One improvement that it was fundamental to introduce into the formulation of the immune-complex vaccines was the control of the correct coating of the virus particles.

Two new controls have been recently developed in a newly formulated immune-complex vaccine (GUMBOHATCH®, an innovative IBD immune-complex vaccine against Gumboro disease) to achieve this:

• Control of free IgY: this control determines that there are still free Ig Y in the final vaccine suspension, which means that all vaccine particles are necessarily completely coated.

• Neutralization control: this control means the inoculation of the immune-complex to embryonated eggs to prove that all vaccine particles have been “neutralized” through the complete coating with antibodies.

However, other new tests and improvements in the formula have been introduced in order to achieve a better and more consistent production process of the immune-complex vaccines:

• Mixture with fresh virus: immune-complex vaccines are formulated on the basis of adding a specific proportion of antibodies depending on the initial titre of the vaccine harvest. This initial titration means a waiting time of 6-7 days between the harvest production and the final mixture with antibodies and the virus is usually frozen in the meantime. The new formulation tries to avoid this waiting time, which can mean loss of virus potency, by formulating the mixture with fresh virus and adding a proportion of antibodies taking account of the maximum range of the harvest titration.

• IgY of egg origin: until now, all commercial immune-complex vaccines have used the IgY extracted from the serum of hyperimmunized animals as coating antibodies. A new procedure for extracting the IgY from the eggs has been developed in order to improve the consistency and capacity for production of the highest quality antibodies (among other advantages).

• Potency Units test: this test involves direct titration of the virus in the form of immune-complex after the freeze-drying process, so it is a direct detection of the potency of the freeze-dried vaccine. This test replaces the indirect titration offered by the CID₅₀.

All these new improvements have resulted in a newly formulated immune-complex vaccine (GUMBOHATCH®) which ensures maintenance of the maximum potency of the vaccine and consistent results in the field.

REFERENCES:

¹Whitfill et al. 1995. Avian Diseases 39, 4, 687-699.

²Jeuriseen et al. 1998. Immunology 95, 494–500.

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