Connections between Exoproteome Heterogeneity and Virulence in the Oral Pathogen Aggregatibacter actinomycetemcomitans

Abstract

Periodontitis is one of the most common inflammatory diseases worldwide, causing high morbidity and decreasing the quality of life of millions of people. The bacterial pathogen Aggregatibacter actinomycetemcomitans is strongly associated with aggressive forms of periodontitis.

Differential Virulence of Aggregatibacter actinomycetemcomitans Serotypes Explained by Exoproteome Heterogeneity

“…A major aim of the present study was to compare the exoproteomes and virulence of serotype a, b, and c isolates of Aa . To this end, we screened a previously established collection of 27 clinical Aa isolates from which we had recently identified seven serotype b isolates ( 26 ). Further screening of the strain collection by serotype-specific PCR resulted in the identification of six Aa isolates with serotype a, 11 isolates with serotype c, and three isolates with serotype f (see Fig.…”

“…In addition, serotype b strains of Aa , especially those with the so-called JP2 genotype and cagE -positive isolates, can express more LtxA, which has been associated with enhanced virulence ( 23 , 24 ). In addition to LtxA, other virulence factors have been invoked in host infection and the evasion of host immune defenses ( 25 , 26 ). Most of these virulence factors are secreted into the extracellular milieu of the bacteria and, therefore, the bacterial “exoproteome” is considered the main reservoir of virulence factors ( 27 ).…”

“…In a previous study, we were able to differentiate Aa isolates and derivative strains with serotype b that showed either rough (R) or smooth (S) colony phenotypes by proteomics. Importantly, upon isolation from patients, Aa exclusively shows the R phenotype, whereas the S phenotype emerges spontaneously upon continued in vitro culturing due to mutations that affect the expression of fimbriae ( 26 , 28 ). It thus seems that proteomics studies on the overall secretion of virulence factors by R isolates of Aa may reflect the clinical presentation of Aa more realistically.…”

Coating and Corruption of Human Neutrophils by Bacterial Outer Membrane Vesicles

“…These observations raised the question of whether OMV exclusion by neutrophils is conserved among different P. gingivalis lineages and also whether this OMV exclusion can also be observed for other major oral pathogens that need to withstand the neutrophil. We therefore isolated OMVs from the major fimbriated oral pathogen A. actinomycetemcomitans (isolate 30R) ( 43 ) and incubated them with human neutrophils. Indeed, the A. actinomycetemcomitans OMVs effectively coated the neutrophil surface but without being internalized and without detectably affecting the neutrophil integrity ( Fig.…”

“…The clinical A. actinomycetemcomitans isolate 30R was grown on BHI agar plates supplemented with 5% l -cysteine, 5 mg/liter hemin, and 1 mg/liter menadione at 37°C and in 5% CO 2 ( 43 ). After 3 days, A. actinomycetemcomitans colonies were picked from BHI agar plates and cultured in BHI broth overnight until it reached a midexponential phase at an OD 600 of ~0.5.…”