Development of a Rhesus Cytomegalovirus gH/gL Subunit Vaccine Based on Markerless Manipulation of a Cloned Poxvirus Genome
- Felix Wussow, Post-Doctoral Fellow, Division of Translational Vaccine Research, Department of Virology, Beckman Research Institute of the City of Hope
- Flavia Chiuppesi, Post-Doctoral Fellow, Division of Translational Vaccine Research, Department of Virology, Beckman Research Institute of the City of Hope
- Don Diamond, Director, Division of Translational Vaccine Research, Department of Virology, Beckman Research Institute of the City of Hope
Human cytomegalovirus (HCMV) is a major public health problem because it causes developmental disabilities in newborns and multi-organ failure in immunocompromised individuals. Neutralizing antibodies (NAb) that prevent HCMV entry into host cells are hypothesized as an important host response against HCMV. Recently it has been discovered that HCMV entry occurs by two different pathways; one mediates HCMV entry into fibroblasts, and the other virus entry into epithelial and endothelial cells (Epi/EC). In contrast to other major envelope glycoprotein complexes, the gH/gL heterodimer is required for both virus entry routes. Several studies provide evidence that NAb to gH/gL prevent HCMV infection of Epi/EC and fibroblasts. These observations indicate that gH/gL could be an important vaccine target to induce NAb against HCMV. Rhesus Cytomegalovirus (RhCMV) is closely related to HCMV and serves as a vaccine efficacy model because it is infectious in Rhesus macaques (RM). We constructed a vaccine vector based on the attenuated poxvirus Modified Vaccinia Ankara virus (MVA) that co-expressed the RhCMV equivalents of HCMV envelope glycoproteins gH/gL (RhgH/RhgL). Using two-step markerless Red recombination, expression cassettes for RhgH and RhgL were consecutively inserted into an MVA genome cloned as a bacterial artificial chromosome (BAC). BAC integrity was confirmed by PCR, restriction pattern, and sequencing. Following virus reconstitution from the BAC DNA in MVA-permissive baby hamster kidney (BHK) cells, expression of the two RhCMV genes from MVA was confirmed by immunoblot. This vaccine will be tested in RhCMV-negative RM for NAb production and protection against challenge with a virulent RhCMV strain. This vaccine offers a novel strategy to prevent or control HCMV infection.