Vaccine Technology – Guided Everything You Need To Know

No one doubts that targeted vaccines, also called recombinants, are here to stay in the poultry market. The truth is that they are effective tools and have important advantages when considering immune prevention programs for birds. The trend is to increasingly incorporate this technology into vaccination programs as producers clearly recognize the benefits.

Vector vaccine technology is a good example of the strong scientific development that is an inherent feature of the poultry sector. The concept of a viral vector was introduced in 1972, and in 1983 and 1984 a vector virus was used to develop a recombinant vaccine against influenza and rabies. In the poultry sector, research into vaccines using recombinant turkey herpes virus (rHVT) began in 1990.

A recombinant vaccine is the result of hybrid DNA molecules from 2 or more microorganisms expressed in a vector. These recombinant viruses act like a “Trojan horse” because the virus used as a vector will harbor parts of the introduction, and when the vector replicates in the host, exposure to the inserted proteins will occur. These proteins will be recognized by the bird’s immune system, generating protection against the antigens of two or more diseases. Thus, the recombinant vaccine is able to generate multivalent immunity and protection.

Currently in poultry, the two most common viruses used as vectors for commercially available recombinant vaccines are smallpox (yaws virus) and turkey herpes virus (HVT). These two viruses were selected for the development of vector vaccines because they possess large and phenotypically stable genomes, allowing portions of the insertions’ genetic material to be inserted, leading to the formation of the recombinant product. One goal of this technology is that the ‘virus’ that will be introduced into the vector will not be released into the external environment, as is the case with conventional live vaccines, resulting in a vaccine that is very safe from the point of view of reversing virulence without lateral transmission. In addition, recombinant vaccines have the advantage of not producing distinct post-vaccination unwanted reactions, especially in conventional vaccines against respiratory diseases, such as Newcastle disease and laryngitis.

Another relevant benefit of the vector vaccine technique is that administration can be conveniently performed as a single dose in the hatchery, either subcutaneously into a day-old chick or via in eggs. There is no interference from maternal antibodies in the replication of recombinant viral glycoproteins. This feature motivated the transfer of many conventional vaccines that were previously manufactured in the field by the method of mass application in multiple doses to the hatchery. The clearest example is the vaccination against Gumboro disease, which, in most producers, is effectively prevented with a single dose in the hatchery using complex or immunogenic vaccines. In this way, we can say that the recombinant vaccine technology produces “perfect mating” with the vaccination. in eggs Because we combine excellence in the process of administering the completed vaccine and the best control of the vaccination process with a safe and appropriate product. These two technologies used together are synergistic and result in greater safety for the immune system.

Protection with recombinant vaccines has already been scientifically demonstrated for the following diseases: Marek’s disease, bird pox, Gumborough disease, Newcastle disease, laryngitis and laryngotracheitis, avian influenza, and Mycoplasma gallissepticum. However, promising research is under development in order to produce new tools, including the use of different vectors, for example, adenovirus. It is important to note that each author product has unique properties. This uniqueness stems from the fact that there are differences in the genetic makeup of each product.

An essential step in developing a highly effective recombinant vaccine is the selection of glycoproteins with high immunogenicity for introduction into the vector. These proteins will be part of the external structure of the directed viruses and will trigger the immune response. Each flying virus contains one or more proteins that play a critical role in the immune response. The main immune antigen of the avian influenza virus is hemagglutinin. Of the Newcastle virus, are hemagglutinin – neuroaminidase and fusion protein; From the Gumboro virus, it is VP2; From laryngitis and tracheitis are g glycoproteins. The fusion protein is known to be more immunogenic for Newcastle disease than the hemagglutinin-neuraminidase protein, for example. Therefore, each product will have its own unique characteristic depending on the input of the gene used and the consequent expression of the protein with immunogenic potential. In addition, another important difference with respect to vector vaccines has to do with the catalyst used. In order for the expression of the inserted gene to occur, for example, the expression of the F protein of the DNC, it is also necessary to introduce the promoter gene into the transporter DNA. The promoter is the gene that will recruit a group of polymerases to produce the immune protein. Each product uses specific stimulants, which makes the vaccine property unique with respect to two key points: the generation of immunity (steady start) duration of immunity (duration of immunity).

emergence of immunity It can be defined as the speed with which full protection is achieved after the vaccine is given. Obviously, the faster the protection is generated, the lower the risk of disease. Previously duration of immunity It can be defined as the total protection generation time after The start of immunity. The longer the immunity, the more effective the vaccine, especially in long-lived birds such as whites and breeders. One of the biggest challenges in developing targeted vaccines is precisely the anticipation of The start of immunity and delay duration of immunity.

Advances in genetic engineering technology could increasingly improve the production and efficacy of recombinant vaccines, with the goal of offering viable alternatives to producers. One thing is certain: the development of poultry farming does not stop. It is an ongoing process.

Understanding how vector vaccines work, their properties, benefits, and limitations is essential to bird health.

* Director of Poultry Technical Services at Zoetis, veterinarian and veterinary pathologist.

View literature:

Francis MG. Spotlight on Avian Pathology: Importance of recombinant vector platform techniques in poultry immunization. Avian Pathology vol. 50, noThe 2, 109-111, 2021.

Hi R. and others. A review of recombinant poultry vector vaccines. bird diseases 65: 438-452, 2021.

Figure 1: Construction of a recombinant herpes virus (rHVT) directed vaccine. Source: huh and others. , 2021.

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