The genome sequence of herpes simplex virus type 2

The genomic DNA sequence of herpes simplex virus type 2 (HSV-2) strain HG52 was determined as 154,746 bp with a G+C content of 70.4%. A total of 74 genes encoding distinct proteins was identified; three of these were each present in two copies, within major repeat elements of the genome. The HSV-2 gene set corresponds closely with that of HSV-1, and the HSV-2 sequence prompted several local revisions to the published HSV-1 sequence (D. J. McGeoch, M. A. Dalrymple, A. J. Davison, A. Dolan, M. C. Frame, D. McNab, L. J. Perry, J. E. Scott, and P. Taylor, J. Gen. Virol. 69:1531-1574, 1988). No compelling evidence for the existence of any additional protein-coding genes in HSV-2 was identified.

A novel compound that elevates high density lipoprotein and activates the peroxisome proliferator activated receptor

In the current studies we describe the effects of PD 72953 and related compounds on lipoprotein levels in chow-fed male rats. After 2 weeks, 10 mg/kg of PD 72953 daily was as effective as 100 mg/kg gemfibrozil for elevating HDL-cholesterol. At 100 mg/kg, PD 72953 further elevated HDL-cholesterol to 232% of control levels, and was associated with increased HDL size and plasma apoE (169% of control), despite no change in hepatic apoE mRNA. ApoA-I rose transiently (at 1 week), but by 2 weeks only apoE remained elevated. PD 72953 dose-dependently reduced plasma apoB, VLDL-cholesterol, LDL-cholesterol, and triglyceride. Hepatic apoC-III mRNA reduction parallelled triglyceride lowering. After 1 week, 30 and 100 mg/kg per day PD 72953 reduced plasma apo-CIII levels by 30 and 34%, and triglycerides by 60 and 83%, respectively. PD 72953 treatment had no effect on triglyceride production rates; however, 125I-labeled VLDL apoB disappearance was enhanced. We compared PD 72953 to a structurally similar diacid, PD 69405, that also reduced VLDL and LDL, but had no effect on HDL elevation. Compared to PD 72953, PD 69405 further accelerated 125I-labeled VLDL apoB disappearance, decreased triglyceride production, and elevated the ratio of post-heparin hepatic to lipoprotein lipase activity. Whole animal studies, transient transfection studies in HepG2 cells, and chimeric receptor studies in kidney 293 cells suggest that PD 72953 is a ligand for the peroxisomal proliferation activated receptor alpha (PPARalpha), and PPARgamma. Overall, PD 72953 may act through a peroxisomal proliferation activated receptor and result in plasma triglycerides and apoB-containing lipoprotein reduction, while also raising HDL cholesterol. Reduced apoC-III may allow triglyceride-rich remnants to more efficiently bind and present substrate to peripheral tissue lipoprotein lipase, and therefore allow enhanced shedding of remnant phospholipid surface for HDL production.

The active site of ICP47, a herpes simplex virus-encoded inhibitor of the major histocompatibility complex (MHC)-encoded peptide transporter associated with antigen processing (TAP), maps to the NH2-terminal 35 residues

The herpes simplex virus (HSV) immediate early protein ICP47 inhibits the transporter associated with antigen processing (TAP)-dependent peptide translocation. As a consequence, empty major histocompatibility complex (MHC) class I molecules are retained in the endoplasmic reticulum and recognition of HSV-infected cells by cytotoxic T lymphocytes is abolished. We chemically synthesized full-length ICP47 (sICP47) and show that sICP47 inhibits TAP-dependent peptide translocation in human cells. Its biological activity is indistinguishable from that of recombinant ICP47 (rICP47). By using synthetic peptides, we mapped the core sequence of ICP47 minimally required for TAP inhibition to residues 2-35. This segment is located within the region of the molecule conserved between ICP47 from HSV-1 and HSV-2. Through alanine scanning substitution we identified three segments within this region that are critical for the ability to inhibit TAP function. The interaction of ICP47 with TAP is unlikely to mimic precisely that of the transported peptides, as deduced from differential labeling of the TAP1 and TAP2 subunits using sICP47 fragments with chemical cross-linkers.

Opposite effects of bezafibrate and gemfibrozil in both normal and hypertriglyceridemic rats

Chow and sucrose-fed rats were used as animal models to study the dose-responses of bezafibrate and gemfibrozil in normolipidemic and hypertriglyceridemic states, respectively. Although both drugs lowered plasma triglycerides (TG) to about the same extent in chow-fed rats, gemfibrozil lowered liver TG as well as plasma total and LDL-cholesterol (LDL-C), but elevated HDL-cholesterol (HDL-C) and plasma apo E concentrations. Bezafibrate produced opposite effects, namely, decreased HDL-C, apo E and liver TG, and tended to increase LDL-C. TG lowering for both drugs in chow-fed rats was not due to changes in TG secretion (production) in normal rats but was associated with enhanced LPL activity. In hypertriglyceridemic rats both drugs modestly reduced TG secretion rates about 40% at a dose producing maximal TG lowering, but again, gemfibrozil elevated and bezafibrate lowered HDL-C and apo E. Unlike gemfibrozil, bezafibrate induced the appearance of LDL-C in hypertriglyceridemic rats which was not detected in control animals, and also tended to increase rather than decrease plasma apo B levels. Finally, changes in liver TG concentration (mg/g) in hypertriglyceridemic rats were opposite for these drugs, resulting in significant drug-related differences in liver TG content (mg/organ). From these data we postulate that, although similar with regard to TG lowering activity and mechanisms thereof, gemfibrozil and bezafibrate produce fundamentally different effects on LDL, HDL and apolipoprotein metabolism (apo B and apo E) in rats which may relate to potential differential effects on reverse cholesterol transport and atherogenesis.

Experimental cascaded operation of low-birefringence nonlinear-optical loop mirrors

We experimentally demonstrate the operation of a low-birefringence (low-bi) nonlinear-optical loop mirror (NOLM) that has the advantages of low switching energy, tolerance to timing jitter, and cascadability. Because cascading two all-optical logic gates is an important step toward high-speed optical signal processing and header processing in time-division-multiplexed networks, we also demonstrate the cascaded operation of two low-bi NOLM's. Using a passively mode-locked fiber laser that produces 450-fs pulses at a wavelength of 1.55 microm, we achieve a 10.7:1 switching contrast ratio and a 2.7-pulse-widths-wide timing window after the cascaded gates. The results agree well with theoretical predictions and confirm the advantages of the long interaction length associated with orthogonally polarized pulses in low-bi (Deltan ~ 3.0 x 10(-6)) polarization-maintaining fiber.

Synchronization of two passively mode-locked erbium-doped fiber lasers by an acousto-optic modulator and grating scheme

We synchronize two passively mode-locked erbium-doped fiber lasers by adjusting only the cavity length to correct both the repetition rate and the phase. The interlaser jitter is less than 6 ps (1.3 times the pulse width) and is extracted from the cross correlation of the two lasers. The lock can be maintained for extended periods of time. These results are obtained by use of a novel acousto-optic-modulator-grating scheme, which provides an equivalent of 300 microm in cavity length tuning with a bandwidth of 10 kHz. These parameters are 30 times the length and 10 times the bandwidth of a typical piezoelectric transducer.

Hypolipidemic activity of select fibrates correlates to changes in hepatic apolipoprotein C-III expression: a potential physiologic basis for their mode of action

For the last 30 years fibrates have been widely prescribed to treat human dyslipidemia. However, the primary mechanism by which they lower plasma lipid levels is still unknown. Studies with transgenic mice have suggested that changes in apoC-III expression levels have a dramatic influence on plasma triglyceride levels. These results suggested that fibrates could reduce lipid levels by lowering apoC-III gene expression. In the current studies, we sought to determine whether the selected fibrates, bezafibrate, clofibrate, fenofibrate, and gemfibrozil, could reduce hepatic apoC-III mRNA and plasma apoC-III levels. Chow-fed rats were orally gavaged daily with a dosing vehicle alone or with 100 mg/kg of each of the fibrates for 1 week and in addition with gemfibrozil for 2 weeks. Bezafibrate and fenofibrate lowered plasma triglyceride by approximately half and dramatically reduced hepatic apoC-III mRNA and plasma apoC-III levels. In contrast, clofibrate did not reduce plasma triglyceride levels and only partially reduced apoC-III mRNA and plasma protein levels. Gemfibrozil strongly reduced plasma triglyceride levels and had an intermediate but significant effect on apoC-III mRNA and plasma apoC-III levels. Some of the fibrates, especially gemfibrozil also reduced plasma apoC-II levels, an effect that could contribute to the observed triglyceride-lowering effect. In addition, the ratio of plasma apoE to plasma apoC-II plus apoC-III was strongly and inversely correlated with plasma triglyceride levels. As plasma apoE levels were not reduced in gemfibrozil-treated animals, this could also have contributed to the triglyceride-lowering effect of this fibrate. Fibrate-mediated triglyceride lowering was not the result of a decreased apoB or VLDL production and, therefore, suggested an enhanced VLDL remnant catabolism. Our results suggest that the mechanism by which fibrates lower plasma triglycerides is by reducing the level of hepatic apoC-III expression.

High-power erbium-doped fiber laser mode locked by a semiconductor saturable absorber

Using an erbium-doped fiber laser (EDFL) passively mode locked by a semiconductor saturable absorber, we generate 5.5-ps pulses of a 2.3-nJ/pulse, which are more than three times higher in energy than for other reported EDFL's. We show that, by introduction of a linear loss element within the cavity, multiple pulsing behavior at high pump powers can be suppressed. We also determine the saturable-absorber characteristics-absorbance versus wavelength near band gap-that are necessary to produce short mode-locked pulses.

HLA class I molecules are not transported to the cell surface in cells infected with herpes simplex virus types 1 and 2

To assess the effect of herpes simplex virus (HSV) on assembly and transport of class I MHC molecules, we compared class I MHC immunoprecipitated from metabolically labeled infected and uninfected human dermal fibroblasts. The immunoprecipitates were analyzed by isoelectric focusing, allowing identification of individual class I alleles and assessment of transport through the Golgi apparatus by the sialation of carbohydrate residues. In cells infected with wild-type HSV, class I synthesis was reduced or abolished because of the host protein synthesis shutoff function of the UL41 gene product. In cells infected with mutant viruses of both HSV-2 strain G and HSV-1 strain 17 that lack the UL41 gene, class I HLA molecules failed to become sialated, suggesting that they were not transported to the Golgi apparatus. In contrast, transferrin receptor was normally sialated in both infected and uninfected cells. Drug treatments of cells to restrict viral gene expression suggested that an early gene or genes were responsible for the effect. A pulse chase showed that class I molecules were synthesized in normal amounts in infected cells, but that heavy chains were retained in a sialyl transferase negative compartment either stably associated with beta 2m or as free heavy chain in a pattern that is characteristic for each class I allele. HSV is thus the fourth example of a DNA virus that interferes with class I assembly or transport.

HLA class I molecules are not transported to the cell surface in cells infected with herpes simplex virus types 1 and 2

To assess the effect of herpes simplex virus (HSV) on assembly and transport of class I MHC molecules, we compared class I MHC immunoprecipitated from metabolically labeled infected and uninfected human dermal fibroblasts. The immunoprecipitates were analyzed by isoelectric focusing, allowing identification of individual class I alleles and assessment of transport through the Golgi apparatus by the sialation of carbohydrate residues. In cells infected with wild-type HSV, class I synthesis was reduced or abolished because of the host protein synthesis shutoff function of the UL41 gene product. In cells infected with mutant viruses of both HSV-2 strain G and HSV-1 strain 17 that lack the UL41 gene, class I HLA molecules failed to become sialated, suggesting that they were not transported to the Golgi apparatus. In contrast, transferrin receptor was normally sialated in both infected and uninfected cells. Drug treatments of cells to restrict viral gene expression suggested that an early gene or genes were responsible for the effect. A pulse chase showed that class I molecules were synthesized in normal amounts in infected cells, but that heavy chains were retained in a sialyl transferase negative compartment either stably associated with beta 2m or as free heavy chain in a pattern that is characteristic for each class I allele. HSV is thus the fourth example of a DNA virus that interferes with class I assembly or transport.

A novel herpes simplex virus gene (UL49A) encodes a putative membrane protein with counterparts in other herpesviruses

Comparative analysis of DNA sequences located between the coding regions of genes UL49 and UL50 of herpes simplex virus types 1 and 2 (HSV-1 and -2) has revealed a small open reading frame (ORF) of 91 and 87 codons respectively with the characteristics of a genuine protein-coding region. The predicted protein products are clearly related and exhibit features of membrane-inserted proteins, with potential N-proximal signal peptides and C-proximal membrane anchor regions. Counterparts are present in the other sequenced alphaherpesviruses, namely varicella-zoster virus (a previously undescribed gene, 9A) and equine herpesvirus type 1 (gene 10), in the betaherpesvirus human cytomegalovirus (gene UL73) and in the gammaherpesvirus Epstein-Barr virus (gene BLRF1). Therefore, we consider that this ORF represents an additional HSV gene (UL49A) with counterparts in all sequenced alpha-, beta- and gammaherpesviruses.

Structural assignment of novel and immunodominant antigenic sites in the neutralizing antibody response of CBA/Ca mice to influenza hemagglutinin

Information on the antigenic structure of influenza hemagglutinin (HA) has been deduced previously from sequence analyses of laboratory mutant viruses selected, in vitro, with neutralizing monoclonal antibody (mAb) established exclusively from BALB/c (H-2d) mice; and there has been no attempt to investigate the influence of host genetic background, or natural route of infection, on the protective antibody repertoire. CBA/Ca mice are extremely sensitive to X31 virus infection, and in the present study a structural analysis was made of the antibody repertoire, by direct sequencing of the HA genes of laboratory mutant viruses selected, in ovo with mAb from CBA/Ca mice primed by natural infection with X31 virus at two different infectious doses. Single nucleotide substitutions in the HA genes of mutant viruses identified both novel and immunodominant antigenic sites on the HA1 subunit: a majority of mAbs, from different donors, were of the IgG2a isotype and were specific for HA1 158 Gly. In addition, novel laboratory mutants were obtained containing substitutions in the HA1 subunit that had not been reported previously for H3 subtype viruses, either natural variants or laboratory mutants, at residues: HA1 62 Ile----Arg; HA1 165 Asn----Ser (resulting in the loss of a N-glycosylation site); and HA1 273 Pro----Leu. Our findings suggest that host genetic background and/or a natural route of infection may be significant factors in the selection of different and distinct neutralizing antibody responses to influenza HA and therefore be of some relevance in our further understanding of the immune pressure for antigenic drift, and the immunogenic features of a protective antigen.

Single amino acid residues in a synthetic peptide of influenza haemagglutinin, HA 1 177-199, distinguish I-Ad- and I-Ed-restricted T-cell epitopes

A majority of Iad-restricted, CD4+ T-cell clones, derived from BALB/c mice infected with X31 (H3N2) influenza virus and specific for the HA 1 subunit of the viral haemagglutinin (HA), has previously been shown to recognize the synthetic peptide HA 1 177-199, corresponding to the primary amino acid sequence of a major antibody binding site. Here it is demonstrated that both I-Ad- and I-Ed-restricted T-cell clones recognize HA 1 177-199, and that inter- and intra-allelic differences in Iad-restricted recognition are defined by single amino acid residues. A panel of truncated HA 1 synthetic peptides defined three distinct but overlapping CD4+ epitopes within the common antigenic site (HA 1 177-199): two I-Ad-restricted epitopes mapped within HA 1 186-198 and HA 1 177-199, and peptide HA 1 178-195 identified an I-Ed-restricted epitope. Moreover, fine specificity differences in the recognition of synthetic peptides, truncated at the carboxy terminus of HA 1 177-199, identified residues HA 1 A 198 and HA 1 S 199 as being critical for defining inter- and intra-allelic differences, respectively, in the Iad-restricted T-cell recognition of HA.

I-Ad restricted T cell recognition of influenza hemagglutinin. Synthetic peptides identify multiple epitopes corresponding to antibody-binding regions of the HA1 subunit

In a recent study, we reported extensive diversity in the Iak-restricted T cell repertoire for the hemagglutinin molecule (HA) of influenza A viruses (H3 subtype). Synthetic peptides identified six nonoverlapping epitopes on the HA1 subunit, and CD4+ T cell clones, specific for these regions, discriminated between natural variant viruses that had accumulated amino acid substitutions during antigenic drift. Here, we demonstrate similar specificity and diversity for the Iad haplotype and have identified multiple T cell epitopes within the sequences HA1 56-76, 71-91, 81-97, 177-199, 186-205, and 206-227. These also include recognition sites for neutralizing antibodies and correlations can be made between antigenic drift substitutions in H3 subtype viruses and the specificity of individual CD4+ clones for mutant HA. Moreover, these peptides appear not to exhibit structural homology and fail to compete for Ag presentation, indicating heterogeneity in peptide-Ia interaction. To explain the observation that CD4+ T cells, from two major haplotypes, recognize antibody binding regions of the HA molecule, we propose that surface Ig receptors of the Ag-specific B memory cell exert a direct effect on the processing of HA peptides and subsequent selection of the class II-restricted T cell memory repertoire after natural infection.

I-Ad restricted T cell recognition of influenza hemagglutinin. Synthetic peptides identify multiple epitopes corresponding to antibody-binding regions of the HA1 subunit

In a recent study, we reported extensive diversity in the Iak-restricted T cell repertoire for the hemagglutinin molecule (HA) of influenza A viruses (H3 subtype). Synthetic peptides identified six nonoverlapping epitopes on the HA1 subunit, and CD4+ T cell clones, specific for these regions, discriminated between natural variant viruses that had accumulated amino acid substitutions during antigenic drift. Here, we demonstrate similar specificity and diversity for the Iad haplotype and have identified multiple T cell epitopes within the sequences HA1 56-76, 71-91, 81-97, 177-199, 186-205, and 206-227. These also include recognition sites for neutralizing antibodies and correlations can be made between antigenic drift substitutions in H3 subtype viruses and the specificity of individual CD4+ clones for mutant HA. Moreover, these peptides appear not to exhibit structural homology and fail to compete for Ag presentation, indicating heterogeneity in peptide-Ia interaction. To explain the observation that CD4+ T cells, from two major haplotypes, recognize antibody binding regions of the HA molecule, we propose that surface Ig receptors of the Ag-specific B memory cell exert a direct effect on the processing of HA peptides and subsequent selection of the class II-restricted T cell memory repertoire after natural infection.

The immune response of BALB/c mice to influenza hemagglutinin: commonality of the B cell and T cell repertoires and their relevance to antigenic drift

An extensive analysis of the class II (I-Ad)-restricted T cell repertoire for influenza hemagglutinin (HA) of the H3 subtype, elicited by natural infection, has shown that majority of CD4+ memory T cell clones focus on antibody-binding regions of HA, sites B and E, and are sensitive to the residue substitutions that have occurred in these regions during antigenic drift. The proliferative responses of CD4+ clones to synthetic peptides have identified T cell epitopes within site B, HA1 177-199 and HA1 182-199, and site E. HA1 56-76. The recognition specificity of T cell clones for antibody-selected mutant viruses, with single amino acid substitutions within these recognition sites identified residues 63, 189, 193 and 198 as being important for T cell recognition and thus established that BALB/c, CD4+ T cell clones were sensitive to the same substitutions known to abrogate BALB/c antibody recognition of the native HA. Our findings indicate extensive commonality of the B cell and T cell repertoires for HA, which may be relevant to an understanding of the immune pressures for antigenic drift, and, moreover, suggest that the antigen-specific B memory cell may be instrumental in selection of the peripheral T cell repertoire.

The structural requirements for class II (I-Ad)-restricted T cell recognition of influenza hemagglutinin: B cell epitopes define T cell epitopes

A majority of I-Ad-restricted CD4+ clones elicited by influenza X31 (H3N2) virus infection, recognize a synthetic peptide of hemagglutinin (HA) corresponding to an antibody binding region of the HA1 subunit (site B: HA1 177-199). The structural requirements for class II-restricted T cell recognition were investigated by determining the proliferative responses of representative CD4+ clones to truncated HA1 peptides and synthetic peptide analogues. Two distinct T cell epitopes were identified and CD4+ clones, specific for either determinant, were sensitive to the same single amino acid substitutions in synthetic peptides at HA1 193 S----N or HA1 198 A----E, that had featured in antigenic drift and abrogated antibody binding to native HA. Competitive inhibition studies, between stimulatory HA1 peptides and non-stimulatory analogue peptides, for antigen presentation to CD4+ clones established that the 193 S----N and 198 A----E substitutions could affect either interaction with the T cell receptor or class II molecule, according to the specificity of the CD4+ clone examined. The structural requirements for class II-restricted T cell recognition of the linear sequence determinants of HA are, therefore, integrally linked to conformation-dependent antibody recognition of the native molecule.