Neuraminidase production by streptococci from patients with glomerulonephritis

Autoantigenic events in acute poststreptococcal glomerulonephritis (APSGN) may result from neuraminidase-induced alterations in immunoglobulin levels. Whether streptococci from patients with APSGN produced neuraminidase and, if so, what substrates could be used for screening purposes and what were of potential clinical relevance were determined. Group A streptococci cultured from 20 patients with APSGN and four patients with acute rheumatic fever and group B, C, D, and G streptococci cultured from other individuals were reacted with the substrates to determine neuraminidase activity by the thiobarbituric acid assay. Neuraminidase production was detected in 16 of 20 streptococci from patients with APSGN. Partial purification by Sephadex G-150 chromatography gave two peaks, and polyacrylamide gel electrophoresis gave two bands with neuraminidase activity. Bovine mucin was the most useful substrate to detect neuraminidase production by nephritogenic streptococci, and with respect to human substrates, IgM was the most sensitive and renal basement membrane the least sensitive to enzyme action.