Protection efficacy of the rLTB-R1 chimera against experimental swine mycoplasmal pneumonia

ABSTRACT

Background: Mycoplasma hyopneumoniae is the etiological agent of the Swine Mycoplasmal Pneumonia (SMP), one ofthe most economically significant diseases in the swine industry worldwide. Commonly used vaccines for SMP controlconsist of inactivated whole cells (bacterins). These vaccines are efficacious against M. hyopneumoniae challenge, but donot prevent colonization by the pathogen or completely eliminate pneumonia. P97 adhesin is conserved in the M. pneumoniae virulent strains, therefore it is an attractive target to be used in recombinant vaccines against M. hyopneumoniae.The aim of the present study was to evaluate protection afforded by rLTB-R1, a recombinant chimera composed by LTBfused with the R1 repeat region of P97 adhesin of M. hyopneumoniae, in specific-pathogen-free (SPF) piglets vaccinatedby intranasal or intramuscular route and challenged with a pathogenic strain of M. hyopneumoniae.Materials, Methods & Results: PCR products of the LTB and R1 coding sequences were fused, then cloned into pETDEST42™ expression vector. The rLTB-R1 was expressed in Escherichia coli BL21 (DE3) Salt induction (SI). The pigletswere divided into three groups four piglets were intranasally vaccinated with 1 mg of rLTB-R1 solubilized in 1 mL of PBSat 0 and 14 days (IN rLTB-R1 group); four piglets were intramuscularly vaccinated with 1 mg of rLTB-R1 solubilized in 1mL of PBS at 0 and 14 days (IM rLTB-R1 group); three piglets were intranasally and intramuscularly inoculated with 1 mLof PBS (control group). Two weeks after the last immunization (28 day), piglets were intratracheally challenged with 10 mLof a suspension containing 109 color-changing unit (CCU) of pathogenic M. hyopneumoniae 7448 strain on three consecutivedays. Until the challenge (28 days), intranasal and intramuscular vaccination with rLTB-R1 induced seroconversions of antiR1 systemic antibodies of 1.6 and 4.6 ×, respectively. The IN rLTB-R1...