Protective effects of high-potency FMDV O1 Manisa monovalent vaccine in cattle challenged with FMDV O/SKR/2010 at 7 or 4 days post vaccination

Serotype O foot-and-mouth disease (FMD) virus belonging to the SEA topotype continues to be a significant problem in the Eastern Asia region, with outbreaks in Japan and South Korea resulting in the culling of over 3.5 million cattle and pigs in recent years. High-potency O1 Manisa vaccine was previously shown to provide protection in cattle 21 days post vaccination (dpv) following challenge with a representative virus, O/SKR/2010. This study tested the ability of the O1 Manisa vaccine to protect cattle from infection and disease with the O/SKR/2010 virus within just 4 or 7 days post vaccination. The vaccine protected 50% of cattle from clinical disease when administered 7 days prior to challenge, but was not protective with just 4 days between vaccination and challenge. Viraemia was significantly reduced in animals challenged 7 dpv but not 4 dpv, compared to unvaccinated controls, however, there were no effects on the level of virus detected in nasal and oral secretions regardless of vaccination time. The level of neutralising antibodies detected in cattle challenged 7 dpv correlated with protection from clinical disease. All animals seroconverted to FMDV non-structural proteins, suggesting no sterile protection. An equal number of animals became persistently infected in both vaccine groups. The results indicated that high-potency O1 Manisa vaccine administered just 7 days prior to challenge should provide partial protection of cattle if an outbreak of O/SKR/2010, or related viruses, occurs, and would be useful to limit spread of FMDV when used in conjunction with other control measures.     

Efficacy of a high potency O1 Manisa foot-and-mouth disease vaccine in cattle against heterologous challenge with a field virus from the O/ME-SA/Ind-2001 lineage collected in North Africa

Outbreaks of foot-and-mouth disease (FMD) in North Africa (2013) and the Gulf States (2013) of the Middle East have been caused by a FMD viral lineage (O/ME-SA/Ind-2001) that was before 2013 restricted to the Indian Sub-continent. This study was undertaken to assess the in vivo efficacy of a FMD virus emergency vaccine type O₁ Manisa against heterologous challenge with a representative field virus (O/ALG/3/2014) from this emerging lineage. This widely available vaccine was selected since in vitro vaccine-matching results gave inconclusive results as to whether or not it would be protective. Three groups of five cattle were vaccinated with O₁ Manisa (homologous potency ≥6PD₅₀/dose) using study guidelines outlined in the European Pharmacopeia, and challenged at 21 days post-vaccination by tongue inoculation. All animals that were vaccinated with the lowest dose (1/16) of vaccine developed generalised FMD, defined as vesicular lesions at the feet. One animal vaccinated with a 1/4 dose of the vaccine also developed generalised disease, as did two animals vaccinated with the full dose of vaccine. These results indicate that the heterologous potency of this high potency O₁ Manisa vaccine was approximately 3.5 PD₅₀/dose. These data support the use of the O₁ Manisa vaccine for FMD control in areas where FMDV is endemic e.g. North Africa, and motivate further studies to evaluate other vaccine candidates (or multivalent combinations) that might be potentially used for emergency purposes in FMD-free settings.     

Multiple efficacy studies of an adenovirus-vectored foot-and-mouth disease virus serotype A24 subunit vaccine in cattle using homologous challenge

The safety and efficacy of an experimental, replication-deficient, human adenovirus-vectored foot-and-mouth disease virus (FMDV) serotype A24 Cruzeiro capsid-based subunit vaccine (AdtA24) was examined in eight independent cattle studies. AdtA24 non-adjuvanted vaccine was administered intramuscularly to a total of 150 steers in doses ranging from approximately 1.0 × 10⁸ to 2.1 × 10¹¹ particle units per animal. No detectable local or systemic reactions were observed after vaccination. At 7 days post-vaccination (dpv), vaccinated and control animals were challenged with FMDV serotype A24 Cruzeiro via the intradermal lingual route. Vaccine efficacy was measured by FMDV A24 serum neutralizing titers and by protection from clinical disease and viremia after challenge. The results of eight studies demonstrated a strong correlation between AdtA24 vaccine dose and protection from clinical disease (R² = 0.97) and viremia (R² = 0.98). There was also a strong correlation between FMDV A24 neutralization titers on day of challenge and protection from clinical disease (R² = 0.99). Vaccination with AdtA24 enabled differentiation of infected from vaccinated animals (DIVA) as demonstrated by the absence of antibodies to the FMDV nonstructural proteins in vaccinates prior to challenge. Lack of AdtA24 vaccine shedding after vaccination was indicated by the absence of neutralizing antibody titers to both the adenovector and FMDV A24 Cruzeiro in control animals after co-mingling with vaccinated cattle for three to four weeks. In summary, a non-adjuvanted AdtA24 experimental vaccine was shown to be safe, immunogenic, consistently protected cattle at 7 dpv against direct, homologous FMDV challenge, and enabled differentiation of infected from vaccinated cattle prior to challenge.     

Cross-protective efficacy of engineering serotype A foot-and-mouth disease virus vaccine against the two pandemic strains in swine

Foot-and-mouth disease (FMD) is a highly contagious vesicular disease that affects domestic and wild cloven-hoofed animals worldwide. Recently, a series of outbreaks of type A FMDV occurred in Southeast Asian countries, China, the Russia Federation, Mongolia, Kazakhstan and South Korea. The FMD virus (A/GDMM/CHA/2013) from China's Guangdong province (2013) is representative of those responsible for the latest epidemic, and has low amino acid identity (93.9%) in VP1 protein with the epidemic strain A/WH/CHA/09 from Wuhan, China in 2009. Both of isolates belong to the Sea-97 genotype of ASIA topotype. Therefore, the application of a new vaccine strain with cross-protective efficacy is of fundamental importance to control the spread of the two described pandemic strains. A chimeric strain rA/P1-FMDV constructed by our lab previously through replacing the P1 gene in the vaccine strain O/CHA/99 with that from the epidemic stain A/WH/CHA/09, has been demonstrated to exhibit good growth characteristics in culture, and the rA/P1-FMDV inactivated vaccine can provide protection against epidemic strain A/WH/CHA/09 in cattle. However, it is still unclear whether the vaccine produces efficient protection against the new pandemic strain (A/GDMM/CHA/2013). Here, vaccine matching and pig 50% protective dose (PD₅₀) tests were performed to assess the vaccine potency. The vaccine matching test showed cross-reactivity of sera from full dose vaccine vaccinated pigs with A/WH/CHA/09 and A/GDMM/CHA/2013 isolates, with average r₁ values of 0.94 ± 0.12 and 0.68 ± 0.06 (r₁ ≥ 0.3), which indicates that the rA/P1-FMDV vaccine is likely to confer good cross-protection against the two isolates. When challenged with two pandemic isolates A/WH/CHA/09 and A/GDMM/CHA/2013 strain, the vaccine achieved 12.51 PD₅₀ and 10.05 PD₅₀ per dose (2.8 μg), respectively. The results indicated that the rA/P1-FMDV inactivated vaccine could protect pigs against both A/WH/CHA/09 and A/GDMM/CHA/2013 pandemic isolates.     

Evaluation of the safety,immunogenicity and efficacy of three capripoxvirus vaccine strains against lumpy skin disease virus

The safety, immunogenicity and efficacy of three commercially available vaccines against lumpy skin disease (LSD) in cattle have been evaluated using a combination of vaccine challenge experiments and the monitoring of immune responses in vaccinated animals in the field. The three vaccines evaluated in the study included two locally produced (Ethiopian) vaccines (lumpy skin disease virus (LSDV) Neethling and Kenyan sheep and goat pox (KSGP) O-180 strain vaccines) and a Gorgan goat pox (GTP) vaccine manufactured by Jordan Bio-Industries Centre (JOVAC). The latter vaccine was evaluated for the first time in cattle against LSDV. The Ethiopian Neethling and KSGPO-180 vaccines failed to provide protection in cattle against LSDV, whereas the Gorgan GTP vaccine protected all the vaccinated calves from clinical signs of LSD. There was no significant difference in protective efficacy detected between two dosage levels (P = 0.2, P = 0.25, and P = 0.1 for KSGP, Neethling and Gorgan vaccines, respectively). Additionally, the Gorgan GTP vaccinated cattle showed stronger levels of cellular immune responses measured using Delayed-Type Hypersensitivity (DTH) reactions at the vaccination site indicating higher levels of immunogenicity produced by the GTPV vaccine in cattle, as opposed to the other two vaccines. This study indicated, for the first time, that the Gorgan GTP vaccine can effectively protect cattle against LSDV and that the Neethling and KSGP O-180 vaccine were not protective. The results emphasise the need for molecular characterization of the Neethling and KSGP O-180 vaccine seed viruses used for vaccine production in Ethiopia. In addition, the potency and efficacy testing process of the Ethiopian LSD Neethling and KSGP O-180 vaccines should be re-evaluated.     

Cross-protective efficacy of the O1 Manisa + O 3039 bivalent vaccine and the O 3039 monovalent vaccine against heterologous challenge with FMDV O/Jincheon/SKR/2014 in pig

After massive foot-and-mouth disease (FMD) outbreaks originated from Jincheon County from Dec. 2014 to Apr. 2015, the effectiveness of the previous FMD vaccine containing only the O1 Manisa as the O antigen, O1 Manisa?+?A Malaysia 97?+?Asia 1 Sharmir trivalent vaccine, was questioned in South Korea, and a change in the O antigen in FMD vaccines was demanded to control the FMD caused by FMDV O/Jincheon/SKR/2014, the O Jincheon strain. Therefore, the efficacies of O1 Manisa?+?O 3039 bivalent vaccine and O 3039 monovalent vaccine were studied for cross-protection against heterologous challenge with the O Jincheon strain. In this study, the efficacy of the O1 Manisa?+?O 3039 bivalent vaccine was better than that of the O 3039 monovalent vaccine, even though the serological relationship (r₁ value) between O Jincheon and O 3039 was matched according to the OIE Terrestrial Manual. According to serological test results from vaccinated specific pathogen free pigs, virus neutralization test titers against Jincheon were good estimates for predicting protection against challenge. A field trial of the O1 Manisa?+?O 3039 bivalent vaccine was performed to estimate the possibility of field application in conventional pig farms, especially due to concerns about the effect of maternally derived antibodies (MDA) in field application of the FMD vaccine. According to the result of the field trial, the O1 Manisa?+?O 3039 bivalent vaccine was considered to overcome MDA. The results of the efficacy and field trials indicated that the O1 Manisa?+?O3039 vaccine could be suitable to replace previous FMD vaccines to control the FMD field situation caused by O Jincheon FMDV.     

The interference effect of maternally-derived antibodies on the serological performance of pigs immunized with a foot-and-mouth disease oil emulsion vaccine

To control foot-and-mouth disease (FMD) outbreaks that originated in Jincheon County in South Korea between 2014 and 2015, several commercial vaccines were studied for their efficacy and serological performance in the field. In this study, the efficacy of the O SKR 7/10 vaccine was evaluated by challenge with the FMD virus (FMDV) O/Jincheon/SKR/2014 (O Jincheon), which has the same O/SEA/Mya-98 lineage as the O/SKR/7/10 strain that was isolated in 2010 in South Korea, in FMD-seronegative pigs. Full protection against the O Jincheon virus was demonstrated as early as 14 days postvaccination, which was explained by the strong serological relationship (r₁ value: ≥ 0.92) between the O Jincheon and O SKR 2010 viruses. However, in the field trial, no satisfactory serological elevations against FMDV were observed, even in the double-vaccinated groups. Therefore, it can be concluded that the O SKR 7/10 vaccine may need to be improved to overcome the interference effects from the high levels of maternally-derived antibodies generated due to the mandatory nationwide vaccination of sows in South Korea.     

Efficacy of a high quality O1/Campos foot-and-mouth disease vaccine upon challenge with a heterologous Korean O Mya98 lineage virus in pigs

In 2010 serotype O foot-and-mouth disease virus of the Mya98 lineage/SEA topotype spread into most East Asian countries. During 2010–2011 it was responsible for major outbreaks in the Republic of Korea where a monovalent O/Manisa vaccine (belonging to the ME-SA topotype) was applied to help control the outbreaks. Subsequently, all susceptible animals were vaccinated every 6 months with a vaccine containing the O/Manisa antigen. Despite vaccination, the disease re-occurred in 2014 and afterwards almost annually. This study focuses on the in vivo efficacy in pigs of a high quality monovalent commercial O₁/Campos vaccine against heterologous challenge with a representative 2015 isolate from the Jincheon Province of the Republic of Korea. Initially, viral characterizations and r₁ determinations were performed on six viruses recovered in that region during 2014–2015, centering on their relationship with the well characterized and widely available O₁/Campos vaccine strain. Genetic and antigenic analysis indicated a close similarity among 2014–2015 Korean isolates and with the previous 2010 virus, with distinct differences with the O₁/Campos strain. Virus neutralisation tests using O₁/Campos cattle and pig post vaccination sera and recent Korean outbreak viruses predicted acceptable cross-protection after a single vaccination, as indicated by r₁ values, and in pigs, by expectancy of protection. In agreement with the in vitro estimates, in vivo challenge with a selected field isolate indicated that O₁/Campos primo vaccinated pigs were protected, resulting in a PD50 value of nearly 10. The results indicated that good quality oil vaccines containing the O₁/Campos strain can successfully be used against isolates belonging to the O Mya98/SEA topotype.     

Efficacy of a high potency O1 Manisa monovalent vaccine against heterologous challenge with a FMDV O Mya98 lineage virus in pigs 4 and 7 days post vaccination

Early protection with a high potency (>6PD₅₀) foot-and-mouth disease (FMD) O₁ Manisa (Middle-East South Asia lineage) vaccine against challenge with O/VIT/2010 (O Mya98 lineage) was tested in pigs. Only two pigs that were vaccinated seven days prior to challenge had any demonstrable antibodies as a result of vaccination at the time of challenge. However, 80% and 60% of pigs that were vaccinated seven and four days prior to coronary band challenge were protected. Vaccination significantly reduced the amount of virus excreted in nasal swabs, saliva and faeces compared to unvaccinated and infected controls. Virus and viral RNA could be detected in some pigs until termination of the experiment 14 days after challenge. Antibodies to the non-structural proteins (NSP) were detected in only one pig that was challenged four days post vaccination (dpv) and transiently in two pigs that were challenged seven dpv at only one time point. For each vaccine and control group, a group of unvaccinated pigs were kept in the same room but with no direct contact with the infected pigs to determine whether vaccination prevented transmission. Despite the presence of live virus and viral RNA in these indirect contact pigs, the groups in contact with the vaccinated and infected pigs did not develop clinical signs nor did they sero-convert. Contact pigs in the same room as unvaccinated challenged controls did show signs of disease and virus infection that resulted in sero-conversion to the NSP. A breach of the wall that separated the two groups at nine days post challenge might have contributed to this finding. This study showed that high potency vaccine can provide protection to pigs soon after vaccination and that aerosol transmission within rooms is a rare event.     

Genetic and antigenic characterization of Indian foot-and-mouth disease virus serotype O isolates collected during the period 2001 to 2012

The phylogenetic analysis of VP1 sequences of the 39 type O foot and mouth virus (FMDV) isolates collected from different regions of India during the year of 2001–12 revealed that all isolates belonged to the Middle East – South Asia (ME-SA) topotype. Based on the amount of divergence among the isolates, the viruses were further classified into three distinct lineages namely Ind 2001, PanAsia and PanAsia-2 as well as a minor, unnamed group. Ind 2001 lineage viruses accounted for most of the current type O outbreaks. At the nucleotide level these isolates showed a divergence of 2% to 14% with an average sequence variation of ∼9.9%. The serological spectrum of the current vaccine strain was studied by using bovine vaccinate serum (BVS) raised against O/IND/R2/75. All the current field isolates (n = 24) were homologous (‘r’ value 0.4 to 1.0) to the vaccine strain. Examination of the amino acid sequences for selection pressure revealed the positive selection at amino acid sites 13 and 45.     

Evaluation of cross-protection between O1 Manisa and O1 Campos in cattle vaccinated with foot-and-mouth disease virus vaccine incorporating different payloads of inactivated O1 Manisa antigen

Serology is used to predict vaccine induced protection against challenge with a heterologous strain of the same serotype of foot-and-mouth disease virus (FMDV). To evaluate the accuracy of such predictions, we compared the protection afforded to cattle vaccinated with the O₁ Manisa strain of FMDV against challenge with either a homologous (O₁ Manisa) or a heterologous strain (O₁ Campos). Serology by virus neutralization test (VNT) using O₁ Manisa antiserum predicted an acceptable protection against such a challenge. Two experiments were carried out to compare the results for consistency. A total of 78 naïve cattle were vaccinated with different antigen payloads (60-0.94 μg) of O₁ Manisa. They were challenged by intradermolingual inoculation with live FMDV, either O₁ Manisa or O₁ Campos. Unvaccinated naïve control cattle (n = 20) were also challenged with either the O₁ Manisa or O₁ Campos viruses and all developed generalized FMD. The protection results for the vaccinated cattle revealed that higher payloads of O₁ Manisa vaccine were needed to protect against heterologous challenge compared to that for homologous challenge. The 50% protective dose (PD₅₀) values for the vaccine in experiments 1 and 2 were found to be 28.78 and 9.44 for the homologous challenge and 3.98 and 5.01 for heterologous challenge. Furthermore, protection against O₁ Campos required a higher level of vaccine-induced antibody against this virus compared to the level of O₁ Manisa neutralizing antibody associated with protection against homologous challenge. The 50% protective level of in vitro neutralizing antibody was found to be log₁₀ 1.827 for O₁ Campos and log₁₀ 0.954 for O₁ Manisa based on O₁ Manisa based virus neutralization test.     

Expression of H5 hemagglutinin vaccine antigen in common duckweed (Lemna minor) protects against H5N1 high pathogenicity avian influenza virus challenge in immunized chickens

A synthetic hemagglutinin (HA) gene from the highly pathogenic avian influenza (HPAI) virus A/chicken/Indonesia/7/2003 (H5N1) (Indo/03) was expressed in aquatic plant Lemna minor (rLemna-HA). In Experiment 1, efficacy of rLemna-HA was tested on birds immunized with 0.2 μg or 2.3 μg HA and challenged with 10⁶ mean chicken embryo infectious doses (EID₅₀) of homologous virus strain. Both dosages of rLemna-HA conferred clinical protection and dramatically reduced viral shedding. Almost all the birds immunized with either dosage of rLemna-HA elicited HA antibody titers against Indo/03 antigen, suggesting an association between levels of anti-Indo/03 antibodies and protection. In Experiment 2, efficacy of rLemna-HA was tested on birds immunized with 0.9 μg or 2.2 μg HA and challenged with 10⁶ EID₅₀ of heterologous H5N1 virus strains A/chicken/Vietnam/NCVD-421/2010 (VN/10) or A/chicken/West Java/PWT-WIJ/2006 (PWT/06). Birds challenged with VN/10 exhibited 100% survival regardless of immunization dosage, while birds challenged with PWT/06 had 50% and 30% mortality at 0.9 μg HA and 2.2 μg HA, respectively. For each challenge virus, viral shedding titers from 2.2 μg HA vaccinated birds were significantly lower than those from 0.9 μg HA vaccinated birds, and titers from both immunized groups were in turn significantly lower than those from sham vaccinated birds. Even if immunized birds elicited HA titers against the vaccine antigen Indo/03, only the groups challenged with VN/10 developed humoral immunity against the challenge antigen. None (rLemna-HA 0.9 μg HA) and 40% (rLemna-HA 2.2 μg HA) of the immunized birds challenged with PWT/06 elicited pre-challenge antibody titers, respectively. In conclusion, Lemna-expressed HA demonstrated complete protective immunity against homologous challenge and suboptimal protection against heterologous challenge, the latter being similar to results from inactivated whole virus vaccines. Transgenic duckweed-derived HA could be a good alternative for producing high quality antigen for an injectable vaccine against H5N1 HPAI viruses.     

Emergency vaccination of sheep against foot-and-mouth disease: significance and detection of subsequent sub-clinical infection

This study has quantified the level of foot-and-mouth disease virus (FMDV) replication and shedding in vaccinated sheep and correlated this to the severity of clinical signs, the induction of antibodies against FMDV non-structural proteins (NSPs) and the transmission of virus to in-contact vaccinated sentinel sheep. To mimic an emergency vaccination regime in the field, sheep were vaccinated with O(1) Manisa vaccine and 4 or 10 days later were indirectly challenged with aerosols from O(1) UKG FMDV infected pigs. Vaccinated and control unvaccinated sheep were monitored for a minimum of 39 days post-challenge. The vaccinated sheep became sub-clinically infected, with reduced virus replication and excretion compared to unvaccinated and clinically infected sheep. Seroconversion to NSP was weak and transient in sheep in which virus replication was of low level and short duration. Virus transmission from vaccinated sub-clinically infected sheep to introduced vaccinated sentinels was not sufficient to cause NSP seroconversion or significant virus shedding. 10% of 10 days and 20% of 4 days vaccinated sheep were virus carriers at greater than 28 days post-challenge compared to 37.5% in the unvaccinated and clinically infected sheep. These results suggest that the low levels of virus replication likely if an effective vaccine is administered at least 4 days prior to challenge exposure are unlikely to result in the spread of infection even under intensive management conditions. Although it may be difficult to detect this infection by serosurveillance, the significance of missing it is likely to be low and the main value of such testing will be to detect undisclosed clinical infection resulting from lack of observation or from exposure to virus before or very soon after vaccination or from vaccine failure due to maladministration or inappropriate strain selection.     

Efficacy of a recombinant Intimin,EspB and Shiga toxin 2B vaccine in calves experimentally challenged with Escherichia coli O157:H7

Escherichia coli O157:H7 is a zoonotic pathogen of global importance and the serotype of Shiga toxin-producing E. coli (STEC) most frequently associated with Hemolytic Uremic Syndrome (HUS) in humans. The main STEC reservoir is cattle. Vaccination of calves with the carboxy-terminal fraction of Intimin γ (IntC280) and EspB can reduce E. coli O157:H7 fecal shedding after experimental challenge. Shiga toxin (Stx) exerts local immunosuppressive effects in the bovine intestine and Stx2B fused to Brucella lumazine synthase (BLS-Stx2B) induces Stx2-neutralizing antibodies. To determine if an immune response against Stx could improve a vaccine’s effect on fecal shedding, groups of calves were immunized with EspB + IntC280, with EspB + IntC280 + BLS-Stx2B, or kept as controls. At 24 days post vaccination calves were challenged with E. coli O157:H7. Shedding of E. coli O157:H7 was assessed in recto-anal mucosal swabs by direct plating and enrichment followed by immunomagnetic separation and multiplex PCR. Calves were euthanized 15 days after the challenge and intestinal segments were obtained to assess mucosal antibodies. Vaccination induced a significant increase of IntC280 and EspB specific antibodies in serum and intestinal mucosa in both vaccinated groups. Antibodies against Stx2B were detected in serum and intestinal mucosa of animals vaccinated with 3 antigens. Sera and intestinal homogenates were able to neutralize Stx2 verocytotoxicity compared to the control and the 2-antigens vaccinated group. Both vaccines reduced E. coli O157:H7 shedding compared to the control group. The addition of Stx2B to the vaccine formulation did not result in a superior level of protection compared to the one conferred by IntC280 and EspB alone. It remains to be determined if the inclusion of Stx2B in the vaccine alters E. coli O157:H7 shedding patterns in the long term and after recurrent low dose exposure as occurring in cattle herds.     

Zika virus knowledge,attitudes, and vaccine interest among university students

BackgroundZika virus vaccine development is underway. We examined interest in receiving a Zika virus vaccine (after one becomes commercially available) among students at a large public university in Northern Virginia.MethodsAn online survey of Zika virus-related knowledge, attitudes, and interest in receiving a Zika vaccine was completed by 619 undergraduate students in April, 2016. Stepwise logistic regression with backward elimination was used to identify the variables most strongly associated with interest in being vaccinated against Zika virus.ResultsMore than half of participants (52.8%) reported that they would be likely or very likely to be vaccinated against Zika virus. Vaccination interest was significantly higher among participants who received an influenza vaccine in the past year (p = 0.002), had higher levels of knowledge about Zika virus (p = 0.046), reported knowing where to access information about Zika virus (p = 0.041), had higher perceived susceptibility to Zika virus (p < 0.001), and believed that the U.S. Government should prioritize actions to control Zika virus (p = 0.001).ConclusionsCommunication and intervention strategies encouraging vaccine uptake may benefit from increasing knowledge of Zika virus, addressing perceived susceptibility, and reaching students, travelers, and others who may be seeking information about prevention of Zika virus and other emerging infectious diseases.     

Vaccination with a live attenuated Acinetobacter baumannii deficient in thioredoxin provides protection against systemic Acinetobacter infection

Multi-drug resistant Acinetobacter baumannii (MDR-Ab), an opportunistic pathogen associated with nosocomial and combat related infections, has a high mortality due to its virulence and limited treatment options. Deletion of the thioredoxin gene (TrxA) from a clinical isolate of MDR-Ab resulted in a 100-fold increase in 50% lethal dose (LD₅₀) in a systemic challenge murine model. Thus, we investigated the potential use of this attenuated strain as a live vaccine against MDR-Ab. Mice were vaccinated by subcutaneous (s.c.) injection of 2 × 10⁵ CFU of the ΔtrxA mutant, boosted 14 days later with an equivalent inoculum, and then challenged 30 days post-vaccination by i.p. injection with 10 LD₅₀ of the wild type (WT) Ci79 strain. Efficacy of vaccination was evaluated by monitoring MDR-Ab specific antibody titers and cytokine production, observing pathology and organ burdens after WT challenge, and measuring levels of serum pentraxin-3, a molecular correlate of A. baumannii infection severity, before and after challenge. Mice vaccinated with ΔtrxA were fully protected against the lethal challenge of WT. However, minimal immunoglobulin class switching was observed with IgM predominating. Spleens harvested from vaccinated mice exhibited negligible levels of IL-4, IFN-γ and IL-17 production when stimulated with UV-inactivated WT Ci79. Importantly, tissues obtained from vaccinated mice displayed reduced pathology and organ burden compared to challenged non-vaccinated mice. Additionally, serum pentraxin-3 concentrations were not increased 24 h after challenge in vaccinated mice, correlating with reduction of WT MDR-Ab infection in ΔtrxA immunized mice. Furthermore, passive immunization with ΔtrxA-immune sera provided protection against lethal systemic Ci79 challenge. Collectively, the defined live attenuated ΔtrxA strain is a vaccine candidate against emerging MDR Acinetobacter infection.     

KISS1 can be used as a novel target for developing a DNA immunocastration vaccine in ram lambs

KISS1 gene-encoding kisspeptins are critical for the onset of puberty and control of adult fertility. This study investigated whether KISS1 can be used as a novel target for immunocastration. Human KISS1 was fused with the HBsAg-S gene for constructing an antibiotic-free recombinant plasmid pKS-asd that coded for 31.168 kDa target fusion protein. Six male Hu sheep lambs were divided into two equal groups, treatment and control. The vaccine (1 mg/ram lamb) prepared in saline solution was injected into lambs at weeks 0, 3 and 6 of the experiment, respectively. Vaccine efficacy was evaluated in terms of KISS1-specific IgG antibody response, serum testosterone levels, scrotal circumference, testicular weight, length and breadth, extent of testicular tissue damage, and sexual behaviour changes. The specific anti-KISS1 antibody titre in vaccinated animals was significantly higher than that in controls (p < 0.05). In addition, vaccinated animals showed lower serum testosterone level, testicular weight and length and smaller scrotal circumference than those in controls (p < 0.05). Spermatogenesis of seminiferous tubules in vaccinated animals was suppressed; sexual behaviours in vaccinated animals were significantly lower (p < 0.05) than those in controls. In conclusion, the immunization against KISS1 in this DNA vaccine induced a strong antibody response and resulted in the suppression of gonadal function and sexual behaviour in animals, demonstrating that KISS1 can be used as a novel target for developing a DNA immunocastration vaccine.     

A vero cell derived combined vaccine against sheep pox and Peste des Petits ruminants for sheep

The combined sheep pox and Peste des Petits ruminants (PPR) vaccine was prepared in lyophilized form containing recommended doses of both vaccine viruses. Safety and immunogenicity of this combined vaccine was evaluated in sheep. Sheep immunized subcutaneously with 1 ml of live attenuated vaccine consisting of 10³ TCID₅₀ each of sheep pox virus (SPV) Romanian Fanar (RF) strain and Peste des Petits ruminants virus (PPRV-Sungri/96 strain) were monitored for clinical and serological responses for a period of four weeks post immunization (pi) and two week post challenge (pc). Specific antibodies directed to sheep pox virus could be demonstrated by indirect ELISA and serum neutralization test (SNT). Competitive ELISA and SNT were used for demonstration of antibodies to PPR virus. All the immunized animals resisted challenge with virulent SPV or PPRV on day 30 pi, while control animals developed characteristic signs of disease. Specific virus could be detected in the unvaccinated control animals after challenge but not from any of the immunized sheep. Combined vaccine was found to be safe and potent as evident from sero conversion as well as challenge studies in sheep. This indicates that component vaccines did not interfere each other and can be used in target population for economic vaccination strategies.     

Efficacy of the oral rabies virus vaccine strain SPBN GASGAS in foxes and raccoon dogs

To test the immunogenicity and efficacy of a new oral rabies virus vaccine strain SPBN GASGAS in wildlife target species, one group of foxes and two groups of raccoon dogs were offered a bait containing 1.7 ml of the vaccine (10^6.6 FFU/ml; 10^6.8 FFU/dose) and subsequently challenged approximately 180 days later with a fox rabies virus isolate. One group of raccoon dogs (n = 30) received the same challenge dose (10^0.7 MICLD₅₀/ml) as the red foxes (n = 29). The other group with raccoon dogs (n = 28) together with 8 animals that received the vaccine dose by direct instillation into the oral cavity (DIOC) were infected with a 40-fold higher dose of the challenge virus (10^2.3 MICLD₅₀/ml). All but one of the 29 vaccinated foxes survived the challenge infection; meanwhile all 12 control foxes succumbed to rabies. Twenty-eight of 30 vaccinated raccoon dogs challenged with the same dose survived the infection, however only six of 12 control animals succumbed. When the higher challenge dose was administered, all 12 control animals died from rabies and all 36 vaccinated animals (28 baited plus 8 DIOC) survived. Blood samples were collected at different time points post vaccination and examined by both RFFIT and ELISA. The kinetics of the measured immune response was similar for both species, although in RFFIT slightly higher values were observed in foxes than in raccoon dogs. However, the immune response as measured in ELISA was identical for both species. The oral rabies virus vaccine SPBN GASGAS meets the efficacy requirements for live rabies virus vaccines as laid down by the European Pharmacopoeia.     

Bartha-k61 vaccine protects growing pigs against challenge with an emerging variant pseudorabies virus

Since late 2011, pseudorabies (PR) has resurfaced in many large pig farms, causing great economic loss for the swine industry in China. The PRV variant strain with high virulence and antigenic variation has been considered to be the main cause, and much attention has been focused on how to prevent and control the reoccurrence of this disease in China. In this study, two kinds of vaccination strategy were employed to evaluate the protective effects of Bartha-k61vaccine against both variant PRV (XJ5) and classical PRV (Ra) strain challenge. Humoral immunity response, clinical signs, survival rate, body weight, virus shedding and pathology were assessed in commercial pigs. The results showed that Bartha-k61vaccine, administered either once or twice, was effective against the PRV variant (XJ5) challenge, while no significant differences were observed between single and prime-boost vaccinated pigs. However, pigs vaccinated twice had better body weight gains than those vaccinated once, following challenge with the classical PRV strain (Ra) (p < 0.01). Therefore, the Bartha-k61 vaccine appears to be an effective vaccine to control the spread of PRV variants in China in the absence of new powerful candidate vaccines specific to these PRV strains.