Construction and Characterization of an Actinobacillus pleuropneumoniae Serotype 2 Mutant Lacking the Apx Toxin Secretion Protein Genes apxIIIB and apxIIID

Abstract

Apx toxins have been identified as important virulence factors of Actinobacillus pleuropneumoniae, the etiologic agent of porcine pleuropneumonia. In some A. pleuropneumoniae serotypes, Apx toxins are secreted by the cell membrane proteins encoded by apxIIIB and apxIIID genes. In an effort to develop a live vaccine strain against A. pleuropneumoniae, we inactivated the apxIIIB and apxIIID genes in A. pleuropneumoniae 1536, a serotype 2 strain, resulting in the DeltaapxIIIB/DapxIIID mutant strain (1536DeltaBDeltaD). Immunization of pigs with live 1536DeltaBDeltaD A. pleuropneumoniae conferred protection against homologous challenge with wild-type A. pleuropneumoniae 1536. Thus, impaired Apx toxin secretion may decrease the virulence of A. pleuropneumoniae and may be an effective strategy for the development of a live-attenuated A. pleuropneumoniae vaccine.

Construction and immunization with double mutant ΔapxIBD Δpnp forms of Actinobacillus pleuropneumoniae serotypes 1 and 5

“…with the parental strain [31]. Thus, our mutants were highly attenuated, and these results confirmed the important roles of the ApxI and ApxII toxins in the virulence of wild-type APP1 and APP5.…”

A recombinant chimera comprising the R1 and R2 repeat regions of M. hyopneumoniae P97 and the N-terminal region of A. pleuropneumoniaeApxIII elicits immune responses

“…The A. pleuropneumoniae strain was cultured in pleuropneumonia-like organism (PPLO) media (BD Biosciences, Sparks, MD) supplemented with 10 μg/ml nicotinamide dinucleotide, 260 μg/ml L-cysteine hydrochloride, 1 mg/ml dextrose, 10 μg/ml L-cysteine dihydrochloride, 0.6 mM glutamine, and 0.1% Tween 80 at 37°C with continuous shaking [32]. For whole-cell lysate preparations, A. pleuropneumoniae was cultured to mid-log phase and collected by centrifugation at 3,000 × g for 10 min.…”

Detection of Actinobacillus pleuropneumoniae through Duplex PCR Based on ApxIA and ApxIVA Genes

“…RTX toxins are the main factors of Actinobacillus pleuropneumoniae § These authors contributed equally to this work. virulence and the virulence level of each Actinobacillus pleuropneumoniae serotype may be directly related to the presence of Apx toxins (Park et al, 2009;Hsu et al, 2016;Hathroubi et al, 2017). ApxIA is a strongly hemolytic and cytotoxic 105-kDa protein (Frey, 1995;Liu et al, 2009;To et al, 2016).…”