[Molecular biological analysis of retinal and streptococcal heat-shock protein 60]

The observation of recurrent oral aphtha preceding ocular inflammation in patients with Behçet's disease suggests a role of oral Streptococcus in the etiology of this disease. Heat-treated Streptococcus antigen can induce ocular inflammation or systemic symptoms in Behçet's disease patients. Furthermore, the presence of an autoantibody against retinal heat-shock protein 60 (HSP 60) has been detected in the sera of these patients. Injection of extracted retinal HSP 60 also induces experimental uveitis in treated rats. The characteristics of retinal HSP 60 and HSP 60 from S. pyogenes were evaluated using a molecular biological approach.

The gene encoding HSP 60 was isolated by polymerase chain reaction (PCR) from a bovine retinal cDNA library and from S. pyogenes DNA. The DNA sequence of the HSP 60 coding region was determined, and the amino acid sequences of the encoded proteins were predicted from the DNA sequence. The synthetic peptide (50 nmol) was emulsified with Freund's complete adjuvant and injected into rats.

Comparison of the amino acid sequences of Streptococcal and bovine retinal HSP 60 revealed about 200 residue regions with 47% homology. Experimental uveitis was mainly induced in rats inoculated with retinal HSP 60-derived peptide or Streptococcus HSP 60-derived peptide that is equivalent to residues 245-259 of human HSP 65.

The retinal and Streptococcal HSP 60 amino acid composition is thought to be important and useful for investigating the mechanisms involved in the induction of Behçet's disease.