Reconsidering targeted toxins to eliminate HIV infection: you gotta have HAART

The success of highly active anti-retroviral therapy (HAART) has inspired new concepts for eliminating HIV from infected individuals. A major obstacle is the persistence of long-lived reservoirs of latently infected cells that might become activated at some time after cessation of therapy. We propose that, in the context of treatment strategies to deliberately activate and eliminate these reservoirs, hybrid toxins targeted to kill HIV-infected cells be reconsidered in combination with HAART. Such combinations might also prove valuable in protocols aimed at preventing mother-to-child transmission and establishment of infection immediately after exposure to HIV. We suggest experimental approaches in vitro and in animal models to test various issues related to safety and efficacy of this concept.

Recombinant modified vaccinia virus Ankara-simian immunodeficiency virus gag pol elicits cytotoxic T lymphocytes in rhesus monkeys detected by a major histocompatibility complex class I/peptide tetramer

The utility of modified vaccinia virus Ankara (MVA) as a vector for eliciting AIDS virus-specific cytotoxic T lymphocytes (CTL) was explored in the simian immunodeficiency virus (SIV)/rhesus monkey model. After two intramuscular immunizations with recombinant MVA-SIVSM gag pol, the monkeys developed a Gag epitope-specific CTL response readily detected in peripheral blood lymphocytes by using a functional killing assay. Moreover, those immunizations also elicited a population of CD8+ T lymphocytes in the peripheral blood that bound a specific major histocompatibility complex class I/peptide tetramer. These Gag epitope-specific CD8+ T lymphocytes also were demonstrated by using both functional and tetramer-binding assays in lymph nodes of the immunized monkeys. These observations suggest that MVA may prove a useful vector for an HIV-1 vaccine. They also suggest that tetramer staining may be a useful technology for monitoring CTL generation in vaccine trials in nonhuman primates and in humans.

A new vaccinia virus intermediate transcription factor

Transcription of the vaccinia virus genome is mediated by a virus-encoded multisubunit DNA-dependent RNA polymerase in conjunction with early-, intermediate-, and late-stage-specific factors. Previous studies indicated that two virus-encoded proteins (capping enzyme and VITF-1) and one unidentified cellular protein (VITF-2) are required for specific transcription of an intermediate promoter template in vitro. We have now extensively purified an additional virus-induced intermediate transcription factor with a native mass of approximately 100 kDa.

The immunogenicity and efficacy of intranasally or parenterally administered replication-deficient vaccinia-parainfluenza virus type 3 recombinants in rhesus monkeys

Immunization of rhesus monkeys with modified vaccinia Ankara (MVA) recombinants expressing the haemagglutinin-neuraminidase (HN) or fusion (F) glycoproteins of human parainfluenza virus type 3 (HPIV3) was compared with an intranasally-administered live, attenuated HPIV3 vaccine candidate, the cp45 derivative of the JS strain of wildtype HPIV3. The MVA recombinants, when given parenterally (i.m.) or as a parenteral-local (i.m. and i.t.) combination, induced an antibody response comparable to that of cp45 and protected the upper and lower respiratory tracts of the rhesus monkeys against challenge with wildtype HPIV3. When given by the i.n. route alone, the MVA/PIV3 recombinants induced a serum antibody response that was comparable to that of cp45 and induced resistance in the lower respiratory tract. Despite the ability of the intranasally-administered MVA/PIV3 recombinants to stimulate a good serological response and to protect the lower respiratory tract, they unexpectedly failed to induce a significant level of resistance in the upper respiratory tract. The live, attenuated virus vaccine candidate induced almost complete resistance in both the upper and lower tracts. The data thus identify two vaccine candidates that can protect both the upper and lower respiratory tracts of rhesus monkey, parenterally-administered MVA/PIV3 and intranasally-administered cp45. Further studies with these vaccines in non-human primates and humans should identify the relative merits of these immunogens for use in the very young infant.

gp100/pmel 17 is a murine tumor rejection antigen: induction of "self"-reactive, tumoricidal T cells using high-affinity, altered peptide ligand

Many tumor-associated antigens are nonmutated, poorly immunogenic tissue differentiation antigens. Their weak immunogenicity may be due to "self"-tolerance. To induce autoreactive T cells, we studied immune responses to gp100/pmel 17, an antigen naturally expressed by both normal melanocytes and melanoma cells. Although a recombinant vaccinia virus (rVV) encoding the mouse homologue of gp100 was nonimmunogenic, immunization of normal C57BL/6 mice with the rVV encoding the human gp100 elicited a specific CD8(+) T cell response. These lymphocytes were cross-reactive with mgp100 in vitro and treated established B16 melanoma upon adoptive transfer. To understand the mechanism of the greater immunogenicity of the human version of gp100, we characterized a 9-amino acid (AA) epitope, restricted by H-2Db, that was recognized by the T cells. The ability to induce specific T cells with human but not mouse gp100 resulted from differences within the major histocompatibility complex (MHC) class I-restricted epitope and not from differences elsewhere in the molecule, as was evidenced by experiments in which mice were immunized with rVV containing minigenes encoding these epitopes. Although the human (hgp10025-33) and mouse (mgp10025-33) epitopes were homologous, differences in the three NH2-terminal AAs resulted in a 2-log increase in the ability of the human peptide to stabilize "empty" Db on RMA-S cells and a 3-log increase in its ability to trigger interferon gamma release by T cells. Thus, the fortuitous existence of a peptide homologue with significantly greater avidity for MHC class I resulted in the generation of self-reactive T cells. High-affinity, altered peptide ligands might be useful in the rational design of recombinant and synthetic vaccines that target tissue differentiation antigens expressed by tumors.

DNA packaging mutant: repression of the vaccinia virus A32 gene results in noninfectious, DNA-deficient, spherical, enveloped particles

The vaccinia virus A32 open reading frame was predicted to encode a protein with a nucleoside triphosphate-binding motif and a mass of 34 kDa. To investigate the role of this protein, we constructed a mutant in which the original A32 gene was replaced by an inducible copy. The recombinant virus, vA32i, has a conditional lethal phenotype: infectious virus formation was dependent on isopropyl-beta-D-thiogalactopyranoside (IPTG). Under nonpermissive conditions, the mutant synthesized early- and late-stage viral proteins, as well as viral DNA that was processed into unit-length genomes. Electron microscopy of cells infected in the absence of IPTG revealed normal-appearing crescents and immature virus particles but very few with nucleoids. Instead of brick-shaped mature particles with defined core structures, there were numerous electron-dense, spherical particles. Some of these spherical particles were wrapped with cisternal membranes, analogous to intracellular and extracellular enveloped virions. Mutant viral particles, purified by sucrose density gradient centrifugation, had low infectivity and transcriptional activity, and the majority were spherical and lacked DNA. Nevertheless, the particle preparation contained representative membrane proteins, cleaved and uncleaved core proteins, the viral RNA polymerase, the early transcription factor and several enzymes, suggesting that incorporation of these components is not strictly coupled to DNA packaging.

Broad spectrum chemokine antagonistic activity of a human poxvirus chemokine homolog

A secreted CC chemokine homolog, encoded by the MC148 gene of molluscum contagiosum virus, potently interfered with the chemotaxis of human monocytes, lymphocytes, and neutrophils in response to a large number of CC and CXC chemokines with diverse receptor specificities. Evidence that the viral protein binds to human chemokine receptors was obtained by competition binding and calcium mobilization experiments. The broad spectrum chemokine antagonistic activity of MC148 can explain the prolonged absence of an inflammatory response in skin tumors that harbor replicating molluscum contagiosum virus.

The envelope protein encoded by the A33R gene is required for formation of actin-containing microvilli and efficient cell-to-cell spread of vaccinia virus

The vaccinia virus (VV) A33R gene encodes a highly conserved 23- to 28-kDa glycoprotein that is specifically incorporated into the viral outer envelope. The protein is expressed early and late after infection, consistent with putative early and late promoter sequences. To determine the role of the protein, two inducible A33R mutants were constructed, one with the late promoter and one with the early and late A33R promoter elements. Decreased A33R expression was associated with small plaques that formed comets in liquid medium. Using both an antibiotic resistance gene and a color marker, an A33R deletion mutant, vA33delta, was isolated, indicating that the A33R gene is not essential for VV replication. The plaques formed by vA33delta, however, were tiny, indicating that the A33R protein is necessary for efficient cell-to-cell spread. Rescue of the large-plaque phenotype was achieved by inserting a new copy of the A33R gene into the thymidine kinase locus, confirming the specific genetic basis of the phenotype. Although there was a reduction in intracellular virus formed in cells infected with vA33delta, the amount of infectious virus in the medium was increased. The virus particles in the medium had the buoyant density of extracellular enveloped viruses (EEV). Additionally, amounts of vA33delta cell-associated extracellular enveloped viruses (CEV) were found to be normal. Immunogold electron microscopy of cells infected with vA33delta demonstrated the presence of the expected F13L and B5R proteins in wrapping membranes and EEV; however, fully wrapped vA33delta intracellular enveloped viruses (IEV) were rare compared to partially wrapped particles. Specialized actin tails that propel IEV particles to the periphery and virus-tipped microvilli (both common in wild-type-infected cells) were absent in cells infected with vA33delta. This is the first deletion mutant in a VV envelope gene that produces at least normal amounts of fully infectious EEV and CEV and yet has a small-plaque phenotype. These data support a new model for VV spread, emphasizing the importance of virus-tipped actin tails.

Role for the vaccinia virus A36R outer envelope protein in the formation of virus-tipped actin-containing microvilli and cell-to-cell virus spread

A small-plaque-forming vaccinia virus mutant with a deletion in the A36R gene encoding an outer envelope protein (Parkinson and Smith, Virology, 204, 376-390, 1994) was shown to assemble wrapped forms of intra- and extracellular virus particles and to mediate acid-induced polykaryon formation. The intracellular virions, however, did not acquire actin tails and those on the cell surface were not associated with specialized microvilli. This phenotype is similar to that of the A34R (E. J. Wolffe, E. Katz, A. Weisberg, and B. Moss, J. Virol 71, 3904-3915, 1997) and A33R (R. Roper, E. J. Wolffe, A. Weisberg, and B. Moss, J. Virol., in press) deletion mutants. Taken together, these data support a model in which the envelope proteins encoded by the A33R, A34R, and A36R genes are all required for nucleation of actin tails, which facilitate dissemination rather than egress of virus particles.

Apoptosis induced by a postbinding step of vaccinia virus entry into Chinese hamster ovary cells

Unlike most cell types examined, nonpermissive Chinese hamster ovary (CHO) cells readily underwent apoptosis upon infection with vaccinia virus (VV). Apoptosis was observed as early as 3 h postinfection with an electrophoretic assay of DNA fragmentation and by 8 h using an in situ (TUNEL) assay. The CHO hr gene from cowpox virus, which overcomes host range restriction of VV in CHO cells, merely delayed the onset of apoptosis by approximately 3 h. Intermediate and late viral protein synthesis were not necessary for apoptosis since these events do not proceed under nonpermissive conditions. Apoptosis also occurred in the presence of cytosine arabinoside or cycloheximide, which inhibits DNA or protein synthesis, respectively, and after infection with a mutant virus that is blocked in early transcription. We also demonstrated that viral early transcription was not required for induction of apoptosis by infecting CHO cells with psoralen/UV-inactivated virus. On the other hand, apoptosis was inhibited by a neutralizing antibody to the virion L1R protein added either before or after virus attachment to cells. These results indicate that a postbinding step associated with cell entry is sufficient and required for induction of apoptosis in CHO cells. Recent progress on apoptotic signaling pathways raises the possibility that a cellular receptor for VV may be involved in apoptosis.

Chemokine homolog of molluscum contagiosum virus: sequence conservation and expression

An analysis of the complete Molluscum contagiosum virus (MCV-1) genome sequence revealed a 104-amino-acid open reading frame (MC148R) that is structurally related to the beta (CC) family of chemokines. The predicted MCV chemokine homolog (MCCH) has a deletion in the NH2-terminal activation domain, suggesting the absence of chemoattractant activity. The principal objectives of the present study were to determine whether: (i) MCCH is conserved in independent isolates of MCV-1 and MCV-2; (ii) MCCH mRNA is expressed in vivo; and (iii) the MCCH protein is secreted from mammalian cells. The nucleotide sequence of the MCCH gene locus was determined for 27 isolates of MCV-1 and 2 of MCV-2 obtained from 29 MCV-infected individuals. In each case, the characteristic CC sequence, the NH2-terminal deletion, and the length of the open reading frame were conserved, although there were some, mostly conservative, amino acid substitutions. Since MCV cannot be propagated in cell culture, mRNA was synthesized in vitro by the early transcription apparatus in purified MCV virions. MCCH RNA was amplified by RT-PCR; the sequence included the complete open reading frame and extended 40 to 50 nucleotides past the first poxviral termination signal (TTTTTNT). Similar RT-PCR results were obtained using total cellular RNA derived from MCV-infected tissue specimens. Finally, the MCCH open reading frame was expressed in a vaccinia virus vector and the predicted size polypeptide was secreted into the medium, as determined by Western blotting. Taken together, our data support the prediction that MCV expresses a secreted chemokine homolog that could antagonize the inflammatory response in vivo.

Mucosal immunization with HIV-1 peptide vaccine induces mucosal and systemic cytotoxic T lymphocytes and protective immunity in mice against intrarectal recombinant HIV-vaccinia challenge

Mucosal tissues are major sites of HIV entry and initial infection. Thus, the induction of a mucosal cytotoxic T lymphocyte (CTL) response is an important feature for an effective HIV vaccine. However, little is known about approaches to induce such a protective CTL response in the mucosa. Here for the first time we show that intrarectal immunization with a synthetic, multideterminant HIV peptide plus cholera toxin adjuvant induced long-lasting, antigen-specific CTL memory in both the inductive (Peyer's patch) and effector (lamina propria) mucosal sites, as well as in systemic sites (spleen), whereas systemic immunization induced specific CTL only in the spleen. Cholera toxin adjuvant, while enhancing the response, was not essential. The CTL recognized target cells either pulsed with HIV peptide or expressing endogenous whole envelope glycoprotein of Mr 160,000 (gp160). Exploring the requirements for CTL induction, we show that mucosal CTL responses are both interleukin 12 and interferon-gamma dependent by using antibody-treated and knock-out mice. Finally, to determine whether a mucosal response is actually protective against local mucosal challenge with virus, we show that intrarectal immunization with the synthetic HIV peptide vaccine protected mice against infection via mucosal challenge with a recombinant vaccinia virus expressing HIV-1IIIB gp160. These studies provide an approach to development of an HIV vaccine that induces CTL immunity in the mucosal and systemic immune systems and protects against mucosal infection with a virus expressing HIV-1 gp160.

Ultraviolet-induced cell death blocked by a selenoprotein from a human dermatotropic poxvirus

Selenium, an essential trace element, is a component of prokaryotic and eukaryotic antioxidant proteins. A candidate selenoprotein homologous to glutathione peroxidase was deduced from the sequence of molluscum contagiosum, a poxvirus that causes persistent skin neoplasms in children and acquired immunodeficiency syndrome (AIDS) patients. Selenium was incorporated into this protein during biosynthesis, and a characteristic stem-loop structure near the end of the messenger RNA was required for alternative selenocysteine decoding of a potential UGA stop codon within the open reading frame. The selenoprotein protected human keratinocytes against cytotoxic effects of ultraviolet irradiation and hydrogen peroxide, providing a mechanism for a virus to defend itself against environmental stress.

Repression of the A8L gene, encoding the early transcription factor 82-kilodalton subunit, inhibits morphogenesis of vaccinia virions

The vaccinia virus early transcription factor (VETF) is a DNA binding protein comprised of 70- and 82-kDa subunits encoded by the D6R and A8L genes, respectively. A previous investigation suggested a novel role for the 70-kDa subunit in the morphogenesis of vaccinia virus particles. The principal objectives of the present study were to determine if the 82-kDa subunit of VETF is also required for morphogenesis and, if so, whether the block occurs before or after the incorporation of the genome into the assembling virus particle. To address these and other questions, we constructed and characterized a conditionally lethal recombinant vaccinia virus in which the A8L gene is stringently repressed by the Escherichia coli lac operator system. The amount of 82-kDa protein synthesized could be regulated by the amount of inducer: from undetectable to higher than normal levels. Virus replication, as determined by plaque formation or virus yield upon synchronous infection, was dependent on inducer. Nevertheless, de novo synthesis of the 82-kDa subunit was not required for viral early, intermediate, and late gene expression or DNA replication. Overexpression of the A8L gene alone, produced by high concentrations of inducer, inhibited viral late protein synthesis, whereas overexpression of the D6R gene alone or both VETF genes simultaneously had little inhibitory effect. Laser confocal fluorescence and quantitative electron microscopic analyses revealed that immature and DNA-containing intermediate stage particles accumulated in the absence of inducer, indicating that the A8L protein has a role in morphogenesis of the core and subsequent events.

Compact, synthetic, vaccinia virus early/late promoter for protein expression

Vaccinia virus, a member of the poxvirus family, is widely used as a mammalian cell expression vector. Vaccinia virus replicates in the cytoplasm and has its own transcriptional system, making it necessary to use viral promoters. Here, we describe the design, construction and use of a 40-bp synthetic, vaccinia virus promoter with largely overlapping early and late regulatory elements. Convenient plasmid transfer vectors are depicted for expression of one or two genes under control of strong early/late promoters and allowing for thymidine kinase (TK) or antibiotic selection of recombinant viruses.

Host range and cytopathogenicity of the highly attenuated MVA strain of vaccinia virus: propagation and generation of recombinant viruses in a nonhuman mammalian cell line

Modified vaccinia virus Ankara (MVA), attenuated by over 500 passages in primary chick embryo fibroblasts (CEF), is presently being used as a safe expression vector. We compared the host ranges of MVA and the parental Ankara strain in CEF and 15 permanent cell lines. The cells could be grouped into three categories: permissive, semipermissive, and nonpermissive. For MVA, the permissive category consisted of primary CEF, a quail cell line derived from QT6, and the Syrian hamster cell line BHK-21. Only in BHK-21 cells did the virus yield approach that occurring in primary CEF. The semipermissive category included two African green monkey cell lines: BS-C-1 and CV-1. The nonpermissive category for MVA consisted of three human cell lines HeLa, 293, and SW 839; one rhesus monkey cell line FRhK-4; two Chinese hamster cell lines CHO and CHL; one pig cell line PK(15); and three rabbit cell lines RK13, RAB-9, and SIRC. The grouping for MVA with a restored K1L host range gene was similar except for the inclusion of RK13 cells among permissive lines. The grouping for the Ankara strain, however, was quite different with more permissive and semipermissive cell lines. Nevertheless, in cells that were permissive for MVA, the virus replicated to higher levels than Ankara, consistent with both positive and negative growth elements associated with the adaptation of MVA. The cell lines were also characterized according to their susceptibility to MVA-induced cytopathic effects, expression of a late promoter regulated reporter gene by an MVA recombinant, and stage at which virion morphogenesis was blocked. Finally, the permissive BHK-21 cell line was shown to be competent for constructing and propagating recombinant MVA, providing an alternative to primary CEF.

Immunogenicity of recombinant vaccinia viruses that display the HIV type 1 envelope glycoprotein on the surface of infectious virions

A chimeric protein, consisting of the extracellular domain of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein attached to the transmembrane and cytoplasmic domains of the vaccinia virus B5R glycoprotein, is displayed on the surface of extracellular recombinant vaccinia virus particles, whereas the unmodified full-length HIV-1 glycoprotein is not (Katz E, et al., J Virol 1997;71:3178-3187). Here, we report that rabbits and mice inoculated with recombinant vaccinia viruses that express the chimeric protein developed higher HIV-specific antibody responses than animals inoculated with vaccinia virus that expressed the unmodified HIV glycoprotein. These data suggest that the immunogenicity of recombinant proteins may be enhanced by their presentation on the surface of vaccinia virus particles.

Poxviruses as expression vectors

Poxviruses are widely used for the cytoplasmic expression of recombinant genes in mammalian cells. Recent improvements allow high expression and simplify the integration of multiple foreign genes. Vaccinia virus mutants and other poxviruses that undergo abortive infection in mammalian cells are receiving special attention because of their diminished cytopathic effects and increased safety. New replicating and 'non-replicating' vectors, encoding the bacteriophage T7 RNA polymerase for transcription of recombinant genes, have been engineered.

Inhibition of vaccinia virus replication by N-(phosphonoacetyl)-L-aspartate: differential effects on viral gene expression result from a reduced pyrimidine nucleotide pool

The replication of vaccinia virus was reduced by 3 logs in cells that had been treated before and during infection with a concentration of N-(phosphonoacetyl)-L-aspartate (PALA) which lowered the UTP and CTP to 5 and 20% of controls, respectively, without affecting cell viability. The antiviral activity of PALA was reversed with uridine, indicating that it was entirely due to the diminution in pyrimidine nucleotides. Analysis of viral proteins revealed prolonged synthesis of some early stage species but a drastic reduction in late stage species, even though the nucleotide concentrations remained relatively constant throughout the infection. Although the gene expression pattern resembled that caused by a potent inhibitor of DNA synthesis, viral DNA accumulation was reduced by only 60%. Very little of the DNA made in the presence of PALA was converted to genome length molecules. The effect of PALA on transcription of early genes was complex: there was a twofold increase in the amount of a relatively short mRNA of 500 nucleotides but a two- to threefold decrease in the amount of a 4300-nucleotide mRNA encoding the largest subunit of RNA polymerase. In contrast, PALA severely inhibited the accumulation of viral intermediate and late stage mRNAs. The extreme sensitivity of vaccinia virus to PALA and the differential effects of the drug on viral gene expression result from the cascade mechanism of viral gene regulation.

Addition of the MSA1 signal and anchor sequences to the malaria merozoite surface antigen 1 C-terminal region enhances immunogenicity when expressed by recombinant vaccinia virus

Genes encoding four different C-terminal fragments of a Plasmodium falciparum merozoite surface antigen were generated: MSA1C-(Si,A), containing signal and anchor regions of MSA1; MSA1C-(Si,nA), containing the signal but not the anchor; MSA1C-(nSi,A), containing the anchor but not the signal, and MSA1C-(nSi,nA) containing neither the signal nor the anchor region. Each gene was inserted into the thymidine kinase region of vaccinia virus, under the control of a synthetic strong early/ late promoter. When the plasmodial genes were expressed in cells infected by the recombinant vaccinia virus, the two proteins containing the signal region were transported to the surface of infected cells. Infection of mice and rabbits with the latter recombinant viruses stimulated C-terminal-specific antibody levels that were 10-80-fold higher than those induced by the two recombinant viruses without the signal region. The combination of the signal and anchor regions with the C-terminal MSA1 protein also generated the most effective neutralization in a P. falciparum invasion assay.

Mutagenesis of phospholipase D defines a superfamily including a trans-Golgi viral protein required for poxvirus pathogenicity

Phospholipase D (PLD) genes are members of a superfamily that is defined by several highly conserved motifs. PLD in mammals has been proposed to play a role in membrane vesicular trafficking and signal transduction. Using site-directed mutagenesis, 25 point mutants have been made in human PLD1 (hPLD1) and characterized. We find that a motif (HxKxxxxD) and a serine/threonine conserved in all members of the PLD superfamily are critical for PLD biochemical activity, suggesting a possible catalytic mechanism. Functional analysis of catalytically inactive point mutants for yeast PLD demonstrates that the meiotic phenotype ensuing from PLD deficiency in yeast derives from a loss of enzymatic activity. Finally, mutation of an HxKxxxxD motif found in a vaccinia viral protein expressed in the Golgi complex results in loss of efficient vaccinia virus cell-to-cell spreading, implicating the viral protein as a member of the superfamily and suggesting that it encodes a lipid modifying or binding activity. The results suggest that vaccinia virus and hPLD1 may act through analogous mechanisms to effect viral cellular egress and vesicular trafficking, respectively.

Dose ranging study of mometasone furoate (Nasonex) in seasonal allergic rhinitis

BACKGROUND

Topical nasal corticosteroids are rapidly gaining acceptance as first-line therapy for seasonal allergic rhinitis, but there is a desire for effective corticosteroids with an improved safety profile over existing products.

OBJECTIVE

A multicenter, double-blind dose ranging study was conducted to compare the activity and tolerance of four doses of mometasone furoate nasal spray (tradename Nasonex) and placebo in adult patients with seasonal allergic rhinitis.

METHODS

Four hundred eighty patients with seasonal allergic rhinitis were enrolled and randomized to receive mometasone furoate nasal spray 50 micrograms (n = 96), 100 micrograms (n = 95), 200 micrograms (n = 98) or 800 micrograms (n = 95), or placebo vehicle (n = 95) once daily for 28 days.

RESULTS

All of the doses of mometasone furoate nasal spray showed activity in reducing the severity of rhinitis. The 200-microgram dose reduced total nasal symptom scores and total symptom scores throughout the study (P < .05 versus placebo vehicle). The 50-microgram dose and the 100-microgram dose showed less consistent activity at early timepoints (days 3 and 7), while the 800 microgram dose did not provide significant additional benefits over the 200-microgram dose. All dose levels were well tolerated

CONCLUSION

The results of this trial indicate that 200 micrograms once daily is the optimum dose of mometasone furoate nasal spray for the treatment of seasonal allergic rhinitis.

The genome of molluscum contagiosum virus: analysis and comparison with other poxviruses

Analysis of the molluscum contagiosum virus (MCV) genome revealed that it encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV). The corresponding OPV proteins comprise those known to be essential for replication as well as many that are still uncharacterized, including 2 of less than 60 amino acids that had not been previously noted. The OPV proteins most highly conserved in MCV are involved in transcription; the least conserved include membrane glycoproteins. Twenty of the MCV proteins with OPV counterparts also have cellular homologs and additional MCV proteins have conserved functional motifs. Of the 77 predicted MCV proteins without OPV counterparts, 10 have similarity to other MCV proteins and/or distant similarity to proteins of other poxviruses and 16 have cellular homologs including some predicted to antagonize host defenses. Clustering poxvirus proteins by sequence similarity revealed 3 unique MCV gene families and 8 families that are conserved in MCV and OPV. Two unique families contain putative membrane receptors; the third includes 2 proteins, each containing 2 DED apoptosis signal transduction domains. Additional families with conserved patterns of cysteines and putative redox active centers were identified. Promoters, transcription termination signals, and DNA concatemer resolution sequences are highly conserved in MCV and OPV. Phylogenetic analysis suggested that MCV, OPV, and leporipoxviruses radiated from a common poxvirus ancestor after the divergence of avipoxviruses. Despite the acquisition of unique genes for host interactions and changes in GC content, the physical order and regulation of essential ancestral poxvirus genes have been largely conserved in MCV and OPV.

The A34R glycoprotein gene is required for induction of specialized actin-containing microvilli and efficient cell-to-cell transmission of vaccinia virus

The mechanisms allowing vaccinia virus to spread from cell to cell are incompletely understood. The A34R gene of vaccinia virus encodes a glycoprotein that is localized in the outer membranes of extracellular virions. The small-plaque phenotype of an A34R deletion mutant was similar to that of mutants with deletions in other envelope genes that fail to produce extracellular vaccinia virions. Transmission electron microscopy, however, revealed that the A34R mutant produced numerous extracellular particles that were labeled with antibodies to other outer-envelope proteins and with protein A-colloidal gold. Fluorescence and scanning electron microscopy indicated that expression of the A34R protein was necessary for detection of vaccinia virus-induced actin tails, which provide motility to the intracellular enveloped form of vaccinia virus, and of virus-tipped specialized microvilli that project from the cell. The ability of vaccinia virus-infected cells to form syncytia after a brief exposure to a pH below 6, known as fusion from within, failed to occur in the absence of expression of the A34R protein; nevertheless, purified A34R- virions were capable of mediating low-pH-induced fusion from without. The present study provides genetic and microscopic evidence for the involvement of a specific viral protein in the formation or stability of actin-containing microvilli and for a role of these structures in cell-to-cell spread rather than in formation of extracellular virions.