First National Prevalence in Italian Horse Population and Phylogenesis Highlight a Fourth Sub-Type Candidate of Equine Hepacivirus

Equine hepacivirus (EqHV, Flaviviridae, hepacivirus) is a small, enveloped RNA virus generally causing sub-clinical hepatitis with occasional fatalities. EqHV is reported in equids worldwide, but for Italy data are limited. To address this, a survey study was set up to estimate prevalence at a national level and among different production categories (equestrian; competition; work and meat; reproduction) and national macro-regions (North, Central, South, and Islands). Data obtained testing 1801 horse serum samples by Real-Time RT PCR were compared within the categories and regions. The NS3 fragment of the PCR-positive samples was sequenced by Sanger protocol for phylogenetic and mutational analysis. The tertiary structure of the NS3 protein was also assessed. The estimated national prevalence was 4.27% [1.97-6.59, 95% CI] and no statistical differences were detected among production categories and macro-regions. The phylogenesis confirmed the distribution in Italy of the three known EqHV subtypes, also suggesting a possible fourth sub-type that, however, requires further confirmation. Mutational profiles that could also affect the NS3 binding affinity to the viral RNA were detected. The present paper demonstrates that EqHV should be included in diagnostic protocols when investigating causes of hepatitis, and in quality control protocols for blood derived products due to its parental transmission.

Hepatitis C virus infection reduces the lifespan of chimpanzees used in biomedical research

Chimpanzees were used in hepatitis research for over three decades with the aim to identify and develop treatments for the virus, a leading cause of chronic liver disease in humans. We used a dataset of 120 chimpanzees housed at a single institution in Japan, 22 of whom became chronically infected with hepatitis C virus (HCV), to examine whether HCV infection results in a reduced lifespan as reported in humans. Survival analysis showed that HCV carriers experienced a higher mortality risk compared with non-carriers. Although no chimpanzee died from hepatic disease, carriers showed higher gamma-glutamyl transpeptidase (γGTP) levels compared with non-carriers suggesting that HCV infection negatively affected their liver condition. These results provide evidence that special attention is necessary to monitor the long-term condition of ex-biomedical primates.

Geographical Distribution and Genetic Diversity of Bank Vole Hepaciviruses in Europe

The development of new diagnostic methods resulted in the discovery of novel hepaciviruses in wild populations of the bank vole (Myodes glareolus, syn. Clethrionomys glareolus). The naturally infected voles demonstrate signs of hepatitis similar to those induced by hepatitis C virus (HCV) in humans. The aim of the present research was to investigate the geographical distribution of bank vole-associated hepaciviruses (BvHVs) and their genetic diversity in Europe. Real-time reverse transcription polymerase chain reaction (RT-qPCR) screening revealed BvHV RNA in 442 out of 1838 (24.0%) bank voles from nine European countries and in one of seven northern red-backed voles (Myodes rutilus, syn. Clethrionomys rutilus). BvHV RNA was not found in any other small mammal species (n = 23) tested here. Phylogenetic and isolation-by-distance analyses confirmed the occurrence of both BvHV species (Hepacivirus F and Hepacivirus J) and their sympatric occurrence at several trapping sites in two countries. The broad geographical distribution of BvHVs across Europe was associated with their presence in bank voles of different evolutionary lineages. The extensive geographical distribution and high levels of genetic diversity of BvHVs, as well as the high population fluctuations of bank voles and occasional commensalism in some parts of Europe warrant future studies on the zoonotic potential of BvHVs.

No Evidence of Mosquito Involvement in the Transmission of Equine Hepacivirus (Flaviviridae) in an Epidemiological Survey of Austrian Horses

Prevalence studies have demonstrated a global distribution of equine hepacivirus (EqHV), a member of the family Flaviviridae. However, apart from a single case of vertical transmission, natural routes of EqHV transmission remain elusive. Many known flaviviruses are horizontally transmitted between hematophagous arthropods and vertebrate hosts. This study represents the first investigation of potential EqHV transmission by mosquitoes. More than 5000 mosquitoes were collected across Austria and analyzed for EqHV ribonucleic acid (RNA) by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Concurrently, 386 serum samples from horses in eastern Austria were analyzed for EqHV-specific antibodies by luciferase immunoprecipitation system (LIPS) and for EqHV RNA by RT-qPCR. Additionally, liver-specific biochemistry parameters were compared between EqHV RNA-positive horses and EqHV RNA-negative horses. Phylogenetic analysis was conducted in comparison to previously published sequences from various origins. No EqHV RNA was detected in mosquito pools. Serum samples yielded an EqHV antibody prevalence of 45.9% (177/386) and RNA prevalence of 4.15% (16/386). EqHV RNA-positive horses had significantly higher glutamate dehydrogenase (GLDH) levels (p = 0.013) than control horses. Phylogenetic analysis showed high similarity between nucleotide sequences of EqHV in Austrian horses and EqHV circulating in other regions. Despite frequently detected evidence of EqHV infection in Austrian horses, no viral RNA was found in mosquitoes. It is therefore unlikely that mosquitoes are vectors of this flavivirus.

Highly divergent cattle hepacivirus N in Southern Brazil

The genus Hepacivirus includes 14 species (Hepacivirus A-N). In this study, we determined a partial genome sequence of a highly divergent bovine hepacivirus (hepacivirus N, HNV) isolate from cattle in Southern Brazil. Previously described HNV isolates have shared 80-99.7% nucleotide sequence identity in the NS3 coding region. However, the sequence determined in this study had 72.6% to 73.8% nucleotide sequence identity to known HNV NS3 sequences. This high divergence could be seen in a phylogenetic tree, suggesting that it represents a new genotype of HNV. These data expand our knowledge concerning the genetic variability and evolution of hepaciviruses.

Frequent occurrence of nonprimate hepacivirus infections in Thoroughbred breeding horses - A cross-sectional study for the occurrence of infections and potential risk factors

Recently, several new hepaciviruses have been identified of which the nonprimate hepacivirus (NPHV) - the closest relative to hepatitis C virus (HCV) discovered to date - is highly prevalent in horses. However, potential risk factors for the transmission of NPHV among horses remain still unknown. Therefore, the objective of this study was to investigate the occurrence of NPHV infections in Thoroughbreds in northern and western Germany and to identify potential risk factors associated with NPHV infections. Using a cross-sectional study design, a total of 733 serum samples from Thoroughbred broodmares and stallions from northern and western Germany were analyzed for the presence of anti-NPHV nonstructural protein 3 (NS3) antibodies and NPHV RNA using the luciferase immunoprecipitation system (LIPS) and a quantitative real-time PCR, respectively. Information regarding signalment, stud farm, breeding history and international transportation history of each horse were collected and evaluated. A frequent occurrence of NPHV was found in the study population with 453 seropositive horses (61.8%) and 134 horses (18.3%) carrying NPHV RNA. Furthermore, statistical analysis revealed that the probability of being infected decreased for horses with a transportation history with increasing age by 20% each year. For horses that stayed in Germany no association between age and infection could be observed. In conclusion, the high occurrence of NPHV infections in breeding Thoroughbreds suggests circulating NPHV infections, endemic herds or persistent shedding in these animals and revealed the association of age and international transportation as risk factor for NPHV infections.

Identification and characterization of toll-like receptors (TLRs) in the Chinese tree shrew (Tupaia belangeri chinensis)

In mammals, the toll-like receptors (TLRs) play a major role in initiating innate immune responses against pathogens. Comparison of the TLRs in different mammals may help in understanding the TLR-mediated responses and developing of animal models and efficient therapeutic measures for infectious diseases. The Chinese tree shrew (Tupaia belangeri chinensis), a small mammal with a close relationship to primates, is a viable experimental animal for studying viral and bacterial infections. In this study, we characterized the TLRs genes (tTLRs) in the Chinese tree shrew and identified 13 putative TLRs, which are orthologs of mammalian TLR1-TLR9 and TLR11-TLR13, and TLR10 was a pseudogene in tree shrew. Positive selection analyses using the Maximum likelihood (ML) method showed that tTLR8 and tTLR9 were under positive selection, which might be associated with the adaptation to the pathogen challenge. The mRNA expression levels of tTLRs presented an overall low and tissue-specific pattern, and were significantly upregulated upon Hepatitis C virus (HCV) infection. tTLR4 and tTLR9 underwent alternative splicing, which leads to different transcripts. Phylogenetic analysis and TLR structure prediction indicated that tTLRs were evolutionarily conserved, which might reflect an ancient mechanism and structure in the innate immune response system. Taken together, TLRs had both conserved and unique features in the Chinese tree shrew.

Single-Genome Sequencing of Hepatitis C Virus in Donor-Recipient Pairs Distinguishes Modes and Models of Virus Transmission and Early Diversification

Despite the recent development of highly effective anti-hepatitis C virus (HCV) drugs, the global burden of this pathogen remains immense. Control or eradication of HCV will likely require the broad application of antiviral drugs and development of an effective vaccine. A precise molecular identification of transmitted/founder (T/F) HCV genomes that lead to productive clinical infection could play a critical role in vaccine research, as it has for HIV-1. However, the replication schema of these two RNA viruses differ substantially, as do viral responses to innate and adaptive host defenses. These differences raise questions as to the certainty of T/F HCV genome inferences, particularly in cases where multiple closely related sequence lineages have been observed. To clarify these issues and distinguish between competing models of early HCV diversification, we examined seven cases of acute HCV infection in humans and chimpanzees, including three examples of virus transmission between linked donors and recipients. Using single-genome sequencing (SGS) of plasma vRNA, we found that inferred T/F sequences in recipients were identical to viral sequences in their respective donors. Early in infection, HCV genomes generally evolved according to a simple model of random evolution where the coalescent corresponded to the T/F sequence. Closely related sequence lineages could be explained by high multiplicity infection from a donor whose viral sequences had undergone a pretransmission bottleneck due to treatment, immune selection, or recent infection. These findings validate SGS, together with mathematical modeling and phylogenetic analysis, as a novel strategy to infer T/F HCV genome sequences.

IMPORTANCE

Despite the recent development of highly effective, interferon-sparing anti-hepatitis C virus (HCV) drugs, the global burden of this pathogen remains immense. Control or eradication of HCV will likely require the broad application of antiviral drugs and the development of an effective vaccine, which could be facilitated by a precise molecular identification of transmitted/founder (T/F) viral genomes and their progeny. We used single-genome sequencing to show that inferred HCV T/F sequences in recipients were identical to viral sequences in their respective donors and that viral genomes generally evolved early in infection according to a simple model of random sequence evolution. Altogether, the findings validate T/F genome inferences and illustrate how T/F sequence identification can illuminate studies of HCV transmission, immunopathogenesis, drug resistance development, and vaccine protection, including sieving effects on breakthrough virus strains.

IL-29 is the dominant type III interferon produced by hepatocytes during acute hepatitis C virus infection

Early, vigorous intrahepatic induction of interferon (IFN)-stimulated gene (ISG) induction is a feature of hepatitis C virus (HCV) infection, even though HCV inhibits the induction of type I IFNs in vitro. To identify the cytokines and cells that drive ISG induction and mediate antiviral activity during acute HCV infection, type I and III IFN responses were studied in (1) serial liver biopsies and plasma samples obtained from 6 chimpanzees throughout acute HCV infection and (2) primary human hepatocyte (PHH) cultures upon HCV infection. Type I IFNs were minimally induced at the messenger RNA (mRNA) level in the liver and were undetectable at the protein level in plasma during acute HCV infection of chimpanzees. In contrast, type III IFNs, in particular, interleukin (IL)-29 mRNA and protein, were strongly induced and these levels correlated with ISG expression and viremia. However, there was no association between intrahepatic or peripheral type III IFN levels and the outcome of acute HCV infection. Infection of PHH with HCV recapitulated strong type III and weak type I IFN responses. Supernatants from HCV-infected PHH cultures mediated antiviral activity upon transfer to HCV-replicon-containing cells. This effect was significantly reduced by neutralization of type III IFNs and less by neutralization of type I IFNs. Furthermore, IL-29 production by HCV-infected PHH occurred independently from type I IFN signaling and was not enhanced by the presence of plasmacytoid dendritic cells.

CONCLUSION

Hepatocyte-derived type III IFNs contribute to ISG induction and antiviral activity, but are not the principal determinant of the outcome of HCV infection.

Efficient infection of tree shrew (Tupaia belangeri) with hepatitis C virus grown in cell culture or from patient plasma

The generation of a new, cost-effective, non-primate, small-animal model would greatly facilitate research into hepatitis C virus (HCV) pathogenesis and the development of novel therapeutic and preventative technologies to control the increasing HCV threat to public health. Native HCV from patient plasma and HCV grown in cell culture (HCVcc) were used to inoculate adult tree shrews. Each animal was inoculated with one HCV genotype. Alanine aminotransferase (ALT) levels, HCV RNA and viral load were determined in the animals before and after inoculation. For native HCV, 16/18 inoculated tree shrews (89 %) became infected; 12/16 (75 %) of these animals became chronically infected, whilst infection was resolved in the remaining four (25 %). For HCVcc, infection occurred in 10/12 inoculated tree shrews (83 %) and chronic infection was observed in two of these animals. HCVcc from Huh7 cells showed a higher infectivity than that from HeLa cells. The animals inoculated with inadequate amounts of HCV were not infected in either native HCV or HCVcc experiments. Peak viral loads reached 10(3)-10(5) international units ml(-1) in chronically infected animals. ALT level changes reflected the normal fluctuation range in most animals. Thus, tree shrews without immunosuppression can be infected efficiently by native HCV and HCVcc when the animal is inoculated with an adequate amount of single-genotype HCV.

Analysis of the complete genomic sequence of an apparently avirulent strain of avian hepatitis E virus (avian HEV) identified major genetic differences compared with the prototype pathogenic strain of avian HEV

Avian hepatitis E virus (HEV) was identified from chickens with hepatitis-splenomegaly syndrome. In this study, the complete genomic sequence of an apparently avirulent strain of avian HEV was determined to be 6649 nt in length, excluding the poly(A) tail, which is 5 nt shorter than the prototype avian HEV. Sequence analyses revealed that the ORF1 has 89.6% nucleotide sequence identity, with numerous non-silent mutations and deletions, compared to the prototype strain. The ORF2 capsid gene showed 90.7% sequence identity with six non-silent mutations, and ORF3 had four non-silent mutations with 97% sequence identity. Overall, the apparently avirulent strain shares only 90.1% nucleotide sequence identity with the prototype strain. The identification of significant non-silent mutations in the capsid gene and other regions suggests that these mutations may play a role in HEV attenuation. This is the first report of the full-length sequence of an apparently avirulent strain of HEV.

CD4+ immune escape and subsequent T-cell failure following chimpanzee immunization against hepatitis C virus

Hepatitis C is a major cause of chronic liver disease, with 170 million individuals infected worldwide and no available vaccine. We analyzed the effects of an induced T-cell response in 3 chimpanzees, targeting nonstructural proteins in the absence of neutralizing antibodies. In all animals the specific T-cell response modified the outcome of infection, producing a 10- to 1,000-fold reduction in peak virus titers. The challenge of 2 immunized animals that had been previously exposed to hepatitis C virus resulted in subclinical infections. Immune responses in the third animal, naive prior to immunization, limited viral replication immediately, evidenced by a 30-fold reduction in virus titer by week 2, declining to a nonquantifiable level by week 6. After 10 weeks of immunological control, we observed a resurgence of virus, followed by progression to a persistent infection. Comparing virus evolution with T-cell recognition, we demonstrated that: (i) resurgence was concomitant with the emergence of new dominant viral populations bearing single amino acid changes in the NS3 and NS5A regions, (ii) these mutations resulted in a loss of CD4+ T-cell recognition, and (iii) subsequent to viral resurgence and immune escape a large fraction of NS3-specific T cells became impaired in their ability to secrete IFN-gamma and proliferate. In contrast, NS3-specific responses were sustained in the recovered/immunized animals presenting with subclinical infections. In conclusion, viral escape from CD4+ T cells can result in the eventual failure of an induced T-cell response that initially controls infection. Vaccines that can induce strong T-cell responses prior to challenge will not necessarily prevent persistent HCV infection.

Hepatitis C virus kinetics and host responses associated with disease and outcome of infection in chimpanzees

To study determinants of clinical outcome following HCV infection, viral kinetics, immune events, and intrahepatic cytokine markers were compared in 10 naive chimpanzees. Four of the animals cleared HCV; 6 developed persistent infections. All animals developed similar acute infections with increasing viremia from 1 to 2 weeks, followed by alanine aminotransferase (ALT) elevations and seroconversion. This viremia pattern consisted of a biphasic increase, a rapid slope (mean doubling time [t(2)] = 0.5 days) followed by a slower slope after the second week (t(2) = 7.5 days). This slowing of virus replication correlated in all animals with increased intrahepatic 2'5' oligoadenylate synthetase 1 (2OAS-1) messenger RNA (mRNA) levels and was independent of disease outcome. An effective control of virus replication was observed following increases in intrahepatic interferon gamma (IFN-gamma) mRNA and ALT levels. Although this control was associated in all animals with a 2-log decrease in virus titer, the timing occurred approximately 2 weeks later in the chronic group (P <.05). Additionally, while cleared infections were characterized by a continual decrease in virus titer, the titers in the persistent infections reached a steady state level of 10(4) to 10(5) RNA copies/mL. This inability of the immune response to sustain viral clearance in the persistent infections was associated with a reduced intrahepatic CD3e and monocyte-induced protein 1alpha (MIP-1alpha) mRNA induction. In conclusion, these data indicate that, regardless of outcome, chimpanzees generate responses that control HCV replication during the early and late acute phase. However, the pathogenesis of HCV may be determined by a more rapid onset of the induced response and the cell population that migrates to the liver.

Hepatitis C virus replication kinetics in chimpanzees with self-limited and chronic infections

The availability of molecular beacon-based, real time polymerase chain reaction (PCR) and a semi-automated sample extraction procedure have made it possible for us to retrospectively examine HCV replication kinetics in HCV naive chimpanzees infected during the past 20 years. We compared these in 17 animals that developed chronic infection, and in 21 that developed self-limited infection. No differences were found in infecting dose, or replication kinetics in the acute phase between these two types of infection. An unanticipated finding was the fact that 10 of 17 animals developing chronic infection partially controlled virus replication for 48 +/- 48 weeks after typical acute phase viraemia, and prior to development of chronic infection. Twenty-nine out of 30 (29/30) sera, which were negative by quantitative PCR during the downregulated period, were, however, positive by the more sensitive Genprobe isothermal transcription-mediated amplification (TMA) assay. Thus, downregulation was not complete. Ten animals showing self-limited infection showed complete resolution of viraemia by TMA assay. Quasispecies analysis revealed that in all, except one case, the virus reappearing after downregulation was essentially identical to that of the originally infecting virus.

Occurrence of hepatitis viruses in wild-born non-human primates: a 3 year (1998-2001) epidemiological survey in Gabon

Hepatitis B and C infections are endemic in human population in central Africa, particularly in Gabon. The aim of this study was to determine the prevalence of hepatitis B virus (HBV) and eventual occurrence of hepatitis C virus (HBC)-related strains in a variety of wild-born non-human primates living in Gabon and Congo. Plasma samples were screened for HBV and HCV markers. A non-invasive method of DNA extraction from faeces followed by specific HBV-DNA amplification was developed to study this infection in wild troops of chimpanzees and gorillas. No HCV infection in non-human primates, wild-born or captive, was detected among 596 samples tested. No HBV infection could be detected in samples tested and obtained from Cercopithecidae. In contrast, 14.7 and 42.2% of wild-born chimpanzees in Gabon and Congo were infected with HBV or had evidence of past HBV infection. At Centre International de Recherches Médicales (CIRMF) Primate Centre, 32.1% of chimpanzees and gorillas were HBV positive or had evidence of past infection. In the cases with past infection, 5.9% wild-born and 8.3% at CIRMF harboured HBV-DNA despite the presence of neutralizing HbsAb. Together with previous findings, we confirm the high HBV prevalence not only in humans but also in chimpanzees and gorillas in Gabon and Congo.

Memory CD8+ T cells are required for protection from persistent hepatitis C virus infection

Few hepatitis C virus (HCV) infections resolve spontaneously but those that do appear to afford protective immunity. Second infections are usually shorter in duration and are less likely to persist but mechanisms of virus control in immune individuals have not been identified. In this study we investigated whether memory helper and/or cytotoxic T lymphocytes provide protection in chimpanzees serially reinfected with the virus. Clearance of the first infection took 3-4 mo and coincided with the delayed onset of CD4+ and CD8+ T cell responses. High frequencies of memory T cells targeting multiple HCV proteins were stable over 7 yr of follow-up. Animals were infected for a second time to assess the protective role of memory T cells. In contrast to the prolonged course of the first infection, viremia was terminated within 14 d. Control of this second infection was kinetically linked to rapid acquisition of virus-specific cytolytic activity by liver resident CD8+ T cells and expansion of memory CD4+ and CD8+ T cells in blood. The importance of memory CD8+ T cells in control of HCV infection was confirmed by antibody-mediated depletion of this lymphocyte subset before a third infection. Virus replication was prolonged despite the presence of memory CD4+ T helper cells primed by the two prior infections and was not terminated until HCV-specific CD8+ T cells recovered in the liver. These experiments demonstrate an essential role for memory CD8+ T cells in long-term protection from chronic hepatitis C.

Seropositivity to HCV in Macaca fascicularis

Several non-human primate species are used as laboratory animals for research purposes. Non human primates represent a potential hazard for laboratory animal handlers as they exceed all other species in importance as potentiators of disease in laboratory personnel (Quist K.D., 1972). Hepatitis viruses cause some of the prevalent diseases in man which constitute an important public health problem. The first outbreak of the infection was related to non human primates and occurred in 1958-1960 in USA, with more then 200 human cases. Chimpanzee is the main species that has been implicated but others have also been involved. We report a case of seropositivity to HCV antigens in Macaca fascicularis using a third generation RIBA assay. The nature of reactivity of the positive samples could not be resolved as no animal in the breeder colony had been exposed to an HCV source. Furthermore, Macaca spp. did not appear to be a susceptible species in previous studies.

Failure to infect rhesus monkeys with hepatitis C virus strains of genotypes 1a, 2a or 3a

The chimpanzee is the only recognized animal model for the study of hepatitis C virus (HCV). However, recently it was reported that rhesus monkeys were susceptible to HCV and developed hepatitis during infection. In the present study, we inoculated two rhesus monkeys each with HCV strain H77 (genotype 1a), strain HC-J6 (genotype 2a) or strain S52 (genotype 3a). Weekly serum samples were tested for liver enzyme values, HCV antibodies and HCV RNA. We did not find evidence of HCV infection in any of the monkeys during 24 weeks of follow-up. Our study demonstrates that rhesus monkeys are not readily infected with HCV and apparently do not represent a useful animal model for the study of HCV.

Altered lymphocyte phenotypes and proliferative responses in chimpanzees infected with hepatitis C virus

Peripheral blood mononuclear cells (MNC) from three chimpanzees infected with hepatitis C virus (HCV) and from two uninfected animals were analyzed by monoclonal antibody phenotyping using flow cytometry. Significant differences in numbers of MNC's expressing cluster designation (CD) phenotypes CD4, CD14, CD19, and CD45RA were found. Additionally, significant differences in MNC proliferation in response to mitogens were also found. This altered proliferative capacity and cellular phenotype profile may be important markers in studying the pathogenesis of chronic HCV disease.

Lymphocyte and neutrophil dysfunction associated with hepatitis B virus and hepatitis non-A, non-B virus infection in the chimpanzee

Chimpanzees were examined for the effect of viral hepatitis infections on specific and nonspecific immune response mechanisms. The data suggest that infection with either hepatitis B virus or hepatitis non-A, non-B virus may result in suppression of cellular immune response components. Mitogen-induced lymphocyte proliferation was lower in virus-infected chimpanzees than in naive animals. Neutrophils from virus infected animals exhibited decreased or altered chemiluminescence kinetics.

Evaluation of a chimpanzee colony for antibodies to hepatitis C virus

The chimpanzee is the only species other than man that is generally susceptible to infection by hepatitis C virus (HCV). Aspects of future studies on vaccines and therapeutics for HCV may continue to depend on the chimpanzee. In an attempt to determine the HCV status of the animals in a chimpanzee colony, the recently developed enzyme immunoassay (EIA) for antibodies to HCV was used. The results of the assay indicated that only 31.3% of the animals that had previously been inoculated with a non-A, non-B hepatitis agent were currently positive in the assay. A retrospective analysis suggested that an additional 20% of the chimpanzees had been positive at some time following infection. Seroconversion to an anti-HCV antibody response using this assay did not appear to correlate with the severity of the initial disease or the development of chronic liver damage. Examination of the EIA-positive samples using the second generation recombinant immunoblot assay (RIBA) containing four HCV antigens suggested that chimpanzees responded differentially to these antigens. Examination of serum samples from 139 uninoculated animals by EIA revealed seven positive samples and ten samples with borderline values. The nature of the reactivities in most of the positive samples could not be resolved, but analysis by RIBA indicated that at least one animal in the breeder colony had been exposed to HCV. Due to the low seroconversion rate and the uncertainties surrounding many of the positive reactions, this assay cannot be used to determine the initial source or extent of spread of HCV infections in the uninoculated animals.

Application of electron microscopy to the study of structural changes in the liver in non-A, non-B hepatitis

Ultrastructural studies employing techniques such as alternative electron metal stain, high-angle tilting and high-voltage electron microscopy were carried out on liver biopsies obtained from chimpanzees infected with non-A, non-B hepatitis. Typical derangement of the endoplasmic reticulum leading to the formation of tubular structures in hepatocytes was observed. The use of potassium permanganate as an alternative stain revealed two features which have not been previously described. The first of these shows the wall of the tubular structures to be composed of a well-defined fibrillar-like meshwork with a periodicity of approximately 15 nm. The second feature is the demonstration of clusters of fibrin-like inclusions consisting of striated fibrils in the neighborhood of the tubular structures. The presence of intracytoplasmic fibrin may indicate non-specific morphological evidence of cell injury. Crystalline structures containing arrays of particles with an average size of 24 nm were also observed in the endoplasmic reticulum of endothelial cells of the hepatic sinusoids. Morphological differences between the crystalline lattice and the reticular arrangement, demonstrated with the use of high-angle tilting of the specimen in the electron microscopy suggest that the arrays may not be viral particules but a reflection of pathological response of the host cell.