Rapid selection of genetic and antigenic variants of foot-and-mouth disease virus during persistence in cattle

Rapid evolution of foot-and-mouth disease virus (FMDV) is documented during persistent infections of cattle. The carrier state was established experimentally with plaque-purified FMDV of serotype C3. Virus was recovered from the esophageal pharyngeal area of the animals up to 539 days postinfection. Analysis of capsid proteins by electrofocusing and by electrophoretic mobility of the genomic poly(C)-rich tract suggested heterogeneity in several isolates and sequential dominance of viral subpopulations. Nucleotide sequences of the VP1-coding region of the parental FMDV C3 clones and of seven isolates from the carrier cattle showed point mutations that represented rates of fixation of mutations of 0.9 X 10(-2) to 7.4 X 10(-2) substitutions per nucleotide per year; 59% of the base changes led to amino acid substitutions, some of which were located within residues 135 to 151, a region involved in neutralization of FMDV. In the esophageal pharyngeal fluid samples, FMDV C3-neutralizing activity was present. Antigenic variation was demonstrated with monoclonal antibodies raised against FMDV C3. Two isolates from carrier cattle differed from the parental virus by 10(2)- or 10(3)-fold decreased reactivity with neutralizing monoclonal antibodies. We suggest that persistent, inapparent infections of ruminants, in addition to being a reservoir of virus, may promote the rapid selection of antigenically variant FMDVs.

Coevolution of cells and viruses in a persistent infection of foot-and-mouth disease virus in cell culture

Virus and cells evolve during serial passage of cloned BHK-21 cells persistently infected with foot-and-mouth disease virus (FMDV). These carrier cells, termed C1-BHK-Rc1 (J.C. de la Torre, M. Dávila, F. Sobrino, J. Ortín, and E. Domingo, Virology 145:24-35, 1985), become constitutively resistant to the parental FMDV C-S8c1. Curing of late-passage C1-BHK-Rc1 cells of FMDV by ribavirin treatment (J.C. de la Torre, B. Alarcón, E. Martínez-Salas, L. Carrasco, and E. Domingo, J. Virol. 61:233-235, 1987) did not restore sensitivity to FMDV C-S8c1. The resistance of C1-BHK-Rc1 cells to FMDV C-S8c1 was not due to an impairment of attachment, penetration, or uncoating of the particles but to some intracellular block that resulted in a 100-fold decrease in the amount of FMDV RNA in the infected cells. FMDV R59, the virus isolated from late-passage carrier cells, partly overcame the cellular block and was more cytolytic than FMDV C-S8c1 for BHK-21 cells. Sequencing of the VP1 gene from nine viral clones from C1-BHK-Rc1 cells showed genetic heterogeneity of 5 X 10(-4) substitutions per nucleotide. Mutations were sequentially fixed during persistence. In addition to resistance to FMDV C-S8c1, C1-BHK-Rc1 cells showed a characteristic round cell morphology, and compared with BHK-21 cells, they grew faster in liquid culture, were less subject to contact inhibition of growth, and had an increased ability to form colonies in semisolid agar. Reconstitution of a persistent infection was readily attained with late-passage C1-BHK-Rc1 cells and FMDV C-S8c1 or FMDV R59. The results suggest that coevolution of BHK-21 cells and FMDV contributes to the maintenance of persistence in cell culture.

VP1 of serotype C foot-and-mouth disease viruses: long-term conservation of sequences

The nucleotide sequences of the VP1-coding regions of several isolates of serotype C3 foot-and-mouth disease virus (FMDV) were determined. The deduced amino acid sequences were compared with those of serotype C1 FMDV. The results provide evidence for two different lineages of FMDV C3 and document the potential for both long-term conservation and rapid evolution of FMDV.

Five French versus eight French catheters and the Judkins technique. Advantages and limitations for studying coronary artery disease

In order to compare 5 French versus 8 French catheters for assessing ischemic heart disease, we prospectively studied 2 groups of 100 patients each, one with 5 French (group I) and the other with 8 French (group II) catheters by the Judkins technique. Significant differences were found in the greater easiness to catheterize LV (p less than 0.05) and LCA (p = 0.01) in group II and in better quality image for LCA in group II (p less than 0.05), although all patients in both groups had acceptable image quality. Pressure curves quality was better in group II (p less than 0.01); X-ray exposure time was longer in group I (p less than 0.001) and arterial compression time in group II (p less than 0.0001). Group I showed 3 and group II 10 mild hematomas (p less than 0.05). The procedure could be completed by the elected first artery and type of catheter in 95 patients in group I and in 96 in group II. Thus, the Judkins technique with 5 French catheters is as valid as with 8 French for assessing ischemic patients, reducing arterial morbidity, although mildly increasing technical difficulty and mildly decreasing quality image.

Genetic and immunogenic variations among closely related isolates of foot-and-mouth disease virus

Genetic heterogeneity among closely related isolates of foot-and-mouth disease virus (FMDV) has been measured by direct sequencing of the VP1-coding-region RNA for three new FMDVs of serotype C1 and by additional sequences of RNA from previously reported isolates, all belonging to a single episode of disease [Sobrino et al., Gene 50 (1986) 149-159]. In the ten viruses compared, eight different VP1 are represented. The changes include amino acid substitutions at a critical antigenic determinant of VP1. We document that variations present in such natural isolates result in changes of the immunogenic properties of the viruses. Vaccines prepared with two of the FMDV C1 analyzed induce complete protection against an homologous virus but only partial protection against an heterologous virus in swine, the host from which these viruses were isolated.

Postextrasystolic potentiation of systolic gradient in valvular aortic stenosis: clinical usefulness and analysis of hemodynamic factors

To analyze the behavior of aortic valve gradient (AVG) after ventricular extrasystole (VE), we studied 36 pure valvular aortic stenoses (AS) free of coronary artery disease and obstructive hypertrophic cardiomyopathy, in whom basal (B) (74 +/- 32 mm Hg) and catheter-induced post-VE (110 +/- 50 mm Hg) AVG were obtained. In all 26 cases with valve area less than 0.70 cm2, the post-VE AVG was greater than or equal to 70 mm Hg. In 19 cases AVG after two or more consecutive VE were also obtained. Maximal post-VE AVG was obtained after multiple VE (19 cases) and/or after one VE causing a post-VE pause equal or longer than 1.7 basal cardiac cycles (post-VE RR greater than or equal to 1.7 B RR) (9 cases). Basal and postsingle VE AVG, up to a post-VE RR greater than or equal to 1.7 B RR, were a linear function of previous RR (r greater than or equal to 0.90), regression line slope increasing with AS severity (P = .05). Inotropic state measured by PEP/LVET only increased after multiple VE, P less than .01. AVG after multiple VE was independent of post-VE RR. Thus, 1) post-VE potentiation of AVG may be seen with fixed valvular AS without obstructive cardiomyopathy; 2) post-VE AVG is a function of compensatory pause after single VE and of increased inotropism after multiple VE; 3) analysis of maximal post-VE AVG generated as described is reliable and useful for assessing AS severity (post-VE AVG greater than or equal to 70 mm Hg meaning an aortic valve area less than 0.70 cm2) and may supplement valve area calculations.

Cardiomegaly and abdominal mass in an acromegalic patient

We herein report the case of a 53-year-old white acromegalic patient with an abdominal mass due to massive cardiomegaly. The patient suffered from long lasting acromegaly refractary to bromocriptine, transsphenoidal surgery and radiotherapy. He had been previously diagnosed as having systemic hypertension, ischemic chest pain and congestive heart failure with marked cardiomegaly. The present admission was due to asthenia, anorexia and weight loss that were finally attributed to adrenal insufficiency secondary to radiotherapy. Plain abdomen X-ray suggested the presence of supramesocolic mass. A large cold area in the left hepatic lobe was detected on the radionuclide liver scan. Radionuclide angiography surprisingly identified the cold area as a vascular structure corresponding to the heart. A body CT scan revealed the heart was expanding between stomach and liver. Two-dimensional echocardiography showed marked enlargement of left ventricle. Cardiomegaly was probably multifactorial (chronic hypertension, ischemic heart disease and acromegaly). To our knowledge, this is the first reported case of massive cardiomegaly behaving as an intraabdominal mass. This possibility must be considered when invasive intraabdominal diagnostic procedures are to be done, particularly in an acromegalic patient.

Reactivity with monoclonal antibodies of viruses from an episode of foot-and-mouth disease

A panel of 12 monoclonal antibodies (MAbs) raised against foot-and-mouth disease virus (FMDV) of serotype C1 (FMDV C-S8c1) and 11 MAbs raised against other FMDVs have been used to evaluate the reactivity of 14 isolates of FMDV of serotype C1 (series FMDV C-S), 12 of them from one disease episode (Spain 1979-1982). The assays used were immunoelectrotransfer blot, immunodot and neutralization of infectivity. None of the isolates could be clearly distinguished by its reactivity with 6 non-neutralizing and 2 neutralizing MAbs raised against FMDV C-S8c1. In contrast, the isolates were distinguished in two groups by a 10(2)-fold difference in their reactivity with 6 neutralizing MAbs. The reactivity of MAbs with synthetic peptides indicated that conserved and non-conserved epitopes recognised respectively by neutralizing MAbs 4G3 and SD6 are localized in the immunogenic region (amino acids 138-156) of VP1. Thus, epidemiologically related FMDVs differ in at least one epitope critical for virus neutralization.

Ribavirin cures cells of a persistent infection with foot-and-mouth disease virus in vitro

Ribavirin (1-beta-D-ribofuranosyl-1H-1,2,4-triazole-3-carboxamide) eliminates foot-and-mouth disease virus from persistently infected cell cultures. The latter are 10-fold more sensitive to ribavirin than lytically infected cells. In treated cells no viral RNA or proteins could be detected by dot-blot hybridization to cDNA probes, virus and RNA infectivity assays, or immunofluorescence. A potential application of the drug for the treatment of animals carrying the virus is suggested.

Venous digital angio-radiography: an accurate and useful technique for assessing coronary bypass graft patency

Digital angiography has been reported to be a valid technique for anatomical studies of the peripheral cardiovascular system and for dynamic studies of ventricular function. The purpose of the present study was to assess the usefulness and accuracy of venous digital angiography (2 images per second) for imaging coronary bypass grafts after coronary artery bypass surgery, comparing its results with those of selective angiography. Fifty-two patients with 108 grafts (101 venous grafts and 7 internal mammary artery grafts) were studied by venous digital angiography and selective angiography. Venous digital angiography correctly diagnosed 95 out of 97 patent grafts and the 11 occluded grafts visualized by selective angiography. These results are better than those obtained in the very few studies so far reported in the literature. We were not able to adequately visualize distal anastomoses in most patients although we could identify the distal portion of 7 out of 8 patent sequential bypass grafts. Thus, these results suggest that venous digital angiography is a useful and accurate technique for assessing coronary bypass graft patency.

Postmyocardial infarction left ventricular thrombus. An unusual cause of transient intractability of heart failure

A case of a transient and huge postanterior acute myocardial infarction left ventricular thrombus causing temporary intractability of severe heart failure is reported. Echographic and hemodynamic data suggest the restrictive-obliterative pattern of heart failure.

Fixation of mutations in the viral genome during an outbreak of foot-and-mouth disease: heterogeneity and rate variations

Rates of fixation of mutations during the evolution of the foot-and-mouth disease virus (FMDV) C1 in nature have been estimated by hybridization of viral RNA to cloned cDNAs representing defined FMDV genome segments, and comparison of the selected RNAs by T1 RNase oligonucleotide fingerprinting. Values ranged from less than 0.04 X 10(-2) to 4.5 X 10(-2) substitutions per nucleotide per year (s/nt/yr), depending on the time period and the genomic segment considered. Rates for viral structural protein genes were up to sixfold higher than for nonstructural protein genes. Values in excess of 10(-2) s/nt/yr have been measured for the RNA region that encodes VP1-VP3. The nucleotide sequences of the major immunogenic region of capsid protein VP1 have been determined for six new FMDV C1 isolates, and they are compared with the two previously known sequences of FMDV C1 (C-S8 and C1-O). Both oligonucleotide fingerprinting of selected RNA fragments and direct nucleotide sequencing demonstrate that genetic heterogeneity exists among three viruses isolated on the same day, introducing a significant indetermination in the evaluation of fixation rates of mutations. During the FMDV C1 outbreak, amino acid substitutions did occur that are known to affect the immunological properties of the virus. The proportion of mutations between two viral RNAs does not increase significantly with the time elapsed between the two isolations, suggesting a cocirculation of multiple, related, nonidentical FMDVs ('evolving quasispecies') as the mode of evolution of this agent.

Oriented synthesis and cloning of influenza virus nucleoprotein cDNA that leads to its expression in mammalian cells

The influenza virus nucleoprotein gene has been cloned by a procedure that involves direct cDNA synthesis onto the primer-vector pBSV9, a pBR322-SV40 recombinant plasmid. dT-tailed pBSV9 was used to prime the synthesis of cDNA on a template of in vitro synthesized viral mRNA. The synthesis of ds-cDNA was initiated by a specific oligodeoxynucleotide and the resulting recombinant was circularized by intramolecular ligation. Recombinant pSVa963 contained the viral nucleoprotein gene directly fused to the SV40 early promoter region included in pBSV9 and followed by a dA:dT tail and the SV40 polyadenylation signal. When pSVa963 was used to transfect COS-1 cells, the presence of three NP-specific mRNAs of 1600, 1900 and 2500 nucleotides in length could be detected. Pulse labelling experiments of COS-1 transfected cells and immunobinding to a nucleoprotein monoclonal antibody indicated the synthesis of nucleoprotein. This nucleoprotein accumulated in the nucleus of transfected cells at a level similar to that found in infected cells. The vector and method described may be useful for the specific cloning and expression of any mRNA for which a 5'-terminal sequence is known.

A primer vector system that allows temperature dependent gene amplification and expression in mammalian cells: regulation of the influenza virus NS1 gene expression

Influenza virus RNA segment 8 has been cloned into primer-vector pSLts1. This vector was designed to replicate in simian cells in a temperature dependent fashion by use of the SV40 tsA209 T-antigen gene. The oriented synthesis of cDNA on dT-tailed pSLts1 was performed on in vitro synthesized mRNA, and the second DNA strand was primed with an influenza-specific terminal oligodeoxynucleotide. Recombinant pSLVa232 contained the RNA segment 8 sequence directly fused to the SV40 late promoter contained in pSLts1, and followed by the SV40 polyadenylation signal. Expression of NS1 gene in transfected COS cells took place at a level comparable to that found in infected cells. When VERO cell cultures were transfected with recombinant pSLVa232, expression of the NS1 gene was temperature dependent. Close to one hundred fold increase in the amplification and expression of the cloned gene was observed after shift down of the transfected cells to permissive temperature. Vector pSLts1 and the cloning strategy described may be useful for the specific cloning and regulated expression of mRNAs of known 5'-terminal sequence.

Direct non-invasive techniques for assessing coronary bypass graft patency

Venous digital subtraction angiography (vDSA) and computed tomography (CT) are two non-invasive techniques that allow direct imaging of coronary grafts. Neither of them is 100% accurate when compared to selective angiography. We studied 52 patients with 107 coronary grafts (101 saphenous and 6 mammary artery grafts) by CT and vDSA. Fifty patients had control selective angiography and 2 had control digital arterial aortography. CT correctly diagnosed 88 of the 95 patent grafts and 8 out of the 12 occluded grafts (in 1 patient 3 patent grafts could not be well analyzed owing to artifacts from pacemaker wires). vDSA correctly identified 93 patent grafts and the 12 occluded grafts, allowing the correct diagnosis of the 11 non/or misdiagnosed CT grafts. CT allowed the correct identification of the 2 misdiagnosed vDSA grafts. These results show that when there was agreement between CT and vDSA there were no diagnostic errors and that the combination of these two non-invasive techniques may avoid selective angiography for studying coronary bypass graft patency.

Establishment of cell lines persistently infected with foot-and-mouth disease virus

Cell lines persistently infected with foot-and-mouth disease virus (FMDV) have been established by growth of BHK-21 (c-13) or IBRS-2 (c-26) that survived standard cytolytic infections with FMDV. They maintain cytoplasmic FMDV RNA sequences, as shown by dot blot hybridization tests, using cloned FMDV cDNA as probes. Cell line C1-BHK-Rc1 was derived by infection of cloned BHK-21 c1 cells and plaque-purified FMDV C-S8 c1. Indirect immunofluorescence assays indicated the presence of FMDV antigens. It was resistant to superinfection by FMDV C-S8 c1, O-S7, or A5, but not by encephalomyocarditis virus (EMCV), vesicular stomatitis virus (VSV), or Semliki forest virus (SFV). Infectious FMDV was detected in the culture medium only up to cell passage 65. The virus isolated from C1-BHK-Rc1 cells showed decreased plaque size and diminished yield in infections at 42 degrees. Multiple mutations in the intracellular FMDV RNA have been detected by T1 oligonucleotide fingerprinting of genomic RNA segments hybridized to FMDV cDNA fragments. At late cell passages, when no infectious FMDV is detected, cells continue to express viral antigens and FMDV RNAs with deletions of up to 3 kb have been identified by Northern blot analysis. We conclude that persistent infections of cell cultures with FMDV are readily established and that multiple genetic and phenotypic variations occur in the virus during persistence.

Heterogeneity among influenza H3N2 isolates recovered during an outbreak. Brief report

Isolates of the H3N2 subtype recovered during an outbreak have been analyzed at the genomic and protein level. No reassortant genomes were detected. By T1-oligonucleotide fingerprinting of RNA segments coding for hemagglutinin (HA), nucleoprotein (NP), and neuraminidase (NA) two genotypes were found.

Hemodynamic evaluation of stenotic cardiac valves: II. Modification of the simplified valve formula for mitral and aortic valve area calculation

Since the introduction by Gorlin and Gorlin of the hydraulic formulae for calculating valve area, it has become the best parameter for quantitating valve stenosis. Recently Hakki et al proposed a simplified formula for valve area calculation that does not take into account either heart rate (HR) or left ventricular filling or ejection time. The purpose of this study was to analyze the validity of Hakki's formulae under different physiological conditions and to propose an easy correction to improve its accuracy. Our study suggests: (1) that an easy correction for heart rate in certain cases, dividing by 1.35 when HR less than 75 beats per min in mitral stenosis and when HR greater than 90 beats per min in aortic stenosis, significantly improves the accuracy and validity of Hakki's formulae (p less than 0.02 and p less than 0.05); (2) the instantaneous valve gradients (peak gradient for aortic stenosis and average of instantaneous early, middle, and late diastolic gradients for mitral stenosis) are as valid as mean planimetric gradients for valve area calculation. Thus the simplified formulae proposed in this study allow mitral and aortic valve area calculations by means of instantaneous gradients, cardiac output, and heart rate.

Hemodynamic evaluation of stenotic cardiac valves: I. Effect of ventriculography and atropine on mitral stenosis

Mitral area is the parameter used for quantitating mitral stenosis (MS) severity. When mitral gradient (MG) is low and reduction of mitral valve area (MVA) might be critical, interventions presumably increasing mitral valve flow (MVF), such as stress or atrial pacing, have been carried out. The purpose of this study was to analyze in 28 patients the combined effect of left ventriculography (LVG) and intravenous atropine (ATR) in the hemodynamic evaluation of MS. The rationale for combining these two interventions is to add up the ATR-positive chronotropic effect to the LVG potentiation of cardiac output. The LVG plus ATR markedly accelerated heart rate (from 80 +/- 14 to 104 +/- 18 bts/min, P less than 0.001), mildly increased cardiac index (from 2.6 +/- 0.6 to 2.9 +/- 0.6 1/min/m2, P less than 0.05), and importantly increased MVF (from 136 +/- 30 to 172 +/- 46 ml/bt, P less than 0.001). Pulmonary wedge pressure increased (from 14 +/- 5 to 21 +/- 5 mmHg, P less than 0.001) because of an important increment of MG (from 12 +/- 6 to 18 +/- 7 mmHg, P less than 0.001). None of six cases with mild MS (MVA greater than 1.5 cm2) and nine of ten cases with severe MS (MVA less than or equal to 1.0 cm2) had MG after LVG plus ATR greater than 12 mmHg. The remaining case with severe MS and the two cases (out of 12) with moderate MS having MG after LVG plus ATR less than or equal to 12 mmHg had, at surgical evaluation, noncritically reduced MVA. This study shows that LVG plus ATR is a valid and easy intervention for increasing MVF during cardiac catheterization. It also allows the reclassification of patients with low baseline MG and reduced MVA into two subgroups: Cases with critically reduced MVA at surgery achieve a postintervention MG greater than 12 mmHg and those cases with noncritically reduced MVA achieve a postintervention MG less than or equal to 12 mmHg.