Haematological findings in cats naturally infected with feline immunodeficiency virus

Antiviral treatment of feline immunodeficiency virus-infected cats with (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine

Feline immunodeficiency virus (FIV), the causative agent of an acquired immunodeficiency syndrome in cats (feline AIDS), is a ubiquitous health threat to the domestic and feral cat population, also triggering disease in wild animals. No registered antiviral compounds are currently available to treat FIV-infected cats. Several human antiviral drugs have been used experimentally in cats, but not without the development of serious adverse effects. Here we report on the treatment of six naturally FIV-infected cats, suffering from moderate to severe disease, with the antiretroviral compound (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine ([R]-PMPDAP), a close analogue of tenofovir, a widely prescribed anti-HIV drug in human medicine. An improvement in the average Karnofsky score (pretreatment 33.2 ± 9.4%, post-treatment 65±12.3%), some laboratory parameters (ie, serum amyloid A and gammaglobulins) and a decrease of FIV viral load in plasma were noted in most cats. The role of concurrent medication in ameliorating the Karnofsky score, as well as the possible development of haematological side effects, are discussed. Side effects, when noted, appeared mild and reversible upon cessation of treatment. Although strong conclusions cannot be drawn owing to the small number of patients and lack of a placebo-treated control group, the activity of (R)-PMPDAP, as observed here, warrants further investigation.

Clinical findings and survival in cats naturally infected with feline immunodeficiency virus

BACKGROUND

The clinical course and outcome of natural feline immunodeficiency virus (FIV) infection are variable and incompletely understood. Assigning clinical relevance to FIV infection in individual cats represents a considerable clinical challenge.

OBJECTIVE

To compare signalment, hematologic and biochemical data, major clinical problem, and survival among client-owned, FIV-infected, and uninfected domestic cats.

ANIMALS

Client-owned, domestic cats tested for FIV (n = 520).

METHODS

Retrospective, case control study. Logistic regression analyses were conducted to identify risk factors for FIV infection and to compare hematologic and biochemical data between cases and controls, after adjusting for potential confounders. Survival times were compared using Kaplan-Meier curves.

RESULTS

The prevalence of FIV infection was 14.6%. Mixed breed, male sex, and older age were risk factors for FIV infection. Hematologic abnormalities, biochemical abnormalities or both were common in both FIV-infected and uninfected cats. Lymphoid malignancies were slightly more common in FIV-infected than uninfected cats. Survival of FIV-infected cats was not significantly different from that of uninfected cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Multiple hematologic and biochemical abnormalities are common in old, sick cats regardless of their FIV status. Their presence should not be assumed to indicate clinical progression of FIV infection. A negative effect of FIV on survival was not apparent in this study.

Determination of differential cell counts in feline bone marrow by use of flow cytometry

OBJECTIVE

To evaluate the potential usefulness of 2 flow cytometric methods for determination of differential cell counts in feline bone marrow.

SAMPLE POPULATION

10 bone marrow specimens from client-owned cats.

PROCEDURE

Bone marrow specimens were stained with 3,3'-dihexyloxacarbocyanine iodide (DiOC6) and evaluated by use of flow cytometry. Differential counts were also determined by analysis of scatterplots of forward-angle versus side-angle light scatter of unstained specimens, obtained by use of flow cytometry (scatterplot method). Results of both flow cytometric methods were compared with differential cell counts determined by manually counting 1,000 cells on slides of Wright-stained smears.

RESULTS

Staining with DiOC6 resulted in identification of mature and immature erythroid and myeloid cells and lymphocytes. Use of the scatterplot method resulted in identification of mature and immature erythroid and myeloid cells and metamyelocytes. However, to identify lymphocytes by use of the scatterplot method, bone marrow specimens were first labeled with an anti-major histocompatability class-II antibody. Comparison of results of the scatterplot method with manual counts yielded higher correlation coefficients and more similar mean values than did comparison of results of the DiOC6 method.

CONCLUSIONS AND CLINICAL RELEVANCE

The scatterplot method provided more accurate and precise results than the DiOC6 method for determination of bone marrow differential cell counts in cats by use of flow cytometry. When combined with fluorescent labeling of lymphocytes, the scatterplot method has potential to provide rapid semiquantitative assessment of bone marrow differential cell counts in cats.