The role of viruses in the development of ocular tumors

Ocular manifestations of feline viral diseases

Feline viral diseases are common and cats can be presented with a variety of clinical manifestations. Ocular disease associated with viral pathogens is not unusual, particularly with viruses causing upper respiratory tract disease in cats, such as feline herpesvirus type 1 and feline calicivirus. These agents mainly cause ocular surface disease. Other viruses, such as feline immunodeficiency virus and feline coronavirus, can cause uveitis, while feline leukemia virus can induce ocular lymphosarcoma. This review covers the most common viral pathogens of cats that cause ocular manifestations, the specific features of the ocular diseases caused by these viruses and therapeutic recommendations.

The need for continuous immunosuppression with cyclosporin A to maintain an experimental model of uveal melanoma

We investigated the need for continuous immunosuppression to maintain experimental tumours derived from human uveal melanoma cells implanted in the choroid of pigmented rabbits. Two groups of pigmented rabbits immunosuppressed with cyclosporin A (CsA) were implanted with human uveal melanoma cells in the suprachoroidal space. After 5 weeks, CsA was discontinued in group 2. Animals were treated with prophylactic antibiotics and examined weekly for tumour growth, weight and secondary effects; blood urea nitrogen levels were measured every two weeks. Autopsies and histopathological studies were performed after death or euthanasia at the end of week 12. The difference between the groups in the development of ophthalmoscopic tumours was not statistically significant 5 weeks after implantation. Tumours in group 1 grew progressively throughout the experiment, whereas group 2 tumours showed marked regression 3-4 weeks after discontinuing CsA. Tumours in group 1 were significantly larger and had greater mitotic activity and showed more ciliary body, optic nerve and extrascleral invasion than tumours in group 2, which showed massive fibrosis, minimal mitotic activity and marked inflammatory cell infiltration. Continuous immunosuppression with CsA seems to be necessary to maintain tumour growth in this experimental model of uveal melanoma.

Feline leukemia virus and feline immunodeficiency virus

Ophthalmic manifestations of FeLV or FIV infection can occur in all ocular tissues and may be manifestations of direct viral effects or secondary to viral-related malignant transformation. Additionally, the manifestations of common feline ophthalmic pathogens may be more severe and poorly responsive to therapy because of the immunosuppressive effects of FeLV or FIV infection. Prompt diagnosis of underlying viral infection in cats with ophthalmic disease is paramount for accurate diagnosis and prognosis and is required for appropriate therapeutic decision making.

Parental age and seasonal variation in the births of children with sporadic retinoblastoma: a mutation-epidemiologic study

Statistical analysis of parental age data from 225 sporadic cases of bilateral retinoblastoma, plus ten sporadic cases of chromosome deletion or translocation involving 13q14 that was identified as of paternal origin, revealed no evidence of paternal or maternal age effect. Parental exposure to ionizing radiation or chemical mutagens, the effect of which is accumulated with advancing age, does not seem to play a major role in the production of germinal mutations at the responsible (RB) locus. Furthermore, analysis of variation in the month of birth of 753 children with sporadic unilateral retinoblastoma did not show any significant deviation from the controls or a cyclic trend. The occurrence of nonheritable retinoblastoma is not likely to be associated with certain viruses such as human adenovirus 12 whose activity varies markedly with season. These results, together with the fairly uniform pattern in the incidence of this tumor among different populations, suggest that most, if not all, cases of sporadic retinoblastoma are caused by some intrinsic biological mechanisms, and not by environmental mutagens that may vary with respect to time and place.