Immunogenicity and efficacy of a Mycoplasma hyopneumoniae/porcine circovirus type 2 combination vaccine against experimental Mycoplasma hyopneumoniae infection in pigs.

Abstract

Vaccination is an important control measure against infections with Mycoplasma hyopneumoniae (M. hyopneumoniae), the primary pathogen of enzootic pneumonia in pigs. The present study investigated local and systemic humoral and cell-mediated immune responses and efficacy upon vaccination of piglets with a combined vaccine containing inactivated M. hyopneumoniae and porcine circovirus 2d (Cirbloc^® M Hyo, Ceva), followed by experimental M. hyopneumoniae infection (D21). Forty-five piglets were allocated to three groups, namely the not-vaccinated and infected (C) (n = 20), vaccinated and infected (V) (n = 20), and not-vaccinated and not-infected (NC) groups (n = 5). Vaccination was applied once (D0) intramuscularly. Four pigs from the V and C groups were euthanized 2 weeks post-infection (D35), and the remaining pigs 2 weeks later (D49). Blood, lung tissue, bronchoalveolar lavage fluid (BALF), and bronchial lymph nodes were collected at different timepoints. Piglets in the V group exhibited seroconversion on days 21 and 35, with markedly elevated levels of specific IgA and IgG in BALF on D35. Furthermore, the V group showed activation of interferon (IFN)-γ⁺/tumor necrosis factor (TNF)-α⁺ CD4⁺CD8α⁺ T cells and T cell proliferation on day 7, with these responses remaining elevated through D21. The concentrations of interleukin (IL)-1β, TNF-α, C-X-C motif chemokine ligand 8 (CXCL-8), and IL-17A in BALF of the C group were higher on D49, correlating with higher M. hyopneumoniae DNA loads. Clinical signs and lung lesions were less severe in vaccinated pigs. The combined vaccine elicited robust M. hyopneumoniae-specific humoral and cellular responses in blood and enhanced post-infection cellular immunity in draining lymph nodes, underscoring its protective efficacy.