| Porcine reproductive and respiratory syndrome (PRRS) is an acute infectious disease of swine characterised by respiratory problems in young pigs and reproduction problems like abprons, stillbirths and high mortality of weak piglets, immunosupression and persistent infection.. The causative agent is PRRS virus (PRRSV). In May 2006, highly pathogenic (HP) PRRS attacked the swine industry of Jiangxi province, China, with the characteristics of high morbidity and mortality in pigs of all ages. The disease spread rapidly to most of the provinces in China, resulting in more than one million deaths in pigs. The causative agent was the HP-PRRSV. The immune system is a double edged sword for PRRSV infection, it can provide a site for viral replication but also can offer defence mechanisms that protects against the disease and thus contributes both to the "disease process and protection from disease. PRRSV and its associated porcine reproductive and respiratory syndrome (PRRS) appear to represent a relevant and highly problematic infectious disease in the veterinary situation, particularly as it relates to Asia and China. Veterinary vaccine development for PRRSV has been problematic and no effective standard vaccine candidates have been effective to date. In our study, we investigated the immune organs lesion and immune responses of piglets infected with HP-PRRSV (HuN4 strain) with or without the immunization with CH-1R attenuated PRRSV vaccine, the role of the monoclonal anti-idiotypic antibody (Mab2-5G2) specific for anti-GP5 antibody in regulating the immune responses before vaccination against HP-PRRSV infection and a potential PRRSV receptor preliminary study on the immune founction of NMHCⅡ-A for PRRSV infection.1,Compromise of immune organs in pigs infected with highly pathogenic porcine reproductive and respiratory syndromePRRSV infection compromises the host's innate and adaptive immunity. The aim of this study was to investigate the immune responses of piglets infected with HP-PRRSV (HuN4 strain) with or without the immunization with CH-1R attenuated PRRSV vaccine. The response were evaluated for the clinical signs, pathological changes and virus load in immune organs, antibody responses and levels of serum IFN-γ, IL-4 and IL-10. The result showed that in comparison with the piglets received the immunization, the piglets infected with HP-PRRSV alone had the thymus atrophy, decreased serum levels of IL-4 and increased serum levels of IL-10 and INF-y. These results suggest that elevated IL-10 levels at the early stage of the infection may enhance virus survival and delay the induction of protective immunity, while increased levels of IL-4 induce the effective immune responses and increase the animals' health status.2,Anti-idiotype immune regulation against highly pathogenic PRRSV infectionOur previous studies demonstrated that pigs infected with PRRSV produced auto-anti-idiotypic antibodies (auto-Ab2s) against idiotypic antibodies to M and GP5 protein, which may up- or down-regulate the immune responses against PRRSV infection. The objectives of this study were to examine the ability of Mab2-5G2 in regulating immune responses against HP-PRRSV infection. PRRSV negative pigs were given Mab2-5G2 or control IgG (0.5,1,3 or 5mg/pig) or PBS at 0 DPI and then infected with the virus at 14 DPI or 0 DPC. Clinical observation, rectal temperature, serum antibodies and cytokines were examined for all pigs. The results showed that Mab2-5G2 as the immune regulator at dosage of 0.5-1mg/pig can increase more than 50% of survival of pig after HP-PRRSV infection. Mab2-5G2 up-regulated IL-4 in the PRRSV-negative pigs between 3-7 DPC, induced elevation of antibodies against PRRSV membrane proteins at 14 DPC. Elevated IL-4 after early stage of PRRSV infection could help pig quickly develop the adaptive immunity against PRRSV infection. Pigs received higher dosages of Mab2-5G2 had the similar results as that received control IgG or PBS, maybe higher dosages of Mab2-5G2 induced immune suppression and can not regulate the immune network against HP-PRRSV infection efficiently.3,Anti-idiotype regulation of PRRSV vaccination against HP-PRRSV infectionIn this study, we investigated the role of the monoclonal Ab2 (Mab2-5G2) specific for anti-GP5 antibody in regulating the PRRSV vaccination against HP-PRRSV (HuN4 strain) infection by evaluation of the clinical signs, pathological changes of immune organs, viremia, antibodies against PRRSV and the levels of serum cytokines. Piglets received lmg/piglet of Mab2-5G2 and vaccination produced higher levels of IL-2 and IL-4. After HP-PRRSV infection, these animals demonstrated obvious clinical signs and pathological lesions of the organs including severe thymus atrophy. These results strongly suggest that when Ab2s specific for anti-GP5 antibodies are present due to PRRSV infection, vaccination against PRRSV do not provide effective protection but impair the immune system and increase the PRRSV pathogenecity.4,Preliminary study on the immune founction of non-muscle myosin heavy chain II-A in PRRSV infectionThe objectives of this study were to examine the immune founction of non-muscle myosin heavy chainⅡ-A (NMHCⅡ-A) in PRRSV infection. Mab2-5G2-TRITC was used to strain the peripheral blood lymphocytes and PRRSV negative pigs were given expressed NMHC II-A at 0 and 14 DPI and then infected with the virus at 28 DPI or 0 DPC. Clinical observation, rectal temperature, serum antibodies and cytokines were examined for all piglets. The results showed that NMHCⅡ-A existing in all peripheral blood lymphocyte. After HP-PRRSV infection, these animals demonstrated obvious clinical signs and pathological lesions of the organs including severe thymus atrophy, decreased the serum levels of IFN-γ, IL-2, IL-4 and IL-10 and suppressed production of antibodies against PRRSV compared to the piglets infected with HP-PRRSV only. These results strongly suggest that NMHC II-A related to the immune responses against PRRSV infection. |
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