Genome-wide screening of lipoproteins in Actinobacillus pleuropneumoniae identifies three antigens that confer protection against virulent challenge

Abstract

Actinobacillus pleuropneumoniae is an important veterinary pathogen that causes porcine pleuropneumonia. Lipoproteins of bacterial pathogens play pleiotropic roles in the infection process. In addition, many bacterial lipoproteins are antigenic and immunoprotective. Therefore, characterization of lipoproteins is a promising strategy for identification of novel vaccine candidates or diagnostic markers. We cloned 58 lipoproteins from A. pleuropneumoniae JL03 (serovar 3) and expressed them in Escherichia coli. Five proteins with strong positive signals in western blotting analysis were used to immunize mice. These proteins elicited significant antibody responses, and three of them (APJL_0922, APJL_1380 and APJL_1976) generated efficient immunoprotection in mice against lethal heterologous challenge with A. pleuropneumoniae 4074 (serovar 1), both in the active and passive immunization assays. Then immunogenicity of these three lipoproteins (APJL_0922, APJL_1380 and APJL_1976) were further tested in pigs. Results showed that these proteins elicited considerable humoral immune responses and effective protective immunity against virulent A. pleuropneumoniae challenge. Our findings suggest that these three novel lipoproteins could be potential subunit vaccine candidates.Actinobacillus pleuropneumoniae is a Gram-negative bacterium that colonizes the upper respiratory tract of pigs, and causes porcine pleuropneumonia, a common respiratory infection that is characterized as acute hemorrhagic to chronic necrotic-fibrinous pleuropneumonia and associated with significant economic losses in the pig industry worldwide 1 . Great efforts have been devoted to the characterization and control of porcine pleuropneumonia in the past 30 years, and considerable achievements have been made. A total of 18 serovars of A. pleuropneumoniae have been identified till now, all of these serovars are able to colonize pigs 2 . Since A. pleuropneumoniae is susceptible to drying and other antibacterial factors, direct transmission from infected to susceptible healthy pigs is considered to be the most frequent means by which the disease spreads 3 . Airborne transmission of A. pleuropneumoniae was also confirmed to occur over a short distance (1 m) 4 . Pigs of all ages are susceptible to A. pleuropneumoniae infection, especially fattening pigs at about 3-months old, and the first outbreak in herds often leads to high morbidity and mortality 5 . A. pleuropneumoniae contains several virulence factors, which are involved in the steps of adherence, colonization and tissue damage during infection, including Apx toxins, LPS, CPS, adhesins, outer membrane proteins, and transcriptional regulators 6 .Treatment of bacterial diseases of food-producing animals by extensive use of antimicrobial agents leads to antimicrobial resistance (AMR), a serious consequence that has attracted growing concerns worldwide 7 . The problem of AMR in A. pleuropneumoniae should not be underestimated at present 8 , and the use of drugs is undesirable for consumers of ethically produ...

Development of a novel high resolution melting assay for identification and differentiation of all known 19 serovars of Actinobacillus pleuropneumoniae

“…Referring to the severity of symptoms caused by A. pleuropneumoniae and based on the assumption of a high A. pleuropneumoniae prevalence (>0.3), Stygar and coworkers calculated the additional yearly costs between €0.4 and 24 per space unit (Stygar et al, 2016 ). Due to the challenges of antibiotic usage and the generation of antibiotic resistance, the most promising approach to preventing A. pleuropneumoniae infection lies in vaccination (Cao et al, 2020 ; Michael et al, 2015 ). Current market‐leading vaccines are based on inactivated Apx toxins and outer membrane components of A. pleuropneumoniae or inactivated A. pleuropneumoniae of selected serovars (Del Pozo Sacristán et al, 2014 ; Sipos et al, 2021 ).…”

Involvement of the Actinobacillus pleuropneumoniae ompW Gene in Confrontation of Environmental Pressure

“…A. pleuropneumoniae is considered one of the most important bacterial respiratory pathogens of pigs with epidemic disease resulting in serious economic loss ( 36 ). There are many studies on the infection mechanism and the resistance to environmental pressure of A. pleuropneumoniae , but there are still many unknowns to be researched.…”

Immune Response to the Dual Antigen Vaccine of Actinobacillus pleuropneumoniae in a Mouse Model

“…Because a single protein may lack epitopes suitable for universal immune recognition, it cannot be used against all serotypes of A. pleuropneumoniae. Multiple antigens induce stronger immune responses than those triggered by a single component [14]. This is our strategy immunization with subunit vaccines combined with individual potential structural and functional proteins from the same target would be predicted to trigger the development of a strong host protective immune response.…”