Polymorphisms in Human Cytomegalovirus Glycoprotein O (gO) Exert Epistatic Influences on Cell-Free and Cell-to-Cell Spread and Antibody Neutralization on gH Epitopes

Day, Le Zhang; Stegmann, Cora; Schultz, Eric P.; Lanchy, Jean-Marc; Yu, Qin; Ryckman, Brent J.

doi:10.1128/jvi.02051-19

Cited by 26 publications

(39 citation statements)

References 66 publications

(173 reference statements)

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“…This last results is in contrast with a previous report from the literature where the TB40-UL148-null virus increases replication in epithelial cells (19). As it was pointed out in a very recent and elegant report, we suppose that this difference may be due to the genetic background of different strains (33). As first, we speculated that the gH/UL116 dimer could recognize a receptor on target cells surface and we purified the complex and checked binding by FACS.…”

Section: Discussioncontrasting

confidence: 68%

The human cytomegalovirus UL116 glycoprotein is a chaperone to control gH-based complexes levels on virions

Vezzani

Amendola²,

Yü³

et al. 2020

Preprint

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Human cytomegalovirus (HCMV) relies in large part upon the viral membrane fusion glycoprotein B (gB) and two alternative gH/gL complexes, gH/gL/gO (Trimer) and the gH/gL/UL128/UL130/UL131A (Pentamer) to enter into cells. The relative amounts of the Trimer and Pentamer vary among HCMV strains and contribute to differences in cell tropism. Although the viral ER resident protein UL148 has been shown to interact with gH to facilitate gO incorporation, the mechanisms that favor the assembly and maturation of one complex over another remain poorly understood. HCMV virions also contain an alternative non-disulfide bound heterodimer comprised of gH and UL116 whose function remains unknown. Here, we show that disruption of HCMV gene UL116 causes infectivity defects of ~10-fold relative to wild-type virus and leads to reduced expression of both gH/gL complexes in virions. Furthermore, gH that is not covalently bound to other viral glycoproteins, which are readily detected in wild-type HCMV virions, become undetectable in the absence of UL116 suggesting that the gH/UL116 complex is abundant in virions. We find evidence that UL116 and UL148 interact during infection indicating that the two proteins might cooperate to regulate the abundance of HCMV gH complexes. Altogether, these results are consistent with a role of UL116 as a chaperone for gH during the assembly and maturation of gH complexes in infected cells.

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Section: Discussioncontrasting

confidence: 68%

The human cytomegalovirus UL116 glycoprotein is a chaperone to control gH-based complexes levels on virions

Vezzani

Amendola²,

Yü³

et al. 2020

Preprint

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“…However, it has more recently been reported that viruses lacking gH/gL/UL128-131 can spread cell to cell, but this is dependent on the gH/gL/gO receptor PDGFRa (48). Furthermore, a recent study by our group demonstrated that switching the UL74 allele in both TR and ME backgrounds could influence the efficiency of cell-to-cell spread, demonstrating that there were epistatic phenomena involved inasmuch as the influence of some UL74 alleles was observed in only one of the two genetic backgrounds (65).…”

Section: Discussionmentioning

confidence: 86%

Specialization for Cell-Free or Cell-to-Cell Spread of BAC-Cloned Human Cytomegalovirus Strains Is Determined by Factors beyond the UL128-131 and RL13 Loci

Schultz

Lanchy

Day

et al. 2020

J Virol

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It is widely held that clinical isolates of human cytomegalovirus (HCMV) are highly cell associated, and mutations affecting the UL128-131 and RL13 loci that arise in culture lead to the appearance of a cell-free spread phenotype. The bacterial artificial chromosome (BAC) clone Merlin (ME) expresses abundant UL128-131, is RL13 impaired, and produces low infectivity virions in fibroblasts, whereas TB40/e (TB) and TR are low in UL128-131, are RL13 intact, and produce virions of much higher infectivity. Despite these differences, quantification of spread by flow cytometry revealed remarkably similar spread efficiencies in fibroblasts. In epithelial cells, ME spread more efficiently, consistent with robust UL128-131 expression. Strikingly, ME spread far better than did TB or TR in the presence of neutralizing antibodies on both cell types, indicating that ME is not simply deficient at cell-free spread but is particularly efficient at cell-to-cell spread, whereas TB and TR cell-to-cell spread is poor. Sonically disrupted ME-infected cells contained scant infectivity, suggesting that the efficient cell-to-cell spread mechanism of ME depends on features of the intact cells such as junctions or intracellular trafficking processes. Even when UL128-131 was transcriptionally repressed, cell-to-cell spread of ME was still more efficient than that of TB or TR. Moreover, RL13 expression comparably reduced both cell-free and cell-to-cell spread of all three strains, suggesting that it acts at a stage of assembly and/or egress common to both routes of spread. Thus, HCMV strains can be highly specialized for either for cell-free or cell-to-cell spread, and these phenotypes are determined by factors beyond the UL128-131 or RL13 loci. IMPORTANCE Both cell-free and cell-to-cell spread are likely important for the natural biology of HCMV. In culture, strains clearly differ in their capacity for cell-free spread as a result of differences in the quantity and infectivity of extracellular released progeny. However, it has been unclear whether “cell-associated” phenotypes are simply the result of poor cell-free spread or are indicative of particularly efficient cell-to-cell spread mechanisms. By measuring the kinetics of spread at early time points, we were able to show that HCMV strains can be highly specialized to either cell-free or cell-to-cell mechanisms, and this was not strictly linked the efficiency of cell-free spread. Our results provide a conceptual approach to evaluating intervention strategies for their ability to limit cell-free or cell-to-cell spread as independent processes.

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“…In the case of GPCMV, TAMYC and 22122, strains exhibited 25% difference in the gO amino acid sequence and importantly two N-terminal region glycosylation sites were missing, which potentially alters ability of the viral trimer (gH/gL/gO) to interact with cell receptor PDGFRA which can be influenced by glycosylation [ 30 ]. In HCMV, gO polymorphisms modify virus cell-free and cell-to-cell spread [ 48 ] and this might account for the basis of the TAMYC strain being highly cell-associated but this requires further study. Potentially, there are additional differences between the two GPCMV strains but this also awaits further evaluation.…”

Section: Discussionmentioning

confidence: 99%

Convalescent Immunity to Guinea Pig Cytomegalovirus Induces Limited Cross Strain Protection against Re-Infection but High-Level Protection against Congenital Disease

Choi

El-Hamdi

McGregor

2020

IJMS

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The guinea pig is the only small animal model for congenital cytomegalovirus (cCMV) but requires guinea pig cytomegalovirus (GPCMV). Current GPCMV research utilizes prototype strain 22122, which limits the translational impact of GPCMV as numerous human CMV strains exist and cCMV is possible in the setting of re-infection. A novel strain of GPCMV (TAMYC) exhibited differences to 22122 in various glycoproteins with GP74 (gO homolog) the most variable (25% difference). Antibody ELISAs for TAMYC-convalescent animals evoked similar immune response to viral glycoprotein complexes (gB, gH/gL, gM/gN, pentamer) and cell-mediated response to pp65 homolog (GP83). Convalescent sera from TAMYC-infected animals neutralized GPCMV infection on fibroblasts but was less effective on epithelial cells. TAMYC-convalescent animals were not protected from dissemination of heterogenous virus challenge (22122). However, in a cCMV protection study, TAMYC-convalescent animals challenged mid-pregnancy (22122) exhibited high-level protection against cCMV compared to seronegative animals with pup transmission reduced from 80% (control) to 12%. Overall, pre-existing immunity in guinea pigs provides limited ability to prevent GPCMV re-infection by a different viral strain but provides a high level of protection against cCMV in heterogenous strain challenge. This level of cross protection against cCMV should be a prerequisite of any CMV vaccine.

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Polymorphisms in Human Cytomegalovirus Glycoprotein O (gO) Exert Epistatic Influences on Cell-Free and Cell-to-Cell Spread and Antibody Neutralization on gH Epitopes

Cited by 26 publications

References 66 publications

The human cytomegalovirus UL116 glycoprotein is a chaperone to control gH-based complexes levels on virions

The human cytomegalovirus UL116 glycoprotein is a chaperone to control gH-based complexes levels on virions

Specialization for Cell-Free or Cell-to-Cell Spread of BAC-Cloned Human Cytomegalovirus Strains Is Determined by Factors beyond the UL128-131 and RL13 Loci

Convalescent Immunity to Guinea Pig Cytomegalovirus Induces Limited Cross Strain Protection against Re-Infection but High-Level Protection against Congenital Disease

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