Tomohiko Ogasawara

An endoprotease homologous to the blood clotting factor X as a determinant of viral tropism in chick embryo.

Host cell proteases responsible for activation of viral fusion glycoproteins are an important determinant for spread and tropism of various animal viruses. Exemplifying such proteases for the first time, we isolated an endoprotease from chick embryo, that activates para‐ and orthomyxovirus fusion glycoproteins by cleaving their precursor proteins at a specific, single arginine site. The protease is a calcium dependent serine protease consisting of two subunits, the 33 kd catalytic chain and the 23 kd chain possibly required for Ca2+ binding, and was found to be highly homologous, if not identical, to the blood clotting factor X(FX), a member of the prothrombin family. Its high efficiency and specificity in cleavage reactions was attributable to the properties characteristic of FX. Its role in vivo was strongly supported by cleavage inhibition in ovo highly selective for this virus group with a specific peptide inhibitor against FX.

Risk Factors for Drug-Resistant Pathogens in Community-acquired and Healthcare-associated Pneumonia

RATIONALE Identification of patients with drug-resistant pathogens at initial diagnosis is essential for treatment of pneumonia. OBJECTIVES To elucidate clinical features of community-acquired pneumonia (CAP) and healthcare-associated pneumonia (HCAP), and to clarify risk factors for drug-resistant pathogens in patients with CAP and HCAP. METHODS A prospective observational study was conducted in hospitalized patients with pneumonia at 10 institutions in Japan. Pathogens identified as not susceptible to ceftriaxone, ampicillin-sulbactam, macrolides, and respiratory fluoroquinolones were defined as CAP drug-resistant pathogens (CAP-DRPs). MEASUREMENTS AND MAIN RESULTS In total, 1,413 patients (887 CAP and 526 HCAP) were analyzed. CAP-DRPs were more frequently found in patients with HCAP (26.6%) than in patients with CAP (8.6%). Independent risk factors for CAP-DRPs were almost identical in patients with CAP and HCAP. These included prior hospitalization (adjusted odds ratio [AOR], 2.06; 95% confidence interval [CI], 1.23-3.43), immunosuppression (AOR, 2.31; 95% CI, 1.05-5.11), previous antibiotic use (AOR, 2.45; 95% CI, 1.51-3.98), use of gastric acid-suppressive agents (AOR, 2.22; 95% CI, 1.39-3.57), tube feeding (AOR, 2.43; 95% CI, 1.18-5.00), and nonambulatory status (AOR, 2.45; 95% CI, 1.40-4.30) in the combined patients with CAP and HCAP. The area under the receiver operating characteristic curve for counting the number of risk factors was 0.79 (95% CI, 0.74-0.84). CONCLUSIONS The clinical profile of HCAP was different from that of CAP. However, physicians can predict drug resistance in patients with either CAP or HCAP by taking account of the cumulative number of the risk factors. Clinical trial registered with https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&type=summary&recptno=R000004001&language=E ; number UMIN000003306.

Expression of factor X and its significance for the determination of paramyxovirus tropism in the chick embryo.

Enveloped animal viruses usually possess a surface glycoprotein which mediates fusion between the viral envelope and host cell membrane, hence enabling the initiation of infection, and its biosynthesis often involves post‐translational endoproteolytic activation of the inactive precursor by a host cell protease(s). Therefore, the protease distribution in the host must be critical for determining the viral tropism. We previously isolated from chick embryo a cogent candidate endoprotease of this kind for paramyxovirus infection, and demonstrated its identity with factor X (FX), a vitamin K‐dependent serine protease in the prothrombin family which, in general, is synthesized in the liver and circulates as one of the plasma proteases essential for blood clotting. Here, we examined FX expression with specific cDNA and antibody probes in a series of embryonic tissues. Many tissues other than the liver expressed the specific mRNA but, in most instances, the translation products remained inactive zymogen forms. The enzymatically active FXa was detectable only in the allantoic fluid and amniotic fluid, and virus spreading was strictly confined to the tissues in direct contact with these FXa‐containing fluids. Thus, the ectopically expressed FXa is probably the major host determinant of paramyxovirus tropism in ovo.

Primary structure of the virus activating protease from chick embryo : its identity with the blood clotting factor Xa

Host cell proteases activating, para‐ and orthomyxovirus fusion glycoprotein precursors play a crucial role in determining the viral tropism in infected organisms, We previously isolated such an endoprotease from the allantoic fluid of chick embryo and showed its close similarity to the activated form of blood clotting factor X (FXa) by partial amino acid sequencing. In this report, we have cloned and sequenced a cDNA of the protease and show that it is encoded in a single gene as a preproform with all the functional and structural domains known to be characteristic of bovine or human FX, establishing the identity between the protease and FXa.

Isolation of factor Xa from chick embryo as the amniotic endoprotease responsible for paramyxovirus activation

In chick embryo, certain paramyxoviruses mainly target the chorioallantois and the allantoamnion and show no extensive further spreading in the other organs. This has been explained by the possible presence of an endoprotease activating the viral fusion glycoprotein precursor in the allantoic and the amniotic fluid, and its absence in other places or organs, We previously isolated such an endoprotease from the allantoic fluid and demonstrated its identity with the clotting factor Xa. Exactly the same endoprotease by all the criteria including the N‐terminal amino acid sequence was now isolated from the amniotic fluid. Thus, the factor Xa seems to be a major host determinant of the viral tropism in chick embryo.

Risk factors for 30-day mortality in patients with pneumonia who receive appropriate initial antibiotics: an observational cohort study

BACKGROUND Appropriate initial antibiotics are essential for the treatment of infectious diseases. However, some patients with pneumonia might develop adverse outcomes, despite receiving appropriate initial antibiotics. We aimed to clarify the risk factors for 30-day mortality in patients who received appropriate initial antibiotics and to identify potential candidates who would benefit from adjunctive therapy. METHODS From March 15, to Dec 22, 2010, we did a prospective, observational study at ten medical institutions in hospitalised patients (aged ≥20 years) with pneumonia. We did a multivariable logistic regression analysis to calculate odds ratios (ORs) and 95% CI to assess the risk factors for 30-day mortality. This study was registered with the University Medical Information Network in Japan, number UMIN000003306. FINDINGS The 30-day mortality was 11% (61 of 579 patients) in the appropriate initial antibiotic treatment group and 17% (29 of 168) in the inappropriate initial antibiotic treatment group. Albumin concentration of less than 30 mg/L (adjusted OR 3·39, 95% CI 1·83-6·28), non-ambulatory status (3·34, 1·84-6·05), pH of less than 7·35 (3·13, 1·52-6·42), respiration rate of at least 30 breaths per min (2·33, 1·28-4·24), and blood urea nitrogen of at least 7·14 mmol/L (2·20, 1·13-4·30) were independent risk factors in patients given appropriate initial antibiotic treatment. The 30-day mortality was 1% (one of 126 patients), 1% (two of 168), 17% (23 of 137), 22% (20 of 89), and 44% (14 of 32) for patients with no, one, two, three, and four or five risk factors, respectively. INTERPRETATION Patients with two or more risk factors were at a higher risk of death during the 30 days assessed than were individuals with no or one risk factor, despite appropriate initial antibiotic treatment. Therefore, adjunctive therapy might be important for improving outcomes in patients with two or more risk factors. FUNDING Central Japan Lung Study Group.

Phase II study of carboplatin, cisplatin, and vindesine in advanced non-small-cell lung cancer

Cisplatin in combination with vindesine has been widely used for the treatment of advanced non-small-cell lung cancer (NSCLC), producing an overall response rate of 32%. We conducted a phase II study to examine whether the addition of carboplatin to the combination of cisplatin and vindesine would improve the antitumor activity of the two platinum agents in advanced NSCLC without increasing their toxicity. Carboplatin (240 mg/m2) and vindesine (3 mg/m2) were given intravenously on day 1 and cisplatin (60 mg/m2) and vindesine (3 mg/m2), on day 8. Of the 40 evaluable patients with advanced NSCLC, 12 showed a partial response, for an overall response rate of 30% (95% confidence interval, 17%–47%). The median duration of response was 12 weeks, and the median survival duration for all patients was 38 weeks. The major toxicity was hematologic: leukopenia (WHO grade≥3) was observed in 21 patients (53%) and anemia (WHO grade≥3), in 13 patients (33%). However, thrombocytopenia was mild and WHO grade 3 toxicity was observed in only 4 patients (10%). Nonhematologic toxicities consisted mainly of WHO grade≥2 nausea and vomiting in 16 patients (40%) and WHO grade≥2 alopecia in 11 patients (28%). No significant nephrotoxicity or neurotoxicity was seen. Our findings indicate that the addition of carboplatin to the combination of cisplatin and vindesine does not improve antitumor activity in patients with advanced NSCLC.