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A live guinea pig cytomegalovirus vaccine deleted of three putative immune evasion genes is highly attenuated but remains immunogenic in a vaccine/challenge model of congenital cytomegalovirus infection.

ABSTRACT: Live attenuated vaccines for prevention of congenital cytomegalovirus infections encode numerous immune evasion genes. Their removal could potentially improve vaccine safety and efficacy. To test this hypothesis, three genes encoding MHC class I homologs (presumed NK evasins) were deleted from the guinea pig cytomegalovirus genome and the resulting virus, 3DX, was evaluated as a live attenuated vaccine in the guinea pig congenital infection model. 3DX was attenuated in vivo but not in vitro. Vaccination with 3DX produced elevated cytokine levels and higher antibody titers than wild type (WT) virus while avidity and neutralizing titers were similar. Protection, assessed by maternal viral loads and pup mortality following pathogenic viral challenge during pregnancy, was comparable between 3DX and WT and significant compared to naïve animals. These results suggest that the safety and perhaps efficacy of live attenuated human cytomegalovirus vaccines could be enhanced by deletion of viral immunomodulatory genes.

SUBMITTER: Crumpler MM

PROVIDER: S-EPMC3539795 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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A live guinea pig cytomegalovirus vaccine deleted of three putative immune evasion genes is highly attenuated but remains immunogenic in a vaccine/challenge model of congenital cytomegalovirus infection.

Crumpler Megan M MM Choi K Yeon KY McVoy Michael A MA Schleiss Mark R MR

Vaccine 20090503 31

Live attenuated vaccines for prevention of congenital cytomegalovirus infections encode numerous immune evasion genes. Their removal could potentially improve vaccine safety and efficacy. To test this hypothesis, three genes encoding MHC class I homologs (presumed NK evasins) were deleted from the guinea pig cytomegalovirus genome and the resulting virus, 3DX, was evaluated as a live attenuated vaccine in the guinea pig congenital infection model. 3DX was attenuated in vivo but not in vitro. Vac ...[more]

PMID: 19389443

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Project description:AimsCongenital human cytomegalovirus (HCMV) infection can lead to long-term neurodevelopmental sequelae, including mental retardation and sensorineural hearing loss. Preconception vaccine strategies relevant to prevention of HCMV-mediated injury to the newborn can be studied in the guinea pig cytomegalovirus (GPCMV) model. The objectives of this study were: 1) to assess in guinea pigs the protective efficacy against congenital infection and disease of a recombinant live, attenuated vaccine with a targeted deletion of the GPCMV homolog of the HCMV pUL83 tegument protein, GP83; and, 2) to compare the extent of placental infection in vaccine and control groups, using an in situ hybridization (ISH) assay.Materials and methodsOutbred Hartley guinea pigs were vaccinated prior to pregnancy with a two-dose series of 5×104 pfu of vAM409, a GP83 deletion virus. Deletion of the GP83 gene resulted in an attenuated virus, and vAM409 vaccinated animals did not demonstrate evidence of DNAemia following vaccination, although ELISA antibody responses were comparable to those observed in natural infection. After mating, pregnant animals were challenged with salivary gland-adapted (SG) GPCMV (1×106 pfu) in the second trimester, and pregnancy outcomes were compared to controls.ResultsCompared to placebo-immunized controls, vaccination resulted in significantly reduced maternal DNAemia following SG challenge, and there was significantly decreased pup mortality in litters born to vaccinated dams (3/29; 10%), compared to control (35/50; 70%; p<0.001). By in situ hybridization study, recovered placentas in the vAM409 vaccine group demonstrated reduced infection and fewer infectious foci compared to the control group.ConclusionsIn summary, preconception immunization with a GP83 deletion vaccine reduced maternal DNAemia and results in protection against congenital GPCMV-associated pup mortality compared to unvaccinated controls. Vaccination resulted in reduced placental infection, probably related to the reduction in maternal DNAemia. Although the pp65 homolog in GPCMV, GP83, is a known target of protective T cell immune responses, it is nevertheless dispensable for effective vaccination against maternal and fetal CMV disease in this model.

Project description:BackgroundCytomegalovirus (CMV) is a leading infectious cause of neurologic deficits, both in the settings of congenital and perinatal infection, but few animal models exist to study neurodevelopmental outcomes. This study examined the impact of neonatal guinea pig CMV (GPCMV) infection on spatial learning and memory in a Morris water maze (MWM) model.MethodsNewborn pups were challenged intraperitoneally (i.p.) with a pathogenic red fluorescent protein-tagged GPCMV, or sham inoculated. On days 15-19 post infection (p.i.), pups were tested in the MWM. Viral loads were measured in blood and tissue by quantitative PCR (qPCR), and brain samples collected at necropsy were examined by histology and immunohistochemistry.ResultsViremia (DNAemia) was detected at day 3 p.i. in 7/8 challenged animals. End-organ dissemination was observed, by qPCR, in the lung, liver, and spleen. CD4-positive (CD4+) and CD8-positive (CD8+) T cell infiltrates were present in brains of challenged animals, particularly in periventricular and hippocampal regions. Reactive gliosis and microglial nodules were observed. Statistically significant spatial learning and memory deficits were observed by MWM, particularly for total maze distance traveled (p < 0.0001).ConclusionNeonatal GPCMV infection in guinea pigs results in cognitive defects demonstrable by the MWM. This neonatal guinea pig challenge model can be exploited for studying antiviral interventions.ImpactCMV impairs neonatal neurocognition and memory in the setting of postnatal infection. The MWM can be used to examine memory and learning in a guinea pig model of neonatal CMV infection. CD4+ and CD8+ T cells infiltrate the brain following neonatal CMV challenge. This article demonstrates that the MWM can be used to evaluate memory and learning after neonatal GPCMV challenge. The guinea pig can be used to examine central nervous system pathology caused by neonatal CMV infection and this attribute may facilitate the study of vaccines and antivirals.

Dataset Information

A live guinea pig cytomegalovirus vaccine deleted of three putative immune evasion genes is highly attenuated but remains immunogenic in a vaccine/challenge model of congenital cytomegalovirus infection.

Publications

A live guinea pig cytomegalovirus vaccine deleted of three putative immune evasion genes is highly attenuated but remains immunogenic in a vaccine/challenge model of congenital cytomegalovirus infection.

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