Sec61-mediated transfer of a membrane protein from the endoplasmic reticulum to the proteasome for destruction

The human cytomegalovirus genome encodes proteins that trigger destruction of newly synthesized major histocompatibility complex (MHC) class I molecules. The human cytomegalovirus gene US2 specifies a product capable of dislocating MHC class I molecules from the endoplasmic reticulum to the cytosol and delivering them to the proteasome. This process involves the Sec61 complex, in what appears to be a reversal of the reaction by which it translocates nascent chains into the endoplasmic reticulum.

The human cytomegalovirus US11 gene product dislocates MHC class I heavy chains from the endoplasmic reticulum to the cytosol

Human cytomegalovirus (HCMV) down-regulates expression of MHC class I products by selective proteolysis. A single HCMV gene, US11, which encodes an endoplasmic reticulum (ER) resident type-I transmembrane glycoprotein, is sufficient to cause this effect. In US11+cells, MHC class I molecules are core-glycosylated and therefore inserted into the ER. They are degraded with a half-time of less than 1 min. A full length breakdown intermediate that has lost the single N-linked glycan in an N-glycanase-catalyzed reaction transiently accumulates in cells exposed to the protease inhibitors LLnL, Cbz-LLL, and lactacystin, identifying the proteasome as a key protease. Subcellular fractionation experiments show this intermediate to be cytosolic. Thus, US11 dislocates newly synthesized class I molecules from the ER to the cytosol, where they are acted upon by an N-glycanase and the proteasome.

Regenerating functional myocardium: improved performance after skeletal myoblast transplantation

The adult heart lacks reserve cardiocytes and cannot regenerate. Therefore, a large acute myocardial infarction often develops into congestive heart failure. To attempt to prevent this progression, we transplanted skeletal myoblasts into cryoinfarcted myocardium of the same rabbits (autologous transfer), monitored cardiac function in vivo for two to six weeks and examined serial sections of the hearts by light and electron microscopy. Islands of different sizes comprising elongated, striated cells that retained characteristics of both skeletal and cardiac cells were found in the cryoinfarct. In rabbits in which myoblasts were incorporated, myocardial performance was improved. The ability to regenerate functioning muscle after autologous myoblast transplantation could have a important effect on patients after acute myocardial infarction.

Induction of antigen-specific cytotoxic T lymphocytes in humans by a malaria DNA vaccine

CD8+ cytotoxic T lymphocytes (CTLs) are critical for protection against intracellular pathogens but often have been difficult to induce by subunit vaccines in animals. DNA vaccines elicit protective CD8+ T cell responses. Malaria-naïve volunteers who were vaccinated with plasmid DNA encoding a malaria protein developed antigen-specific, genetically restricted, CD8+ T cell-dependent CTLs. Responses were directed against all 10 peptides tested and were restricted by six human lymphocyte antigen (HLA) class I alleles. This first demonstration in healthy naïve humans of the induction of CD8+ CTLs by DNA vaccines, including CTLs that were restricted by multiple HLA alleles in the same individual, provides a foundation for further human testing of this potentially revolutionary vaccine technology.

The ER-luminal domain of the HCMV glycoprotein US6 inhibits peptide translocation by TAP

Human cytomegalovirus (HCMV) inhibits MHC class I antigen presentation by a sequential multistep process involving a family of unique short (US) region-encoded glycoproteins. US3 retains class I molecules, whereas US2 and US11 mediate the cytosolic degradation of heavy chains by the proteosomes. In US6-transfected cells, however, intracellular transport of class I molecules is impaired because of defective peptide translocation by transporters associated with antigen processing (TAP). Peptide transport is restored in HCMV mutants lacking US6. In contrast to the cytosolic herpes simplex virus protein ICP47, US6 interacts with TAP inside the endoplasmic reticulum lumen, as shown by US6 derivatives lacking the transmembrane and cytoplasmic domains and by the observation that US6 does not prevent peptides from binding to TAP. Thus, HCMV targets TAP for immune escape by a molecular mechanism different from that of herpes simplex virus.

Human cytomegalovirus US3 impairs transport and maturation of major histocompatibility complex class I heavy chains

The human cytomegalovirus (HCMV) early glycoprotein products of the US11 and US2 open reading frames cause increased turnover of major histocompatibility complex (MHC) class I heavy chains. Since US2 is homologous to another HCMV gene (US3), we hypothesized that the US3 gene product also may affect MHC class I expression. In cells constitutively expressing the HCMV US3 gene, MHC class I heavy chains formed a stable complex with beta 2-microglobulin. However, maturation of the N-linked glycan of MHC class I heavy chains was impaired in US3+ cells. The glycoprotein product of US3 (gpUS3) occurs mostly in a high-mannose form and coimmunoprecipitates with beta 2-microglobulin associated class I heavy chains. Mature class I molecules were detected at steady state on the surface of US3+ cells, as in control cells. Substantial perinuclear accumulation of heavy chains was observed in US3+ cells. The data suggest that gpUS3 impairs egress of MHC class I heavy chains from the endoplasmic reticulum.

Chemokine sequestration by viral chemoreceptors as a novel viral escape strategy: withdrawal of chemokines from the environment of cytomegalovirus-infected cells

Human cytomegalovirus (HCMV), a betaherpesvirus, has developed several ways to evade the immune system, notably downregulation of cell surface expression of major histocompatibility complex class I heavy chains. Here we report that HCMV has devised another means to compromise immune surveillance mechanisms. Extracellular accumulation of both constitutively produced monocyte chemoattractant protein (MCP)-1 and tumor necrosis factor-superinduced RANTES (regulated on activation, normal T cell expressed and secreted) was downregulated in HCMV-infected fibroblasts in the absence of transcriptional repression or the expression of polyadenylated RNA for the cellular chemokine receptors CCR-1, CCR-3, and CCR-5. Competitive binding experiments demonstrated that HCMV-infected cells bind RANTES, MCP-1, macrophage inflammatory protein (MIP)-1beta, and MCP-3, but not MCP-2, to the same receptor as does MIP-1alpha, which is not expressed in uninfected cells. HCMV encodes three proteins with homology to CC chemokine receptors: US27, US28, and UL33. Cells infected with HCMV mutants deleted of US28, or both US27 and US28 genes, failed to downregulate extracellular accumulation of either RANTES or MCP-1. In contrast, cells infected with a mutant deleted of US27 continues to bind and downregulate those chemokines. Depletion of chemokines from the culture medium was at least partially due to continuous internalization of extracellular chemokine, since exogenously added, biotinylated RANTES accumulated in HCMV-infected cells. Thus, HCMV can modify the chemokine environment of infected cells through intense sequestering of CC chemokines, mediated principally by expression of the US28-encoded chemokine receptor.

Multiple independent loci within the human cytomegalovirus unique short region down-regulate expression of major histocompatibility complex class I heavy chains

Reduction of major histocompatibility complex class I cell surface expression occurs in adenovirus-, herpes simplex virus-, human cytomegalovirus (HCMV)-, and murine cytomegalovirus-infected cell systems. Recently, it was demonstrated that the down-regulation mediated by HCMV infection is posttranslational, as a result of increased turnover of class I heavy chains in the endoplasmic reticulum (M. F. C. Beersma, M. J. E. Bijlmakers, and H. L. Ploegh, J. Immunol. 151:4455-4464, 1993; Y. Yamashita, K. Shimokata, S. Saga, S. Mizuno, T. Tsurumi, and Y. Nishiyama, J. Virol. 68:7933-7943, 1994. To identify HCMV genes involved in class I regulation, we screened our bank of HCMV deletion mutants for this phenotype. A mutant with a 9-kb deletion in the S component of the HCMV genome (including open reading frames IRS1 to US9 and US11) failed to down-regulate class I heavy chains. By examining the effects of smaller deletions within this portion of the HCMV genome, a 7-kb region containing at least nine open reading frames was shown to contain the genes required for reduction in heavy-chain expression. Furthermore, it was determined that at least two independent loci within the 7-kb region were able to cause class I heavy-chain down-regulation. One of these, US11, encodes a 32-kDa glycoprotein which causes down-regulation of class I heavy chains in the absence of other viral gene products. Hence, a specific function associated with a phenotype of the HCMV replicative cycle has been mapped to a dispensable gene region. These loci may be important for evasion of the host's immune response and viral persistence.

Pharmacology of L-660,711 (MK-571): a novel potent and selective leukotriene D4 receptor antagonist

L-660,711 (3-(3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl) ((3-dimethyl amino-3-oxo propyl)thio)methyl)thio)propanoic acid is a potent and selective competitive inhibitor of [3H]leukotriene D4 binding in guinea pig (Ki value, 0.22 nM) and human (Ki value, 2.1 nM) lung membranes but is essentially inactive versus [3H]leukotriene C4 binding (IC50 value in guinea pig lung, 23 microM). Functionally it competitively antagonized contractions of guinea pig trachea and ileum induced by leukotriene (LT) D4 (respective pA2 values, 9.4 and 10.5) and LTE4 (respective pA2 values, 9.1 and 10.4) and contractions of human trachea induced by LTD4 (pA2 value, 8.5). L-660,711 (5.8 x 10(-8)M) antagonized contractions of guinea pig trachea induced by LTC4 in the absence (dose ratio = 28) but not in the presence of 45 mM L-serine borate (dose ratio less than 2). L-660,711 (1.9 x 10(-5)M) did not block contractions of guinea pig trachea induced by histamine, acetylcholine, 5-hydroxytryptamine, PGF2 alpha, U-44069, or PGD2. In the presence of atropine, mepyramine, and indomethacin, L-660,711 (1.9 x 10(-5)M) inhibited a small component of the response to antigen on guinea pig trachea but completely blocked anti-IgE-induced contractions of human trachea. L-660,711 (i.v.) antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. LTC4, LTD4, and LTE4 but did not block bronchoconstriction to arachidonic acid, U-44069, 5-hydroxytryptamine, histamine, or acetylcholine. Intraduodenal L-660,711 antagonized LTD4 (0.2-12.8 micrograms/kg)-induced bronchoconstriction in guinea pigs, and p.o. L-660,711 blocked LTD4- and Ascaris-induced bronchoconstriction in conscious squirrel monkeys and ovalbumin-induced bronchoconstriction in conscious sensitized rats treated with methysergide (3 micrograms/kg). The pharmacological profile of L-660,711 indicates that it is a potent, selective, orally active leukotriene receptor antagonist which is well suited to determine the role played by LTD4 and LTE4 in asthma and other pathophysiologic conditions.

Expression of the cysteinyl leukotriene 1 receptor in normal human lung and peripheral blood leukocytes

The cysteinyl leukotrienes (CysLTs) are important mediators of human asthma. Pharmacologic and clinical studies show that the CysLTs exert most of their bronchoconstrictive and proinflammatory effects through activation of a putative, 7-transmembrane domain, G-protein-coupled receptor, the CysLT1 receptor. The initial molecular characterization of the CysLT1 receptor showed by in situ hybridization, the presence of CysLT1 receptor messenger RNA (mRNA) in human lung smooth-muscle cells and lung macrophages. We confirmed the results of these in situ hybridization analyses for the CysLT1 receptor, and produced the first immunohistochemical characterization of the CysLT1 receptor protein in human lung. The identification of the CysLT1 receptor in the lung is consistent with the antibronchoconstrictive and antiinflammatory actions of CysLT1 receptor antagonists. We also report the expression of CysLT1 receptor mRNA and protein in most peripheral blood eosinophils and pregranulocytic CD34+ cells, and in subsets of monocytes and B lymphocytes.

Steady-state free precession magnetic resonance imaging of the heart: comparison with segmented k-space gradient-echo imaging

Steady-state free precession imaging is a promising technique for cardiac magnetic resonance imaging (MRI), as it provides improved blood/myocardial contrast in shorter acquisition times compared with conventional gradient-echo acquisition. The better contrast could improve observer agreement and automatic detection of cardiac contours for volumetric assessment of the ventricles, but measurements might differ from those obtained using conventional methods. We compared volumetric measurements, observer variabilities, and automatic contour detection between a steady-state free precession imaging sequence (BFFE = balanced fast field echo) and segmented k-space gradient-echo acquisition (TFE = turbo field echo) in 41 subjects. With BFFE, significantly higher end-diastolic and end-systolic volumes and lower wall thickness, ventricular mass, ejection fraction, and wall motion were observed (P < 0.0001), while interobserver variabilities were lower and automatic contour detection of endocardial contours was more successful. We conclude that the improved image quality of BFFE reduces the observer-dependence of volumetric measurements of the left ventricle (LV) but results in significantly different values in comparison to TFE measurements.

Pharmacology of montelukast sodium (Singulair), a potent and selective leukotriene D4 receptor antagonist

Montelukast sodium (Singulair), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-(1- hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [3H]leukotriene D4 specific binding in guinea pig lung (Ki 0.18 +/- 0.03 nM), sheep lung (Ki 4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (Ki 0.52 +/- 0.23 nM), but it was essentially inactive versus [3H]leukotriene C4 specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC50 10 microM) and [3H]leukotriene B4 specific binding in THP-1 cell membranes (IC50 40 microM). Montelukast also inhibited specific binding of [3H]leukotriene D4 to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with Ki values of 0.21 +/- 0.08, 0.19 +/- 0.02, and 0.26 +/- 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D4 (pA2 value 9.3; slope 0.8). In contrast, montelukast (16 microM) failed to antagonize contractions of guinea pig trachea induced by leukotriene C4 (45 mM serine-borate), serotonin, acetylcholine, histamine, prostaglandin D2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D4 but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D4 induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED50 0.03 +/- 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03-0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 micrograms.kg-1.min-1) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene D4 receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.

Cytomegalovirus US2 destroys two components of the MHC class II pathway, preventing recognition by CD4+ T cells

Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus that causes life-threatening disease in patients who are immunosuppressed for bone marrow or tissue transplantation or who have AIDS (ref. 1). HCMV establishes lifelong latent infections and, after periodic reactivation from latency, uses a panel of immune evasion proteins to survive and replicate in the face of robust, fully primed host immunity. Monocyte/macrophages are important host cells for HCMV, serving as a latent reservoir and as a means of dissemination throughout the body. Macrophages and other HCMV-permissive cells, such as endothelial and glial cells, can express MHC class II proteins and present antigens to CD4+ T lymphocytes. Here, we show that the HCMV protein US2 causes degradation of two essential proteins in the MHC class II antigen presentation pathway: HLA-DR-alpha and DM-alpha. This was unexpected, as US2 has been shown to cause degradation of MHC class I (refs. 5,6), which has only limited homology with class II proteins. Expression of US2 in cells reduced or abolished their ability to present antigen to CD4+ T lymphocytes. Thus, US2 may allow HCMV-infected macrophages to remain relatively 'invisible' to CD4+ T cells, a property that would be important after virus reactivation.

Induction of CD4(+) T cell-dependent CD8(+) type 1 responses in humans by a malaria DNA vaccine

We assessed immunogenicity of a malaria DNA vaccine administered by needle i.m. or needleless jet injection [i.m. or i.m./intradermally (i.d.)] in 14 volunteers. Antigen-specific IFN-gamma responses were detected by enzyme-linked immunospot (ELISPOT) assays in all subjects to multiple 9- to 23-aa peptides containing class I and/or class II restricted epitopes, and were dependent on both CD8(+) and CD4(+) T cells. Overall, frequency of response was significantly greater after i.m. jet injection. CD8(+)-dependent cytotoxic T lymphocytes (CTL) were detected in 8/14 volunteers. Demonstration in humans of elicitation of the class I restricted IFN-gamma responses we believe necessary for protection against the liver stage of malaria parasites brings us closer to an effective malaria vaccine.

Boosting with recombinant vaccinia increases immunogenicity and protective efficacy of malaria DNA vaccine

To enhance the efficacy of DNA malaria vaccines, we evaluated the effect on protection of immunizing with various combinations of DNA, recombinant vaccinia virus, and a synthetic peptide. Immunization of BALB/c mice with a plasmid expressing Plasmodium yoelii (Py) circumsporozoite protein (CSP) induces H-2Kd-restricted CD8+ cytotoxic T lymphocyte (CTL) responses and CD8+ T cell- and interferon (IFN)-gamma-dependent protection of mice against challenge with Py sporozoites. Immunization with a multiple antigenic peptide, including the only reported H-2Kd-restricted CD8+ T cell epitope on the PyCSP (PyCSP CTL multiple antigenic peptide) and immunization with recombinant vaccinia expressing the PyCSP induced CTL but only modest to minimal protection. Mice were immunized with PyCSP DNA, PyCSP CTL multiple antigenic peptide, or recombinant vaccinia expressing PyCSP, were boosted 9 wk later with the same immunogen or one of the others, and were challenged. Only mice immunized with DNA and boosted with vaccinia PyCSP (D-V) (11/16: 69%) or DNA (D-D) (7/16: 44%) had greater protection (P < 0. 0007) than controls. D-V mice had significantly higher individual levels of antibodies and class I-restricted CTL activity than did D-D mice; IFN-gamma production by ELIspot also was higher in D-V than in D-D mice. In a second experiment, three different groups of D-V mice each had higher levels of protection than did D-D mice, and IFN-gamma production was significantly greater in D-V than in D-D mice. The observation that priming with PyCSP DNA and boosting with vaccinia-PyCSP is more immunogenic and protective than immunizing with PyCSP DNA alone supports consideration of a similar sequential immunization approach in humans.

Rapid cytoplasmic turnover of c-myc mRNA: requirement of the 3' untranslated sequences

Expression of the c-myc gene can be controlled by transcriptional or posttranscriptional mechanisms (or both), depending on the cell type and the growth conditions. An important mechanism of posttranscriptional regulation is modulation of cytoplasmic c-myc mRNA stability; normal human and murine c-myc mRNAs have cytoplasmic half-lives of 30 min or less. To elucidate the c-myc sequences which impart this unusually high rate of cytoplasmic transcript turnover, we have constructed various deletion and hybrid c-myc genes and analyzed the cytoplasmic stability of the mRNAs produced from them in stably transfected murine fibroblasts. The results indicate that sequences contained within the 5' and 3' ends of the c-myc transcript can affect cytoplasmic stability. Specifically, the 3' untranslated sequences of c-myc exon 3 are required for, but do not ensure, a high rate of transcript turnover in the cytoplasm. Exon 2 coding sequences do not seem to be involved, and exon 1 sequences at the 5' end of the transcript have only a small effect on cytoplasmic transcript stability. The sequences that are primarily responsible for the short c-myc RNA half-life were localized to a region of 140 bases in the 3' untranslated region.

Age-dependent acquired protection against Plasmodium falciparum in people having two years exposure to hyperendemic malaria

An epidemiologic study of susceptibility to frequent and high-grade parasitemia by Plasmodium falciparum revealed that age-dependent acquired protection developed within a two-year period of exposure to hyperendemic infection pressure. The study was conducted in a single village in northeastern Irian Jaya, Indonesia, where half the residents were native to the province and the other half were transmigrants from areas of Java, where there is little or no malaria transmission. Five separate measures of susceptibility to the asexual parasitemia of falciparum malaria were derived from results of four months of biweekly surveillance of 240 volunteers. Increasing protection as a function of age among the Javanese was a consistent pattern among the five estimates of susceptibility. These age-dependent functions of protection were quantitatively parallel to those among life-long residents of Irian Jaya. When humoral immune responsiveness to ring-infected erythrocyte surface antigen (RESA) was measured by ELISA, a similar pattern emerged; the relative level of antibody to RESA increased as parallel functions of age among the two subpopulations. Acquired protective immunity against P. falciparum was not the cumulative product of many years of heavy exposure to antigen. Instead, the full benefit of protection appeared to develop quickly. The degree of protection was governed by recent exposure and age, independent of history of chronic heavy exposure.

Pharmacological study of the contractile activity of leukotriene C4 and D4 on isolated human airway smooth muscle

Synthetic leukotriene C4(LTC4) and leukotriene D4(LTD4) were examined on isolated human tracheal and bronchial smooth muscle. Both LTC4 and LTD4 produced slowly developing contraction of trachealis and bronchus which were submaximal (70-85% of the carbachol maximum) and were not blocked by 1.0 microM atropine, 5.0 microM mepyramine, or 5.6 microM indomethacin. The EC50's for LTC4 and LTD4 were 10.3 and 1.8 nM on trachealis and 1.8 and 1.7 nM on bronchus, respectively. LTD4 was in excess of 20 000 times more potent than acetylcholine on some bronchial and tracheal tissues. Similar differences in potency were obtained in some tissues when LTC4 and LTD4 were compared with histamine. Tissues pretreated for 30 min with 2.0-4.0 microM FPL-55712 were less reactive to LTC4 and LTD4 than untreated control tissues. Established contractions to LTC4 and LTD4 persisted despite washing with fresh Krebs solution, were partially reversed by FPL-55712 (0.5-10 microM) and the Ca2+ channel blocker D-600 (5-10 microM), but were completely reversed by the catecholamine adrenaline (1.0 microM) and by high concentrations of FPL-55712 (greater than 20 microM). The marked potency of the leukotrienes on human tracheal and bronchial smooth muscle suggests an important role for these lipoxygenase products in respiratory disease.

Control of human airway smooth muscle: in vitro studies

An in vitro study of neural and myogenic control of human tracheal smooth muscle was undertaken. Over 80% of these had active tension and 13% had phasic contractile activity. Tonic and phasic activities were not reversed by indomethacin, 5,8,11,14-eicosatetraynoic acid, methysergide, mepyramine, atropine, or tetrodotoxin (TTX) but were blocked by the calcium antagonist verapamil. In some quiescent strips, tonic and/or phasic activity was induced by exposure to potassium-conductance blockers such as 4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA). Electrical (field) stimulation resulted in frequency-dependent biphasic responses: an initial atropine-sensitive cholinergic contraction followed by a nonadrenergic relaxation. This biphasic response to low stimulus parameters (less than 0.5 ms, less than 15 Hz) was blocked by TTX and scorpion venom and enhanced by 4-AP and TEA, consistent with a neural mechanism. Relaxation responses to longer pulse durations (0.5-1 ms) were not blocked by TTX despite abolition of contraction nor were they enhanced by 4-AP and TEA, suggesting a nonneural mechanism. ATP, adenosine, arachidonate metabolites, histamine, 5-hydroxytryptamine, neurotensin, or vasoactive intestinal polypeptide were ruled out as possible nonadrenergic mediators. The nature and physiological significance of the nonneural inhibitory response remains unknown.

Human cytomegalovirus US2 destabilizes major histocompatibility complex class I heavy chains

Human cytomegalovirus (HCMV) infection causes down-regulation of major histocompatibility complex class I heavy chains. We determined previously that there are two HCMV loci which encode functions responsible for that phenotype and that US11 is one of these loci (T. R. Jones, L. A. Hanson, L. Sun, J. S. Slater, R. M. Stenberg, and A. E. Campbell, J. Virol. 69:4830-4841, 1995). Through the construction and analysis of defined viral mutants and stably transfected cell lines, we identify US2 as the other locus. US2 is expressed from very early through late times postinfection, with its predominant product being a relatively unstable 24-kDa endoglycosidase H-resistant glycoprotein. In cell lines constitutively expressing US2, free class I heavy chains are proximal targets for US2-induced degradation, shortly after their synthesis. Both US2 and US11 can function in concert with US3 to down-regulate class I. Beta-2-microglobulin-associated heavy chains which are retained in the endoplasmic reticulum as a result of binding to the US3 glycoprotein are susceptible to destabilization caused by both US2 and US11 gene products. Thus, three HCMV genes which affect either the stability or the transport of class I heavy chains have been identified. The observation that each of these proteins is most abundant early in the replicative cycle suggests that they may play an important immunomodulatory role in vivo prior to productive infection, either during the latent or persistent phase or during reactivation.

Synthetic oligodeoxynucleotides containing CpG motifs enhance immunogenicity of a peptide malaria vaccine in Aotus monkeys

Synthetic peptide and recombinant protein vaccines are optimally immunogenic when delivered with an effective adjuvant. Candidate vaccines currently insufficiently immunogenic may induce a protective immunity if they could be delivered with more effective adjuvants. For example, immunogens that induce promising responses when administered to mice with complete and incomplete Freund's adjuvants perform less well in primate animal models where complete Freund's adjuvant is not used. We report the use of synthetic oligodeoxynucleotides containing CpG motifs, the sequences of which are based on immunostimulatory bacterial DNA sequences, to enhance the immune response in Aotus monkeys to a synthetic peptide malaria vaccine. Monkeys were immunized with the synthetic peptide PADRE 45, a synthetic peptide containing amino acid sequences derived from the circumsporozoite protein (CSP) from Plasmodium falciparum, and delivered in an emulsion of saline and Montanide 720, a mannide oleate in oil solution, that also contained one of three oligodeoxynucleotides. The animals receiving oligodeoxynucleotides containing either three or four CpG motifs produced antibodies that bound a recombinant CSP as measured in ELISA, and reacted with P. falciparum sporozoites in a sporozoite immunofluorescent test. These responses were significantly greater than those seen in animals receiving the oligodeoxynucleotide without CpG motifs. These data indicate that oligodeoxynucleotides containing CpG motifs improve immunogenicity of peptide immunogens in non-human primates, and may be immunopotentiators useful in humans.

Dislocation of type I membrane proteins from the ER to the cytosol is sensitive to changes in redox potential

The human cytomegalovirus (HCMV) gene products US2 and US11 dislocate major histocompatibility class I heavy chains from the ER and target them for proteasomal degradation in the cytosol. The dislocation reaction is inhibited by agents that affect intracellular redox potential and/or free thiol status, such as diamide and N-ethylmaleimide. Subcellular fractionation experiments indicate that this inhibition occurs at the stage of discharge from the ER into the cytosol. The T cell receptor alpha (TCR alpha) chain is also degraded by a similar set of reactions, yet in a manner independent of virally encoded gene products. Diamide and N-ethylmaleimide likewise inhibit the dislocation of the full-length TCR alpha chain from the ER, as well as a truncated, mutant version of TCR alpha chain that lacks cysteine residues. Cytosolic destruction of glycosylated, ER-resident type I membrane proteins, therefore, requires maintenance of a proper redox potential for the initial step of removal of the substrate from the ER environment.

Malaria prophylaxis using azithromycin: a double-blind, placebo-controlled trial in Irian Jaya, Indonesia

New drugs are needed for preventing drug-resistant Plasmodium falciparum malaria. The prophylactic efficacy of azithromycin against P. falciparum in malaria-immune Kenyans was 83%. We conducted a double-blind, placebo-controlled trial to determine the prophylactic efficacy of azithromycin against multidrug-resistant P. falciparum malaria and chloroquine-resistant Plasmodium vivax malaria in Indonesian adults with limited immunity. After radical cure therapy, 300 randomized subjects received azithromycin (148 subjects, 750-mg loading dose followed by 250 mg/d), placebo (77), or doxycycline (75, 100 mg/d). The end point was slide-proven parasitemia. There were 58 P. falciparum and 29 P. vivax prophylaxis failures over 20 weeks. Using incidence rates, the protective efficacy of azithromycin relative to placebo was 71.6% (95% confidence interval [CI], 50.3-83.8) against P. falciparum malaria and 98.9% (95% CI, 93.1-99.9) against P. vivax malaria. Corresponding figures for doxycycline were 96.3% (95% CI, 85.4-99.6) and 98% (95% CI, 88.0-99.9), respectively. Daily azithromycin offered excellent protection against P. vivax malaria but modest protection against P. falciparum malaria.