Effects Of Environmental Stress, Chinese Herb Medicine And Gene Transfer On The Non-specific Immune Functions Of Fish

The occurrence of fish disease lies on three factors: the environment, the pathogen and the fish. One of the fish's physiological responses to environmental change is a durative and strong stress response, which may inhibit fish immune functions greatly and increase the susceptibility to kinds of pathogens. In order to avoid the economic losses caused by environmental problem, on one hand, people should reduce the destruction to environment, and on the other hand, efforts should be made to enhance fish immunity and resistance to disease. Then how to accelerate the immune functions of aquacultural fish? There are two methods: one is to add immunstimulant to fish feed, and the other is to improve fish properties using gene transfer technology. The present work firstly investigated the effects of environmental stress on fish immune system, and then chose two kinds of Chinese herb medicine to study their immunostimulative efficacy on fish, and finally, evaluated the effects of growth hormone and lactoferrin gene transfer on fish resistance to disease. The main results are as follows: Environmental Stress Section 1 Crowding stress caused by high raising density (over 35 g·L-1) inhibited fish immune functions notably. Higher density and longer crowding period led to higher mortality. 2 The dynamic change trends of the levels of cortisol and lysozyme were different after chronic (crowding) and acute (handling) stresses. So was their sensitiveness to stress. As for acute stress, the cortisol response was more sensitive than the lysozyme response, and could therefore reflect the stress status of fish more actually. 3 The effects of cortisol on fish immunity should be discussed from two aspects: short term increase of cortisol level (injection without a carrier) enhanced fish immunity and was in favor of overcoming stress; long term increase of cortisol level (injection with a butter carrier) suppressed fish immunity and led to the high susceptibility to microbes. Chinese Herb Medicine Section 1 After fed with Chinese herb medicine at the doses of 3.0%—6.0% during 11 to 18 days, fish showed activated non-specific immunity and high resistance to Aeromonas hydrophila infection. 2 The innate immunity was stimulated and the resistance to Aeromonas hydrophila infection was enhanced, and the endurance to disturbing and oxygen shortage was increased after fish were injected with Acanthopanax senticocus solution ( Dose A1, A2) and fed with Acanthopanax senticocus in basal feed (Dose B1, B2). (Specific doses are under patent protection.) Gene Transfer Section 1 This study indicated that the "all-fish"growth hormone gene transfer could not only speed the growth but also improve the non-specific immune functions of carp. 2 The high resistance to Aeromonas hydrophila　infection of human lactoferrin-transgenic grass carp might be due to the stimulated fish immunity by the expression of lactoferrin gene, not due to the direct bactericidal action of lactoferrin.