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P U Cameron

Publications and source records attributed to P U Cameron.

At least 19 recordsLinked to original sources
PubMed2003

CD4 is expressed by epidermal Langerhans' cells predominantly as covalent dimers.

Langerhans' cells (LC) of skin are CD4 expressing, dendritic, antigen-presenting cells, that are essential for activation of primary immune responses and are productively infected by HIV. We have shown previously that lymphocytes and monocytes express CD4 both as monomers and covalently linked homodimers. In those cells the 55-kDa monomer structure predominates. LC in un-fractionated human epidermal cell (EC) suspension also expresses both forms of CD4, but in EC the dimer form is predominant. Because isolation of LC into single cell suspension by trypsin, as is routinely used for LC isolation, degrades CD4, a systematic study for an alternate procedure for LC isolation was performed. Thus it was found that collagenase blend F treatment can efficiently release LC into suspension, under conditions of only minimal degradation of control soluble recombinant CD4 or CEM-T4 or THP-1 cell CD4, or importantly of LC surface CD4. SDS-PAGE immunoblotting of purified LC extracted from EC by collagenase confirmed CD4 structure as predominantly 110-kDa dimers, with only minimal 55-kDa monomers. The suitability of LC prepared thus for functional studies was demonstrated with binding of functional ligand HIV gp120. It remains to be determined, however, why tissue embedded LC express mainly CD4 dimers, but single-celled blood lymphocytes and monocytes mainly monomers.

Antigens, CD1↗
PubMed2001

Attenuated and wild-type HIV-1 infections and long terminal repeat-mediated gene expression from plasmids delivered by gene gun to human skin ex vivo and macaques in vivo.

Gene expression from HIV-based gene therapy vectors or live-attenuated HIV-1 vaccines requires RNA transcription supported by the HIV-1 promoter, the long terminal repeat (LTR). Delivery of live-attenuated HIV-1 vaccines as plasmid DNA would overcome problems associated with production of attenuated HIV-1 strains. We investigated the expression of reporter plasmids and proviral HIV-1 constructs driven by either the HIV-1 LTR or LTRs with deletions in the U3 enhancer regions. LTR-driven plasmids were inoculated by gene gun into both human epidermis ex vivo and macaques in vivo. The HIV-1 LTR drove reporter gene expression in human and macaque skin, although with 15- to 20-fold less efficiency compared to the immediate-early cytomegalovirus promoter. A deleted LTR derived from a naturally attenuated HIV-1 strain infecting a member of the well-characterized Sydney Blood Bank Cohort of long-term nonprogressors was 5-fold less efficient in expression of the reporter gene compared to wild-type LTR. Delivery of proviral wild-type HIV-1 DNA constructs to human skin resulted in recovery of HIV-1 from cells emigrating from the epidermis, providing an ex vivo model of the infectivity of proviral HIV-1 DNA. However, delivery of proviral HIV-1 DNA containing deletions in either the LTR, Nef, or the secondary viral transcription activator,Vpr, significantly reduced HIV-1 replication in this model. The early coexpression of Tat from a second plasmid did not restore replication. Thus, although attenuated lentiviral vaccines might be deliverable as proviral DNA constructs in primate subjects, significant improvements are needed to enhance the efficiency of this method.

AIDS Vaccines↗
PubMed2001

Bitter-sweet symphony: defining the role of dendritic cell gp120 receptors in HIV infection.

BACKGROUND: Dendritic cells (DC) are believed to be one of the first cell types infected during HIV transmission. Recently a single C-type lectin receptor (CLR), DC-SIGN, has been reported to be the predominant receptor on monocyte derived DC (MDDC) rather than CD4. The role of other CLRs in HIV binding and HIV binding by CLRs on other types of DC in vivo is largely unknown. OBJECTIVES AND STUDY DESIGN: Review HIV binding to DC populations, both in vitro and in vivo, in light of the immense interest of a recently re-identified CLR called DC-SIGN. RESULTS AND CONCLUSIONS: From recent work, it is clear that immature MDDC have a complex pattern of HIV gp120 binding. In contrast to other cell types gp120 has the potential to bind to several receptors on DC including CD4 and several types of C type lectin receptor, not just exclusively DC-SIGN. Given the diverse types of DC in vivo future work will need to focus on defining the receptors for HIV binding to these different cell types. Mucosal transmission of HIV in vivo targets immature sessile DCs, including Langerhans cells which lack DC-SIGN. The role of CLRs and DC-SIGN in such transmission remains to be defined.

Animals↗
PubMed2001

Uptake of HIV and latex particles by fresh and cultured dendritic cells and monocytes.

Blood dendritic cells (DC) efficiently carry HIV-1 and transmit infection to CD4+ T cells in the absence of productive infection of the APC. Fluorescent latex beads were used to define the endocytic pathways that may contribute to this non-infectious pathway of virus carriage. Beads between 14 nm and 2300 nm in diameter were taken up by uncultured blood DC, but uptake of beads larger than 280 nm was much reduced in the DC compared to monocytes. After culture, there was a reduction in bead carriage in DC compared to monocytes. In the DC, beads were found as small aggregates in class II containing compartments or as single beads just below the cell surface. Beads accumulated in monocytes as aggregates in class II negative compartments. Bead recycling occurred in DC, but not in the fresh or cultured monocytes. Electron microscopy of HIV-1-pulsed DC cultured with CD4+ T cells showed accumulation of apoptotic debris and virions within endosomes in the DC. The peripheral location and recycling of endocytosed material in DC provides a pathway for virion transfer from DC to T cells that does not occur in monocytes.

Cells, Cultured↗
PubMed2001

Infectivity of wild-type and deleted proviral SIV DNA.

Live attenuated lentiviruses are potentially effective candidate HIV vaccines; however, delivery of these viruses in the field would be problematic. Delivery of attenuated lentiviruses as proviral DNA would be a simple means of immunization, but the efficiency of this method of delivery is not known. In this study, macaques were readily infected following inoculation of plasmid DNA encoding proviral simian immunodeficiency virus (SIVmac239), whether given i.m. (300 microg) or epidermally (15 microg), with all four animals succumbing to AIDS at a mean of 26 weeks following inoculation. Using a human skin explant model, we found that the 50% infectious dose (ID50) of proviral SIV or HIV-1 plasmid may be as low as 1 microg when delivered to skin by gold particle bombardment using a gene gun. An infectious proviral clone of SIV mac239 with a 105 bp deletion in the 3' nef/LTR overlap region was engineered (SIVsbbc delta3), analogous to the initial common nef/LTR deletion in HIV-1 strains isolated from an Australian cohort of long-term slow-progressors. Two further macaques were also readily infected with SIVsbbc delta3 after i.m. injection of 300 microg of highly purified plasmid DNA. Unexpectedly, in one macaque inoculated with SIVsbbc delta3 DNA, SIV strains isolated three to six weeks after infection had completely repaired the nef/LTR deletion with wild-type sequence, and eventually progressed to AIDS. The mechanism used to rebuild this deletion with wild-type sequence, presumably derived from an intact 5' LTR, is unclear, but possibilities include RNA read-through errors from the plasmid DNA and recombination with residual plasmid DNA at the inoculation site.

Animals↗
PubMed2000

Efficacy and kinetics of glycerol inactivation of HIV-1 in split skin grafts.

Allogeneic split skin grafts are used widely in the treatment of burns. The relative simplicity of glycerol preservation of skin suggests it will be used increasingly in areas of high HIV-1 seroprevalence. The ability of glycerol preservation to inactivate HIV-1 present in skin graft infected in vitro was determined using a macrophage tropic strain HIV-1 as a cell-free virus suspension, within infected PBMCs, or within in vitro HIV-1 infected fresh cadaveric split skin. Different temperatures and concentrations of glycerol were used and infectivity determined by coculture with mitogen activated peripheral blood mononuclear cells (PBMCs) and measurement of reverse transcriptase activity after 7-10 days. Cell-free HIV-1 was inactivated within 30 min at 4 degrees C in glycerol concentrations of 70% or higher. During similar exposure cell- or skin-associated HIV-1 titer was reduced but not eliminated with 70% and 85% glycerol at 4 degrees C. HIV-1 was recovered consistently from skin stored in 85% glycerol at 4 degrees C for up to 72 hr but virus isolation was infrequent after storage for more than 5 days. At 20 degrees C or 37 degrees C, 70% or 85% glycerol could inactivate cell- or skin-associated HIV-1 within 8 hr. The initial glycerolization procedures and the storage at 4 degrees C eliminated effectively HIV-1 from skin.

Cadaver↗
PubMed2000

Induction of osteoclasts from CD14-positive human peripheral blood mononuclear cells by receptor activator of nuclear factor kappaB ligand (RANKL).

Osteoclasts are bone-resorbing cells that are derived from haemopoietic precursors, including cells present in peripheral blood. The recent identification of RANKL [receptor activator of nuclear factor (NF)-kappaB ligand], a new member of the tumour necrosis factor ligand superfamily that has a key role in osteoclastogenesis, has allowed the in vitro generation of osteoclasts in the absence of cells of the stromal/osteoblast lineage. Human peripheral blood mononuclear cells (PBMC) cultured in vitro with soluble RANKL and human macrophage colony-stimulating factor form osteoclasts. However, PBMC are heterogeneous, consisting of subsets of monocytes and lymphocytes as well as other blood cells. As the CD14 marker is strongly expressed on monocytes, the putative osteoclast precursor in peripheral blood, we have selected CD14(+) cells from PBMC to examine their osteoclastogenic potential and their expression of novel members of the tumour necrosis factor superfamily involved in osteoclastogenesis. Highly purified CD14(+) cells demonstrated mRNA expression of receptor activator of NF-kappaB, but no expression of RANKL or osteoprotegerin, whereas PBMC expressed mRNAs for all three factors. CD14(+) (but not CD14(-)) cells cultured on bone slices for 21 days with human macrophage colony-stimulating factor and soluble RANKL generated osteoclasts and showed extensive bone resorption. Similar numbers of osteoclasts were generated by 10(5) CD14(+) cells and 10(6) PBMC, but there was significantly less intra-assay variability with CD14(+) cells, suggesting the absence of stimulatory/inhibitory factors from these cultures. The ability of highly purified CD14(+) cells to generate osteoclasts will facilitate further characterization of the phenotype of circulating osteoclast precursors and cell interactions in osteoclastogenesis.

Bone Resorption↗
PubMed1999

Periodontal attachment loss in HIV-infected patients is associated with the major histocompatibility complex 8.1 haplotype (HLA-A1,B8,DR3).

Periodontal attachment loss is mediated by overproduction of tumour necrosis factor (TNF) and interleukin (IL)-1, and appears to have a genetic component. The 8.1 major histocompatibility complex (MHC) ancestral haplotype (HLA-A1,B8,TNFA-308(2),DR3) is associated with elevated TNF production and predisposes carriers to several autoimmune/immunopathological disorders, including rapid progression of HIV disease, but not early onset periodontal disease in healthy individuals. Rather a high proportion of subjects with severe periodontal disease carry allele 2 at IL-1A-889 and IL-1B+3953. We predicted that genetic associations may be different or clearer in HIV patients, as they often show elevated production of TNF and IL-1 and periodontal attachment loss. Hence periodontal parameters and IL-1 polymorphisms were assessed in HIV-positive subjects expressing HLA-B8 with or without other markers of the 8.1 haplotype. Of 16 HLA-B8 subjects, 13 demonstrated elevated probing pocket depth and clinical attachment loss. The difference was statistically significant and did not correlate with smoking, age, CD4 T-cell counts, HIV viral load or levels of dental plaque. As TNFA-308 (allele 2) was present in four non-B8 subjects who had minimal attachment loss, it may not mediate the effect of the 8.1 haplotype. Moreover, polymorphisms at IL-1A-889 and IL-1B+3953 did not significantly affect periodontal parameters. Thus a central MHC gene characteristic of the 8.1 haplotype was the clearest determinant of periodontal attachment loss in HIV-infected individuals.

Adult↗
PubMed1999

Monocyte-derived dendritic cells as a model for the study of HIV-1 infection: productive infection and phenotypic changes during culture in human serum.

Dendritic cells (DC) have been implicated in the initial selection for macrophage-tropic HIV-1 during transmission and in the generation of high-level virus replication during interactions with CD4 T cells. The role of DC as viral reservoirs and the extent of productive infection is unclear, but the ability to generate large numbers of DC from blood monocytes has produced a tractable model for study of DC-HIV-1 interactions. When cultured in granulocyte-macrophage colony stimulating factor and IL-4, sorted CD14+ monocytes rapidly lost phagocytic function for both 93 nm and 977 nm latex particles and developed the surface markers and function of DC. After 7 days, when returned to medium containing human serum without cytokines, some monocyte-derived dendritic cells (MDDC) became adherent, but retained the costimulatory markers CD80 and CD86 and continued to express CD83 and CD40. The MDDC stimulated allogeneic CD4 T cells, did not express new macrophage markers and remained non-phagocytic. With or without TNF-alpha, MDDC generated in cytokines were infected by macrophage and T cell-tropic virus and produced higher reverse transcriptase levels than did the autologous monocyte-derived macrophages (MDM). When added to T cells, the infected MDDC were able to infect T cells with a wider range of viral isolates than were MDM.

Antigens, CD↗
PubMed1998

Specificity of binding of HIV-1 anti-p24 antibodies to CD4+ lymphocytes from HIV-infected subjects.

The clinical utility of a flow cytometric assay (FCA) for intracellular HIV p24 antigen was evaluated in a group of HIV-1-infected subjects. A previously described method, p24-FCA (1), was modified to minimize nonspecific staining and to include irrelevant isotype-matched control antibodies. Blood mononuclear cells from 32 HIV-1 seropositive subjects and 14 HIV-1 seronegative controls were examined. In HIV-1 seropositive individuals, the proportion of CD4+ lymphocytes that bound the p24 monoclonal and the isotype control antibodies were not different. The frequency of cells binding p24 antibodies increased with declining CD4 counts and was highest in patients with low CD4+ lymphocyte counts. Although results of p24-FCA do reflect disease progression, the high nonspecific binding of monoclonal antibodies in infected subjects obscures specific p24 binding and precludes its use as an accurate measure of infection within single cells.

Antibody Specificity↗
PubMed1998

HIV-1 selection by epidermal dendritic cells during transmission across human skin.

Macrophage tropic HIV-1 is predominant during the initial viremia after person to person transmission of HIV-1 (Zhu, T., H. Mo, N. Wang, D.S. Nam, Y. Cao, R.A. Koup, and D.D. Ho. 1993. Science. 261:1179-1181.), and this selection may occur during virus entry and carriage to the lymphoid tissue. Human skin explants were used to model HIV-1 selection that may occur at the skin or mucosal surface. Macrophage tropic, but not T cell line tropic strains of HIV-1 applied to the abraded epidermis were recovered from the cells emigrating from the skin explants. Dermis and epidermis were separated by dispase digestion after virus exposure to determine the site of viral selection within the skin. Uptake and transmission to T cells of all HIV-1 isolates was found with the dermal emigrant cells, but only macrophage tropic virus was transferred by emigrants from the epidermis exposed to HIV-1, indicating selection only within the epidermis. CD3+, CD4+ T cells were found in both the dermal and epidermal emigrant cells. After cell sorting to exclude contaminating T cells, macrophage tropic HIV-1 was found in both the dermal emigrant dendritic cells and in dendritic cells sorted from the epidermal emigrants. These observations suggest that selective infection of the immature epidermal dendritic cells represents the cellular mechanism that limits the initial viremia to HIV-1 that can use the CCR5 coreceptor.

CD4-Positive T-Lymphocytes↗
PubMed1996

The interaction of macrophage and non-macrophage tropic isolates of HIV-1 with thymic and tonsillar dendritic cells in vitro.

Dendritic cells isolated from thymus and tonsil were tested for susceptibility to HIV-1 strains that are tropic for macrophages or for T cell lines. DCs were purified by cell sorting and before infection expressed high levels of CD4 and HLA-DR and lacked markers for T, B, NK cells, or macrophages. Viral entry and reverse transcription was found after pulsing with strains of HIV-1 that could infect macrophages. During the first 36 h the PCR signals for gag sequences increased in DCs and macrophages. In contrast little if any viral DNA was found after pulsing macrophages or DCs with HIV-1 that was able to infect T cell lines. DCs pulsed with HIV-1 were able to transmit infection to responding T cells during an allogeneic or superantigen response. Selection for virus able to infect lymphoid DCs and other DCs expressing CD4 and its transfer to T cells during subsequent immune responses may provide a mechanism for the observed predominance of macrophage-tropic HIV-1 after in vivo transmission.

CD4 Antigens↗
PubMed1995

Human immunodeficiency virus 1 reservoir in CD4+ T cells is restricted to certain V beta subsets.

The human immunodeficiency virus 1 (HIV-1) replicates more efficiently in T-cell lines expressing T-cell receptors derived from certain V beta genes, V beta 12 in particular, suggesting the effects of a superantigen. The targeted V beta 12 subset was not deleted in HIV-1-infected patients. It was therefore possible that it might represent an in vivo viral reservoir. Viral load was assessed by quantitative PCR with gag primers and with an infectivity assay to measure competent virus. It was shown that the tiny V beta 12 subset (1-2% of T cells) often has a higher viral load than other V beta subsets in infected patients. Selective HIV-1 replication in V beta 12 cells was also observed 6-8 days after in vitro infection of peripheral blood lymphocytes from normal, HIV-1 negative donors. Viral replication in targeted V beta subsets may serve to promote a biologically relevant viral reservoir.

Adult↗
PubMed1994

Conjugates of dendritic cells and memory T lymphocytes from skin facilitate productive infection with HIV-1.

Experimentally, a productive infection with HIV-1 requires that virus be administered to T cells that are activated by mitogens. We describe a productive milieu for HIV-1 within the confines of normal skin that does not require standard stimuli. The milieu consists of dendritic cells and T cells that emigrate from skin and produce distinctive stable, nonproliferating conjugates. These conjugates, upon exposure to each of seven different HIV-1 isolates, begin to release high levels of virus progeny within 4 days. Numerous infected syncytia, comprised of both dendritic and T cells, rapidly develop. We propose that conjugates of dendritic cells and T cells, as found in the external linings of organs involved in sexual transmission of HIV-1, represent an important site for the productive phase of HIV-1 infection. Because the affected T cells carry the memory phenotype, this site additionally provides a mechanism for the chronic depletion of CD4+ memory cells in HIV-1 disease.

CD4-Positive T-Lymphocytes↗
PubMed1994

Susceptibility of dendritic cells to HIV-1 infection in vitro.

We review recent work on the extent of HIV-1 infection of dendritic cells (DCs) and the consequences of exposure to virus. The reported levels of infection of DCs from blood have varied from "explosive" to "undetectable." The only study that used sorted DCs demonstrated little if any infectability, which may not be surprising given the very low levels of CD4 on the populations that were studied. HIV-1-pulsed, highly purified DCs function as potent antigen-presenting cells during the mixed leukocyte reaction and responses to superantigens. At the same time that the HIV-1-pulsed DCs stimulate CD4+ T cells in DC-T clusters, the virus is transferred to the responding lymphocytes and a vigorous productive infection of the T cells takes place. This pool of transferable HIV-1 is short lived in cultured human blood DCs and likely reflects the capacity of these cells to internalize and recycle vesicles in the endocytic pathway, as revealed with experiments using 0.1-micron fluorescent latex beads. Current efforts are directed to analyzing the interaction of HIV-1 with several populations of DCs that express higher levels of CD4. These include DCs studied in fresh, uncultured blood, as well as skin, thymus, and tonsil DCs. In each case, entry and reverse transcription of HIV-1 are seen, but again, coculture with T cells is required for a productive infection to take place. We conclude that DCs could play a critical role in the pathogenesis of HIV-1 infection, but that the interaction with CD4+ T cells is a critical variable in analyzing the extent of productive infection and its consequences.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Expression of CD11/CD18 and ICAM-1 on monocytes and lymphocytes of HIV-1-infected individuals.

The role of the leukocyte integrins in the infection of cells by HIV-1 or in the progression of AIDS-related disease is of continuing interest. Using a dual-labeling flow cytometric method, we determined the level of expression of the leukocyte integrins and intercellular adhesion molecule 1 (ICAM-1) on monocytes and lymphocytes from HIV-1-infected and uninfected individuals. The mean fluorescence of CD18 on lymphocytes and CD11c on monocytes of HIV-1-infected subjects was significantly higher than for the control group (P = .008 and .014, respectively). There was a trend toward higher fluorescence of CD11a on lymphocytes from HIV-1-infected subjects compared with cells from the control group (P = .089). Integrin expression on lymphocytes or monocytes from HIV-infected individuals did not correlate with their CD4 lymphocyte number. However, the mean fluorescence associated with ICAM-1 on monocytes and CD11a and CD18 expression on lymphocytes was related to clinical stage of disease.

Acquired Immunodeficiency Syndrome↗