Autonomous circadian rhythms in the human hepatocyte regulate hepatic drug metabolism and inflammatory responses

Critical aspects of physiology and cell function exhibit self-sustained ~24-hour variations termed circadian rhythms. In the liver, circadian rhythms play fundamental roles in maintaining organ homeostasis. Here, we established and characterized an in vitro liver experimental system in which primary human hepatocytes display self-sustained oscillations. By generating gene expression profiles of these hepatocytes over time, we demonstrated that their transcriptional state is dynamic across 24 hours and identified a set of cycling genes with functions related to inflammation, drug metabolism, and energy homeostasis. We designed and tested a treatment protocol to minimize atorvastatin- and acetaminophen-induced hepatotoxicity. Last, we documented circadian-dependent induction of pro-inflammatory cytokines when triggered by LPS, IFN-β, or Plasmodium infection in human hepatocytes. Collectively, our findings emphasize that the phase of the circadian cycle has a robust impact on the efficacy and toxicity of drugs, and we provide a test bed to study the timing and magnitude of inflammatory responses over the course of infection in human liver.

Pan-Genotype Hepatitis E Virus Replication in Stem Cell-Derived Hepatocellular Systems

BACKGROUND & AIMS

The 4 genotypes of hepatitis E virus (HEV) that infect humans (genotypes 1-4) vary in geographical distribution, transmission, and pathogenesis. Little is known about the properties of HEV or its hosts that contribute to these variations. Primary isolates grow poorly in cell culture; most studies have relied on variants adapted to cancer cell lines, which likely alter virus biology. We investigated the infection and replication of primary isolates of HEV in hepatocyte-like cells (HLCs) derived from human embryonic and induced pluripotent stem cells.

METHODS

Using a cell culture-adapted genotype 3 strain and primary isolates of genotypes 1 to 4, we compared viral replication kinetics, sensitivity to drugs, and ability of HEV to activate the innate immune response. We studied HLCs using quantitative reverse-transcriptase polymerase chain reaction and immunofluorescence assay and enzyme-linked immunosorbent assays. We used an embryonic stem cell line that can be induced to express the CRISPR-Cas9 machinery to disrupt the peptidylprolyl isomerase A gene, encoding cyclophilin A (CYPA), a protein reported to inhibit replication of cell culture-adapted HEV. We further modified this line to rescue expression of CYPA before terminal differentiation to HLCs and performed HEV infection studies.

RESULTS

HLCs were permissive for infection by nonadapted, primary isolates of HEV genotypes 1 to 4. HEV infection of HLCs induced a replication-dependent type III interferon response. Replication of primary HEV isolates, unlike the cell culture-adapted strain, was not affected by disruption of the peptidylprolyl isomerase A gene or exposure to the CYPA inhibitor cyclosporine A.

CONCLUSIONS

Cell culture adaptations alter the replicative capacities of HEV. HLCs offer an improved, physiologically relevant, and genetically tractable system for studying the replication of primary HEV isolates. HLCs could provide a model to aid development of HEV drugs and a system to guide personalized regimens, especially for patients with chronic hepatitis E who have developed resistance to ribavirin.

Intrinsic Immunity Shapes Viral Resistance of Stem Cells

Stem cells are highly resistant to viral infection compared to their differentiated progeny; however, the mechanism is mysterious. Here, we analyzed gene expression in mammalian stem cells and cells at various stages of differentiation. We find that, conserved across species, stem cells express a subset of genes previously classified as interferon (IFN) stimulated genes (ISGs) but that expression is intrinsic, as stem cells are refractory to interferon. This intrinsic ISG expression varies in a cell-type-specific manner, and many ISGs decrease upon differentiation, at which time cells become IFN responsive, allowing induction of a broad spectrum of ISGs by IFN signaling. Importantly, we show that intrinsically expressed ISGs protect stem cells against viral infection. We demonstrate the in vivo importance of intrinsic ISG expression for protecting stem cells and their differentiation potential during viral infection. These findings have intriguing implications for understanding stem cell biology and the evolution of pathogen resistance.

Humanized mice efficiently engrafted with fetal hepatoblasts and syngeneic immune cells develop human monocytes and NK cells

BACKGROUND & AIMS

Human liver chimeric mice are useful models of human hepatitis virus infection, including hepatitis B and C virus infections. Independently, immunodeficient mice reconstituted with CD34(+) hematopoietic stem cells (HSC) derived from fetal liver reliably develop human T and B lymphocytes. Combining these systems has long been hampered by inefficient liver reconstitution of human fetal hepatoblasts. Our study aimed to enhance hepatoblast engraftment in order to create a mouse model with syngeneic human liver and immune cells.

METHODS

The effects of human oncostatin-M administration on fetal hepatoblast engraftment into immunodeficient fah(-/-) mice was tested. Mice were then transplanted with syngeneic human hepatoblasts and HSC after which human leukocyte chimerism and functionality were analyzed by flow cytometry, and mice were challenged with HBV.

RESULTS

Addition of human oncostatin-M enhanced human hepatoblast engraftment in immunodeficient fah(-/-) mice by 5-100 fold. In contrast to mice singly engrafted with HSC, which predominantly developed human T and B lymphocytes, mice co-transplanted with syngeneic hepatoblasts also contained physiological levels of human monocytes and natural killer cells. Upon infection with HBV, these mice displayed rapid and sustained viremia.

CONCLUSIONS

Our study provides a new mouse model with improved human fetal hepatoblast engraftment and an expanded human immune cell repertoire. With further improvements, this model may become useful for studying human immunity against viral hepatitis.

LAY SUMMARY

Important human pathogens such as hepatitis B virus, hepatitis C virus and human immunodeficiency virus only infect human cells which complicates the development of mouse models for the study of these pathogens. One way to make mice permissive for human pathogens is the transplantation of human cells into immune-compromised mice. For instance, the transplantation of human liver cells will allow the infection of these so-called "liver chimeric mice" with hepatitis B virus and hepatitis C virus. The co-transplantation of human immune cells into liver chimeric mice will further allow the study of human immune responses to hepatitis B virus or hepatitis C virus. However, for immunological studies it will be crucial that the transplanted human liver and immune cells are derived from the same human donor. In our study we describe the efficient engraftment of human fetal liver cells and immune cells derived from the same donor into mice. We show that liver co-engraftment resulted in an expanded human immune cell repertoire, including monocytes and natural killer cells in the liver. We further demonstrate that these mice could be infected with hepatitis B virus, which lead to an expansion of natural killer cells. In conclusion we have developed a new mouse model that could be useful to study human immune responses to human liver pathogens.

Expression of paramyxovirus V proteins promotes replication and spread of hepatitis C virus in cultures of primary human fetal liver cells

Here we demonstrate that primary cultures of human fetal liver cells (HFLC) reliably support infection with laboratory strains of hepatitis C virus (HCV), although levels of virus replication vary significantly between different donor cell preparations and frequently decline in a manner suggestive of active viral clearance. To investigate possible contributions of the interferon (IFN) system to control HCV infection in HFLC, we exploited the well-characterized ability of paramyxovirus (PMV) V proteins to counteract both IFN induction and antiviral signaling. The V proteins of measles virus (MV) and parainfluenza virus 5 (PIV5) were introduced into HFLC using lentiviral vectors encoding a fluorescent reporter for visualization of HCV-infected cells. V protein-transduced HFLC supported enhanced (10 to 100-fold) levels of HCV infection relative to untransduced or control vector-transduced HFLC. Infection was assessed by measurement of virus-driven luciferase, by assays for infectious HCV and viral RNA, and by direct visualization of HCV-infected hepatocytes. Live cell imaging between 48 and 119 hours postinfection demonstrated little or no spread of infection in the absence of PMV V protein expression. In contrast, V protein-transduced HFLC showed numerous HCV infection events. V protein expression efficiently antagonized the HCV-inhibitory effects of added IFNs in HFLC. In addition, induction of the type III IFN, IL29, following acute HCV infection was inhibited in V protein-transduced cultures.

CONCLUSION

These studies suggest that the cellular IFN response plays a significant role in limiting the spread of HCV infection in primary hepatocyte cultures. Strategies aimed at dampening this response may be key to further development of robust HCV culture systems, enabling studies of virus pathogenicity and the mechanisms by which HCV spreads in its natural host cell population.

Hepatitis C virus induces interferon-λ and interferon-stimulated genes in primary liver cultures

Hepatitis C virus (HCV) replication in primary liver cells is less robust than that in hepatoma cell lines, suggesting that innate antiviral mechanisms in primary cells may limit HCV replication or spread. Here we analyzed the expression of 47 genes associated with interferon (IFN) induction and signaling following HCV infection of primary human fetal liver cell (HFLC) cultures from 18 different donors. We report that cell culture-produced HCV (HCVcc) induced expression of Type III (λ) IFNs and of IFN-stimulated genes (ISGs). Little expression of Type I IFNs was detected. Levels of IFNλ and ISG induction varied among donors and, often, between adapted and nonadapted HCV chimeric constructs. Higher levels of viral replication were associated with greater induction of ISGs and of λ IFNs. Gene induction was dependent on HCV replication, as ultraviolet light-inactivated virus was not stimulatory and an antiviral drug, 2'-C-methyladenosine, reduced induction of λ IFNs and ISGs. The level of IFNλ protein induced was sufficient to inhibit HCVcc infection of naïve cultures.

CONCLUSION

Together, these results indicate that despite its reported abilities to blunt the induction of an IFN response, HCV infection is capable of inducing antiviral cytokines and pathways in primary liver cell cultures. Induction of ISGs and λ IFNs may limit the growth and spread of HCV in primary cell cultures and in the infected liver. HCV infection of HFLC may provide a useful model for the study of gene induction by HCV in vivo.

Cell culture-produced hepatitis C virus does not infect peripheral blood mononuclear cells

Hepatitis C virus (HCV) replicates primarily in the liver, but HCV RNA has been observed in association with other tissues and cells including B and T lymphocytes, monocytes, and dendritic cells. We have taken advantage of a recently described, robust system that fully recapitulates HCV entry, replication and virus production in vitro to re-examine the issue of HCV infection of blood cell subsets. The HCV replicase inhibitor 2'C-methyl adenosine was used to distinguish HCV RNA replication from RNA persistence. Whereas cell culture-grown HCV replicated in Huh-7.5 hepatoma cells, no HCV replication was detected in B or T lymphocytes, monocytes, macrophages, or dendritic cells from healthy donors. No blood cell subset tested expressed significant levels of Claudin-1, a tight junction protein needed for HCV infection of Huh-7.5 cells. A B cell line expressing high levels of Claudin-1, CD81, and scavenger receptor BI remained resistant to HCV pseudoparticle infection. We bypassed the block in HCV entry by transfecting HCV RNA into blood cell subsets. Transfected RNA was not detectably translated and induced high levels of interferon-alpha. Supernatants from HCV RNA-transfected macrophages inhibited HCV replication in Huh-7.5 cells.

CONCLUSION

We conclude that multiple blocks prevent blood cells from supporting HCV infection.

Individual donor nucleic acid amplification testing for detection of West Nile virus

We have developed an economical, high-throughput nucleic acid amplification test (NAT) for blood-borne viruses, suitable for use in the screening of plasma samples from individual blood donors. This assay system includes a semiautomated procedure, using 96-well glass fiber plates for the extraction of viral nucleic acids from plasma and "universal beacon" technology which permits the detection of all genotypes of highly variable viruses (e.g., human immunodeficiency virus and hepatitis C virus). In this detection system, two fluorescent- detection technologies were employed successfully in a single tube: molecular beacon for West Nile virus (WNV) detection using a 6-carboxyfluorescein fluorophore and TaqMan for internal control detection using a VIC fluorophore. To establish proof of concept, we focused on the development of a robust individual donor NAT for WNV. The assay showed no reactivity to 15 other viruses tested or to 420 blood donor samples from the WNV pre-epidemic season. No cross-contamination was observed on an alternating positive-/negative-well test. The sensitivity (limit of detection, 95%) of the assay for WNV is between 3.79 and 16.3 RNA copies/ml, depending on which material was used as a standard. The assay detected all positive blood donation samples identified by the Roche WNV NAT. The assay can be performed qualitatively for screening and quantitatively for confirmation.

Protection against chronic hepatitis C virus infection after rechallenge with homologous, but not heterologous, genotypes in a chimpanzee model

An open question for hepatitis C virus (HCV) vaccine development is whether the various genotypes of this virus protect against the development of chronic infection after heterologous infection with different genotypes. We approached this question by challenging chimpanzees that had recovered from HCV genotype 1a or 1b infection with 6 heterologous genotypes as well as with a homologous genotype (for chimpanzees originally infected with genotype 1a). All 9 chimpanzees rechallenged with a homologous genotype developed self-limited infections. Of 11 chimpanzees challenged with 100 chimpanzee infectious doses of heterologous genotypes, 6 developed self-limited infections, with peak viral loads in acute-phase serum that were ~5-fold lower than those seen during primary infections. One chimpanzee (which had recovered from genotype 1b infection and was rechallenged with genotype 6a) did not develop viremia but did show an anamnestic cell-mediated immune response after rechallenge. Four of the 11 chimpanzees rechallenged with heterologous genotypes developed chronic infections with the genotypes used for rechallenge. These findings suggest that a universally protective HCV vaccine may need to incorporate epitopes from multiple genotypes.

Characterization of the immune response against hepatitis C infection in recovered, and chronically infected chimpanzees

The immune response to hepatitis C virus (HCV) is believed to be critical in determining the outcome of the disease. In this study we have analysed epitope recognition, cytokine profile, and anti-HCV antibody responses in chronically HCV-infected and recovered chimpanzees. Quantitative measurement of anti-HCV antibody in HCV-infected chimpanzees revealed that the response in HCV- recovered chimpanzees peaked within 4-20 weeks. In contrast, the anti-HCV antibody responses in chronically HCV infected chimpanzees did not peak until 100-200 weeks after infection, and decreased gradually thereafter. T cell proliferation assays measuring responses to pooled HCV proteins revealed significant increases in the 3H-uptake during the early stages of infection in recovered chimpanzees in comparison to the chronically infected ones. Class I-restricted epitopes of the core, and NS3 proteins of HCV were analysed using 9-10 mer overlapping peptides covering the core and NS3 proteins, and IFN-gamma ELISPOT technique. Our data indicated early and broad class-I restricted core, and NS3 protein epitope recognitions in HCV-recovered chimpanzees but not in chimpanzees that had been chronically infected. Additionally, dominant epitopes recognized early in infection (8 weeks) were no longer recognized later in infection (followed up to 64 weeks). Cytokines profiling revealed a 50-fold increase in TNF-alpha secretion in the supernatant of core-specific CD8 memory cells of the chronically infected chimpanzees in comparison to the recovered ones. In summary, multiple parameters correlate with HCV recovery in chimpanzees.

Lack of evidence for HIV type 1-related SIVcpz infection in captive and wild chimpanzees (Pan troglodytes verus) in West Africa

Serum from 387 chimpanzees (Pan troglodytes verus), caught in the wild or bred in captivity, was tested for antibody to HIV-1 and HIV-2, using second- and third-generation enzyme immunoassays. Six samples were repeatedly positive; however, only one of these was Western blot positive. Serial sera drawn before and after the Western blot-positive samples were seronegative, and thus we conclude that this sample represented specimen contamination, or mislabeling. Thus, none of the 387 Pan troglodytes verus from West Africa were spontaneously infected with SIVcpz. Chimpanzees are known to be exquisitely susceptible to infection with HIV-1 when experimentally inoculated, and thus our findings suggest that HIV-1-related viruses do not exist in Pan troglodytes verus in the wild. As it has been convincingly shown that SIVcpz exists in wild Pan troglodytes troglodytes in Central Africa, this suggests that HIV-1 arose in Central Africa, but not in West Africa.

Stabilized viral nucleic acids in plasma as an alternative shipping method for NAT

BACKGROUND

Preservation of the integrity of viral nucleic acids in blood specimens during shipping and handling is crucial for NAT and viral load monitoring. An economical and convenient method is described for nucleic acid stabilization by using an RNA stabilizing solution (RNAlater, Ambion) in plasma that is designed for the shipment of samples to tropical countries.

STUDY DESIGN AND METHODS

HCV, HIV, and HBV FFP were compared with RNAlater-treated plasma and dried plasma spots (DPSs) after incubation at 37 degrees C, which was chosen as an upper limit of ambient shipping temperature, for up to 28 days. HCV-infected chimpanzee plasma was shipped at either room temperature after RNAlater treatment or as frozen plasma in liquid nitrogen from Liberia to New York City. They were then compared for HCV RNA levels. The nucleic acid stabilities were determined by quantitative PCR by using a molecular beacon assay on a sequence detection system (ABI 7700, PE-Biosystems) and by visualizing the PCR components on an acrylamide gel.

RESULTS

Quantitative PCR data showed that a 60:40 or greater ratio of RNAlater:plasma volume successfully stabilized HCV RNA and HIV RNA in plasma for up to 28 days at 37 degrees C. HBV DNA in plasma was stable for up to 14 days at 37 degrees C without any stabilizing solution. DPSs on filter paper stabilized viral nucleic acids, but the recoveries were 3 to 10 times less than those with frozen plasma. The integrity of the 5' UTR region of HCV RNA in RNA later-treated chimpanzee plasma was intact when its PCR component was viewed on an acrylamide gel.

CONCLUSION

The DPS method stabilized nucleic acids, at least with the extraction method used, was less sensitive than use of RNAlater, and required tedious manual handling. RNAlater provides a convenient way of stabilizing viral nucleic acid in plasma at ambient temperature during sample transportation.

Comparison of two different preparations of HIV immune globulin for efficiency of neutralization of HIV type 1 primary isolates

The objective of this study was to compare the virus-neutralizing ability of two different preparations of HIV immune globulin (HIVIG) isolated from human plasma units that were selected according to two different criteria. The first preparation, designated NYBC-HIVIG, was isolated from plasmas with high neutralizing antibody titers against HIV-1. The second preparation, designated NABI-HIVIG, was isolated from plasma with high titers of antibody to the HIV-1 p24 antigen. A panel of primary HIV-1 isolates was phenotypically characterized by their ability to induce syncytia in CEM-SS cells. Neutralization of this panel of primary isolates by the two HIVIG preparations was assessed in HeLa-MAGI-CCR5 cells, utilizing a luminescence-based assay. In addition, the reactivities of these two preparations with a panel of HIV-1 gp120 proteins, V3 loop peptides, and HIV-1 p24 antigen were determined. Both HIVIG preparations were shown to neutralize all virus isolates tested. However, doses of NABI-HIVIG required for 50% virus neutralization were 2.2- to 4.4- fold (mean, 3.2-fold) higher than the required doses of NYBC-HIVIG. Comparative antigen-binding assays showed that, although NABI-HIVIG possessed higher titers of antibody to HIV-1 p24, NYBC-HIVIG generally contained higher titers of antibody to HIV-1 gp120 and V3 peptides. These experiments show that the criteria used for selection of source plasmas for isolation of HIVIG can influence the effective concentration of virus-neutralizing antibody present in the final immunoglobulin preparation, and may determine the doses required for clinical efficacy.

DNA prime/canarypox boost-based immunotherapy of chronic hepatitis B virus infection in a chimpanzee

There are about 200 million chronic hepatitis B virus (HBV) carriers at high risk of development of cirrhosis and hepatocellular carcinoma. Termination of the carrier state may avert these risks. We have investigated immunotherapy for chronic HBV infection in a chimpanzee HBV carrier using recombinant DNA-based immunization followed by a recombinant canarypox booster. One week after the booster, HBV DNA declined greater than 400-fold and remained undetectable by the quantitative polymerase chain reaction (PCR) assay for 186 weeks. Plasma levels of hepatitis B surface antigen (HBsAg) declined for only a short time. The decline in HBV DNA correlated with a boost in gamma interferon production without a corresponding boost in cytotoxic T lymphocyte levels, and decline in the transcriptional template or covalently closed circular DNA level. Confirmation of these findings requires further studies in chimpanzees and/or in humans.

Antiretroviral effects of deoxyhypusyl hydroxylase inhibitors: a hypusine-dependent host cell mechanism for replication of human immunodeficiency virus type 1 (HIV-1)

The HIV-1 protein Rev, critical for translation of incompletely spliced retroviral mRNAs encoding capsid elements, requires a host cell protein termed "eukaryotic initiation factor 5A" (eIF-5A). This is the only protein containing hypusine, a lysine-derived hydroxylated residue that determines its proposed bioactivity, the translation of a subset of cellular mRNAs controlling G1-to-S transit of the cell cycle. We postulated that inhibiting the hypusine-forming deoxyhypusyl hydroxylase (DOHH) should, by depleting eukaryotic initiation factor 5A, compromise Rev function and thus reduce HIV-1 multiplication. We now report that the alpha-hydroxypyridones, specifically mimosine, a natural product, and deferiprone, an experimental drug, inhibited deoxyhypusyl hydroxylase in T-lymphocytic and promonocytic cell lines and, in a concentration-dependent manner, suppressed replication of HIV-1. However, the alpha-hydroxypyridones did not affect the formation of unspliced or multiply spliced HIV-1 transcripts. Rather, these agents caused Rev-dependent incompletely spliced HIV-1 mRNA such as gag, but not cellular "housekeeping" mRNAs, to disappear from polysomes. Consequently, alpha-hydroxypyridone-mediated depletion of eIF-5A decreased biosynthesis of structural HIV-1 protein encoded by gag, measured as p24, whereas the induced formation of cellular protein like tumor necrosis factor alpha remained unaffected. By interfering with the translation of incompletely spliced retroviral mRNAs, these compounds restrict HIV-1 to the early, nongenerative phase of its reproductive cycle. In the inducibly HIV-1 expressing T-cell line ACH-2, the deoxyhypusyl hydroxylase inhibitors triggered extensive apoptosis, particularly of cells that actively produce HIV-1. Selective suppression of retroviral protein biosynthesis and preferential apoptosis of retrovirally infected cells by alpha-hydroxypyridones point to a novel mode of antiretroviral action.

Passive immunization with a human immunodeficiency virus type 1-neutralizing monoclonal antibody in Hu-PBL-SCID mice: isolation of a neutralization escape variant

A monoclonal antibody (694/98-D) directed toward the V3 loop of human immunodeficiency virus type 1 (HIV-1) was evaluated for pre- and postexposure prophylaxis in SCID mice reconstituted with human peripheral blood lymphocytes (Hu-PBL-SCID). Fifty percent protection against the HIV-1LAI strain was obtained by preexposure administration of 1.32 mg/kg antibody. However, virus isolated from 1 mouse 3 weeks after passive immunization with 13.2 mg/kg antibody proved resistant to subsequent in vitro neutralization by 694/98-D. V3 loop sequence analysis of cloned virus revealed amino acid changes within the linear core epitope recognized by 694/98-D and in one flanking amino acid. Further evaluation of 694/98-D for postexposure prophylaxis in mice revealed that 694/ 98-D was effective when given 15 min after virus. However, efficacy declined to 50% if treatment was delayed to 1 h after virus inoculation. These studies point out some potential drawbacks of passive immunization with monoclonal antibodies.

Immunity in chimpanzees chronically infected with hepatitis C virus: role of minor quasispecies in reinfection

We have previously reported that chimpanzees chronically infected with hepatitis C virus (HCV) could be reinfected, even with the original infecting strain. In this study we tested the hypothesis that this might reflect the presence of minor quasispecies to which there was little or no immunity. To evaluate this hypothesis, we sequenced multiple clones taken at intervals after primary infection and rechallenge from four chronically infected chimpanzees. The inoculum used in these studies (HCV-H, genotype 1a) revealed 17 separate variants among 46 clones sequenced. Following challenge, each of the four challenged animals showed marked alterations of their quasispecies distribution. The new variants, which appeared 1 to 6 weeks after challenge, were either identical to or closely resembled variants present in the challenge inoculum. These results, paralleled by an increase in viremia in some of the challenged animals, suggest that quasispecies in the challenge inoculum were responsible for signs of reinfection and that there was little immunity. However, the newly emerged quasispecies completely took over infection in only one animal. In the remaining three chimpanzees the prechallenge quasispecies were able to persist. The natural evolution of infection within chimpanzees resulted in variants able to compete with the inoculum variants. Whether through reexposure or the natural progression of infection, newly emerged quasispecies are likely to play a role in the pathogenesis of chronic HCV infection.

Immune response to epitopes of hepatitis C virus (HCV) structural proteins in HCV-infected humans and chimpanzees

Hepatitis C virus (HCV)-infected humans and chimpanzees were studied for reactivity with linear epitopes in HCV H strain structural proteins. In 10 HCV-infected patients, epitopes were mostly mapped to the capsid and E1 proteins but not to E2. However, serum from 1 HCV-infected blood donor with a high anti-capsid titer reacted with multiple epitopes including E2. By contrast, antibody to capsid epitopes was seen in sera from HCV-rechallenged chimpanzees but not from chronically infected animals. No reactivity was observed to GOR epitope in chimpanzees, while 6 of 11 human subjects reacted with this host-coded antigen. Reactivity to rare epitopes in E2 was seen in chimpanzees with chronic and self-limited infections. Reactivity to one peptide of E1 (aa 316-329) was observed in 10 of 11 sera from HCV-infected humans and 11 of 15 chimpanzee sera. However, reactivity to this epitope was also seen in normal chimpanzees and in 6 (7.1%) of 84 uninfected human subjects.

PCR: how to kill unwanted DNA

Avoidance of contamination in the PCR laboratory requires the use of strict precautions. Among these, chemical decontamination of surfaces and equipment is desirable to prevent inadvertent contamination of samples by the gloved hand and by pipettors. We have investigated the use of sodium hypochloride (Clorox), in comparison to concentrated HCl, for PCR sterilization. Ten percent Clorox was found to eliminate all ethidium bromide-stainable DNA and to prevent PCR amplification of a 600-bp DNA segment within one minute of template treatment. RNA was similarly destroyed. By contrast, even 2.0 N HCl did not destroy DNA detectable by PCR within five minutes. Because of its high efficacy, low cost and relatively low corrosiveness, we recommend the use of ten percent Clorox as a decontaminant for elimination of DNA templates in the PCR laboratory.

Onchocerca volvulus: characterization of monoclonal antibodies reactive with surface components of third-stage larvae

Five murine monoclonal antibodies (Mab's) have been produced which are reactive with the surface of the third-stage larvae (L3) of Onchocerca volvulus. These were produced from a fusion performed after intrasplenic injection of 10 live O. volvulus L3. Hybridomas were first screened by Elisa using a PBS extract of O. volvulus female adult worms. Elisa negative wells were screened by IFA on whole formalin-fixed L3. Five Mab's were isolated which were reactive with the surface of L3, all were found to be of the IgM isotype. All five Mab's were cross-reactive with the surface of O. lienalis L3, but not with the L3 of Brugia malayi, B. pahangi, Dirofilaria immitis, or Acanthocheilonema viteae. One of the Mab's, OV3-9, reacted with an antigen common to many species of helminths. The other four were genus specific reacting only with O. volvulus and O. lienalis. All 5 Mab's reacted with L2 of O. volvulus, but not with the L4 by IFA on whole fixed larvae. Only Mab's OV3-8 and OV3-9 reacted with cryosections of adult O. volvulus by IFA indicating that the other 3 Mab's are specific for the surface of L2/L3 of the genus Onchocerca. None of the Mab's reacted with detergent dissociated L3 proteins in Western Blot analysis. The ability of L3 to bind the Mab's was abolished by incubating larvae in either proteinase K or trypsin but was unaffected by incubation of larvae in detergents, or by treatment with periodate, indicating the proteinaceous nature of the Mab specific epitopes. Anti-phosphorylcholine Mab (Gib-13) did not react with the surface of L3.(ABSTRACT TRUNCATED AT 250 WORDS)

hsp70 mRNA accumulates in LLC-PK1 pig kidney cells treated with calcitonin but not with 8-bromo-cyclic AMP

In LLC-PK1 pig kidney cells, treatment with a cAMP-elevating peptide hormone, calcitonin, induces the accumulation of urokinase-type plasminogen activator (uPA) mRNA. When we used the method of differential hybridization to isolate uPA cDNA clones, we also obtained several calcitonin-inducible clones that were unrelated to uPA. Sequence analysis revealed 60% sequence homology between one of these clones and that of a Drosophila hsp70 gene. The uPA and the hsp70 cDNA clones were used as probes to compare the effects of various treatments on the accumulation of uPA mRNA and hsp70 mRNA in LLC-PK1 cells. Calcitonin or 8-bromo-cAMP treatment induced uPA mRNA accumulation, which was negligible in untreated cells. Heat treatment (42 degrees C) was ineffective. Calcitonin or heat treatment increased hsp70 mRNA accumulation, which was already high in untreated cells, but 8-bromo-cAMP was ineffective. Nuclear transcription of the hsp70 gene was increased by calcitonin but not by 8-bromo-cAMP treatment. These results suggest that calcitonin induces hsp70 mRNA accumulation in LLC-PK1 cells by a pathway apart from the activation of adenylate cyclase and through, at least partly, the activation of the gene transcription. Furthermore, induction of uPA mRNA accumulation by calcitonin or 8-bromo-cAMP treatment did not require protein synthesis. In contrast, induction of hsp70 mRNA accumulation by calcitonin or heat treatment did require protein synthesis. Other reports showed that protein synthesis is not required for heat induction of hsp70 mRNA in different cells, suggesting that the mechanism of induction of hsp70 mRNA accumulation in LLC-PK1 cells is not the same as in other cells.

Lymphokine and nonlymphokine mRNA levels in stimulated human T cells. Kinetics, mitogen requirements, and effects of cyclosporin A

Northern and dot blotting with a panel of DNA probes were used to monitor the levels of specific mRNAs in mitogen-stimulated human T cells. The induction of IL-2 and IFN mRNAs required the synergistic action of PMA and either PHA or OKT3 mAb. In contrast, several nonlymphokine genes, the protooncogenes c-fos and c-myc, and the IL-2-R gene, were induced by either PHA or PMA alone. PHA increased the background levels of a 70 kD heat shock protein mRNA, but did not affect the observed background of c-myb mRNA. For all mRNAs that were induced, isolated CD4 and CD8 T cell subsets behaved similarly. Exogenous IL-2 had little (IFN) or no (IL-2) effect on lymphokine mRNAs, but significantly increased c-myc, IL-2-R and heat shock protein mRNAs. Therefore, the stimuli for lymphokine mRNAs differed from those required for several inducible nonlymphokine genes. IL-2 and IFN mRNAs exhibited some important similarities with c-myc, however. The levels of IL-2, IFN, and c-myc mRNA followed similar kinetics, peaking at 3 h in restimulated blasts and at 12 h in unstimulated T cells. The subsequent downregulation of lymphokine and c-myc mRNAs was retarded by cycloheximide. The induction of IL-2, IFN, and c-myc mRNAs was blocked by the immunosuppressive drug CsA, but not by the inactive analog CsH, and this block occurred at the level of nuclear transcription. Since the exogenous stimuli for lymphokine and c-myc gene expression differ, we suggest that intracellular controls must be shared to account for the similarities in their kinetics of expression and CsA sensitivity.

Antibodies to interleukin 2. Effects on immune responses in vitro and in vivo

Antibodies to highly purified mouse interleukin 2 (IL-2) were raised in rabbits; a 1:500 dilution of antiserum completely blocked the in vitro mitogenic effect of 10(-9) M IL-2. The antisera functioned effectively to immunoprecipitate biosynthetically labeled IL-2 and the purified immunoglobulins were useful in the construction of affinity columns for the adsorption and one-step immunopurification of IL-2. The antibodies were apparently specific for IL-2 among the lymphokines, they did not block the biological effects of IL-1, IL-3, gamma-IFN, B cell stimulating factor(s), and cytotoxic T cell differentiation factor(s). When anti-IL-2 was added to the in vitro reactions, it blocked mixed leukocyte reactions (MLR) and associated lymphocyte proliferation, the in vitro generation of cytotoxic T cells, and antibody formation as assessed by erythrocyte-specific plaque-forming cells (PFC). When injected into mice, anti-IL-2 antibodies also reduced the formation of cytotoxic lymphocytes in response to allogeneic cells, suggesting that endogenous IL-2 participates in such reactions in vivo. Taken together, the results indicate that these IL-2 antibodies will be useful adjuncts in the analysis of immune response both in vivo and in vitro.

Cytotoxic T cells both produce and respond to interleukin 2

Interleukin 2 (IL-2) is a T cell-derived lymphokine that serves as a cofactor for the in vitro response of T lymphocytes to antigen and plays an important role in regulating the growth and/or differentiation of these cells (1, 2). It has been postulated (2, 3) that IL-2 is produced by a discrete regulatory T cell subset, with its effects being exerted on a second, functionally distinct subpopulation of T cells. Cytotoxic T cells have been included in the IL-2-responsive subset (3). Several models of immune regulation have further assumed that the T lymphocyte pool is divided into a complex array of genetically preprogrammed T cell subtypes, each performing a specific regulatory or effector function (4, 5). However, recent results from several laboratories (6-8) have failed to support such a strict functional subdivision of the T cell pool. The availability of highly purified mouse IL-2 (1) prompted us to reevaluate the distinction, if any, between IL-2-producing and IL-2- responsive T cells. For this purpose, we resorted to a cell-cloning procedure using activated T lymphocytes that were maintained only for short periods in culture. T cell clones were tested for cytotoxic activity, responsiveness to IL-2, and for the capacity to produce IL-2 after appropriate stimulation. We found no evidence for the existence of a major functional subdivision involving these parameters among alloantigen-activated T cells: the majority of clones analyzed could perform all three functions.

Production of lymphocyte activating factor in vivo

Mice injected with Propionibacterium acnes, when challenged with lipopolysaccharide release a range of soluble mediators into their serum. Included among these is lymphocyte activating factor (LAF, interleukin-1). The release of LAF in vivo was detected only when serum samples were assayed at high dilution because inhibitors of its activity in vitro were also present. The kinetics of release of LAF in vivo after injection of P. acnes was dependent on the mouse strain used. LAF was also detected in serum collected from nude mice, implying that the LAF activity measured in vitro was not due to contamination with T cell products, such as interleukin 2.

Cultured thyroid allografts induce a state of partial tolerance in adult recipient mice

Thyroid allografts (BALB/c) prepared for transplantation by cyclophosphamide pretreatment of the donor, followed by organ culture of donor tissues for 3 weeks in a gas phase of 95% O2-5% CO2 function in normal CBA recipient mice for greater than or equal to 350 days. Up to 100 days post-transplantation, the tissue can be rejected by challenge of the recipient with 10(5) BALB/c peritoneal cells. After prolonged residence in the recipient (greater than 100, less than or equal to 350 days), only a proportion of allografts are rejected when the recipient is challenged with 10(5) followed by 10(6) peritoneal cells of donor origin. Recipients of long-term allografts are partially tolerant of BALB/c tissues. They are hyporesponsive to in vivo challenge with BALB/c spleen cells. However, lymph node cells from these animals respond essentially normally to stimulation with BALB/c spleen cells in vitro. Tolerant recipients will accept a second uncultured BALB/c allograft after a transitory rejection crisis. This crisis is not observed in the primary allograft.

Lethal effect of the intravenous injection of H-2 alloantigen activated T cells

T cells of C57BL/6J (B6) mice activated in vitro against the K and D determinants of the H-2d haplotype, and expanded in tissue culture in the presence of interleukin 2, were capable of rapidly killing lethally irradiated BALB/c recipients when injected intravenously. Mice given 10(6), 10(7) and 10(8) such T cells survived 10.5, 8.5 and 0.5 days respectively. Mice given irradiation only survived 10.5 days. Mice given 10(8) B6 T cells activated against all determinants of a third party haplotype (H-2k) survived 8.5 days. Respiratory distress developed within 3 hr of injection in mice given 10(8) T cells activated against the H-2 alloantigens of the recipient haplotype, and at autopsy their lungs showed pulmonary congestion, focal obliteration of the alveolar space and thickening of alveolar interstitial tissue with fibrin, red cell and a mononuclear cell infiltrate. These findings may have relevance to the use of cellular immunotherapy.

Interleukin 2 production by alloantigen (H-2) activated T cells

H-2 alloantigen-activated T cells release Interleukin 2 in response to a secondary stimulus by either Concanavalin A or alloantigen. No detectable lymphokine is released in the absence of secondary stimulation and, in the case of alloantigen restimulation, lymphokine release is antigen-specific. Once formed, however, the lymphokine shows no antigen specificity in its action. Like the precursor of the cytotoxic T cell, the precursor of the Interleukin 2-producing T cell requires two signals for its activation; alloantigen and a source of costimulator activity. Once activated, T cells will release lymphokine in response to alloantigen alone.

Inhibition of T-cell activity by cyclosporin A

Cyclosporin A (CyA) inhibits early events in the T-cell response. It strongly suppresses the activation of naive T cells by IL1 or IL2 and alloantigen. CyA exerts a selective effect on activated T cells. It inhibits the ability of these cells to release IL2 in response to antigen or mitogen restimulation, at concentration that have no effect on the ability of these same cell populations to respond to IL2 by proliferation. The specific effects of CyA are not limited to T cells, however, and this drug will inhibit IL1 production by lipopolysaccharide W-stimulated PU5-IR cells.

Interleukin 2 production by both Ly2+ and Ly2- T-cell subsets

Homogeneous T-cell populations produced by activating lymphocytes to I-, K-, or K+ D- region-encoded determinants of the mouse H-2 complex release interleukin 2 when restimulated by concanavalin A. Contrary to earlier reports on the cellular origin of the lymphokine, we find that interleukin 2 production can be either Ly2+ or Ly2- T-cell-dependent.

Cellular requirements for production and release of the lymphocyte costimulator

The lymphocyte costimulator (CoS) is a lymphokine required for the activation of T cell responses to H-2 alloantigens or mitogen, CoS activity is found in the supernatant medium of Concanavalin A (Con A) stimulated spleen cells, In this paper we investigate the cellular requirements for CoS production by Con A-activated mouse spleen cells. Maximal lymphokine production in response to Con A depends on a co-operative interaction between T cells and a nylon wool-adherent cell present in the spleen of nude mice. T cells appear to be the major producers of CoS activity, doing so only in response to an initial inductive stimulus supplied by nude spleen cells. The inductive stimulus is found as a soluble factor in the supernatant of Con A-activated spleen cells, and can also be provided by stimulatory (S+), but not by non-stimulatory (S-), tumour cells H-2 identical with the responding T cells. The activation of lymphokine-producing T cells is thus a two-signal process, requiring both mitogen and an additional inductive signal. Once activated, homogeneous populations of T cells will release lymphokine in response to mitogen alone.

Successful allotransplantation of mouse pancreatic islets to nonimmunosuppressed recipients

Pancreatic islets from BALB/c (H-2d) mice are rejected within 14 days of transplantation to the kidney capsule of allogeneic, CBA/H (H-2k) recipients. Cyclophosphamide pretreatment of the islet donor reduced the intensity of the allograft response, and these islets undergo a more chronic rejection process. Islets from cyclophosphamide-pretreated donors can be cultured in a gas phase of 95% O2 and 5% CO2, provided the islets are aggregated into clusters of about 50 islets. After a culture period of 7--12 days, the islet tissue was transplanted to normal allogeneic recipients, where the tissue elicited little or no allograft response over a 3-mo observation period.