Lack of detection of a putative retrovirus associated with haemic neoplasia in the soft shell clam Mya arenaria

• Published in: Journal of invertebrate pathology Vol. 109; no. 1; pp. 97 - 104
• Main Authors: AboElkhair, M., Iwamoto, T., Clark, K.F., McKenna, P., Siah, A., Greenwood, S.J., Berthe, F.C.J., Casey, J.W., Cepica, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.01.2012; Elsevier
• Subjects: Animals; Biological and medical sciences; centrifugation; Centrifugation, Density Gradient - methods; clams; disease transmission; electron microscopy; electrophoresis; etiology; filtrates; Fundamental and applied biological sciences. Psychology; genes; Haemic neoplasia; Hematologic Neoplasms - pathology; Hematologic Neoplasms - veterinary; Hematologic Neoplasms - virology; Hemocytes - ultrastructure; Hemocytes - virology; Invertebrates; Marine; Mollusca; Mya - virology; Mya arenaria; Retroviridae; Retroviridae - enzymology; Retroviridae - genetics; Retroviridae - isolation & purification; Retroviridae Infections - diagnosis; Retroviridae Infections - veterinary; Retroviridae Infections - virology; Retrovirus; Reverse transcriptase activity; reverse transcriptase polymerase chain reaction; Reverse Transcriptase Polymerase Chain Reaction - veterinary; RNA; RNA, Viral - analysis; RNA, Viral - genetics; RNA-directed DNA polymerase; RNA-Directed DNA Polymerase - genetics; RNA-Directed DNA Polymerase - metabolism; RT-PCR; shell (molluscs); sucrose; Sucrose gradient; tissues; viruses; Mya arenaria; Retrovirus; Haemic neoplasia; Sucrose gradient; Reverse transcriptase activity; RT-PCR; Reverse transcription; Activity; Bivalvia; Invertebrata; Mollusca; Detection; Reverse transcription polymerase chain reaction
• ISSN: 0022-2011; 1096-0805; 1096-0805
• DOI: 10.1016/j.jip.2011.10.008

[Display omitted] ► Whole tissues of both HN+ve and HN−ve animals were exposed to sucrose gradient. ► The fractions with highest RT activity were exposed to RNA, protein, and EM analysis. ► There was no evidence for existing of a putative retrovirus. ► RT-PCR using universal primers of retroviruses was negative in all tested samples. Haemic neoplasia (HN) is a leukemia-like disease that affects at least 20 species of marine bivalves including soft shell clam, Mya arenaria. Since the disease was discovered in 1969, the etiology remains unknown. A retroviral etiology has been suggested based on the detection of reverse transcriptase activity and electron microscopic observation of retroviral-like particles using negative staining. To date, however no virus isolate and no retroviral sequence from HN has been obtained. Moreover, transmission of the disease by cell-free filtrate from affected clams has not been reproduced. In the current study, we reinvestigated the association of HN with a putative retrovirus. Sucrose gradient centrifugation followed by assessment of reverse transcriptase activity, electrophoretic analysis of protein and RNA, and electron microscopic examinations of fractions corresponding to retroviral density were employed. Detection of retroviral pol sequences using degenerate RT-PCR approaches was also attempted. Our results showed visible bands at the expected density of retrovirus in HN-positive and HN-negative clam tissues and both with reverse transcriptase activity. Electron microscopy, RNA analysis, protein analysis, and PCR systems targeting the pol gene of retroviruses did not however provide clear evidence supporting presence of a retrovirus. We point out that the retrovirus etiology of HN of Mya arenaria proposed some 25years ago should be reconsidered in the absence of a virus isolate or virus sequences.