Follow-Up of Viral Parameters in FeLV- or FIV-Naturally Infected Cats Treated Orally with Low Doses of Human Interferon Alpha

Antiviral therapy in cats progressively infected with feline leukaemia virus: lessons from a series of 18 consecutive cases from Australia

BACKGROUND

It is doubtful that any of the treatments proposed for feline leukaemia virus (FeLV) infection are effective, despite the entity being described 60 years ago.

METHODS

Eighteen pet cats with progressive FeLV infections were recruited in Australia. One or more antiviral drugs were trialled in 16 cats, while two FeLV-infected cats were not handleable and served as untreated controls. Six cats were administered RetroMAD1™ only (0.5 mg/kg orally twice daily), a commercially available recombinant chimeric protein with proposed antiretroviral activity. Three cats were administered the integrase inhibitor raltegravir only (10-15 mg/kg orally twice daily), a drug used as a component of highly effective antiretroviral therapy for human immunodeficiency virus (HIV-1) infection. Three cats were administered RetroMAD1™ and raltegravir concurrently, and four cats were administered raltegravir and the reverse transcriptase inhibitor zidovudine (AZT, 5 mg/kg orally twice daily) concurrently. FeLV RNA and p27 antigen loads were measured at two timepoints (T1-2 months and T3-5 months) during therapy and compared to baseline (pretreatment) levels, to assess the response to therapy using linear modelling. The median survival time (MST) of the cats from commencement of FeLV treatment to death was also determined and compared between treatments.

RESULTS

The MST for the 16 FeLV-positive cats which received antiviral therapy was 634 days, while the MST from FeLV diagnosis to death for the two untreated control cats was 780 days. In cats treated with RetroMAD1™, FeLV viral load decreased from T0 to T1-2 months (median viral load reduced from 1339 × 106 to 705 × 106 copies/mL plasma; P = 0.012), but MST was reduced compared to cats not given RetroMAD1™ (426 days vs 1006 days; P = 0.049). Cats treated with raltegravir and AZT had no significant changes in FeLV viral load over time, but p27 antigen load was decreased from T0 to T3-5 months in cats treated with raltegravir (median p27 antigen level reduced from 50.2% to 42.7%; P = 0.005). All other results were not significantly affected by the treatment provided. Importantly, statistically significant and substantial associations were found between age at FeLV diagnosis and survival time (P = 0.046, R2 = 18.6) and between FeLV viral load at T0 and survival time (P = 0.004, R2 = 44.4). Younger cats, and cats with higher levels of pretreatment FeLV RNA, had reduced survival times. Cats treated with RetroMAD1™ were typically younger (median age 2.0 vs 8.0 years), likely explaining the observed reduction in MST. A significant association was found between FeLV viral load and p27 antigen load at T0 (P = 0.015, R2 = 32.9).

CONCLUSIONS

Results from this small case series do not provide convincing support for the use of RetroMAD1™, raltegravir or AZT, alone or in combination, for the treatment of cats progressively infected with FeLV. The changes observed were biologically insignificant. Age and FeLV viral load at diagnosis are useful prognostic markers, and p27 antigen concentration can be used to predict viral load. Larger field trials should be performed examining antiretroviral therapy in FeLV-positive cats with progressive infections, preferably using three or more drugs from at least two classes, as is standard with human antiretroviral therapy. Future studies would be easier in countries with a higher prevalence of FeLV infections than Australia.

BET Inhibitor JQ1 Attenuates Feline Leukemia Virus DNA, Provirus, and Antigen Production in Domestic Cat Cell Lines

Feline leukemia virus (FeLV) is a cosmopolitan gammaretrovirus that causes lifelong infections and fatal diseases, including leukemias, lymphomas, immunodeficiencies, and anemias, in domestic and wild felids. There is currently no definitive treatment for FeLV, and while existing vaccines reduce the prevalence of progressive infections, they neither provide sterilizing immunity nor prevent regressive infections that result in viral reservoirs with the potential for reactivation, transmission, and the development of associated clinical diseases. Previous studies of murine leukemia virus (MuLV) established that host cell epigenetic reader bromodomain and extra-terminal domain (BET) proteins facilitate MuLV replication by promoting proviral integration. Here, we provide evidence that this facilitatory effect of BET proteins extends to FeLV. Treatment with the archetypal BET protein bromodomain inhibitor (+)-JQ1 and FeLV challenge of two phenotypically disparate feline cell lines, 81C fibroblasts and 3201 lymphoma cells, significantly reduced FeLV proviral load, total FeLV DNA load, and p27 capsid protein expression at nonlethal concentrations. Moreover, significant decreases in FeLV proviral integration were documented in 81C and 3201 cells. These findings elucidate the importance of BET proteins for efficient FeLV replication, including proviral integration, and provide a potential target for treating FeLV infections.

Wavy changes in the whiskers of domestic cats are correlated with feline leukemia virus infection

BACKGROUND

Feline leukemia virus (FeLV) is a retrovirus with global impact on the health of domestic cats and is usually examined by serology. In our daily clinical practice, we noticed that cats infected with FeLV often possess wavy whiskers (sinus hairs on the face). To investigate the relationship between wavy whiskers (WW) and FeLV infection, the association between the presence or absence of wavy changes in whiskers and serological FeLV infection was examined in a total of 358 cats including 56 cats possessing WW, using the chi-square test. The results of blood tests from 223 cases were subjected to multivariate analysis (logistic analysis). Isolated whiskers were observed under light microscopy, and upper lip tissues (proboscis) were subjected to histopathological and immunohistochemical analyses.

RESULTS

The prevalence of WW was significantly correlated with FeLV antigen positivity in the blood. Of 56 cases with WW, 50 (89.3%) were serologically positive for FeLV. The significant association between WW and serological FeLV positivity was also confirmed by multivariate analysis. In WW, narrowing, degeneration, and tearing of the hair medulla were observed. Mild infiltration of mononuclear cells in the tissues, but no degeneration or necrosis, was found. By immunohistochemistry, FeLV antigens (p27, gp70 and p15E) were observed in various epithelial cells including the sinus hair follicular epithelium of the whisker.

CONCLUSIONS

The data suggest that the wavy changes in whiskers, a unique and distinctive external sign on a cat's face, were associated with FeLV infection.

Feline immunodeficiency virus (FIV) infection in domestic pet cats in Australia and New Zealand: Guidelines for diagnosis, prevention and management

Despite the passage of over 30 years since its discovery, the importance of feline immunodeficiency virus (FIV) on the health and longevity of infected domestic cats is hotly debated amongst feline experts. Notwithstanding the absence of good quality information, Australian and New Zealand (NZ) veterinarians should aim to minimise the exposure of cats to FIV. The most reliable way to achieve this goal is to recommend that all pet cats are kept exclusively indoors, or with secure outdoor access (e.g., cat enclosures, secure gardens), with FIV testing of any in‐contact cats. All animal holding facilities should aim to individually house adult cats to limit the spread of FIV infection in groups of animals that are stressed and do not have established social hierarchies. Point‐of‐care (PoC) FIV antibody tests are available in Australia and NZ that can distinguish FIV‐infected and uninfected FIV‐vaccinated cats (Witness™ and Anigen Rapid™). Although testing of whole blood, serum or plasma remains the gold standard for FIV diagnosis, PoC testing using saliva may offer a welfare‐friendly alternative in the future. PCR testing to detect FIV infection is not recommended as a screening procedure since a negative PCR result does not rule out FIV infection and is only recommended in specific scenarios. Australia and NZ are two of three countries where a dual subtype FIV vaccine (Fel‐O‐Vax® FIV) is available and offers a further avenue for disease prevention. Since FIV vaccination only has a reported field effectiveness of 56% in Australia, and possibly lower in NZ, FIV‐vaccinated cats should undergo annual FIV testing prior to annual FIV re‐vaccination using a suitable PoC kit to check infection has not occurred in the preceding year. With FIV‐infected cats, clinicians should strive to be even more thorough than usual at detecting early signs of disease. The most effective way to enhance the quality of life and life expectancy of FIV‐infected cats is to optimise basic husbandry and to treat any concurrent conditions early in the disease course. Currently, no available drugs are registered for the treatment of FIV infection. Critically, the euthanasia of healthy FIV‐infected cats, and sick FIV‐infected cats without appropriate clinical investigations, should not occur.

Management of Severe Oral Inflammatory Conditions in Dogs and Cats

Severe oral inflammatory disease is not uncommon in the mouths of canine and feline patients. An approach to oral diagnosis is offered. This article discusses a brief review of important points in the oral diagnosis and management of main canine (canine chronic ulcerative stomatitis (CCUS), eosinophilic stomatitis, and Wegener's granulomatosis (WG)) and feline diseases (feline gingivostomatitis/caudal stomatitis, oral eosinophilic lesions, pyogenic granuloma, and autoimmune diseases with oral manifestations), and-whereby possible-information about the current understanding of disease pathogenesis and treatment is offered.

Therapeutic and Prophylactic Use of Oral, Low-Dose IFNs in Species of Veterinary Interest: Back to the Future

Cytokines are important molecules that orchestrate the immune response. Given their role, cytokines have been explored as drugs in immunotherapy in the fight against different pathological conditions such as bacterial and viral infections, autoimmune diseases, transplantation and cancer. One of the problems related to their administration consists in the definition of the correct dose to avoid severe side effects. In the 70s and 80s different studies demonstrated the efficacy of cytokines in veterinary medicine, but soon the investigations were abandoned in favor of more profitable drugs such as antibiotics. Recently, the World Health Organization has deeply discouraged the use of antibiotics in order to reduce the spread of multi-drug resistant microorganisms. In this respect, the use of cytokines to prevent or ameliorate infectious diseases has been highlighted, and several studies show the potential of their use in therapy and prophylaxis also in the veterinary field. In this review we aim to review the principles of cytokine treatments, mainly IFNs, and to update the experiences encountered in animals.

Interferon therapies in small animals

Interferons (IFNs) are cytokines that play an important role in the immune response of animals and humans. A number of studies reviewed here have evaluated the use of human, canine and feline IFNs as treatments for infectious, inflammatory and neoplastic disease in dogs and cats. Recombinant canine IFN-γ is deemed an efficacious therapy for canine atopic dermatitis. Recombinant feline IFN-ω is effective against canine parvoviral enteritis and has also been recommended for canine atopic dermatitis. Based on limited evidence, recombinant canine IFN-α could be a topical treatment option for dogs with gingivitis and keratoconjunctivitis sicca. Conclusive evidence is lacking for other diseases and large randomised controlled trials are needed before IFNs can be recommended for other indications.

Clinical and Hematological Follow-Up of Long-Term Oral Therapy with Type-I Interferon in Cats Naturally Infected with Feline Leukemia Virus or Feline Immunodeficiency Virus

Simple Summary

The viruses which produce feline leukemia (FeLV) and feline immunodeficiency (FIV) attack cells involved in the immune response. As specific drugs are either nonexistent, produce secondary effects, or are expensive, a therapeutic possibility is using nonspecific immunostimulants, such as human interferon alpha. We used this drug to treat 27 cats infected by FeLV and 31 infected by FIV. All cats were naturally infected and treatment was administered orally by their owners for four months. Participating cats were evaluated in our clinics at mid-treatment (M2), end of treatment (M4), and 4–8 months after the end of treatment (M10). We observed that treatment was well tolerated by the cats (as it did not affect the liver or the kidney functions), and improved most of the parameters analyzed (clinic, anemia, white cell counts, and CD4+/CD8+ ratio) as long as it was administered. However, 4–8 months after it was discontinued, though most animals remained clinically healthy, many of these parameters had rebounded to initial values or values even worse than the initial values. Thus, more studies should be conducted with longer administration of this drug to evaluate tolerability and sustained improvement of diseases produced by these two viruses which may lead to death.

Abstract

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV), two of the most important pathogens of cats, produce chronic systemic diseases with progressive death of cells involved in the immune response, ultimately leading to death. Immunostimulants is one of the few alternatives to the symptomatic treatment. In this study, 27 naturally FeLV-infected (FeLV+) and 31 naturally FIV-infected (FIV+) cats were administered orally by their owners 60 IU/day of recombinant human interferon alpha (rHuIFN-α) for four months in alternate weeks. Clinical status was evaluated and blood samples collected at four different visits or months (M): pretreatment (M0), mid-treatment (M2), end of treatment (M4), and 4–8 months after end of treatment (M10). Most cats ostensibly improved their clinical status, and many became asymptomatic. rHuIFN-α treatment improved the anemic processes observed at M0 (at least in cats with mild or moderate anemia) and leukocyte counts, including a more favorable CD4+/CD8+ ratio. An increase in the serum gammaglobulin concentration was seen in 80% of the cats. Despite observing an obvious favorable progress in the clinical, biopathological, and CD4+/CD8+ values during treatment, almost invariably all the parameters analyzed worsened after treatment discontinuation (M10), which suggests that the interferon-α protocol should be either extended or include additional cycles for a long-lasting benefit in FeLV+ and FIV+ cats.