• CMV-specific immune response post-Towne challenge: gB antibody, T-cell IFN-g ELISPOT, T-cell proliferation assays for IE1, pp65, and/or gB, cytokine and phenotypic flow cytometry responses to pp65, IE1, gB.
  

• Safety of Towne challenge in subjects who have previously been immunized with a trivalent pDNA CMV vaccine (VCL-CT02).
  

This is a Phase 1, single-center, open-label trial of the live, attenuated Towne CMV vaccine administered as a “challenge” to healthy, CMV-seronegative, adult subjects who previously received the CMV immunotherapeutic trivalent pDNA-based vaccine, VCL-CT02, given by intradermal or intramuscular routes as described in the following table; these subjects have been followed for 32 weeks.

Table 6.1 Subject Distribution Group Formulation Dosing Regimen (day) Dose per Injection(Administered to the deltoid region) Route of Administration Number of Subjects

1. VCL-CT02 0, 28, 56 1.0 mg Intramuscular (IM) 6
2. VCL-CT02 0, 28, 56 100 μg/injection × 2 injections Intradermal (ID) 11 Total 17

Up to 10 subjects from Groups 1 and 2 will be approached for enrollment in the current protocol. If a subject consents and meets all eligibility criteria, the subject will receive Towne (3000 pfu subcutaneously) between 9 and 15 months after the subject’s first dose of VCL-CT02. Safety will be monitored and Both antibody to CMV gB and T-cell responses to CMV antigens will be measured at specified intervals for 252 days post Towne challenge.