title: Vaccination with a Live Attenuated Cytomegalovirus Devoid of a Protein Kinase R Inhibitory Gene Results in Reduced Maternal Viremia and Improved Pregnancy Outcome in a Guinea Pig Congenital Infection Model.
abstract: Development of a vaccine to prevent congenital cytomegalovirus infection is a major public health priority. Live vaccines attenuated through mutations targeting viral mechanisms responsible for evasion of host defense may be both safe and efficacious. Safety and vaccine efficacy were evaluated using a guinea pig cytomegalovirus (GPCMV) model. Recombinant GPCMV with a targeted deletion of gp145 (designated Δ145), a viral protein kinase R (PKR) inhibitor, was generated. Attenuation was evaluated following inoculation of 10(7) PFU of Δ145 or parental virus into guinea pigs immunosuppressed with cyclophosphamide. Efficacy was evaluated by immunizing GPCMV-naive guinea pigs twice with either 10(5) or 10(6) PFU of Δ145, establishing pregnancy, and challenging the guinea pigs with salivary gland-adapted GPCMV. The immune response, maternal viral load, pup mortality, and congenital infection rates in the vaccine and control groups were compared. Δ145 was substantially attenuated for replication in immunocompromised guinea pigs. Vaccination with Δ145 induced enzyme-linked immunosorbent assay (ELISA) and neutralizing antibody levels comparable to those achieved in natural infection. In the higher- and lower-dose vaccine groups, pup mortality was reduced to 1/24 (4%) and 4/29 (14%) pups, respectively, whereas it was 26/31 (81%) in unvaccinated control pups (P < 0.0001 for both groups versus the control group). Congenital infection occurred in 20/31 (65%) control pups but only 8/24 (33%) pups in the group vaccinated with 10(6) PFU (P < 0.05). Significant reductions in the magnitude of maternal DNAemia and pup viral load were noted in the vaccine groups compared to those in the controls. Deletion of a GPCMV genome-encoded PKR inhibitor results in a highly attenuated virus that is immunogenic and protective as a vaccine against transplacental infection.
  
  
  OBJECTIVE
  Previous attempts to develop successful immunization against cytomegalovirus have largely centered on subunit vaccination against virion proteins but have yielded disappointing results. The advent of bacterial artificial chromosome technologies has enabled engineering of recombinant cytomegaloviruses (CMVs) from which virus genome-encoded immune modulation genes have been deleted, toward the goal of developing a safe and potentially more efficacious live attenuated vaccine. Here we report the findings of studies of such a vaccine against congenital CMV infection based on a virus with a targeted deletion in gp145, a virus genome-encoded inhibitor of protein kinase R, using the guinea pig model of vertical CMV transmission. The deletion virus was attenuated for dissemination in immunocompromised guinea pigs but elicited ELISA and neutralizing responses. The vaccine conferred protection against maternal DNAemia and congenital transmission and resulted in reduced viral loads in newborn guinea pigs. These results provide support for future studies of attenuated CMV vaccines.
authors.affiliation: Center for Infectious Diseases and Microbiology Translational Research, Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA schleiss@umn.edu.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Schleiss
authors.affiliation: Center for Infectious Diseases and Microbiology Translational Research, Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Bierle
authors.affiliation: Center for Infectious Diseases and Microbiology Translational Research, Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Swanson
authors.affiliation: Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McVoy
authors.affiliation: Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
authors.forename: Jian Ben
authors.initials: JB
authors.lastname: Wang
authors.affiliation: Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
authors.forename: Zainab
authors.initials: Z
authors.lastname: Al-Mahdi
authors.affiliation: Fred Hutchison Cancer Research Center and the University of Washington, Seattle, Washington, USA.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Geballe
mesh_terms: D000818:Animals; D003587:Cytomegalovirus / Q000235:genetics* / Q000276:immunology*; D003586:Cytomegalovirus Infections / Q000151:congenital / Q000517:prevention & control*; D005260:Female; D006168:Guinea Pigs; D011247:Pregnancy; D011256:Pregnancy Outcome; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency*; D014611:Vaccination / Q000379:methods*; D014613:Vaccines, Attenuated / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*; D014766:Viremia
chemical_list: D014613:Vaccines, Attenuated; D014765:Viral Vaccines; D017346:Protein Serine-Threonine Kinases