key: cord-0912357-d1pbys8x authors: BOYLE, D. B.; HEINE, H. G. title: Recombinant fowlpox virus vaccines for poultry date: 2017-12-22 journal: Immunol Cell Biol DOI: 10.1038/icb.1993.45 sha: 108aefaa643124d184a5b899e5b4c9b07ef5ef89 doc_id: 912357 cord_uid: d1pbys8x The intensive poultry industries rely heavily upon the use of vaccines for disease control. Viral vector based vaccines offer new avenues for the development of vaccines for effective disease control in poultry. Techniques developed for the construction of recombinant vaccinia viruses have been readily adapted to the construction of recombinant viruses based on fowlpox virus (rFPV). The ability to insert several genes into the large genome of fowlpox may enable the development of multivalent vaccines and vaccines incorporating immune response modifiers such as lymphokines. Newcastle disease, avian influenza, infectious bursal disease and Marek's disease antigens expressed by rFPV have been shown to be effective vaccines in poultry. None appear, however, to provide a substantial improvement in vaccine efficacy. Recombinant FPV will be a valuable adjunct to conventional vaccines currently in widespread use. Whether rFPV or other vector based vaccines can circumvent the problems of vaccination in the presence of high maternally derived antibodies is yet to be resolved. The observation that avipoxvirus recombinants may be suitable for the vaccination of non‐avian species provides an added dimension to vaccines based on FPV or other avipoxviruses. Recombinant FPV will find a useful role in poultry disease control when used in conjunction with conventional vaccines. spray). The majority of vaccines are used to control viral diseases and to be cost effective The intensive poultry industries (for meat and are based on live attenuated viruses. In layer egg production) rely heavily upon the use of and breeder birds, where it is desirable to vaccines for disease control. Because of the re-vaccinate to maintain protection and to cost competitive nature of these industries generate high levels of yolk sac antibodies to vaccines must be very cheap to purchase and protect hatching chickens, the primary live administer. In addition, to provide effective vims vaccines are usually followed by inactiprotection against disease the vaccines must be vated adjuvanted vaccines. The laying bird applicable at an early age -preferably at 1 day may receive as many as 10 to 20 vaccinations of age when the cost of vaccine administration during its production life, can also be kept low. One day old birds are The classical poultry pathogens of avian exposed to heavily contaminated environ-influenza (AI) and Newcastle disease viruses ments immediately they are placed in produc-(NDV) remain serious disease threats where tion sheds. If vaccines cannot be delivered at 1 they occur. Fortunately Australia has remained day of age, it is desirable that they be deliver-free of virulent NDV since the 1930s. We able by mass administration methods at later have, however, seen three outbreaks of AI in times (e.g. via the drinking water or by aerosol the past in Victoria. The development of recombinant vaccinia viruses''^ for the expression and delivery of vaccine antigens to mammalian species soon led to the realization that other host-specific viruses would also be suitable vectors for vaccine delivery. A number of viruses of poultry are being developed as potential vaccine vectors. Poxviruses, herpesvinises and adenoviruses appear to be the most attractive candidate vector viruses.^ Our work has concentrated on the development and evaluation of recombinant fowlpox viruses (rFPV) to deliver vaccine antigens to poultry. In this paper we review the efficacy of rFPV as poultry vaccines and attempt to compare their efficacy with currently available vaccines. The strategies adopted for the construction of rFPV are based on the approaches developed for vaccinia virus recombinants.'''^ Several sites have been used for the insertion of vaccine antigen genes including the thymidine kinase (TK) gene,^ the terminal inverted repeat regions,^ the site homologous to the vaccinia virus TK region from which the FPV TK appears to have been translocated^ and several sites identified by shot-gun insertion strategies.^ It is necessary to provide a poxvirus promoter to ensure expression of the inserted vaccine antigen. Promoters derived from FPV and other poxviruses all appear to operate to some level in rFPV.'° To facilitate rFPV construction and identification, dominant selectable makers have been developed.^ The P-galactosidase gene has been extensively used to allow rapid identification of recombinants using a chromogenic substrate.^ Details of rFPV construction strategies have recently been reviewed and will not be dealt with in detail here." As many of the rFPV reported have been constructed using different FPV parent strains, insertion sites and promoters it is very difficult to determine the impact of these features upon their efficacy for vaccination of poultry. For example, promoter strength may be an important issue regarding the quantity of vaccine antigen delivered"^ and insertions in some regions could lead to attenuation of the rFPV in comparison with the parent FPV strain used for recombinant construction. The residual virulence of the rFPV could have a significant impact upon vaccine efficacy. The primary target of IBDV (a birnavirus) infection is the bursa of Fabricius. Infection of young birds causes depletion of the germinal follicles leading to immunosuppression and susceptibility to other infections. Current vaccines are based on low virulence field strains as live vaccines or on inactivated virus derived from infected bursae. Protection of the young chick during the first 3-5 weeks of life relies on generation of high antibody titres in the hen and transfer of these to the hatching chick via the yolk sac of the egg. Current vaccines do not generate protective immunity in day old birds, particularly in the presence of the high levels of transferred maternal antibodies. Highly virulent strains of IBDV have emerged in Europe and Asia.^^ Unlike the previous strains, these highly virulent strains of IBDV directly cause significant levels of mortality in young birds. The VP2 protein of IBDV, previously shown to induce protective immunity in poultry, has been expressed by a rFPV as a fusion protein with (3-galactosidase.'^ When used to vaccinate 1 and 14 day old poultry this rFPV protected against mortality induced by the homologous IBDV strain or a highly virulent strain. It did not protect against bursal infection and damage. Our own studies with a rFPV expressing the VP2 protein from the Australian IBDV 002/73 strain have shown that this recombinant induces antibodies to IBDV, albeit at a level lower than an oil adjuvanted, killed IBDV vaccine.^" This FPV-VP2 recombinant did provide protection against bursal infection and damage by the homologous 002/73 strain in poultry vaccinated at 1 or 21 days of age. The level of protection was less than that provided by the oil adjuvanted, killed IBDV vaccine. Neither of the reported recombinant FPV-IBDV vaccines appears to be as effective as currently available vaccines. IBV (a coronavirus) is the cause of an acute, highly infectious respiratory disease in chickens. In Australia infection is also associated with a severe nephrosis. Production losses are associated with mortality, and in laying birds egg production drops occur with decrease in egg quality. Attenuated live viruses are used as vaccines for disease control. The complex serological and cross protection relationships of IBV isolates complicates the selection and use of strains for vaccination. Field experiences suggest vaccine failures are due to the emergence or selection of serotypes different from the vaccines in use. There is a need for improved IBV vaccines to provide broad protection and protection against emerging strains. The peplomer or spike protein of IBV expressed by vaccinia virus induced low level antibody responses in vaccinated mice.^T here have been no reports of successful use of rFPV expressing the peplomer antigen to protect chickens against challenge with IBV. We have successfully expressed the peplomer gene of IBV M41 strain in FPV. Expression of the antigen by both the vaccinia P.Ll 1 promoter and the P.E/L FPV promoter was demonstrated by immunofluorescence. We have failed, however, to demonstrate induction of antibodies or protective immune responses in poultry vaccinated with these rFPV (D. B. Boyle & H. G. Heine unpubl. obs. 1993). Because of the multiple and complex serotypes of IBV and the negative results with FPV recombinants to date, the prospects for new IBV vaccines based upon viral vectors appear remote at this time. Newcastle disease is considered to be the most significant exotic disease threat to the Australian poultry industries. Virus strains range from highly virulent to avirulent, however there is no strain specific immunity. All NDV vaccines protect against the different pathotypes. The strains of NDV present in Australian poultry flocks cause very minor or no disease problems. A wide variety of attenuated live and killed NDV vaccines are used outside Australia with the live attenuated vaccines being the most cost effective to deliver because they are very cheap to produce. Several research groups have reported the construction and evaluation of rFPV^''^~^°a nd pigeonpox virus^' expressing NDV genes and protection has been demonstrated with rFPV expressing either the haemagglutininneuraminidase (HN) or fusion (F) gene. Protection provided by FPV-F recombinants appeared better than that provided by FPV-HN recombinants.^^ The protection provided by FPV-NDV recombinants was not as good as that induced by conventional NDV vaccines (D. B. Boyle unpubl. obs. 1993). The combined use of conventional NDV and rFPV-NDV vaccines generated better immune responses than either alone.^Â Classical fowl plague is caused by Al viruses predominantly of the H5 or H7 haemaggluti-nin (HA) subtypes. Outbreaks of Al have occurred in southern Austraha on three occasions in the tjast: 1976, 1986 and 1992. Disease control has rehed upon quarantine and movement controls, and eradication has been achieved by slaughtering of all birds on infected farms. There are currently no commercially applicable vaccines available for the control of AL Recombinant FPV expressing the HA subtype H5 and the nucleoprotein (NP) of Al have been evaluated in poultry for vaccine efficacy.^^"^^ The HA H5 subtype expressed by FPV provided very good protection against Al disease in chickens and turkeys. In some but not all challenge situations Al virus replication and shedding was also substantially reduced. Protection -was subtype specific -with FPV-H5 recombinants protecting against H5 subtype viruses but not against H7 subtype virus. Immunization with a rFPV expressing the cross-reactive NP antigen did not provide protective immunity against Al. The results sliow that vaccination protection against Al is mediated by antibodies directed against the HA. Protection is provided against disease, but substantial virus replication and shedding can occur in the vaccinated and challenged bird. The failure of the NP to induce protection in poultry, in spite of its cross-reactivity across subtypes, reinforces the observations made in the mouse influenza model, where vaccinia virus NP recombinants failed to provide protection against disease and infection even though they were able to induce cross-reactive cytotoxic T lymphocytes "° "" [28] [29] [30] Marek's disease vaccine All of the currently available vaccines against MDV, with the exception of those based on the related HVT, are delivered as cellassociated viruses requiring storage and transport on liquid nitrogen. A rFPV expressing the glycoprotein B of MDV has been shown to induce neutralizing antibodies to MDV, to reduce levels of cell-associated viraemia and to protect against lymphoma and death caused by challenge with homologous and heterologous MDV strains, including highly virulent strains.^* Provided the FPV-MDV recombinant vaccines can provide protection against MDV in field applications, they may represent significant improvements over currently available vaccines. To provide protection as early as possible and to keep the costs of vaccine delivery as low as possible, the preferred time for primary application of many poultry vaccines is at 1 day of age, that is, when the birds leave the hatching incubators and immediately prior to placing in brooding and growing sheds. Vaccines applied at this age face two significant problems. The immunological immaturity of the day old birds reduces vaccine efficacy and maternally derived antibodies adsorbed via the yolk sac have the potential to interfere with active immunization at this early age. Some disease control strategies deliberately endeavour to maximize maternally derived antibodies by hyperimmunization of the laying hen to protect the newly hatched bird during the first 3-5 weeks of age. Vaccination is then carried out when maternally derived antibodies have waned sufficiently to no longer interfere with active immunization. In practice the proper timing of this vaccination is difficult since waning maternally derived protection can lead to a period in which many birds in a fiock are susceptible to infection prior to protection being conferred by active immunization. Those few studies that have been reported with vaccinia virus recombinants have shown that passively acquired antibodies to the coexpressed antigen inhibit the generation of active immunity to that antigen. Serum from influenza immune mice transferred to mice subsequently immunized with a vacciniainfiuenza HA recombinant suppressed the antibody response to the HA.^^ Vaccination of young infants who possess maternally derived antibodies to respiratory syncytial virus (RSV) with conventional RSV vaccines produces poor responses to the protective RSV glycoprotein antigens in spite of extensive replication of the virus. Cotton rats receiving hyperimmune serum to RSV glycoproteins prior to vaccination with vaccinia virus recombinants expressing RSV glycoproteins had suppressed antibody responses and were more susceptible to infection than control animals. Suppression was both qualitative and quantita-tive with the total antibody responses to the glycoproteins being suppressed and the suppression was selective for epitopes involved in induction of neutralizing antibodies.'^''"^'* Passively acquired antibodies to the vector may also lead to suppression of immune responses to the vector and co-expressed antigen.-'^ This immunosuppression appears to operate on both the B and T cell responses and may extend beyond the time after which residual maternally derived antibodies are no longer detectable.^^ Since application of poultry vaccines to 1 day old chickens is crucial to the successful control of disease in many cases, the impact of maternally derived antibodies upon vaccine efficacy warrants further detailed investigation. The proposal that recombinant avipoxviruses may be suitable for the vaccination of nonavian species provided an added dimension to vaccines based on FPV or other avipoxviruses.''* Recombinants expressing rabies and measles glycoproteins have been shown to be protective in non-avian species.•^^"'*° Recombinants based on canarypox were shown to be more effective than rFPV.^^ One of these recombinants has been evaluated in a Phase I human vaccination trial.^' Avipoxvirus infection of mammalian cell lines and animals fails to produce infectious progeny virus, yet expression of early gene products occurs, and so provides a substantial safety advantage over recombinants based upon viruses generating productive infections. Those studies reported to date on rFPV for vaccination of poultry suggest that they will be a valuable adjunct to conventional vaccines currently in widespread use. Some, such as Al, may provide a vaccine where none has existed before and others, such as MDV, may be significantly cheaper to produce and deliver. Where routes of inoculation have been compared, the most efficacious has been by wing web inoculation.^^ This has the disadvantages of being labour intensive, costly and best applied at 1 day of age. Mass vaccination strategies (e.g. via drinking water or aerosol) do not appear to be applicable to rFPV unless suitable FPV parent strains can be found. Vaccination and challenge experiments have shown that rFPV can induce protection against overt clinical disease. Their efficacy has not been directly compared with conventional vaccines and the longevity of responses has not been determined. With many poultry diseases, protection against disease alone is not sufficient to prevent production losses as infection without overt clinical disease may still lead to very significant production losses. Recombinant FPV may find a useful role in poultry disease control when used in conjunction with conventional vaccines. In the case of FPV-NDV recombinants the combined use of conventional and rFPV vaccines generated better immune responses than either alone.'^T he issue of whether rFPV or other vector based vaccines can circumvent the problems of vaccination in the face of high maternally derived antibodies is yet to be resolved but it remains a central issue in the application of vector based vaccines for poultry disease control. Other vector viruses (e.g. adenoviruses and herpesviruses) may be more suitable for mass administration in the face of maternally derived antibodies. However these vectors have yet to be fully established and evaluated. Recombinant FPV based vaccines do offer the potential to develop multivalent vaccines. Construction of poxviruses as cloning vectors: Insertion of the thymidine kinase gene from herpes simplex virus into the DNA of infectious vaccinia vims Vaccinia virus: A selectable eukaryotic cloning and expression vector Vectors for recombinant vaccine delivery Infectious recombinant vectored virus vaccines Vaccinia: Virus, vector, vaccine Construction of recombinant fowlpox viruses as vectors for poultry vaccines Insertion of the fusion gene from Newcastle disease vims into a nonessential region in the terminal repeats of fowlpox vims and demonstration of protective immunity induced by the recombinant Constmction of fowlpox vims vectors with intergenic insertions: Expression of the P-galactosidase gene and the measles vims fusion protein Recombinant fowlpox vims inducing protective immunity in non-avian species Quantitative assessment of poxvirus promoters in fowlpox and vaccinia vims recombinants Avipoxvims vectors Acute infectious bursal disease in poultry A recombinant fowlpox virus that expresses the VP2 antigen of infectious bursal disease virus induces protection against mortality caused by the vims Infectious bursal disease vims structural protein VP2 expressed by a fowlpox vims recombinant confers protection against disease in chickens Expression of the infectious bronchitis vims spike protein by recombinant vaccinia virus and induction of neutralizing antibodies in vaccinated mice Recombinant fowlpox viruses inducing protective immunity against Newcastle disease and fowlpox viruses A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase gene of Newcastle disease vims (NDV) protects chickens against challenge by NDV Newcastle disease virus fusion protein expressed in a fowlpox vims recombinant confers protection in chickens A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase gene of Newcastle disease vims (NDV) protects chickens against challenge by NDV Protection of chickens with a recombinant fowlpox vims expressing the Newcastle disease vims hemagglutinin-neuraminidase gene Constmction of a pigeonpox virus recombinant: Expression of the Newcastle disease vims (NDV) fusion glycoprotein and protection of chickens against Antibody response to Newcastle disease virus (NDV) of recombinant fowlpox vims (FPV) expressing a hemagglutinnin-neuraminidase of NDV into chickens in the presence of antibody to NDV and FPV Protective immunity against avian influenza induced by a fowlpox virus recombinant Vaccine Efficacy of nucleoprotein and haemagglutinin antigens expressed in fowlpox virus as vaccine for influenza in chickens Expression of avian influenza virus haemagglutinin by recombinant fowlpox virus Protection of chickens against highly pathogenic avian influenza virus (H5N2) by recombinant fowlpox viruses Effect of route of administration on the efficacy of a recombinant fowlpox virus against H5N2 avian influenza The roles of influenza virus haemagglutinin and nucleoprotein in protection: Analysis using vaccinia virus recombinants Efficacy of influenza haemagglutinin and nucleoprotein as protective antigens against influenza virus infection in mice Characterization and immunological properties of influenza A virus nucleoprotein (NP): Cell associated NP isolated from infected cells or viral NP expressed by vaccinia recombinant virus do not confer protection Protection against Marek's disease by a fowlpox virus recombinant expressing the glycoprotein B of Marek's disease virus Passive immune serum inhibits antibody response to recombinant vaccinia virus Passive transfer of respiratory syncytial virus (RSV) antiserum suppresses the immune response to the RSV fusion (F) and large (G) glycoproteins expressed by recombinant vaccinia viruses Immunosuppression of the antibody response to respiratory syncytial virus (RSV) by pre-existing serum antibodies: Partial prevention by topical infection of the respiratory tract with vaccinia virus-RSV recombinants Transfer of maternal antibodies results in inhibition of specific immune responses in the offspring Fowlpox virus as a vector for non-avian species Recombinant fowlpox virus inducing protective immunity in non-avian species Efficacy studies on a canarypoxrabies recombinant virus Immunisation of man with canarypox virus expressing rabies glycoprotein Fowlpox virus recombinant encoding the measles virus fusion protein: protection of mice against fatal measles encephalitis