A sensitive and versatile bioluminescence bioassay for HIV type 1 based on adenoviral vectors

Simian virus 40 vectors for pulmonary gene therapy

Background

Sepsis remains the leading cause of death in critically ill patients. One of the primary organs affected by sepsis is the lung, presenting as the Acute Respiratory Distress Syndrome (ARDS). Organ damage in sepsis involves an alteration in gene expression, making gene transfer a potential therapeutic modality. This work examines the feasibility of applying simian virus 40 (SV40) vectors for pulmonary gene therapy.

Methods

Sepsis-induced ARDS was established by cecal ligation double puncture (2CLP). SV40 vectors carrying the luciferase reporter gene (SV/luc) were administered intratracheally immediately after sepsis induction. Sham operated (SO) as well as 2CLP rats given intratracheal PBS or adenovirus expressing luciferase served as controls. Luc transduction was evaluated by in vivo light detection, immunoassay and luciferase mRNA detection by RT-PCR in tissue harvested from septic rats. Vector abundance and distribution into alveolar cells was evaluated using immunostaining for the SV40 VP1 capsid protein as well as by double staining for VP1 and for the surfactant protein C (proSP-C). Immunostaining for T-lymphocytes was used to evaluate the cellular immune response induced by the vector.

Results

Luc expression measured by in vivo light detection correlated with immunoassay from lung tissue harvested from the same rats. Moreover, our results showed vector presence in type II alveolar cells. The vector did not induce significant cellular immune response.

Conclusion

In the present study we have demonstrated efficient uptake and expression of an SV40 vector in the lungs of animals with sepsis-induced ARDS. These vectors appear to be capable of in vivo transduction of alveolar type II cells and may thus become a future therapeutic tool.

Synchronized infection of cell cultures by magnetically controlled virus

To override the diffusion-limited adsorption step of viral infection, we magnetically synchronized cell attachment. Human immunodeficiency virus type 1-based lentivirus preparations were rendered magnetically reactive by association with magnetite nanoparticles, 50 nm in diameter. Application of a magnetic field resulted in immediate redistribution of the viral inoculum to the cell-associated state and completion of the productive adsorption process within 1 min. Independent of adsorption time, viral concentration, and diffusion rate, infection subsequently progressed by the receptor-mediated entry mechanism. Synchronization of this rate-limiting step of infection may now be applied to analyze isolated events in the viral replication sequence.

Human immunodeficiency virus type 1 infection inhibits granulocyte-macrophage colony-stimulating factor-induced activation of STAT5A in human monocyte-derived macrophages

Human immunodeficiency virus type 1 (HIV-1) infects cells of the monocyte/macrophage lineage. While infection of macrophages by HIV-1 is generally not cytopathic, it does impair macrophage function. In this study, we examined the effect of HIV-1 infection on intracellular signaling in human monocyte-derived macrophages (MDM) stimulated with the growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF is an important growth factor for cells of both the macrophage and granulocyte lineages and enhances effector functions of these cells via the heterodimeric GM-CSF receptor (GM-CSFR). A major pathway which mediates the effects of GM-CSF on macrophages involves activation of the latent transcription factor STAT5A via a Janus kinase 2 (JAK2)-dependent pathway. We demonstrate that GM-CSF-induced activation of STAT5A is inhibited in MDM after infection in vitro with the laboratory-adapted R5 strain of HIV-1, HIV-1(Ba-L), but not after infection with adenovirus. HIV-1 infection of MDM did not decrease the STAT5A or JAK2 mRNA level or STAT5A protein level or result in increased constitutive activation of STAT5A. Surface expression of either the alpha-chain or common beta(c)-chain of GM-CSFR was also unaffected. We conclude that HIV-1 inhibits GM-CSF activation of STAT5A without affecting expression of the known components of the signaling pathway. These data provide further evidence of disruption of cellular signaling pathways after HIV-1 infection, which may contribute to immune dysfunction and HIV-1 pathogenesis.

Selectively reduced tat mRNA heralds the decline in productive human immunodeficiency virus type 1 infection in monocyte-derived macrophages

The transcription and splicing of human immunodeficiency virus type 1 (HIV-1) mRNA in primary blood monocyte-derived macrophages (MDM) and CD4(+) peripheral blood lymphocytes (PBL) were compared to determine whether any differences might account for the slower noncytopathic infection of cells of the macrophage lineage. The expression of regulatory mRNAs during acute infection of MDM was delayed by about 12 h compared to that of PBL. In each cell type, an increase in spliced viral mRNAs slightly preceded virus production from the culture. Following the peak of productive infection, there was a proportional decrease in the expression of all regulatory mRNAs detected in PBL. In MDM, a dramatic additional decrease specifically in the tat mRNA species heralded a reduction in virus production. This decline in tat mRNA was reflected by a concomitant decrease in Tat activity in the cells and occurred with the same kinetics irrespective of the age of the cells when infected. Addition of exogenous Tat protein elicited a burst of virus production from persistently infected MDM, suggesting that the decrease in virus production from the cultures is a consequence of the reduction in tat mRNA levels. Our results show that modulation of HIV-1 mRNAs in macrophages during long-term infection, which is dependent on the period of infection rather than cell differentiation or maturation, results in a selective reduction of Tat protein levels at the commencement of a persistent, less productive phase of infection. Determination of the mechanism of this mRNA modulation may lead to novel targets for control of replication in these important viral reservoirs.

An adenovirus-based fluorescent reporter vector to identify and isolate HIV-infected cells

A procedure is described that allows the simple identification and sorting of live human cells that transcribe actively the HIV virus, based on the detection of GFP fluorescence in cells. Using adenoviral vectors for gene transfer, an expression cassette including the HIV-1 LTR driving the reporter gene GFP was introduced into cells that expressed stably either the Tat transcriptional activator, or an inactive mutant of Tat. Both northern and fluorescence-activated cell sorting (FACS) analysis indicate that cells containing the functional Tat protein presented levels of GFP mRNA and GFP fluorescence several orders of magnitude higher than control cells. Correspondingly, cells infected with HIV-1 showed similar enhanced reporter gene activation. HIV-1-infected cells of the lymphocytic line Jurkat were easily identified by fluorescence-activated cell sorting (FACS) as they displayed a much higher green fluorescence after transduction with the reporter adenoviral vector. This procedure could also be applied on primary human cells as blood monocyte-derived macrophages exposed to the adenoviral LTR-GFP reporter presented a much higher fluorescence when infected with HIV-1 compared with HIV-uninfected cells. The vector described has the advantages of labelling cells independently of their proliferation status and that analysis can be carried on intact cells which can be isolated subsequently by fluorescence-activated cell sorting (FACS) for further culture. This work suggests that adenoviral vectors carrying a virus-specific transcriptional control element controlling the expressions of a fluorescent protein will be useful in the identification and isolation of cells transcribing actively the viral template, and to be of use for drug screening and susceptibility assays.

Imaging transgene expression in live animals

Monitoring the expression of therapeutic genes in targeted tissues in disease models is important to assessing the effectiveness of systems of gene therapy delivery. We applied a new light-detection cooled charged-coupled device (CCCD) camera for continuous in vivo assessment of commonly used gene therapy delivery systems (such as ex vivo manipulated cells, viral vectors, and naked DNA), without the need to kill animals. We examined a variety of criteria related to real-time monitoring of luciferase (luc) gene expression in tissues including bone, muscle, salivary glands, dermis, liver, peritoneum, testis, teeth, prostate, and bladder in living mice and rats. These criteria included determination of the efficiency of infection/transfection of various viral and nonviral delivery systems, promoter specificity, and visualization of luciferase activity, and of the ability of luciferin to reach various organs. The exposure time for detection of luc activity by the CCCD camera is relatively short (approximately 2 minutes) compared with the intensified CCD camera photon-counting method (approximately 15 minutes). Here we transduce a variety of vectors (such as viruses, transfected cells, and naked DNA) by various delivery methods, including electroporation, systemic injection of viruses, and tail-vein, high-velocity-high-volume administration of DNA plasmids. The location, intensity, and duration of luc expression in different organs were determined. The distribution of luciferin is most probably not a barrier for the detection of in vivo luciferase activity. We showed that the CCCD photon detection system is a simple, reproducible, and applicable method that enables the continuous monitoring of a gene delivery system in living animals.