Vaccination of human volunteers against Russian spring-summer (RSS) virus complex with attenuated Langat E5 virus

Attenuated Langat E5 virus grown in germ-free chick embryos has 6 markers to differentiate it from the parent virulent virus. It is stable after passage in various laboratory animals and tissue cultures. When injected into human volunteers it leads to the development of significant levels of homologous and heterologous neutralizing antibody against certain members of the Russian spring-summer virus complex. These antibodies persist at a high level for at least 2 years. Furthermore, no complications have been demonstrated by repeated clinical examinations, electroencephalograms, electrocardiograms, chest X-rays, and examinations of blood and urine. Attenuated Langat E5 virus has potential value for live virus vaccine for the protection against human illness caused by the members of the Russian spring-summer virus complex.