Sequence and functional characterization of feline interleukin 2

Intra-tumoral gene delivery of feIL-2, feIFN-gamma and feGM-CSF using magnetofection as a neoadjuvant treatment option for feline fibrosarcomas: a phase-I study

Despite aggressive pre- or postoperative treatment, feline fibrosarcomas have a high relapse rate. In this study, a new treatment option based on immune stimulation by intra-tumoral delivery of three feline cytokine genes was performed. The objective of this phase-I dose-escalation study was to determine a safe dose for further evaluation in a subsequent phase-II trial. Twenty-five client-owned cats with clinical diagnosis of fibrosarcoma - primary tumours as well as recurrences - entered the study. Four increasing doses of plasmids coding for feIL-2, feIFN-gamma or feGM-CSF, respectively, were previously defined. In groups I, II, III and IV these doses were 15, 50, 150 and 450 microg per plasmid and a corresponding amount of magnetic nanoparticles. Two preoperative intra-tumoral injections of the magnetic DNA solution were followed by magnetofection. A group of four control cats received only surgical treatment. Side effects were registered and graded according to the VCOG-CTCAE scale and correlated to treatment. Statistical analyses included one-way anova, post hoc and Kruskal-Wallis tests. ELISA tests detecting plasma feIFN-gamma and plasma feGM-CSF were performed. One cat out of group IV (450 microg per plasmid) showed adverse events probably related to gene delivery. As these side effects were self-limiting and occurred only in one of eight cats in group IV, this dose was determined to be well tolerable. Altogether six cats developed local recurrences during a 1-year observation period. Four of these cats had been treated with dose IV. Regarding these observations, a subsequent phase-II trial including a representative amount of cats should be tested for the efficacy of dose IV as well as dose III.

The role of polymerase chain reaction and its newer developments in feline medicine

We give a brief overview on the principles of the polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR), quantitative competitive PCR and real-time PCR (TaqMan technology). The literature dealing with PCR and its role in the diagnosis, pathogenesis and research of infectious diseases of the domestic cat is reviewed. Cross-contaminations which occasionally occur during handling of amplified DNA may be an important problem in the PCR laboratory. In many infectious diseases, PCR results are difficult to interpret as their predictive positive and negative values are not always known. Newer assays, such as TaqMan procedures, are becoming increasingly reliable and cost-effective. It can be expected that additional knowledge on how to interpret PCR results will soon be available.

Cytokines and anti-cytokine therapy: clinical potential for treatment of feline disease

Cytokines are soluble proteins produced by nucleated cells throughout the body. They have wide ranging effects on cell growth and differentiation, mediating immune responses, haemopoiesis and tissue repair. Advances in recombinant DNA technology have led to a vast increase in knowledge of their biological properties and subsequently their use in human clinical trials. The use of human cytokines in feline medicine has been of limited success as the action of cytokines is often species restricted or their activity may be neutralized due to antibody formation. Recently, however, many feline cytokines have been cloned which raises the possibility of their future use in the management and prevention of feline disease. Ultimately, they may find widespread clinical uses including the treatment of cancer, cytopenias and viral infections and as vaccine adjuvants.

Antibody and cytokine responses in kittens during the development of feline infectious peritonitis (FIP)

Two recombinant FIPV spike proteins were assessed for their immunogenic properties in 8-week-old kittens, which were then challenged intranasally with FIPV 79-1146. Humoral responses were assessed by ELISA and serum neutralisation test. Changes in PBMC cytokine mRNA levels were detected by a reverse transcription, semiquantitative polymerase chain reaction assay (RT-sqPCR), assessing IL-2, IL-4, IL-6, IL-10, IL-12 and IFNgamma. All of the kittens developed clinical signs typical of FIP, which were confirmed on gross post mortem examination. The recombinant proteins induced little or no specific antibody response prior to challenge, and failed to alter the course of disease compared to controls. One week after virus challenge, the stimulated PBMCs showed small increases in the expression of IL-6 and IFNgamma mRNA, which correlated with a transient pyrexia. After this time expression of IL-6 mRNA remained unaltered but, as FIP developed, mRNA levels of IL-2, IL-4, IL-10, IL-12 and IFNgamma became markedly depressed.

Biological response modifiers: interferons, interleukins, recombinant products, liposomal products

The concept of enhancing the normal immune response against infections and neoplasms has been considered for decades. The administration of various natural and synthetic products to simulate systemic infections has largely given over to the idea that specific cytokines can be used effectively when administered systemically. Interferons, interleukins, and hematopoietic growth factors may offer substantial clinical benefit in chronic viral infections, and cancers such as osteosarcoma, melanoma, and lymphosarcoma. Erythropoietin has been shown to have great utility in the management of chronic renal failure. At this point in time, only recombinant products derived from humans are commercially available, and they are expensive and not licensed for use in companion animals. Nevertheless, these products may have significant clinical impact on several highly fatal disorders of dogs and cats. When administered systemically, cytokines perturb complex regulatory pathways, and serious side effects may occur. Innovative delivery methods, such as liposomes, gene therapy, and even oral administration may increase the therapeutic index of these molecules. Biological response modification, cytokine biology, and associated delivery systems are rapidly changing fields, and the small animal veterinarian will need to watch for significant advances in these areas over the next several years.

Bioactivity of recombinant feline interleukin-2 on human and feline leukocytes

Interleukin (IL)-2 is a 16,000 Da protein product of T lymphocytes which is the principle cytokine responsible for clonal expansion of T lymphocytes as a response to antigen exposure. Deficiency of functional IL-2 plays a pivotal role in the pathogenesis of human immunodeficiency syndrome and may be important in the pathogenesis of feline immunodeficiency syndrome as well. Additionally, IL-2 may enhance secretion of interleukin-5 from the TH2 subset of CD4+ T cells, promote peripheral and systemic eosinophilia, and contribute to the eosinophilia which characterizes the inflamed airways of human beings and cats with asthma. We recently reported the sequence of feline IL-2 and the synthesis of recombinant feline IL-2. The purpose of the present study was to evaluate the bioactivity of recombinant feline IL-2 on human and feline leukocytes. We established dose-response relationships between recombinant feline IL-2 and radiolabeled proliferating human and feline leukocytes using thymidine incorporation as a marker of bioactivity. We found that recombinant human IL-2 promotes proliferation of both human and feline leukocytes. However, recombinant feline IL-2 promotes proliferation of feline cells, but not human cells.

A reverse transcription-polymerase chain reaction technique to detect feline cytokine genes

The ability to detect feline cytokine expression would allow further characterization of the feline immune system. Bioassays are currently available for the measurement of feline IL2, IL6 and TNF alpha but not for other biologically important cytokines. To detect the expression of other cytokines, a reverse transcription-polymerase chain reaction (RT-PCR) procedure was developed. Since feline cytokine gene sequences other than TNF alpha were not available, mammalian DNA and mRNA sequences for IL2, IFN gamma, IL4, IL6, IL10, IL12 and beta-actin, obtained from the Genbank database were compared and oligonucleotide primers chosen from consensus sequences. To validate the cytokine and beta-actin primers, peripheral blood mononuclear cells from specific pathogen free (SPF) cats were cultured in the presence of Con A for various periods of time (0-72 h). RNA was collected, reverse transcribed into cDNA, and the cDNA was amplified by PCR with each set of cytokine primer pairs. RT-PCR products were hybridized with specific 32P end-labeled internal oligonucleotide probes and then analyzed with the AMBIS imaging system to determine the kinetics of cytokine mRNA production. The beta-actin signal was used to control for sample to sample variation in the quantity of mRNA and variation in the RT and PCR reactions. Peak mRNA expression for most cytokines was found to occur between 2 to 4 h of Con A stimulation. mRNA expression was correlated with cytokine bioactivity for IL2 and IL6. Peak IL2 bioactivity occurred after 8 h of Con A stimulation, 4 h after the mRNA expression had peaked. Although IL6 mRNA expression peaked between 2 and 4 h of stimulation, bioactivity was not detected until 8 h of stimulation and continued to increase over the next 24-48 h.

The isolation and sequence of canine interleukin-2

A cDNA corresponding to canine IL-2 has been isolated and sequenced. The cDNA was synthesised using RT-PCR, with oligonucleotide primers designed from conserved regions of published IL-2 sequences. The cDNA encodes a predicted full length IL-2 protein of 155 amino-acids. At the nucleic acid level, the canine cDNA shows 92, 88, 88, 82 and 74% homology to published sequences of feline, human, equine, bovine and murine IL-2, respectively. The derived protein shows 90, 86, 85, 76 and 75% similarity to feline, human, equine, murine and bovine IL-2 homologs.