A look back at the Autogenous vaccines inswine medicine: why and how?

Author: Gabriela Silva-Guerra, Swine and Poultry Infectious Diseases Research Center (CRIPA)

Article published in Porc Québec, March 2023, Volume 34 #1, Pages 34 to 37

This forum, organized by the Swine and Poultry Infectious Diseases Research Center (CRIPA) and supported by the Fonds de Recherche du Québec, was held on December 1, 2022. Invited experts discussed several important topics, such as new data on autogenous vaccines against the bacteria Streptococcus suis (S. suis) and Glaesserella parasuis (G. parasuis), the challenges of vaccination against swine influenza virus type A (VIPA) in North America, and field experiences with different types of autogenous vaccines (inactivated bacterial or viral vaccines and RNA particle vaccines).

Overview of the situation of autogenous vaccines against S. suis and G. parasuis

Dr. Marcelo Gottschalk and Dr. Mariela Segura (Université de Montréal) presented their laboratory and field studies on autogenous bacterins against S. suis. For the field studies, they evaluated the efficacy of vaccines from different pharmaceutical companies used in sows or piglets. The results led to five highlights:

Water-in-oil adjuvants appear to provide better protection against S. suis.
The use of culture supernatant (even very concentrated) in the vaccine preparation does not appear to increase protection compared to the vaccine prepared with killed and washed bacteria (bacterins).
The inclusion of multiple S. suis serotypes (multivalent vaccine) does not appear to affect protection against a specific serotype included in the vaccine.
When vaccinating sows, it is difficult to obtain high levels of maternal antibodies in piglets at 3–5 weeks of age. Thus, a sow vaccination program would potentially be more useful when clinical signs appear early post-weaning.
Vaccination of piglets between 1 and 3 weeks of age does not appear to result in the production of vaccine antibodies, unlike vaccination between 3 and 5 weeks. This could potentially be useful when clinical signs appear late in the post-weaning period.

Furthermore, the importance of comprehensive diagnostic procedures and appropriate scientific approach in vaccine efficacy studies (inclusion of control groups) was emphasized.

Dr. Eric Thibault and Dr. Hubert Gantelet (Ceva Santé Animale) shared with us some findings in Europe, including a desire by European authorities to secure the market by improving the quality and control of autogenous vaccines. Most autogenous vaccines are used against bacterial diseases, with S. suis being the priority target. In this regard, the Ceva team evaluated the immunogenicity of autogenous vaccines against S. suis in weaned piglets (in collaboration with the Université de Montréal). They concluded that the type of adjuvant used in the vaccine significantly influences the immune response against S. suis. In the same vein, Josh Elston and Dr. Andrea Pitkin (Newport Laboratories, USA) emphasized that the efficacy of vaccines against S. suis relies on the use of the right strains – requiring good diagnostic monitoring, the right adjuvant and the right antigenic concentration. Their field experiments reported that vaccination of sows and piglets reduced losses due to mortality caused by S. suis by 1.0–1.5%.

Dr. Brad Chappell presented the results of experiments conducted by the genetic company Topigs Norsvin Canada with different vaccines, both commercial and autogenous, against G. parasuis. Their field studies, comparing vaccine formulations with aluminum hydroxide or Emulsigen applied to weaned piglets, demonstrated that the latter induced significant seroconversion (high antibody levels) at 66 days of age compared to controls.

In light of the various conferences, everyone agrees on the importance of diagnostic work in order to identify and characterize the agents involved.

Better integration of autogenous vaccines to combat swine influenza

Dr. Marie Culhane (University of Minnesota) presented an overview of swine influenza in the United States. Multiple types of VIPA, including H1N1, H1N2, H3N2, and H3N1, are circulating in American herds. The development of a long-term VIPA control program must be based on epidemiological monitoring to document the genetic and antigenic evolution of the virus, and the creation of a bank of isolates to allow better selection of strains for vaccine formulation. They demonstrated that vaccination of sows against VIPA reduces the prevalence of infection by around 74% in piglets at weaning. Vaccination also reduces the risk of reassortant viruses.

Dr. Kevin Vilaça (South West Vets, Ontario) indicated that to control VIPA, it is also important to inform producers about the risk factors for this infection, provide each producer with reports specific to their herd, involve all producers in the control process and act proactively rather than reactively (vaccinate before problems appear). The South West Vets team has developed a database that now contains the sequences of over 400 Ontario strains of VIPA. The use of sequence comparison tools combined with the study of antigenic sites allows them to select the strains to include in the autoimmune. The objectives pursued are:

Have a multivalent vaccine that provides protection against the strains that are predominant in Ontario. A first “provincial” vaccine was approved for manufacturing in 2019;
Use the vaccine preventively before the disease strikes a herd;
Carry out continuous surveillance of circulating strains in order to rapidly identify emerging strains, and update the vaccine regularly;
Ensure collective immunity at the lowest cost, and with the least possible impact on production systems.

In Quebec, analysis of recent VIPA sequences suggests that a vaccine including 4 or 5 strains corresponding to 4-5 “clades” could be suitable.

Finally, Dr. Channing Sebo-Decker (Merck Animal Health, USA) presented the results obtained with the Sequivity technology, used to produce autogenous vaccines against VIPA and even other viruses such as porcine circoviruses and rotaviruses. The alleged advantages of this type of vaccine are a humoral and cellular immune response, the absence of antigenic competition with multi-strain formulations, extremely rare vaccine reactions and the possibility of differentiating infected from vaccinated animals (DIVA). In the case of VIPA, she emphasized the importance of “antigenic key sites” that determine the conformation of the hemagglutinin and the quality of the antibody response.

In light of the various conferences, everyone agrees on the importance of diagnostic work in order to identify and characterize the agents involved. We hope that the forum will have inspired all participants to persevere in their efforts to find solutions in the fight against infectious diseases.