scholarly journals Specialization for cell-free or cell-to-cell spread of BAC-cloned HCMV strains is determined by factors beyond the UL128-131 and RL13 loci

2019 ◽  
Author(s):  
Eric P. Schultz ◽  
Jean-Marc Lanchy ◽  
Le Zhang Day ◽  
Qin Yu ◽  
Christopher Peterson ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Early Time ◽  
Cell Types ◽  
Conceptual Approach ◽  
Bac Clone ◽  
Intact Cells ◽  
A Cell ◽  
Infected Cells ◽  
Kinetics Of ◽  
Cell Spread

ABSTRACTIt 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 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, 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 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 transcriptional repressed, cell-to-cell spread of ME was still more efficient than 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.IMPORTANCEBoth 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.

scholarly journals 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

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Eric P. Schultz ◽  
Jean-Marc Lanchy ◽  
Le Zhang Day ◽  
Qin Yu ◽  
Christopher Peterson ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Neutralizing Antibodies ◽  
Early Time ◽  
Artificial Chromosome ◽  
Cell Types ◽  
Conceptual Approach ◽  
Bac Clone ◽  
Intact Cells ◽  
A Cell ◽  
Cell Spread

ABSTRACT 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.

scholarly journals SARS-CoV-2 cell-to-cell spread occurs rapidly and is insensitive to antibody neutralization

2021 ◽  
Author(s):  
Laurelle Jackson ◽  
Hylton Rodel ◽  
Shi-Hsia Hwa ◽  
Sandile Cele ◽  
Yashica Ganga ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Cell Fusion ◽  
Neutralizing Antibodies ◽  
Time Lapse ◽  
Cell Types ◽  
Live Virus ◽  
Multinucleated Cells ◽  
Close Range ◽  
Infected Cells ◽  
Cell Spread

Viruses increase the efficiency of close-range transmission between cells by manipulating cellular physiology and behavior, and SARS-CoV-2 uses cell fusion as one mechanism for cell-to-cell spread. Here we visualized infection using time-lapse microscopy of a human lung cell line and used live virus neutralization to determine the sensitivity of SARS-CoV-2 cell-to-cell spread to neutralizing antibodies. SARS-CoV-2 infection rapidly led to cell fusion, forming multinucleated cells with clustered nuclei which started to be detected at 6h post-infection. To compare sensitivity of cell-to-cell spread to neutralization, we infected either with cell-free virus or with single infected cells expressing on their surface the SARS-CoV-2 spike protein. We tested two variants of SARS-CoV-2: B.1.117 containing only the D614G substitution, and the escape variant B.1.351. We used the much smaller area of single infected cells relative to infection foci to exclude any input infected cells which did not lead to transmission. The monoclonal antibody and convalescent plasma we tested neutralized cell-free SARS-CoV-2, with the exception of B.1.351 virus, which was poorly neutralized with plasma from non-B.1.351 infections. In contrast, cell-to-cell spread of SARS-CoV-2 showed no sensitivity to monoclonal antibody or convalescent plasma neutralization. These observations suggest that, once cells are infected, SARS-CoV-2 may be more difficult to neutralize in cell types and anatomical compartments permissive for cell-to-cell spread.

scholarly journals Glycolipid and glycoprotein transport through the Golgi complex are similar biochemically and kinetically. Reconstitution of glycolipid transport in a cell free system.

1990 ◽  
Vol 111 (2) ◽  
pp. 421-428 ◽  
Author(s):  
B W Wattenberg
Keyword(s):  
Sialic Acid ◽  
Golgi Apparatus ◽  
Chinese Hamster ◽  
Free System ◽  
Cell Free System ◽  
Glycoprotein G ◽  
A Cell ◽  
Infected Cells ◽  
Glycoprotein Transport ◽  
Kinetics Of

Glycolipid transport between compartments of the Golgi apparatus has been reconstituted in a cell free system. Transport of lactosylceramide (galactose beta 1-4-glucose-ceramide) was followed from a donor to an acceptor Golgi population. The major glycolipid in CHO cells is GM3 (sialic acid alpha 2-3 galactose beta 1-4-glucose-ceramide). Donor membranes were derived from a Chinese hamster ovary (CHO) cell mutant (Lec2) deficient in the Golgi CMP-sialic acid transporter, and therefore contained lactosylceramide as the predominant glycolipid. Acceptor Golgi apparatus was prepared from another mutant, Lec8, which is defective in UDP-Gal transport. Thus, glucosylceramide is the major glycolipid in Lec8 cells. Transport was measured by the incorporation of labeled sialic acid into lactosylceramide (present originally in the donor) by transport to acceptor membranes, forming GM3. This incorporation was dependent on ATP, cytosolic components, intact membranes, and elevated temperature. Donor membranes were prepared from Lec2 cells infected with vesicular stomatitus virus (VSV). These membranes therefore contain the VSV membrane glycoprotein, G protein. Donor membranes derived from VSV-infected cells could then be used to monitor both glycolipid and glycoprotein transport. Transport of these two types of molecules between Golgi compartments was compared biochemically and kinetically. Glycolipid transport required the N-ethylmaleimide sensitive factor previously shown to act in glycoprotein transport (Glick, B. S., and J. E. Rothman. 1987. Nature [Lond.]. 326:309-312; Rothman, J. E. 1987. J. Biol. Chem. 262:12502-12510). GTP gamma S inhibited glycolipid and glycoprotein transport similarly. The kinetics of transport of glycolipid and glycoprotein were also compared. The kinetics of transport to the end of the pathway were similar, as were the kinetics of movement into a defined transport intermediate. It is concluded that glycolipid and glycoprotein transport through the Golgi occur by similar if not identical mechanisms.

scholarly journals The Multiplicity of Infection of a Plant Virus Varies during Colonization of Its Eukaryotic Host

2009 ◽  
Vol 83 (15) ◽  
pp. 7487-7494 ◽  
Author(s):  
Pablo González-Jara ◽  
Aurora Fraile ◽  
Tomás Canto ◽  
Fernando García-Arenal
Keyword(s):  
Fluorescent Proteins ◽  
Infection Process ◽  
Multiplicity Of Infection ◽  
Genome Expression ◽  
Red Fluorescent Proteins ◽  
A Cell ◽  
Infected Cells ◽  
Infection Cycles ◽  
Virus Genomes ◽  
Kinetics Of

ABSTRACT The multiplicity of infection (MOI), i.e., the number of virus genomes that infect a cell, is a key parameter in virus evolution, as it determines processes such as genetic exchange among genomes, selection intensity on viral genes, epistatic interactions, and the evolution of multipartite viruses. In fact, the MOI level is equivalent to the virus ploidy during genome expression. Nevertheless, there are few experimental estimates of MOI, particularly for viruses with eukaryotic hosts. Here we estimate the MOI of Tobacco mosaic virus (TMV) in its systemic host, Nicotiana benthamiana. The progress of infection of two TMV genotypes, differently tagged with the green or red fluorescent proteins GFP and RFP, was monitored by determining the number of leaf cell protoplasts that showed GFP, RFP, or GFP and RFP fluorescence at different times postinoculation. This approach allowed the quantitative analysis of the kinetics of infection and estimation of the generation time and the number of infection cycles required for leaf colonization. MOI levels were estimated from the frequency of cells infected by only TMV-GFP or TMV-RFP. The MOI was high, but it changed during the infection process, decreasing from an initial level of about 6 to a final one of 1 to 2, with most infection cycles occurring at the higher MOI levels. The decreasing MOI can be explained by mechanisms limiting superinfection and/or by genotype competition within double-infected cells, which was shown to occur in coinfected tobacco protoplasts. To our knowledge, this is the first estimate of MOI during virus colonization of a eukaryotic host.

A new plaque system for canine distemper: characteristics of the green strain of canine distemper virus

1979 ◽  
Vol 25 (6) ◽  
pp. 680-685 ◽  
Author(s):  
C. K. Ho ◽  
L. A. Babiuk
Keyword(s):  
Canine Distemper Virus ◽  
Cell Types ◽  
Kidney Cells ◽  
Canine Distemper ◽  
Kinetics Of Adsorption ◽  
Green Strain ◽  
Dog Kidney ◽  
Infected Cells ◽  
Kinetics Of ◽  
Cellular Destruction

A Vero cell adapted Green strain of canine distemper virus (CDV) was tested for its plaque-forming capacity in different cell lines. Plaque formation was observed in HEp-2, BS-C-I, and HeLa cells but not in Vero or dog kidney cells even though replication and cytopathology were observed in the latter cell types. In the cells in which the virus was capable of producing plaques, the plaques were observed within 24 h post infection and continued to increase in size with subsequent cellular destruction such that by 72 h postinfection the size of the plaques approached 0.5 mm. With the use of the plaquing technique, it was possible to demonstrate the thermal lability of the virus as well as the kinetics of adsorption. Thus, it was shown that the half-life of the virus was 125 min at 25 °C, 75 min at 35 °C, and 65 min at 37 °C. The rate of adsorption of CDV to HEp-2 cells was 17.2% in 30 min at 37 °C and continued slowly for 4 h before completion. Application of this rapid plaque-forming assay to plaque-reduction tests for CDV antibody and for CDV-infected cells by the infectious center assay are described.

scholarly journals Stabilizing the HIV-1 envelope glycoprotein State 2A conformation

2020 ◽  
Author(s):  
Dani Vézina ◽  
Shang Yu Gong ◽  
William D. Tolbert ◽  
Shilei Ding ◽  
Dung Nguyen ◽  
...  
Keyword(s):  
Envelope Glycoprotein ◽  
Neutralizing Antibodies ◽  
Coreceptor Binding ◽  
Viral Particles ◽  
A Cell ◽  
Infected Cells ◽  
Cluster A ◽  
State 1 ◽  
Hiv 1 ◽  
Conformation State

The HIV-1 envelope glycoprotein (Env) trimer [(gp120/gp41)3] is a metastable complex expressed at the surface of viral particles and infected cells that samples different conformations. Before engaging CD4, Env adopts an antibody-resistant “closed” conformation (State 1). CD4 binding triggers an intermediate conformation (State 2) and then a more “open” conformation (State 3) that can be recognized by non-neutralizing antibodies (nnAbs) such as those that recognize the coreceptor binding site (CoRBS). Binding of antibodies to the CoRBS permits another family of nnAbs, the anti-cluster A family of Abs which target the gp120 inner domain, to bind and stabilize an asymmetric conformation (State 2A). Cells expressing Env in this conformation are susceptible to antibody-dependent cellular cytotoxicity (ADCC). This conformation can be stabilized by small-molecule CD4 mimetics (CD4mc) or soluble CD4 (sCD4) in combination with anti-CoRBS Ab and anti-cluster A antibodies. The precise stoichiometry of each component that permits this sequential opening of Env remains unknown. Here, we used a cell-based ELISA (CBE) assay to evaluate each component individually. In this assay we used a “trimer mixing” approach by combining wild-type (wt) subunits with subunits impaired for CD4 or CoRBS Ab binding. This enabled us to show that State 2A requires all three gp120 subunits to be bound by sCD4/CD4mc and anti-CoRBS Abs. Two of these subunits can then bind anti-cluster A Abs. Altogether, our data suggests how this antibody vulnerable Env conformation is stabilized. Importance Stabilization of HIV-1 Env State 2A has been shown to sensitize infected cells to ADCC. State 2A can be stabilized by a “cocktail” composed of CD4mc, anti-CoRBS and anti-cluster A Abs. We present evidence that optimal State 2A stabilization requires all three gp120 subunits to be bound by both CD4mc and anti-CoRBS Abs. Our study provides valuable information on how to stabilize this ADCC-vulnerable conformation. Strategies aimed at stabilizing State 2A might have therapeutic utility.

scholarly journals Polymorphisms in Human Cytomegalovirus gO Exert Epistatic Influences on Cell-Free and Cell-To-Cell Spread, and Antibody Neutralization on gH Epitopes

2019 ◽  
Author(s):  
Le Zhang Day ◽  
Cora Stegmann ◽  
Eric P. Schultz ◽  
Jean-Marc Lanchy ◽  
Qin Yu ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Viral Genome ◽  
Genetic Background ◽  
Neutralizing Antibodies ◽  
Important Determinant ◽  
Cell Types ◽  
Cell Tropism ◽  
Laboratory Studies ◽  
Antibody Neutralization ◽  
Cell Spread

ABSTRACTThe human cytomegalovirus (HCMV) glycoproteins H and L (gH/gL) can be bound by either gO, or the UL128-131 proteins to form complexes that facilitate entry and spread and the complexes formed are important targets of neutralizing antibodies. Strains of HCMV vary considerably in the levels of gH/gL/gO and gH/gL/UL128-131 and this can impact infectivity and cell tropism. In this report, we investigated how natural interstrain variation in the amino acid sequence of gO influences the biology of HCMV. Heterologous gO recombinants were constructed in which 6 of the 8 alleles or genotypes (GT) of gO were analyzed in the backgrounds of strain TR and Merlin (ME). The levels of gH/gL complexes were not affected, but there were impacts on entry, spread and neutralization by anti-gH antibodies. AD169 (AD) gO (GT1a) drastically reduced cell-free infectivity of both strains on fibroblasts and epithelial cells. PHgO(GT2a) increased cell-free infectivity of TR in both cell types, but spread in fibroblasts was impaired. In contrast, spread of ME in both cell types was enhanced by Towne (TN) gO (GT4), despite similar cell-free infectivity. TR expressing TNgO(GT4) was resistant to neutralization by anti-gH antibodies AP86 and 14-4b, whereas ADgO(GT1a) conferred resistance to 14-4b, but enhanced neutralization by AP86. Conversely, ME expressing ADgO(GT1a) was more resistant to 14-4b. These results suggest; 1) mechanistically distinct roles for gH/gL/gO in cell-free and cell-to-cell spread, 2) gO isoforms can differentially shield the virus from neutralizing antibodies, and 3) effects of gO polymorphisms are epistatically dependent on other variable loci.IMPORTANCEAdvances in HCMV population genetics have greatly outpaced understanding of the links between genetic diversity and phenotypic variation. Moreover, recombination between genotypes may shuffle variable loci into various combinations with unknown outcomes. UL74(gO) is an important determinant of HCMV infectivity, and one of the most diverse loci in the viral genome. By analyzing interstrain heterologous UL74(gO) recombinants, we show that gO diversity can have dramatic impacts on cell-free and cell-to-cell spread as well as on antibody neutralization and that the manifestation of these impacts can be subject to epistatic influences of the global genetic background. These results highlight the potential limitations of laboratory studies of HCMV biology that use single, isolated genotypes or strains.

scholarly journals Essential Role of CCL2 in Clustering of Splenic ERTR-9+ Macrophages during Infection of BALB/c Mice by Listeria monocytogenes

2006 ◽  
Vol 75 (1) ◽  
pp. 462-470 ◽  
Author(s):  
Jadwiga Jablonska ◽  
Kurt E. Dittmar ◽  
Tanja Kleinke ◽  
Jan Buer ◽  
Siegfried Weiss
Keyword(s):  
Listeria Monocytogenes ◽  
Marginal Zone ◽  
Early Time ◽  
Cell Types ◽  
Host Cells ◽  
Early Time Point ◽  
Infected Cells ◽  
Different Cell Types ◽  
Time Point

ABSTRACT Early interactions between pathogens and host cells are often decisive for the subsequent course of infection. Here we investigated early events during infection by Listeria monocytogenes, a ubiquitously occurring facultative intracellular microorganism that exhibits severe pathogenicity, mainly in immunocompromised individuals. We show that the inflammatory chemokine CCL2 is highly up-regulated early after Listeria infection in spleens of BALB/c mice. ERTR-9+ macrophages of the marginal zone were identified as the only infected cells and exclusive producers of CCL2 at the early time point. Consequently, clusters of different cell types were formed around infected ERTR-9+ cells. Metallophilic MOMA-1+ marginal zone macrophages were, however, excluded from the clusters and migrated into the B-cell follicles. Depletion of CCL2 during infection resulted in a different composition of cell clusters in the spleen and increased the mortality rate of treated mice. Interestingly, ERTR-9+ macrophages no longer were part of clusters in such mice but remained at their original location in the marginal zone.

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

2020 ◽  
Vol 94 (8) ◽  
Author(s):  
Le Zhang Day ◽  
Cora Stegmann ◽  
Eric P. Schultz ◽  
Jean-Marc Lanchy ◽  
Qin Yu ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Viral Genome ◽  
Genetic Background ◽  
Neutralizing Antibodies ◽  
Important Determinant ◽  
Cell Types ◽  
Cell Tropism ◽  
Laboratory Studies ◽  
Antibody Neutralization ◽  
Cell Spread

ABSTRACT Human cytomegalovirus (HCMV) glycoproteins H and L (gH/gL) can be bound by either gO or the UL128 to UL131 proteins (referred to here as UL128-131) to form complexes that facilitate entry and spread, and the complexes formed are important targets of neutralizing antibodies. Strains of HCMV vary considerably in the levels of gH/gL/gO and gH/gL/UL128-131, and this can impact infectivity and cell tropism. In this study, we investigated how natural interstrain variation in the amino acid sequence of gO influences the biology of HCMV. Heterologous gO recombinants were constructed in which 6 of the 8 alleles or genotypes (GT) of gO were analyzed in the backgrounds of strains TR and Merlin (ME). The levels of gH/gL complexes were not affected, but there were impacts on entry, spread, and neutralization by anti-gH antibodies. AD169 (AD) gO (GT1a) [referred to here as ADgO(GT1a)] drastically reduced cell-free infectivity of both strains on fibroblasts and epithelial cells. PHgO(GT2a) increased cell-free infectivity of TR in both cell types, but spread in fibroblasts was impaired. In contrast, spread of ME in both cell types was enhanced by Towne (TN) gO (GT4), despite similar cell-free infectivity. TR expressing TNgO(GT4) was resistant to neutralization by anti-gH antibodies AP86 and 14-4b, whereas ADgO(GT1a) conferred resistance to 14-4b but enhanced neutralization by AP86. Conversely, ME expressing ADgO(GT1a) was more resistant to 14-4b. These results suggest that (i) there are mechanistically distinct roles for gH/gL/gO in cell-free and cell-to-cell spread, (ii) gO isoforms can differentially shield the virus from neutralizing antibodies, and (iii) effects of gO polymorphisms are epistatically dependent on other variable loci. IMPORTANCE Advances in HCMV population genetics have greatly outpaced understanding of the links between genetic diversity and phenotypic variation. Moreover, recombination between genotypes may shuffle variable loci into various combinations with unknown outcomes. UL74(gO) is an important determinant of HCMV infectivity and one of the most diverse loci in the viral genome. By analyzing interstrain heterologous UL74(gO) recombinants, we showed that gO diversity can have dramatic impacts on cell-free and cell-to-cell spread as well as on antibody neutralization and that the manifestation of these impacts can be subject to epistatic influences of the global genetic background. These results highlight the potential limitations of laboratory studies of HCMV biology that use single, isolated genotypes or strains.

scholarly journals HCMV trimer- and pentamer-specific antibodies synergize for virus neutralization but do not correlate with congenital transmission

2019 ◽  
Vol 116 (9) ◽  
pp. 3728-3733 ◽  
Author(s):  
Adam L. Vanarsdall ◽  
Andrea L. Chin ◽  
Jing Liu ◽  
Theodore S. Jardetzky ◽  
James O. Mudd ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Cell Types ◽  
The Other ◽  
Major Focus ◽  
Specific Antibodies ◽  
Transplant Patients ◽  
Human Sera ◽  
Cell Spread ◽  
Major Target ◽  
Pregnant Mothers

Human cytomegalovirus (HCMV) causes substantial disease in transplant patients and harms the development of the nervous system in babies infected in utero. Thus, there is a major focus on developing safe and effective HCMV vaccines. Evidence has been presented that a major target of neutralizing antibodies (NAbs) is the HCMV pentamer glycoprotein gH/gL/UL128-131. In some studies, most of the NAbs in animal or human sera were found to recognize the pentamer, which mediates HCMV entry into endothelial and epithelial cells. It was also reported that pentamer-specific antibodies correlate with protection against transmission from mothers to babies. One problem with the studies on pentamer-specific NAbs to date has been that the studies did not compare the pentamer to the other major form of gH/gL, the gH/gL/gO trimer, which is essential for entry into all cell types. Here, we demonstrate that both trimer and pentamer NAbs are frequently found in human transplant patients’ and pregnant mothers’ sera. Depletion of human sera with trimer caused reductions in NAbs similar to that observed following depletion with the pentamer. The trimer- and pentamer-specific antibodies acted in a synergistic fashion to neutralize HCMV and also to prevent virus cell-to-cell spread. Importantly, there was no correlation between the titers of trimer- and pentamer-specific NAbs and transmission of HCMV from mothers to babies. Therefore, both the trimer and pentamer are important targets of NAbs. Nevertheless, these antibodies do not protect against transmission of HCMV from mothers to babies.

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