Recombinant Fowlpox Virus Vaccines Research Articles

Efficacy of Fowlpox Virus Vector Vaccine Expressing VP2 and Chicken Interleukin-18 in the Protection against Infectious Bursal Disease Virus.

In mammals, the role of interleukin-18 (IL-18) in the immune response is to drive inflammatory and, normally therefore, anti-viral responses. IL-18 also shows promise as a vaccine adjuvant in mammals. Chicken IL-18 (chIL-18) has been cloned. The aim of this study was to investigate the potential of chIL-18 to act as a vaccine adjuvant in the context of a live recombinant Fowlpox virus vaccine (fpIBD1) against Infectious bursal disease virus (IBDV). fpIBD1 protects against mortality, but not against damage to the bursa of Fabricius caused by IBDV infection. The Fowlpox virus genome itself contains several candidate immunomodulatory genes, including potential IL-18 binding proteins (IL-18bp). We knocked out (Δ) the potential IL-18bp genes in fpIBD1 and inserted (::) the cDNA encoding chIL-18 into fpIBD1 in the non-essential ORF030, generating five new viral constructs -fpIBD1::chIL-18, fpIBD1ΔORF073, fpIBD1ΔORF073::chIL-18, fpIBD1ΔORF214, and fpIBD1ΔORF214::chIL-18. The subsequent protection from challenge with virulent IBDV, as measured by viral load and bursal damage, given by these altered fpIBD1 strains, was compared to that given by the original fpIBD1. Complete protection was provided following challenge with IBDV in chicken groups vaccinated with either fpIBDIΔ073::IL-18 or fpIBD1Δ214::IL-18, as no bursal damage nor IBDV was detected in the bursae of the birds. The results show that chIL-18 can act as an effective vaccine adjuvant by improving the fpIBD1 vaccine and providing complete protection against IBDV challenge.

Efficacy of novel recombinant fowlpox vaccine against recent Mexican H7N3 highly pathogenic avian influenza virus

Since 2012, H7N3 highly pathogenic avian influenza (HPAI) has produced negative economic and animal welfare impacts on poultry in central Mexico. In the present study, chickens were vaccinated with two different recombinant fowlpox virus vaccines (rFPV-H7/3002 with 2015 H7 hemagglutinin [HA] gene insert, and rFPV-H7/2155 with 2002 H7 HA gene insert), and were then challenged three weeks later with H7N3 HPAI virus (A/chicken/Jalisco/CPA-37905/2015). The rFPV-H7/3002 vaccine conferred 100% protection against mortality and morbidity, and significantly reduced virus shed titers from the respiratory and gastrointestinal tracts. In contrast, 100% of sham and rFPV-H7/2155 vaccinated birds shed virus at higher titers and died within 4 days. Pre- (15/20) and post- (20/20) challenge serum of birds vaccinated with rFPV-H7/3002 had antibodies detectable by hemagglutination inhibition (HI) assay using challenge virus antigen. However, only a few birds (3/20) in the rFPV-H7/2155 vaccinated group had antibodies that reacted against the challenge strain but all birds had antibodies that reacted against the homologous vaccine antigen (A/turkey/Virginia/SEP-66/2002) (20/20). One possible explanation for differences in vaccines efficacy is the antigenic drift between circulating viruses and vaccines. Molecular analysis demonstrated that the Mexican H7N3 strains have continued to rapidly evolve since 2012. In addition, we identified in silico three potential new N-glycosylation sites on the globular head of the H7 HA of A/chicken/Jalisco/CPA-37905/2015 challenge virus, which were absent in 2012 H7N3 outbreak virus. Our results suggested that mutations in the HA antigenic sites including increased glycosylation sites, accumulated in the new circulating Mexican H7 HPAIV strains, altered the recognition of neutralizing antibodies from the older vaccine strain rFPV-H7/2155. Therefore, the protective efficacy of novel rFPV-H7/3002 against recent outbreak Mexican H7N3 HPAIV confirms the importance of frequent updating of vaccines seed strains for long-term effective control of H7 HPAI virus.

Protection Against Mycoplasma gallisepticum in Layers Immunized with Recombinant Fowl Poxvirus Vaccine Followed by Live F Strain Vaccine

Protection Against Mycoplasma gallisepticum in Layers Immunized with Recombinant Fowl Poxvirus Vaccine Followed by Live F Strain Vaccine

Protection against H7N3 high pathogenicity avian influenza in chickens immunized with a recombinant fowlpox and an inactivated avian influenza vaccines

Beginning on June 2012, an H7N3 highly pathogenic avian influenza (HPAI) epizootic was reported in the State of Jalisco (Mexico), with some 22.4 million chickens that died, were slaughtered on affected farms or were preemptively culled on neighboring farms. In the current study, layer chickens were vaccinated with a recombinant fowlpox virus vaccine containing a low pathogenic AI (LPAI) H7 gene insert (rFPV-H7-AIV) and an inactivated oil-emulsified H7N3 AIV vaccine, and subsequently challenged against the Jalisco H7N3 HPAIV. All vaccine combinations provided similar and significant protection against mortality, morbidity, and shedding of challenge virus from the respiratory and gastrointestinal tracts. Serological data also suggested analogous protection from HPAIV among immunized birds. Control of the recent Jalisco AIV infection could be achieved by using various combinations of the two vaccines tested. Even though a single dose of rFPV-H7-AIV vaccine at 1-day-of-age would be the most pragmatic option, optimal protection may require a second dose of vaccine administered in the field.

Recombinant duck enteritis virus works as a single-dose vaccine in broilers providing rapid protection against H5N1 influenza infection

Although vaccination is an important strategy for controlling H5N1 avian influenza virus infections, broilers (short-lived meat chickens) remain the major victims in disease-endemic countries. Inactivated vaccine usually requires 2–3weeks to establish solid protection, and recombinant vaccines, including the recombinant fowlpox virus vaccine and the recombinant Newcastle disease virus vaccine are affected by maternal antibodies against the vectors. These disadvantages compromise the protective efficacy of these vaccines in broilers. Here, we evaluated the safety and efficacy of a new recombinant duck enteritis virus that expresses the HA gene of an H5N1 virus (rDEV-re6) in specific-pathogen-free chickens and broilers. We found this new rDEV-re6 virus to be safe in chickens and to induce rapid and solid protection after a single dose. This virus may therefore serve as an ideal single-dose vaccine for broilers.

Evaluation of recombinant fowlpox virus expressing infectious bronchitis virus S1 gene and chicken interferon-γ gene for immune protection against heterologous strains

A recombinant fowlpox virus (rFPV-IFNγS1) that co-expressed the infectious bronchitis virus (IBV) S1 gene and the chicken interferon-γ gene has been constructed. To evaluate the efficacy of the recombinant fowlpox virus vaccine against heterotypic IBV strains, 60 4-week-old Specific-Pathogen-Free (SPF) chickens were inoculated with this vaccine and 3 weeks post inoculation challenged with the homotypic IBV strain LX4 and the heterotypic IBV strains LHB, LHLJ04XI, LTJ95I and LSC99I. Antibodies against IBV were detected in vaccinated chickens 1-week post inoculation. The number of CD4+ and CD8+ T-lymphocytes in the peripheral blood increased rapidly in the vaccinated groups challenged with strains LX4, LHB and LHLJ04XI. There were significant differences in the number of CD4+ and CD8+ T-lymphocytes between the vaccinated groups challenged with strains LTJ95I and LSC99I and all the control groups. The morbidity was below 30% in vaccinated groups challenge with strains LX4, LHB and LHLJ04XI, but was 40% greater than that in the other groups. In addition, the lesions and the amount of virus shedding were less severe in the vaccinated groups challenged by strains LX4, LHB and LHLJ04XI when compared with the other groups, but there was no significant difference in the average body weight of the chickens in all groups (all p>0.05). These results indicate that the rFPV-IFNγS1 protected chickens against challenge with homotypic IBV strain LX4 and heterotypic strains LHLJ04XI and LHB.

The development of persistent duck hepatitis B virus infection can be prevented using antiviral therapy combined with DNA or recombinant fowlpoxvirus vaccines

We recently reported the development of a successful post-exposure combination antiviral and “prime-boost” vaccination strategy using the duck hepatitis B virus (DHBV) model of human hepatitis B virus infection. The current study aimed to simplify the vaccination strategy and to test the post-exposure efficacy of combination therapy with the Bristol-Myers Squibb antiviral drug, entecavir (ETV) and either a single dose of DHBV DNA vaccines on day 0 post-infection (p.i.) or a single dose of recombinant fowlpoxvirus (rFPV–DHBV) vaccines on day 7 p.i. Whilst untreated control ducks infected with an equal dose of DHBV all developed persistent and wide spread DHBV infection of the liver, ducks treated with ETV combined with either the DHBV DNA vaccines on day 0 p.i. or the rFPV–DHBV vaccines on day 7 p.i. had no detectable DHBV-infected hepatocytes by day 14 p.i. and were protected from the development of persistent DHBV infection.

A safety assessment of a fowlpox-vectored Mycoplasma gallisepticum vaccine in chickens

A recombinant fowlpox virus vaccine expressing key protective Mycoplasma gallisepticum antigens could facilitate in the prevention both of fowlpox virus and M. gallisepticum infections. Vectormune FP-MG vaccine, a recombinant fowlpox virus expressing both M. gallisepticum 40k and mgc genes, was assessed for its safety in 8-wk-old specific-pathogen-free White Leghorn chickens. The vaccine virus was serially passaged 5 times by wing-web inoculation. Based on the postinoculation clinical observation, gross pathological examination of air sacs and peritoneum, genetic stability evaluation, virus shedding and tissue distribution detection, horizontal transmission ability determination, and protection against fowlpox virus challenge, the Vectormune FP-MG vaccine possesses a high level of safety.

Characterization and efficacy determination of commercially available Central American H5N2 avian influenza vaccines for poultry

A poultry vaccination program was implemented in Central America beginning in January 1995 to control both H5N2 low (LPAI) and high pathogenicity avian influenza. This study was conducted to identify seed strain composition and the efficacy of 10 commercially available H5 vaccines against challenge with H5N2 LPAI viruses isolated from Latin America in 2003. The original 1994 vaccine seed virus in commercial inactivated vaccines did not significantly reduce challenge virus shed titers. However, two seed strains of inactivated vaccines, genetically more closely related to the challenge virus, did significantly reduce titers of challenge virus shed from respiratory tract. In addition, a live recombinant fowlpox virus vaccine containing a more distantly related Eurasian lineage H5 gene insert significantly reduced respiratory shedding as compared to sham vaccinates. These results demonstrate the feasibility of identifying vaccine seed strains in commercial finished products for regulatory verification and the need for periodic challenge testing against current field strains in order to select efficacious vaccine seed strains.

Improvements to the Hemagglutination Inhibition Test for Serological Assessment of Recombinant Fowlpox–H5-Avian-Influenza Vaccination in Chickens and Its Use Along with an Agar Gel Immunodiffusion Test for Differentiating Infected from Noninfected Vaccinated Animals

In general, avian influenza (AI) vaccines protect chickens from morbidity and mortality and reduce, but do not completely prevent, replication of wild AI viruses in the respiratory and intestinal tracts of vaccinated chickens. Therefore, surveillance programs based on serological testing must be developed to differentiate vaccinated flocks infected with wild strains of AI virus from noninfected vaccinated flocks in order to evaluate the success of vaccination in a control program and allow continuation of national and international commerce of poultry and poultry products. In this study, chickens were immunized with a commercial recombinant fowlpox virus vaccine containing an H5 hemagglutinin gene from A/turkey/Ireland/83 (H5N8) avian influenza (AI) virus (rFP-H5) and evaluated for correlation of immunological response by hemagglutination inhibition (HI) or agar gel immunodiffusion (AGID) tests and determination of protection following challenge with a high pathogenicity AI (HPAI) virus. In two different trials, chickens immunized with the rFP-H5 vaccine did not develop AGID antibodies because the vaccine lacks AI nucleoprotein and matrix genes, but 0%-100% had HI antibodies, depending on the AI virus strain used in the HI test, the HI antigen inactivation procedure, and whether the birds had been preimmunized against fowlpox virus. The most consistent and highest HI titers were observed when using A/turkey/Ireland/83 (H5N8) HPAI virus strain as the beta-propiolactone (BPL)-inactivated HI test antigen, which matched the hemagglutinin gene insert in the rFP-H5 vaccine. In addition, higher HI titers were observed if ether or a combination of ether and BPL-inactivated virus was used in place of the BPL-inactivated virus. The rFP-H5 vaccinated chickens survived HPAI challenge and antibodies were detected by both AGID and HI tests. In conclusion, we demonstrated that the rFP-H5 vaccine allowed easy serological differentiation of infected from noninfected birds in vaccinated populations of chickens when using standard AGID and HI tests.

Subtype AE HIV-1 DNA and recombinant Fowlpoxvirus vaccines encoding five shared HIV-1 genes: safety and T cell immunogenicity in macaques

To induce broad T cell immunity to HIV-1, we evaluated the safety, immunogenicity and dose–response relationship of DNA and recombinant Fowlpoxvirus (rFPV) vaccines encoding five shared HIV subtype AE genes (Gag, Pol, Env, Tat, Rev) in pigtail macaques. The DNA (three doses of either 1 mg or 4.5 mg) and rFPV (a single boost of either 5 × 10 7 or 2 × 10 8 plaque forming units) vaccines were administered intramuscularly without adjuvants. Broadly reactive HIV-specific T cell immunity was stimulated by all doses of the vaccines administered, without significant differences between the high and low doses studied. The vaccines induced both CD4 and CD8 T cell responses to Gag, Pol, Env and Tat/Rev proteins, with CD4 T cell responses being greater in magnitude than CD8 T cell responses. The vaccine-induced T cell responses had significant cross-recognition of heterologous HIV-1 proteins from non-AE HIV-1 subtypes. In conclusion, these subtype AE HIV-1 DNA and rFPV vaccines were safe, induced broad T-cell immunity in macaques, and are suitable for progression into clinical trials.

Failure of a Recombinant Fowl Poxvirus Vaccine Containing an Avian Influenza Hemagglutinin Gene to Provide Consistent Protection against Influenza in Chickens Preimmunized with a Fowl Pox Vaccine

Vaccines against mildly pathogenic avian influenza (AI) have been used in turkeys within the United States as part of a comprehensive control strategy. Recently, AI vaccines have been used in control programs against highly pathogenic (HP) AI of chickens in Pakistan and Mexico. A recombinant fowl pox-AI hemagglutinin subtype (H) 5 gene insert vaccine has been shown to protect specific-pathogen-free chickens from HP H5 AI virus (AIV) challenge and has been licensed by the USDA for emergency use. The ability of the recombinant fowl pox vaccine to protect chickens preimmunized against fowl pox is unknown. In the current study, broiler breeders (BB) and white leghorn (WL) pullets vaccinated with a control fowl poxvirus vaccine (FP-C) and/or a recombinant fowl poxvirus vaccine containing an H5 hemagglutinin gene insert (FP-HA) were challenged with a HP H5N2 AIV isolated from chickens in Mexico. When used alone, the FP-HA vaccine protected BB and WL chickens from lethal challenge, but when given as a secondary vaccine after a primary FP-C immunization, protection against a HP AIV challenge was inconsistent. Both vaccines protected against virulent fowl pox challenge. This lack of consistent protection against HPAI may limit use to chickens without previous fowl pox vaccinations. In addition, prior exposure to field fowl poxvirus could be expected to limit protection induced by this vaccine.

Efficacy of Recombinant Fowl Poxvirus Vaccine in Protecting Chickens against a Highly Pathogenic Mexican-Origin H5N2 Avian Influenza Virus

Internationally and nationally, governments and the poultry industries have used various strategies to control avian influenza (AI), ranging from a minimum of living with mildly pathogenic AI virus (AIV) infections to the other extreme of implementing a total quarantine-slaughter approach for eradication of highly pathogenic (HP) forms of the disease. However, recent economic considerations in various countries have prompted a broader reevaluation of vaccination as one of several tools to be used in AI control programs, including H5 and H7 HP AI. In the current study, 1-day-old chickens were immunized with a recombinant fowl poxvirus vaccine containing a hemagglutinin gene insert (Vector-HA) from an H5 AIV. Vector-HA- and negative control (vector-control)-vaccinated chicks were challenged with a HP H5N2 AIV isolated from chickens in Mexico. All immunized chickens were antibody negative on the agar gel precipitin test, indicating that vaccination would not interfere with routine AI serologic surveillance programs in the United States. However, in the hemagglutinin-inhibition test, a few immunized chickens (8%) had low serologic titers. Protection against illness (90-100%) and death (90-100%) was provided by the vector-HA vaccine from 3 wk of age to the end of the 20-wk study. The number of chickens shedding the challenge AIV from their enteric tracts was significantly reduced (50-75%) and the quantity of challenge AIV shed from respiratory and enteric tracts was significantly reduced (10(1)-10(2.1) mean embryo lethal dose/ml) in most vector-HA vaccine groups when compared with vector-control groups. Furthermore, vector-HA vaccination reduced in contact transmission of HP AI challenge virus to both vector-HA- and vector-control-vaccinated chickens. These findings indicate the recombinant fowl poxvirus vaccine can be a useful tool in an AI control program by preventing illness and death in chickens and reducing intestinal and respiratory shedding of H5 AIV. However, for an AI control program to be successful, enhanced biosecurity and surveillance must be practiced, and the vaccine's use must be controlled by an industry and/or government task force.

Recombinant fowlpox virus vaccines against Australian virulent Marek's disease virus: gene sequence analysis and comparison of vaccine efficacy in specific pathogen free and production chickens

We have cloned and sequenced the glycoprotein genes gB, gC and gD of the Australian virulent Marek's disease virus (MDV) isolate Woodlands No.1. The glycoprotein gB and gC sequences were identical to the homologs of other virulent MDV type 1 strains, and the glycoprotein gD sequence contained only one unique amino acid substitution. Recombinant fowlpox viruses (rFPVs) expressing the MDV glycoprotein genes were constructed and their efficacy as vaccines was evaluated in specific pathogen free (SPF) and production chickens. Vaccination with the FPV-gB recombinant protected SPF chickens from Marek's disease mortality and tumour formation following challenge with virulent MDV Woodlands No.1. The degree of protection from Marek's disease was dependent on the vaccine dose and route of inoculation. The rFPVs expressing gC or gD did not provide protection from Marek's disease. A rFPV expressing both gB and gC did not provide enhanced protection in comparison with the rFPV-gB alone. The rFPV-gB vaccine failed to protect commercial chickens from MD mortality and provided little protection from tumour formation in comparison with the commercial herpesvirus of turkey (HVT) vaccine. The failure to provide protection against MD may be related to the impact of maternally derived immunity to MDV and FPV and possibly the genotype of the chickens.

Influence of dose and route of inoculation on responses of chickens to recombinant fowlpox virus vaccines

The influence of dose and route of inoculation on responses of chickens to vaccination with recombinant fowlpox viruses (rFPVs) expressing an influenza haemagglutinin (HA) (FPV-HA) and the infectious bursal disease virus (IBDV) VP2 antigen (FPV-VP2) has been evaluated. Antibody responses to influenza and fowlpox virus were generated following vaccination via the wing web by subcutaneous inoculation or skin scarification. Intranasal and conjunctival inoculation failed to induce antibodies to FPV or influenza. Following direct intratracheal inoculation antibodies developed to influenza but not FPV. Dose response studies with the FPV-HA and FPV-VP2 recombinants showed that good responses to FPV and the vaccine antigen could be generated over a wide ( 100000 fold) dose range following wing web inoculation. The responses generated by the FPV-VP2 recombinant over this vaccine dose range protected against IBDV infection of the bursae following challenge with the Australian IBDV 002/73 isolate. These data suggest that effective application of rFPVs for poultry vaccination may be restricted to wing web and parenteral routes of inoculation.

Analysis of the Fowlpox Virus Genome Region Corresponding to the Vaccinia Virus D6 to A1 Region: Location of, and Variation in, Non-essential Genes in Poxviruses

The DNA sequence of the fowlpox virus genome corresponding to the vaccinia virus D6 to A1 region has been determined. Translation of this sequence reveals fowlpoxvirus gene homologues corresponding to the D6, D7, D9, D10, D11, D12, D13 and A1 genes of vaccinia virus. In contrast, no gene homologue for the non-essential vaccinia virus D8 gene was present in fowlpox virus. Instead, a gene transcribed from the opposite strand to the vaccinia virus D8 gene showing no homology to any previously sequenced poxvirus gene was present. The amino terminus of the fowlpox virus D9 homologue had undergone substantial changes, including frameshifts which would be predicted to inactivate the gene. Insertion of a gene cartridge composed of the vaccinia virus p7.5 promoter and the lacZ gene into the fowlpox virus D8, D9 and D10 genes in vitro, followed by recombination into fowlpox virus, was carried out. Stable insertion mutants with the correct genotype were obtained for D8 and D9 which, when tested in chickens did not appear to have been attenuated. No stable insertion mutants were obtained for D10, indicating that this gene probably encodes a function which is essential for virus replication. The D8 and D9 genes of fowlpox virus represent useful insertion sites for the construction of recombinant fowlpox virus vaccines.