Susceptibility of human peripheral blood dendritic cells to infection by human immunodeficiency virus

Preparations of human peripheral blood dendritic cells have been infected with human immunodeficiency virus (HIV). After 5 days in culture they were examined by electron microscopy. Virus was observed budding from the plasma membrane of dendritic cells and mature virions were observed on the cell surface. In addition, a second cell type, similar in morphology to 'classical' dendritic cells but containing numerous cytoplasmic granules, was also found to support replication of the virus. We speculate that the growth of HIV in dendritic cells could cause immunosuppression by impairing antigen presentation.

L6 skeletal muscle cells have functional V1-vasopressin receptors coupled to stimulated inositol phospholipid metabolism

The effects of vasopressin and related peptides upon the rat skeletal muscle cell line, L6, have been examined. No effects upon cellular cyclic AMP levels were found indicating that L6 cells possess no functional V2-vasopressin receptors. Vasopressin and its analogues did, however, stimulate the rapid and dose-dependent accumulation of inositol phosphates. This effect and the rank order of potency of vasopressin analogues demonstrate the presence of functional V1-vasopressin receptors upon L6 cells. These results suggest that the L6 line may be a useful model for vasopressin effects upon skeletal muscle metabolism.

Analysis of antigenic determinants on internal and external proteins of influenza virus and identification of antigenic subpopulations of virions in recent field isolates using monoclonal antibodies and immunogold labelling

An electron microscopic immunogold labelling technique employing monoclonal antibodies has been applied to the antigenic analysis of influenza A and B viruses. Reassortant influenza A H3N2 viruses containing haemagglutinin molecules from viruses isolated between 1968 and 1982 were analysed with a panel of monoclonal antibodies raised against viruses which appeared over the same period. The immunogold labelling technique clearly demonstrated the antigenic drift in the haemagglutinin molecule that occurred between 1968 and 1982. When the technique was applied to the examination of viruses from a more geographically restricted influenza epidemic in a semi-closed community, antigenic variants were found. Furthermore the technique enabled the identification of distinct antigenic variant subpopulations within a single clinical isolate. Analysis of the HA of MDCK cell or egg grown virus by this procedure provided data to support the hypothesis that the host cell exerts selective pressure on subpopulations of virus resulting in the emergence of antigenic variants.

Early interactions between animal viruses and the host cell: relevance to viral vaccines

Viral recognition of specific receptors in the host cell plasma membrane is the first step in virus infection. Attachment is followed by a redistribution or capping of virus particles on the cell surface which may play a role in the uptake process. Certain viruses penetrate the plasma membrane directly but many, both enveloped and non-enveloped viruses, are endocytosed at coated pits and subsequently pass into endosomes. The low pH environment of the endosome facilitates passage of the viral genome into the cytoplasm. For some viruses the mechanism of membrane penetration is now known to be linked to a pH-mediated conformational change in external virion proteins. As a consequence of infection there are alterations in the permeability of the plasma membrane which may contribute to cellular damage. Recent advances in the understanding of these processes are reviewed and their relevance to the development of new strategies for vaccines emphasised.

Isolation of retroviruses from two patients with "common variable" hypogammaglobulinaemia

Retroviruses related to human T-lymphotropic virus III/lymphadenopathy-associated virus (HTLV-III/LAV) have been isolated from peripheral-blood mononuclear cells of two patients with "common variable" hypogammaglobulinaemia who were being treated with intravenous gammaglobulin. One has had three different opportunistic infections. In both patients hypogammaglobulinaemia developed within 6 years of a longlasting undiagnosed viral-like illness in adolescence, and it is suggested that the virus causing that illness also gave rise to the hypogammaglobulinaemia. However, iatrogenic infection from intravenous gammaglobulin cannot be ruled out.

Infection of cultured human muscle cells by influenza virus

In a search for myotropic viruses with a potential to initiate muscle autoimmunity, we found that two strains of influenza A virus, A/England/863/78 (H3N2) and the reassortant virus X-47 (H3N2), could infect human syncytial myotubes lytically. The X-47 strain could, in addition, infect unicellular precursor myoblasts. Intracellular viral protein synthesis was demonstrated by pulse-labelling studies in both cell types with both virus strains. By immunofluorescence and immunoelectron microscopy, viral antigens were demonstrated in infected muscle cells specifically identified by double staining with monoclonal antibodies to either of two independent muscle-specific antigens. However, using 'co-capping' techniques in conjunction with electron microscopy, there was no evidence of association between viral haemagglutinin and the acetylcholine receptor (one major target of autoimmunity to muscle cells) on the infected cell membrane.

Relationship between large granular lymphocytes and NK-1.2+ cells from normal and poly(inosinic:cytidylic acid) (poly(I:C]-treated mice

The present work analyzes the relationship between large granular lymphocytes (LGL), NK-1.2+ cells, and natural killer (NK) activity of C3H/HeN mice. Different hematic cell fractions were obtained according to their nylon-wool adherence and density on Percoll gradients. NK-1.2+ cells (8% of nucleated cells) were more numerous than LGL (3% of nucleated cells) in the input blood population. Eighty-five percent of LGL were recovered from the sorted NK-1.2+ cell fraction. After incubation on nylon-wool column, 63% of LGL and 36% of NK-1.2+ were eluted in the nonadherent fraction. Eighteen percent of NK-1.2+ cells were recovered from the most adherent elutable cell fraction. After the discontinuous Percoll gradient most LGL were present in the low-density fractions while 20% of NK-1.2+ cells were recovered from the highest-density fraction. NK activity was significant both in the nylon-wool-nonadherent and -adherent fractions. After the Percoll gradient most NK activity was present in the low-density fractions. In the present experimental conditions treatment poly(inosinic:cytidylic acid) (poly(I:C] did not increase the numbers of LGL and NK-1.2+ cells either in the blood or in the spleen. However it increased significantly the NK activity of the input cell populations and of the nonadherent and low-density fractions. Similarly, exposure of specific pathogen-free (SPF) mice to non-SPF conditions stimulated NK cytotoxicity but did not alter the percentage of LGL in the blood or in the spleen. Poly(I:C) treatment induced a shift of LGL and NK-1.2+ cells toward the low-density fractions. In poly(I:C)-treated mice images of granule secretion from LGL were detected. Taken together, the present results indicate that LGL and NK-1.2+ cell populations do not totally overlap. Moreover subpopulations of LGL and NK-1.2+ cells can differ in NK activity, morphology, density, adherence to nylon wool, and response to poly(I:C).

The structure and biosynthesis of epidermal growth factor precursor

The structure of mouse submaxillary gland epidermal growth factor (EGF) precursor has been deduced from complementary DNAs. The mRNA is approximately 4800 bases and predicts prepro EGF to be a protein of 1217 amino acid residues (133 X 10 Mr). EGF (53 amino acid residues) is flanked by polypeptides of 188 and 976 residues at its carboxy and amino termini, respectively. The amino terminus of the precursor contains seven cysteine-rich peptides that resemble EGF. Towards the carboxy terminus is a 20-residue hydrophobic membrane spanning domain. The mild portion of the EGF precursor shares a 33% homology with the low density lipoprotein receptor, which extends over 400 amino acid residues. These features suggest that EGF precursor could function as a membrane-bound receptor. RNA dot-blot analysis and in situ hybridization show EGF mRNA to be abundant in the submaxillary gland, kidney and incisor tooth buds. Lower EGF mRNA levels were found in the lactating breast, pancreas, small intestine, ovary, spleen, lung, pituitary and liver. In the kidney EGF mRNA was most abundant in the distal convoluted tubules. Analysis of EGF precursor biosynthesis in organ culture of the submaxillary gland and kidney showed differential processing of the precursor in the two tissues. In the submaxillary gland immunoreactive low molecular weight EGF was produced, but in the kidney the high molecular weight precursor was not processed. In the distal convoluted tubule of the kidney EGF precursor may act as a receptor that is involved in ion transport.

Biology of cloned cytotoxic T lymphocytes specific for lymphocytic choriomeningitis virus: clearance of virus and in vitro properties

We have generated lymphocytic choriomeningitis virus-specific, H-2-restricted cytotoxic thymus-derived lymphocyte (CTL) clones. By using these reagents in several in vitro assays with infected target cells, we show that CTLs by themselves prevent the release of infectious virus into culture fluids and significantly lower the titers of infectious virus previously produced. This ability of cloned CTLs is not influenced by monensin. However, monensin does abrogate the ability of CTLs from spleens of mice primed 6 to 8 days previously with virus to kill virus-infected syngeneic targets. When tested for the participation of lymphokines in this system, the CTLs proliferate when reacted with syngeneic lymphocytic choriomeningitis virus-infected macrophages but fail to make interleukin-2. These CTLs make gamma interferon when reacted with syngeneic virus-infected targets. However, the production of interferon does not directly correlate with CTL-mediated killing. The number of H-2K and D molecules expressed on the target cell surface is not altered during the course of lymphocytic choriomeningitis virus infection. Electron microscopy shows finger-like projections of the CTL clone thrust into the infected cell and lesions bearing an internal diameter of approximately 15 nm in those membranes, illustrating the lytic process.

Ultrastructural and immunofluorescence studies of early events in adenovirus-HeLa cell interactions

Scanning electron microscopy and immunofluorescence techniques show that the attachment of adenovirus type 5 to HeLa cells is followed by a temperature-dependent redistribution of virus particles on the cell surface. Metabolic inhibitors and cytochalasin B, a drug that impairs microfilament function, blocked this redistribution. Transmission electron microscopy studies demonstrated that inhibition of redistribution was paralleled by an inhibition of virus internalization. In further experiments virus and cells were incubated at 4 degrees C and then treated with adenovirus 'soluble' antigens to block unoccupied virus receptors. On warming these preparations to 37 degrees C, the internalization of attached virions was found to be impaired. It is proposed that energy-dependent redistribution of attached adenovirus particles on the cell surface facilitates entry by bringing virions into contact with sufficient receptors to allow internalization.

Thiourea prevents cytotoxicity and mutagenicity, but not sister-chromated exchanges in V79 cells treated with cis-diaminedichloroplatinum (II)

This work shows that cis-diaminedichloroplatinum(II)'s (cis-DDP) mutagenicity, as well as its cytotoxicity, can be prevented by subsequent treatment with thiourea. Sister-chromatid exchanges (SCE) induced by cis-DDP are only partially prevented by thiourea under conditions where mutagenicity is totally inhibited. A 4.5-h delay in the addition of thiourea following cis-DDP treatment results in an almost complete loss of its ability to prevent mutagenicity, but only a partial loss of its ability to prevent cytotoxicity and sister-chromatid exchanges.

Evidence of diffusion artefacts in diaminobenzidine immunocytochemistry revealed during immune electron microscope studies of the early interactions between influenza virus and cells

Anti-haemagglutinin-labelled antibodies have been used to search for influenza entry into cells by fusion of viral and plasma membranes. The plasma membranes of infected cells were stained by immunoperoxidase but not by immunoferritin reagents. It is suggested that the staining obtained with the peroxidase conjugate was due to diffusion of the diaminobenzidine reaction product away from the enzymic site. Immunoferritin labelling provided no evidence for entry of influenza by fusion of viral and plasma membranes under conditions of physiological pH.

Polymorphism of the NS1 proteins of type A influenza virus

The type-specific non-structural protein 1 (NS1) of influenza A viruses was found to be heterogeneous with respect to charge, varying in pI by more than two orders of magnitude, and to phosphorylation. Phosphorylation was strain-specific, variable in extent between strains, and in some strains NS1 proteins were not detectably phosphorylated. Phosphorylation was not responsible for the major variations in charge as, paradoxically, the most acidic NS1 proteins were not phosphorylated. Cytoplasmic inclusions, which are formed between NS1 proteins and cellular RNA in infections with a number of human strains, were absent from A/FP/Rostock-infected cells and do not, therefore, appear to be essential in virus multiplication. We suggest that the acidic nature of the NS1 of A/FP/Rostock may prevent it from binding RNA and hence from forming inclusions. The variation in charge of NS1 proteins which we determined experimentally correlates with the overall differences in charge adduced from published amino acid sequence and implications of this variability to the biological role of NS1 are discussed.

Replication of human respiratory coronavirus strain 229E in human macrophages

Evidence for the replication of human coronavirus strain 229E (HCV 229E) in macrophages is presented. Virus antigen was detected in macrophages by an immunofluorescent technique 24 h after infection and virus particles were observed in the cisternae of the endoplasmic reticulum by electron microscopy. Giant cells were observed by light and scanning electron microscopy, and large multinucleate cells were seen by thin-section electron microscopy, suggesting that HCV 229E can induce syncytial formation in cultured human macrophages. Furthermore, the production of infectious virus by macrophages was demonstrated by an infectious centre assay.

Effect of iron saturation on transferrin uptake by reticulocytes. A morphological study

The presence of iron on the transferrin molecule increases its affinity for and sojourn time on the reticulocyte. This could be due to selective internalization of iron-containing transferrin molecules. This possibility was investigated by electron microscopic autoradiography. Rabbit reticulocytes were incubated with rabbit transferrin at 6, 33, and 72% iron saturations, and the distribution of transferrin molecules at membrane and intracellular locations was assessed by grain counting. The results showed that (1) both apotransferrin and iron transferrin enter the cell interior and (2) the amount of intracellular transferrin was primarily controlled by the concentration of membrane-bound transferrin and not by its iron saturation.

IgE plasma cells in human jejunum demonstrated by immune electron microscopy

An immune electron microscopy technique has been employed to detect IgE plasma cells in histologically normal human jejunal biopsies. Anti-IgE-labelled plasma cells have been found in the lamina propria of three out of eight biopsies studied. Thus this report ends speculation regarding the presence of IgE plasma cells in human jejunum and supports other data indicating local IgE production in mucosal tissues.

The distribution of human coronavirus strain 229E on the surface of human diploid cells

The distribution of human coronavirus strain 229E (HCV 229E) particles on the surface of human diploid (MRCc) cells was examined. Virus particles showed a totally random distribution on fixed cells and on cells to which virus had been adsorbed in the cold. A marked redistribution of virus particles was observed on warming virus-cell preparations to 33 degrees C for 20 min, the peripheral areas of the cell becoming relatively devoid of virus particles while the majority of particles were now located some distance from the edge of the cell. Redistribution did not occur in the presence of metabolic inhibitors.

The interaction of influenza virus haemagglutinin with phospholipid vesicles - morphological and immunological studies

HA-lipid spheres or "virosomes' were prepared using neutral or negatively charged, but not positively charged, phospholipids. Virosomes were similar in size and shape to native virus particles although the HA subunites were at least twofold less numerous on the virosomes. The HA subunites were attached by their narrow end to the lipid bilayer, and could be removed by digestion with bromelain. However, HA subunits released from intact virus by digestion with bromelain, which removed the hydrophobic tail of the molecule, could not attach to liposomes. Measurements of HA spikes before (mean length 14.2 +/- 0.9 nm) and after attachment to liposomes (mean length 13.3 +/-0.7 nm) and examination of freeze-fractured virosomes indicated that the HA did not penetrate deeply into the lipid bilayer. Similarly, HA subunits did not penetrate deeply into the lipid of virus particles. NP and M proteins could be attached to liposomes but could not be visualized by electron microscopy. Virosomes were taken up by Vero cells by viropexis with no evidence of fusion. Incorporation of HA or NP on to virosomes resulted in increased immunogenicity compared to free HA subunits or NP respectively. This adjuvant activity was not apparent in simple mixtures of HA liposomes. The antibody induced by HA subunits, virions and virosomes reacted similarly with strain-specific (SS) antigenic determinants of the haemagglutinin.

The effect of pneumatic tourniquets on skeletal muscle physiology

The effect of 3- and 5-hour pneumatic tourniquets on skeletal muscle physiology was investigated. Maximum isometric tension development, contraction and half relaxation times were measured in the muscles lying immediately under and distal to the tourniquet. On release of the tourniquet no consistent difference between control and experimental muscles was observed with respect to contraction and half relaxation times; however, there was a marked reduction in maximum isometric tension development. On the sixth day after release of a 5-hour tourniquet, isometric tension was reduced to 2--20 per cent of the control value in the distal muscle and to 40--60 per cent of the control value in the compressed muscle. Six days after a 3-hour tourniquet the compressed muscle tension was reduced to approximately 80 per cent of the control value whilst in the distal muscle, tension development varied from normal to 64 per cent of the control value. Thus it is shown that the effect on muscle contraction after a 3-hour tourniquet is not immediately reversed by the restoration of the blood supply. A reduction in muscle strength follows which may take a week or more to recover.

Infectivity of human coronavirus strain 229E

The replication of human coronavirus strain 229E was observed by using indirect immunofluorescence in infected monolayers of MRC continuous cells. By 8 h after infection, bright cytoplasmic fluorescence was detected in cells infected with human coronavirus 229E. Discrete foci of infection were observed from 8 to 16 h after infection in cells infected with high dilutions of human coronavirus 229E; each fluorescent focus corresponded to a single virus infection. A fluorescent focus assay is described, using indirect immunofluorescence, which is more sensitive than the established techniques of tube titration and plaque assay. Particle/infectivity ratios for unpurified and purified virus preparations revealed a considerable drop in infectivity on purification.

Mouse hepatitis virus strain 3 infection of C57, A/Sn and A/J strain mice and their macrophages. Brief report

Mouse hepatitis virus strain 3 replicated in C57, A/Sn and A/J strain mouse macrophages with the production of a clear cytopathic effect, although only C57 and A/Sn strains of mice were killed with similar MHV3 dilutions. We could not confirm a previous report showing that in vitro cultured macrophages from A/J strain mice were resistant to MHV3 infection.

The effect of pneumatic tourniquets on the ultrastructure of skeletal muscle

Experiments have been carried out on rhesus monkeys to determine the effect of the application of a pneumatic tourniquet on the ultrastructure of the muscles of the lower limb. Tourniquets were applied for periods lasting between one and five hours. The changes in the muscle lying immediately under the cuff of the tourniquet were more marked than those observed in muscle distal to the cuff. Three hours appears to be close to the limit of the time that a muscle can resist the sustained compression of a tourniquet.

Studies on the mechanism of influenza virus entry into cells

Inhibitors of glycolysis, oxidative phosphorylation, protein synthesis, membrane Na&-K& transport and microfilament and microtubule function have been employed to elucidate the mechanism of influenza virus uptake by CAM and CEF cells. Electron microscopy demonstrated uptake of virus by viropexis in the presence of all these inhibitors. Utilizing a pulse labelling technique, virus entering CEF cells in the presence of inhibitors was shown to initiate specific virus polypeptide synthesis after neutralization of remaining extracellular virus and removal of the inhibitors. As a consequence of these findings an energy independent mechanism of viropexis has been proposed.

Mechanism of myofibril growth and proliferation in fish muscle

The mechanisms of myofibril growth proliferation were investigated in the red and white muscles of fish. In both types of muscle the ratio of lattice filament spacings between the Z disk and M line was found to be greater than that required for perfect transformation of a square into a hexagonal lattice. This mismatch was considered to result in the thin filaments being pulled obliquely instead of at right angles to the Z disk. The angle of pull of the thin filaments was measured in longitudinal sections. The splitting process was found to decrease the degree of pull. Splitting was also observed in transverse sections of the peripheral myofibrils. In both red and white fibres these myofibrils were found to commence splitting when they reached a size of approximately 1–2 mum diameter. Evidence from ultrastructural and autoradiographical studies suggested that growth of the myofibrils within the fibres is centrifugal. The outermost myofibrils appear to be the ones which are being built up and which split. The data indicated that in fish muscle a considerable number of filaments may be added to the daughter regions whilst splitting of the myofibril is still continuing.

Complement Lesions in Cell Membranes from Joint Effusions of Various Types of Arthritis

Electron microscopy of differentially centrifuged synovial fluid from patients with differing types of arthritis revealed a few membranes bearing complement lesions. This finding occurred equally in patients with seronegative arthritis as well as in patients with rheumatoid arthritis and positive rheumatoid factor. By incubating effusion leukocytes in vitro with effusion fluid, and peripheral leukocytes with syngeneic serum complement, under conditions in which classical complement activation was inhibited, it could be shown that this finding was through activation of the alternative pathway, by means of lysosomal enzymes. It is not clear where, in inflammatory exudates, is the site of action; it may be on the internal membranes of already damaged cells, as no detectable cytotoxic effect could be found by using 86Rb as a marker for specific release in PMN leukocytes. By means of hemolysis of indicator cells, lysosomal enzyme was found to have the net effect of inhibiting the lysis of indicator cells in the presence of complement activated by the alternative pathway.

Electron microscope observations on the entry of avian infectious bronchitis virus into susceptible cells

Infectious bronchitis virus was observed to enter cells of chicken chorioallantoic membrane by viropexis. There was no support for the suggestion that entry took place by fusion of viral and plasma membranes. The results of electron microscopy showed that virus attachment occurred both at 4 degrees and at 37 degrees C. Viropexis was not observed until the preparations were warmed. Similar results were obtained using chicken kidney cells. Quantitative data obtained from a plaque counting system employing chicken kidney cells indicated that attachment was the same at both temperatures and that some virus particles were taken up at 4 degrees C. Virus uptake was triggered by attachment of the virus to the cell membrane and the subsequent process of virus entry visualised by E. M. appeared to proceed without the involvement of lysosomal enzymes. No intracellular virus was located by electron microscopy in warmed preparations when virus was treated with specific antiserum, either before or after adsorption to the cells.

Detection of antibody in virus--antibody complexes by immunoferritin labelling and subsequent negative staining

A technique for the immunoferritin labelling of antibody participating in virus--antibody complexes has been developed. Complexes were labelled by incubation with the immunoferritin reagent and excess reagent removed by polyacrylamide gel electrophoresis. Labelled complexes were then visualised in the electron microscope by negative staining.

The histochemical demonstration of myofibrillar adenosine triphosphatase activity in fish muscle

A technique for the demonstration of myofibrillar adenosine triphosphatase activity (ATPase) used for mammalian muscle has been modified to suit fish muscle. The mammalian method involves selectively inhibiting fiber types by preincubation at either alkaline (pH 10.4) or acid (pH 4.3) pH before incubation for myofibrillar (ATPase) activity. Fish muscle fibers were found to be generally inactivated under these conditions. Preincubation at an acid pH was found to be unsuitable for fish muscle because of the indiscriminate inactivation of the fibers. The effects of preincubating at pH 10.4 and incubating tissue sections for different time periods and at different pH's and temperatures have been investigated. A differential staining of fiber types correlated with biochemical data on myofibrillar ATPase for red and white muscles was obtained by preincubating sections for short periods (1–2 min) at pH 10.4. Under these conditions the intermediately positioned pink fibers were found to stain similarly to the white fibers of high myofibrillar ATPase activity. An investigation has been made of the qualitative distribution of fiber types in the myotomal muscle of live teleost species: coalfish (Gadus virens), grey mullet (Mugil cephalus), crucian carp (Carassius carassius), black mollie (Mollienesia sp), and glassfish (Chanda ranga). The pink fibers were found to be abundant in all the species examined with the exception of the glassfish.