A mutant of Parainfluenza type 1 virus with decreased capacity for growth at 38 C and 39 C.

Abstract

Since the initial recovery of parainfluenza viruses from man 12-14 years ago, clinical and epidemiologic studies have established these agents as important pathogens of the respiratory tract in early life [1-5]. Inactivated monovalent or polyvalent vaccines have been prepared, but evidence of protective efficacy has not been obtained [6-10]. The recent finding that the level of virus-neutralizing antibody in nasal secretions was a better index of host resistance to infection with parainfluenza type 1 virus than was the level of serum antibody suggested that the development of live attenuated strains of virus suitable for nasopharyngeal administration might be a more effective approach to immunoprophylaxis [11, 12]. Adaptation of several myxoviruses to growth at low or suboptimal temperatures (25 C-26 C) has resulted in the emergence and selection of mutants that exhibit decreased virulence for man