Importance of a prime-boost DNA/protein vaccination to protect chickens against low-pathogenic H7 avian influenza infection

Vaccination with recombinant Lactococcus lactis expressing HA1-IgY Fc fusion protein provides protective mucosal immunity against H9N2 avian influenza virus in chickens

BACKGROUND

H9N2 virus is mainly transmitted through the respiratory mucosal pathway, so mucosal immunity is considered to play a good role in controlling avian influenza infection. It is commonly accepted that no adequate mucosal immunity is achieved by inactivated vaccines, which was widely used to prevent and control avian influenza virus infection. Thus, an improved vaccine to induce both mucosal immunity and systemic immunity is urgently required to control H9N2 avian influenza outbreaks in poultry farms.

METHODS

In this study, we constructed a novel Lactococcus lactis (L. lactis) strain expressing a recombinant fusion protein consisting of the HA1 proteins derived from an endemic H9N2 virus strain and chicken IgY Fc fragment. We evaluated the immunogenicity and protective efficacy of this recombinant L. lactis HA1-Fc strain.

RESULTS

Our data demonstrated that chickens immunized with L. lactis HA1-Fc strain showed significantly increased levels of serum antibodies, mucosal secretory IgA, T cell-mediated immune responses, and lymphocyte proliferation. Furthermore, following challenge with H9N2 avian influenza virus, chickens immunized with L. lactis HA1-Fc strain showed reduced the weight loss, relieved clinical symptoms, and decreased the viral titers and the pathological damage in the lung. Moreover, oropharyngeal and cloacal shedding of the H9N2 influenza virus was detected in chicken immunized with L. lactis HA1-Fc after infection, the results showed the titer was low and reduced quickly to reach undetectable levels at 7 days after infection.

CONCLUSION

Our data showed that the recombinant L. lactis HA1-Fc strain could induce protective mucosal and systemic immunity, and this study provides a theoretical basis for improving immune responses to prevent and control H9N2 virus infection.

Harnessing Recent Advances in Synthetic DNA and Electroporation Technologies for Rapid Vaccine Development Against COVID-19 and Other Emerging Infectious Diseases

DNA vaccines are considered as a third-generation vaccination approach in which antigenic materials are encoded as DNA plasmids for direct in vivo production to elicit adaptive immunity. As compared to other platforms, DNA vaccination is considered to have a strong safety profile, as DNA plasmids neither replicate nor elicit vector-directed immune responses in hosts. While earlier work found the immune responses induced by DNA vaccines to be sub-optimal in larger mammals and humans, recent developments in key synthetic DNA and electroporation delivery technologies have now allowed DNA vaccines to elicit significantly more potent and consistent responses in several clinical studies. This paper will review findings from the recent clinical and preclinical studies on DNA vaccines targeting emerging infectious diseases (EID) including COVID-19 caused by the SARS-CoV-2 virus, and the technological advancements pivotal to the improved responses-including the use of the advanced delivery technology, DNA-encoded cytokine/mucosal adjuvants, and innovative concepts in immunogen design. With continuous advancement over the past three decades, the DNA approach is now poised to develop vaccines against COVID-19, as well as other EIDs.

Vaccines against avian influenza in poultry

The review presents the latest data about the types of vaccines against avian influenza that are used in current medical practice or are under development. Inactivated whole virion vaccines, live vector vaccines, as well as experimental vaccines developed using genetic engineering techniques (e.g. subunit vaccines, VLP vaccines, DNA vaccines) were considered. The efficiency of influenza reverse genetic technology for the development of prototype vaccine strains was noted.

Evaluation of different chemical adjuvants on an avian influenza H6 DNA vaccine in chickens

This study assessed the ability of three adjuvants (aluminium hydroxide, Essai (microparticle) and Phema (nanoparticle)) to enhance the immune response of chickens to an H6N2 avian influenza DNA vaccine. No haemagglutination inhibition antibody was detected following two intramuscular immunizations with the adjuvanted and non-adjuvanted pCAG-HAk vaccine, which has previously been shown to induce moderate H6 haemagglutinin antibody response in SPF chickens. Following virus challenge, neither the vaccinated group without adjuvant nor the Essai-adjuvanted group showed a statistically significant reduction in virus shedding in oropharyngeal and cloacal swabs compared with the naive control group. However, the aluminium hydroxide and Phema-adjuvanted groups significantly reduced the frequency of virus shedding in oropharyngeal swabs, indicating that these adjuvants appeared to further enhance the vaccine potency. Aluminium hydroxide holds promise as an adjuvant for enhancing DNA-induced immune response in chickens owing to its low price and safety record.

DNA vaccination of poultry: The current status in 2015

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Poultry DNA vaccination studies are regularly being published since 1993.

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These studies are mainly, but not only, concerned with vaccination against viruses.

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The different strategies of improving DNA vaccine efficacies are presented.

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The fate of the vaccine plasmid, immune properties and other applications are described.

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Despite the compiling preclinical reports, a poultry DNA vaccine is yet unavailable in the market.

DNA vaccination is a promising alternative strategy for developing new human and animal vaccines. The massive efforts made these past 25 years to increase the immunizing potential of this kind of vaccine are still ongoing. A relatively small number of studies concerning poultry have been published. Even though there is a need for new poultry vaccines, five parameters must nevertheless be taken into account for their development: the vaccine has to be very effective, safe, inexpensive, suitable for mass vaccination and able to induce immune responses in the presence of maternal antibodies (when appropriate). DNA vaccination should meet these requirements. This review describes studies in this field performed exclusively on birds (chickens, ducks and turkeys). No evaluations of avian DNA vaccine efficacy performed on mice as preliminary tests have been taken into consideration. The review first describes the state of the art for DNA vaccination in poultry: pathogens targeted, plasmids used and different routes of vaccine administration. Second, it presents strategies designed to improve DNA vaccine efficacy: influence of the route of administration, plasmid dose and age of birds on their first inoculation; increasing plasmid uptake by host cells; addition of immunomodulators; optimization of plasmid backbones and codon usage; association of vaccine antigens and finally, heterologous prime-boost regimens. The final part will indicate additional properties of DNA vaccines in poultry: fate of the plasmids upon inoculation, immunological considerations and the use of DNA vaccines for purposes other than preventing infectious diseases.

Vaccination with recombinant 4 × M2e.HSP70c fusion protein as a universal vaccine candidate enhances both humoral and cell-mediated immune responses and decreases viral shedding against experimental challenge of H9N2 influenza in chickens

As cellular immunity is essential for virus clearance, it is commonly accepted that no adequate cellular immunity is achieved by all available inactivated HA-based influenza vaccines. Thus, an improved influenza vaccine to induce both humoral and cell-mediated immune responses is urgently required to control LPAI H9N2 outbreaks in poultry farms. M2e-based vaccines have been suggested and developed as a new generation of universal vaccine candidate against influenza A infection. Our previous study have shown that a prime-boost administration of recombinant 4×M2e.HSP70c (r4M2e/H70c) fusion protein compared to conventional HA-based influenza vaccines provided full protection against lethal dose of influenza A viruses in mice. In the present study, the immunogenicity and protective efficacy of (r4M2e/H70c) was examined in chickens. The data reported herein show that protection against H9N2 viral challenge was significantly increased in chickens by injection of r4M2e/H70c compared with injection of conventional HA-based influenza vaccine adjuvanted with MF59 or recombinant 4×M2e (r4M2e) without HSP70c. Oropharyngeal and cloacal shedding of the virus was detected in all of the r4M2e/H70c vaccinated birds at 2 days after challenge, but the titer was low and decreased rapidly to reach undetectable levels at 7 days after challenge. Moreover, comparison of protective efficacy against LPAI H9N2 in birds intramuscularly immunized with r4M2e/H70c likely represented the ability of the M2e-based vaccine in providing cross-protection against heterosubtypic H9N2 challenge and also allowed the host immune system to induce HA-homosubtype neutralizing antibody against H9N2 challenge. This protective immunity might be attributed to enhanced cell-mediated immunity, which is interpreted as increased lymphocytes proliferation, increased levels of Th1-type (IFN-γ) and Th2-type (IL-4) cytokines production and increased CD4(+) to CD8(+) ratios, resulting from the injection of four tandem repeats of the ectodomain of the conserved influenza matrix protein M2 (4×M2e) genetically fused to C-terminus of Mycobacterium tuberculosis HSP70 (mHSP70c).

Prevalence and control of H7 avian influenza viruses in birds and humans

The H7 subtype HA gene has been found in combination with all nine NA subtype genes. Most exhibit low pathogenicity and only rarely high pathogenicity in poultry (and humans). During the past few years infections of poultry and humans with H7 subtypes have increased markedly. This review summarizes the emergence of avian influenza virus H7 subtypes in birds and humans, and the possibilities of its control in poultry. All H7Nx combinations were reported from wild birds, the natural reservoir of the virus. Geographically, the most prevalent subtype is H7N7, which is endemic in wild birds in Europe and was frequently reported in domestic poultry, whereas subtype H7N3 is mostly isolated from the Americas. In humans, mild to fatal infections were caused by subtypes H7N2, H7N3, H7N7 and H7N9. While infections of humans have been associated mostly with exposure to domestic poultry, infections of poultry have been linked to wild birds or live-bird markets. Generally, depopulation of infected poultry was the main control tool; however, inactivated vaccines were also used. In contrast to recent cases caused by subtype H7N9, human infections were usually self-limiting and rarely required antiviral medication. Close genetic and antigenic relatedness of H7 viruses of different origins may be helpful in development of universal vaccines and diagnostics for both animals and humans. Due to the wide spread of H7 viruses and their zoonotic importance more research is required to better understand the epidemiology, pathobiology and virulence determinants of these viruses and to develop improved control tools.

Passive antibody transfer in chickens to model maternal antibody after avian influenza vaccination

Birds transfer maternal antibodies (MAb) to their offspring through the egg yolk where the antibody is absorbed and enters the circulatory system. Maternal antibodies provide early protection from disease, but may interfere with the vaccination efficacy in the chick. MAb are thought to interfere with vaccine antigen processing that reduces the subsequent immune response. Once MAb titers are depleted, the chick will respond to vaccination, but they are also susceptible to viral infection. This study examines the effect of MAb on seroconversion to different viral-vectored avian influenza virus (AIV) vaccines. Chicks were given passively transferred antibodies (PTA) using AIV hyperimmunized serum, and subsequently vaccinated with a fowlpox-AIV recombinant vaccine (FPr) or a Newcastle disease virus-AIV recombinant vaccine (NDVr). Our results indicate that passively transferred antibodies led to significant reduction of seroconversion and clinical protection from virulent challenge in recombinant virus vaccinated chicks thus demonstrating maternal antibody interference to vaccination. The passive antibody transfer model system provides an important tool to evaluate maternal antibody interference to vaccination.

Protective efficacy of a broadly cross-reactive swine influenza DNA vaccine encoding M2e, cytotoxic T lymphocyte epitope and consensus H3 hemagglutinin

BACKGROUND

Pigs have been implicated as mixing reservoir for the generation of new pandemic influenza strains, control of swine influenza has both veterinary and public health significance. Unlike human influenza vaccines, strains used for commercially available swine influenza vaccines are not regularly replaced, making the vaccines provide limited protection against antigenically diverse viruses. It is therefore necessary to develop broadly protective swine influenza vaccines that are efficacious to both homologous and heterologous virus infections. In this study, two forms of DNA vaccines were constructed, one was made by fusing M2e to consensus H3HA (MHa), which represents the majority of the HA sequences of H3N2 swine influenza viruses. Another was made by fusing M2e and a conserved CTL epitope (NP147-155) to consensus H3HA (MNHa). Their protective efficacies against homologous and heterologous challenges were tested.

RESULTS

BALB/c mice were immunized twice by particle-mediated epidermal delivery (gene gun) with the two DNA vaccines. It was shown that the two vaccines elicited substantial antibody responses, and MNHa induced more significant T cell-mediated immune response than MHa did. Then two H3N2 strains representative of different evolutional and antigenic clusters were used to challenge the vaccine-immunized mice (homosubtypic challenge). Results indicated that both of the DNA vaccines prevented homosubtypic virus infections completely. The vaccines' heterologous protective efficacies were further tested by challenging with a H1N1 swine influenza virus and a reassortant 2009 pandemic strain. It was found that MNHa reduced the lung viral titers significantly in both challenge groups, histopathological observation showed obvious reduction of lung pathogenesis as compared to MHa and control groups.

CONCLUSIONS

The combined utility of the consensus HA and the conserved M2e and CTL epitope can confer complete and partial protection against homologous and heterologous challenges, respectively, in mouse model. This may provide a basis for the development of universal swine influenza vaccines.

Prophylactic treatment with Toll-like receptor ligands enhances host immunity to avian influenza virus in chickens

Avian influenza viruses (AIV) pose a threat towards the health of both poultry and humans. To interrupt the transmission of the virus, novel prophylactic strategies must be considered which may reduce the shedding of AIV. One potential is the prophylactic use of Toll-like receptor (TLR) ligands. Many cells of the immune system express TLRs, and cellular responses to TLR stimulation include activation and the production of cytokines. TLR ligands have been employed as prophylactic treatments to enhance host resistance to pathogens both in mammals and chickens. Therefore, the present study was conducted to determine whether TLR ligands may be used prophylactically in chickens to enhance host immunity to AIV. Chickens received intramuscular injections of either low or high doses of the TLR ligands poly I:C, lipopolysaccharide (LPS) and CpG ODN. Twenty-four hours post-treatment, chickens were infected with the low pathogenic avian influenza virus H4N6, and both oropharyngeal and cloacal virus shedding were assessed on days 4 and 7 post-infection. To identify potential correlates of immunity, spleen and lungs were collected on days 2, 4 and 7 post-infection for RNA extraction. The results suggested that all of the TLR ligand treatments induced a significant reduction in virus shedding, with the TLR3 ligand poly I:C conferring the greatest AIV immunity compared to control birds, followed by CpG ODN and LPS. Furthermore, transcriptional analysis of gene expression in the spleen and lungs suggest IFN-α and IL-8 as correlates of immunity conferred by poly I:C, and IFN-γ for CpG ODN and LPS. In conclusion, TLR ligands, have the ability to enhance host immunity against AIV, and future studies should consider exploring the combinatory effects of poly I:C and CpG ODN prophylaxis in conjunction with AIV vaccination.

A Novel Vaccine Using Nanoparticle Platform to Present Immunogenic M2e against Avian Influenza Infection

Using peptide nanoparticle technology, we have designed two novel vaccine constructs representing M2e in monomeric (Mono-M2e) and tetrameric (Tetra-M2e) forms. Groups of specific pathogen free (SPF) chickens were immunized intramuscularly with Mono-M2e or Tetra-M2e with and without an adjuvant. Two weeks after the second boost, chickens were challenged with 107.2 EID50 of H5N2 low pathogenicity avian influenza (LPAI) virus. M2e-specific antibody responses to each of the vaccine constructs were tested by ELISA. Vaccinated chickens exhibited increased M2e-specific IgG responses for each of the constructs as compared to a non-vaccinated group. However, the vaccine construct Tetra-M2e elicited a significantly higher antibody response when it was used with an adjuvant. On the other hand, virus neutralization assays indicated that immune protection is not by way of neutralizing antibodies. The level of protection was evaluated using quantitative real time PCR at 4, 6, and 8 days post-challenge with H5N2 LPAI by measuring virus shedding from trachea and cloaca. The Tetra-M2e with adjuvant offered statistically significant (P < 0.05) protection against subtype H5N2 LPAI by reduction of the AI virus shedding. The results suggest that the self-assembling polypeptide nanoparticle shows promise as a potential platform for a development of a vaccine against AI.

Development of avian influenza virus H5 DNA vaccine and MDP-1 gene of Mycobacterium bovis as genetic adjuvant

Background

Studies have shown that DNA vaccines can induce protective immunity, which demonstrated the high potential of DNA vaccines as an alternative to inactivated vaccines. Vaccines are frequently formulated with adjuvants to improve their release, delivery and presentation to the host immune system.

Methods

The H5 gene of H5N1 virus (A/Ck/Malaysia/5858/04) was cloned separately into pcDNA3.1 + vector. The immunogenicity of the cloned H5 DNA vaccine was tested on SPF chickens using two different approaches. First approach was using H5 DNA vaccine (pcDNA3.1/H5) and the second was using H5 DNA vaccine in addition to the pcDNA3.1/MDP1 vaccine. Ten days old chickens inoculated three times with two weeks intervals. The spleen and muscle samples from chickens immunized with H5 (pcDNA3.1/H5) and H5 + MDP1 (pcDNA3.1/H5 + pcDNA3.1/MDP1) vaccines were collected after sacrificing the chickens and successfully expressed H5 and MDP1 RNA transcripts. The sera of immunized chickens were collected prior to first immunization and every week after immunization; and analyzed using enzyme-linked immunosorbent assay (ELISA) and hemagglutination inhibition (HI) test.

Results

Results of competitive ELISA showed successful antibody responses two weeks post immunization. The HI test showed an increased in antibody titers during the course of experiment in group immunized with H5 and H5 + MDP1 vaccines. The result showed that the constructed DNA vaccines were able to produce detectable antibody titer in which the group immunized with H5 + MDP1 vaccine produced higher antibody comparing to H5 vaccine alone.

Conclusions

This study shows for the first time the usefulness of MDP1 as a genetic adjuvant for H5 DNA vaccine.

Enhanced immunity against classical swine fever in pigs induced by prime-boost immunization using an alphavirus replicon-vectored DNA vaccine and a recombinant adenovirus

Classical swine fever (CSF) - caused by the classical swine fever virus (CSFV) - is a fatal disease of pigs that is responsible for extensive losses to the swine industry worldwide. We had demonstrated previously that a prime-boost vaccination strategy using an alphavirus (Semliki Forest virus, SFV) replicon-vectored DNA vaccine (pSFV1CS-E2) and a recombinant adenovirus (rAdV-E2) expressing the E2 glycoprotein of CSFV induced enhanced immune responses in a mouse model. In this study, we evaluated further the efficacy of the heterologous prime-boost immunization approach in pigs, the natural host of CSFV. The results showed that the pigs (n=5) receiving pSFV1CS-E2/rAdV-E2 heterologous prime-boost immunization developed significantly higher titers of CSFV-specific neutralizing antibodies and comparable CD4(+) and CD8(+) T-cell proliferation, compared to the pigs receiving double immunizations with rAdV-E2 alone. When challenged with virulent CSFV Shimen strain, the pigs of the heterologous prime-boost group did not show clinical symptoms or viremia, which were observed in one of the 5 pigs immunized with rAdV-E2 alone and all the 5 control pigs immunized with an empty adenovirus. The results demonstrate that the heterologous DNA prime and recombinant adenovirus boost strategy can induce solid protective immunity.

Prime-boost immunization using a DNA vaccine delivered by attenuated Salmonella enterica serovar typhimurium and a killed vaccine completely protects chickens from H5N1 highly pathogenic avian influenza virus

H5N1 highly pathogenic avian influenza virus (HPAIV) has posed a great threat not only for the poultry industry but also for human health. However, an effective vaccine to provide a full spectrum of protection is lacking in the poultry field. In the current study, a novel prime-boost vaccination strategy against H5N1 HPAIV was developed: chickens were first orally immunized with a hemagglutinin (HA) DNA vaccine delivered by attenuated Salmonella enterica serovar Typhimurium, and boosting with a killed vaccine followed. Chickens in the combined vaccination group but not in single vaccination and control groups were completely protected against disease following H5N1 HPAIV intranasal challenge, with no clinical signs and virus shedding. Chickens in the prime-boost group also generated significantly higher serum hemagglutination inhibition (HI) titers and intestinal mucosal IgA titers against avian influenza virus (AIV) and higher host immune cellular responses than those from other groups before challenge. These results demonstrated that the prime-boost vaccination strategy provides an effective way to prevent and control H5N1 highly pathogenic avian influenza virus.

DNA vaccines in veterinary use

DNA vaccines represent a new frontier in vaccine technology. One important application of this technology is in the veterinary arena. DNA vaccines have already gained a foothold in certain fields of veterinary medicine. However, several important questions must be addressed when developing DNA vaccines for animals, including whether or not the vaccine is efficacious and cost effective compared with currently available options. Another important question to consider is how to apply this developing technology in a wide range of different situations, from the domestic pet to individual fish in fisheries with several thousand animals, to wildlife programs for disease control. In some cases, DNA vaccines represent an interesting option for vaccination, while in others, currently available options are sufficient. This review will examine a number of diseases of veterinary importance and the progress being made in DNA vaccine technology relevant to these diseases, and we compare these with the conventional treatment options available.

A live attenuated H7N3 influenza virus vaccine is well tolerated and immunogenic in a Phase I trial in healthy adults

BACKGROUND

Live attenuated influenza vaccines (LAIVs) are being developed and tested against a variety of influenza viruses with pandemic potential. We describe the results of an open-label Phase I trial of a live attenuated H7N3 virus vaccine.

METHODS AND FINDINGS

The H7N3 BC 2004/AA ca virus is a live attenuated, cold-adapted, temperature-sensitive influenza virus derived by reverse genetics from the wild-type low pathogenicity avian influenza virus A/chicken/British Columbia/CN-6/2004 (H7N3) and the A/AA/6/60 ca (H2N2) virus that is the Master Donor Virus of the live, intranasal seasonal influenza vaccine. We evaluated the safety, infectivity, and immunogenicity of two doses of 10(7.5)TCID(50) of the vaccine administered by nasal spray 5 weeks apart to normal healthy seronegative adult volunteers in an inpatient isolation unit. The subjects were followed for 2 months after one dose of vaccine or for 4 weeks after the second dose. Twenty-one subjects received the first dose of the vaccine, and 17 subjects received two doses. The vaccine was generally well tolerated. No serious adverse events occurred during the trial. The vaccine was highly restricted in replication: 6 (29%) subjects had virus recoverable by culture or by real-time reverse transcription polymerase chain reaction (rRT-PCR) after the first dose. Replication of vaccine virus was not detected following the second dose. Despite the restricted replication of the vaccine, 90% of the subjects developed an antibody response as measured by any assay: 62% by hemagglutination inhibition assay, 48% by microneutralization assay, 48% by ELISA for H7 HA-specific serum IgG or 71% by ELISA for H7 HA-specific serum IgA, after either one or two doses. Following the first dose, vaccine-specific IgG secreting cells as measured by ELISPOT increased from a mean of 0.1 to 41.6/10(6) PBMCs; vaccine-specific IgA secreting cells increased from 2 to 16.4/10(6) PBMCs. The antibody secreting cell response after the second dose was less vigorous, which is consistent with the observed low replication of vaccine virus after the second dose and consequent lower antigenic stimulation.

CONCLUSION

The live attenuated H7N3 vaccine was generally well tolerated but was highly restricted in replication in healthy seronegative adults. Despite the restricted replication, the vaccine was immunogenic, with serum IgA being the most sensitive measure of immunogenicity. Further development of this vaccine is warranted (ClinicalTrials.gov Identifier: NCT00516035).

Influenza vaccines for avian species

Beginning in Southeast Asia in 2003, a multinational epizootic outbreak of H5N1 highly pathogenic avian influenza (HPAI) was identified in commercial poultry and wild bird species. This lineage, originally identified in Southern China in 1996 and then Hong Kong in 1997, caused severe morbidity and mortality in many bird species, was responsible for considerable economic losses via trade restrictions, and crossed species barriers (including its recovery from human cases). To date, these H5N1 HPAI viruses have been isolated in European, Middle Eastern, and African countries, and are considered endemic in many areas where regulatory control and different production sectors face substantial hurdles in controlling the spread of this disease. While control of avian influenza (AI) virus infections in wild bird populations may not be feasible at this point, control and eradiation of AI from commercial, semicommercial, zoo, pet, and village/backyard birds will be critical to preventing events that could lead to the emergence of epizootic influenza virus. Efficacious vaccines can help reduce disease, viral shedding, and transmission to susceptible cohorts. However, only when vaccines are used in a comprehensive program including biosecurity, education, culling, diagnostics and surveillance can control and eradication be considered achievable goals. In humans, protection against influenza is provided by vaccines that are chosen based on molecular, epidemiologic, and antigenic data. In poultry and other birds, AI vaccines are produced against a specific hemagglutinin subtype of AI, and use is decided by government and state agricultural authorities based on risk and economic considerations, including the potential for trade restrictions. In the current H5N1 HPAI epizootic, vaccines have been used in a variety of avian species as a part of an overall control program to aid in disease management and control.

Influenza vaccines and vaccination strategies in birds

Although it is well accepted that the present Asian H5N1 panzootic is predominantly an animal health problem, the human health implications and the risk of human pandemic have highlighted the need for more information and collaboration in the field of veterinary and human health. H5 and H7 avian influenza (AI) viruses have the unique property of becoming highly pathogenic (HPAI) during circulation in poultry. Therefore, the final objective of poultry vaccination against AI must be eradication of the virus and the disease. Actually, important differences exist in the control of avian and human influenza viruses. Firstly, unlike human vaccines that must be adapted to the circulating strain to provide adequate protection, avian influenza vaccination provides broader protection against HPAI viruses. Secondly, although clinical protection is the primary goal of human vaccines, poultry vaccination must also stop transmission to achieve efficient control of the disease. This paper addresses these differences by reviewing the current and future influenza vaccines and vaccination strategies in birds.