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N J Knowles

Publications and source records attributed to N J Knowles.

16 recordsLinked to original sources
PubMed1992

Genetic relationships between southern African SAT-2 isolates of foot-and-mouth-disease virus.

Sequencing of part of the 1D gene of foot-and-mouth disease virus was used to determine the relationships between SAT-2 viruses isolated from outbreaks which occurred in cattle in Zimbabwe and Namibia and in impala in South Africa between 1979 and 1989. The results demonstrated that the outbreaks in different countries were unrelated. Surprisingly close relationships were shown between all SAT-2 viruses isolated from cattle in Zimbabwe since 1983 but the two major epizootics which occurred in 1989 were caused by viruses which were clearly different. Conversely, two apparently unrelated outbreaks in impala in South Africa were caused by viruses which could not be distinguished.

Africa, Southern↗
PubMed1992

Evolution of the capsid protein genes of foot-and-mouth disease virus: antigenic variation without accumulation of amino acid substitutions over six decades.

The genetic diversification of foot-and-mouth disease virus (FMDV) of serotype C over a 6-decade period was studied by comparing nucleotide sequences of the capsid protein-coding regions of viruses isolated in Europe, South America, and The Philippines. Phylogenetic trees were derived for VP1 and P1 (VP1, VP2, VP3, and VP4) RNAs by using the least-squares method. Confidence intervals of the derived phylogeny (significance levels of nodes and standard deviations of branch lengths) were placed by application of the bootstrap resampling method. These procedures defined six highly significant major evolutionary lineages and a complex network of sublines for the isolates from South America. In contrast, European isolates are considerably more homogeneous, probably because of the vaccine origin of several of them. The phylogenetic analysis suggests that FMDV CGC Ger/26 (one of the earliest FMDV isolates available) belonged to an evolutionary line which is now apparently extinct. Attempts to date the origin (ancestor) of the FMDVs analyzed met with considerable uncertainty, mainly owing to the stasis noted in European viruses. Remarkably, the evolution of the capsid genes of FMDV was essentially associated with linear accumulation of silent mutations but continuous accumulation of amino acid substitutions was not observed. Thus, the antigenic variation attained by FMDV type C over 6 decades was due to fluctuations among limited combinations of amino acid residues without net accumulation of amino acid replacements over time.

Amino Acid Sequence↗
PubMed1991

Evaluation of a trapping ELISA for the differentiation of foot-and-mouth disease virus strains using monoclonal antibodies.

A trapping enzyme-linked immunosorbent assay (ELISA) has been evaluated for the differentiation of foot-and-mouth disease virus (FMDV) strains using a panel of seven anti-serotype O monoclonal antibodies (MAbs). The variation of results within and between tests performed on the same day and on different days was examined using three strains of FMDV. Criteria for establishing antigenic differences between the strains as defined by the individual MAbs are proposed based on the variability measured, which can be used as standards by workers performing this test with other MAbs and FMDV strains.

Animals↗
PubMed1990

The complete nucleotide sequence of a pathogenic swine vesicular disease virus.

The nucleotide sequence of a swine vesicular disease virus (SVDV) strain that is pathogenic for pigs has been determined and compared with that of a non-pathogenic strain of SVDV, as well as a number of other enteroviruses. It shows only 98 base changes in comparison with a non-pathogenic strain of SVDV (Inoue et al., 1989, J. Gen. Virol. 70, 919-934). Fourteen of these nucleotide differences between the pathogenic and the non-pathogenic SVDV strains occur in the 5' non-coding region which, by analogy with the other picornaviruses, has been implicated in the efficiency with which the RNA is employed as mRNA. Additional differences found throughout the coding regions are largely conservative in nature. A number of residues are discussed as candidates for determinants of pathogenicity. This sequence has been submitted to the PIR database and has accession number A30061.

Amino Acid Sequence↗
PubMed1990

Antigenic analysis of serotype O foot-and-mouth disease virus isolates from the Middle East, 1981 to 1988.

During the period 1981-88 foot-and-mouth disease virus (FMDV) serotype O continued to be isolated from outbreaks in the Middle East. Field isolates submitted to the World Reference Laboratory have been examined in relation to reference strains by either complement fixation, virus neutralization or enzyme-linked immunosorbent assays. Most isolates were related to the European type O1 reference strains although strains emerging in late 1987 and 1988 were more closely related to O1/Manisa. In addition, FMDV isolates from Libya in 1981 and Syria in 1987 have shown very little relationship to these reference strains, although evidence of their persistence and spread has not been demonstrated.

Animals↗
PubMed1990

The complete nucleotide sequence of enterovirus type 70: relationships with other members of the picornaviridae.

Enterovirus type 70 (EV70) is the causative agent of acute haemorrhagic conjunctivitis and may also give rise to a rare neurological complication closely resembling poliomyelitis. The complete nucleotide sequence of the genome of EV70 has been determined from cDNA cloned in Escherichia coli. The genome consists of a 5' non-coding region of 726 nucleotides (nt), a long open reading frame of 6582 nt and a 3' non-coding region of 82 nt prior to the poly(A) tract. Comparison of the nucleotide sequence and the predicted amino acid sequence of the polyprotein with those published for other enteroviruses reveals sufficiently high similarity to predict antigenic regions and polyprotein cleavage sites. The P1 region of EV70 is as similar to those of the entero- as to those of the rhinoviruses, whereas the P2 and P3 regions are more closely related to the coxsackie B and swine vesicular disease viruses than other entero- or rhinoviruses.

Amino Acid Sequence↗
PubMed1990

A study of antigenic variants of foot and mouth disease virus type A in India between 1977 and 1985.

The structural polypeptides of thirty-three field isolates of foot and mouth disease virus (FMDV) collected in India between 1977 and 1985 were analysed by SDS-polyacrylamide gel electrophoresis. They were placed in eleven groups based on their patterns and compared with results of conventional serological (virus neutralisation and complement fixation) tests. Variation occurred in the structural proteins of the viruses isolated between 1977 and 1981; however, the polypeptide patterns of viruses isolated in 1984 and 1985 were identical.

Animals↗
PubMed1988

FRAGMAP--a program for restriction site map comparison.

A program is described which aligns pairs of linear restriction site maps using an algorithm which maximizes the number of coincident sites through the addition of extra 'padding' fragments; and makes maps of the non-conserved sites between pairs and triplets of input maps. A range of display facilities, hardcopy functions and database management routines are also included. The program runs on a stand-alone microcomputer, and is stored along with a database of several hundred files on a single floppy disc.

Copying Processes↗
PubMed1988

Serological and biochemical analysis of some recent type A foot-and-mouth disease virus isolates from the Middle East.

In 1986 and 1987 foot-and-mouth disease virus (FMDV) serotype A was isolated from outbreaks of disease in Saudi Arabia and Iran. Selected virus isolates were antigenically distinct from the prototype A22 virus strain (A22/Iraq/64), but were serologically related to each other. However, polyacrylamide gel electrophoresis showed that whilst the respective Saudi Arabian structural polypeptides were homogeneous, those from an Iran isolate were distinct. Direct sequencing of part of the P-1D (VP1) gene demonstrated considerable difference in nucleotide homology between the two groups of viruses; the Saudi Arabian viruses were closely related to each other but only distantly related to both the A22 prototype virus strain and the Iranian virus isolate. The latter viruses were only slightly more closely related to each other. Thus there appeared to be at least two distinct FMDV type A variants co-circulating in the Middle East, both of which differed considerably from the classical A22 subtype.

Animals↗
PubMed1985

A serological classification of bovine enteroviruses.

Cross virus neutralization (VN), complement fixation (CF) and immunoprecipitation (IP) tests were employed to compare the seven currently recognized bovine enterovirus (BEV) serotypes with seven serologically distinct strains previously isolated in Great Britain and two other BEV from the United Kingdom. Based on criteria used to differentiate other human and animal picornavirus serotypes, it was discovered that BEV types 1, 4, 5 and 6 were related to each other and could be included in a single serotype. Types 3 and 7 were found to be identical, and related to serotype 2. All of the other nine BEV were included in either serotype 1 or 2. Not all of the strains in each serotype were identical and antigenic variants were designated as subtypes. Antigenic relationships not revealed by VN were demonstrated in CF and IP tests. Bovine enterovirus strains whose antisera had the broadest intratypic reactivity were suggested as prototypes. The two proposed BEV serotypes could also be distinguished by their ability to agglutinate erythrocytes. Guinea pig erythrocytes were agglutinates by both serotypes while sheep red cells only reacted with serotype 1.

Animals↗
PubMed1985

A study of antigenic variants of foot-and-mouth disease virus by polyacrylamide gel electrophoresis of their structural polypeptides.

Twenty-nine foot-and-mouth disease (FMD) type A virus strains, previously classified serologically as distinct subtypes were analysed by polyacrylamide gel electrophoresis (PAGE) to determine the extent of variation in the pattern of the structural polypeptides and to evaluate the technique as an aid to existing subtyping techniques. The majority of the subtypes examined had distinct polypeptide patterns, however, some variation also occurred between strains within a subtype. The position of VP2(1B) and VP3(1C) was often unchanged in different strains within a subtype and between geographically related subtypes over long periods of time. Changes in the position of VP1(1D) were also observed within a subtype. The technique was considered to be of value for the screening of isolates prior to conventional serological subtyping procedures and in the tracing of the possible origin of FMD outbreaks.

Animals↗
PubMed1979

Classification of porcine enteroviruses by antigenic analysis and cytopathic effects in tissue culture: description of 3 new serotypes.

Porcine enteroviruses isolated in the United Kingdom between 1972 and 1976 were compared with the 8 serotypes previously described and with human coxsackie B virus types 1 to 6 for ability to grow in different cell lines. This allowed the classification of all strains into 3 broad groups according to type of cytopathic effect in IBRS-2 cells and further subdivision on the basis of production of cytopathic effect in BHK 21, HeLa and VERO cells. None of the porcine enterovirus strains was neutralized by antisera to human enteroviruses (Lim Benyesh-Melnick Pools) with the exception of swine vesicular disease virus, which was neutralised by coxsackie B5 antiserum. Antisera prepared either in gnotobiotic pigs or in guinea pigs against the 8 porcine enterovirus serotypes failed to neutralize 9 isolates which could be classified into 3 new serotypes, for which Nos. 9, 10 and 11 are proposed. Guinea pig sera could be used as an alternative to gnotobiotic pig sera for type differentiation.

Animals↗
PubMed1979

Molecular approach to the epidemiology of swine vesicular disease: correlation of variation in the virus structural polypeptides with serological properties.

Variation has been observed in the structural polypeptides of swine vesicular disease viruses isolated from the United Kingdom and Hong Kong. Despite the limited number of isolates examined, several distinct polypeptide patterns were obtained when the virus structural proteins were examined by polyacrylamide gel electrophoresis. Isolates from outbreaks in the United Kingdom which were known to be connected gave the same polypeptide pattern, whereas viruses with different polypeptide patterns could not be traced to a common source. The different polypeptide patterns were obtained consistently and were not altered by passage of the virus in tissue culture. In general, isolates with identical polypeptide patterns could not be distinguished by neutralization or antibody blocking tests or by competition radioimmunoassays. However, isolates with different polypeptide patterns could be differentiated by antibody blocking tests or radioimmunoassay. The correlation between the serological tests and the polyacrylamide gel electrophoresis analyses illustrates the value of analyzing structural polypeptides in the epidemiological study of swine vesicular disease.

Animals↗