Clinical efficacy of the acyclic nucleoside phosphonate 9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine (PMPDAP) in the treatment of feline immunodeficiency virus-infected cats

Role of Feline Immunodeficiency Virus in Lymphomagenesis--Going Alone or Colluding?

Feline immunodeficiency virus (FIV) is a naturally occurring lentivirus of domestic and nondomestic feline species. Infection in domestic cats leads to immune dysfunction via mechanisms similar to those caused by human immunodeficiency virus (HIV) and, as such, is a valuable natural animal model for acquired immunodeficiency syndrome (AIDS) in humans. An association between FIV and an increased incidence of neoplasia has long been recognized, with frequencies of up to 20% in FIV-positive cats recorded in some studies. This is similar to the rate of neoplasia seen in HIV-positive individuals, and in both species neoplasia typically requires several years to arise. The most frequently reported type of neoplasia associated with FIV infection is lymphoma. Here we review the possible mechanisms involved in FIV lymphomagenesis, including the possible involvement of coinfections, notably those with gamma-herpesviruses.

Clinical efficacy of melittin in the treatment of cats infected with the feline immunodeficiency virus

OBJECTIVE

The bee venom melittin shows an antiviral efficacy against the human immunodeficiency virus in cell culture. It was shown to be non-toxic for cats. Aim of this pilot study was to investigate the clinical efficacy and side-effects of melittin in cats naturally infected with feline immunodeficiency virus (FIV).

MATERIAL AND METHODS

The study was performed as a prospective, placebo-controlled double-blinded trial. Twenty cats were included, of which 10 cats each were treated with either melittin (500 µg/kg body weight) or phosphate-buffered saline (placebo) subcutaneously twice per week. During the treatment period of 6 weeks, the cats' general health status, determined by the Karnofsky's score, and the severity of clinical signs (conjunctivitis and stomatitis) using a clinical scoring system were evaluated. Haematology, biochemistry profiles, lymphocyte subpopulations, CD4/CD8 ratio, and pterines (biopterine, 7-xanthopterine) as surrogate parameters were also compared.

RESULTS

The general health status and the clinical scores for conjunctivitis and stomatitis improved in cats treated with melittin. A statistically significant improvement however could only be detected for conjunctivitis in cats treated with melittin compared to cats treated with placebo which was likely due to different scores between both groups at the beginning. No influence on the lymphocyte subpopulations, CD4/CD8 ratio, and pterine concentrations was observed. No side effects occurred in this study.

CONCLUSION AND CLINICAL RELEVANCE

In the protocol used in the present study, no significant efficacy of melittin could be detected. However, efficacy of melittin, especially if applied in a higher dosage as in the present study or for a longer period, could be evaluated in further studies. Synergistic effects if used in combination with classic antiretroviral drugs could be an interesting future approach.

Evaluation of a modified Karnofsky score to assess physical and psychological wellbeing of cats in a hospital setting

Objectives The Karnofsky score (KS) modified for cats, a scoring system to rate health and quality of life (QOL) in cats, is used in clinical trials, but its reliability and validity are yet to be determined. The present study aims to evaluate the scientific robustness of the KS when adapted for use in a hospital setting. Methods A list of variables to consider during the physical examination, which informs the clinician's score (CS) part of the KS, was added and clinicians were allowed to choose a score anywhere between 0 and 50. The Karnofsky QOL questionnaire was adapted for use in a hospital setting. F-tests with Bonferroni correction and Spearman rank correlation coefficients were used to evaluate reliability and validity of the KS to assess the health and wellbeing of cats in a hospital setting. The records of 54 feline immunodeficiency virus-positive cats, which were recruited for a clinical trial and hospitalised for 6 weeks, were reviewed. Four veterinarians scored the CS, and one veterinarian and a veterinary nurse assessed the QOL score. Results Mean absolute difference between observers was significantly larger for the CS than for the QOL score ( P <0.001) and two veterinarians scored significantly higher than the remaining two veterinarians ( P <0.001). Inter-observer correlation ranged from 0.45-0.75 for the CS. For the QOL score, the absolute difference between observers was small, no significant difference was found between observers and a high degree of inter-observer correlation was noted (r = 0.91). Conclusions and relevance The results indicate low inter-observer reliability for the CS, requiring additional modifications to this part of the KS. The QOL score seems more reliable, and the questionnaire may serve as a reliable tool in the assessment of QOL in cats in a hospital setting. Consequently, further adaptation of the KS is mandatory when simultaneous assessment of both the cat's clinical health and perceived wellbeing is required.

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.