Viraemic frequencies and seroprevalence of non-primate hepacivirus and equine pegiviruses in horses and other mammalian species

Prevalence of Equine Hepacivirus Infections in France and Evidence for Two Viral Subtypes Circulating Worldwide

Like hepatitis C virus (HCV) in humans, the newly identified equine hepacivirus (NPHV) displays a predominating liver tropism that may evolve into chronic infections. The genomes of the two viruses share several organizational and functional features and are phylogenetically closest amongst the Hepacivirus genus. A limited amount of data is available regarding the spread of hepacivirus infections in horses. In this study, we asked whether in a more representative sample the prevalence and distribution of NPHV infections in France would resemble that reported so far in other countries. A total of 1033 horses sera from stud farms throughout France were analysed by qRT-PCR to determine the prevalence of ongoing NPHV infections and viral loads; in positive samples, partial sequences of NPHV's genome (5'UTR, NS3 and NS5B genes) were determined. Serum concentrations of biliary acids, glutamate dehydrogenase (GLDH) and L-gamma-glutamyl transferase (γ-GT) were measured for most horses. We detected NPHV infections in 6.2% of the horses, a prevalence that reached 8.3% in thoroughbreds and was significantly higher than in other breeds. The presence of circulating virus was neither significantly associated with biological disturbances nor with clinical hepatic impairment. Our phylogenetic analysis was based on both neighbour-joining and maximum-likelihood approaches. Its result shows that, like almost everywhere else in the world so far, two major groups of NPHV strains infect French domestic horses. Based on genetic distances, we propose a classification into two separate NPHV subtypes. Viral loads in the serum of horses infected by the main subtype were, in average, four times higher than in those infected by the second subtype. We hypothesize that amino acid substitutions in the palm domain of NS5B between NPHV subtypes could underlie viral phenotypes that explain this result.

Acute and chronic infections with nonprimate hepacivirus in young horses

The recently discovered nonprimate hepacivirus (NPHV) naturally infects horses and is the closest known homolog of hepatitis C virus to date. Within a follow-up study acute field infections were monitored in four young Thoroughbred horses until the ages of 12-13 months. Serum samples were analyzed for the presence of NPHV RNA and anti-NPHV NS3 antibodies and liver specific parameters were evaluated. The four young horses were not able to clear infection, but remained chronically infected for the entire monitored time period despite the presence of NPHV specific antibodies.

Exploring the possibility of arthropod transmission of HCV

Hepatitis C virus (HCV) is a major cause of chronic hepatitis, cirrhosis, and liver cancer occurring in up to 3% of the world's population. Parenteral exposure to HCV is the major mode of transmission of infection. Once established, infection will persist in up to 85% of individuals with only a minority of patients clearing viremia. Egypt has possibly the highest HCV prevalence in the world where 10-20% of the general population are infected with HCV. Endemic HCV appears to be concentrated in the tropics and sub-tropics where there are higher biting rates from insects. The question as to whether a bridge vector transmission is possible, via arthropods, both between humans and/or from an animal reservoir to humans is explored. Mechanical transmission, as opposed to biological transmission, is considered. Mechanical transmission can be an efficient way of transmitting an infection, as effective as biological transmission. Probability of transmission can increase as to the immediate circumstances and conditions at the time. Several factors may enhance mechanical transmission, including high levels of microbes in the vector, frequent biting, the close proximity, and contact between vectors and recipients as well as high density of insects. HCV has been isolated from bodies or heads of mosquitoes collected from the houses of HCV-infected individuals. The possibility of enzootic cycles of HCV tangential transmission via bridging vectors, such as, arthropods needs to be further investigated and possible animal reservoirs, including domestic rural epizootic cycles for HCV infection, requires further research with particular initial emphasis on equine infections. J. Med. Virol. 89:187-194, 2017. © 2016 Wiley Periodicals, Inc.

Vertical transmission of hepatitis C virus-like non-primate hepacivirus in horses

Non-primate hepacivirus (NPHV), a recently discovered hepatotropic virus infecting horses, is phylogenetically the closest known homologue of hepatitis C virus (HCV). The main route for acquiring HCV infection in childhood is vertical transmission. However, nothing is known about the natural mode of transmission for NPHV. To investigate the possibility of vertically transmitted NPHV infection in horses, 20 Thoroughbred broodmares and their foals were monitored during foaling season 2015 until 6 months post-partum. Prepartal serum was taken from the mares, and during foaling umbilical cord blood and colostrum samples were collected. Postnatal serum samples were taken from the foals after delivery. In addition, serum was taken at 3 and 6 months after foaling from all mares and foals. Samples were analysed for the presence of NPHV RNA by quantitative real-time PCR and for the presence of anti-NPHV NS3 antibodies by luciferase immunoprecipitation system. Identified NPHV isolates were sequenced and phylogenetic analysis of the viral glycoproteins was used to track the course of naturally occurring infections and the circulation of distinct isolates within the herd. At parturition, 16 mares were seropositive, including four viraemic mares. Vertical transmission occurred in one of these four mare-foal pairs. Interestingly, NPHV isolates of newly infected foals and mares after 3 and 6 months cluster in their respective pasture herds suggesting another horizontal route of transmission.

Experimental models of hepatitis B and C - new insights and progress

Viral hepatitis is a major cause of morbidity and mortality, affecting hundreds of millions of people worldwide. Hepatitis-causing viruses initiate disease by establishing both acute and chronic infections, and several of these viruses are specifically associated with the development of hepatocellular carcinoma. Consequently, intense research efforts have been focusing on increasing our understanding of hepatitis virus biology and on improving antiviral therapy and vaccination strategies. Although valuable information on viral hepatitis emerged from careful epidemiological studies on sporadic outbreaks in humans, experimental models using cell culture, rodent and non-human primates were essential in advancing the field. Through the use of these experimental models, improvement in both the treatment and prevention of viral hepatitis has progressed rapidly; however, agents of viral hepatitis are still among the most common pathogens infecting humans. In this Review, we describe the important part that these experimental models have played in the study of viral hepatitis and led to monumental advances in our understanding and treatment of these pathogens. Ongoing developments in experimental models are also described.

Equine Mesenchymal Stromal Cells from Different Sources Efficiently Differentiate into Hepatocyte-Like Cells

Adult equine hepatocytes have proven challenging to culture long term in vitro as they rapidly lose their morphology and functionality, thus limiting studies on liver function and response to disease. In this study, we describe for the first time the differentiation of equine mesenchymal stromal cells (MSC) from a variety of sources into functional hepatocyte-like cells (HLC). First, we differentiated equine umbilical cord blood (UCB)-derived MSC into HLC and found that these cells exhibited a distinct polygonal morphology, stored glycogen as visualized by periodic acid Schiff's reagent staining, and were positive for albumin and other hepatocyte-specific genes. Second, we demonstrated that UCB-HLC could be revived following cryopreservation and retained their phenotype for at least 10 days. Third, we differentiated three sets of MSC from bone marrow (BM), adipose tissue (AT), and peripheral blood (PB), matched within the same horse. We achieved a 100% differentiation success rate with BM, 0% with AT, and 66% with PB. An additional set of nine PB-MSC samples resulted in an overall success rate of 42% (n = 12), and age or gender did not seem to have an effect on the success of hepatic differentiation from that source. In a final set of experiments, we evaluated the use of these HLC as tools in different fields of biomedical research like virology, to study viral growth, and toxicology, to study chemicals with hepatic toxicity. Equine HLC were found susceptible for infection with the equine herpesviruses type 1 (EHV-1), -2, and -5, and exhibited a more sensitive dose-dependent response to arsenic toxicity than the commonly used human hepatocellular cell line HepG2. Taken together, these data indicate that equine MSC can be efficiently differentiated into HLC and these equine HLC could be a useful tool for in vitro studies.

First Description of Hepacivirus and Pegivirus Infection in Domestic Horses in China: A Study in Guangdong Province, Heilongjiang Province and Hong Kong District

Since 2012, three viruses, known as equine hepacivirus (EqHV), equine pegivirus (EPgV) and Theiler’s disease-associated virus (TDAV), have been discovered in equines. Given that these viruses are the newest members of the Flaviviridae family, genomic information concerning circulating EqHV, EPgV and TDAV strains around the world is limited. To date, no genetic surveillance studies have been performed on these three viruses in the equine population of China. Here, a total of 177 serum samples were collected from equines across China between 2014 and 2015. Using PCR, we detected viral RNA in the serum samples, six of which were EqHV positive and two of which were EPgV positive. Co-infection with the two viruses was not observed among the Chinese equines studied, and TDAV RNA was not detected in the equine serum samples collected for this study. Phylogenetic analysis of partial NS5B open reading frame (ORF), NS3 ORF, and 5’ untranslated region nucleotide sequences from EqHV as well as partial NS3 ORF sequence from EPgV indicated that EqHV and EPgV have evolved into two main clades by themselves, both of which are circulating in China. Based on the partial NS5B and NS3 ORF sequences of EqHV, the sequences of one clade were also split into two subclades. This study enriches our knowledge of the geographic distribution of these three equine viruses.

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.

First report of equine Pegivirus in South America, Brazil

The human Pegivirus (HPgV, also known as GBV-C virus or hepatitis G virus) is a lymphotropic RNA-virus phylogenetically related to the Hepatitis C virus, which infects approximately 5% of the world's human population. Recently, two novel, presumably hepatotropic, pegiviruses, designated as equine Pegivirus (EPgV) and Theiler's Disease Associated Virus (TDAV), were discovered in horses with clinical and laboratory evidence of hepatic disease. To verify the occurrence of pegiviruses infection in horses from Pará State, northern Brazil, serum samples from 114 horses located in four cities (Acará, Belém, Dom Eliseu and Ananindeua) were submitted for the molecular analysis of EPgV by nested RT-PCR. The results of nucleotide sequencing and phylogenetic analysis of EPgV NS3 and NS5B genomic regions confirmed one positive sample among 114 tested samples (1/114; 0.8%). No evidence of TDAV infection was found, but despite the low prevalence and unknown clinical significance among the studied population, these results represent the first molecular detection of EPgV in horses in South America.

Frequent presence of hepaci and pegiviruses in commercial equine serum pools

Novel viruses belonging to the genera Hepacivirus and Pegivirus have recently been discovered in horses and other animal species. Viral genomes of non-primate hepaciviruses (NPHV), equine pegivirus 1 (EPgV 1) and Theiler's disease associated virus (TDAV) were detected in a horse serum routinely used for cell culture propagation in our laboratory. Therefore, a study was carried out to further investigate the presence of these human Hepatitis C virus (HCV) related viruses in equine serum based products used in veterinary medicine and for research and to characterize the viral genomes. Without exception all commercially available equine sera purchased for cell culture propagation (n=6) were tested positive for NPHV, EPgV 1 or TDAV genomes by qRT-PCR. Molecular analyses of one single commercial horse serum from Europe confirmed multiple viral genomes, including two TDAV genomes significantly different from the only published TDAV sequence. Furthermore, multiple batches of horse serum pools (n=35) collected for manufacturing of biological products turned out to be positive for NPHV and EPgV 1 genomes. Nevertheless, the final commercial products (n=9) were exclusively tested qRT-PCR negative. Field samples (n=119) obtained from two premises located in the same region as the donor horses were analyzed, demonstrating the frequent presence of NPHV and EPgV 1, but the absence of TDAV genomes. The presence of NPHV, EPgV 1 and TDAV in commercial equine sera and serum based products could have considerable consequences for biosecurity and may also bias the outcome of research studies conducted with related viruses.

Hepacivirus cross-species transmission and the origins of the hepatitis C virus

Just 5 years ago the hepatitis C virus (HCV) - a major cause of liver disease infecting >3% of people worldwide - was the sole confirmed member of the Hepacivirus genus. Since then, genetically-diverse hepaciviruses have been isolated from bats, dogs, cows, horses, primates and rodents. Here we review current information on the hepaciviruses and speculate on the zoonotic origins of the viruses in humans, horses and dogs. Recent and direct cross-species transmission from horses to dogs appears plausible, but the zoonotic origins of HCV in humans remain opaque. Mechanical transmission by biting insects, notably tabanids, could, in theory, connect all three host species. Much further work is needed to understand the transmission and zoonotic potential of hepaciviruses in natural populations.

Epidemiology of hepatitis C in Croatia in the European context

We analyzed prevalence, risk factors and hepatitis C virus (HCV) genotype distribution in different population groups in Croatia in the context of HCV epidemiology in Europe, with the aim to gather all existing information on HCV infection in Croatia which will be used to advise upon preventive measures. It is estimated that 35000-45000 of the Croatian population is chronically infected with HCV. Like in other European countries, there have been changes in the HCV epidemiology in Croatia over the past few decades. In some risk groups (polytransfused and hemodialysis patients), a significant decrease in the HCV prevalence was observed after the introduction of routine HCV screening of blood/blood products in 1992. Injecting drug users (IDUs) still represent a group with the highest risk for HCV infection with prevalence ranging from 29% to 65%. Compared to the prevalence in the Croatian general population (0.9%), higher prevalence rates were found in prison populations (8.3%-44%), human immunodeficiency virus-infected patients (15%), persons with high-risk sexual behavior (4.6%) and alcohol abusers (2.4%). Low/very low prevalence was reported in children and adolescents (0.3%) as well as in blood donors (0%-0.009%). In addition, distribution of HCV genotypes has changed due to different routes of transmission. In the general population, genotypes 1 and 3 are most widely distributed (60.4%-79.8% and 12.9%-47.9%, respectively). The similar genotype distribution is found in groups with high-risk sexual behavior. Genotype 3 is predominant in Croatian IDUs (60.5%-83.9%) while in the prison population genotypes 3 and 1 are equally distributed (52.4% and 47.6%). Data on HCV prevalence and risk factors for transmission are useful for implementation of preventive measures and HCV screening.

Detection of non-primate hepaciviruses in UK dogs

Non-primate hepacivirus (NPHV) has been identified in dogs, horses, bats and wild rodents. The presence of NPHV in dogs outside of the USA however is yet to be established. Here we describe for the first time the detection of NPHV in the UK dog population (described throughout the manuscript as CnNPHV). We examined tissues collected from dogs housed in a rehoming kennel where respiratory disease was endemic. CnNPHV RNA was detected in the tracheal tissues of 48/210 dogs by RT-PCR, and in the liver, lung and/or tracheal tissues of 12/20 dogs. The presence of CnNPHV RNA, and its tropism was confirmed by in situ hybridisation. Histopathological examination demonstrated a trend toward higher histopathological scores in CnNPHV RNA positive respiratory tissues, although, this was not statistically significant. Our findings broaden the geographic distribution and our understanding of CnNPHV. Further evidence of CnNPHV replication in canids warrants investigation.

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Non-primate hepacivirus (NPHV) has been detected in UK dog population.

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NPHV has dual respiratory and hepatic tropism.

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This is the first time NPHV RNA was detected in lower respiratory tract.

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This study broaden the geographical distribution and our understanding of NPHV.

Genetic and serological surveillance for non-primate hepacivirus in horses in Japan

Non-primate hepacivirus (NPHV) is a recently discovered homolog of the hepatitis C virus in horses. The frequency and distribution of NPHV infections among horses in Japan is unknown. In this study, serum samples from 453 horses across Japan were screened for NPHV RNA using real-time RT-PCR and anti-nonstructural 3 protein (NS3) antibodies using the Gaussia luciferase immunoprecipitation system assay. In order to monitor the course of NPHV infection in horses, we examined 31 stored samples (9 adult horses and 22 young horses) obtained one year ago and compared the results to the recent data. Stored sera from 7 mare-foal pairs were also examined. The NS3 region sequences of 14 NPHV strains from NPHV RNA positive serum samples were determined and analyzed phylogenically. Of the 453 serum samples tested, 33.55% were positive for anti-NS3 antibody and 13.68% were positive for NPHV RNA. We found a higher rate of NPHV RNA detection in serum obtained from young horses (1-2 years of age) than that of adults, in two geographically distinct areas. We observed higher variation in the course of infection over one year in young horses than in adult horses. The foals were infected with NPHV after the weaning period. Phylogenic analysis revealed that while NPHV NS3 genes isolated in Japan clustered with sequences previously classified as NPHV, but the genetic diversity of the Japanese NPHV strains we detected was not correlated with their geographic origin. In conclusion, Japanese horses exhibit a high prevalence of NPHV. Young age appears to be a risk factor for such viral infection in Japan, although the infectious route was not determined.

Assessment of cross-species transmission of hepatitis C virus-related non-primate hepacivirus in a population of humans at high risk of exposure

The recent discovery of hepatitis C virus (HCV)-related viruses in different animal species has raised new speculations regarding the origin of HCV and the possibility of a zoonotic source responsible for the endemic HCV transmission. As a consequence, these new findings prompt questions regarding the potential for cross-species transmissions of hepaciviruses. The closest relatives to HCV discovered to date are the non-primate hepaciviruses (NPHVs), which have been described to infect horses. To evaluate the risk of a potential zoonotic transmission, we analysed NPHV RNA and antibodies in humans with occupational exposure to horses in comparison with a low-risk group. Both groups were negative for NPHV RNA, even though low seroreactivities against various NPHV antigens could be detected irrespective of the group. In conclusion, we did not observe evidence of NPHV transmission between horses and humans.

Identification of a Novel Hepacivirus in Domestic Cattle from Germany

Hepatitis C virus (HCV) continues to represent one of the most significant threats to human health. In recent years, HCV-related sequences have been found in bats, rodents, horses, and dogs, indicating a widespread distribution of hepaciviruses among animals. By applying unbiased high-throughput sequencing, a novel virus of the genus Hepacivirus was discovered in a bovine serum sample. De novo assembly yielded a nearly full-length genome coding for a polyprotein of 2,779 amino acids. Phylogenetic analysis confirmed that the virus represents a novel species within the genus Hepacivirus. Viral RNA screening determined that 1.6% (n = 5) of 320 individual animals and 3.2% (n = 5) of 158 investigated cattle herds in Germany were positive for bovine hepacivirus. Repeated reverse transcription-PCR (RT-PCR) analyses of animals from one dairy herd proved that a substantial percentage of cows were infected, with some of them being viremic for over 6 months. Clinical and postmortem examination revealed no signs of disease, including liver damage. Interestingly, quantitative RT-PCR from different organs and tissues, together with the presence of an miR-122 binding site in the viral genome, strongly suggests a liver tropism for bovine hepacivirus, making this novel virus a promising animal model for HCV infections in humans.

IMPORTANCE

Livestock animals act as important sources for emerging pathogens. In particular, their large herd size and the existence of multiple ways of direct and food-borne infection routes emphasize their role as virus reservoirs. Apart from the search for novel viruses, detailed characterization of these pathogens is indispensable in the context of risk analysis. Here, we describe the identification of a novel HCV-like virus in cattle. In addition, determination of the prevalence and of the course of infection in cattle herds provides valuable insights into the biology of this novel virus. The results presented here form a basis for future studies targeting viral pathogenesis of bovine hepaciviruses and their potential to establish zoonotic infections.

Surveying the global virome: identification and characterization of HCV-related animal hepaciviruses

Recent advances in sequencing technologies have greatly enhanced our abilities to identify novel microbial sequences. Thus, our understanding of the global virome and the virome of specific host species in particular is rapidly expanding. Identification of animal viruses is important for understanding animal disease, the origin and evolution of human viruses, as well as zoonotic reservoirs for emerging infections. Although the human hepacivirus, hepatitis C virus (HCV), was identified 25years ago, its origin has remained elusive. In 2011, the first HCV homolog was reported in dogs but subsequent studies showed the virus to be widely distributed in horses. This indicated a wider hepacivirus host range and paved the way for identification of rodent, bat and non-human primate hepaciviruses. The equine non-primate hepacivirus (NPHV) remains the closest relative of HCV and is so far the best characterized. Identification and characterization of novel hepaciviruses may in addition lead to development of tractable animal models to study HCV persistence, immune responses and pathogenesis. This could be particular important, given the current shortage of immunocompetent models for robust HCV infection. Much remains to be learned on the novel hepaciviruses, including their association with disease, and thereby how relevant they will become as HCV model systems and for studies of animal disease. This review discusses how virome analysis led to identification of novel hepaci- and pegiviruses, their genetic relationship and characterization and the potential use of animal hepaciviruses as models to study hepaciviral infection, immunity and pathogenesis. This article forms part of a symposium in Antiviral Research on "Hepatitis C: Next steps toward global eradication."

Characterization of nonprimate hepacivirus and construction of a functional molecular clone

Nonprimate hepacivirus (NPHV) is the closest known relative of hepatitis C virus (HCV) and its study could enrich our understanding of HCV evolution, immunity, and pathogenesis. High seropositivity is found in horses worldwide with ∼ 3% viremic. NPHV natural history and molecular virology remain largely unexplored, however. Here, we show that NPHV, like HCV, can cause persistent infection for over a decade, with high titers and negative strand RNA in the liver. NPHV is a near-universal contaminant of commercial horse sera for cell culture. The complete NPHV 3'-UTR was determined and consists of interspersed homopolymer tracts and an HCV-like 3'-terminal poly(U)-X-tail. NPHV translation is stimulated by miR-122 and the 3'-UTR and, similar to HCV, the NPHV NS3-4A protease can cleave mitochondrial antiviral-signaling protein to inactivate the retinoic acid-inducible gene I pathway. Using an NPHV consensus cDNA clone, replication was not observed in primary equine fetal liver cultures or after electroporation of selectable replicons. However, intrahepatic RNA inoculation of a horse initiated infection, yielding high RNA titers in the serum and liver. Delayed seroconversion, slightly elevated circulating liver enzymes and mild hepatitis was observed, followed by viral clearance. This establishes the molecular components of a functional NPHV genome. Thus, NPHV appears to resemble HCV not only in genome structure but also in its ability to establish chronic infection with delayed seroconversion and hepatitis. This NPHV infectious clone and resulting acute phase sera will facilitate more detailed studies on the natural history, pathogenesis, and immunity of this novel hepacivirus in its natural host.

Clinical course of infection and viral tissue tropism of hepatitis C virus-like nonprimate hepaciviruses in horses

Hepatitis C virus (HCV) has a very narrow species and tissue tropism and efficiently replicates only in humans and the chimpanzee. Recently, several studies identified close relatives to HCV in different animal species. Among these novel viruses, the nonprimate hepaciviruses (NPHV) that infect horses are the closest relatives of HCV described to date. In this study, we analyzed the NPHV prevalence in northern Germany and characterized the clinical course of infection and viral tissue tropism to explore the relevance of HCV-related horse viruses as a model for HCV infection. We found that approximately 31.4% of 433 horses were seropositive for antibodies (Abs) against NPHV and approximately 2.5% carried viral RNA. Liver function analyses revealed no indication for hepatic impairment in 7 of 11 horses. However, serum gamma-glutamyl transferase (GGT) concentrations were mildly elevated in 3 horses, and 1 horse displayed even highly elevated GGT levels. Furthermore, we observed that NPHV infection could be cleared in individual horses with a simultaneous emergence of nonstructural (NS)3-specific Abs and transient elevation of serum levels of liver-specific enzymes indicative for a hepatic inflammation. In other individual horses, chronic infections could be observed with the copresence of viral RNA and NS3-specific Abs for over 6 months. For the determination of viral tissue tropism, we analyzed different organs and tissues of 1 NPHV-positive horse using quantitative real-time polymerase chain reaction and fluorescent in situ hydridization and detected NPHV RNA mainly in the liver and at lower amounts in other organs.

CONCLUSION

Similar to HCV infections in humans, this work demonstrates acute and chronic stages of NPHV infection in horses with viral RNA detectable predominantly within the liver.