Extracellular neuraminidase production of streptococci associated with acute nephritis

The possibility that streptococcal neuraminidase has a pathogenic role in acute poststreptococcal glomerulonephritis is reviewed. Experimental and clinical evidence suggesting autologous immune phenomena and anti-Ig reactivity in this disease is discussed. Neuraminidase may also induce sialic acid depletion that would be expected to result in changes of the electrical charge in the immune complex as well as in the glomerular polyanion filtration barrier. The nature of these changes will facilitate penetrability of material with nephritogenic potential. Neuraminidase production was detected in the majority of streptococcal isolates obtained from patients with glomerulonephritis and the best substrate for screening purposes appears to be bovine submaxillary gland mucin. On the basis of available evidence, it is suggested that the development of glomerulonephritis after streptococcal infection probably does not depend on neuraminidase production by the bacteria; however, this enzyme may be responsible for the anti-Ig reactivity demonstrated in some patients and thereby influence the course of the disease.