Abstract 527: A streamlined workflow for liquid biopsy extraction and highplex digital PCR analysis using the Maxwell® RSC system and 6-color Crystal Digital PCR™

Circulating cell free DNA (cfDNA) extracted from liquid biopsy samples have become established sample types for characterizing oncology targets. Currently, there are several extraction protocols and genomic platforms for researchers to select when interrogating genetic information.

The focus of this work was to identify a flexible method for sample extraction that seamlessly integrates into a straightforward and sensitive genetic analysis workflow from plasma samples. Here, we present a workflow combining the Maxwell RSC system for automated cfDNA extraction and Crystal Digital PCR on the naica system for ultrasensitive high-plex detection from liquid biopsy samples of EGFR mutations in non-small cell lung cancer (NSCLC) and PIK3CA mutations and HER2 amplification in breast cancer.

By bridging sample extraction with the Maxwell RSC system and high-plex digital PCR with the 6-color naica® system, we detected with high sensitivity and precision 32 common and rare somatic EGFR mutations in exons 18, 19, 20, and 21, representing more than 90% of EGFR mutations described in NSCLC. Furthermore, following the same extraction and sample testing workflow, we simultaneously detected a set of PIK3CA mutations and HER2 amplification from cfDNA samples. This proof-of-concept workflow creates the foundation for further development of streamlined sample-to-answer protocols that will better assist cancer researchers across the biomarker testing landscape.

Citation Format: Cécile Jovelet, Myrtille Remy, Mylene Menanteau, Doug White, Douglas Horejsh, Allison Mallory. A streamlined workflow for liquid biopsy extraction and highplex digital PCR analysis using the Maxwell® RSC system and 6-color Crystal Digital PCR™ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 527.

Abstract 4426: Automated miRNA purification from plasma, serum or exosomes

Introduction: MicroRNAs (miRNAs) are endogenous small noncoding RNAs 18-24 nucleotides in size that play important roles involving gene regulation associated with cancer, disease control and gene silencing. Because of the impact on disease progression, miRNA research is rapidly shifting towards biomarker discovery. Many of the commercially available miRNA purification methods involve organic extraction during preprocessing. Here, we describe a novel chemistry that enables RNA purification including smaller RNA such as miRNA. This chemistry offers significant advantages with a simple automated workflow, no organic extraction and minimal preprocessing.

Method: In this study we show successful purification of small RNA, including miRNA, from 100uL to 500uL liquid samples utilizing a novel chemistry on the Maxwell® RSC instrument, which can process between 1 and 16 samples. Proteinase K and Lysis Buffer C are added to the liquid samples and incubated before being transferred to the Maxwell cartridge for miRNA isolation. Sample types tested include plasma, serum and isolated exosomes. The miRNA were evaluated using RT-qPCR including miR-16, miR-21, and let-7a.

Results: The eluates had high levels of small RNA including miRNA at levels comparable to manual competitor methods that require organic extraction. Quantitative PCR showed that the eluates had little or no detectable DNA contamination. Integration of the chemistry onto this automated platform reduced hands-on time while maintaining high quality needed for use in downstream RT-qPCR amplification assays.

Summary: This novel chemistry and method enables purification of small RNA from a range of samples types and volumes. The purified RNA has little or no detectable DNA contamination. Phenol extraction is not required, improving safety and simplifying waste disposal. Also, the automation of this workflow decreases manual hands-on time, saving scientist time and reducing the risk of RNase contamination.

Citation Format: Michelle Mandrekar, Jami English, Douglas Horejsh, Chris Moreland, Herly Karlen, Marjeta Urh. Automated miRNA purification from plasma, serum or exosomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4426.

Abstract 492: Automated circulating cell-free DNA purification from large volume draws

Circulating, cell-free DNA (ccfDNA) has emerged as an important tool in molecular oncology research. Because it is highly fragmented, present in small quantities, and highly susceptible to degradation, purification of ccfDNA poses unique challenges to researchers. While plasma is the main focus of many researchers for ccfDNA, recent work has shown that it is present in other biological fluids.

Promega has developed a unique chemistry to selectively purify ccfDNA from plasma. The Maxwell RSC ccfDNA Plasma system is a completely automated system that allows purification of ccfDNA from 1ml of plasma. To add flexibility, we adapted the chemistry to automated platforms in 24-well configurations. These platforms include the Hamilton Microlab STAR series and the KingFisher Flex Processor. Because the biomarkers in ccfDNA can be of very low frequency, many researchers prefer to process volumes of samples >1ml which can exceed the capacity of many purification systems. Using a sequential bind strategy, we demonstrate that ccf DNA can be purified from at least 8ml sample draw using a fully automated method. Liquid draws tested include plasma and urine. DNA quantity was assessed by qPCR using an autosomal target, and quality was assessed using an internal PCR control.

This study shows the flexibility and robustness of the Maxwell RSC ccfDNA chemistry. We successfully adapted it for purification from relatively large volume liquids in a fully automated manner making this a convenient option for early biomarker research.

Citation Format: Robert Ray, Mark Bratz, Doug Wieczorek, Douglas White, Douglas Horejsh, Eric Vincent, Trista Schagat. Automated circulating cell-free DNA purification from large volume draws. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 492.

Abstract 1957: MicroRNA analysis paired with a novel live cell viability assay: a complete epigenetic workflow in human cancer cell lines

The requirements for nucleic acid purification for use in RNA profiling have expanded with the growing interest in the role of microRNAs (miRNAs) and other small non-coding RNAs in cancer cell growth and metastasis. This evolution of expression analysis has highlighted the need for more sophisticated tools for total RNA isolation from cancer cells and tissues, beyond traditional translated messenger RNAs (mRNA). To address this need, we describe tools to isolate total RNA, for mRNA and miRNA analyses, in the context of an epigenetic workflow with cancer cell lines.

In these experiments, histone deacetylase (HDAC) inhibitor treatment of different cancer cell lines was performed and expression of miRNA and mRNAs measured in parallel with assays for cell viability, cytotoxicity, and HDAC activity. This workflow multiplexes RNA and miRNA expression profiling with assays for viability and cytotoxicity to efficiently capture a more complete understanding of expression results.

With this improved cell viability workflow, one experiment from the same well can yield information about cell health, cytotoxicity, HDAC activity, and mRNA plus miRNA expression profiling. Our workflow incorporates monitoring of cell health in real-time during experimental treatments, simple and effective total RNA purification, and robust quantitative PCR reagents for a comprehensive experimental design.

Citation Format: Samantha Lewis, Brad Hook, Don Smith, Douglas Horejsh, Trista Schagat. MicroRNA analysis paired with a novel live cell viability assay: a complete epigenetic workflow in human cancer cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1957.

Abstract 4846: Automated RNA and DNA purification from FFPE samples

Formalin-fixed, paraffin-embedded (FFPE) samples are commonly used for archiving pathology samples for use by many researchers including clinical research labs. These samples provide a valuable tool for retrospective studies of diseases such as cancer. Traditional methods for the purification of DNA or RNA from FFPE tissue samples are often labor intensive, include the use of hazardous organic reagents, and involve difficult pre-processing steps. Here, we describe development of automated methods for the purification of RNA or DNA from FFPE tissue sections using the Maxwell® RSC Instrument, which can process between 1 and 16 samples. DNA was purified from FFPE mouse brain, liver, lung, skin and spleen as well as FFPE human colon. RNA was purified from FFPE mouse brain, liver, lung, skin and spleen as well as FFPE human breast tissue. Eluates were tested for inhibition in qPCR or RT-qPCR. A comparison with another automated method was performed with FFPE mouse spleen and skin and a human tissue. The Maxwell RSC methods produced high quality amplifiable DNA or RNA from a variety of sample types with little or no inhibition. In addition, these methods simplified pre-processing, minimized hands-on time, and did not use hazardous organics.

Citation Format: Michelle Mandrekar, Douglas Horejsh, Samantha Lewis, Chris Moreland, Marjeta Urh. Automated RNA and DNA purification from FFPE samples. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4846. doi:10.1158/1538-7445.AM2015-4846

Abstract 3383: Correlation of mutations detected in liquid and tissue biopsies

Circulating cell-free DNA (ccfDNA) in plasma can be used to detect biomarkers that show great promise for diagnosis and monitoring of cancer, giving rise to the possibility of liquid biopsies that obviate the need for invasive tissue collection. The low concentration and highly fragmented nature of ccfDNA, coupled with the low frequency of potential oncogenic biomarkers, presents challenges and will require a purification method that is efficient and highly reproducible.

Here we describe a method for purifying nucleic acids based on novel surface and binding chemistries. The combination of these two approaches allows for increased binding of fragmented DNA. The method can be partially automated to ensure highly reproducible results. Up to 4mls of plasma can be processed and eluted in as little as 15ul, giving DNA concentrations of 1-10ul. This greatly facilitates use in Next Generation Sequencing.

Using the automated method, ccfDNA was purified from the plasma of 7 patients who had previously undergone surgical resection for malignancy. DNA was also purified from the FFPE malignant tissue off of slides, following macrodissection, from the same patients. NGS was used to interrogate both sample types for potentially oncogenic variants. Several laboratory developed tests, all including COLD-PCR, were also employed to verify the presence or absence of variants. The two types of samples showed excellent correlation on mutations, suggesting that use of a less invasive liquid biopsy has the potential to enable actionable mutation detection without using more invasive solid tumor biopsy means.

Citation Format: Douglas H. White, Douglas Horejsh, Molly Accola, William Rehrauer, Marjeta Urh. Correlation of mutations detected in liquid and tissue biopsies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3383. doi:10.1158/1538-7445.AM2015-3383

Abstract 1872: A novel method for efficient and hands-free purification of circulating DNA from human plasma

Circulating or Cell-Free DNA in plasma can be used to detect biomarkers that show great promise for diagnosis and monitoring of cancer, and is already being used as a non-invasive method to detect trisomy in fetuses. There is currently great interest in the discovery of new cancer biomarkers and their potential clinical application. However, reproducible and efficient purification of these highly fragmented and low-concentration species represents a major challenge. Here we will present a novel method which is completely automated and allows parallel purification of circulating nucleic acid from plasma and serum using a medium-throughput robot. Sixteen samples can be processed simultaneously. The method was optimized to produce high-quality DNA that is suitable for use in quantitative PCR and next generation sequencing. In addition, the absence of any pre-processing steps improves reproducibility and lowers the risk of contamination.Initial characterization on plasma from pregnant women showed that fetal DNA could be detected as early as 4 weeks into gestation and could be tracked throughout pregnancy. Further characterization showed that the system was able to reliably detect less than 25 copies/ml plasma of fragmented DNA that was spiked into the sample. Subsequent work on plasma from patients with colorectal cancer showed that the system was able to detect DNA containing both wild-type and mutated EGFR, suggesting that this method can be a useful tool when screening plasma samples for biomarkers of interest.

Citation Format: Douglas White, Douglas Horejsh, Zhiyang Zeng, Tetsuo Uyeda, Poncho Meisenheimer, Marjeta Urh. A novel method for efficient and hands-free purification of circulating DNA from human plasma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1872. doi:10.1158/1538-7445.AM2014-1872

Efficacy of three surface disinfectants against spores of Clostridium difficile ribotype 027

BACKGROUND

The emergence of Clostridium difficile ribotype 027 raised the question of sporicidal surface disinfectants are also effective against spores of C. difficile ribotype 027.

MATERIALS AND METHODS

Three surface disinfectants based on magnesium monoperoxyphthalate hexahydrate (Dismozon pur), a combination of (ethylenedioxy)dimethanol, glutaral and benzyl-C12-18-alkyldimethylammonium chlorides (Kohrsolin extra) and a combination of glutaral, benzyl-C12-18-alkyldimethylammonium chlorides and didecyl-dimethylammonium chloride (Kohrsolin FF) were tested in a suspension test in various concentrations and contact times against spores of three C. difficile strains including ribotype 027.

RESULTS

All three surface disinfectant reduced the number of spores by ≥4 log(10) steps, e.g. Dismozon pur at 1.5% and 2 h exposure time, Kohrsolin extra at 2% and 4 h exposure time, and Kohrsolin FF at 2% and 6 h exposure time. Spores of ribotype 027 did not show a lower susceptibility to Dismozon pur compared to the other two C. difficile strains.

CONCLUSIONS

All three tested surface disinfectants should be effective for surface disinfection in outbreaks caused by C. difficile ribotype 027.

BeadCons: detection of nucleic acid sequences by flow cytometry

Molecular beacons are single-stranded nucleic acid structures with a terminal fluorophore and a distal, terminal quencher. These molecules are typically used in real-time PCR assays, but have also been conjugated with solid matrices. This unit describes protocols related to molecular beacon-conjugated beads (BeadCons), whose specific hybridization with complementary target sequences can be resolved by cytometry. Assay sensitivity is achieved through the concentration of fluorescence signal on discrete particles. By using molecular beacons with different fluorophores and microspheres of different sizes, it is possible to construct a fluid array system with each bead corresponding to a specific target nucleic acid. Methods are presented for the design, construction, and use of BeadCons for the specific, multiplexed detection of unlabeled nucleic acids in solution. The use of bead-based detection methods will likely lead to the design of new multiplex molecular diagnostic tools.

Ability of peripheral blood mononuclear cells to activate interferon response in vitro is predictive of virological response in HCV patients

The most reliable predictor of treatment efficacy in hepatitis C is HCV viremia decay at week 12 [early virological response (EVR)]. We investigated whether the ability of peripheral blood mononuclear cells (PBMC) to mount an interferon (IFN) response in vitro could be predictive of EVR. Fifteen patients treated with PEG IFNalpha + RBV, with pre-therapy frozen PBMC, were retrospectively selected. After a 3 hr PBMC exposure to IFNalpha in vitro, up-regulation of mRNA for IFN-stimulated genes (ISG) was measured by membrane super-array. ISG mRNA levels in unstimulated PBMC were low, but beta2M and CASP1 were significantly higher in EVR vs non-EVR. ISG mRNA up-regulation by IFN was more pronounced in EVR vs non-EVR. For 7 genes (IP-10, IFIT1, IFIT2, IFIT3, TRAIL, KIAA1628 and OAS2) cut-off levels were established, by ROC analysis, able to correctly classify all EVR and non-EVR. Early virological response to PEG IFNalpha +RBV is correlated with the pre-therapy ability of PBMC to activate an IFN response in vitro. If validated in a wider cohort of patients, the ability of this set of ISG to discriminate between EVR and non-EVR may be useful for pre-therapy evaluation, particularly in patients with unfavourable combinations of conventional response predictors.

[Rapid differential diagnosis of Orthopoxviruses and Herpesviruses based upon multiplex real-time PCR]

OBJECTIVE

Variola virus, belonging to Orthopoxviridae family, is one of the most dangerous human pathogens that could be used as biological weapon. We have developed a new rapid assay, based upon Real-time PCR and melting temperatures analysis of amplicons, for the contemporary detection of Orthopoxvirus, VZV and HSV1-2, that are the most important infectious agents to be considered for differential diagnosis.

METHODS

The target for detection of orthopoxvirus DNA has been a region of the crmB gene which is common to Variola virus and to other old world orthopoxviruses pathogenic for humans. The targets for VZV and HSV1-2 have been ORF 29 and DNA polymerase, respectively. Suitability of the amplified fragments to RFLP or sequencing analysis, to recognize the involved viral species, has been also tested.

RESULT

The selected primers have showed high sensitivity, specificity and compatibility with common amplification conditions. A mean melting temperature difference of 8.7 degree C was observed between the amplicons from the two virus types. Further identification of individual pathogens was made using RFLP analysis.

CONCLUSION

The PCR-based protocol set up in this study for presumptive differential diagnosis of variola and herpesviral infections is rapid and specific and it can be used also to detect other orthopoxviral infections, like monkeypox.

Anti-severe acute respiratory syndrome coronavirus immune responses: the role played by V gamma 9V delta 2 T cells

Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus (SARS-CoV) strain. Analyses of T cell repertoires in health care workers who survived SARS-CoV infection during the 2003 outbreak revealed that their effector memory Vγ9Vδ2 T cell populations were selectively expanded ∼3 months after the onset of disease. No such expansion of their αβ T cell pools was detected. The expansion of the Vγ9Vδ2 T cell population was associated with higher anti–SARS-CoV immunoglobulin G titers. In addition, in vitro experiments demonstrated that stimulated Vγ9Vδ2 T cells display an interferon-γ–dependent anti–SARS-CoV activity and are able to directly kill SARS-CoV–infected target cells. These findings are compatible with the possibility that Vγ9Vδ2 T cells play a protective role during SARS

T-Cell response profiling to biological threat agents including the SARS coronavirus

The emergence of pathogens such as SARS and the increased threat of bioterrorism has stimulated the development of novel diagnostic assays for differential diagnosis. Rather than focusing on the detection of an individual pathogen component, we have developed a T cell profiling system to monitor responses to the pathogens in an array format. Using a matrix of antigens specific for different pathogens, a specific T cell profile was generated for each individual by monitoring the intracellular production of interferon-gamma by flow cytometry. This assay allows for the testing of multiple proteins or peptides at a single time and provides a quantitative and phenotypic assessment of CD4(+) and CD8(+) responding cells. We present profiling examples for several positive individuals, including those vaccinated with the smallpox and anthrax vaccines. We also show antigen optimization for the SARS-hCoV, as studies revealed that these proteins contain peptides which cross-react with more common coronaviruses, a cause of the common cold. The T cell array is an early and sensitive multiplex measure of active infection, exposure to a pathogen, or effective, recent vaccination.

Rapid, differential diagnosis of orthopox- and herpesviruses based upon real-time PCR product melting temperature and restriction enzyme analysis of amplicons

Orthopoxviruses tend to have non-specific early symptoms that cannot be differentiated readily from other infectious exanthemas, such as varicella-zoster virus (VZV) or disseminated herpes simplex virus (HSV) infections. A rapid assay was developed for the differential diagnosis of orthopoxviruses and herpesviruses based upon the melting temperatures of real-time PCR amplicons. A mean melting temperature difference of 8.7 degrees C was observed between the products amplified from the two virus families. Further identification of individual pathogens was made using restriction enzyme analysis. The assay was able to identify correctly viruses from quality control panels of herpes and orthopoxviruses.

Long-lasting CD3+ T-cell deficiency after cord blood stem cell transplantation in a human herpesvirus 6-infected child

We report a long-lasting (8-month) reactivation of human herpesvirus 6 (HHV-6) infection in child who had undergone cord blood stem cell transplantation. The reactivation was characterized by high viral loads and by immediate-early mRNA positivity. HHV-6 infection was associated with a deep depletion of CD3, while the CD4/CD8 ratio remained substantially unchanged.

A molecular beacon, bead-based assay for the detection of nucleic acids by flow cytometry

Molecular beacons are dual-labelled probes that are typically used in real-time PCR assays, but have also been conjugated with solid matrices for use in microarrays or biosensors. We have developed a fluid array system using microsphere-conjugated molecular beacons and the flow cytometer for the specific, multiplexed detection of unlabelled nucleic acids in solution. For this array system, molecular beacons were conjugated with microspheres using a biotin-streptavidin linkage. A bridged conjugation method using streptavidin increased the signal-to-noise ratio, allowing for further discrimination of target quantitation. Using beads of different sizes and molecular beacons in two fluorophore colours, synthetic nucleic acid control sequences were specifically detected for three respiratory pathogens, including the SARS coronavirus in proof-of-concept experiments. Considering that routine flow cytometers are able to detect up to four fluorescent channels, this novel assay may allow for the specific multiplex detection of a nucleic acid panel in a single tube.

Flow cytometry and T-cell response monitoring after smallpox vaccination

Orthopoxvirus zoonosis or smallpox as result of bioterrorism or biological warfare represents a risk for epidemic spread. By monitoring T-cell responses by flow cytometry, we observed a recall response after recent vaccination against smallpox. When the high similarity between the orthopoxviruses is considered, this rapid assay that uses vaccinia antigens could identify recently exposures.

Human herpesvirus-6 modulates RANTES production in primary human endothelial cell cultures

Human herpesvirus 6 (HHV6) is a beta-herpesvirus capable of infecting several cell types from different origins. HHV6 is the etiological agent of exantem subitum and has been associated with several diseases, all characterized by an inflammatory response triggered by chemokines. We show that strain U1102 of HHV6 is able to infect persistently human endothelial cells obtained from umbilical veins, adult aorta and adult heart microvessels, without apparent cytopathic effect. Analysis by in situ PCR showed that HHV6 sequences were present in 20% of HUVEC, 10% of aortic, and 1% of heart microvascular endothelial cells. Regardless of endothelial cell origin, HHV6 infection induced de novo synthesis of the RANTES CC-chemokine. It was found, however, that microvascular endothelial cells, despite their lower susceptibility to HHV6 infection, showed the highest RANTES expression. Chemokine production occurred also in the absence of viral DNA synthesis. Furthermore, RANTES synthesis required an active viral genome, as UV-inactivated HHV6 infection of endothelial cells did not lead to chemokine production. We investigated the expression of HHV6 U51 gene, which encodes a chemokine receptor that is already known to sequester and down modulate RANTES in epithelial cells. HHV6-infected endothelial cells co-expressed RANTES and U51 mRNAs starting from 12 hr up to 48 hr post-infection. Then, RANTES transcripts disappeared whereas U51 messages continued to be expressed. In conclusion, this study highlights the major role of HHV6 in endothelial cell biology and the development of inflammatory processes.

CXCR4-dependent HIV-1 infection of differentiated epithelial cells

Epithelial cells constitute a physical barrier to sexual transmission of HIV, but are also a source of cytokines that could alter infection efficiency. We studied HIV infection of the human colonic epithelial cell line HCT116, which is a model for differentiation of intestinal mucosal epithelium. Differentiated HCT116 cells had increased expression of cell surface C-X-C chemokine receptor type-4 (CXCR4) that mediated HIV entry, despite the apparent absence of cell surface CD4. HIV infection in differentiated HCT116 cells increased the levels of IL-1alpha, and IFN-alpha mRNA even though only 1% of cells had integrated provirus. The inefficient, CXCR4-mediated infection of differentiated HCT116 cells supports the view that epithelial cells are a barrier and not a portal for HIV transmission. However, low level infection of epithelial cells could trigger the release of cytokines that indirectly increase the transmission rate.

Role of the promyelocytic leukemia protein PML in the interferon sensitivity of lymphocytic choriomeningitis virus

Lymphocytic choriomeningitis virus (LCMV) induces type I interferon (alpha and beta interferon [IFN-alpha and IFN-beta]) upon infection and yet is sensitive to the addition of type II interferon (gamma interferon [IFN-gamma]) to the culture media. This sensitivity is biologically important because it correlates inversely with the ability of certain LCMV strains to persist in mice (D. Moskophidis, M. Battegay, M. A. Bruendler, E. Laine, I. Gresser, and R. M. Zinkernagel, J. Virol. 68:1951-1955, 1994). The cellular oncoprotein PML is induced by both IFN-alpha/beta and IFN-gamma, and PML binds the LCMV Z protein and becomes redistributed within cells from nucleus to cytoplasm upon LCMV infection. In the present study, increased PML expression results in diminished LCMV replication, implicating PML in the IFN sensitivity of LCMV. Virus production in PML -/- murine embryonic fibroblasts (MEF) exceeds virus production in PML +/+ MEF, and this difference is exacerbated by IFN treatment that upregulates PML expression. IFN-gamma also diminishes LCMV production in PML -/- cells; therefore, viral IFN sensitivity is not entirely due to PML. Both viral mRNA production and viral protein production decrease as PML expression increases. Here we propose that PML reduces LCMV transcription through its interaction with the Z protein.

Whole body positron emission tomography imaging of activated lymphoid tissues during acute simian-human immunodeficiency virus 89.6PD infection in rhesus macaques

Mechanisms of acute retroviral pathogenesis have been examined during primary infection of rhesus macaques with simian-human immunodeficiency virus 89.6PD (SHIV(89.6PD)). During acute infection, between initial exposure and establishment of antigen-specific immune responses that stabilize the virus burden, rapid immune system changes influence the viral set-point and dictate subsequent steps in disease progression. In a previous study, we described specific patterns of lymphocyte activation during acute SHIV(89.6PD) infection. We now extend these studies to describe lymphoid tissue activation, using whole body positron emission tomography (PET) and the radioactive tracer 2-[(18)F]fluorodeoxyglucose (FDG). Within a few days after primary infection by intravenous, intrarectal, or intravaginal routes, PET-FDG imaging revealed a distinct pattern of lymphoid tissue activation centered on axillary, cervical, and mediastinum lymph nodes. Increased tissue FDG uptake preceded fulminant virus replication at these sites, suggesting that a diffusible factor of host or viral origin was responsible for lymphoid tissue changes. These data show that activation of lymphoid tissues in the upper body is an early response to virus infection and that diffusible mediators of activation might be important targets for vaccine or therapeutic intervention strategies.

Lassa and Mopeia virus replication in human monocytes/macrophages and in endothelial cells: different effects on IL-8 and TNF-alpha gene expression

Cells of the mononuclear and endothelial lineages are targets for viruses which cause hemorrhagic fevers (HF) such as the filoviruses Marburg and Ebola, and the arenaviruses Lassa and Junin. A recent model of Marburg HF pathogenesis proposes that virus directly causes endothelial cell damage and macrophage release of TNF-alpha which increases the permeability of endothelial monolayers [Feldmann et al. , 1996]. We show that Lassa virus replicates in human monocytes/macrophages and endothelial cells without damaging them. Human endothelial cells (HUVEC) are highly susceptible to infection by both Lassa and Mopeia (a non-pathogenic Lassa-related arenavirus). Whereas monocytes must differentiate into macrophages before supporting even low level production of these viruses, the virus yields in the culture medium of infected HUVEC cells reach more than 7 log10 PFU/ml without cellular damage. In contrast to filovirus, Lassa virus replication in monocytes/macrophages fails to stimulate TNF-alpha gene expression and even down-regulates LPS-stimulated TNF-alpha mRNA synthesis. The expression of IL-8, a prototypic proinflammatory CXC chemokine, was also suppressed in Lassa virus infected monocytes/macrophages and HUVEC on both the protein and mRNA levels. This contrasts with Mopeia virus infection of HUVEC in which neither IL-8 mRNA nor protein are reduced. The cumulative down-regulation of TNF-alpha and IL-8 expression could explain the absence of inflammatory and effective immune responses in severe cases of Lassa HF.

Lymphocyte activation during acute simian/human immunodeficiency virus SHIV(89.6PD) infection in macaques

Host-virus interactions control disease progression in human immunodeficiency virus-infected human beings and in nonhuman primates infected with simian or simian/human immunodeficiency viruses (SHIV). These interactions evolve rapidly during acute infection and are key to the mechanisms of viral persistence and AIDS. SHIV(89.6PD) infection in rhesus macaques can deplete CD4(+) T cells from the peripheral blood, spleen, and lymph nodes within 2 weeks after exposure and is a model for virulent, acute infection. Lymphocytes isolated from blood and tissues during the interval of acute SHIV(89.6PD) infection have lost the capacity to proliferate in response to phytohemagglutinin (PHA). T-cell unresponsiveness to mitogen occurred within 1 week after mucosal inoculation yet prior to massive CD4(+) T-cell depletion and extensive virus dissemination. The lack of mitogen response was due to apoptosis in vitro, and increased activation marker expression on circulating T cells in vivo coincided with the appearance of PHA-induced apoptosis in vitro. Inappropriately high immune stimulation associated with rapid loss of mature CD4(+) T cells suggested that activation-induced cell death is a mechanism for helper T-cell depletion in the brief period before widespread virus dissemination. Elevated levels of lymphocyte activation likely enhance SHIV(89.6PD) replication, thus increasing the loss of CD4(+) T cells and diminishing the levels of virus-specific immunity that remain after acute infection. The level of surviving immunity may dictate the capacity to control virus replication and disease progression. We describe this level of immune competence as the host set point to show its pivotal role in AIDS pathogenesis.

Mucosal transmission of virulent and avirulent lentiviruses in macaques

Sexual transmission of human immunodeficiency virus provides an efficient mode for virus spread and poses unique challenges to vaccine developers. Host and viral factors that affect transmission have been studied by epidemiological approaches in the human population, and some of these factors have been modeled with experimental infection of nonhuman primates. Basic principles have emerged regarding transmission and viral virulence. These ideas may be beneficial for designing a safe and effective vaccine.

Intrarectal transmission of simian immunodeficiency virus in rhesus macaques: selective amplification and host responses to transient or persistent viremia

Intrarectal simian immunodeficiency virus (SIV) infection in rhesus macaques is a model for sexual transmission of primate retroviruses. Phylogenetic studies on envelope gene sequences that were present in blood following intrarectal SIV inoculation provided evidence for selective amplification of a subset of viruses present in the inoculum and defined one amino acid sequence uniquely associated with intrarectal infection. Both persistent and transient viremia states were observed after intrarectal infection. Immune responses in persistently infected animals accounted for slower rates of disease progression despite the presence of highly pathogenic viruses that were documented by transfusion studies. Transient viremia elicited protective immunity against subsequent intrarectal virus challenge but did not protect against intravenous virus challenge. Transient viremia usually but not always led to self-limiting infection. In one animal, we documented a relapse to active viremia long after the initial transient viremia. SIV transmission across mucosal barriers affects pathogenesis in the short term by limiting the types of viruses established in the host and in the longer term by establishing host responses that slow disease progression despite the presence of highly pathogenic viruses in blood.