Field Study on the Immunological Response and Protective Effect of a Licensed Autogenous Vaccine to Control Streptococcus suis Infections in Post-Weaned Piglets.

Lorelei Corsaut,Guy Beauchamp,Marcelo Gottschalk,Mariela Segura,Marty Misener,Paisley Canning

doi:10.3390/vaccines8030384

Abstract

Streptococcus suis is one of the most important bacterial pathogens in weaned piglets and responsible for serious economic losses to the swine industry. Currently, mostly autogenous vaccines composed of killed bacteria (bacterins) are available. However, immunological and protective data from field studies are missing. We report for the first time a comparative field study on the immunological response induced by an autogenous vaccine applied to either piglets or sows in a farm with recurrent S. suis problems. (I) Piglets from non-vaccinated sows received an autogenous bacterin during the first week and at three weeks of age. (II) Sows received the vaccine at five and three weeks pre-farrowing and piglets were non-vaccinated. Levels, isotype profile and opsonophagocytosis capacity of the serum antibodies induced by vaccination were evaluated. Vaccination of piglets failed to induce an active immune response. Vaccination of sows induced a significant increase in anti-S. suis antibodies, mainly composed of IgG1. However, isotype switching was modulated by the S. suis serotype included in the vaccine formulation. Despite this antibody increase in vaccinated sows, transfer of maternal immunity to piglets was not different from the control group (i.e., piglets from non-vaccinated sows). Notably, levels of maternal antibodies in piglets were already very high with marked opsonophagocytosis capacity at one week of age, independently of the vaccination program. However, their levels decreased by three weeks of age, indicating possible absence of antibodies in the post-weaning high-risk period. These observations correlated with lack of clinical protection in the farm. Overall, a piglet or a sow vaccination program herein mostly failed to induce lasting protection in nursery piglets. An improvement of vaccine formulation or an optimized program may be required.

Highlights

IntroductionStreptococcus suis is responsible for important economic losses to the porcine industry worldwide [1]
Streptococcus suis is responsible for important economic losses to the porcine industry worldwide [1].It is one of the most important complications of infections caused by the porcine reproductive and respiratory syndrome virus (PRRSV) [1]
In the era of antibiotic restrictions, new social consumption trends and lack of efficacious commercial vaccines, autogenous bacterins dominate the market with the intention to control S. suis infection in pigs

Summary

Introduction

Streptococcus suis is responsible for important economic losses to the porcine industry worldwide [1]. It is one of the most important complications of infections caused by the porcine reproductive and respiratory syndrome virus (PRRSV) [1]. Clinical features associated with S. suis infection in pigs. 9) are recovered from diseased animals in Europe [3,4]. The situation is much complicated in North America, where many serotypes are routinely isolated from diseased pigs, without a clear predominance of a single serotype across the countries [5,6]. S. suis has been reported to be an emerging zoonotic pathogen with the greatest risk for people who have close contact with pigs or unprocessed pork such as, in Western countries, pig farmers and workers, butchers, meat inspectors and swine veterinarians

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