| Interleukin-18(IL-18) is an important cytokine with a variety of biologicalactivity, such as inducing a large number of gamma interferon, stimulatinglymphocyte transforms into lymphoblast, promoting the release of other cytokinesand increasing the cytotoxicity, it plays a very crucial role in cell-mediated immune,resisting virus infection and inhibiting the growth of tumor cells.Phytohemagglutinin (PHA) has a significant effect on stimulating lymphocyteproliferation, and2-deoxyglucose (2-D-G) could inhibit the propagation of the virusdirectly, that lead them has been widely used in the treatment of viral disease. AsNewcastle disease vaccine often failed to cause the response of immune system andnegative infections, atypical Newcastle disease (ND) regular occurs in poultry, killedlarge numbers of chicken, reduced the production of egg and most food was wastefor feeding sick chickens, which brought great economic losses to the poultryindustry. In this study, composite immunostimulants consist of effective dose ofPHA, usual dose of2-D-G and different doses of recombinant chicken IL-18wasprepared, it used to study the effects of immune-enhancing of ND vaccine byvaccinating chickens with ND.7d old chickens were vaccinated with attenuated Newcastle disease vaccine and5h later inoculated composite immunostimulants though administered orally andintramuscular injection, then fed separately, at the age of21d, vaccinated again.10chickens each group were randomly selected every7days after vaccinated, heartblood lymphocytes were separated sterilely and used to measure lymphocytetransformation rate; serum was separated determine the content of interleukin-2(IL-2) and gamma interferon (INF-γ)by ELISA; the level of antibodies in the serumagainst the virus was mensurated by hemagglutination and hemagglutinationinhibition test; chicken executed by cervical dislocation, dissected and weighed its spleen and bursa, weigh and record the weight; The residuary chickens challengeNewcastle disease F48virulent strain by eye and intranasal pathway on35d,observed and record the flocks status and mortality;40days of age the incidence isnot dead chickens treatment compound preparation, observe and record theimprovement rate.The results showed that intramuscular injection with compositeimmunostimulants contains recombinant chicken IL-18protein can significantlyimprove the level of INF-γ and IL-2in the chicken, with the increasing in theamount of IL-18protein, INF-γ and IL-2expresses at a higher level. The content ofINF-γ and IL-2reaches its highest level at7d-14d after immuned, which are43ng/Land70ng/L, and it has been able to maintain a high level at least in the28d.Immunization though oral route with composite immunostimulants containsrecombinant chicken IL-18bacteria can significantly improve the level of INF-γ andIL-2after vaccination. Its content reaches highest level after7d immuned, which are50ng/L and62ng/L, then comes the slight decline. With increasing of content ofrecombinant IL-18strain in the composite immunostimulants, levels of INF-γ andIL-2expression changes little. Both intramuscular injection and oral route withcomposite immunostimulants can significantly improve the lymphocytetransformation rate of the Newcastle disease vaccined chickens, antibody levels andimmune organ index, however, intramuscular injection gets a better effect than oral.Meanwhile, with the contents of recombinant chicken IL-18protein increased, thelymphocyte transformation rate and antibody levels get higher. The average antibodytiters peaked at10.2(log2) in the28d. At the same time, intramuscular injection withcomposite immunostimulants can promote growth of immune organs fastercompared to the oral group and vaccine control group at the early of chickens.This study shows that the composite immunostimulants consist of recombinantchicken interleukin-18, PHA and2-deoxyglucose can significantly enhance theeffect of Newcastle disease vaccine on the induction of INF-γ and IL-2, stimulatinglymphocyte proliferation and transformation, improving the level of antibodiesagainst the virus, promoting immune organ growth rate. It provides a theoreticalbasis for the production and application of new type of immune enhancing agentsand antiviral agents. |
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