ABSTRACT
Brucellosis is a zoonotic disease that causes animal and human diseases. Vaccination is a major measure for prevention of brucellosis, but it is currently not possible to distinguish vaccinated animals from those that have been naturally infected. Therefore, in this study, we constructed the Brucella (B.) abortus 2380 wbkA mutant (2308DeltawbkA) and evaluated its virulence. The survival of 2308DeltawbkA was attenuated in murine macrophage (RAW 264.7) and BALB/c mice, and it induced high protective immunity in mice. The wbkA mutant elicited an anti-Brucella-specific immunoglobulin G response and induced the secretion of gamma interferon. Antibodies to 2308DeltawbkA could be detected in sera from mice, implying the potential for use of this protein as a diagnostic antigen. The WbkA antigen would allow serological differentiation between infected and vaccinated animals. These results suggest that 2308DeltawbkA is a potential attenuated vaccine against 16M. This vaccine will be further evaluated in sheep.
Subject(s)
Animals , Humans , Mice , Antibodies , Brucella abortus , Brucella , Brucellosis , Immunization , Immunoglobulin G , Interferons , Macrophages , Sheep , Staphylococcal Protein A , Vaccination , Virulence , ZoonosesABSTRACT
Objective To determine the difference of macrophage RAW264.7 apoptosis induced by Brucella melitensis virulent strain 16M and attenuated strain M5-90 and elucidate the regulatory role of caspases 3,8 and 9.Methods The best multiplicity of infection (MOI) was determined through kinetic analysis of Brucella melitensis strain 16M and M5-90 induced mouse macrophages apoptosis(bacterium ∶ cell =100 ∶ 1,50 ∶ 1,10 ∶1).The infection model was established using the best MOI =50 ∶ 1.The numbers of in vivo bacteria by colony formation units were calculated after macrophages were infected for different times,including 2,4,8,12,24 and 48 h,and the infected cells were collected.The ratios of apoptosis were detected and the regulation of caspases 3,8 and 9 in apoptosis pathway was elucidated by flow cytometry.Results The numbers of 16M in vivo bacteria were 105.4,104.8,105.8,106.5,108.0 and 109.0,respectively and of M5-90 were 106.1,106.2,106.4,106.3,106.1 and 105.0,respectively.The number of in vivo bacteria of 16M was significantly increased than that of M5-90 after infected for 24 h to 48 h.The ratios of apoptosis induced by 16M after infected for 2,4,8,12,24 and 48 h was (2.67 ± 0.09)％,(13.13 ± 0.30)％,(6.56 ± 0.42)％,(6.49 ± 0.28)％,(16.07 ± 0.86)％ and (24.23 ± 1.67)％,respectively,and by M5-90 was (3.62 ± 0.02)％,(32.01 ± 2.59)％,(17.58 ± 0.44)％,(16.09 ± 0.10)％,(62.53 ± 2.70)％ and (85.53 ± 0.15)％,respectively,and by control group was [(1.90 ± 0.20)％,(1.92 ±0.16)％,(1.99 ± 0.03)％,(2.48 ± 0.11)％,(3.56 ± 0.07)％,(5.26 ± 0.33)％].The differences were statistically between groups in same time.The Brucella melitensis vaccine strain M5-90 was more powerful than virulent strain 16M in respect of inducing macrophage apoptosis after infected for 24 to 48 h.Twenty-four hours after infection,the expression of caspases 3,8 and 9 was (1.47 ± 0.05)％,(1.52 ± 0.02)％ and (2.47 ± 0.12)％,respectively,in control group and the expression was (9.70 ± 0.46)％,(6.08 ± 0.56)％ and (35.08 ± 1.64)％,respectively,after infected for 24 h induced by M5-90.The expression of caspases 3,8 and 9 was significantly higher than that control group (P ＜ 0.01).Twenty-four hours after given caspases 3,8 and 9 inhibitor,apoptosis rate in control group was (66.72 ± 1.28)％,in M5-90 group was (22.58 ± 0.55)％,(53.15 ± 1.85)％ and (29.18 ± 0.23)％,respectively,and compared with control group,apoptosis rate of caspases 3,8 and 9 was significantly lower(P ＜ 0.01).Conclusions Apoptosis of macrophage can be induced by Brucella melitensis virulent vaccine strain 16M and attenuated strain M5-90.M5-90 is stronger than that of strain 16M.Caspases 3,8 and 9 can regulate macrophage apoptosis after M5-90 infection.
ABSTRACT
Objective To construct the bp26 deletion mutant of Brucella vaccine strain M5-90 (M5-90Δbp26),to compare its immunogenicity with parental strain(M5-90),and to develope a new candidate vaccine strain of Brucella melitensis with reduced virulence that can be used to distinguish vaccinated livestock from infected animals.Methods Mutant vaccine strain of Brucella melitensis was constructed by conventional molecular biology techniques then the genetic stability of mutant M5-90Δbp26 was tested and its conventional bacteriological nature was identified; 1.0 × 109 CFU/2 ml doses of M5-90Δbp26 strain and the parental strain were used to vaccinate 3 sheep; sera were analyzed for reactivity against BP26 by Western blotting and for agglutination activity; to analyze the virulence of mutant and parental strain,mice were injected with 1.0 × 106,6.0 × 106 and 2.0 × 107 CFU/0.2 ml doses of M5-90 and M5-90Δbp26,respectively,and clinical symptoms were monitored and the death of mice was recorded.Results The M5-90Δbp26 was successfully generated and reversion was not observed in 15 generations.The size of PCR products was 629 bp while the parental strain was 1279 bp.The sequence analysis showed a 650 bp missing in M5-90Δbp26.The conventional bacteria identification tests confirmed that the mutant was depth variant strain,including mono-specific antiserum M type transformed into R,and the BK2 phage based splitting assay converted from the positive to the negative.Western blotting showed the purified BP26 protein was recognized by the serum against the parental strain while not by the serum against M5-90Δbp26 strain.Agglutination test showed the level of the serum antibody induced by M5-90Δbp26 strain(1:50) was significantly lower than that of serum induced by parental strain(＞ 1:800).Virulence test showed that M5-90Δbp26 strain was less virulent than parental strain.Conclusions M5-90Δbp26 has been successfully constructed.M5-90Δbp26 of Brucella melitensis has the characteristic of reduced virulence and has a potential as brucellosis candidate vaccine strain permitting serological discrimination between diseased and vaccinated livestock.
ABSTRACT
Objective To develop a BP26 recombinant BCG (rBCG-BP26) vaccine,and to observe the effects of rBCG-BP26 on CD4+,CD8+ T cells in immunized mice.Methods The recombinant shuttle vector pMV261-Ag85B-BP26 was constructed by using traditional molecular biological technology.The recombinant strains were obtained by kanamycin resistance screening and PCR identification after electroporation.Western blotting was used to detect the expression of recombinant BP26 vaccine in immunized mice.Safety experiment was carried out in three different groups:the target experiment(rBCG-BP26) group,the positive control(BCG) group and the negative control(PBS) group,15 BALB/c mice in each group.Intradermal inoculations of 100 μl rBCG-BP26 [containing 106 colony forming units(CFU)],BCG,and PBS were carried out,respectively.Signs of mice in each group were observed.After immunization for 10,20,30,and 40 days,body weight was weighed,and tail blood was collected to observe the change of peripheral blood CD4+ and CD8+ T cells by flow cytometry.Results The rBCG-BP26 was successfully constructed.The expression of BP26 protein was detected in the liquid medium and the bacteria cells.The results of safety test analysis showed that there were no significant differences in signs and body weights(F=2.468,0.331,1.520,0.739,all P＞ 0.05),between PBS group[ (19.24 ± 0.54),(21.37 ± 0.66),(22.83 ± 0.62),(25.06 ± 0.37)g],BCG group[ (19.90 ± 0.02),(21.53 ± 1.57),(21.95 ± 0.55),(24.70 ± 0.39)g]and rBCG-BP26 group[ (19.16 ± 0.55 ),(20.89 ± 0.20),(22.15 ± 0.76),(24.60 ± 0.64)g].The results of flow cytometry showed that the percentages of CD4+ T cell level were lower in BCG group(26.70％,33.07％) and rBCG-BP26 group( 13.40％,26.70％) than that of the PBS group(33.85％,29.33％) and the values of CD4+/CD8+ T cells increased in rBCG-BP26 group (0.69％,1.27％,1.57％,1.70％ ) 10,20 and 30 days after immunization.Conclusions Recombinant BCG-BP26 vaccine strain can express brucella BP26 protein efficiently.Furthermore,its virulence is mild,and it can activate CD4+,CD8+ T cells in the body.It can be used as one of candidate vaccine strain against brucellosis.