MONOCLONAL-ANTIBODIES TO HUMAN PARAINFLUENZA VIRUS TYPE-1 DETECT MAJOR ANTIGENIC CHANGES IN CLINICAL ISOLATES

The extent of antigenic diversity within a population of human parainfluenza virus type 1 (HPIV-1) isolates collected over a 26-year period was investigated. Twenty-three monoclonal antibodies (MAbs) made to the hemagglutinin-neuraminidase protein (HN), fusion protein (F), phosphoprotein (P), and nucleoprotein (NP) of a 1957 type strain were compared in their ability to bind to the different clinical isolates in ELISA and hemagglutinin-inhibition (HI) assay. Four HN, one F, and two NP MAbs bound equally to all of the viruses tested, but six of the MAbs demonstrated significant antigenic heterogeneity. Most of these antigenic changes appeared stable over time and noncumulative. Four of the clinical isolates and the type virus had similar reactivity patterns (subtype A) to these MAbs, while the remaining 10 isolates may form a second group (subtype B). Children's sera demonstrated this same subtype specificity in HI assays. One neutralization site was present on the 1957 strain and not on any of the subsequent isolates. The possibility of two or more major subtypes of HPIV-1 should be considered in future epidemiologic, therapeutic, and vaccine-related work.