Radioactively-labelled VSV, both Indiana and New Jersey serotypes, were rapidly and efficiently adsorbed onto goose erythrocytes, but only within a narrow range of pH and at low temperatures. Under optimal conditions for adsorption, both infectivity and haemagglutinating activity of VSV were reduced. A basic difference between the two serotypes was identified: adsorption and haemagglutination of the Indiana serotype were stable even at pH 9.0 and at 37° C, whereas New Jersey serotype was eluted slowly at +0° C and at pH 6.4 and rapidly at a higher temperature and pH. The rapid elution offers a useful method for purification of New Jersey serotype.
Particle counting of VSV showed that 10 to 50 virus particles were required for one PFU. Haemagglutination was not a sensitive method for assaying small amounts of VSV; 3–20 × 107 virus particles or more than 107 PFU corresponded to one HAU.