Macrophages are considered of central importance in cell-to-cell transmission of human immunodeficiency virus (HIV) infection in vivo. In this report, we describe a novel cell-to-cell transmission model using HIV-infected monocyte-derived macrophages (MDMs) as donor cells and peripheral blood lymphocytes (PBLs) as recipients. Virus was transmitted during a 2-h coincubation period from intracellular or tightly cell-associated viral stores in adherent infected MDMs to nonadherent CD3(+) PBLs. Transmission required cell contact, but syncytia formation was not observed. HIV cell-to-cell transmission occurred in both allogeneic and autologous systems, and replication was higher in phytohemagglutinin (PHA)-stimulated than unstimulated recipient PBLs. In contrast, transmission of infection by cell-free virus was barely detectable without PHA stimulation of recipients, suggesting the cell-cell interaction may have provided stimuli to recipient cells in the cell-to-cell system. Viral DNA levels increased 5-24 h postmixing, and this increase was inhibited by pretreatment of cells with the reverse transcription inhibitor azidothymidine, indicating de novo reverse transcription was involved. Cell-to-cell transmission was more efficient than infection with cell-free virus released from donor MDMs, or 0.1 TCID(50)/cell cell-free viral challenge. This model provides a system to further investigate the mechanisms and characteristics of HIV cell-to-cell transmission between relevant primary cells that may be analogous to this important mode of virus spread in vivo.

A double-blind, placebo-controlled trial was conducted to study the effects of over-the-counter analgesic/antipyretic medications on virus shedding, immune response, and clinical status in the common cold. Sixty healthy volunteers were challenged intranasally with rhinovirus type 2 and randomized to one of four treatment arms: aspirin, acetaminophen, ibuprofen, or placebo. Fifty-six volunteers were successfully infected and shed virus on at least 4 days after challenge. Virus shedding, antibody levels, clinical symptoms and signs, and blood leukocyte levels were carefully monitored. Use of aspirin and acetaminophen was associated with suppression of serum neutralizing antibody response (P less than .05 vs. placebo) and increased nasal symptoms and signs (P less than .05 vs. placebo). A concomitant rise in circulating monocytes suggested that the suppression of antibody response may be mediated through drug effects on monocytes and/or mononuclear phagocytes. There were no significant differences in viral shedding among the four groups, but a trend toward longer duration of virus shedding was observed in the aspirin and acetaminophen groups.

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Dengue virus (DENV) pathogenesis is related to the host responses to viral infection within target cells, and therefore, this study assessed intracellular changes in host proteins following DENV infection. Two-dimensional gel electrophoresis and mass spectrometry identified upregulation of the host endoplasmic reticulum (ER) chaperone GRP78 in K562 cells following DENV infection, in the absence of virus-induced cell death. Upregulation of GRP78 in DENV-infected cells was confirmed by immunostaining and confocal microscopy and by Western blot analysis and was also observed in DENV-infected primary monocyte-derived macrophages, a natural target cell type for DENV infection. GRP78 was upregulated in both DENV antigen-positive and -negative cells in the DENV-infected culture, suggesting a bystander effect, with the highest GRP78 levels coincident with high-level DENV antigen production and infectious-virus release. Transfection of target cells to express GRP78 prior to DENV challenge did not affect subsequent DENV infection, but cleavage of GRP78 with the SubAB toxin, during an established DENV infection, yielded a 10-to 100-fold decrease in infectiousvirus release, loss of intracellular DENV particles, and a dramatic decrease in intracellular DENV antigen. However, DENV RNA levels were unchanged, indicating normal DENV RNA replication but altered DENV antigen levels in the absence of GRP78. Thus, GRP78 is upregulated by DENV infection and is necessary for DENV antigen production and/or accumulation. This may be a common requirement for viruses such as flaviviruses that depend heavily on the ER for coordinated protein production and processing.The pathogenesis of dengue virus (DENV) disease is multifactorial, and many of the clinical manifestations of the disease, including the life-threatening DENV-induced hemorrhage, may be mediated by the host responses to infection. Many studies have defined altered host responses during DENV infection, including activation of T cells (19) and altered levels of circulating factors in patients (13) and altered release of cytokines and chemokines from DENV-infected cells (8). Transcriptome analyses of DENV-infected endothelial cells (23, 45), HepG2 cells (9), circulating patient cells (39), or peripheral blood mononuclear cells from DENV-infected macaque monkeys (37) have identified alterations in transcripts involved in a variety of cellular processes, including the innate immune response, cell signaling, and metabolic processes. A recent study examined proteomic changes in DENVinfected HepG2 cells and identified 17 altered cellular proteins, including 2 proteins for which the changes were confirmed (32). In the current study, we performed a proteomic analysis of changes due to DENV infection in a target cell population that is relevant to a natural DENV infection and in which DENV-induced cytopathic effect (CPE) and the cellular death response are absent. Two-dimensional gel electrophoresis (2DGE) identified upregulation of glucose-regulated protein 78 (GRP78), otherwise known a...

The ability of dengue virus-infected human monocyte-derived macrophages to induce permeability changes in primary human umbilical vein endothelial cells was investigated. Supernatants from dengue virus type 2-infected monocyte-derived macrophages increased permeability in human umbilical vein endothelial cell monolayers without inducing endothelial cell infection. Production of permeabilising activity from monocyte-derived macrophages occurred after the peak of progeny virus release. TNF-alpha, a known inducer of endothelial cell permeability, was released from dengue virus infected monocyte-derived macrophages but its release did not coincide with release of endothelial cell permeabilising activity. Permeability induction was enhanced by pre-incubation with supernatants from infected monocyte-derived macrophages harvested at the time of peak release of TNF-alpha and infectious virus. Thus, supernatants from dengue virus-infected monocyte-derived macrophages contain factors that increase human umbilical vein endothelial cell permeability, but this is not accompanied by endothelial cell infection or directly correlated with release of dengue virus or TNF-alpha from monocyte-derived macrophages. This model system can be used for further in vitro analysis of mechanisms that may relate to capillary leakage and the development of dengue haemorrhagic fever/dengue shock syndrome.

We have developed a novel linker-primer PCR assay for the detection and quantification of integrated human immunodeficiency virus type 1 (HIV) DNA. This assay reproducibly allowed the detection of 10 copies of integrated HIV DNA, in a background of 2 ؋ 10 5 cell equivalents of human chromosomal DNA, without amplifying extrachromosomal HIV DNA. We have used this assay and a near-synchronous one-step T-cell infection model to investigate the kinetics of viral DNA accumulation following HIV infection. We report here that integrated HIV DNA started accumulating 1 h after the first appearance of extrachromosomal viral DNA and accounted for ϳ10% of the total HIV DNA synthesized in the first round of viral replication. These results highlight the efficient nature of integrase-mediated HIV integration in infected T cells.

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