Downregulation of a protective Actinobacillus pleuropneumoniae antigen during the course of infection.
The persistence of Actinobacillus pleuropneumoniae in convalescent pigs significantly contributes to the distribution of disease. The downregulation of protective antigens in vivo as one possible mechanism responsible for this phenomenon was investigated using the small iron-regulated transferrin binding protein (TbpB-protein) as exemplary protective antigen. From a total of 21 pigs experimentally infected with A. pleuropneumoniae serotype 7 in three trials, bronchoalveolar lavage fluid (BALF) was obtained on day 1 or 2, day 7, day 14 and day 21. Employing double immunofluorescence of BALF with a monoclonal anti-TbpB antibody and an A. pleuropneumoniae -specific anti-polysaccharide antiserum a statistically significant decrease of the percentage of A. pleuropneumoniae bacteria strongly expressing TbpB protein was observed during the course of infection. These results were supported by in vitro incubation of A. pleuropneumoniae in medium supplemented with BALF. In addition, it was found that TbpB-expression in BALF from day 7 after infection could not be inhibited by the substitution of iron. These results suggest (i) the downregulation of protective antigens is one possible mechanism allowing bacterial persistence, (ii) in vitro induction in the presence of BALF mimics the in vivo situation, and (iii) TbpB expression is additionally regulated by an iron-independent mechanism.
Hennig
I
I
Tierärztliche Hochshule Hannover, Institut für Mikrobiologie und Tierseuchen, Bischofsholer Damm 15, Hannover, 30173, Germany.
Teutenberg-Riedel
B
B
Gerlach
G F
GF
D000189:Actinobacillus Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000276:immunology* / Q000472:pathogenicity; D000818:Animals; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D015153:Blotting, Western / Q000662:veterinary; D018893:Bronchoalveolar Lavage / Q000662:veterinary; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology*; D003720:Densitometry / Q000662:veterinary; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D005260:Female; D015200:Fluoroimmunoassay / Q000662:veterinary; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000032:analysis; D033862:Iron-Binding Proteins; D008168:Lung / Q000276:immunology; D008297:Male; D014066:Palatine Tonsil / Q000276:immunology; D011001:Pleuropneumonia / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D011897:Random Allocation; D011994:Recombinant Proteins / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000276:immunology* / Q000382:microbiology; D033863:Transferrin-Binding Proteins
D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D002352:Carrier Proteins; D033862:Iron-Binding Proteins; D011994:Recombinant Proteins; D033863:Transferrin-Binding Proteins; D007501:Iron