Studies On The Biological Characteristics And Immune Effect To Channel Catfish(Ictalurus Punctatus) Of Outer Membrane Proteins From Stenotrophomonas Maltophilia

The outer membrane proteins(OMP) of S.Maltophilia were extracted by the sarkosyl method and their density were detected with Brandford.The SDS-PAGE analysis showed that the molecular weight of OMP were between 14.2K.D-78.3KD,which concluded four main protein bands for 14.2KD,15.9KD,34.5KD,61.5KD and two lesser bands for 31.8KD,78.3KD.In the acute toxicity test,the half lethal dose(LD₅₀) of S.Maltophilia OMP to I.Punetaus was detected as 9.6mg/kg body weight,but harmless to fish when the dose reduced to 3mg/kg body weight.I.Punetaus were peritonealy injected with S.maltophilia OMP and formalin killed cells(FKC) twice in 0d and in 28d.The immune effect of the two immunogens were compared by examing the agglutinating antibody titers of serum,eight nonspecific immune indexs as the phagocytic activity of leucocytes,the bactericidal index of phagocytes, contents of alexine C₃,IgM,lysozyme,total protein,albumin and SOD activity in serum and relative percent survival(RPS) by challenging with live 50LD₅₀ S.maltophilia in 56d.The results showed that:S.maltophilia OMP had more remarkable nonspecific immunostimulative effect than FKC which displayed better in all indexs except the phagocytic activity of leucocytes during the whole test time.And OMP had better passive.immunoprotection, which could protect 60%I.Punetaus from bacterial attack,5%higher than FKC.To compare the immune enhancement effect of Ficuscaricapolysaccharide(Fcps), Propolis(Pro) and Glycyrrhizine(Gly) to S.maltophilia OMP,I.Punetaus were given with OMP,OMP+Fcps,OMP+Pro and OMP+Gly respectively by the same immune way as above.After immunization,the eight immune indexs and RPS same as above were also detected.The results showed that:among the thress adjuvants,Pro displayed the best immune enhancement effect,which could strengthen the nonspecific immunity,immunogenicity and immunoprotection of OMP.OMP+Pro group displayed best in all nonspecific immune indexs except the phagocytic activity of leucocytes,and had the highest anti-S.maltophilia antibody titer and RPS(73.33%).Gly and Fcps also could strengthen the nonspecific immunity and immunogenicity of OMP.In the examing indexs of the lysozyme and SOD activity in serum,OMP+Gly group and OMP+Fcps group mostly displayed better than OMP group.Besides,OMP+Gly group and OMP+Fcps group could seperately protect 66.67%and 61.67%I.Punetaus from bacterial attack,6.67%and 1.67%higher than OMP group.