Victorio M. Collado

Evaluation of a novel nested PCR for the routine diagnosis of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV)

Laboratory diagnosis of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) usually involves both viruses, as the clinical signs are similar and coinfection may occur. Serological methods may not represent an accurate diagnosis: maternal antibodies or cross-reactions may give false positive results to FIV, and false negative results may occur in latent FeLV status, or in certain FIV infection stages. A nested polymerase chain reaction (PCR) technique was designed to detect FeLV, FIV and feline endogenous retrovirus simultaneously. The detection of endogenous sequences was considered indicative of successful DNA extraction. The technique was used to diagnose FIV and FeLV in the blood cells of 179 cats. The κ value with the serological data was 0.69 for FeLV and 0.87 for FIV. The joint detection of FeLV and FIV by this novel nested PCR is sensitive, specific, fast and convenient, and its applicability for clinical diagnosis is promising, as the direct evidence of the presence of the virus is more realistic than the indirect data provided by the serological detection.

Use of recombinant interferon omega in feline retrovirosis: from theory to practice.

Abstract Type-I interferons (IFNs) are cytokines that have non-specific antiviral activity, participating mostly in innate defense mechanisms. Their administration has been proposed to treat several viral and immunomediated diseases as an immunomodulatory therapy. Due to its availability, recombinant human interferon-alpha (rHuIFN-α) has been studied in relation to feline retrovirosis, both in vitro and in vivo. However, IFNs are species-specific and antibodies have been shown to develop in response to the high rHuIFN-α doses necessary for an effective therapy. A recombinant feline IFN has been developed, which has been characterized as interferon-omega (rFeIFN-ω), designed to overcome these problems. Nonetheless, very few studies have been undertaken to evaluate its efficacy in cats naturally infected with FIV or FeLV. In an initial study, we here demonstrated that rFeIFN-ω can dramatically improve the clinical condition of infected cats, and induce improvement of hematologic parameters. Minor changes or no change was observed for hypergammaglobulinemia, CD4/CD8 ratio, proviral load, viremia and RT activity, suggesting that the overall effect of IFN was on innate immunity. More studies are needed in order to better understand its in vivo mechanisms.

Effect of Type-I Interferon on Retroviruses

Type-I interferons (IFN-I) play an important role in the innate immune response to several retroviruses. They seem to be effective in controlling the in vivo infection, though many of the clinical signs of retroviral infection may be due to their continual presence which over-stimulates the immune system and activates apoptosis. IFN-I not only affect the immune system, but also operate directly on virus replication. Most data suggest that the in vitro treatment with IFN-I of retrovirus infected cells inhibits the final stages of virogenesis, avoiding the correct assembly of viral particles and their budding, even though the mechanism is not well understood. However, in some retroviruses IFN-I may also act at a previous stage as some retroviral LTRs posses sequences homologous to the IFN-stimulated response element (ISRE). When stimulated, ISREs control viral transcription. HIV-1 displays several mechanisms for evading IFN-I, such as through Tat and Nef. Besides IFN-α and IFN-β, some other type I IFN, such as IFN-τ and IFN-ω, have potent antiviral activity and are promising treatment drugs.

El sistema inmune innato I: sus mecanismos

El sistema inmune innato surgio muy tempranamente en la evolucion y, con escasas variaciones, es el que defiende a la mayoria de los animales de las agresiones externas, aunque se suele prestar mas atencion a la inmunidad adaptativa. En esta revision se repasan aspectos tales como las similitudes y diferencias entre los sistemas inmunes innato y adquirido, el reconocimiento de los patogenos y los mecanismos que se desencadenan para eliminarlos, empezando por la activacion del complemento que dispara una serie de respuestas, y la fagocitosis, que mejora tambien tras activarse el complemento. Ademas, el sistema inmune innato ha evolucionado para colaborar con el adquirido, y sin esta colaboracion apenas se formarian anticuerpos ni se daria la denominada respuesta inmune de base celular. En conclusion, el sistema inmune innato es un pilar fundamental en el mantenimiento de la integridad del organismo.

El Sistema Inmune Innato II: la primera respuesta frente a la infección

El desencadenamiento de una enfermedad en un animal no se debe unicamente a la invasion de un agente patogeno, sino que el estado inmune del individuo es decisivo. La inmunidad innata es la primera respuesta de un animal frente a un microorganismo extrano, mediante la cual se intenta eliminar la infeccion o contenerla hasta la aparicion de una respuesta inmune mas especifica y eficaz, la inmunidad adaptativa. Los principales componentes de la inmunidad innata son las barreras fisicas, quimicas y biologicas, las celulas fagocitarias, ciertos linfocitos y celulas asesinas naturales o NK (Natural Killer) y factores solubles, que incluyen los componentes del complemento y las citoquinas que median la fagocitosis y la inflamacion. La respuesta inmune innata es inespecifica, es decir carece de memoria inmunologica y se desarrolla por mecanismos inespecificos, incapaces de distinguir las diferencias antigenicas de los diferentes tipos de microorganismos. Ademas de los procesos inflamatorios de forma localizada, existe una respuesta general para proteger el cuerpo en su conjunto, la “respuesta de fase aguda”, coordinada por las citoquinas secretadas por macrofagos, con la que se crean las condiciones organicas mas adecuadas para luchar contra los distintos patogenos. Pero, ademas de esta respuesta generalizada frente a diferentes agentes extranos, va a producirse una respuesta innata caracteristica frente a cada tipo de patogeno (bacterias y sus productos, hongos, virus, y parasitos).