Oral vaccination of piglets against Mycoplasma hyopneumoniae using silica SBA-15 as an adjuvant effectively reduced consolidation lung lesions at slaughter

Marina L Mechler-Dreibi,Hélio J Montassier,Osvaldo A Sant’Anna,Luís Guilherme De Oliveira,Tereza S Martins,Henrique M S Almeida,Karina Sonalio,Beatriz B Zambotti,Mariela A C Martines,Fernando A M Petri,Márcia C A Fantini,Gabriel Y Storino,Marcela M Ferreira

doi:10.1038/s41598-021-01883-2

Abstract

Mycoplasma (M.) hyopneumoniae is the main pathogen of porcine enzootic pneumonia (PEP). Its controlling is challenging, and requires alternative strategies. This study aimed to develop an oral vaccine against M. hyopneumoniae using a nanostructured mesoporous silica (SBA-15) as an adjuvant, and compare its effect with an intramuscular (IM) commercial vaccine (CV). Fifty 24 day-old M. hyopneumoniae-free piglets composed five equal groups for different immunization protocols, consisting of a CV and/or oral immunization (OI). Control piglets did not receive any form of immunization. All piglets were challenged with M. hyopneumoniae strain 232 on D49 by tracheal route. IgA antibody response in the respiratory tract, bacterial shedding and serum IgG were evaluated. The piglets were euthanized on 28 (D77) and 56 (D105) days post-infection. Lung lesions were macroscopically evaluated; lung fragments and bronchoalveolar fluid (BALF) were collected for estimation of bacterial loads by qPCR and/or histopathology examination. All immunization protocols induced reduction on Mycoplasma-like macroscopic lung lesions. IgA Ab responses anti-M. hyopneumoniae, the expression of IL-4 cytokine and a lower expression of IL-8 were induced by CV and OI vaccines, while IgG was induced only by CV. Oral immunization using silica as a carrier-adjuvant can be viable in controlling M. hyopneumoniae infection.

Highlights

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the main causative pathogen of porcine enzootic pneumonia (PEP), a chronic respiratory disease in pigs, and one of the main pathogens involved in the porcine respiratory disease complex (PRDC)[1]
Many of these cells return to the original mucosal surface, but others can be found at different mucosal surfaces, so that oral immunization can lead to a migration of IgA precursor B cells to the bronchi, which subsequently secreted IgA antibodies in the bronchial mucosa[5]
Based on the importance of developing oral vaccine adjuvants that are efficient in presenting antigens to the cells of mucosal lymphoid tissues (MALT), the objectives of this study were (i) to develop an oral vaccine specific to M. hyopneumoniae by encapsulating a blend of proteins of this bacterium into the silica (SBA-15); (ii) to stimulate the immune responses of the respiratory mucosa; (iii) to evaluate the efficacy of the protection induced by this vaccine against experimental infection with a virulent strain of M. hyopneumoniae, compared to a commercial inactivated vaccine

Summary

Introduction

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the main causative pathogen of porcine enzootic pneumonia (PEP), a chronic respiratory disease in pigs, and one of the main pathogens involved in the porcine respiratory disease complex (PRDC)[1]. In the mucosal lymphoid tissues, mature T cells and B cells are stimulated by antigen and induce IgA antibody response. These cells migrate from the submucosal lymphoid tissue by the bloodstream to the lamina propria, where B cells differentiate into plasma cells secreting dimeric IgA antibodies. Many of these cells return to the original mucosal surface, but others can be found at different mucosal surfaces, so that oral immunization can lead to a migration of IgA precursor B cells to the bronchi, which subsequently secreted IgA antibodies in the bronchial mucosa[5]. An improvement in the recruitment of defense cells was observed, which led to an increase in phagocytosis and processing by the gut antigen-presenting c ells[17,18,19,20]

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