The murine cytomegalovirus (MCMV) homolog of the HCMV phosphotransferase (UL97(pk)) gene

The murine cytomegalovirus (MCMV) M97 gene is homologous with both eukaryotic protein kinases and the phosphotransferases of herpesviruses. The gene conserves the domain structure of protein kinases and of the human cytomegalovirus UL97 (phosphotransferase) gene. An M97 transcript of 2.5 kb is present predominantly at late times, and much smaller quantities of the transcript are detected at early times postinfection. Comparison of the DNA sequences of the complete M97 genes from 12 ganciclovir-sensitive and aciclovir-sensitive strains of MCMV showed that the sensitive isolates strongly conserve the sequence of the catalytic domains, but have only moderate conservation of the sequence of the amino-terminal (regulatory) region. MCMV provides a useful model for studying the in vivo function of the phosphotransferase genes of the betatherpesviruses and has potential for use in studies of antiviral resistance.

HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype

AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual.

Molecular analyses of human immunodeficiency virus type 1 V3 region quasispecies derived from plasma and peripheral blood mononuclear cells of the first long-term-nonprogressing mother and child pair

Molecular analyses were done for the V3 region quasispecies of human immunodeficiency virus type 1 (HIV-1) strains from plasma and peripheral blood mononuclear cells of the first HIV-1-infected long-term-nonprogressing mother-child pair whose members have survived for >13 years with stable CD4 T cell counts. There was a predominance of lower V3 loop charge and the absence of genotypic changes that are critical in phenotypic determination and tropism during HIV-1 infection. The intrahost genetic diversity between HIV-1 strains from the mother-child pair compared with HIV-1 strains from slow and rapid progressors suggested that a high genetic heterogeneity in HIV-1 strains from this HIV-1-infected long-term-nonprogressing mother and child pair was directly proportional to the length of their immunocompetent period.

The state of maturation of monocytes into macrophages determines the effects of IL-4 and IL-13 on HIV replication

The molecular mechanisms of the effects of IL-4 and IL-13 on HIV infection in human monocytes as they matured into monocyte-derived macrophages over 7 days were investigated using HIV-1(BaL), and low passage clinical strains. IL-4 and IL-13 up-regulated the expression of both genomic and spliced HIV mRNA in monocytes cultured on Teflon, as determined by Northern analysis and p24 Ag assay. Using a nuclear run-on assay, IL-4 stimulation was shown to enhance transcription by two- to threefold. IL-4 stimulated nuclear factor-kappaB nuclear translocation and binding before enhancement of HIV RNA expression. Conversely, IL-4 and IL-13 markedly and significantly inhibited HIV replication at the transcriptional level in monocyte-derived macrophages, and this occurred whether these cytokines were added before or after HIV infection. The reversal from stimulation to inhibition occurred after 3 to 5 days of adherence to plastic. IL-4 had no significant effect on HIV reverse transcription. The effect of both cytokines on the monocyte maturation/differentiation (CD11b, CD13, and CD26) and other macrophage markers (CD14 and CD68) was examined. IL-4 enhanced CD11b, but inhibited CD26 expression and delayed CD13 loss. IL-13 had similar effects on CD11b and CD13, but no effect on CD26. Hence, these cytokines do not simply enhance monocyte differentiation, but have complex and slightly divergent effects that impact on HIV replication probably through cell signaling pathways and nuclear factor-kappaB translocation.

Coinfection and genetic recombination between HIV-1 strains: possible biological implications in Australia and South East Asia

It has been recognised that human immunodeficiency virus (HIV) mutates rapidly and that nucleotide substitutions, deletions, insertions, and rearrangements resulting from recombination events are the main factors that result in variation of the HIV-1 genome. Together, these processes are actively contributing to the diversity and virulence of viral forms comprising the acquired immune deficiency syndrome (AIDS) pandemic. There are 9 HIV-1 subtypes recognised (A-H and O), based on the envelope region segments. Inter-subtype recombination has been already described, whereas intra-subtype recombination has been difficult to detect. In this study, we have identified in vivo genetic recombination between HIV-1 strains belonging to subtype B in a patient who presented both intravenous drug use (IVDU) and homosexual sex as risk factors. Genetic analysis of viral strains in the hypervariable V3 region of the envelope gene indicated the presence of three distinct sequence groups categorized according to their respective tetrapeptide motifs-GPGR, GLGR and GPGK. Detailed genetic and phylogenetic analyses suggested the recombination occurring only between sequence groups with GPGR and GPGK tetrapeptide motifs. These data suggest that coinfection with closely related strains can occur in vivo, and the generation of hybrid HIV-1 genomes via genetic recombination between subtype B strains can result in further antigenic diversity which may thwart diagnosis and future vaccine efforts. Since HIV-1 subtype B is still the most commonly found subtype around the globe, the hybrid genomes between different subtype B strains may result in epidemiologic shifts and altered pathogenesis.

The state of maturation of monocytes into macrophages determines the effects of IL-4 and IL-13 on HIV replication

The molecular mechanisms of the effects of IL-4 and IL-13 on HIV infection in human monocytes as they matured into monocyte-derived macrophages over 7 days were investigated using HIV-1(BaL), and low passage clinical strains. IL-4 and IL-13 up-regulated the expression of both genomic and spliced HIV mRNA in monocytes cultured on Teflon, as determined by Northern analysis and p24 Ag assay. Using a nuclear run-on assay, IL-4 stimulation was shown to enhance transcription by two- to threefold. IL-4 stimulated nuclear factor-kappaB nuclear translocation and binding before enhancement of HIV RNA expression. Conversely, IL-4 and IL-13 markedly and significantly inhibited HIV replication at the transcriptional level in monocyte-derived macrophages, and this occurred whether these cytokines were added before or after HIV infection. The reversal from stimulation to inhibition occurred after 3 to 5 days of adherence to plastic. IL-4 had no significant effect on HIV reverse transcription. The effect of both cytokines on the monocyte maturation/differentiation (CD11b, CD13, and CD26) and other macrophage markers (CD14 and CD68) was examined. IL-4 enhanced CD11b, but inhibited CD26 expression and delayed CD13 loss. IL-13 had similar effects on CD11b and CD13, but no effect on CD26. Hence, these cytokines do not simply enhance monocyte differentiation, but have complex and slightly divergent effects that impact on HIV replication probably through cell signaling pathways and nuclear factor-kappaB translocation.

Twin studies demonstrate a host cell genetic effect on productive human immunodeficiency virus infection of human monocytes and macrophages in vitro

Biological and genetic variability is a prominent feature of human immunodeficiency virus (HIV) strains, especially in tropism, syncytium formation, and replicative capacity. To determine whether there were variable host cell effects on HIV replication in monocytes, three different strains of low-passage-number monocytotropic blood isolates of HIV and the laboratory-adapted strain Ba-L were inoculated into panels of adherent monocytes drawn from 44 different donors, and peak extracellular HIV p24 antigen titers were compared. The clinical HIV strains showed patterns of either moderate or low-level replication in most donor monocytes (20 to 4,000 pg/ml). However, within this range there was marked variation in peak titers in most donors. HIV type 1 Ba-L replicated in all donor monocytes to much higher levels with less variability (30 to 40 ng/ml). Furthermore, replication of 21 clinical blood-derived strains of HIV in blood monocytes and monocyte-derived macrophages (MDM) from pairs of identical twins and age-matched unrelated donors (URD) of the same sex were compared. In all of the seven pairs of identical twins, the kinetics of replication (measured by extracellular HIV p24 antigen) of panels of four clinical HIV type 1 isolates in monocytes were similar within pairs. However, marked and significant differences in kinetics of HIV production occurred within 10 of the 12 unrelated donor pairs (P = 0.0007). The remaining two URD pairs showed similar kinetic patterns, but only one pair had the same HLA-DR genotype. Similar results were observed with monocytes/MDMs obtained from a second bleed of the same donor. Hence, discordant patterns of HIV replication kinetics between URD monocyte pairs contrasted with concordant patterns in identical twin monocytes. These data strongly suggest a host cell genetic effect on productive viral replication in monocytes and MDMs. So far, no consistent genetic linkage of HIV replication pattern with HLA-DR genotype has been observed.

An HIV-1 infected long-term non-progressor (LTNP): molecular analysis of HIV-1 strains in the vpr and nef genes

We describe a long-term non-progressive injecting drug user (IDU) who was infected with human immunodeficiency virus type-1 (HIV-1) in 1984, and has survived with stable CD4+ T-cell counts (> 800/microliters blood) without any acquired immune deficiency syndrome (AIDS) related illness. With a goal to investigate the molecular nature of HIV-1 strains infecting this patient, we amplified the nef and vpr genes directly from the fresh uncultured peripheral blood mononuclear cells (PBMCs), and carried out co-culture studies. Sequence analysis of the nef gene (from 1994 samples) showed no deletions (as has been previously reported) expected for a 7 base pair duplication at the C-terminus which prematurely terminated the nef reading frame, whereas even after repeated attempts the nef gene could not be amplified from the 1992 PBMC samples. In contrast, the vpr gene (from 1992 and 1994 samples) revealed two distinct quasispecies with no apparent defects. We observed five amino acid substitutions, between residues 83-90, at the C-terminus which has been recently implicated in G2 cell cycle arrest as an early step to HIV-1 infection. In the light of recent evidence on the role of nef gene defects/attenuations in long-term survival of HIV-1 infected patients, it may be that the nef gene defect created by gene duplication, which eliminated the cysteine-206 crucial in disulfide bond formation, may play a role in chronic HIV-1 infection in this patient. These data further suggest that deletions in the nef gene may not be the only reason for long-term non-progression of HIV-1 infection in some individuals, but the gene defects like duplication and subtle mutations in the functional motifs of both nef and vpr genes may confer similar protection in HIV-1 infected patients surviving for longer periods of time with stable CD4 counts.

Inhibition of human immunodeficiency virus replication in differentiating monocytes by interleukin 10 occurs in parallel with inhibition of cellular RNA expression

The mechanism of inhibition of HIVBa-L replication by interleukin 10 (IL-10) in primary monocytes and macrophages at various stages of maturation was investigated using semiquantitative PCR for reverse-transcribed HIV DNA, and Northern hybridization for HIV mRNA expression in comparison with extracellular p24 antigen. Pretreatment of monocytes with IL-10 markedly inhibited expression of both unspliced and spliced HIV RNA, reaching a nadir at 7 days and recovering to normal levels by 10 days after a single application. The optimum inhibitory concentration was 25 ng/ml. Less inhibition of HIV RNA expression was observed when IL-10 was added after HIV infection of monocytes and the inhibitory effect progressively declined to negligible levels as monocytes matured into macrophages over 10 days. IL-10 also downregulated the expression of cellular genes, including the transferrin receptor, 28S rRNA, and GAPDH. The kinetics of the inhibition of cellular mRNAs correlated with the inhibition of HIV RNA and also declined as monocytes matured into macrophages. In contrast, IL-10 did not inhibit cellular mRNA expression in the macrophage cell line THP-1. Neutralizing polyclonal antibody to IL-10 reversed all its inhibitory effects. Interaction of IL-10 and TNF-alpha in combination were generally antagonistic in their effects on HIV transcription. IL-10 prevented stimulation of HIV RNA expression by TNF-alpha after preincubation with monocytes for 48 hr. IL-10 had no effect on the levels of HIV cDNA or the process of initiation and completion of reverse transcription. The inhibitory effect of IL-10 on HIV replication in maturing monocytes was probably mediated mainly by inhibition of cellular gene expression and inhibition of maturation of monocytes into macrophages and their activation, with consequent downregulation of HIV mRNA.

The inhibition of HIV replication in monocytes by interleukin 10 is linked to inhibition of cell differentiation

The effect of exogenous recombinant interleukin 10 on the replication of low-passage HIV-1 strains in blood-derived monocytes and monocyte-derived-macrophages (MDMs) was examined at various stages of cell maturation after adherence to the plastic substrate. Interleukin 10 inhibited extracellular production of HIV-1 to a greater degree in monocytes infected within 24 hr of adherence than those infected at 5-7 days. Inhibition of viral production as extracellular p24 antigen was most marked when interleukin 10 was preincubated with monocytes for 24-96 hr (optimum, 48 hr), and increased between 2 and 100 ng/ml. Neutralizing antibody to IL-10 reversed the inhibition. Inhibition of HIV production from monocytes and macrophages was maximal at 1 week after a single addition of cytokine, but then HIV production rose to control levels. Interleukin 10 was also found to inhibit reversibly the normal increase in size and maturation of both uninfected and HIV-infected monocytes during 10-15 days of adherence. In addition, cytoplasmic and membrane expression of CD26, a marker of macrophage maturation, was markedly inhibited but the proportion of detaching, apoptotic, or necrotic cells was also not increased. Hence, interleukin 10 reversibly inhibits both monocyte maturation and HIV production from infected monocytes with similar kinetics, suggesting that inhibition of monocyte maturation by IL-10 may have a marked effect of HIV production by these cells.

The interaction of human fetal neurons and epidermal cells in vitro

The interaction of autologous human fetal neurons with epidermal cells was studied by culturing fetal dorsal root ganglia (DRG) in the center of a dual chamber system with epidermal explants in the outer chamber. The two chambers were separated by two concentric stainless steel annular rings adherent to the substratum by silicon grease and agarose. Axons from the DRG penetrated the agarose barrier, growing into the exterior chamber by 10 d in vitro (DIV) and extended past sparse peripheral fibroblasts to interact specifically with epidermal cells by 12 to 16 DIV. Scanning electron microscopy (SEM) showed single or multiple neuronal fascicles terminating on epidermal cells with spatular, veillike or bulbous axon termini. Transmission electron microscopy (TEM) showed fine axonal termini between epidermal cells, separated by an intercellular gap. The specificity of axonal targeting for epidermal cells rather than fibroblasts was also demonstrated by infecting the DRG with Herpes simplex virus type-1 (HSV-1). Specific anterograde transport of HSV-1 along axons to keratin-expressing epidermal cells was demonstrated by immunofluorescence and immunoperoxidase staining using monoclonal antibodies to viral glycoprotein D. This model allows the study of the mechanism of the specific interactions between neurons and epidermal cells analogous to those in fetal development and after cutaneous nerve regeneration.

Managing HIV. Part 4: Primary therapy. 4.3 The laboratory in managing HIV infection

The CD4 cell count is a useful guide to the clinical stages of HIV infection, although it is only an indirect measure of viral activity. More direct measures of viral load will eventually become part of clinical practice.

Subtype B isolates of human immunodeficiency virus type 1 detected in Australia

The human immunodeficiency virus type 1 (HIV-1) can be subtyped on the basis of nucleotide sequence variability. Knowledge of circulating HIV-1 genotypes or subtypes allows understanding of the origin and spread of HIV-1 in different geographical regions, and is required for rational vaccine development. A study was undertaken to determine the predominant HIV-1 subtype in Australia. Part of the HIV-1 envelope gene (including the variable domain, V3) was sequenced directly from DNA extracted from peripheral blood mononuclear cells of 17 HIV-1 seropositive people in Sydney, Australia. Phylogenetic analysis based on nucleotide sequence suggested that all patients (including individual cases acquired in New Zealand, Papua New Guinea and Thailand) were infected with HIV-1 subtype B. Octapeptides from the HIV-1 envelope V3 loop tip indicated variation but included a predominance of the most common subtype B octapeptides HIGPGRAF (4 cases), NIGPGRAF (3 cases) and PIGPGRAF (1 case). These data suggest that subtype B is the major HIV-1 strain in Australia (and probably in New Zealand and Papua New Guinea), although the importation of HIV-1 acquired overseas is likely to lead to the detection and dissemination of other subtypes in Australia.

Managing HIV. Part 3: Mechanisms of disease. 3.1 Structure and function of HIV

The discovery of HIV in 1983 is a landmark of medical science in the 20th century. HIV is a fragile but stealthy virus that thrives within the cells of the immune system itself, subverting the body's defences against disease. Knowing the structure and life cycle of the virus is the key to understanding how it is transmitted, how it causes disease and how best to prevent or control infection.

Analysis of recombinant and native CD4 by one- and two-dimensional gel electrophoresis

Knowledge of CD4 conformation within the membranes of human lymphoid and monocytoid cells is essential for a clear understanding of its function as a ligand for major histocompatibility complex II (MHC) molecules in T cell activation and for gp120 in human immunodeficiency virus (HIV) infection. The charge and structure of native (nCD4) and soluble recombinant CD4 (rCD4) were examined by one- and two-dimensional (2-DE) electrophoresis antigen mapping and silver staining. Recombinant CD4 was partitioned by nonequilibrium pH gradient electrophoresis (NEPHGE) and revealed a number of differentially charged 44 kDa species (pI > 9.5). Biotinylation (4 h, room temperature) of rCD4 yielded a single labelled species on sodium dodedyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with an increased apparent molecular mass to 50 kDa, consistent with a maximal incorporation of approximately 18 molecules of biotin per rCD4 molecule. The milder biotinylation (15 min, 4 degrees C) of cell-(CEM-T4, THP-1) expressed CD4 was not accompanied by any apparent alteration in molecular weight, nor abrogation of CD4 antigenicity. This was determined by isolation of nCD4 by immunoprecipitation and SDS-PAGE immunoblotting, using anti-CD4 mAbs (leu3a, OKT4A, Q4120, T4, OKT4, Q425) and by flow cytometry (leu4a, T4). The immunoprecipitation of full-length native CD4 from lymphoid MT2 and CEM-T4 cell extracts, however, revealed both monomeric and higher-order CD4 antigen complexes by immunoblotting. These studies describe the biotinylation, 1-DE and 2-DE of CD4 preparations, and indicate the capacity of CD4 of lymphocytes to form complexes which may influence CD4 conformation and epitope availability.

Herpes simplex virus protein targets for CD4 and CD8 lymphocyte cytotoxicity in cultured epidermal keratinocytes treated with interferon-gamma

In early recurrent herpetic lesions, CD4 T lymphocytes are the predominant infiltrating cells, and keratinocytes expressing major histocompatibility complex (MHC) class II antigens, induced by interferon-gamma (IFN-gamma), are the major site of herpes simplex virus (HSV) replication. IFN-gamma pretreatment of human keratinocytes in vitro reduced MHC class I antigen down-regulation by HSV-1 infection and induced expression of HLA-DR that was unaltered by subsequent HSV-1 infection. Incubation of these infected keratinocytes with phosphonoacetic acid (PAA) almost completely inhibited expression of four major HSV glycoproteins, although expression of early proteins was not affected. Weak CD8 T lymphocyte cytotoxicity against IFN-gamma-stimulated, HLA-DR-expressing HSV-1-infected keratinocytes was consistently directed to the immediate early/early proteins (all 9 patients tested) but against late proteins to a lesser degree (4/9 patients). However, CD4 T lymphocyte cytotoxicity was much greater and directed predominantly against late HSV-1 glycoproteins (all 9 subjects tested) in these cells.