Cardiotrophin-1 (CT-1) leads to a specific form of ventricular hypertrophy characterized by sarcomeres added in series, and has been reported to be elevated in heart failure. Previous competitive assays for CT-1 necessitate the extraction of plasma and involve prolonged incubations. We describe the development of a non-competitive assay for CT-1 that can measure plasma levels without the need for extraction. Two antibodies specific for the mid-section (amino acids 105-120) and C-terminal (amino acids 186-199) portions of CT-1 were developed in rabbits. One antibody was immobilized and used as the capture antibody. The other antibody was affinity purified and biotinylated. Unextracted plasma was incubated with these antibodies, and detection was with methylacridinium ester-labelled streptavidin. Plasma was obtained from 40 patients with heart failure and 40 normal control subjects. The non-competitive assay demonstrated a linear increase in chemiluminescence (measured as relative light units) with increasing amounts of full-length recombinant CT-1, with no evidence of a hook effect at high concentrations. The lower limit of detection was 2.9 fmol/ml. Intra-assay coefficients of variation ranged from 3.1% to 4.2% in the 10-40 fmol/well concentration range, and interassay coefficients of variation ranged from 3.5% to 4.5% in the 550-950 fmol/ml range. Measurements of CT-1 levels in patients with heart failure (median 166.5 fmol/ml; range 49.5-2788 fmol/ml) revealed very significantly elevated levels compared with those in normal controls (median 43.5 fmol/ml; range 11.2-258.6 fmol/ml; P<0.0001 by Mann-Whitney test). At a CT-1 concentration of 68 fmol/ml, sensitivity and specificity were 95% and 82.5% respectively. Thus this new non-competitive immunochemiluminometric assay for CT-1 could successfully detect full-length recombinant CT-1 in unextracted plasma, and demonstrated that plasma levels of CT-1 were significantly elevated in patients with heart failure.

The glycoprotein 130 (gp 130) signalling pathway is important in the development of heart failure. Cardiotrophin-1 (CT-1), a cytokine acting via the gp 130 pathway, is involved in the process of ventricular remodelling following acute myocardial infarction (AMI) in animals. The aims of the present study were to examine the profile of plasma CT-1 following AMI in humans, and its relationship with echocardiographic parameters of left ventricular (LV) systolic function. Serial measurements of plasma CT-1 levels were made in 60 patients at 14-48 h, 49-72 h, 73-120 h and 121-192 h following AMI and at a later clinic visit. LV function was assessed using a LV wall motion index (WMI) score on admission (WMI-1) and at the clinic visit (WMI-2). Compared with values in control subjects (29.5+/-3.6 fmol/ml), the plasma CT-1 concentration was elevated in AMI patients at 14-48 h (108.1+/-15.1 fmol/ml), 49-72 h (105.2+/-19.7 fmol/ml), 73-120 h (91.2+/-14.9 fmol/ml) and 121-192 h (118.8+/-22.6 fmol/ml), and at the clinic visit (174.9+/-30.9 fmol/ml) (P<0.0001). Levels were higher following anterior compared with inferior AMI. For patients with anterior AMI, CT-1 levels were higher at the clinic visit than at earlier times. WMI-1 correlated with CT-1 at all times prior to hospital discharge (P<0.05). On best subsets analysis, the strongest correlate with WMI-1 was CT-1 level at 49-72 h (R(2)=20%, P<0.05). In conclusion, plasma levels of CT-1 are elevated soon after AMI in humans and rise further in the subsequent weeks in patients after anterior infarction. CT-1 measured soon after AMI is indicative of LV dysfunction, and this cytokine may have a role in the development of ventricular remodelling and heart failure after AMI.

1. An epizootic killing 90% of a stock of 500 guinea-pigs has been described; cultures from these guinea-pigs frequently gave an organism indistinguishable by cultural or serological tests from the B. aertryck and the B. suipestifer.2. This organism was highly pathogenic when inoculated subcutaneously into guinea-pigs and of low pathogenicity when given to them with food.3. Healthy contacts put with animals infected subcutaneously or fed with the bacillus did not die.4. Sterile filtrates of organs of guinea-pigs of the infected stock administered by different methods frequently killed.5. The evidence definitely suggests that the essential infecting agent in the epizootic was a filter-passer.

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