GBV-C: State of the Art and Future Prospects

The plasma viral communities associate with clinical profiles in a large-scale haematological patients cohort

BACKGROUND

Haematological patients exhibit immune system abnormalities that make them susceptible to viral infections. Understanding the relationship between the virome in the blood plasma of haematological patients and their clinical characteristic is crucial for disease management. We aimed to explore the presence of viral pathogens and identify close associations between viral infections and various clinical features.

RESULTS

A total of 21 DNA viruses and 6 RNA viruses from 12 virus families were identified from 1383 patients. Patients with haematological diseases exhibited significantly higher diversity, prevalence, and co-detection rates of viral pathogens. During fever episodes, pathogen detection was notably higher, with Epstein-Barr virus (EBV) and Mucorales infections being the most probable culprits for fever symptoms in non-haematological patients. The detection rate of torque teno virus (TTV) significantly increases in haematological patients after transplantation and during primary lung infections. Additionally, TTV-positive patients demonstrate significantly higher absolute neutrophil counts, while C-reactive protein and procalcitonin levels are notably lower. Furthermore, TTV, cytomegalovirus, and parvovirus B19 (B19V) were found to be more prevalent in non-neutropenic patients, while non-viral pathogenic infections, such as Gram-negative bacteria and Mucorales, were more common in neutropenic patients. Pegivirus C (HPgV-C) infection often occurred post-transplantation, regardless of neutropenia. Additionally, some viruses such as TTV, B19V, EBV, and HPgV-C showed preferences for age and seasonal infections.

CONCLUSIONS

Analysis of the plasma virome revealed the susceptibility of haematological patients to plasma viral infections at specific disease stages, along with the occurrence of mixed infections with non-viral pathogens. Close associations were observed between the plasma virome and various clinical characteristics, as well as clinical detection parameters. Understanding plasma virome aids in auxiliary clinical diagnosis and treatment, enabling early prevention to reduce infection rates in patients and improve their quality of life. Video Abstract.

Interplay between HIV and Human Pegivirus (HPgV) Load in Co-Infected Patients: Insights from Prevalence and Genotype Analysis

Human pegivirus (HPgV) is transmitted through sexual or parenteral exposure and is common among patients receiving blood products. HPgV is associated with lower levels of human immunodeficiency virus (HIV) RNA and better survival among HIV-infected patients. This study aimed to investigate the prevalence of HPgV and determine its subtypes in HIV-infected individuals living in Istanbul, which has the highest rate of HIV infection in Türkiye. Total RNA extraction from plasma, cDNA synthesis, and nested PCR were performed for HPgV on plasma samples taken from 351 HIV-1-infected patients. The HPgV viral load was quantified on HPgV-positive samples. HPgV genotyping was performed by sequencing the corresponding amplicons. In the present study, the overall prevalence of HPgV RNA in HIV-infected patients was 27.3%. HPgV subtypes 1, 2a, and 2b were found, with subtype 2a being the most frequent (91.6%). Statistical analysis of HIV-1 viral load on HPgV viral load showed an opposing correlation between HIV-1 and HPgV loads. In conclusion, these data show that HPgV infection is common among HIV-positive individuals in Istanbul, Türkiye. Further comprehensive studies are needed to clarify both the cellular and molecular pathways of these two infections and to provide more information on the effect of HPgV on the course of the disease in HIV-infected individuals.

Human Pegivirus-1 Detection and Genotyping in Brazilian Patients with Fulminant Hepatitis

Fulminant hepatitis is a severe clinical disease characterized by a marked decline in liver function and encephalopathy. In a previous survey, using metagenomics in a group of 27 patients with this clinical condition, we observed an expressive quantity of reads of the Human pegivirus-1 (HPgV-1). Therefore, the objective of this study was to evaluate the frequency, molecular features, and HPgV-1 circulating genotypes in patients with fulminant hepatitis. After testing the collected plasma samples, we discovered twelve samples (44.4%) that were positive for HPgV-1 RNA (using both real-time and nested PCR). The positive samples presented a mean cycle threshold (Ct) of 28.5 (±7.3). Genotyping assignments revealed that all HPgV-1 positive samples belonged to the HPgV-1 genotype 2 (both subgenotypes 2A and 2B were identified). Although HPgV-1 is considered a commensal virus, little is known regarding its prevalence and genotypes in cases of fulminant hepatitis. More research is needed to understand whether HPgV-1 can be implicated in clinical disorders and infectious diseases.

Review of human pegivirus: Prevalence, transmission, pathogenesis, and clinical implication

Human pegivirus (HPgV-1), previously known as GB virus C (GBV-C) or hepatitis G virus (HGV), is a single-stranded positive RNA virus belonging to the genus Pegivirus of the Flaviviridae family. It is transmitted by percutaneous injuries (PIs), contaminated blood and/or blood products, sexual contact, and vertical mother-to-child transmission. It is widely prevalent in general population, especially in high-risk groups. HPgV-1 viremia is typically cleared within the first 1–2 years of infection in most healthy individuals, but may persist for longer periods of time in immunocompromised individuals and/or those co-infected by other viruses. A large body of evidences indicate that HPgV-1 persistent infection has a beneficial clinical effect on many infectious diseases, such as acquired immunodeficiency syndrome (AIDS) and hepatitis C. The beneficial effects seem to be related to a significant reduction of immune activation, and/or the inhabitation of co-infected viruses (e.g. HIV-1). HPgV-1 has a broad cellular tropism for lymphoid and myeloid cells, and preferentially replicates in bone marrow and spleen without cytopathic effect, implying a therapeutic potential. The paper aims to summarize the natural history, prevalence and distribution characteristics, and pathogenesis of HPgV-1, and discuss its association with other human viral diseases, and potential use in therapy as a biovaccine or viral vector.

Virus discovery in chronic inflammatory demyelinating polyneuropathy

The events triggering and/or sustaining the auto-immune response underlying chronic inflammatory demyelinating polyneuropathy (CIDP) are unknown. Similar to Guillain-Barré syndrome (GBS), a viral infection might play a role in CIDP. In this study, an virus detection method (VIDISCA-next generation sequencing) capable of detecting known and unknown viruses, was used to analyze the virome in serum of 47 CIDP patients at different time points of the disease and, when available, in cerebrospinal fluid (CSF) samples (N: 17). Serum samples of GBS patients (N:24) and healthy controls (N:114) were used for comparisons. In 5/47 (10.6%; 95% CI: 4-23) CIDP samples, 10/24 (42%; 95% CI: 22-63) GBS samples and 32/114 (28.1%; 95% CI: 20-37) healthy controls samples, anelloviruses were detected, generally regarded as a non-pathogenic species. Parvovirus B19 and GB virus C were found in two CIDP samples (4%). Parvovirus B19, HIV-1 and GB virus C were found in three GBS samples (13%). In 2/17 CIDP CSF samples, an anellovirus and polyomavirus were detected, probably due to contamination during lumbar puncture. No sequences of other viruses were detected in serum or CSF. A (persistent) viral infection sustaining the auto-immune response in CIDP seems therefore unlikely.

Therapeutic Exploitation of Viral Interference

Viral interference, originally, referred to a state of temporary immunity, is a state whereby infection with a virus limits replication or production of a second infecting virus. However, replication of a second virus could also be dominant over the first virus. In fact, dominance can alternate between the two viruses. Expression of type I interferon genes is many times upregulated in infected epithelial cells. Since the interferon system can control most, if not all, virus infections in the absence of adaptive immunity, it was proposed that viral induction of a nonspecific localized temporary state of immunity may provide a strategy to control viral infections. Clinical observations also support such a theory, which gave credence to the development of superinfection therapy (SIT). SIT is an innovative therapeutic approach where a non-pathogenic virus is used to infect patients harboring a pathogenic virus. For the functional cure of persistent viral infections and for the development of broad- spectrum antivirals against emerging viruses a paradigm shift was recently proposed. Instead of the virus, the therapy should be directed at the host. Such a host-directed-therapy (HDT) strategy could be the activation of endogenous innate immune response via toll-like receptors (TLRs). Superinfection therapy is such a host-directed-therapy, which has been validated in patients infected with two completely different viruses, the hepatitis B (DNA), and hepatitis C (RNA) viruses. SIT exerts post-infection interference via the constant presence of an attenuated non-pathogenic avian double- stranded (ds) RNA viral vector which boosts the endogenous innate (IFN) response. SIT could, therefore, be developed into a biological platform for a new "one drug, multiple bugs" broad-spectrum antiviral treatment approach.

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.

Molecular and Clinical Profiles of Human Pegivirus Type 1 Infection in Individuals Living with HIV-1 in the Extreme South of Brazil

Human pegivirus type 1 (HPgV-1) infection has been associated with a beneficial effect on the prognosis of human immunodeficiency virus type 1 (HIV-1)-coinfected individuals. However, the mechanisms involved in this protection are not yet fully elucidated. To date, circulating HPgV-1 genotypes in HIV-1-infected individuals have not yet been identified in the extreme south of Brazil. The present study aimed to determine the genotypic circulation of HPgV-1 and the influence of HPgV-1 status and persistence time on the evolution of HIV-1 infection. A retrospective cohort of 110 coinfected individuals was analyzed. Samples were subjected to viral RNA extraction, cDNA synthesis, nested PCR, and genotyping. Genotypes 1 (2.8%), 2 (47.9% of subtype 2a and 42.3% of subtype 2b), and 3 (7%) were identified. In antiretroviral treatment-naïve subjects HPgV-1 subtype 2b was associated with lower HIV-1 viral load (VL) rates (p = 0.04) and higher CD4+ T-cell counts (p = 0.03) than was subtype 2a, and the positivity for HPgV-1 was associated with higher CD4+ T-cell counts (p = 0.02). However, there was no significant difference in HIV-1 VL between HPgV-1-positive and HPgV-1-negative subjects (p = 0.08). There was no significant association between the different groups in HPgV-1 persistence and median HIV-1 VL (p = 0.66) or CD4+ T-cell counts (p = 0.15). HPgV-1 subtype 2b is associated with better prognosis of HIV-1 infection. Although HPgV-1 infection is persistent, our data suggest that the time of infection does not influence HIV-1 VL or CD4+ T-cell counts in coinfected subjects.

Prevalence and vertical transmission of human pegivirus among pregnant women infected with HIV

OBJECTIVE

To determine the prevalence of human pegivirus (HPgV) and factors associated with vertical transmission among pregnant women infected with HIV.

METHOD

A retrospective cross-sectional study was conducted among pregnant women treated at an HIV reference service in Rio Grande, Brazil, between January 1, 2010, and January 1, 2015. The polymerase chain reaction was used to diagnose HPgV infection among the women and their neonates. Clinical, obstetric, and neonatal data were obtained from medical records.

RESULTS

Infection with HPgV was detected among 16 (25%) of 63 women and 5 (8%) of 63 newborns, corresponding to a vertical transmission rate of 31%. Multivariate analysis demonstrated that the absence of prenatal care was the only risk factor for vertical transmission of HPgV (prevalence ratio 19.61, 95% confidence interval 1.29-297.48; P=0.032).

CONCLUSION

Prenatal care could protect against vertical transmission of HPgV among women infected with HIV; however, studies among HIV-negative individuals are still required to verify this correlation.

Human pegivirus-1 in the CSF of patients with HIV-associated neurocognitive disorder (HAND) may be derived from blood in highly viraemic patients

BACKGROUND

Human pegivirus-1 (HPgV-1) infection in the brain has not been extensively examined and its association with disease remains unconfirmed. In a high throughput sequencing study to look for infectious agents that could play a role in HIV-associated neurocognitive disorder (HAND), this virus was detected in 3 of 8 CSF samples.

OBJECTIVES

To determine the significance of this finding, additional patients were screened and the viral load and viral diversity in blood and CSF were examined.

STUDY DESIGN

Nested PCR of the viral 5'NCR region was performed on blood and CSF pairs from 16 HAND patients. PCR products were cloned, sequenced and analysed to determine viral diversity in blood and CSF. HPgV-1 viral loads were determined in paired blood and CSF of 2 patients by digital droplet PCR. Nested PCR was also performed on CSF samples from patients with other brain disorders.

RESULTS

Virus was detected in both blood and CSF in 3 of 16 HAND patients. Viral loads were very high in blood (8.81 and 10.56 log copies/ml) and 4-5 logs lower in CSF (4.68 and 5.84 log copies/ml). Sequence analysis of 5'NCR clones in blood and CSF showed limited variation. The dominant viral variant (based on clonal sequence identity) in blood and CSF was usually identical. HPgV-1 was detected in CSF from patients with other brain disorders at a similar frequency (15% versus 18.75% in HAND patients).

CONCLUSION

While several studies have reported HPgV-1 detection in CSF of patients with brain disease, this is the only study that has examined both blood and CSF compartments simultaneously. Our findings show that virus in CSF always coincided with viraemia and levels were 4-5 logs higher in blood. While a rare, but specific brain tropism cannot be excluded, blood is the more probable source of virus in HAND patients.

Prevalence and Clinical Impact of Human Pegivirus-1 Infection in HIV-1-Infected Individuals in Yunnan, China

Human Pegivirus-1 (HPgV-1) may have a beneficial impact on disease progression in human immunodeficiency virus-1 (HIV-1) infection. However, analysis of the genotypic diversity of HPgV-1 and its relevance to the progression of HIV-1 disease remains limited. A total of 1062 HIV-1-infected individuals were recruited in all sixteen prefectures of Yunnan province, China. The reverse transcription nested polymerase chain reaction (RT-nPCR), phylogenetic analyses, and clinical data analyses were used to detect HPgV-1 infection, determine genotype, and analyze HPgV-1 genotype impact on HIV-1 disease progression. The overall positive rate of HPgV-1 RNA was 23.4% (248/1062), and the frequency of HPgV-1 infection in injecting drug users (IDUs) (28.5%, 131/460) was significantly higher than in heterosexuals (19.4%, 117/602). Multiple genotypes were identified in 212 subjects with successful sequencing for the E2 gene, including genotype 7 (55.7%), genotype 3 (34.9%), genotype 4 (4.7%), genotype 2 (3.3%), and an unclassified group (1.4%). Moreover, genotype 7 predominated in IDUs, whereas genotype 3 was the most common in heterosexuals. Our results revealed that HPgV-1 genotype 7 groups exhibited significantly lower HIV-1 viral load and higher CD4⁺ cell counts. This finding suggests that HPgV-1 genotype 7 may be associated with a better progression of HIV-1 disease.

Extracellular Vesicles Exploit Viral Entry Routes for Cargo Delivery

Extracellular vesicles (EVs) have emerged as crucial mediators of intercellular communication, being involved in a wide array of key biological processes. Eukaryotic cells, and also bacteria, actively release heterogeneous subtypes of EVs into the extracellular space, where their contents reflect their (sub)cellular origin and the physiologic state of the parent cell. Within the past 20 years, presumed subtypes of EVs have been given a rather confusing diversity of names, including exosomes, microvesicles, ectosomes, microparticles, virosomes, virus-like particles, and oncosomes, and these names are variously defined by biogenesis, physical characteristics, or function. The latter category, functions, in particular the transmission of biological signals between cells in vivo and how EVs control biological processes, has garnered much interest. EVs have pathophysiological properties in cancer, neurodegenerative disorders, infectious disease, and cardiovascular disease, highlighting possibilities not only for minimally invasive diagnostic applications but also for therapeutic interventions, like macromolecular drug delivery. Yet, in order to pursue therapies involving EVs and delivering their cargo, a better grasp of EV targeting is needed. Here, we review recent progress in understanding the molecular mechanisms underpinning EV uptake by receptor-ligand interactions with recipient cells, highlighting once again the overlap of EVs and viruses. Despite their highly heterogeneous nature, EVs require common viral entry pathways, and an unanticipated specificity for cargo delivery is being revealed. We discuss the challenges ahead in delineating specific roles for EV-associated ligands and cellular receptors.

Discovery of a Novel Human Pegivirus in Blood Associated with Hepatitis C Virus Co-Infection

Hepatitis C virus (HCV) and human pegivirus (HPgV), formerly GBV-C, are the only known human viruses in the Hepacivirus and Pegivirus genera, respectively, of the family Flaviviridae. We present the discovery of a second pegivirus, provisionally designated human pegivirus 2 (HPgV-2), by next-generation sequencing of plasma from an HCV-infected patient with multiple bloodborne exposures who died from sepsis of unknown etiology. HPgV-2 is highly divergent, situated on a deep phylogenetic branch in a clade that includes rodent and bat pegiviruses, with which it shares <32% amino acid identity. Molecular and serological tools were developed and validated for high-throughput screening of plasma samples, and a panel of 3 independent serological markers strongly correlated antibody responses with viral RNA positivity (99.9% negative predictive value). Discovery of 11 additional RNA-positive samples from a total of 2440 screened (0.45%) revealed 93–94% nucleotide identity between HPgV-2 strains. All 12 HPgV-2 RNA-positive cases were identified in individuals also testing positive for HCV RNA (12 of 983; 1.22%), including 2 samples co-infected with HIV, but HPgV-2 RNA was not detected in non-HCV-infected individuals (p<0.0001), including those singly infected by HIV (p = 0.0075) or HBV (p = 0.0077), nor in volunteer blood donors (p = 0.0082). Nine of the 12 (75%) HPgV-2 RNA positive samples were reactive for antibodies to viral serologic markers, whereas only 28 of 2,429 (1.15%) HPgV-2 RNA negative samples were seropositive. Longitudinal sampling in two individuals revealed that active HPgV-2 infection can persist in blood for at least 7 weeks, despite the presence of virus-specific antibodies. One individual harboring both HPgV-2 and HCV RNA was found to be seronegative for both viruses, suggesting a high likelihood of simultaneous acquisition of HCV and HPgV-2 infection from an acute co-transmission event. Taken together, our results indicate that HPgV-2 is a novel bloodborne infectious virus of humans and likely transmitted via the parenteral route.

To date, only one human hepacivirus (HCV) and one human pegivirus (HPgV-1/GBV-C) in the family Flaviviridae are known to exist. Using unbiased metagenomic next-generation sequencing, we discovered and assembled the genome of a novel pegivirus from plasma corresponding to an HCV-infected patient who died from unknown sepsis. This virus, provisionally named human pegivirus 2 (HPgV-2), is highly divergent, sharing <32% amino acid identity with its nearest relatives, a bat and rodent pegivirus. Identification and sequencing of 11 additional HPgV-2 viruses, revealing 93–94% identity between strains, as well as documented antibody responses using multiple markers, confirm that HPgV-2 is a bona fide novel infectious virus of humans. Several lines of evidence, including (1) a documented history of multiple bloodborne exposures in the index patient, (2) parallel detection of HPgV-2 and HCV RNA in an individual during the "window period" between infection and the appearance of detectable antibody, and (3) a tight observed association between HPgV-2 and HCV co-infection, suggest that HPgV-2 is an infectious agent capable of bloodborne transmission.

Utility of Metagenomic Next-Generation Sequencing for Characterization of HIV and Human Pegivirus Diversity

Given the dynamic changes in HIV-1 complexity and diversity, next-generation sequencing (NGS) has the potential to revolutionize strategies for effective HIV global surveillance. In this study, we explore the utility of metagenomic NGS to characterize divergent strains of HIV-1 and to simultaneously screen for other co-infecting viruses. Thirty-five HIV-1-infected Cameroonian blood donor specimens with viral loads of >4.4 log₁₀ copies/ml were selected to include a diverse representation of group M strains. Random-primed NGS libraries, prepared from plasma specimens, resulted in greater than 90% genome coverage for 88% of specimens. Correct subtype designations based on NGS were concordant with sub-region PCR data in 31 of 35 (89%) cases. Complete genomes were assembled for 25 strains, including circulating recombinant forms with relatively limited data available (7 CRF11_cpx, 2 CRF13_cpx, 1 CRF18_cpx, and 1 CRF37_cpx), as well as 9 unique recombinant forms. HPgV (formerly designated GBV-C) co-infection was detected in 9 of 35 (25%) specimens, of which eight specimens yielded complete genomes. The recovered HPgV genomes formed a diverse cluster with genotype 1 sequences previously reported from Ghana, Uganda, and Japan. The extensive genome coverage obtained by NGS improved accuracy and confidence in phylogenetic classification of the HIV-1 strains present in the study population relative to conventional sub-region PCR. In addition, these data demonstrate the potential for metagenomic analysis to be used for routine characterization of HIV-1 and identification of other viral co-infections.

Local Virus Extinctions following a Host Population Bottleneck

A small number of African green monkeys (AGMs) were introduced into the Caribbean from West Africa in the 1600s. To determine the impact of this population bottleneck on the AGM virome, we used metagenomics to compare the viral nucleic acids in the plasma of 43 wild AGMs from West Africa (Gambia) to those in 44 AGMs from the Caribbean (St. Kitts and Nevis). Three viruses were detected in the blood of Gambian primates: simian immunodeficiency virus (SIVagm; in 42% of animals), a novel simian pegivirus (SPgVagm; in 7% of animals), and numerous novel simian anelloviruses (in 100% of animals). Only anelloviruses were detected in the Caribbean AGMs with a prevalence and levels of viral genetic diversity similar to those in the Gambian animals. A host population bottleneck therefore resulted in the exclusion of adult-acquired SIV and pegivirus from the Caribbean AGMs. The successful importation of AGM anelloviruses into the Caribbean may be the result of their early transmission to infants, very high prevalence in African AGMs, and frequent coinfections with as many as 11 distinct variants.

IMPORTANCE

The extent to which viruses can persist in small isolated populations depends on multiple host, viral, and environmental factors. The absence of prior infections may put an immunologically naive population at risk for disease outbreaks. Isolated populations originating from a small number of founder individuals are therefore considered at increased risk following contact with populations with a greater variety of viruses. Here, we compared the plasma virome of West African green monkeys to that in their descendants after importation of a small number of animals to the Caribbean. A lentivirus and a pegivirus were found in the West African population but not in the Caribbean population. Highly diverse anelloviruses were found in both populations. A small founder population, limited to infants and young juvenile monkeys, may have eliminated the sexually transmitted viruses from the Caribbean AGMs, while anelloviruses, acquired at an earlier age, persisted through the host population bottleneck.

Complex links between natural tuberculosis and porcine circovirus type 2 infection in wild boar

Individuals in natural populations are exposed to a diversity of pathogens which results in coinfections. The aim of this study was to investigate the relation between natural infection with tuberculosis (TB) due to infection by bacteria of the Mycobacterium tuberculosis complex and porcine circovirus type 2 (PCV2) in free-ranging Eurasian wild boar (Sus scrofa). Apparent prevalence for TB lesions and PCV2 infection was extremely high in all age classes, including piglets (51% for TB; 85.7% for PCV2). Modeling results revealed that the relative risk of young (less than 2 years old) wild boar to test positive to PCV2 PCR was negatively associated with TB lesion presence. Also, an interaction between TB, PCV2, and body condition was evidenced: in wild boar with TB lesions probability of being PCV2 PCR positive increased with body condition, whereas this relation was negative for wild boar without TB lesions. This study provides insight into the coinfections occurring in free-ranging host populations that are naturally exposed to several pathogens at an early age. Using TB and PCV2 as a case study, we showed that coinfection is a frequent event among natural populations that takes place early in life with complex effects on the infections and the hosts.

Virus against virus (VIVI): a potential solution against HIV/AIDS

Most therapeutic regimens are aimed at the use of pharmacologic agents or the induction of immunological response against the pathological agent. However, these methods tend to be insufficient for the management of some of the most debilitating infectious diseases. Here we present a novel therapeutic approach. It involves voluntary super-infection of a subject having HIV/AIDS with a virus (GBV-C), which to date has not been shown to be responsible for any pathology. It has been shown to counter, suppress or eradicate the agent responsible for the severe disease. Several studies demonstrate the role of different micro-organisms in influencing the growth of other pathogens in the human body. This hypothesis requires meticulous testing before its implementation on humans. If the trials are successful, the implications for this hypothesis are promising considering the compliance issues and adverse effects associated with current standard of HIV care.

What ecologists can tell virologists

I pictured myself as a virus…and tried to sense what it would be like. --Jonas Salk. Ecology as a science evolved from natural history, the observational study of the interactions of plants and animals with each other and their environments. As natural history matured, it became increasingly quantitative, experimental, and taxonomically broad. Focus diversified beyond the Eukarya to include the hidden world of microbial life. Microbes, particularly viruses, were shown to exist in unfathomable numbers, affecting every living organism. Slowly viruses came to be viewed in an ecological context rather than as abstract, disease-causing agents. This shift is exemplified by an increasing tendency to refer to viruses as living organisms instead of inert particles. In recent years, researchers have recognized the critical contributions of viruses to fundamental ecological processes such as biogeochemical cycling, competition, community structuring, and horizontal gene transfer. This review describes virus ecology from a virus's perspective. If we are, like Jonas Salk, to imagine ourselves as a virus, what kind of world would we experience?

GB virus C infection in Indonesian HIV-positive patients

GB virus C (GBV-C), a human virus of the Flaviviridae family that is structurally and epidemiologically closest to hepatitis C virus (HCV), has been reported to confer beneficial outcomes in HIV-positive patients. However, the prevalence of GBV-C in HIV-positive individuals in Indonesia is unknown. Since GBV-C is more prevalent in anti-HCV positive patients than in anti-HCV negative subjects, transmission of GBV-C and HCV could be by the same method. This study examined the prevalence and molecular characteristics of GBV-C infection in HIV patients in Yogyakarta, Indonesia. The prevalence of GBV-C among HIV patients (n = 125, median age 31 years) based on the 5'UTR region was 111/125 (88.8%), including 39/48 (81.3%) and 72/77 (93.5%) HIV-infected patients with and without HCV infection, respectively. GBV-C isolates were of genotype 2a, 3 and 6 in 58.3%, 12.6% and 28.4% of patients, respectively. Patients with genotype 3 were significantly younger than those with genotypes 2a or 6 (P = 0.001 and P = 0.012, respectively). Genotypes 3 and 6 were significantly associated with injection drug use (P = 0.004 and P = 0.002, respectively) and HCV co-infection (P < 0.001 for both genotypes), indicating a shared transmission route with HCV. In conclusion, the prevalence of GBV-C among HIV-positive patients in Indonesia is high, and three genotypes were detected, namely genotype 2a, 3 and 6.

Identification of rodent homologs of hepatitis C virus and pegiviruses

Hepatitis C virus (HCV) and human pegivirus (HPgV or GB virus C) are globally distributed and infect 2 to 5% of the human population. The lack of tractable-animal models for these viruses, in particular for HCV, has hampered the study of infection, transmission, virulence, immunity, and pathogenesis. To address this challenge, we searched for homologous viruses in small mammals, including wild rodents. Here we report the discovery of several new hepaciviruses (HCV-like viruses) and pegiviruses (GB virus-like viruses) that infect wild rodents. Complete genome sequences were acquired for a rodent hepacivirus (RHV) found in Peromyscus maniculatus and a rodent pegivirus (RPgV) found in Neotoma albigula. Unique genomic features and phylogenetic analyses confirmed that these RHV and RPgV variants represent several novel virus species in the Hepacivirus and Pegivirus genera within the family Flaviviridae. The genetic diversity of the rodent hepaciviruses exceeded that observed for hepaciviruses infecting either humans or non-primates, leading to new insights into the origin, evolution, and host range of hepaciviruses. The presence of genes, encoded proteins, and translation elements homologous to those found in human hepaciviruses and pegiviruses suggests the potential for the development of new animal systems with which to model HCV pathogenesis, vaccine design, and treatment.

The genetic and biological characterization of animal homologs of human viruses provides insights into the origins of human infections and enhances our ability to study their pathogenesis and explore preventive and therapeutic interventions. Horses are the only reported host of nonprimate homologs of hepatitis C virus (HCV). Here, we report the discovery of HCV-like viruses in wild rodents. The majority of HCV-like viruses were found in deer mice (Peromyscus maniculatus), a small rodent used in laboratories to study viruses, including hantaviruses. We also identified pegiviruses in rodents that are distinct from the pegiviruses found in primates, bats, and horses. These novel viruses may enable the development of small-animal models for HCV, the most common infectious cause of liver failure and hepatocellular carcinoma after hepatitis B virus, and help to explore the health relevance of the highly prevalent human pegiviruses.