Tracking Murine Gammaherpesvirus 68 Infection of Germinal Center B Cells In Vivo

ABSTRACT Intranasal infection of mice with murine gammaherpesvirus 68 (MHV-68), a virus genetically related to the human pathogen Kaposi's sarcoma-associated herpesvirus, results in a persistent, latent infection in the spleen and other lymphoid organs. Here, we have determined the frequency of virus infection in splenic dendritic cells, macrophages, and several B-cell subpopulations, and we quantified cell type-dependent virus transcription patterns. The frequencies of virus genome positive cells were maximal at 14 days postinfection in all splenic cell populations analyzed. Marginal zone and germinal center B cells harbored the highest frequency of infection and the former population accounted for approximately half the total number of infected B cells. Analysis of virus transcription during the establishment of latency revealed that virus gene expression in B cells was restricted and dependent on the differentiation stage of the B cell. Notably, transcription of ORF73 was detected in germinal center B cells, a finding in agreement with the predicted latent genome maintenance function of ORF73 in dividing cells. At late times after infection, virus DNA could only be detected in newly formed and germinal center B cells, which suggests that B cells play a critical role in facilitating life-long latency.

Download Full-text

Evidence for a Multiprotein Gamma-2 Herpesvirus Entry Complex

Journal of Virology ◽

10.1128/jvi.01141-07 ◽

2007 ◽

Vol 81 (23) ◽

pp. 13082-13091 ◽

Cited By ~ 21

Author(s):

Laurent Gillet ◽

Philip G. Stevenson

Keyword(s):

B Cells ◽

Specific Antibody ◽

Cell Binding ◽

Murine Gammaherpesvirus ◽

Single Entry ◽

Single Complex ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68 ◽

Better Than

ABSTRACT Herpesviruses use multiple virion glycoproteins to enter cells. How these work together is not well understood: some may act separately or they may form a single complex. Murine gammaherpesvirus 68 (MHV-68) gB, gH, gL, and gp150 all participate in entry. gB and gL are involved in binding, gB and gH are conserved fusion proteins, and gp150 inhibits cell binding until glycosaminoglycans are engaged. Here we show that a gH-specific antibody coprecipitates gB and thus that gH and gB are associated in the virion membrane. A gH/gL-specific antibody also coprecipitated gB, implying a tripartite complex of gL/gH/gB, although the gH/gB association did not require gL. The association was also independent of gp150, and gp150 was not demonstrably bound to gB or gH. However, gp150 incorporation into virions was partly gL dependent, suggesting that it too contributes to a single entry complex. gp150− and gL− gp150− mutants bound better than the wild type to B cells and readily colonized B cells in vivo. Thus, gp150 and gL appear to be epithelial cell-adapted accessories of a core gB/gH entry complex. The cell binding revealed by gp150 disruption did not require gL and therefore seemed most likely to involve gB.

Download Full-text

B Cell-Intrinsic Expression of Interferon Regulatory Factor 1 Supports Chronic Murine Gammaherpesvirus 68 Infection

Journal of Virology ◽

10.1128/jvi.00399-20 ◽

2020 ◽

Vol 94 (13) ◽

Author(s):

C. N. Jondle ◽

K. E. Johnson ◽

A. A. Uitenbroek ◽

P. A. Sylvester ◽

C. Nguyen ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Germinal Center ◽

Chronic Infection ◽

Latent Reservoir ◽

B Cell Differentiation ◽

B Cell Lymphomas ◽

Murine Gammaherpesvirus ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

ABSTRACT Gammaherpesviruses are ubiquitous pathogens that are associated with cancers, including B cell lymphomas. These viruses are unique in that they infect naive B cells and subsequently drive a robust polyclonal germinal center response in order to amplify the latent reservoir and to establish lifelong infection in memory B cells. The gammaherpesvirus-driven germinal center response in combination with robust infection of germinal center B cells is thought to precipitate lymphomagenesis. Importantly, host and viral factors that selectively affect the gammaherpesvirus-driven germinal center response remain poorly understood. Global deficiency of antiviral tumor-suppressive interferon regulatory factor 1 (IRF-1) selectively promotes the murine gammaherpesvirus 68 (MHV68)-driven germinal center response and expansion of the viral latent reservoir. To determine the extent to which antiviral effects of IRF-1 are B cell intrinsic, we generated mice with conditional IRF-1 deficiency. Surprisingly, B cell-specific IRF-1 deficiency attenuated the establishment of chronic infection and the germinal center response, indicating that MHV68 may, in a B cell-intrinsic manner, usurp IRF-1 to promote the germinal center response and expansion of the latent reservoir. Further, we found that B cell-specific IRF-1 deficiency led to reduced levels of active tyrosine phosphatase SHP1, which plays a B cell-intrinsic proviral function during MHV68 infection. Finally, results of this study indicate that the antiviral functions of IRF-1 unveiled in MHV68-infected mice with global IRF-1 deficiency are mediated via IRF-1 expression by non-B cell populations. IMPORTANCE Gammaherpesviruses establish lifelong infection in over 95% of all adults and are associated with B cell lymphomas. The virus’s manipulation of the germinal center response and B cell differentiation to establish lifelong infection is thought to also precipitate malignant transformation, through a mechanism that remains poorly understood. The host transcription factor IRF-1, a well-established tumor suppressor, selectively attenuates MHV68-driven germinal center response, a phenotype that we originally hypothesized to occur in a B cell-intrinsic manner. In contrast, in testing, B cell-intrinsic IRF-1 expression promoted the MHV68-driven germinal center response and the establishment of chronic infection. Our report highlights the underappreciated multifaceted role of IRF-1 in MHV68 infection and pathogenesis.

Download Full-text

p53 Controls Murine Gammaherpesvirus Latency and Prevents Infection-Associated IgH/c-Myc Translocations

10.1101/2020.08.02.233148 ◽

2020 ◽

Author(s):

Shana M. Owens ◽

Jeffrey M. Sifford ◽

Gang Li ◽

Eduardo Salinas ◽

Debopam Ghosh ◽

...

Keyword(s):

B Cells ◽

Cell Cycle Progression ◽

Cellular Proliferation ◽

Host Restriction ◽

Murine Gammaherpesvirus ◽

Host Restriction Factor ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

ABSTRACTGammaherpesviruses (GHVs) establish life-long infections and cause cancer in humans and other animals. To facilitate chronic infection, GHV oncoproteins promote cellular proliferation and differentiation. Aberrant cell-cycle progression driven by viral oncogenes should trigger activation of tumor suppressor p53, unless p53 is functionally deactivated during GHV latency establishment. However, interactions of GHVs with the p53 pathway during the establishment and maintenance of latent infection are poorly defined. Here we demonstrate in vivo that p53 is induced specifically in infected cells during latency establishment by murine gammaherpesvirus 68 (MHV68). In the absence of p53, MHV68 latency establishment was significantly increased, especially in germinal center B cells, and correlated with enhanced cellular proliferation. However, enhanced latency was not sustainable, and MHV68 exhibited a defect in long-term latency maintenance in p53-deficient mice. Moreover, IgH/c-Myc translocations were readily detected in B cells from infected p53-null mice indicating virus-driven genomic instability. These data demonstrate that p53 intrinsically restricts MHV68 latency establishment and reveal a paradigm in which a host restriction factor provides a long-term benefit to a chronic pathogen by limiting infection-associated damage.

Download Full-text

Long-Term Latent Murine Gammaherpesvirus 68 Infection Is Preferentially Found within the Surface Immunoglobulin D-Negative Subset of Splenic B Cells In Vivo

Journal of Virology ◽

10.1128/jvi.77.15.8310-8321.2003 ◽

2003 ◽

Vol 77 (15) ◽

pp. 8310-8321 ◽

Cited By ~ 107

Author(s):

David O. Willer ◽

Samuel H. Speck

Keyword(s):

B Cells ◽

Small Animal ◽

Cell Types ◽

Murine Gammaherpesvirus ◽

Surface Immunoglobulin ◽

Immunoglobulin D ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

ABSTRACT Murine gammaherpesvirus 68 (γHV68; also known as MHV-68) can establish a latent infection in both inbred and outbred strains of mice and, as such, provides a tractable small-animal model to address mechanisms and cell types involved in the establishment and maintenance of chronic gammaherpesvirus infection. Latency can be established at multiple anatomic sites, including the spleen and peritoneum; however, the contribution of distinct cell types to the maintenance of latency within these reservoirs remains poorly characterized. B cells are the major hematopoietic cell type harboring latent γHV68. We have analyzed various splenic B-cell subsets at early, intermediate, and late times postinfection and determined the frequency of cells either (i) capable of spontaneously reactivating latent γHV68 or (ii) harboring latent viral genome. These analyses demonstrated that latency is established in a variety of cell populations but that long-term latency (6 months postinfection) in the spleen after intranasal inoculation predominantly occurs in B cells. Furthermore, at late times postinfection latent γHV68 is largely confined to the surface immunoglobulin D-negative subset of B cells.

Download Full-text

Mature B cells are required for acute splenic infection, but not for establishment of latency, by murine gammaherpesvirus 68.

Journal of Virology ◽

10.1128/jvi.70.10.6775-6780.1996 ◽

1996 ◽

Vol 70 (10) ◽

pp. 6775-6780 ◽

Cited By ~ 194

Author(s):

K E Weck ◽

M L Barkon ◽

L I Yoo ◽

S H Speck ◽

I V Virgin HW

Keyword(s):

B Cells ◽

Murine Gammaherpesvirus ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

Download Full-text

Murine Gammaherpesvirus 68 Open Reading Frame 75c Tegument Protein Induces the Degradation of PML and Is Essential for Production of Infectious Virus

Journal of Virology ◽

10.1128/jvi.02752-07 ◽

2008 ◽

Vol 82 (16) ◽

pp. 8000-8012 ◽

Cited By ~ 39

Author(s):

Paul D. Ling ◽

Jie Tan ◽

Jaturong Sewatanon ◽

RongSheng Peng

Keyword(s):

Infectious Virus ◽

Nuclear Body ◽

Tegument Protein ◽

Suitable Model ◽

Virus Infections ◽

Reading Frame ◽

Murine Gammaherpesvirus ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

ABSTRACT Promyelocytic Leukemia nuclear body (PML NB) proteins mediate an intrinsic cellular host defense response against virus infections. Herpesviruses express proteins that modulate PML or PML-associated proteins by a variety of strategies, including degradation of PML or relocalization of PML NB proteins. The consequences of PML-herpesvirus interactions during infection in vivo have yet to be investigated in detail, largely because of the species-specific tropism of many human herpesviruses. Murine gammaherpesvirus 68 (γHV68) is emerging as a suitable model to study basic biological questions of virus-host interactions because it naturally infects mice. Therefore, we sought to determine whether γHV68 targets PML NBs as part of its natural life cycle. We found that γHV68 induces PML degradation through a proteasome-dependent mechanism and that loss of PML results in more robust virus replication in mouse fibroblasts. Surprisingly, γHV68-mediated PML degradation was mediated by the virion tegument protein ORF75c, which shares homology with the cellular formylglycinamide ribotide amidotransferase enzyme. In addition, we show that ORF75c is essential for production of infectious virus. ORF75 homologs are conserved in all rhadinoviruses but so far have no assigned functions. Our studies shed light on a potential role for this unusual protein in rhadinovirus biology and suggest that γHV68 will be a useful model for investigation of PML-herpesvirus interactions in vivo.

Download Full-text

Dendritic Cells Loaded with Tumor B Cells Elicit Broad Immunity against Murine Gammaherpesvirus 68 but Fail To Prevent Long-Term Latency

Journal of Virology ◽

10.1128/jvi.00571-10 ◽

2010 ◽

Vol 84 (17) ◽

pp. 8975-8979

Author(s):

Janet Weslow-Schmidt ◽

Fang Ye ◽

Stephanie S. Cush ◽

Kathleen A. Stuller ◽

Marcia A. Blackman ◽

...

Keyword(s):

Dendritic Cells ◽

B Cells ◽

Acute Infection ◽

Dendritic Cell Vaccination ◽

Murine Gammaherpesvirus ◽

Attenuated Viruses ◽

Gammaherpesvirus 68 ◽

Vaccine Approach ◽

Murine Gammaherpesvirus 68

ABSTRACT It is still unknown whether a noninfectious gammaherpesvirus vaccine is able to prevent or reduce virus persistence. This led us to use dendritic cells loaded with tumor B cells as a vaccine approach for the murine gammaherpesvirus 68 (γHV68) model of infection. Dendritic cells loaded with UV-irradiated latently infected tumor B cells induce broad, strong, and long-lasting immunity against γHV68. Dendritic cell vaccination prevents the enlargement of lymph nodes and severely limits acute infection and early latency but does not prevent γHV68 from establishing long-term latency. Our findings support the concept that attenuated viruses may be the best vaccine option for preventing gammaherpesvirus persistence.

Download Full-text

Telomerase activation in normal B lymphocytes and non-Hodgkin's lymphomas

Blood ◽

10.1182/blood.v88.1.222.222 ◽

1996 ◽

Vol 88 (1) ◽

pp. 222-229 ◽

Cited By ~ 111

Author(s):

KF Norrback ◽

K Dahlenborg ◽

R Carlsson ◽

G Roos

Keyword(s):

B Cells ◽

B Cell ◽

Germinal Center ◽

Telomerase Activity ◽

Lymphoid Tissues ◽

Low Grade ◽

Malignant Lymphomas ◽

Hodgkin's Lymphomas ◽

Germinal Center B Cells

Abstract Activation of telomerase seems to be a prerequisite for immortalization and is found in permanent cell lines and most malignant tumors. Normal somatic cells are generally telomerase negative, except for bone marrow stem cells. Weak activity is also present in peripheral blood cells. In the present study strong telomerase activity was demonstrated in vivo in normal mature cells of the immune system, as well as in malignant lymphomas. Benign lymph nodes had lower telomerase activity than benign tonsils, which exhibited intermediate to high activity comparable with findings in malignant lymphomas. In benign tonsils the activity seemed to be restricted to germinal center B cells. In benign lymphoid tissues telomerase activity correlated with B-cell numbers and cell proliferation, but this was not observed in the lymphoma group. High- grade lymphomas exhibited higher levels of telomerase compared with low- grade cases. The data showed that in vivo activation of telomerase is a characteristic feature of germinal center B cells. Different signals for activation of telomerase are likely to exist, one of them being immune stimulation. The data suggest that telomerase activity in malignant lymphomas can be explained by an “induction and retention” model, ie, transformation occurs in a normal, mature B cell with reactivated telomerase, which is retained in the neoplastic clone.

Download Full-text

Characterization of a Spontaneous 9.5-Kilobase-Deletion Mutant of Murine Gammaherpesvirus 68 Reveals Tissue-Specific Genetic Requirements for Latency

Journal of Virology ◽

10.1128/jvi.76.13.6532-6544.2002 ◽

2002 ◽

Vol 76 (13) ◽

pp. 6532-6544 ◽

Cited By ~ 22

Author(s):

Eric T. Clambey ◽

Herbert W. Virgin ◽

Samuel H. Speck

Keyword(s):

Deletion Mutant ◽

Latent Infection ◽

Loss Of Function ◽

Murine Gammaherpesvirus ◽

Peritoneal Cells ◽

Gammaherpesvirus 68 ◽

Murine Gammaherpesvirus 68

ABSTRACT Murine gammaherpesvirus 68 (γHV68 [also known as MHV-68]) establishes a latent infection in mice, providing a small-animal model with which to identify host and viral factors that regulate gammaherpesvirus latency. While γHV68 establishes a latent infection in multiple tissues, including splenocytes and peritoneal cells, the requirements for latent infection within these tissues are poorly defined. Here we report the characterization of a spontaneous 9.5-kb-deletion mutant of γHV68 that lacks the M1, M2, M3, and M4 genes and eight viral tRNA-like genes. Previously, this locus has been shown to contain the latency-associated M2, M3, and viral tRNA-like genes. Through characterization of this mutant, we found that the M1, M2, M3, M4 genes and the viral tRNA-like genes are dispensable for (i) in vitro replication and (ii) the establishment and maintenance of latency in vivo and reactivation from latency following intraperitoneal infection. In contrast, following intranasal infection with this mutant, there was a defect in splenic latency at both early and late times, a phenotype not observed in peritoneal cells. These results indicate (i) that there are different genetic requirements for the establishment of latency in different latent reservoirs and (ii) that the genetic requirements for latency depend on the route of infection. While some of these phenotypes have been observed with specific mutations in the M1 and M2 genes, other phenotypes have never been observed with the available γHV68 mutants. These studies highlight the importance of loss-of-function mutations in defining the genetic requirements for the establishment and maintenance of herpesvirus latency.

Download Full-text