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.