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  • Author or Editor: Mary B. Tompkins x
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Summary

Feline leukemia virus and feline immunodeficiency virus (fiv) are lymphotropic retroviruses that cause a wide range of diseases in domestic cats. Although it is known that both viruses are capable of infecting T lymphocytes and that infected cats are lymphopenic, it was not known how infection with either virus might alter specific lymphocyte subpopulations. Using a panel of monoclonal antibodies to feline lymphocyte subpopulations, we examined, by use of flow cytometric analysis, lymphocyte changes in cats naturally infected with FeLV or fiv and explored the early stages in the immunopathogenesis of experimentally induced infection with these viruses. Both groups of naturally infected cats had T-cell lymphopenia. In the fiv-infected cats, the T-cell decrease was principally attributable to loss of CD4+ cells, whereas CD8+ and B-cell numbers remained normal. This led to inversion of the CD4+ to CD8+ ratio in these cats. In contrast, the T-cell lymphopenia in FeLV-infected cats resulted from decrease in CD4+ and CD8+ cells, which led to a CD4+ to CD8+ ratio within normal limits. Experimentally induced infection with these 2 viruses supported these findings. Infection with FIV induced early (10 weeks after infection), chronic inversion of the CD4+ to CD8+ ratio. In contrast, infection with FeLV did not alter CD4+ to CD8+ ratio in the first 20 weeks after infection.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare cytotoxic effects and antiviral efficacy of 9 nucleoside reverse transcriptase inhibitors (NRTIs) against FIV in feline peripheral blood mononuclear cells.

Sample—Peripheral blood mononuclear cells obtained from 3 specific pathogen–free cats.

Procedures—3 of the 9 NRTIs had not been previously assessed in feline cell lines. Cytotoxic effects were determined by colorimetric quantification of a formazan product resulting from bioreduction of a tetrazolium reagent by viable peripheral blood mononuclear cells; uninfected cells from 1 cat were used in these assays. Cells from all 3 cats were infected with a pathogenic clone of FIV, and in vitro antiviral efficacy of each NRTI was assessed with an FIV p24 antigen capture ELISA.

Results—Cytotoxic effects in feline peripheral blood mononuclear cells were observed only at concentrations > 10 μM for all 9 NRTIs. Comparison of the cytotoxic effect at the highest concentration investigated (500μM) revealed that didanosine and amdoxovir were significantly less toxic than abacavir. All drugs induced a dose-dependent reduction of FIV replication. At the highest concentration investigated (10μM), there was no significant difference in antiviral efficacy among the test compounds.

Conclusions and Clinical Relevance—The evaluated NRTIs had low cytotoxicity against feline peripheral blood mononuclear cells and appeared to be safe options for further in vivo evaluation for the treatment of FIV-infected cats. There was no evidence suggesting that the newly evaluated compounds would be superior to the existing NRTIs for reducing FIV burden of infected cats.

Full access
in American Journal of Veterinary Research

Summary

Bronchoalveolar lavage was performed through an endotracheal tube in 34 specific-pathogen-free cats to determine expected values for bronchoalveolar lavage fluid cytologic analysis, using this method of collection. Saline solution for lavage was instilled in 3 separate aliquots at a volume of 5 ml/kg of body weight each. Analysis of sequential aliquots was performed to investigate the differences in cell counts among the 3 fractions. The effect of combining aliquots, including or omitting the first fraction, was evaluated to determine whether all aliquots could be combined for analysis without substantially affecting results.

The total number of nucleated cells retrieved from each cat ranged from 0.9 to 31.1 × 106. Most of these cells were macrophages (78 ± 15%, mean ± sd) and eosinophils (16 ± 14%). The first aliquot had the greatest number of epithelial cells, and the lowest total nucleated cell count and relative and absolute eosinophil counts. Differences among aliquots also were identified for relative and absolute macrophage counts, relative and absolute neutrophil counts, and absolute lymphocyte count. Statistically significant differences were found for many of the cell counts when values from the combination of the second and third aliquots were compared with values from the combination of all 3 aliquots. Magnitude of the differences was small, and these differences were not believed to be of practical consequence.

Free access
in American Journal of Veterinary Research

SUMMARY

Sequential histologic, immunologic, and virologic features of herpesvirus-induced keratitis were studied in 18 experimentally infected cats. Histologic changes were assessed by use of light microscopy, and the presence of viral antigen, B lymphocytes, and T lymphocytes was verified immunohistochemically. Flow cytometry was used to monitor changes in blood T lymphocytes (CD4 and CD8 homologues) and B lymphocytes. Cellular immunity was assessed by use of the lymphocyte proliferation assay. Development of stromal keratitis was preceded by prolonged absence of corneal epithelium, decreased numbers of circulating lymphocyte subsets, decreased mitogen responses, and acquisition of viral antigen by the corneal stroma. Return to normal of circulating lymphocyte numbers and function was temporally associated with the arrival of neutrophils and B and T lymphocytes in the corneal stroma. Sequelae to stromal inflammation were fibrosis and scarring. Findings suggest that suppression of local immune responses allows virus access to the corneal stroma, and that subsequent keratitis is mediated by an immune response to viral antigen.

Free access
in American Journal of Veterinary Research

Objective

To determine whether it was possible to retrieve organisms, by means of bronchoalveolar lavage (BAL), from cats inoculated with Toxoplasma gondii.

Design

Experimental study.

Animals

27 cats. Sixteen of the 27 were experimentally infected with feline immunodeficiency virus.

Procedure

All cats were inoculated with T gondii tachyzoites. Cats were grouped on the basis of feline immunodeficiency virus status and route (IV or intra-arterial) and number of tachyzoites administered. Bronchoalveolar lavage was performed by means of a standard technique. Lavage fluid was evaluated cytologically for tachyzoites.

Results

Clinical signs of toxoplasmosis varied widely among individual cats, but were generally most pronounced in group-1 and -2 cats (n = 5 each) and less pronounced in group-3 (n = 5) cats. Group-4 and -5 cats (n = 6 each) did not have clinical signs of toxoplasmosis. In 14 of the 15 cats in groups 1, 2, and 3, tachyzoites were detected in BAL flu id collected 7 days after inoculation. Tachyzoites were detected 14 days after inoculation in the single cat without tachyzoites 7 days after inoculation. A necropsy was performed on 9 of these cats, and tachyzoites were identified histologically in 4 of the 9. Tachyzoites were not detected in BAL fluid collected 3 days (n = 6) or 7 days (n = 6) after inoculation from the 12 cats in groups 4 and 5. Tachyzoites were not identified histologically in any of these 12 cats.

Clinical Implications

BAL may be useful in the diagnosis of toxoplasmosis. Particularly in cats with signs of pulmonary involvement. (J Am Vet Med Assoc 1997;210:648–650

Free access
in Journal of the American Veterinary Medical Association