Characterization of the lipopolysaccharide O antigens of Actinobacillus pleuropneumoniae serotypes 9 and 11: antigenic relationships among serotypes 9, 11, and 1

Abstract

The antigenic lipopolysaccharide 0 polysaccharides of capsular serotypes 9 and 11 were examined by chemical, immunological, and nuclear magnetic resonance methods. Immunodiffusion tests carried out on these 0 antigens indicated that both contained common epitopes which were also shared by Actinobacilus peuropneumonae serotype 1. Chemical analysis and high-field nuclear magnetic resonance spectroscopy showed that the 0 antigens of serotypes 9 and 11 were high-molecular-weight polymers consisting of a backbone of repeating trisaccharide units composed of a-L-rhamnopyranosyl and a-D-glucopyranosyl residues (2:1). One of the c-L-rhamnose units forms a branch point and is stoichiometrically substituted with terminal 2-acetamido-2-deoxy-1-D-glucose residues in the serotype 11 0 polysaccharide, but only to the extent of 25% in the serotype 9 0 polysaccharide. Thus, the serotype 9 0 polysaccharide contains two different repeating units: a tetrasaccharide unit with the same structure as that of the serotype 11 0 polysaccharide and a trisaccharide unit:where R = j3-D-GlcpNAc for serotype 1 and 11 0 polysaccharides, and R = H (75%) and R = f-D-GlcPNAc (25%o) for serotype 9. The structure of the previously determined serotype 1 0 polysaccharide (E. Altman, J.-R Brisson, and M. B. Perry, Biochem. Cell. Biol. 64:17-25, 1986) is identical to that of the serotype 11 0 polysaccharide. We propose a more complete serotyping scheme for A. pleuropneumoniae which includes designation of both the capsular (K) and 0 antigens. Actinobacillus pleuropneumoniae is a gram-negative, pleomorphic rod which causes a highly contagious disease in pigs. The occurrence of A. pleuropneumoniae-associated pleuropneumonia has increased since 1976 (29) because of intensified pig production, and A. pleuropneumoniae lipopolysaccharide (LPS) is recognized as an important virulence factor (30). In attempts to combat the disease, serological methods of identification of infected animals based on the identification and characterization of serotype-specific antigens would greatly assist in solving the problem. Information on the structures of the LPS 0 antigens of A. pleuropneumoniae involved as virulence factors, in protection, and in serodiagnosis could provide data leading to the rational development of suitable, protective vaccines and the production of specific serotyping and serodiagnostic reagents.Currently, 12 serotypes ofA. pleuropneumoniae based on capsular polysaccharides (CPS) are recognized (26). Capsular serotypes 1, 5, and 7 are the predominant disease isolates from A. pleuropneumoniae outbreaks in the United States and Canada (28), whereas serotype 9 is predominant in The Netherlands (19). Serological cross-reactivity between A. pleuropneumoniae serotypes 1 and 9 has been detected by * Corresponding author. t NRCC no. 34260. complement fixation and gel diffusion methods (25). This cross-reactivity was attributed to common polysaccharide antigens by Mittal (24), who also concluded that these serotypes do not share CPS epitopes but that the cross...

fhuAofActinobacillus pleuropneumoniaeEncodes a Ferrichrome Receptor but Is Not Regulated by Iron

“…The three main branches of the dendrogram are serotypes 1, 9, 11, 3, and 8; serotypes 6, 2, 4, 7, and 5; and serotypes 10 and 12. Interestingly, this relatedness may be correlated, to some extent, with the serological cross-reactivity (3). Taken together, these data could be extrapolated to interpret the common ancestry of different A. pleuropneumoniae serotypes and show their evolution as how they diversified over time.…”

Chromosome sizes and phylogenetic relationships between serotypes of Actinobacillus pleuropneumoniae

“…However, cross-reactivity, between A. pleuropneumoniae serotypes 1, 9 and 11, between serotypes 3, 6 and 8, and between serotypes 4 and 7 has been described [12]. These cross-reactions were shown to be associated with common epitopes and common components of the cell wall antigens [12,13].…”

AtypicalActinobacillus PleuropneumoniaeIsolates That Share Antigenic Determinants with Both Serotypes 1 and 7

“…5 This pathogen is among the most important nosocomial infections in humans 28 and is the most diagnosed cause of antibiotic-associated colitis. 2,18 Outbreaks of C. difficile-associated disease are not uncommonly reported in human hospital wards, and caused ward closures in 16% of British hospitals in 1996. 34 Clostridium difficile has also been implicated in an outbreak of colitis among horses at a veterinary teaching hospital.…”

“…Clostridium difficile is a gram-positive anaerobic bacterium that is an important cause of diarrhea in humans, 2,22,25 and a commonly identified nosocomial pathogen in human hospitals. [26][27][28]31 Other than hamsters and guinea pigs, the exact role of this pathogen in domestic animals is less clear, although increasingly it is associated with enterocolitis in horses.…”

“…5 Because these isolates possessed serotype 1 CPS-related epitopes, they were easily captured by beads coated with antibodies raised against whole-cell antigen in rabbits; in fact, these antibodies have been shown to be directed to both capsular and somatic epitopes. 15 Based on the proposed new nomenclature, 2,19 isolates 1B and 27E could antigenically be designated as K1:O7, whereas isolate 26B would be considered as K1:O7/4. Diagnostic laboratories that use LC-LPS-based ELISA may diagnose herds infected with these isolates as being infected by A. pleuropneumoniae serotype 7, whereas those that use CPS-based ELISA will probably consider them as being infected by A. pleuropneumoniae serotype 1.…”