QUANTIFICATION OF MEASLES-VIRUS BY A VIRUS RECEPTOR-DEPENDENT AND HEMAGGLUTININ-SPECIFIC T-CELL STIMULATION ASSAY

The human measles virus receptor CD46 plays a major role in the uptake of measles virus (MV) for antigen presentation by major histocompatib ility complex class II molecules to T cells. On this basis, a new bioa ssay has been set up to quantify measles virus in a cell free tissue c ulture supernatant. A stable mouse B cell transfectant expressing CD46 was used as the antigen presenting cell for presentation of measles v irus to a haemagglutinin-specific and class II-restricted mouse T cell hybridoma. The measles virus haemagglutinin was quantified by its abi lity to stimulate IL-2 secretion by the T cells, A good correlation wa s found between the amount of haemagglutinin measured in supernatants from infected cells using the CD46-dependent T cell stimulation assay and the number of infectious viral particles as determined in a plaque assay. When MV was purified on a discontinuous sucrose gradient, most of the infectious virus and the haemagglutinin antigen were recovered in the same fraction. These data indicate that the CD46-dependent hae magglutinin-specific T cell assay could be used to measure the product ion of measles virus in the supernatant of infected cells. The assay r equired only 48 h, was sensitive, highly specific, and did not rely on the replication of the virus. This new bioassay would be applicable f or the detection of any other virus provided that antigen presenting c ells expressing the corresponding virus receptor and virus envelope gl ycoprotein-specific T cells are available. Moreover, it would be an in teresting tool to monitor the receptor binding properties of attenuate d vaccine virus and envelope glycoprotein subunit vaccines.