Deletion of speA and aroC genes impacts the pathogenicity of Vibrio anguillarum in spotted sea bass.

Vibrio anguillarum is one of the major pathogens responsible for bacterial infections in marine environments, causing significant impacts on the aquaculture industry. The misuse of antibiotics leads to bacteria developing multiple drug resistances, which is detrimental to the development of the fisheries industry. In contrast, live attenuated vaccines are gradually gaining acceptance and widespread recognition. In this study, we constructed a double-knockout attenuated strain, V. anguillarum ΔspeA-aroC, to assess its potential for preparing a live attenuated vaccine. The research results indicate a significant downregulation of virulence-related genes, including Type VI secretion system, Type II secretion system, biofilm synthesis, iron uptake system, and other related genes, in the mutant strain. Furthermore, the strain lacking the genes exhibited a 67.47% reduction in biofilm formation ability and increased sensitivity to antibiotics. The mutant strain exhibited significantly reduced capability in evading host immune system defenses and causing in vivo infections in spotted sea bass (Lateolabrax maculatus), with an LD50 that was 13.93 times higher than that of the wild-type V. anguillarum. Additionally, RT-qPCR analysis of immune-related gene expression in spotted sea bass head kidney and spleen showed a weakened immune response triggered by the knockout strain. Compared to the wild-type V. anguillarum, the mutant strain caused reduced levels of tissue damage. The results demonstrate that the deletion of speA and aroC significantly reduces the biosynthesis of biofilms in V. anguillarum, leading to a decrease in its pathogenicity. This suggests a crucial role of biofilms in the survival and invasive capabilities of V. anguillarum.

Generation and characterization of a genetically modified live rabies vaccine strain with attenuating mutations in multiple viral proteins and evaluation of its potency in dogs.

Live rabies vaccines have advantageous features that can facilitate mass vaccination for dogs, the most important reservoirs/transmitters of rabies. However, some live vaccine strains have problems in their safety, namely, risks from the residual pathogenicity and the pathogenic reversion of live vaccine strains. The reverse genetics system of rabies virus provides a feasible option to improve the safety of a live vaccine strain by, for example, artificially introducing attenuating mutations into multiple viral proteins. It was previously demonstrated in separate studies that introduction of amino acid residues Leu at position 333 in the viral glycoprotein (G333), Ser at G194, and Leu/His at positions 273/394 in the nucleoprotein (N273/394) enhance the safety of a live vaccine strain. In this study, to test our hypothesis that combinational introduction of these residues would significantly increase the safety level of a vaccine strain, we generated a novel live vaccine candidate, ERA-NG2, that is attenuated by mutations at N273/394 and G194/333, and we examined its safety and immunogenicity in mice and dogs. ERA-NG2 did not cause any clinical signs in mice after intracerebral inoculation. After 10 passages in suckling mouse brains, ERA-NG2 retained all of the introduced mutations except the mutation at N394 and the highly attenuated phenotype. These findings indicate that the ERA-NG2 is highly and stably attenuated. After confirming that ERA-NG2 induced a virus-neutralizing antibody (VNA) response and protective immunity in mice, we immunized dogs intramuscularly with a single dose (105-7 focus-forming units) of ERA-NG2 and found that, at all of the tested doses, the strain induced a VNA response in dogs without inducing any clinical signs. These findings demonstrate that ERA-NG2 has a high level of safety and a substantial level of immunogenicity in dogs and thus is a promising live vaccine candidate that can facilitate vaccination in dogs.

Safety analysis of children of different ages vaccinated with measles, mumps and rubella combined attenuated live vaccine/measles and rubella combined attenuated live vaccine in Jilin Province from 2015 to 2022 / 中国生物制品学杂志

@#Objective To analyze the safety of children of different ages vaccinated with measles,mumps and rubella combined attenuated live vaccine(MMR in brief)/measles and rubella combined attenuated live vaccine(MR in brief)in Jilin Province from 2015 to 2022.Methods The actual vaccination data of MMR and MR from January 1,2015 to December 31,2022 were collected through the Jilin information management system for immunization programming,and all AEFI case information reported after vaccination with MMR and MR in this period was collected through the national adverse event following immunization(AEFI) monitoring and reporting system.The incidence rates of AEFI reports were compared among8-month-old children vaccinated with the first dose of MMR(MMR 8 group) and MR(MR8 group),18-month-old children vaccinated with the first dose of MMR(vaccinated with MR at 8 months old,MMR18-1 group) and the second dose of MMR(vaccinated with the first dose of MMR at 8 months old,MMR18-2 group) to preliminarily evaluate the safety of children vaccinated with MMR and MR at different ages.Results The reported incidence of AEFI in MMR8,MR8,MMR18-1 and MMR18-2 groups were 374.41/100 000,350.81/100 000,101.70/100 000 and 104.91/100 000,respectively,with significant difference among the four groups(χ~2=1 145.47,P=0.00);There was no significant difference between MMR8 and MR8,as well as MMR18-1 and MMR18-2 groups(χ~2=3.780 and 0.194,respectively,each P> 0.05);There were significant differences between MMR8 and MMR18-1,MMR8 and MMR18-2,as well as MR8 and MMR18-1groups(χ~2=920.440,412.110 and 1 021.120,respectively,each P=0.00).Most of the adverse reactions were general reactions,mainly fever,local redness and induration;A few were abnormal reactions,which were mainly allergic reactions(rash,papules,urticaria,etc.).Only one case of coincidence was reported in MMR8 group,and no psychogenic reaction,vaccine quality accident and vaccination accident occurred.All AEFI turned out to be improved or cured.Conclusion The differences of AEFI reported incidence of 8-month-old children vaccinated with MMR and MR were all small,and the difference of AEFI reported incidence of 18-month-old children vaccinated with the second dose of MMR was small regardless of the initial vaccination with MMR or MR.It is safe to use MMR instead of MR for the first vaccination in8-month-old children.

Research progress on vaccines against human respiratory syncytial virus / 中国生物制品学杂志

@#Human respiratory syncytial virus(hRSV)is one of the main pathogens that cause lower respiratory tract infection in infants and the elderly.hRSV genome contains 10 genes with a full length of 15 222 bp,encoding 11 proteins(9structural proteins and 2 non-structural proteins).Different proteins play different roles in the pathogenesis of hRSV.With the in-depth research on the biological and structural characteristics of hRSV,various types of hRSV vaccines have been developed,making rapid progress.For example,hRSV attenuated live vaccine hRSV ?NS2/?1313/I1314L has entered Phase II clinical trial,and hRSV subunit protein vaccine Pre-F-GCN4t has entered Phase III clinical trial.In this paper,the biological characteristics of hRSV and the types of hRSV vaccines with rapid progress are reviewed so as to provide a reference for the development of hRSV vaccines in China.

Safety enhancement of a genetically modified live rabies vaccine strain by introducing an attenuating Leu residue at position 333 in the glycoprotein.

To improve the safety of genetically modified live rabies vaccine strains, most studies have utilized an attenuating Arg-to-Glu mutation at position 333 in the glycoprotein (G333), which is responsible for attenuation of the live vaccine strain SAG2. The Glu residue requires two nucleotide substitutions to revert to pathogenic Arg, thus significantly lowering the probability of pathogenic reversion caused by the Glu-to-Arg mutation at G333. However, only one nucleotide substitution is sufficient to convert the Glu residue to another pathogenic residue, Lys, and thereby to cause pathogenic reversion. This indicates a potential safety problem of SAG2 and the live vaccine candidates attenuated by Glu at G333. In this study, aiming to solve this problem, we examined the utility of a Leu residue, which requires two nucleotide substitutions to be both Arg and Lys, as an attenuating mutation at G333. Using a reverse genetics system of the live vaccine strain ERA, we generated ERA-G333Leu by introducing an Arg-to-Leu mutation at G333. Similar to ERA-G333Glu, which is attenuated by an Arg-to-Glu mutation at G333, ERA-G333Leu did not cause obvious clinical signs in 6-week-old mice after intracerebral inoculation. Importantly, after 10 passages in suckling mouse brains, ERA-G333Glu acquired a pathogenic Lys or Arg at G333 and a high level of lethality in mice, whereas ERA-G333Leu retained the attenuating Leu at G333 and only showed a modest level of virulence probably caused by a mutation at G194. In addition, ERA-G333Leu and ERA-G333Glu induced neutralizing antibody response and protective immunity in mice with similar efficiencies. The results demonstrate that, compared to ERA-G333Glu, ERA-G333Leu is more stably attenuated, also indicating the high utility of a Leu residue as an attenuating mutation at G333 in the development of live rabies vaccine strains with a high level of safety.

The Analysis of Live-Attenuated Piscirickettsia salmonis Vaccine Reveals the Short-Term Upregulation of Innate and Adaptive Immune Genes in Atlantic Salmon (Salmo salar): An In Situ Open-Sea Cages Study.

Piscirickettsia salmonis, the etiological agent of the Salmon Rickettsial Septicemia (SRS), is one the most serious health problems for the Chilean salmon industry. Typical antimicrobial strategies used against P. salmonis include antibiotics and vaccines, but these applications have largely failed. A few years ago, the first attenuated-live vaccine against SRS (ALPHA JECT LiVac® SRS vaccine) was released to the market. However, there is no data about the agents involved in the activation of the immune response induced under field conditions. Therefore, in this study we evaluated the expression profile of a set of gene markers related to innate and adaptive immunity in the context of a cellular response in Atlantic salmon (Salmo salar) reared under productive farm conditions and immunized with a live-attenuated vaccine against P. salmonis. We analyzed the expression at zero, 5-, 15- and 45-days post-vaccination (dpv). Our results reveal that the administration of the attenuated live SRS LiVac vaccine induces a short-term upregulation of the cellular-mediated immune response at 5 dpv modulated by the upregulation of ifnα, ifnγ, and the cd4 and cd8α T cell surface markers. In addition, we also registered the upregulation of il-10 and tgfß. Altogether, the results suggest that a balanced activation of the immune response took place only at early times post-vaccination (5 dpv). The scope of this short-term upregulation of the cellular-mediated immune response against a natural outbreak in fish subjected to productive farm conditions deserves further research.

Mumps antibody levels after MMR vaccination in a population in Changning District of Shanghai / 上海预防医学

ObjectiveTo evaluate the dosage effect of measles， mumps and rubella combined attenuated live vaccine （MMR） vaccination on seroprevalence of mumps. MethodsA cross-sectional study was conducted among people in Changning District of Shanghai aged 1 month to 19 years old （n=1 816） in Mar.－Sep. 2017. Blood samples were analyzed for mumps antibodies using enzyme-linked immunosorbent immunoglobulin G （IgG） assays. ResultsMumps antibody seropositivity was 94.59% in 2 years old children and maintained at 98.18%-100.00% from 4 to 9 years old. The seropositivity began to decrease since 10 years， and it was 88.33% （95%CI： 81.20%-93.47%） at age of 12 years. In 12-19 years age group， individuals with 3 doses of mumps-containing vaccines had the highest seropositivity （93.88%） and individuals with 1 or 0 doses had the lowest seropositivity （68.75%）. ConclusionTwo-dose MMR immunization in Shanghai induces a sharp increase in mumps antibody levels in the corresponding age groups. The antibody levels decline gradually with time since the second dose. Vaccine dosage is positively associated with mumps IgG seropositivity and geometric mean concentrations （GMC） in 12-19 years old.

Mumps antibody levels after MMR vaccination in a population in Changning District of Shanghai / 上海预防医学

ObjectiveTo evaluate the dosage effect of measles， mumps and rubella combined attenuated live vaccine （MMR） vaccination on seroprevalence of mumps. MethodsA cross-sectional study was conducted among people in Changning District of Shanghai aged 1 month to 19 years old （n=1 816） in Mar.－Sep. 2017. Blood samples were analyzed for mumps antibodies using enzyme-linked immunosorbent immunoglobulin G （IgG） assays. ResultsMumps antibody seropositivity was 94.59% in 2 years old children and maintained at 98.18%-100.00% from 4 to 9 years old. The seropositivity began to decrease since 10 years， and it was 88.33% （95%CI： 81.20%-93.47%） at age of 12 years. In 12-19 years age group， individuals with 3 doses of mumps-containing vaccines had the highest seropositivity （93.88%） and individuals with 1 or 0 doses had the lowest seropositivity （68.75%）. ConclusionTwo-dose MMR immunization in Shanghai induces a sharp increase in mumps antibody levels in the corresponding age groups. The antibody levels decline gradually with time since the second dose. Vaccine dosage is positively associated with mumps IgG seropositivity and geometric mean concentrations （GMC） in 12-19 years old.

[Systematic reviews and evidence quality assessment on effectiveness of 1 dose varicella attenuated live vaccine for healthy children aged 1-12 years in China].

Objective: To assess the effectiveness of 1 dose varicella attenuated live vaccine (VarV) for healthy children aged 1-12 years in China and explore the application of the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) framework in observational studies of vaccine effectiveness (VE). Methods: We searched studies about the VE of 1-dose VarV for children aged 1-12 years in China which published before 2019 and evaluated the quality of the studies by the Newcastle Ottawa Scale (NOS) table. We used Meta-analysis models to obtain the pooled 1-dose VE and that in subgroups by study design, outbreak or not, study quality and age of subjects. The evidences of VEs were rated by means of the GRADE system. Results: Thirty-two studies were included and the pooled 1-dose VE was 75% [95% confidence interval (CI): 68%-80%]. The VE of outbreak studies [VE=66% (95%CI: 57%-73%)] was lower than non-outbreak studies [VE=85% (95%CI: 78%-89%)], and the VE in <6 years old children [VE=84% (95%CI:77%-89%)] was higher than that in ≥6 years old children [VE=60% (95%CI: 51%-68%)]. There was no significant difference in VE among studies with different design and quality. The quality of the evidences of pooled 1-dose VE was"very low", which was downgraded in bias risk and inconsistency and not downgraded in indirectness, imprecision and publication bias. Conclusions: The 1-dose VarV can provide medium level protection for 1-12 years old children in China, but it will decrease significantly for ≥6 years old children, so it is suggested to implement the strategies of two-dose vaccination of VarV in children <6 years old. The GRADE framework can be used in the observational studies of VE and it is suggested that the technical guidelines of observational study should be worked out to improve the overall quality of evidence.

[Progress and analysis on the development of 2019-nCoV vaccine].

As the COVID-19 pandemic is intensifying globally, more and more people are pinning their hopes on the development of vaccines. At present, there are many research teams who have adopted different vaccine technology routes to develop 2019-nCoV vaccines. This article reviews and analyzes the current development and research status of 2019-nCoV vaccines in different routes, and explores their possible development in the future.

Development of a live attenuated duck hepatitis A virus type 3 vaccine (strain SD70).

Duck hepatitis A virus type 3 (DHAV-3) is an important pathogen that causes substantial losses in the Chinese duck industry. DHAV-3 is highly fatal to ducklings and there is no licensed vaccine in China available to reduce DHAV-3 infection. Our goal was to develop a live attenuated vaccine candidate against DHAV-3. A field isolated strain, SD, was attenuated by serially passaging in specific-pathogen-free (SPF) chicken embryos, and it lost its pathogenicity after 40 passages. The 70th passaged strain (SD70), which achieved good growth capacity in chicken embryos with a viral titer of 107.5 ELD50/mL, was chosen to be the live attenuated vaccine candidate. The SD70 strain did not cause clinical signs of disease or mortality in 1-day-old ducklings and showed no virulence reversion after seven rounds of in vivo back passages. The minimum effective dose of SD70 was determined to be 102.5 ELD50 via the vaccination route of subcutaneous inoculation. A single dose of the SD70 provided good protection to susceptible ducklings against the lethal DHAV-3 strain. Compared with the genomic sequence of the parent SD strain, the SD70 had 12 amino acid substitutions, some of which may play a role in virulence attenuation. This study demonstrated that the attenuated SD70 strain is a promising vaccine candidate for the prevention of DHAV-3 infection in China. It exhibited safety, good stability and excellent protection.

Toxoplasma gondii ADSL Knockout Provides Excellent Immune Protection against a Variety of Strains.

Toxoplasma gondii is a protozoan parasite, occurring worldwide, endangers human health and causes enormous economic losses to the Ministry of Agriculture. A safe and effective vaccination is needed to handle these problems. In addition, ideal vaccine production is a challenge in the future. In this study, we knocked out the adenylosuccinate lyase (ADSL) gene and found that the gene reduces the growth rate of T. gondii tachyzoites in vitro under standard growth conditions by plaque or replication experiments. Furthermore, mice that were immunized with tachyzoites of the ME49ΔADSL strain induced 100% protection efficacy against challenge with the type 1 strain RH, type 2 strain ME49 and type 3 strain VEG. All mice that were immunized with ME49ΔADSL had a survival rate of 100% when they were reinfected with wild-type strains, either 30 days or 70 days after immunization, and immunization was also protective against homologous infection with 50 T. gondii ME49 tissue cysts. In addition, the level of Toxoplasma-specific IgG was significantly elevated at 30 and 70 days after immunization. ME49ΔADSL induced high levels of Th1 cytokines (interferon gamma (IFN-γ), interleukin (IL)-12) at 4 weeks after immunization and spleen cell cultures from mice vaccinated for 150 days were able to produce robust INF-γ and IL-12 levels in the supernatant. The results of the present study showed that ΔADSL vaccination induced a T. gondii-specific cellular immune response against further infections. These results suggest that the ADSL-deficient vaccine can induce anti-Toxoplasma gondii humoral and cellular immune responses and has 100% immune protection against post-challenge by the type 1 strain RH, type 2 strain ME49 and type 3 strain VEG. It will be used as an excellent candidate for live vaccines and may contribute in a positive meaning to control human toxoplasmosis.

Analysis on the loss coefficient of bivalent live attenuated oral polio vaccine in Hongshan District of Wuhan City / 公共卫生与预防医学

Objective To analyze the loss coefficient of bivalent live attenuated oral polio vaccine（bOPV) in Hongshan District, and understand the causes and influencing factors, and to provide a basis for scientifically formulating vaccine use plans and regulating vaccine management. Methods Using the data of Hubei Province Immunization Planning Information System and Hongshan District Vaccination Storage and Management System, a special questionnaire was designed to understand the vaccination and use of bOPV in various immunization units in Hongshan District. A descriptive statistical analysis method was used to calculate the loss coefficient. Results The bOPV loss coefficient of 25 vaccination units in Hongshan District was 1.69. The difference of the loss coefficient between the out-patient clinics of the District Health and Family Planning Committee（1.35）and the community clinics undertaken by large hospitals (2.01）was statistically significant. The difference of the loss coefficient between the inoculation once a week（1.57）and 2-6 times per week（1.94）was statistically significant. In terms of vaccine-disabled time, the two groups of 4 hours had different calculated loss coefficients 1.86 and 1.61, respectively, and the difference was statistically significant. Multivariate regression analysis of the factors related to the loss coefficients found that different outpatient attributes had a greater impact on the loss coefficient than the inoculation cycle and the number of inoculation stations. The loss coefficient for 2016 and 2017 was 2.09 and 1.75, respectively. The difference was statistically significant. Conclusion The management and use of live attenuated bivalent polio vaccine in Hongshan District was relatively standardized. The vaccine loss can by further reduced by strengthening supervision and assessment, setting up centralized vaccination and standardizing publicity and training.

Progress and analysis on the development of 2019-nCoV vaccine / 生物医学工程学杂志

As the COVID-19 pandemic is intensifying globally, more and more people are pinning their hopes on the development of vaccines. At present, there are many research teams who have adopted different vaccine technology routes to develop 2019-nCoV vaccines. This article reviews and analyzes the current development and research status of 2019-nCoV vaccines in different routes, and explores their possible development in the future.

Adverse events following immunization of measles,mumps and rubella,ormeasles and rubella combined attenuated live vaccine among8-month-old children in Jiaxing / 预防医学

Objective@#To analyze the surveillance of adverse event following immunization (AEFI) among 8-month-old children in Jiaxing who received measles, mumps and rubella combined attenuated live vaccine (MMR) or measles and rubella combined attenuated live vaccine (MR) , so as to provide support for the adjustment of vaccine immunization strategy.@*Methods @#The AEFI information of MR (December 1, 2016 to April 30, 2018) and MMR (December 1, 2018 to April 30, 2020) was collected through National AEFI Monitoring Information Management System to compare the incidence, clinical features, occurred time of AEFI as well as combined vaccination.@*Results@#Totally 94 287 doses of MR and 79 994 doses of MMR were administered, 145 and 156 cases of AEFI were reported, and the incidence rate was 15.38/10 000 after MR vaccination, which was lower than 19.50/10 000 after MMR vaccination (P<0.05). Most reported AEFI were abnormal reactions, with 93 cases (11.63/10 000) after MR vaccination and 101 cases (10.71/10 000) after MMR vaccination, among which 72 cases (7.64/10 000) and 76 cases (9.50/10 000) respectively had allergic rash. The AEFI cases mainly occurred less than one day after vaccination, with 113 cases (77.93%) after MR vaccination and 125 cases (80.13%) after MMR vaccination. Most cases of AEFI were vaccinated with Japanese encephalitis attenuated live vaccine (JEV), with 103 cases (71.03%) after MR vaccination and 102 cases (65.38%) after MMR vaccination.@*Conclusions@#The MMR is safety for 8-month-old children in Jiaxing. Most AEFI cases had abnormal reactions, occur within one day after vaccination, and are vaccinated with JEV.

A Marker-Free Bordetella bronchiseptica aroA/bscN Double Deleted Mutant Confers Protection Against Lethal Challenge.

Bordetella bronchiseptica is a leading cause of swine respiratory disorders which depict a great threat to well-flourished porcine industry. Vaccination remains an effective way for the prevention of B. bronchiseptica infections, as live B. bronchiseptica vaccines possess many advantages compared to inactivated vaccines and/or sub-unit vaccines, however, their safety is not up to the mark. In present study, we constructed marker-free aroA/bscN double deleted B. bronchiseptica QH09 through two-step homologous recombination strategy. Our data showed that QH09 attenuated virulence to mice compared with the parent aroA deleted B. bronchiseptica QH0814. We also found that QH09 meets the vaccine safety standards, upon challenge in piglets, did not cause any visible clinical signs or lesions on organs. Finally, we demonstrated that vaccination of QH09 activated the systemic as well as the mucosal immunity in pigs and provided protection against lethal bacterial challenge. These findings suggest that the aroA/bscN double deleted B. bronchiseptica QH09 may be an effective vaccine candidate, with safety assurance of animals against B. bronchiseptica infections.

Superoxide dismutase B (sodB), an important virulence factor of Vibrio alginolyticus, contributes to antioxidative stress and its potential application for live attenuated vaccine.

Vibrio alginolyticus is an opportunistic and halophilic Gram-negative pathogen in limiting the development of aquatic industry and affecting human health. SODs are oxidative enzymes that play a critical role in oxidative defense. In this study, an in-frame deleted mutant strain (ΔsodB) was constructed by allelic exchange mutagenesis to investigate physiological role of sodB in pathogenicity of V. alginolyticus. The results exhibited that ΔsodB showed no differences in growth compared with wild-type strain HY9901 (WT), but led to increasing in biofilm formation, ECPase activity and sensitivity to hydrogen peroxide, decreasing in swarming motility, adherence to CIK cells, SOD activity and virulence. In addition, ΔsodB induced a high antibody titer and provided a valid protection with a relative percent survival value of 86.5% without inducing clinical symptoms after challenging with WT. These results suggest that sodB is important for normal physiological function, oxidation resistance and virulence in V. alginolyticus, and ΔsodB may be considered as an effective live attenuated vaccine against V. alginolyticus.

Double-attenuated influenza virus elicits broad protection against challenge viruses with different serotypes in swine.

Influenza A viruses (IAV) have caused seasonal epidemics and severe pandemics in humans. Novel pandemic strains as in 2009 may emerge from pigs, serving as perpetual virus reservoir. However, reliably effective vaccination has remained a key issue for humans and swine. Here, we generated a novel double-attenuated influenza live vaccine by reverse genetics and subjected immunized mice and pigs to infection with the homologous wild-type, another homosubtypic H1N1, or a heterosubtypic H3N2 virus to address realistic challenge constellations. This attenuated mutant contains an artificial, strictly elastase-dependent hemagglutinin cleavage site and a C-terminally truncated NS1 protein from the IAV A/Bayern/74/2009 (H1N1pdm09). Prior to challenge, we immunized mice once and pigs twice intranasally. In vitro, the double-attenuated mutant replicated strictly elastase-dependently. Immunized mice and pigs developed neither clinical symptoms nor detectable virus replication after homologous challenge. In pigs, we observed considerably reduced clinical signs and no nasal virus shedding after homosubtypic and reduced viral loads in respiratory tracts after heterosubtypic infection. Protection against homosubtypic challenge suggests that an optimized backbone strain may require less frequent updates with recent HA and NA genes and still induce robust protection in relevant IAV hosts against drifted viruses.

Development of an attenuated live vaccine candidate of duck Tembusu virus strain.

Infection with duck Tembusu virus (DTMUV) can cause large economic losses to the duck-rearing industry in China. In this study, we isolated a virulent strain of DTMUV (SDS) from sparrows near a duck farm and attenuated it via serially passaging (alternately for 100 passages) in specific pathogen-free chicken and duck embryos. We attenuated the virus after the 60th passage (SDS-60), based on the production of embryos that were free of visible lesions and still alive. The 70th adapted strain (SDS-70), obtained with a virus titer of 10-2.46 EID50 was chosen to be the live attenuated vaccine. After immunizing ducklings with the SDS-70 strain, they obtained 100% protection against infection by the SDS-10 virulent strain. Our data demonstrate that the vaccine can protect ducks from becoming infected with TMUV. Our study also shows that this newly developed attenuated vaccine candidate provides excellent immunogenicity, is safe, and has the potential to control DTMUV infections in ducks.

Identification of Fur in Pasteurella multocida and the Potential of Its Mutant as an Attenuated Live Vaccine.

Pasteurella multocida is a pathogenic microorganism that causes a variety of serious diseases in humans and animals worldwide. The global regulator gene, fur, plays an important role in pathogenesis and regulates the virulence of many bacteria. Here, we identified a fur gene in P. multocida by complementing a Salmonella Choleraesuis Δfur mutant, and characterized a fur mutant strain of P. multocida. The P. multocida Δfur mutant strain exhibited no significant differences in growth and outer membrane protein (OMP) profiles when the complemented strain was compared to the parent. Ducks were used as the model organism to determine the virulence and protection efficacy induced by Δfur mutant strain. Animal experiments showed that colonization by the mutant was decreased by oral infection of live Δfur mutant strain. The LD50 of the ducks infected with the Δfur mutant was 146-fold higher than that of the ducks infected with the wild-type strain when administered through the oral route. Evaluation of the immunogenicity and protective efficacy of the Δfur mutant of P. multocida revealed strong serum IgY and bile IgA immune responses following oral inoculation with the Δfur strain. Ducks that were orally inoculated with the Δfur mutant strain demonstrated 62% protection efficacy against severe lethal challenge with the wild-type P. multocida. This study provides new insights into P. multocida virulence and the potential use of an attenuated vaccine against P. multocida.