Persistent Human Cytomegalovirus Infection Research Articles

HCMV infection and IFITM3 rs12252 are associated with Rasmussen's encephalitis disease progression.

ObjectiveRasmussen’s encephalitis (RE) is a rare and severe progressive epileptic syndrome with unknown etiology. Infection by viruses such as human cytomegalovirus (HCMV) has been hypothesized to be a potential trigger for RE. Interferon‐induced transmembrane protein‐3 (IFITM3) single‐nucleotide polymorphism (SNP) rs12252 is associated with the severity of viral infection disease. This study aimed to address the possibility that HCMV infection and IFITM3 rs12252 might be associated with RE disease progression.MethodsThe expression of HCMV and IFITM3 was detected with immunohistochemical staining, in situ hybridization and immunofluorescence double staining. The genotype of IFITM3 rs12252 was detected using the Sanger sequencing method. A genetic association analysis was carried out for this SNP and HCMV antigen expression. The relationship between this SNP and the clinical characteristics of these patients was further analyzed. In in vitro study, HCMV replication in SH‐SY5Y cells with overexpressed IFITM3 variant was detected by immunofluorescence and real‐time RT‐PCR.ResultsElevated expression of HCMV and IFITM3 was observed in the brain tissue of RE patients. Moreover, the IFITM3 polymorphism rs12252‐C was found to associate with HCMV high detection and rapid disease progression in RE patients with the IFITM3 rs12252‐CC genotype. In vitro study showed the overexpressed IFITM3 variant was associated with HCMV high infection level.ConclusionThese results suggest that the IFITM3 rs12252‐C is associated with the disease progression of RE patients via facilitating persistent HCMV infection in brain tissue and provides new insight into understanding the pathogenesis of RE.

Persistent HCMV infection of a glioblastoma cell line contributes to the development of resistance to temozolomide

Glioblastoma multiforme (GBM) is the most aggressive form of primary human gliomas. While chemotherapy using the DNA alkylating agent temozolomide (TMZ) is a first line treatment for GBMs, the development of resistance to TMZ is a common limitation to successful treatment. Human Cytomegalovirus (HCMV) is a ubiquitous β-herpesvirus that establishes a lifelong infection latent infection in host haematopoetic cells, where lytic replication of the virus is silenced. HCMV can also establish a persistent infection in hosts, where low levels of virus are lytically produced. Furthermore, multiple studies have identified HCMV DNA and/or proteins in human GBM samples, and have shown that acute infection with HCMV confers a glioblastoma stem cell (GSC) phenotype, further supporting an oncomodulatory role for HCMV in GBM progression and severity. In this current study, we examined the long-term effects of HCMV persistence to cell viability, cell proliferation, and the development of TMZ resistance over time using a glioblastoma cell line known as LN-229. Persistent HCMV infections were established and maintained in this cell line for 30 weeks without the addition of new virus. Here, we report that HCMV persistence in this cell line resulted in increased cell viability, increased cell proliferation, and a marked resistance to the DNA alkylating agent, TMZ, over time, suggesting that low levels of lytically replicating HCMV could contribute to tumor progression in GBM.

First-line Therapy With Donor-derived Human Cytomegalovirus (HCMV)-specific T Cells Reduces Persistent HCMV Infection by Promoting Antiviral Immunity After Allogenic Stem Cell Transplantation.

Human cytomegalovirus (HCMV) infection, especially persistent HCMV infection, is an important cause of morbidity and mortality after allogenic stem cell transplantation (allo-SCT). Antiviral agents remain the first-line therapy but are limited by side effects and acquired resistance. We evaluated the safety and efficacy of donor-derived HCMV-specific cytotoxic T cells (CTLs) as a first-line therapy for HCMV infection after allo-SCT and investigated the underlying mechanisms. In humanized HCMV-infected mice, first-line therapy with CTLs effectively combated systemic HCMV infection by promoting the restoration of graft-derived endogenous HCMV-specific immunity in vivo. In a clinical trial, compared with the pair-matched, high-risk control cohort, first-line therapy with CTLs significantly reduced the rate of persistent (2.9% vs 20.0%, P = .018) and late (5.7% vs 20.0%, P = .01) HCMV infection and cumulative incidence of persistent HCMV infection (hazard ratio [HR], 0.13; 95% confidence interval [CI], 0.10-0.82; P = .02), lowered 1-year treatment-related mortality (HR, 0.15. 95% CI, 0.11-0.90. P = .03), and improved 1-year overall survival (HR, 6.35; 95% CI, 1.05-9.00; P = .04). Moreover, first-line therapy with CTLs promoted the quantitative and functional recovery of CTLs in patients, which was associated with HCMV clearance. We provide robust support for the benefits of CTLs combined with antiviral drugs as a first-line therapy for treating HCMV infection and suggest that adoptively infused CTLs may stimulate the recovery of endogenous HCMV-specific immunity. NCT02985775.

First-Line Therapy with Donor Derived HCMV-Specific T Cells Reduce Persistent HCMV Infection after Allogenic Stem Cell Transplantation

Background: Human cytomegalovirus (HCMV) infection, especially persistent HCMV infection, is an important cause of morbidity and mortality after allogenic stem cell transplantation (allo-SCT). Antiviral agents remain the mainstay of treatment and are recommend as the first-line therapy for HCMV. However, drugs are associated with significant toxicity, and their efficacy is limited in the absence of cell-mediated immunity. In recent years, adoptive immunotherapy with HCMV-specific T cells (CTLs) has been developed as an alternative option for HCMV, and data from previous studies have indicated that infusion of CTLs at early-stage of HCMV infection may have better benefits compared to salavage therapy. However, because CTLs remains time consuming and cost-intensive, so far there have no reports of first-line therapy with CTLs for HCMV infection, and the mechanisms driving the sustained antiviral immunity induced by adoptive T cells transfer remain undetermined. Our previous study had demonstrated that patients with acute graft-versus-host disease (aGVHD) were at high risk to develop persistent HCMV infection. Therefore, in the current study, we selected patients who developed aGVHD before HCMV reactivated and started CTLs generation in advance. This risk-stratified measure successfully selected patients who had high risk resisting to conventional anti-HCMV therapy , and spared low risk patients as well, making it feasible and financially viable to use CTLs as a first-line therapy.Aims: To provide robust support for the safety and efficacy of CTLs given as a first-line therapy for HCMV infection after allo-SCT, and gain some insight into the underlying mechanisms.Methods: Firstly, using humanized HCMV infected mice model, we explored where the adoptive transferred CTLs cells trafficked, evaluated the antiviral efficacy of CTLs and investigated the recovery of HCMV-specific immunity after T cell transfer. Secondly, we conducted a prospective clinical trial enrolled 35 allo-SCT patients who diagnosed with acute GVHD and had high risk developing persistent HCMV infection, intervened with antiviral agents combined with CTLs as first-line therapy and evaluated the long-term safety and durability of antiviral responses. As controls, we selected a cohort of 70 high-risk patients as well as another cohort of 70 low-risk patients who only received antiviral agents as first-line therapy without CTLs. We also evaluated the immune response after infusion and analyzed the association between immune recovery and HCMV clearance.Results: i) In humanized HCMV infection mice, adoptive infused CTLs had the ability to homing to organs, and effectively combated systemic HCMV infection by promoting the restoring of stem cell derived endogenous HCMV-specific immunity. ii) In clinical trial, first-line therapy with CTLs significantly reduced the rate (2.86% vs. 20.00%, P=0.018) and the cumulative incidence (HR=7.60, 95%CI=1.22-10.15, P=0.020) of persistent HCMV infection, and showed a lower one-year treatment related mortality (TRM) (HR=6.83, 95%CI=1.16-8.90, P=0.030) and a better one-year overall survival (OS) (HR=6.35, 95%CI=1.05-9.00, P=0.040) compared to high-risk control cohort. The cumulative incidence of persistent HCMV infection, one-year TRM and OS in CTL cohort were comparable to those in low-risk control cohort. Moreover, first-line therapy with CTLs promoted the quantitative and functional recovery of CTLs in patients, which was associated with HCMV clearance.Conclusion: In this study, we firstly demonstrated the safety and efficacy of CTLs administration as a first-line therapy for HCMV infection in humanized HCMV infection mice, and in a large clinical cohort study. The data provided robust support for the benefits of donor derived CTLs in treating HCMV infection as a first-line therapy, and suggested that infused CTLs might probably stimulate the recovery of donor derived HCMV-specific immunity. This trial was registered at www.clinicaltrials.gov as #NCT02985775. DisclosuresNo relevant conflicts of interest to declare.

Anti-cytomegalovirus IgG antibody titer is positively associated with advanced T cell differentiation and coronary artery disease in end-stage renal disease

BackgroundAccumulating evidence indicates that persistent human cytomegalovirus (HCMV) infection is associated with several health-related adverse outcomes including atherosclerosis and premature mortality in individuals with normal renal function. Patients with end-stage renal disease (ESRD) exhibit impaired immune function and thus may face higher risk of HCMV-related adverse outcomes. Whether the level of anti-HCMV immune response may be associated with the prognosis of hemodialysis patients is unknown.ResultsAmong 412 of the immunity in ESRD study (iESRD study) participants, 408 were HCMV seropositive and were analyzed. Compared to 57 healthy individuals, ESRD patients had higher levels of anti-HCMV IgG. In a multivariate-adjusted logistic regression model, the log level of anti-HCMV IgG was independently associated with prevalent coronary artery disease (OR = 1.93, 95% CI = 1.2~ 3.2, p = 0.01) after adjusting for age, sex, hemoglobin, diabetes, calcium phosphate product and high sensitivity C-reactive protein. Levels of anti-HCMV IgG also positively correlated with both the percentage and absolute number of terminally differentiated CD8+ and CD4+ CD45RA+ CCR7- TEMRA cells, indicating that immunosenescence may participate in the development of coronary artery disease.ConclusionThis is the first study showing that the magnitude of anti-HCMV humoral immune response positively correlates with T cell immunosenescence and coronary artery disease in ESRD patients. The impact of persistent HCMV infection should be further investigated in this special patient population.

Tissue reservoirs of antiviral T cell immunity in persistent human CMV infection.

T cell responses to viruses are initiated and maintained in tissue sites; however, knowledge of human antiviral T cells is largely derived from blood. Cytomegalovirus (CMV) persists in most humans, requires T cell immunity to control, yet tissue immune responses remain undefined. Here, we investigated human CMV-specific T cells, virus persistence and CMV-associated T cell homeostasis in blood, lymphoid, mucosal and secretory tissues of 44 CMV seropositive and 28 seronegative donors. CMV-specific T cells were maintained in distinct distribution patterns, highest in blood, bone marrow (BM), or lymph nodes (LN), with the frequency and function in blood distinct from tissues. CMV genomes were detected predominantly in lung and also in spleen, BM, blood and LN. High frequencies of activated CMV-specific T cells were found in blood and BM samples with low virus detection, whereas in lung, CMV-specific T cells were present along with detectable virus. In LNs, CMV-specific T cells exhibited quiescent phenotypes independent of virus. Overall, T cell differentiation was enhanced in sites of viral persistence with age. Together, our results suggest tissue T cell reservoirs for CMV control shaped by both viral and tissue-intrinsic factors, with global effects on homeostasis of tissue T cells over the lifespan.

Sociodemographic factors associated with IgG and IgM seroprevalence for human cytomegalovirus infection in adult populations of Pakistan: a seroprevalence survey.

BackgroundThe seroprevalence of human cytomegalovirus (HCMV) infection ranges from 30 to 90 % in developed countries. Reliable estimates of HCMV seroprevalence are not available for Pakistan. This study determined the seroprevalence and sociodemographic factors associated with HCMV infection in adult populations of Karachi, Pakistan.MethodsA seroprevalence survey was conducted on 1000 adults, including residents of two semi-urban communities, and visitors to a government and a private hospital. Questionnaire-based interviews were conducted. Sera were analysed for HCMV-specific IgG and IgM. Chi-square or Fisher’s exact test was used for comparing sociodemographic variables against seropositivity of HCMV-IgG or IgM. Multiple logistic regression modeling was performed for IgG seroprevalence and adjusted odds ratios were computed.ResultsThe seroprevalence of HCMV-IgG and IgM was 93.2 and 4.3 % respectively. 95.3 % of individuals who were IgM seropositive were also seropositive for IgG. Around 6 % (15/250) of women of childbearing age remained uninfected and were therefore susceptible to primary infection. HCMV-IgG seroprevalence was associated with being female (p = 0.001), increasing age (p = 0.002) and crowding index (p = 0.003) and also with lower levels of both education (p < 0.001) and income (p = 0.008). Seroprevalence also differed significantly by marital status (p = 0.008) and sampling location (p < 0.001). A logistic regression model for HCMV-IgG seroprevalence showed associations with being female (OR = 1.89; 95 % CI: 1.10–3.25), increasing age (OR = 3.95; 95 % CI: 1.79–8.71) and decreasing income (OR = 0.72; 95 % CI: 0.54–0.96). A strong association was observed between increased seroprevalence of HCMV-IgM and decreasing household size (p = 0.008).ConclusionsSeroprevalence of HCMV is very high in Pakistan, although 6 % of women of childbearing age remain at risk of primary infection. The IgM seropositivity observed in some individuals living in small household size (1–3 individuals) with persistent HCMV infection could have resulted from a recurrent HCMV infection. Future longitudinal research in pregnant women and neonates is required to study the trends in HCMV seroprevalence over time in Pakistan for the development of a potential HCMV prevention and vaccination programme.

Human Cytomegalovirus Promotes Survival of Infected Monocytes via a Distinct Temporal Regulation of Cellular Bcl-2 Family Proteins.

Monocytes play a key role in the hematogenous dissemination of human cytomegalovirus (HCMV) to target organ systems. To infect monocytes and reprogram them to deliver infectious virus, HCMV must overcome biological obstacles, including the short life span of monocytes and their antiviral proapoptotic response to infection. We have shown that virally induced upregulation of cellular Mcl-1 promotes early survival of HCMV-infected monocytes, allowing cells to overcome an early apoptotic checkpoint at around 48 h postinfection (hpi). Here, we demonstrate an HCMV-dependent shift from Mcl-1 as the primary antiapoptotic player to the related protein, Bcl-2, later during infection. Bcl-2 was upregulated in HCMV-infected monocytes beginning at 48 hpi. Treatment with the Bcl-2 antagonist ABT-199 only reduced the prosurvival effects of HCMV in target monocytes beginning at 48 hpi, suggesting that Mcl-1 controls survival prior to 48 hpi, while Bcl-2 promotes survival after 48 hpi. Although Bcl-2 was upregulated following viral binding/signaling through cellular integrins (compared to Mcl-1, which is upregulated through binding/activation of epidermal growth factor receptor [EGFR]), it functioned similarly to Mcl-1, adopting the early role of Mcl-1 in preventing caspase-3 cleavage/activation. This distinct, HCMV-induced shift from Mcl-1 to Bcl-2 occurs in response to a cellular upregulation of proapoptotic Bax, as small interfering RNA (siRNA)-mediated knockdown of Bax reduced the upregulation of Bcl-2 in infected monocytes and rescued the cells from the apoptotic effects of Bcl-2 inhibition. Our data demonstrate a distinct survival strategy whereby HCMV induces a biphasic regulation of cellular Bcl-2 proteins to promote host cell survival, leading to viral dissemination and the establishment of persistent HCMV infection. Hematogenous dissemination of HCMV via infected monocytes is a crucial component of the viral survival strategy and is required for the establishment of persistent infection and for viral spread to additional hosts. Our system of infected primary human blood monocytes provides us with an opportunity to answer specific questions about viral spread and persistence in in vivo-relevant myeloid cells that cannot be addressed with the more traditionally used replication-permissive cells. Our goal in examining the mechanisms whereby HCMV reprograms infected monocytes to promote viral dissemination is to uncover new targets for therapeutic intervention that would disrupt key viral survival and persistence strategies. Because of this important role in maintaining survival of HCMV-infected monocytes, our new data on the role of Bcl-2 regulation during viral infection represents a promising molecular target for mitigating viral spread and persistence.

TTV DNA plasma load and its association with age, gender, and HCMV IgG serostatus in healthy adults

Understanding immunosenescence and changes in antimicrobial immune response with age is of high importance. The association of immunosenescence with gender and persistent infection with human cytomegalovirus (HCMV) is a matter of intensive research. We determined whether replication of another persistent and highly prevalent virus, Torque teno virus (TTV), is related to age, gender, and HCMV IgG serostatus of the host. TTV DNA load in plasma was assessed by real-time PCR in 313 healthy persons: 20-30years old (young, n = 104), 50-60years old (middle-aged, n = 101), or >80years old (elderly, n = 108). TTV DNA loads were further associated with age-groups, gender, and HCMV IgG serostatus. TTV load was significantly higher in the elderly compared to the young group (p < 0.001; Tukey's honest significant difference (HSD)), and the higher TTV DNA levels over age were found to be gender-specific (p = 0.002; ANOVA), with young women showing the lowest TTV load compared to young men (p = 0.009, t test) and compared to the other female age-groups (middle-aged p = 0.005; elderly p < 0.001; Tukey's HSD). TTV load of HCMV IgG-seropositive persons was significantly higher than that of the HCMV IgG seronegative in the young (p = 0.005; t test) and middle-aged (p = 0.016; t test) groups. These results indicate that the host's immune control of TTV replication decreases with age and is gender-specific. Persistent HCMV infection is significantly related to higher TTV DNA loads, especially at a younger age. Therefore, the influence of gender and HCMV on immunosenescence earlier in life should be further explored.

Association of HCMV specific IgG subclass antibody levels with gender and age

Infection with human cytomegalovirus (HCMV), a ubiquitously distributed herpesvirus, has been associated with human immune system aging. Especially total HCMV specific IgG antibody (AB) titres have been correlated with human frailty and mortality. The aim of this study was to further assess to which extent HCMV specific subclass AB titres differ between individuals and whether this is associated with age and gender.ELISA tests detecting HCMV specific IgG subclass 1 and 3 ABs, the main subclass ABs directed against HCMV, were developed. Using these ELISAs, 145 (73 female and 72 male) age-matched patients, aged 17 to 87years, were tested.The results showed that the IgG1 and 3 subclass distribution was highly variable among individuals, and that female persons had significantly higher IgG3 titres than age-matched male persons (p=0.0073). A correlation of the IgG3 subclass titres with age was found in female persons (Spearman r=0.305, p=0.0088).Thus the total HCMV specific IgG level appears to consist of a variable and gender associated distribution of IgG subclass ABs developed against persistent HCMV infection. The analysis of IgG subclass titres therefore could further be used to refine previously established clinical associations of aging with total HCMV specific IgG AB titres.

Association of Atherosclerosis With Expression of the LILRB1 Receptor By Human NK and T-Cells Supports the Infectious Burden Hypothesis

The contribution of human cytomegalovirus (HCMV) to vascular disease may depend on features of the immune response not reflected by the detection of specific antibodies. Persistent HCMV infection in healthy blood donors has been associated with changes in the distribution of NK cell receptors (NKR). The putative relationship among HCMV infection, NKR distribution, subclinical atherosclerosis, and coronary heart disease was assessed. NKR expression was compared in acute myocardial infarction (AMI) patients (n=70) and a population-based control sample (n=209). The relationship between NKR expression and carotid intima-media thickness (CIMT) in controls (n=149) was also studied. HCMV infection was associated with higher proportions of NKG2C+ and LILRB1+ NK and T-cells. In contrast, only LILRB1+ NK and CD56+ T-cells were found to be increased in AMI patients, independent of age, sex, conventional vascular risk factors, and HCMV seropositivity. Remarkably, LILRB1 expression in NK and T-cells significantly correlated with CIMT in controls. The association of overt and subclinical atherosclerotic disease with LILRB1+ NK and T-cells likely reflects a relationship between the immune challenge by infections and cardiovascular disease risk, without attributing a dominant role for HCMV. Our findings may lead to the identification of novel biomarkers of vascular disease.

Detection of Human Cytomegalovirus in Amniotic Fluid and Villous Tissues

Human cytomegalovirus (HCMV) is the most common cause of intrauterine infection. Endothelial and/or epithelial cells in uterine tissue are major sites of latent or persistent HCMV infection in women, and the uterus may play an important role in viral dissemination. To elucidate the pathomechanisms of intrauterine infection by HCMV, we examined the presence of the HCMV genome, antigen and infectious virion in amniotic fluid and villous tissues. The isolation of infectious HCMV in amniotic fluid was detected using the MRC-5 human embryonic fibroblast cell line. The HCMV genome was detected by polymerase chain reaction. Expression and distribution of HCMV antigens and mRNA transcripts in villous tissues were examined by immunostaining using primary antibodies specific for an immediate early nuclear antigen and for a late cytoplasmic antigen of HCMV, and in situ hybridization using an antisense probe specific for the phosphoprotein 71 (pp71) region of HCMV, respectively. The HCMV genome was detected in 46 (26%) out of 176 amniotic fluid specimens. Moreover, the infectious virus was isolated in nine of these specimens (5.1%), with viral immediate early and late antigens being detected in the cultured cells of amniotic fluid. In the villous tissues of all examined cases (7/7), viral mRNA and antigen were detected, and 48% of the pregnant women whose cervical smears were positive for the HCMV genome by polymerase chain reaction delivered babies with positive urinary samples. These results suggest that transplacental transmission of HCMV to the fetus occurs more frequently than has been previously reported. Further studies are necessary to precisely clarify the mechanisms of intrauterine HCMV infection.

Impact of persistent cytomegalovirus infection on human neuroblastoma cell gene expression

In a model of human neuroblastoma (NB) cell lines persistently infected with human cytomegalovirus (HCMV) we previously showed that persistent HCMV infection is associated with an increased malignant phenotype, enhanced drug resistance, and invasive properties. To gain insights into the mechanisms of increased malignancy we analyzed the global changes in cellular gene expression induced by persistent HCMV infection of human neuroblastoma cells by use of high-density oligonucleotide microarrays (HG-U133A, Affymetrix) and RT-PCR. Comparing the gene expression of different NB cell lines with persistently infected cell sub-lines revealed 11 host cell genes regulated in a similar manner throughout all infected samples. Nine of these 11 genes may contribute to the previously observed changes in malignant phenotype of persistently HCMV infected NB cells by influencing invasive growth, apoptosis, angiogenesis, and proliferation. Thus, this work provides the basis for further functional studies.

Predictive value of maternal-IgG avidity for congenital human cytomegalovirus infection.

Human cytomegalovirus (HCMV) is now the most common cause of viral intrauterine infection. Fetal damage is mostly linked to maternal primary infection. It is therefore important to differentiate primary from recurrent or persistent HCMV infection in pregnant females. For this purpose, IgM tests are not reliable enough and the measurement of the IgG avidity appears to be presently the best method. To evaluate the performance of the measurement of HCMV-IgG avidity by a 8 M urea denaturation assay in predicting congenital infection in the offspring. Seventy-eight women were included in this study on the basis of a HCMV IgM positive or equivocal result on a first serum during pregnancy, but without a documented seroconversion history. The IgG avidity was measured and correlated with the outcome of the pregnancy. In eight cases of HCMV in utero infection the maternal HCMV-IgG avidity index was below 50%. One case of HCMV in utero infection was observed despite a high avidity index during the second trimester of the pregnancy. High or intermediate HCMV-IgG avidity indexes during the first trimester of pregnancy were not associated with a congenital infection. Even in the presence of an IgM positive result, an HCMV IgG avidity index above 65% on a serum obtained during the first trimester of pregnancy could reasonably be considered as a good indicator of past HCMV infection. In these conditions invasive prenatal diagnosis is not necessary.

Modulatory effects of human cytomegalovirus infection on malignant properties of cancer cells.

Although there is no definitive evidence of the association of human cytomegalovirus (HCMV) infection with human cancers, the oncogenic potential of HCMV has been well established by in vitro studies demonstrating the ability of UV-irradiated or infectious virus to transform a variety of cells. After prolonged passaging the transformed cell type was maintained while HCMV DNA sequences were no more detectable. Three morphological transforming regions (mtr) of HCMV have been identified. The effects of HCMV on cellular functions which may be associated with the malignant phenotype include the expression of oncogenes and transcriptional activation of growth factors and interleukin synthesis. In infected cells, HCMV induces cytoskeletal alterations and changes in expression of cell surface receptors for extracellular matrix proteins which could result in increased motility and dissemination of cancer cells. Several human neuroblastoma cell lines undergo maturation in different neural crest derived cell types upon treatment with oncogenic potential agents, i.e. retinoic acid. The persistent HCMV infection of neuroblastoma cells (> 1 year) is accompanied by the increased expression of oncoproteins (i.e. N-myc) and decreased expression of tyrosine hydroxylase and dopamine-beta-hydroxylase. The activation of the cellular metabolism is due to HCMV binding to cellular receptors (prior to virus gene expression) and to the activity of HCMV immediate early (IE) gene products. IE proteins act directly as transcriptional activators or their activity is mediated by a variety of cellular transcription factors. HCMV infection may result in activation of promoters of cellular genes coding for cytokines, replication enzymes, proto-oncogenes and viral promoters. Recently it has been demonstrated that HCMV IE proteins block apoptosis probably by suppressing the ability of the antioncogene p53 to activate a reporter gene. The interactions of HCMV with tumor suppressor proteins such as p53 or retinoblastoma (pRb) susceptibility protein are reminiscent of those mediated by the oncoproteins of DNA tumor viruses. The acquisition of a fully malignant phenotype by normal cells is thought to require several mutations in a number of cellular genes. In this connection, HCMV may play the role of a nonobligate either direct or indirect cofactor for tumor genesis, e.g. by blocking apoptosis, which may be an essential requirement for tumor progression. Due to the stimulation of growth factors and/or inhibition of antioncogenes by its gene products, HCMV may modulate the malignant potential for tumor cells.

Latent infection and reactivation of human cytomegalovirus

Human cytomegalovirus (HCMV) is the most common cause of congenital and perinatal infections throughout the world. Primary infection with HCMV usually follows a benign course, but the virus remains latent or persistent in the host cell thereafter. Under immunosuppressive conditions, latent or persistent infection can be reactivated to produce a wide variety of clinical manifestations. Understanding the epidemiology of HCMV infection is a key element in development of strategies for prevention of infection. Definition of sites and mechanisms involved in the maintenance of latent or persistent HCMV infection and reactivation is also essential for a thorough understanding of the pathogenesis of HCMV infection. This mini review focuses on recent advances in the study of persistent infection and reactivation of HCMV. Although the actual sites of latency or persistence of HCMV infections are still controversial, peripheral blood mononuclear cells (PBMC) and endothelial cells appear to be the principal site of infection. Persistent infections caused by HCMV could be augmented by a decrease in major histocompatibility complex (MHC) expression as well as by virus-mediated immune dysfunction. It is also likely that specific cellular interactions as well as production of several cytokines are necessary for the reactivation of HCMV.

Immunoaffinity purification of a 72K early antigen of human cytomegalovirus: analysis of humoral and cell-mediated immunity to the purified polypeptide.

An early antigen of human cytomegalovirus (HCMV) was purified from infected cells as a 72K polypeptide by immunoaffinity chromatography using a monoclonal antibody. It was located in both nucleus and cytoplasm, and was non-glycosylated and undetectable on the surface of infected cells. Known seropositive subjects had antibody against the purified protein and it elicited proliferative T cell responses in 10 of 16 subjects. Five of 14 T cell lines established in response to the purified protein were predominantly CD8+ and of these two showed major histocompatibility complex-restricted cytotoxicity against HCMV-infected cells. This provides further evidence that antigens expressed at early times may be targets for the immune response during persistent HCMV infection.