Infection of blood and bone marrow cells with the human cytomegalovirus in vivo

Immune surveillance of cytomegalovirus in tissues

Cytomegalovirus (CMV), a representative member of the Betaherpesvirinae subfamily of herpesviruses, is common in the human population, but immunocompetent individuals are generally asymptomatic when infected with this virus. However, in immunocompromised individuals and immunologically immature fetuses and newborns, CMV can cause a wide range of often long-lasting morbidities and even death. CMV is not only widespread throughout the population but it is also widespread in its hosts, infecting and establishing latency in nearly all tissues and organs. Thus, understanding the pathogenesis of and immune responses to this virus is a prerequisite for developing effective prevention and treatment strategies. Multiple arms of the immune system are engaged to contain the infection, and general concepts of immune control of CMV are now reasonably well understood. Nonetheless, in recent years, tissue-specific immune responses have emerged as an essential factor for resolving CMV infection. As tissues differ in biology and function, so do immune responses to CMV and pathological processes during infection. This review discusses state-of-the-art knowledge of the immune response to CMV infection in tissues, with particular emphasis on several well-studied and most commonly affected organs.

Tumor Control by Cytomegalovirus: A Door Open for Oncolytic Virotherapy?

Belonging to the herpesviridae family, human cytomegalovirus (HCMV) is a well-known ubiquitous pathogen that establishes a lifelong infection in humans. Recently, a beneficial tumor-cytoreductive role of CMV infection has been defined in human and animal models. Described as a potential anti-tumoral activity, HCMV modulates the tumor microenvironment mainly by inducing cell death through apoptosis and prompting a robust stimulatory effect on the immune cells infiltrating the tumor tissue. However, major current limitations embrace transient protective effect and a viral dissemination potential in immunosuppressed hosts. The latter could be counteracted through direct viral intratumoral delivery, use of non-human strains, or even defective CMV vectors to ascertain transformed cells-selective tropism. This potential oncolytic activity could be complemented by tackling further platforms, namely combination with immune checkpoint inhibitors or epigenetic therapy, as well as the use of second-generation chimeric oncovirus, for instance HCMV/HSV-1 oncolytic virus. Overall, preliminary data support the use of CMV in viral oncolytic therapy as a viable option, establishing thus a potential new modality, where further assessment through extensive basic research armed by molecular biotechnology is compulsory.

Early CMV-replication after allogeneic stem cell transplantation is associated with a reduced relapse risk in lymphoma

A preventive effect of early human cytomegalovirus (HCMV) replication was evaluated in 136 non-Hodgkin lymphoma (NHL) patients with mature B-cell NHLs (n = 94), and mature T- and NK-cell NHLs (n = 42) after allogeneic stem cell transplantation (alloSCT). Most study-patients (85%) had received at least 2 cycles of chemotherapy and 60% had also received an autograft prior to alloSCT. First detection of CMV-replication by HCMV antigenemia/viremia was found at a median of day +33 after alloSCT. The cumulative incidence of relapse at 5 years after alloSCT was 38% (95% confidence interval [95%CI]: 26-49) in 82 patients without compared to 22% (95%CI: 8-37) in 54 patients with HCMV antigenemia/viremia (p = .013). A decreased relapse risk of HCMV replication was confirmed by multivariate analysis for HCMV antigenemia/viremia (Hazard ratio [HR]: 0.29, 95%CI: 0.11-0.76, p < .014). This report demonstrated a possible improvement of relapse incidence after replicative HCMV infection in patients with NHL after alloSCT.

Isolated Necrotizing Epiglottitis: Report of a Case in a Neutropenic Patient and Review of the Literature

Isolated necrotizing epiglottitis (INE) is an unusual condition that may develop in immunocompromised patients. Only 3 cases of INE have been reported in the English-language literature; this is the fourth case, one in a 27-year-old woman who had neutropenia due to cytomegalovirus infection. Stenotrophomonas maltophilia and Candida albicans were isolated from the culture of necrotic material. The features of INE are discussed here by reviewing the literature and by examining the characteristics of this case.

Cytomegalovirus induces apoptosis in acute leukemia cells as a virus-versus-leukemia function

Cytomegalovirus (HCMV) reactivation occurs frequently after hematopoietic stem cell transplantation and is associated with an increased treatment-related mortality. Induction of apoptosis by HCMV is unusual because HCMV utilizes various strategies to prevent apoptosis in infected cells in order to delay cell death and maintain viral replication. Here we show that HCMV can infect the acute leukemia cell lines Kasumi-1 (AML) and SD-1 (BCR-ABL-positive ALL), which inhibited their proliferation and induced apoptosis in almost all cells after 14 days. Although HCMV induced a significant up-regulation of the anti-apoptotic gene cFLIP and the anti-stress gene Gadd45a, and simultaneously down-regulated the pro-apoptotic genes p53, Gadd45gamma in Kasumi-1 and SD-1 cells, we found that these anti-apoptotic mechanisms failed in HCMV-infected acute leukemia cells and apoptosis occurred via a caspase-dependent pathway. We conclude that HCMV can provide anti-leukemic effects in vitro. To determine if this phenomenon may be clinically relevant further investigations will be required.

Maintenance of large numbers of virus genomes in human cytomegalovirus-infected T98G glioblastoma cells

After infection, human cytomegalovirus (HCMV) persists for life. Primary infections and reactivation of latent virus can both result in congenital infection, a leading cause of central nervous system birth defects. We previously reported long-term HCMV infection in the T98G glioblastoma cell line (1). HCMV infection has been further characterized in T98Gs, emphasizing the presence of HCMV DNA over an extended time frame. T98Gs were infected with either HCMV Towne or AD169-IE2-enhanced green fluorescent protein (eGFP) strains. Towne infections yielded mixed IE1 antigen-positive and -negative (Ag(+)/Ag(-)) populations. AD169-IE2-eGFP infections also yielded mixed populations, which were sorted to obtain an IE2(-) (Ag(-)) population. Viral gene expression over the course of infection was determined by immunofluorescent analysis (IFA) and reverse transcription-PCR (RT-PCR). The presence of HCMV genomes was determined by PCR, nested PCR (n-PCR), and fluorescence in situ hybridization (FISH). Compared to the HCMV latency model, THP-1, Towne-infected T98Gs expressed IE1 and latency-associated transcripts for longer periods, contained many more HCMV genomes during early passages, and carried genomes for a greatly extended period of passaging. Large numbers of HCMV genomes were also found in purified Ag(-) AD169-infected cells for the first several passages. Interestingly, latency transcripts were observed from very early times in the Towne-infected cells, even when IE1 was expressed at low levels. Although AD169-infected Ag(-) cells expressed no detectable levels of either IE1 or latency transcripts, they also maintained large numbers of genomes within the cell nuclei for several passages. These results identify HCMV-infected T98Gs as an attractive new model in the study of the long-term maintenance of virus genomes in the context of neural cell types.

IMPORTANCE

Our previous work showed that T98G glioblastoma cells were semipermissive to HCMV infection; virus trafficked to the nucleus, and yet only a proportion of cells stained positive for viral antigens, thus allowing continual subculturing and passaging. The cells eventually transitioned to a state where viral genomes were maintained without viral antigen expression or virion production. Here we report that during long-term T98G infection, large numbers of genomes were maintained within all of the cells' nuclei for the first several passages (through passage 4 [P4]), even in the presence of continual cellular division. Surprisingly, genomes were maintained, albeit at a lower level, through day 41. This is decidedly longer than in any other latency model system that has been described to date. We believe that this system offers a useful model to aid in unraveling the cellular components involved in viral genome maintenance (and presumably replication) in cells carrying long-term latent genomes in a neural context.

Cytomegalovirus in bone marrow cells correlates with cytomegalovirus in peripheral blood leukocytes

In allogeneic hematopoietic stem cell transplant recipients with bone marrow (BM) suppression, cytomegalovirus (CMV) pp65 antigenemia and DNA were detectable in peripheral blood leukocytes (PBL) and BM cells. A relationship between CMV infection of PBL and BM cells has been found.

A myeloid progenitor cell line capable of supporting human cytomegalovirus latency and reactivation, resulting in infectious progeny

Human cytomegalovirus (HCMV) is a herpesvirus that establishes a lifelong, latent infection within a host. At times when the immune system is compromised, the virus undergoes a lytic reactivation producing infectious progeny. The identification and understanding of the biological mechanisms underlying HCMV latency and reactivation are not completely defined. To this end, we have developed a tractable in vitro model system to investigate these phases of viral infection using a clonal population of myeloid progenitor cells (Kasumi-3 cells). Infection of these cells results in maintenance of the viral genome with restricted viral RNA expression that is reversed with the addition of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA, also known as PMA). Additionally, a latent viral transcript (LUNA) is expressed at times where viral lytic transcription is suppressed. Infected Kasumi-3 cells initiate production of infectious virus following TPA treatment, which requires cell-to-cell contact for efficient transfer of virus to other cell types. Importantly, lytically infected fibroblast, endothelial, or epithelial cells can transfer virus to Kasumi-3 cells, which fail to initiate lytic replication until stimulated with TPA. Finally, inflammatory cytokines, in addition to the pharmacological agent TPA, are sufficient for transcription of immediate-early (IE) genes following latent infection. Taken together, our findings argue that the Kasumi-3 cell line is a tractable in vitro model system with which to study HCMV latency and reactivation.

A case of acute hepatitis E associated with multidrug hypersensitivity and cytomegalovirus reactivation

A 65-year-old Japanese man was hospitalized because of acute hepatitis and severe cholestasis due to hepatitis E virus (HEV) infection combined with a drug reaction to a cold preparation. He died of disseminated intravascular coagulation and severe intestinal bleeding due to systemic cytomegalovirus reactivation following the development of severe eruptions with marked eosinophilia due to drug hypersensitivity to taurine and ursodeoxycholate preparations. The close interaction between viral infection or reactivation and drug hypersensitivity was considered as a pathophysiology in this case, which emphasizes the need for further study of the immunological mechanism of the interaction.

Latency and reactivation of human cytomegalovirus

Human cytomegalovirus (HCMV) persists as a subclinical, lifelong infection in the normal human host, maintained at least in part by its carriage in the absence of detectable infectious virus--the hallmark of latent infection. Reactivation from latency in immunocompromised individuals, in contrast, often results in serious disease. Latency and reactivation are defining characteristics of the herpesviruses and key to understanding their biology. However, the precise cellular sites in which HCMV is carried and the mechanisms regulating its latency and reactivation during natural infection remain poorly understood. This review will detail our current knowledge of where HCMV is carried in healthy individuals, which viral genes are expressed upon carriage of the virus and what effect this has on cellular gene expression. It will also address the accumulating evidence suggesting that reactivation of HCMV from latency appears to be linked intrinsically to the differentiation status of the myeloid cell, and how the cellular mechanisms that normally control host gene expression play a critical role in the differential regulation of viral gene expression during latency and reactivation.

Atherogenic progression of carotid stenosis associates selectively with monocyte fraction in circulating leukocytes

Humoral biomarkers of inflammation appear to correlate with future cardiovascular events warranting investigation of more specific associations between phenotypic subclasses of circulating cellular immunity and atherogenic progression of carotid stenosis. Retrospective study of carotid stenosis progression based on archived serial carotid duplex ultrasonography examinations in 100 patients. Predictors of atherogenic progression of carotid stenosis were sought using univariate and multivariate analysis of age, gender, hypertension, diabetes mellitus, smoking, peripheral blood leukocyte count and leukocyte differential profile, platelets, diastolic and systolic and mean arterial blood pressure, pulse pressure, creatinine, glucose, total-, HDL-, and LDL-cholesterol, triglycerides, and body mass index. Atherogenic progression of carotid stenosis was limited to patients with carotid stenosis at baseline (41/100) and exhibited a sporadic episodic temporal course. Univariate predictors of stenosis progression were diabetes mellitus, smoking, percent monocytes, and absolute monocyte count. Logistic regression demonstrated that monocytes as a percentage of circulating leukocytes [odds ratio (OR) 1.25, 95% confidence interval (CI) 1.06-1.47, P=0.0093] and smoking (OR 7.09, 95% CI 1.97-25.43, P=0.0027) were independently associated with atherogenic epochs. A selective association between the fraction of monocytes among leukocytes in peripheral blood and atherogenic progression of carotid stenosis is described.

In vitro infection of megakaryocytes and their precursors by human cytomegalovirus

Apart from congenital human cytomegalovirus (HCMV) infection, manifest HCMV disease occurs primarily in immunocompromised patients. In allogeneic bone marrow transplantation, HCMV is frequently associated with graft failure and cytopenias involving all hematopoietic lineages, but thrombocytopenia is the most commonly reported hematologic complication. The authors hypothesized that megakaryocytes (MK) may be a specific target for HCMV. Although the susceptibility of immature hematopoietic progenitors cells to HCMV has been established, a productive viral life cycle has only been linked to myelomonocytic maturation. The authors investigated whether HCMV can also infect MK and impair their function. They demonstrated that HCMV did not affect the thrombopoietin (TPO)-driven proliferation of CD34+ cells until MK maturation occurred. MK challenged with HCMV showed a 50% more rapid loss of viability than mock-infected cells. MK and their early precursors were clearly shown to be susceptible to HCMV in vitro, as evidenced by the presence of HCMV in magnetic column-purified CD42+ MK and 2-color fluorescent staining with antibodies directed against CD42a and HCMV pp65 antigen. These findings were confirmed by the infection of MK with a laboratory strain of HCMV containing the β-galactosidase (β-gal) gene. Using chromogenic β-gal substrates, HCMV was detected during MK differentiation of infected CD34+ cells and after infection of fully differentiated MK. Production of infectious virus was observed in cultures infected MK, suggesting that HCMV can complete its life cycle. These results demonstrate that MK are susceptible to HCMV infection and that direct infection of these cells in vivo may contribute to the thrombocytopenia observed in patients infected with HCMV.

Human cytomegalovirus infection of human hematopoietic progenitor cells

For a number of years it has been well established that human cytomegalovirus (HCMV) can be transmitted by the cellular components of blood. HCMV is also associated with a number of hematologic disorders. Although HCMV was thought to be present in blood cells in a latent or persistent form, it was not known how the virus was maintained and which cells were the carriers of HCMV. In addition to peripheral blood cells, there has been clinical evidence that HCMV may be associated with specific disorders of the hematopoietic system. Recently, a number of advances in cell and molecular biology have helped to develop a better understanding of the relationship between HCMV and the hematopoietic system. The application of the polymerase chain reaction (PCR) to the study of HCMV infection has revealed that the virus was present in mononuclear cells with only limited transcription of its genome. Studies conducted in our laboratory have demonstrated that both CD34+ progenitor cells and monocytes could be infected with HCMV and virus recovered when the cells were allowed to terminally differentiate. Subsequently, these results have been confirmed in vivo: HCMV DNA and limited RNA transcripts could be detected in in vivo infected hematopoietic progenitor cells and HCMV has been rescued from macrophages derived through in vitro differentiation of monocytes from normal seropositive blood donors. Although our understanding of the relationship between HCMV and the hematopoietic system has been advanced, the mechanisms by which the virus can be maintained in a latent state and how it is reactivated is still unclear. Furthermore, it remains to be determined what HCMV-mediated effect is responsible for the inhibition of hematopoiesis following an in vitro infection and its significance in vivo.