Monoclonal antibodies produced to bean yellow mosaic virus, clover yellow vein virus, and pea mosaic virus which cross-react among the three viruses

Incidence, Spatial Patterns, and Associations Among Viruses in Snap Bean and Alfalfa in New York

Recent epidemics in snap bean (Phaseolus vulgaris) characterized by virus-like symptoms prompted a survey of commercial fields for Alfalfa mosaic virus (AMV), Cucumber mosaic virus (CMV), and the Bean yellow mosaic virus (BYMV)/Clover yellow vein virus (ClYVV) complex in 2002 and 2003. Snap bean fields were either remote from or adjacent to alfalfa (Medicago sativa), a putative source of these viruses. Bean fields were sampled at the bloom stage in both years. Model-adjusted mean incidences of infection by AMV, BYMV/ClYVV, and CMV were 41.96, 6.56, and 6.69%, respectively, in alfalfa, and 6.66, 6.38, and 17.20% in snap bean. In 2002, 25.9% of snap bean plants were infected by more than one virus; <1% had more than one virus in 2003. Virus incidences did not differ between snap bean adjacent to or remote from alfalfa, but incidence of infection by AMV and BYMV/ClYVV was significantly higher in snap bean planted later in the season rather than earlier. In 2002, there was a positive association between AMV and CMV in the tendency to find both viruses in the same snap bean plant. In some years, infection by aphid-transmitted viruses can become widespread in snap bean in New York.

Characterisation and epitope analysis of monoclonal antibodies to virions of clover yellow vein and Johnsongrass mosaic potyviruses

Mouse monoclonal antibodies (MAbs) against the Australian B strain of clover yellow vein (ClYVV-B) and the JG strain of Johnsongrass mosaic (JGMV) potyviruses were produced, characterised and the epitopes with which they reacted were deduced. Using intact particles of ClYVV a total of ten MAbs were obtained which reacted strongly with ClYVV-B in an enzyme-linked immunosorbent assay and Western blots. Four of these MAbs (1, 2, 4, and 13) were found to be ClYVV-specific, as they reacted with all five ClYVV strains from Australia and the U.S.A. but not with 11 strains of bean yellow mosaic (BYMV), pea mosaic (PMV), and white lupin mosaic (WLMV) viruses which, together with ClYVV, form the BYMV subgroup of potyvirses. These MAbs failed to react with eight other potyvirus species, including six which infect legumes like the viruses in the BYMV subgroup. The ClYVV MAb 10 was found to be BYMV subgroup-specific. It reacted strongly with 15 of the 16 strains of viruses in the subgroup and gave no reaction with eight other potyviruses. The other five ClYVV MAbs reacted with varying degrees of specificity with the BYMV subgroup viruses and also with other potyviruses. Eight of the ClYVV MAbs (1, 2, 4, 5, 13, 17, 21, and 22) reacted with the intact coat proteins only and not with the truncated (minus amino terminus) coat protein of ClYVV suggesting that the epitopes for these MAbs are located in the surface-exposed, amino-terminal region of the ClYVV coat protein. Comparison of published coat protein sequences of BYMV and ClYVV isolates indicated that the epitopes for the four ClYVV-specific MAbs may be in the amino-terminal region spanning amino acid residues 18 to 30, whereas those for the other four MAbs may be located in the first 17 amino-terminal amino acid residue region. The epitopes that reacted with BYMV subgroup-specific MAb 10 and MAb 30 which reacted with 20 of the 24 potyvirus isolates, are probably located in the core region of ClYVV coat protein as these MAbs reacted with the intact as well as truncated coat protein of ClYVV. Analysis, in Western blot immunoassay, of 17 MAbs raised against virions of JGMV revealed that only two MAbs (1-25 and 4-30) were JGMV-specific, whereas others displayed varying degrees of specificity to different potyviruses.(ABSTRACT TRUNCATED AT 400 WORDS)

Bean yellow mosaic, clover yellow vein, and pea mosaic are distinct potyviruses: evidence from coat protein gene sequences and molecular hybridization involving the 3' non-coding regions

The sequences of the 3' 1019 nucleotides of the genome of an atypical strain of bean yellow mosaic virus (BYMV-S) and of the 3' 1018 nucleotides of the clover yellow vein virus (CYVV-B) genome have been determined. These sequences contain the complete coding region of the viral coat protein followed by a 3' non-coding region of 173 and 178 nucleotides for BYMV-S and CYVV-B, respectively. When the deduced amino acid sequences of the coat protein coding regions were compared, a sequence identity of 77% was found between the two viruses, and optimal alignment of the 3' untranslated regions of BYMV-S and CYVV-B gave a 65% identity. However, the degree of homology of the amino acid sequences of coat proteins of BYMV-S with the published sequences for three other strains of BYMV ranged from 88% to 94%, while the sequence homology of the 3' untranslated regions between the four strains of BYMV ranged between 86% and 95%. Amplified DNA probes corresponding to the 3' non-coding regions of BYMV-S and CYVV-B showed strong hybridization only with the strains of their respective viruses and not with strains of other potyviruses, including pea mosaic virus (PMV). The relatively low sequence identities between the BYMV-S and CYVV-B coat proteins and their 3' non-coding regions, together with the hybridization results, indicate that BYMV, CYVV, and PMV are distinct potyviruses.

Serology of potyviruses: current problems and some solutions

The serological relationships among members of the family Potyviridae are extremely complex and inconsistent. Variable cross-reactivity of polyclonal antisera, unexpected paired relationships between distinct viruses, and lack of cross-reactions between some strains are the major problems associated with the serology of potyviruses. Recent biochemical and immunochemical investigations of coat proteins have established the molecular basis for potyvirus serology and provided explanations for most of the problems with serology of potyviruses. Information from these studies has also formed the basis for the development of several novel approaches to the accurate detection and identification of potyviruses. However, even these novel approaches are not without drawbacks and some of them cannot be applied easily in plant virus laboratories, since they require prior sequence information and facilities for peptide synthesis. These findings suggest that serology is an imperfect criterion for the identification and classification of potyviruses.

Potyviruses, monoclonal antibodies, and antigenic sites

Virus-specific and cross-reactive monoclonal antibodies have been produced to at least 19 different aphid-transmitted potyviruses. This report summarizes the development of these monoclonal antibodies as well as presents information on the delineation of the virus-specific and group-common epitopes defined by these monoclonal antibodies. Virus-specific and group-common antigenic determinants were mapped by a variety of techniques, including analysis of antigen: antibody reactivity patterns, determination of N-terminal vs. trypsin-resistant core peptide-specificity, immunoanalysis of overlapping synthetic peptides, and immunoanalysis of bacterially expressed coat-protein gene products. Of those monoclonal antibodies that have been examined, monoclonal antibody-defined virus-specific epitopes are virion surface-located within the 30+ amino acid amino terminus, whereas the group-common epitopes are found in the trypsin-resistant core protein not usually located on the virion surface, as has been shown previously with certain polyclonal antibodies. New information is presented on the analysis of bean yellow mosaic virus amino terminal epitopes as well as on the identification of amino terminal antigenic determinants shared between strains of bean yellow mosaic virus and pepper mottle virus. A recommendation on the evaluation and use of a panel of potyvirus broad-spectrum reacting monoclonals as reference monoclonal antibodies for the detection and classification of aphid-transmitted potyviruses is also presented.

Potyvirus serology, sequences and biology

Amino acid sequences of the cytoplasmic cylindrical inclusion protein (CIP), large nuclear inclusion protein (NIb), and coat protein (CP) of potyviruses were re-examined in light of reported serological relationships, and correlated with known and deduced biological functions. No obvious correlations were observed between either amino acid sequences or epitopes recognized by monoclonal antibodies and the natural host ranges of the potyviruses examined. Whereas the identified sequence motifs of the RNA helicase (CIP) and replicase (NIb) are predicted to be antigenic, most of the conserved sequences and epitopes in the CIP, NIb and CP were presumed to be maintained for structural rather than functional reasons. Three possible potyvirus clusters are proposed on the basis of the length and composition of the virion surface-exposed amino terminal extension of the CP; these clusters do not correlate with overall CP sequence homology, host range, or vectors, but are of potential evolutionary significance and hence of possible taxonomic value.