR length and composition, especially in the FW3 and CDR3 regions of the heavy- and light-chain genes. These human Fab MAbs specific to preS1, generated from a combinatorial library, represent prototypes of passive immunotherapy candidates for viral hepatitis B.

Efficient High-Energy Pulse-Train Generation Using a 2 n-Pulse Michelson Interferometer

We demonstrate a novel, Michelson-based, ultrafast multiplexer with a throughput approaching 100% for a polarization-multiplexed train and 50% for a linearly polarized train, which is compatible with a high-energy pulse train and shaped-pulse generation. The interpulse spacings in the resultant 2(n)-pulse train can be adjusted continuously from multinanoseconds through zero. Using this interferometer, we also demonstrate generation of a 16-pulse train of terahertz pulses.

Molecular and serologic survey of Orientia tsutsugamushi infection among field rodents in southern Cholla Province, Korea

Field rodents were collected from six areas in southern Cholla Province, Korea from October to December 1993. Twenty-eight (24%) of the 119 Apodemus agrarius were seropositive (> 1:10) for Orientia tsutsugamushi by the passive hemagglutination assay (PHA). Of the seropositive cases, 11 specimens had antibody titers greater than 1:80. No seropositive specimens were found among the eight Crocidura lasiura collected. On the other hand, the polymerase chain reaction (PCR) amplified about 520 basepairs of a gene encoding the 56-kD protein from the genomic DNA of 12 strains of O. tsutsugamushi tested. This target DNA sequence was amplified from the 11 (8.7%) blood specimens of A. agrarius, and one of the eight C. lasiura also showed evidence of O. tsutsugamushi infection by PCR. Only one of the PCR-positive samples was also PHA-positive. These results suggest that the PCR combined with a serologic assay more accurately detects the degree of infection of rodents with rickettsiae-causing scrub typhus in epidemiologic surveys.

Language, context, and speaker effects in the identification and discrimination of English /r/ and /l/ by Japanese and Korean listeners

Japanese and Korean listeners' identification and discrimination of English /r/ and /l/ were compared using a common set of minimal pair stimuli. The effects of speakers (two native speakers of Australian English), position of the contrast within the word (word initial, initial consonant cluster. and medial positions), and listening task (forced choice identification versus oddball discrimination) were examined, with a view to assessing the relative importance of language-specific and language-independent factors operating at the acoustic-phonetic and phonological levels of signal processing in "foreign sound" speech perception. Both prior phonological learning and the relative acoustic discriminability of the items affected subjects' performance on the identification test. Where both factors were engaged, phonological learning effects predominated over the effects of acoustic discriminability. The extent to which a speaker encoded critical acoustic cues for the /r-l/ distinction was found to affect /r-l/ identification. Dynamic spectral features known to be relevant for the /r-l/ contrast were effective in predicting (in a linear regression analysis) speaker-dependent differences in identification scores. Although the discrimination test may have been influenced by ceiling effects, the performance profiles on the identification and discrimination tests were quite different, indicating that the identification and discrimination tests imposed quite different task demands upon listeners and that phonological processing of the signal was more engaged by the former task.

Mapping of antigenic determinant regions of the Bor56 protein of Orientia tsutsugamushi

The 56-kDa protein (Bor56) of Orientia tsutsugamushi is an immunoprotective antigen and is the target molecule of neutralizing antibodies. This antigen is recognized by almost all of the serum antibodies produced by patients in the convalescence phase of scrub typhus. We expressed the Bor56 open reading frame in Escherichia coli and generated from it a series of deletion constructs as MalE fusion proteins. Antibody-binding domains were characterized by using patient sera, mouse monoclonal antibodies (MAbs), and Bor56-immunized-mouse sera. None of the antibodies bound to a fusion protein containing the carboxy-terminal 140 amino acids (aa) of the Bor56 protein, suggesting that the carboxy-terminal domain of Bor56 is not exposed on the surface of the molecule. Human immunoglobulin M (IgM) antibodies predominantly bound to antigenic domain I (AD I; amino acids [aa] 19 to 113) and AD III (aa 243 to 328). Human IgG antibodies also showed preferential binding to AD I. The epitope recognized by strain-specific MAb (KI4) or group-specific MAb (KI57) was mapped to AD II (aa 142 to 203). Mouse serum antibodies, elicited by immunization with deletion mutants, consistently bound to AD III. Moreover, the carboxy-terminal 140 aa of the Bor56 protein did not elicit an antibody response in C3H/HeDub mice. A model of the antigenic structure of Bor56 is presented and discussed. These results suggest that antigenic fragments from AD I and AD III are useful in the induction of humoral immunity against O. tsutsugamushi. These antigenic analyses provide an important foundation for further analyses of the neutralizing-antibody responses generated during rickettsial infections. They also provide potential peptide substrates for diagnostic assays and vaccine strategies.

Induction of neutralizing antibody in mice by immunization with recombinant 56 kDa protein of Orientia tsutsugamushi

Anti-oriential antibody inhibits Orientia tsutsugamushi attachment to, and penetration of, host cells. However, O. tsutsugamushi antigens that induce the production of a neutralizing antibody have not been identified. The authors immunized mice and rabbits with the recombinant 56 kDa protein of O. tsutsugamushi fused to the maltose binding protein of Escherichia coli (MBP-Bor56) and analysed their effect on O. tsutsugamushi attachment to or penetration of L929 cells. O. tsutsugamushi attachment and penetration were measured by using an indirect immunofluorescent antibody assay (IFA). O. tsutsugamushi growth in L929 cells was determined by [3H]thymidine uptake assay. By IFA, we observed a 96% reduction of attachment or penetration of O. tsutsugamushi treated with rabbit anti-MBP-Bor56 sera. [3H]thymidine uptake showed that mouse anti-MBP-Bor56 sera caused a 91% reduction in O. tsutsugamushi growth, when compared to mouse anti-MBP sera. These results suggest that the 56 kDa protein of O. tsutsugamushi plays an important role in O. tsutsugamushi attachment to or penetration of cells.

Sequencing and phylogenetic analysis of the spoIIA operon from diverse Bacillus and Paenibacillus species

In order to clone the spoIIA operon from three different Bacillus and Paenibacillus species, we designed two sets of PCR primers based on three previously published Bacillus spoIIA sequences. One set of primers corresponded to the C-terminal region of SpoIIAB and a region near the middle of SpoIIAC. These primers were used to amplify the corresponding region of spoIIA from Bacillus stearothermophilus and Paenibacillus polymyxa (previously called Bacillus polymyxa [see Ash, C., Priest, F.G., Collins, M.D., 1993. Molecular identification of ribosomal-RNA group 3 bacilli using a PCR probe test - proposal for the creation of a new genus Paenibacillus. Antonie van Leeuwenhoek Int. J. Gen. Mol. Microbiol. 64, 253-260]. The other set of primers, corresponding to an N-terminal and a C-terminal region of SpoIIAC, was used for B. sphaericus. The PCR products were used as probes for Southern blotting of homologous chromosomal DNA. DNA corresponding to spoIIA from the three organisms was identified by screening chromosomal DNA libraries, and cloned. Sequence analysis showed that all spoIIA sequences were conserved, but conservation was strongest in SpoIIAC and least strong in SpoIIAA. In the promoter the -35 region was conserved well but the -10 region rather poorly. Within the proteins, certain regions were particularly strongly conserved, suggesting that they are essential to the function of the protein. Phylogenetic analysis of spoIIA suggested that B. stearothermophilus is close to B. subtilis and B. licheniformis, but that P. polymyxa and B. sphaericus are remote from B. subtilis.

T-track PCR fingerprinting for the rapid detection of genetic polymorphism

The diversity of DNA sequences can be analyzed by comparing randomly amplified polymorphic DNA, or restriction fragment length polymorphism fragments of DNA. Such analyses are dependent on the selection of appropriate restriction enzyme(s) and/or primers. We have investigated a simpler approach to providing sensitive and specific genotyping. Cyclic extension of target sequences with dideoxythymidine generates PCR products with variable lengths. We analyzed these variable PCR products by scoring the number of variable bands and comparing the scores (numerical profiles) to establish similarities. We found that the polymorphic lengths of the PCR products were comparable among serologically defined strains. It suggests that this single PCR reaction followed by a one-step electrophoresis yields easily analyzable data that can be compared with data from other gels.

Induction of homologous immune response to Rickettsia tsutsugamushi Boryong with a partial 56-kilodalton recombinant antigen fused with the maltose-binding protein MBP-Bor56

Although the 56-kDa protein of Rickettsia tsutsugamushi has been presumed to play important roles in generating protective immunity against scrub typhus, studies of this protein have been impeded. We used the recombinant 56-kDa protein of R. tsutsugamushi Boryong fused with the maltose-binding protein of Escherichia coli (MBP-Bor56) to analyze its ability to induce protective immunity in a C3H/HeDub murine model. Intraperitoneal immunization of mice with MBP-Bor56 resulted in an increase in the 50% minimal lethal dose of more than 160 times compared with that for the control mice. Splenic mononuclear cells from the mice immunized with MBP-Bor56 showed a dose-dependent pattern of lymphocyte proliferation response and secreted gamma interferon and interleukin-2 when stimulated with irradiated R. tsutsugamushi Boryong, which is a cytokine profile of Th1 cells. High titers of antibody to R. tsutsugamushi were also demonstrated by indirect immunofluorescent-antibody testing. These findings suggest that the 56-kDa protein of R. tsutsugamushi is one of the candidates for a vaccine against scrub typhus.

Isolation of a new Orientia tsutsugamushi serotype

Orientia tsutsugamushi, the etiological agent of scrub typhus, is an antigenically diverse organism and many serologically distinct strains have been identified. The 56 kDa protein of O. tsutsugamushi, a major protein in the outer membrane, has been thought to be responsible for this antigenic variability. A strain of O. tsutsugamushi isolated in Korea cross-reacted with both Gilliam strain-specific and Karp strain-specific monoclonal antibodies. When its 56 kDa protein gene was cloned and analyzed, its sequence showed variation especially between 1,200 and 1,250 bp, showing that this isolate is a new O. tsutsugamushi strain.

Tetrodotoxin infusion: nonventilatory effects and role in toxicity models

OBJECTIVES

To determine the cardiovascular, autonomic, and neuromuscular effects of an IV infusion of tetrodotoxin (TTX) when ventilation is supported.

METHODS

TTX was infused in 18 anesthetized beagles during conventional mechanical ventilation. TTX infusion continued at a rate of 9.3 micrograms/kg/hr until apnea occurred with 1 minute of ventilator disconnection. Measurements included intravascular pressures, heart rate (HR), cardiac output, blood gases, displacements of the rib cage and abdomen, O2 delivery, and responses to train-of-four and tetanic peripheral nerve stimulation. Results are expressed as mean +/- SD.

RESULTS

During TTX infusion, all the dogs had discoordinate movements of the rib cage, abdomen, and limbs. Vomiting, urination, defecation, and increased salivation occurred. Nicotinic and muscarinic effects, neuromuscular blockade, and cardiovascular depression were produced by TTX. Apnea occurred in 72.0 +/- 17.0 minutes when a total of 119.0 +/- 17.4 micrograms of TTX was infused. At apnea, decreases in arterial pressure, cardiac index, HR, O2 delivery, and systemic vascular resistance occurred, while pulmonary artery pressure and pulmonary vascular resistance increased. Loss of response to tetanic stimulation was closely correlated with the dose of TTX that produced apnea.

CONCLUSION

The clinical symptoms and signs of TTX poisoning are similar to those of anticholinesterase poisons, and TTX dosing as described by this model may serve as a surrogate for organophosphorus poisoning. The model may be useful to determine optimum therapies for TTX poisoning and, since TTX prevents sodium influx into cells, to investigate enhanced survival in animals suffering from ischemia.