Safety and immunogenicity of the Towne strain cytomegalovirus vaccine

Background. Women with naturally acquired serum antibodies to cytomegalovirus (CMV) are usually protected against both frequent secondary infection and giving birth to infants severely affected by intrauterine CMV infection. Objective. To determine the feasibility of using a live attenuated strain of CMV (Towne) to achieve immunity similar to that provided by wild-type infection, we evaluated a new lot of the Towne strain of CMV in 3 open label trials involving 68 men, 63 women of childbearing age and 13 children, respectively. Results. Mild local reactions occurred among approximately one-third of subjects. There were no systemic reactions. All 45 subjects tested developed lymphoproliferative responses to CMV. CD8(+) class I-restricted cytotoxic T cell responses specific for CMV antigens were detected in three of four subjects and persisted for 6 months. Neutralizing titers were maximal at 2 to 4 months postimmunization, were dose-dependent and were comparable to those induced by natural infection. Conclusion. These results support further evaluation of the Towne strain of CMV in women at risk for acquiring CMV infection during pregnancy or among children transmitting CMV to pregnant women.