KI and WU polyomaviruses and CD4+ cell counts in HIV-1-infected patients, Italy

Beyond Cytomegalovirus and Epstein-Barr Virus: a Review of Viruses Composing the Blood Virome of Solid Organ Transplant and Hematopoietic Stem Cell Transplant Recipients

Viral primary infections and reactivations are common complications in patients after solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT) and are associated with high morbidity and mortality. Among these patients, viral infections are frequently associated with viremia. Beyond the usual well-known viruses that are part of the routine clinical management of transplant recipients, numerous other viral signatures or genomes can be identified in the blood of these patients. The identification of novel viral species and variants by metagenomic next-generation sequencing has opened up a new field of investigation and new paradigms. Thus, there is a need to thoroughly describe the state of knowledge in this field with a review of all viral infections that should be scrutinized in high-risk populations. Here, we review the eukaryotic DNA and RNA viruses identified in blood, plasma, or serum samples of pediatric and adult SOT/HSCT recipients and the prevalence of their detection, with a particular focus on recently identified viruses and those for which their potential association with disease remains to be investigated, such as members of the Polyomaviridae, Anelloviridae, Flaviviridae, and Astroviridae families. Current knowledge of the clinical significance of these viral infections with associated viremia among transplant recipients is also discussed. To ensure a comprehensive description in these two populations, individuals described as healthy (mostly blood donors) are considered for comparative purposes. The list of viruses that should be on the clinicians' radar is certainly incomplete and will expand, but the challenge is to identify those of possible clinical significance.

Associations of Viral Seroreactivity with AIDS-Related Non-Hodgkin Lymphoma

Infection with human immunodeficiency virus (HIV) is associated with substantially increased incidence of non-Hodgkin lymphoma (NHL). This risk may be driven, in part, by reduced immune control over viral infections in the setting of acquired immunodeficiency syndrome (AIDS), although the lymphomagenic mechanisms are not yet established. We used bead-based multiplex assays to measure antibody seroreactivity to 32 viral antigens representing 22 different viral infections (human herpesviruses 1-8, hepatitis B and C virus, human T-lymphotropic virus type-1, and human polyomaviruses) in two prospective HIV cohorts. Incident (n = 28) and prevalent (n = 38) AIDS-related NHL cases were matched by age, sex, race, and CD4 count to 67 HIV-positive control individuals without AIDS-NHL. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations of AIDS-NHL with the number of different viruses to which an individual was seropositive and seroreactivity to individual antigens. Seropositivity to an increasing number of viruses was inversely associated with AIDS-NHL (OR per virus = 0.84, 95% CI = 0.72-0.98). Seroreactivity to herpes simplex virus 2 2mgG unique antigen (OR = 0.47; 95% CI = 0.23-0.97) and to WU polyomavirus viral capsid protein (OR = 0.26, 95% CI = 0.10-0.65) was significantly lower in AIDS-NHL cases compared to controls. In this evaluation of antibodies to multiple viruses, we observed an inverse association between seropositivity to a larger number of viruses and AIDS-NHL. While in need of further evaluation, our data raise the novel hypothesis that insufficient exposures or impaired humoral immune responses to viral infections may be associated with AIDS-related lymphomagenesis.

Prevalence of DNA of fourteen human polyomaviruses determined in blood donors

BACKGROUND

Human polyomaviruses (HPyVs), like herpesviruses, cause persistent infection in a large part of the population. In immunocompromised and elderly patients, PyVs cause severe diseases such as nephropathy (BK polyomavirus [BKPyV]), progressive multifocal leukoencephalopathy (JC polyomavirus [JCPyV]), and skin cancer (Merkel cell polyomavirus [MCPyV]). Like cytomegalovirus, donor‐derived PyV can cause disease in kidney transplant recipients. Possibly blood components transmit PyVs as well. To study this possibility, as a first step we determined the presence of PyV DNA in Dutch blood donations.

STUDY DESIGN AND METHODS

Blood donor serum samples (n = 1016) were analyzed for the presence of DNA of 14 HPyVs using HPyV species‐specific quantitative polymerase chain reaction (PCR) procedures. PCR‐positive samples were subjected to confirmation by sequencing. Individual PCR findings were compared with the previously reported PyV serostatus.

RESULTS

MC polyomavirus DNA was detected in 39 donors (3.8%), JCPyV and TS polyomavirus (TSPyV) DNA in five donors (both 0.5%), and HPyV9 DNA in four donors (0.4%). BKPyV, WU polyomavirus (WUPyV), HPyV6, MW polyomavirus (MWPyV), and LI polyomavirus (LIPyV) DNA was detected in one or two donors. Amplicon sequencing confirmed the expected product for BKPyV, JCPyV, WUPyV, MCPyV, HPyV6, TSPyV, MWPyV, HPyV9, and LIPyV. For JCPyV a significant association was observed between detection of viral DNA and the level of specific IgG antibodies.

CONCLUSION

In 5.4% of Dutch blood donors PyV DNA was detected, including DNA from pathogenic PyVs such as JCPyV. As a next step, the infectivity of PyV in donor blood and transmission via blood components to immunocompromised recipients should be investigated.

An overview on human polyomaviruses biology and related diseases

In recent years, the Polyomaviridae family grew rapidly, thanks to the introduction of high-throughput molecular techniques. To date, 14 polyomaviruses have been identified in humans but the association with human diseases has been established only for few of them. BKPyV has been associated with nephropathy in kidney transplant patients and hemorrhagic cystitis in hematopoietic stem cell transplant patients; JCPyV to progressive multifocal leukoencephalopathy, mainly in HIV-positive patients; Merkel cell polyomavirus to Merkel cell carcinoma; Trichodysplasia spinulosa polyomavirus to the rare skin disease Trichodysplasia spinulosa; human polyomaviruses 6 and 7 to pruritic rash. Immunocompromised patients are at risk of developing disease. Here, we summarized and discussed the scientific literature concerning the human polyomaviruses biology, seroprevalence and association with human diseases.

Characterization of the non-coding control region of polyomavirus KI isolated from nasopharyngeal samples from patients with respiratory symptoms or infection and from blood from healthy blood donors in Norway

Seroepidemiological studies showed that the human polyomavirus KI (KIPyV) is common in the human population, with age-specific seroprevalence ranging from 40-90 %. Genome epidemiological analyses demonstrated that KIPyV DNA is predominantly found in respiratory tract samples of immunocompromised individuals and children suffering from respiratory diseases, but viral sequences have also been detected in brain, tonsil, lymphoid tissue studies, plasma, blood and faeces. Little is known about the sequence variation in the non-coding control region of KIPyV variants residing in different sites of the human body and whether specific strains dominate in certain parts of the world. In this study, we sequenced the non-coding control region (NCCR) of naturally occurring KIPyV variants in nasopharyngeal samples from patients with respiratory symptoms or infection and in blood from healthy donors in Norway. In total 86 sequences were obtained, 44 of which were identical to the original isolated Stockholm 60 variant. The remaining NCCRs contained one or several mutations, none of them previously reported. The same mutations were detected in NCCRs amplified from blood and nasopharyngeal samples. Some patients had different variants in their specimens. Transient transfection studies in HEK293 cells with a luciferase reporter plasmid demonstrated that some single mutations had a significant effect on the relative early and late promoter strength compared with the Stockholm 60 promoter. The effect of the NCCR mutations on viral replication and possible virulence properties remains to be established.

High diversity of human polyomaviruses in environmental and clinical samples in Argentina: Detection of JC, BK, Merkel-cell, Malawi, and human 6 and 7 polyomaviruses

New human polyomaviruses have been recently described. The aim of this work was to detect and characterize human polyomaviruses circulating in Argentina by recovering viruses from environmental and sewage samples and evaluating their potential role as viral indicators of human waste contamination. Analysis was performed in a wider context including viruses from clinical samples from an immunocompromised population. River water and sewage samples were analyzed as a strategy to study the molecular epidemiology of viruses excreted by millions of people. Samples belonged to the Matanza-Riachuelo River (2005-2006: n=25 and 2012: n=20) and sewage from Buenos Aires city and suburbs (2011 and 2013: n=24). Viral detection was performed by PCR and the amplified viral genomes were characterized by phylogenetic analysis. Polyomaviruses were detected in 95.8% of sewage samples, identifying BKPyV (87.5%), JCPyV (83.3%), MCPyV (8.3%) and HPyV6 (8.3%). Besides, one sample collected in 2009 resulted positive for HPyV7. In 2005-2006, polyomaviruses were detected in 84.0% of river water samples, with the highest detection for MCPyV (52.0%), followed by BKPyV (44.0%), JCPyV (20.0%) and MWPyV (4.0%). In 2012, polyomaviruses were detected in 85.0% of river samples, finding JCPyV (85.0%), BKPyV (75.0%), MCPyV (25.0%) and HPyV6 (25.0%). Also, polyomaviruses, including JCPyV, BKPyV and MCPyV, were detected in 63.2% of urine samples from patients infected with HIV (n=19). Characterization indicated the coexistence of different genotypes and variants for each virus, particularly in sewage. MCPyV sequences (the only sequences from Argentina) formed a monophyletic group with the single sequence available for South America (French Guiana). The high level of detection and viral diversity found by environmental surveillance, which involved the characterization of viruses not previously described in South America, reinforces the usefulness of this approach to monitor viral contamination and describe the viral epidemiology in the general population.

The human polyomaviruses KI and WU: virological background and clinical implications

In 2007, two novel polyomaviruses KI and WU were uncovered in the respiratory secretions of children with acute respiratory symptoms. Seroepidemiological studies showed that infection by these viruses is widespread in the human population. Following these findings, different biological specimens and body compartments have been screened by real-time PCR in the attempt to establish a pathogenetic role for KI polyomavirus (KIPyV) and WU polyomavirus (WUPyV) in human diseases. Although both viruses have been found mainly in respiratory tract samples of immunocompromised patients, a clear causative link with the respiratory disease has not been established. Indeed, the lack of specific clinical or radiological findings, the frequent co-detection with other respiratory pathogens, the detection in subjects without signs or symptoms of respiratory disease, and the variability of the viral loads measured did not allow drawing a definitive conclusion. Prospective studies carried out on a large sample size including both immunocompromised and immunocompetent patients with and without respiratory symptoms are needed. Standardized quantitative real-time PCR methods, definition of a clear clinical cutoff value, timing in the collection of respiratory samples, are also crucial to understand the pathogenic role, if any, of KIPyV and WUPyV in human pathology.

Human polyomavirus reactivation: disease pathogenesis and treatment approaches

JC and BK polyomaviruses were discovered over 40 years ago and have become increasingly prevalent causes of morbidity and mortality in a variety of distinct, immunocompromised patient cohorts. The recent discoveries of eight new members of the Polyomaviridae family that are capable of infecting humans suggest that there are more to be discovered and raise the possibility that they may play a more significant role in human disease than previously understood. In spite of this, there remains a dearth of specific therapeutic options for human polyomavirus infections and an incomplete understanding of the relationship between the virus and the host immune system. This review summarises the human polyomaviruses with particular emphasis on pathogenesis in those directly implicated in disease aetiology and the therapeutic options available for treatment in the immunocompromised host.

The role of infections and coinfections with newly identified and emerging respiratory viruses in children

Acute respiratory infections are a major cause of morbidity in children both in developed and developing countries. A wide range of respiratory viruses, including respiratory syncytial virus (RSV), influenza A and B viruses, parainfluenza viruses (PIVs), adenovirus, rhinovirus (HRV), have repeatedly been detected in acute lower respiratory tract infections (LRTI) in children in the past decades. However, in the last ten years thanks to progress in molecular technologies, newly discovered viruses have been identified including human Metapneumovirus (hMPV), coronaviruses NL63 (HcoV-NL63) and HKU1 (HcoV-HKU1), human Bocavirus (HBoV), new enterovirus (HEV), parechovirus (HpeV) and rhinovirus (HRV) strains, polyomaviruses WU (WUPyV) and KI (KIPyV) and the pandemic H1N1v influenza A virus. These discoveries have heavily modified previous knowledge on respiratory infections mainly highlighting that pediatric population is exposed to a variety of viruses with similar seasonal patterns. In this context establishing a causal link between a newly identified virus and the disease as well as an association between mixed infections and an increase in disease severity can be challenging. This review will present an overview of newly recognized as well as the main emerging respiratory viruses and seek to focus on the their contribution to infection and co-infection in LRTIs in childhood.

Genome analysis of the new human polyomaviruses

Polyomaviridae is a growing family of naked, double-stranded DNA viruses that infect birds and mammals. The last few years, several new members infecting birds or primates have been discovered, including seven human polyomaviruses: KI, WU, Merkel cell polyomavirus, HPyV6, HPyV7, trichodysplasia spinulosa-associated polyomavirus, and HPyV9. In addition, DNA and antibodies against the monkey lymphotropic polyomavirus have been detected in humans, indicating that this virus can also infect man. However, little is known about the route of infection, transmission, cell tropism, and, with the exception of Merkel cell polyomavirus and trichodysplasia spinulosa-associated polyomavirus, the pathogenicity of these viruses. This review compares the genomes of these emerging human polyomaviruses with previously known polyomaviruses detected in man, reports mutations in different isolates, and predicts structural and functional properties of their viral proteins.

Prevalence of polyomaviruses and links with human diseases

The simian virus 40 and murine polyomaviruses were shown to be DNA tumor viruses in their natural hosts and/or heterologous experimental hosts in the mid-20th Century. The first two human polyomaviruses, the BK polyomavirus and JC polyomavirus, were discovered in 1971 and were shown to induce severe disease in immunocompromised patients, but their involvement in human cancers is still a matter for debate. The discovery of a polyomavirus associated with Merkel cell carcinoma (Merkel cell polyomavirus) in 2008 resulted in a renewed interest in the Polyomaviridae family, leading to the discovery of new human polyomaviruses. This review addresses the involvement of the nine human polyomaviruses and simian virus 40 in human diseases, with a particular focus on their prevalence and the humoral response directed against structural antigens in the general population and in subjects presenting specific diseases.

Infrequent detection of KI, WU and MC polyomaviruses in immunosuppressed individuals with or without progressive multifocal leukoencephalopathy

Conflicting prevalence of newly identified KI(KIPyV), WU(WUPyV) and Merkel Cell Carcinoma(MCPyV) polyomaviruses have been reported in progressive multifocal leukoencephalopathy(PML) patient samples, ranging from 0 to 14.3%. We analyzed the prevalence of these polyomaviruses in cerebrospinal fluid(CSF), peripheral blood mononuclear cells(PBMC), and bone marrow samples from PML patients, immunosuppressed individuals with or without HIV, and multiple sclerosis(MS) patients. Distinct PCR tests for KIPyV, WUPyV and MCPyV DNA performed in two independent laboratories detected low levels of MCPyV DNA only in 1/269 samples. The infrequent detections of these viruses in multiple samples from immunosuppressed individuals including those with PML suggest that their reactivation mechanisms may be different from that of JC polyomavirus (JCPyV) and that they do not play a role in the pathogenesis of PML.