Oral streptococci and cardiovascular disease: searching for the platelet aggregation-associated protein gene and mechanisms of Streptococcus sanguis-induced thrombosis.
BACKGROUND
Pathogenic mechanisms in infective endocarditis, disseminated intravascular coagulation, and cardiovascular events involve the aggregation of platelets into thrombi. Attendant infection by oral bacteria contributes to these diseases. We have been studying how certain oral streptococci induce platelet aggregation in vitro and in vivo. Streptococcus sanguis expresses a platelet aggregation-associated protein (PAAP), which contributes little to adhesion to platelets. When specific antibodies or peptides block PAAP, S. sanguis fails to induce platelet aggregation in vitro or in vivo.


METHODS
We used subtractive hybridization to identify the gene encoding for PAAP.


RESULTS
After subtraction of strain L50 (platelet aggregation-negative), four strain 133-79 specific sequences were characterized. Sequence agg4 encoded a putative collagen-binding protein (CbpA), which was predicted to contain two PAAP collagen-like octapeptide sequences. S. sanguis CbpA- mutants were constructed and tested for induction of platelet aggregation in vitro. Platelet aggregation was substantially inhibited when compared to the wild-type using platelet-rich plasma from the principal donor, but adhesion was unaffected. Other donor platelets responded normally to the CbpA- strain, suggesting additional mechanisms of response to S. sanguis. In contrast, CshA- and methionine sulfoxide reductase-negative (MsrA-) strains neither adhered nor induced platelet aggregation.


CONCLUSIONS
CbpA was suggested to contribute to site 2 interactions in our two-site model of platelet aggregation in response to S. sanguis. Platelet polymorphisms were suggested to contribute to the thrombogenic potential of S. sanguis.
Herzberg
Mark C
MC
Department of Oral Sciences, School of Dentistry and the Mucosal and Vaccine Research Center, University of Minnesota, Minneapolis, MN 55455, USA. mcherzb@umn.edu
Nobbs
Angela
A
Tao
Lin
L
Kilic
Ali
A
Beckman
Eric
E
Khammanivong
Ali
A
Zhang
Yongshu
Y
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D002318:Cardiovascular Diseases / Q000382:microbiology*; D004697:Endocarditis, Bacterial / Q000382:microbiology; D005798:Genes, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010973:Platelet Adhesiveness / Q000235:genetics; D010974:Platelet Aggregation / Q000235:genetics; D011110:Polymorphism, Genetic; D013298:Streptococcus sanguis / Q000235:genetics* / Q000472:pathogenicity*; D013927:Thrombosis / Q000382:microbiology*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C490083:CbpA protein, bacteria; C111210:platelet aggregation-associated protein, Streptococcus