Pathology of tumors in fish associated with retroviruses: a review.

Thirteen proliferative diseases in fish have been associated in the literature with 1 or more retroviruses. Typically, these occur as seasonal epizootics affecting farmed and wild fish, and most lesions resolve spontaneously. Spontaneous resolution and lifelong resistance to reinfection are 2 features of some piscine retrovirus-induced tumors that have stimulated research interest in this field. The purpose of this review is to present the reader with the epidemiological and morphological features of proliferative diseases in fish that have been associated with retroviruses by 1 or more of the following methods: detection of C-type retrovirus-like particles or reverse transcriptase activity in tumor tissues; successful tumor transmission trials using well-characterized, tumor-derived, cell-free inocula; or molecular characterization of the virus from spontaneous and experimentally induced tumors. Two of the diseases included in this review, European smelt spawning papillomatosis and bicolor damselfish neurofibromatosis, at one time were attributed to a retroviral etiology, but both are now believed to involve additional viral agents based on more recent investigations. We include the latter 2 entities to update the reader about these developments.

Primary leptomeningeal plasmablastic lymphoma.

Lymphomas that develop in human immunodeficiency virus (HIV) infected patients are predominantly aggressive B-cells lymphomas. The most common HIV-associated lymphomas include Burkitt lymphoma, diffuse large B-cell lymphoma (that often involves the CNS), primary effusion lymphoma, and plasmablastic lymphoma (PBL). Of these, PBL is relatively uncommon and displays a distinct affinity for presentation in the oral cavity. In this manuscript we report a previously undescribed primary leptomeningeal form of PBL in a patient with acquired immunodeficiency syndrome. A 40-year-old HIV positive man presented with acute onset confusion, emesis, and altered mental status. Lumbar puncture showed numerous nucleated cells with atypical plasmocyte predominance. CSF flowcytometry showed kappa restriction with CD8 and CD38 positivity and negative lymphocyte markers, while the MRI showed diffuse leptomeningeal enhancement. As the extensive systemic work-up failed to reveal any disease outside the brain, an en bloc diagnostic brain and meningeal biopsy was performed. The biopsy specimen showed sheets of plasmacytoid cells with one or more large nuclei, prominent nuclear chromatin, scattered mitoses, and abundant cytoplasm, highly suggestive of plasmablastic lymphoma. HIV-associated malignancies have protean and often confusing presentations, which pose diagnostic difficulties posed to the practicing neurological-surgeons. Even in cases where an infectious cause is suspected for the meningeal enhancement, neoplastic involvement should be considered, and cytology and flow-cytometry should be routinely ordered on the CSF samples.

Plasmacytoid leukemia of chinook salmon.

Plasmacytoid leukemia is a common disease of seawater pen-reared chinook salmon (Oncorhynchus tshawytscha) in British Columbia, Canada, but has also been detected in wild salmon, in freshwater-reared salmon in United States, and in salmon from netpens in Chile. The disease can be transmitted under laboratory conditions, and is associated with a retrovirus, the salmon leukemia virus. However, the proliferating plasmablasts are often infected with the microsporean Enterocytozoon salmonis, which may be an important co-factor in the disease.

Preliminary analysis of the polypeptides of the salmon leukemia virus (SLV) and evidence for development of a bimodal viremia following SLV infection.

A retrovirus, known as salmon leukemia virus (SLV), was purified from farm-reared chinook salmon (Oncorhynchus tshawytscha) with plasmacytoid leukemia (PL). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of purified SLV revealed the presence of 9 virus-associated polypeptides with molecular weights from 82 kDa to 15 kDa. Endoglycosidase digestion and alcian blue staining of viral polypeptides separated by SDS-PAGE, and immunoprecipitation experiments using hyperimmune antisera suggest that the non-glycosylated 27 kDa polypeptide may represent a capsid-associated protein and the 82 kDa glycoprotein may represent an envelope-associated protein, which appears to be composed of a 67 kDa protein moiety. Fish injected with PL-positive tissue homgenate developed a bimodal viremia, as indicated by the presence of cell-free, virus-associated reverse transcriptase activity and SLV in serum of fish from 1 to 3 wk post-injection and again from 7 wk on through the rest of the study. If horizontal transmission of SLV and PL occurs in infected chinook salmon, it is most likely to occur after the second viremic period begins.