Biomedical subjects

Zhaoti Wang

Publications and source records attributed to Zhaoti Wang.

5 recordsLinked to original sources

PubMed2006

A phase 1 study of 4 live, recombinant human cytomegalovirus Towne/Toledo chimeric vaccines.

BACKGROUND: Human cytomegalovirus (HCMV) infection acquired in utero often results in severe consequences, including mental retardation and deafness. Although not evaluated for this indication, live attenuated HCMV vaccines based on the Towne strain are well-tolerated and have demonstrated moderate efficacy in other clinical settings. METHODS: To produce live HCMV vaccine candidates that retain the excellent safety profile of the Towne strain but are more immunogenic, the genomes of the Towne strain and the unattenuated HCMV Toledo strain were recombined to yield 4 independent chimeric vaccine candidates. These vaccine candidates were evaluated in 20 HCMV-seropositive persons, in a phase 1, double-blinded, placebo-controlled trial. Participants received a single dose of vaccine or placebo, and the safety and tolerability of the vaccine candidates were evaluated. RESULTS: There was no difference in systemic symptoms between the vaccine and placebo recipients. As a group, vaccine recipients experienced more injection-site reactions than did placebo recipients; however, these were generally minor and short-lived. Vaccine virus could not be detected in blood, urine, or saliva samples obtained from any vaccine recipient. CONCLUSIONS: The Towne/Toledo chimeric vaccine candidates were well tolerated and did not cause systemic infection. Additional human trials are warranted to further evaluate the potential of these vaccine candidates as live virus vaccines.

Adult↗

PubMed2005

Human cytomegalovirus uracil DNA glycosylase associates with ppUL44 and accelerates the accumulation of viral DNA.

BACKGROUND: Human cytomegalovirus UL114 encodes a uracil-DNA glycosylase homolog that is highly conserved in all characterized herpesviruses that infect mammals. Previous studies demonstrated that the deletion of this nonessential gene delays significantly the onset of viral DNA synthesis and results in a prolonged replication cycle. The gene product, pUL114, also appears to be important in late phase DNA synthesis presumably by introducing single stranded breaks. RESULTS: A series of experiments was performed to formally assign the observed phenotype to pUL114 and to characterize the function of the protein in viral replication. A cell line expressing pUL114 complemented the observed phenotype of a UL114 deletion virus in trans, confirming that the observed defects were the result of a deficiency in this gene product. Stocks of recombinant viruses without elevated levels of uracil were produced in the complementing cells; however they retained the phenotype of poor growth in normal fibroblasts suggesting that poor replication was unrelated to uracil content of input genomes. Recombinant viruses expressing epitope tagged versions of this gene demonstrated that pUL114 was expressed at early times and that it localized to viral replication compartments. This protein also coprecipitated with the DNA polymerase processivity factor, ppUL44 suggesting that these proteins associate in infected cells. This apparent interaction did not appear to require other viral proteins since ppUL44 could recruit pUL114 to the nucleus in uninfected cells. An analysis of DNA replication kinetics revealed that the initial rate of DNA synthesis and the accumulation of progeny viral genomes were significantly reduced compared to the parent virus. CONCLUSION: These data suggest that pUL114 associates with ppUL44 and that it functions as part of the viral DNA replication complex to increase the efficiency of both early and late phase viral DNA synthesis.

Cells, Cultured↗

PubMed2004

Development of an efficient fluorescence-based microneutralization assay using recombinant human cytomegalovirus strains expressing green fluorescent protein.

MedImmune Vaccines has created four, live, attenuated human cytomegalovirus (HCMV) vaccine candidates, each derived from defined portions of the parental strains, Towne and Toledo. To determine each candidate's ability to induce HCMV specific immunity, a fluorescence-based microneutralization assay was developed using recombinants of Toledo and Towne which express enhanced green fluorescent protein (EGFP). Replication of the EGFP recombinants in cell culture was the same as the respective parental strains. Using the EGFP recombinants, this fluorescence-based microneutralization assay was compared with the traditional plaque reduction assay. Serum samples were analyzed by both the fluorescence microneutralization and plaque reduction assays and regression analysis showed a correlation of R2 > or = 0.90 between the two assays. As an alternative to measuring fluorescence, infected cells were examined microscopically and the number of green fluorescent cells was counted automatically. Regression lines between fluorescent cell counting and fluorescence in the well also showed a high correlation (R2 > or = 0.92). An excellent linear concordance in titers was observed between the two assays. Using the plaque reduction assay, serum samples were identified that preferentially neutralized the Toledo strain compared to the Towne strain. The same preferences were observed with the fluorescence-based microneutralization assay. This new assay is adaptable to rapid, automated collection of neutralization data and would therefore be suitable for the examination of large numbers of clinical serum samples.

Cell Line↗

PubMed2004

Antiviral CD8 T cells in the control of primary human cytomegalovirus infection in early childhood.

Human cytomegalovirus (CMV) establishes persistent infection, with control of replication thought to be mediated by CMV-specific CD8 T cells. Primary CMV infection commonly affects young children and causes prolonged viral shedding in saliva and urine. We investigated whether this virus-host interaction pattern reflects a developmental deficiency of antiviral CD8 T cell-mediated immunity during childhood. CMV-specific CD8 T cell responses in asymptomatic children with active infection were not different from adults with recent or long-term infection in frequency and functional analyses. High urine CMV concentrations were detected, despite these CMV-specific CD8 T cell responses. We conclude that delayed resolution of primary CMV infection in young children is not caused by a deficient CMV-specific CD8 T cell response. Because these healthy children continue to have local CMV replication, we suggest that CD8 T cells may function primarily to prevent symptomatic, disseminated disease.

Adult↗

PubMed2004

Persistent and selective deficiency of CD4+ T cell immunity to cytomegalovirus in immunocompetent young children.

Healthy young children who acquire CMV have prolonged viral shedding into the urine and saliva, but whether this is attributable to limitations in viral-specific immune responses has not been explored. In this study, we found that otherwise immunocompetent young children after recent primary CMV infection accumulated markedly fewer CMV-specific CD4(+) T cells that produced IFN-gamma than did adults. These differences in CD4(+) T cell function persisted for more than 1 year after viral acquisition, and did not apply to CMV-specific IFN-gamma production by CD8(+) T cells. The IFN-gamma-producing CD4(+) T cells of children or adults that were reactive with CMV Ags were mainly the CCR7(low) cell subset of memory (CD45R0(high)CD45RA(low)) cells. The decreased IFN-gamma response to CMV in children was selective, because their CCR7(low) memory CD4(+) T cells and those of adults produced similar levels of this cytokine after stimulation with staphylococcal enterotoxin B superantigen. CD4(+) T cells from children also had reduced CMV-specific IL-2 and CD154 (CD40 ligand) expression, suggesting an early blockade in the differentiation of viral-specific CD4(+) T cells. Following CMV acquisition, children, but not adults, persistently shed virus in urine, and this was observable for at least 29 mo postinfection. Thus, CD4(+) T cell-mediated immunity to CMV in humans is generated in an age-dependent manner, and may have a substantial role in controlling renal viral replication and urinary shedding.

Adult↗