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Amino acid change 335 E to K affects the sialic-acid-binding and neuraminidase activities of Urabe AM9 mumps virus hemagglutinin-neuraminidase glycoprotein.

Reyes-Leyva J, Baños R, Borraz-Argüello M, Santos-López G, Rosas N, Alvarado G, Herrera I, Vallejo V, Tapia-Ramírez J

Laboratorio de Virología y Biología Molecular, Centro de Investigación Biomédica de Oriente, Instituto Mexicano del Seguro Social; Hospital General de Zona No. 5, Km. 4.5, Carretera Atlixco-Metepec, 74360 Metepec, Puebla, Mexico.

A mutation coding for the amino acid change E(335) to K is frequently found in the hemagglutinin-neuraminidase (HN) gene of Urabe AM9 mumps viruses isolated during post-vaccination meningitis cases. To identify if this mutation modifies the biological activities of the HN glycoprotein, two variants of Urabe AM9 vaccine differing at amino acid 335 (HN-E(335) and HN-K(335)) were isolated and their receptor-binding specificity was determined by means of competence assays. Pre-incubation of the viruses with sialic acids inhibited both syncytia formation in Vero cells and replication in SH-SY5Y cells. Thus, HN-K(335) showed higher affinity towards sialylalpha2,6lactose, whereas HN-G(335) preferred sialylalpha2,3lactose. These results are relevant because a high expression of sialylalpha2,6lactose in nerve cells was confirmed by means of Sambucus nigra lectin-cytochemistry. In addition, kinetics assays showed that HN-K(335) and HN-E(335) also differ in their hydrolysis rate (V(max) values of 37.5 vs. 3.5nmolmin(-1)mg(-1), respectively). Therefore, HN-K(335) variant presented a neuraminidase activity level 11-fold higher than that of HN-E(335) variant. In conclusion, the mutation affects the receptor-binding and neuraminidase activities of Urabe AM9 mumps virus variants.

Published 16 February 2007 in Microbes Infect, 9(2): 234-40.
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