Complete Protection of Mice against Lethal Murine Cytomegalovirus Challenge by Immunization with DNA Vaccines Encoding Envelope Glycoprotein Complex III Antigens gH, gL and gO

Abstract

Human cytomegalovirus infects the majority of humanity which may lead to severe morbidity and mortality in newborns and immunocompromised adults. Humoral and cellular immunity are critical for controlling CMV infection. HCMV envelope glycoprotein complexes (gC I, II, III) represent major antigenic targets of antiviral immune responses. The gCIII complex is comprised of three glycoproteins, gH, gL, and gO. In the present study, DNA vaccines expressing the murine cytomegalovirus homologs of the gH, gL, and gO proteins were evaluated for protection against lethal MCMV infection in the mouse model. The results demonstrated that gH, gL, or gO single gene immunization could not yet offer good protection, whereas co-vaccination strategy apparently showed effects superior to separate immunization. Twice immunization with gH/gL/gO pDNAs could provide mice complete protection against lethal salivary gland-derived MCMV (SG-MCMV) challenge, while thrice immunization with pgH/pgL, pgH/pgO or pgL/pgO could not provide full protection. Co-vaccination with gH, gL and gO pDNAs elicited robust neutralizing antibody and cellular immune responses. Moreover, full protection was also achieved by simply passive immunization with anti-gH/gL/gO sera. These data demonstrated that gCIII complex antigens had fine immunogenicity and might be a promising candidate for the development of HCMV vaccines.

Importance of Highly Conserved Peptide Sites of Human Cytomegalovirus gO for Formation of the gH/gL/gO Complex

“…An essential role of the gH/gL/gO complex for pathogenesis of murine CMV (MCMV) was recently demonstrated in a mouse model: a gO-deficient MCMV mutant was unable to establish infection in mice (32), indicating that gO plays a pivotal role for host-to-host transmission of CMV. Immunization of mice with gH/gL/gO leads to full protection from otherwise lethal MCMV infection (33). For HCMV it was recently demonstrated that gH/gL/gO interacts with the cellular receptor platelet-derived growth factor receptor alpha (PDGFR-␣) (34).…”

Assessment of humoral immune response of a Cytomegalovirus DNA-vaccine candidate in BALB/c mice

“…Research in this area has focused on either attenuation of the live virus or the use of [8]. CMV is a large virus with a 230 kb double-stranded DNA genome coding for approximately 200 proteins of which UL55 (also known as glycoprotein B) has been recognized as a key immunogen eliciting strong immune responses in humans and a target for vaccine development [8,9]. Antibody production is considered a major defense against viruses and HCMV antiglycoprotein B (anti gB) is detected in all infected individuals.…”

“…Antibody production is considered a major defense against viruses and HCMV antiglycoprotein B (anti gB) is detected in all infected individuals. gB is a highly conserved, 906 amino-acid long protein consisting of an ectodomain, a hydrophobic region, a transmembrane and a cytoplasmic domain which is required for viral entry into all cell types including placental precursor cells and cell to cell spread of the virus [8][9][10]. Several antibodybinding sites have been identified on gB of which two domains containing three antigenic sites are capable of eliciting neutralizing antibodies during natural infection [9][10][11][12].…”

“…gB is a highly conserved, 906 amino-acid long protein consisting of an ectodomain, a hydrophobic region, a transmembrane and a cytoplasmic domain which is required for viral entry into all cell types including placental precursor cells and cell to cell spread of the virus [8][9][10]. Several antibodybinding sites have been identified on gB of which two domains containing three antigenic sites are capable of eliciting neutralizing antibodies during natural infection [9][10][11][12]. The gB region also contains several non-linear or assembled epitopes [9][10][11][12] and of the 5 antigenic domains identified on this protein, 4 have mapped to the first 693aa of the ectodomain, identifying the extracellular portion of HCMV gB as the immunodominant target for elicitation of neutralizing antibodies following natural infection [9][10][11][12].…”

“…Several antibodybinding sites have been identified on gB of which two domains containing three antigenic sites are capable of eliciting neutralizing antibodies during natural infection [9][10][11][12]. The gB region also contains several non-linear or assembled epitopes [9][10][11][12] and of the 5 antigenic domains identified on this protein, 4 have mapped to the first 693aa of the ectodomain, identifying the extracellular portion of HCMV gB as the immunodominant target for elicitation of neutralizing antibodies following natural infection [9][10][11][12]. In the present study the coding sequence for this fragment was synthesized and cloned as a DNA-based vaccine expressing truncated HCMV gB and its antigenicity was assessed in BALB/c mice.…”