Isolation and characterization of monoclonal antibodies to human parainfluenza virus type 4 and their use in revealing antigenic relation between subtypes 4A and 4B.

Eighty monoclonal antibodies (MAbs) against parainfluenza virus type 4(PIV-4) were isolated and characterized. Of 50 MAbs against PIV-4A, 14 reacted with the nucleocapsid (NP) protein, 11 with the hemagglutinin-neuraminidase (HN) glycoprotein, 6 with the fusion (F) glycoprotein, and 19 with the matrix (M) protein. With the aid of the PIV-4A and PIV-2 specific MAbs showing cross-reactivity with PIV-4B, the structural proteins of PIV-4B were identified. gp72, p65, gp65, gp55, p53, and p40 of PIV-4B were assigned to HN, NP, Fo, F1, P, and M proteins, respectively. Based on the results, specificities of the MAbs against PIV-4B were determined. Of 30 hybridoma clones against PIV-4B, 13 clones were found to produce antibodies against the NP protein, 7 against the HN protein, and 10 against the F protein. Epitope mapping of these MAbs was performed with competitive binding assays in ELISA. According to their biological activities, the MAbs against the HN protein of either PIV-4A or 4B could be divided into three groups. The first group showed high hemagglutination inhibition (HI), hemolysis inhibition (HLI), and neutralizing (NT) activities. The second group showed high NT activity, but could not block hemagglutination. The final group showed a lower level of all activities. The MAbs against the F protein of PIV-4A and against PIV-4B were divided into two groups. Some MAbs against the F protein had high titer of NT, suggesting that the F protein had neutralizing-related epitopes. Antigenicity of the NP protein was highly conserved among subtypes of PIV-4. On the other hand, the MAbs against the HN and the F proteins showed high reactivity with the homologous subtype viruses, but low reactivity with the heterologous subtype viruses, indicating that the external glycoproteins exhibited antigenic variations between two subtypes of PIV-4. When the immunological interrelationship among various paramyxoviruses was analyzed. PIV-4 was found to be antigenically related to PIV-2, SV 5, and mumps virus.