|Nikolaeva, Olga -|
|Roop, Daniel -|
|Galvino-Costa, Suellen -|
|Dos Reis Figueira, Antonia -|
|Karasev, Alex -|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2012
Publication Date: April 1, 2012
Citation: Nikolaeva, O., Roop, D., Galvino-Costa, S., Dos Reis Figueira, A., Gray, S.M., Karasev, A. 2012. Epitope mapping for monoclonal antibodies recognizing tuber necrotic isolates of Potato virus Y. American Journal of Potato Research. 89:(2):121-128. Interpretive Summary: The tuber necrotic strain of Potato virus Y that emerged recently in the United States has the potential to cause significant yield and quality losses to both the seed and commercial potato industries. It is important that seed lots infected with this virus be identified and eliminated from seed stocks before they can be planted. The detection of this virus strain is usually accomplished using several commercially available antibodies, however there are reports that different results can be obtained depending on the antibody used. We investigated the specificity of each of the commercial antibodies by identifying the exact amino acid sequence of the virus coat protein reacts with each of the antibodies. This would allow us to identify if there was a difference among the antibodies and if the virus coat protein was variable in these regions and could be responsible for varying results. Three of the four antibodies were mapped to a linear segment of the coat protein; the fourth antibody could not be mapped. Of the three antibodies, two recognize the same piece of the coat protein and that piece of the coat protein contains two changes that allow these antibodies to bind specifically to the tuber necrotic strain. However, these two changes are also frequently changed in some isolates of the virus that would prevent the antibodies from binding and identifying the tuber necrotic virus. The other antibody consistently recognized all of the tuber necrotic viruses. This is valuable information for testing laboratories when making selections of antibodies for diagnostics testing purposes.
Technical Abstract: Potato virus Y (PVY) is an important viral pathogen of potato responsible for reducing tuber yield and quality across the globe. The PVYN and PVYNTN strains, the latter of which induces potato tuber necrotic ringspot disease (PTNRD), are regulated for international potato trade, and have been routinely detected using monoclonal antibodies (MAbs) that discriminate between PVYN and PVYO serotypes. Here, we identify the distinct binding sites in the capsid protein of PVY for three of the four main PVYN-specific MAbs, Bioreba-N, SASA-N, and Neogen- N, available commercially. These binding domains were mapped through a combination of TAS-ELISA testing of MAbs on multiple reference isolates of PVY, sequence analysis, heterologous expression of capsid protein fragments, and synthetic peptide binding experiments. All three MAbs were found to bind linear epitopes located within the first 31 N-terminal amino acids of the capsid protein.Bioreba-N MAb epitope spanned aa 1-17 and included three positions, aa 1, aa 11, and aa 17, which differ between PVYN and PVYO serotypes. Both SASA-N and Neogen-N epitopes spanned aa 22-30, and included two positions, aa 24 and aa 29, which differ between PVYN and PVYO serotypes. Epitopes for SASA-N and Neogen-N MAbs are likely to be identical or overlapping. Examination of available sequences for tuber necrotic isolates of PVY that do not react with PVYN-specific MAbs SASA-N and Neogen-N indicated possible selection for substitutions in corresponding epitopes leading to the loss of reactivity towards these antibodies. The data obtained suggested that testing with more than one PVYN serotype-specific MAb could assure a reliable serological identification of a PVYN or PVYNTN isolate.