Inhibited Syncytium Formation Research Articles

Inhibitory Effects of Cryptotanshinone and Dihydrotanshinone I on Intracellular Trafficking of Viral Glycoproteins.

Antiviral agents that target the viral envelope surface glycoproteins can disrupt the interactions between the viral glycoproteins and host cell receptors, thereby preventing viral entry into host cells. However, the mechanisms underlying glycoprotein processing and cellular trafficking have not been fully elucidated. In this study, we aimed to investigate the mechanism of action of cryptotanshinone (CTN) and dihydrotanshinone I (DTN) as inhibitors of viral glycoprotein trafficking, by assessing their inhibitory action on syncytium formation and cytopathic effects. CTN and DTN were isolated and characterized from Salvia miltiorrhiza; they effectively inhibited syncytium formation in Newcastle disease virus-infected baby hamster kidney cells. Both compounds inhibited the transport of viral G-proteins to the cell surface, resulting in intracellular accumulation. These results suggest that CTN and DTN are potential glycoprotein trafficking inhibitors that function at the Golgi apparatus. Overall, our results indicate that CTN and DTN suppress intracellular glycosylation by competing as inhibitors of glycosylation trafficking.

Human cytomegalovirus glycoprotein variants governing viral tropism and syncytium formation in epithelial cells and macrophages.

Human cytomegalovirus (HCMV) displays a broad cell tropism, and the infection of biologically relevant cells such as epithelial, endothelial, and hematopoietic cells supports viral transmission, systemic spread, and pathogenesis in the human host. HCMV strains differ in their ability to infect and replicate in these cell types, but the genetic basis of these differences has remained incompletely understood. In this study, we investigated HCMV strain VR1814, which is highly infectious for epithelial cells and macrophages and induces cell-cell fusion in both cell types. A VR1814-derived bacterial artificial chromosome (BAC) clone, FIX-BAC, was generated many years ago but has fallen out of favor because of its modest infectivity. By sequence comparison and genetic engineering of FIX, we demonstrate that the high infectivity of VR1814 and its ability to induce syncytium formation in epithelial cells and macrophages depends on VR1814-specific variants of the envelope glycoproteins gB, UL128, and UL130. We also show that UL130-neutralizing antibodies inhibit syncytium formation, and a FIX-specific mutation in UL130 is responsible for its low infectivity by reducing the amount of the pentameric glycoprotein complex in viral particles. Moreover, we found that a VR1814-specific mutation in US28 further increases viral infectivity in macrophages, possibly by promoting lytic rather than latent infection of these cells. Our findings show that variants of gB and the pentameric complex are major determinants of infectivity and syncytium formation in epithelial cells and macrophages. Furthermore, the VR1814-adjusted FIX strains can serve as valuable tools to study HCMV infection of myeloid cells.IMPORTANCEHuman cytomegalovirus (HCMV) is a major cause of morbidity and mortality in transplant patients and the leading cause of congenital infections. HCMV infects various cell types, including epithelial cells and macrophages, and some strains induce the fusion of neighboring cells, leading to the formation of large multinucleated cells called syncytia. This process may limit the exposure of the virus to host immune factors and affect pathogenicity. However, the reason why some HCMV strains exhibit a broader cell tropism and why some induce cell fusion more than others is not well understood. We compared two closely related HCMV strains and provided evidence that small differences in viral envelope glycoproteins can massively increase or decrease the virus infectivity and its ability to induce syncytium formation. The results of the study suggest that natural strain variations may influence HCMV infection and pathogenesis in humans.

Multi-clonal SARS-CoV-2 neutralization by antibodies isolated from severe COVID-19 convalescent donors.

The interactions between antibodies, SARS-CoV-2 and immune cells contribute to the pathogenesis of COVID-19 and protective immunity. To understand the differences between antibody responses in mild versus severe cases of COVID-19, we analyzed the B cell responses in patients 1.5 months post SARS-CoV-2 infection. Severe, and not mild, infection correlated with high titers of IgG against Spike receptor binding domain (RBD) that were capable of ACE2:RBD inhibition. B cell receptor (BCR) sequencing revealed that VH3-53 was enriched during severe infection. Of the 22 antibodies cloned from two severe donors, six exhibited potent neutralization against authentic SARS-CoV-2, and inhibited syncytia formation. Using peptide libraries, competition ELISA and mutagenesis of RBD, we mapped the epitopes of the neutralizing antibodies (nAbs) to three different sites on the Spike. Finally, we used combinations of nAbs targeting different immune-sites to efficiently block SARS-CoV-2 infection. Analysis of 49 healthy BCR repertoires revealed that the nAbs germline VHJH precursors comprise up to 2.7% of all VHJHs. We demonstrate that severe COVID-19 is associated with unique BCR signatures and multi-clonal neutralizing responses that are relatively frequent in the population. Moreover, our data support the use of combination antibody therapy to prevent and treat COVID-19.

A TLR7 agonist activates bovine Th1 response and exerts antiviral activity against bovine leukemia virus

Bovine leukemia virus (BLV) infection is a bovine chronic infection caused by BLV, a member of the genus Deltaretrovirus. In this study, we examined the immunomodulatory effects of GS-9620, a toll-like receptor (TLR) 7 agonist, in cattle (Bos taurus) and its therapeutic potential for treating BLV infection. GS-9620 induced cytokine production in peripheral blood mononuclear cells (PBMCs) as well as CD80 expression in CD11c+ cells and increased CD69 and interferon (IFN)-γ expressions in T cells. Removing CD11c+ cells from PBMCs decreased CD69 expression in T cells in the presence of GS-9620. These results suggest that TLR7 agonism promotes T-cell activation via CD11c+ cells. Analyses using PBMCs from BLV-infected cattle revealed that TLR7 expression in CD11c+ cells was upregulated during late-stage BLV infection. Furthermore, GS-9620 increased IFN-γ and TNF-α production and inhibited syncytium formation in vitro, suggesting that GS-9620 may be used to treat BLV infection.

In vitro anti-HIV activity of ethanol extract from gandarusa (Justicia gendarussa Burm. f) leaves.

Anti retroviral drugs for HIV has problems with uncomfortable side effects and that endanger the lives of HIV sufferers. Several herbs have been empirically proven to have an effect on HIV eradication through inhibition of reverse transcriptase. One of such antiviral herbs is Justicia gendarussa (J. gendarussa). The aim of research is to evaluate anti-HIV activity of 70% fractionated-ethanol extract (with releasing alkaloids) and 70% ethanol extract (without releasing alkaloids) of J. gendarussa leaves on in vitro HIV-infected of MOLT-4 cells. The effect of the extracts in inhibiting viral replication and fusion process on acute HIV infection was identified through syncytia formation assay. Effect of the extracts on HIV p24 antigen was evaluated using HIV-1 p24 ELISA kit. It was found that 70% fractionated-ethanol extract and 70% ethanol extract of J. gendarussa leaves significantly inhibited of HIV replication by inhibition of syncytia formation, where the 50% effective concentration (EC50) values of the 70% fractionated- ethanol extract and 70% ethanol extract are 70.5 μg/mL and 228.7 μg/mL, respectively. Both of the extracts were also significantly inhibited HIV replication by decreasing HIV p24 antigen level where the EC 50 values of the 70% fractionatedethanol extract and 70% ethanol extract are 88.8 μg/mL and 540.7 μg/mL, respectively. Moreover, it was found that 70% fractionated- ethanol extract of J. gendarussa leaves has anti-HIV activity since its EC50 values less than 100 μg/mL. It was concluded that J. gendarussa could be potentially developed into a phyto-pharmaceutical product due to its anti-HIV activity.

Conservation of a Neutralization Epitope of Human T-cell Leukemia Virus Type 1 (HTLV-1) among Currently Endemic Clinical Isolates in Okinawa, Japan.

Approximately one-tenth of the 10 million individuals living with human T-cell leukemia virus type-1 (HTLV-1) worldwide live in Japan. Most of these infected individuals live in the southwest region of Japan, including Okinawa prefecture; however, currently no prophylactic vaccine against HTLV-1 infection is available. For preventing the HTLV-1 spread, we previously generated a humanized monoclonal antibody (hu-LAT-27) that mediates both neutralization and antibody-dependent cellular cytotoxicity (ADCC). The neutralization epitope of LAT-27 is a linear amino acid sequence from residue 191 to 196 (Leu-Pro-His-Ser-Asn-Leu) of the HTLV-1 envelope gp46 protein. Here, we found that the LAT-27 epitope is well conserved among HTLV-1 clinical isolates prevalent in Okinawa. The hu-LAT-27 treatment inhibited syncytium formation by these clinical HTLV-1 isolates. Although an amino acid substitution at residue 192 in the LAT-27 epitope from proline to serine was found in a few HTLV-1 isolates, hu-LAT-27 could still react with a synthetic peptide carrying this amino acid substitution. These findings demonstrate the wide spectrum of hu-LAT-27 reactivity, suggesting that hu-LAT-27 may be a candidate drug for prophylactic passive immunization against HTLV-1 infection.

A novel glycoprotein D-specific monoclonal antibody neutralizes herpes simplex virus

The worldwide prevalence of herpes simplex virus (HSV) and the shortage of efficient vaccines and novel therapeutic strategies against HSV are widely global concerns. The abundance on the virion and the major stimulus for the virus-neutralizing antibodies makes gD a predominant candidate for cure of HSV infection. In this study, we generated a monoclonal antibody (mAb), termed m27f, targeting to glycoprotein D (gD) of HSV-2, which also has cross-reactivity against HSV-1 gD. It has a high level of neutralizing activity against both HSV-1 and HSV-2, and binds to a highly conserved region (residues 292–297) within the pro-fusion domain of gD. It can effectively block HSV cell-to-cell spread in vitro. The pre- or post-attachment neutralization assay and syncytium formation inhibition assay revealed that m27f neutralizes HSV at the post-binding stage. Moreover, therapeutic administration of m27f completely prevented infection-related mortality of mice challenged with a lethal dose of HSV-2. Our newly identified epitope for the neutralizing antibody would facilitate studies of gD-based HSV entry or vaccine design, and m27f itself demonstrated a high potential for adaptation as a protective or therapeutic drug against HSV.

Characterization of two monoclonal antibodies, 38F10 and 44D11, against the major envelope fusion protein of Helicoverpa armigera nucleopolyhedrovirus.

The envelope fusion protein F of baculoviruses is a class I viral fusion protein which play a significant role during virus entry into insect cells. F is initially synthesized as a precursor (F0) and then cleaved into a disulfide-linked F1 and F2 subunits during the process of protein maturation and secretion. To facilitate further investigation into the structure and function of F protein during virus infection, monoclonal antibodies (mAbs) against the F2 subunit of Helicoverpa armigera nucleopolyhedrovirus (HearNPV) (HaF) were generated. Two kinds of mAbs were obtained according to their different recognition epitopes: one kind of mAbs, as represented by 38F10, recognizes amino acid (aa) 85 to 123 of F2 and the other kind, represented by 44D11, recognizes aa 148 to 173 of F2. Western blot and immunofluorescence assay confirmed that both of the mAbs recognized the F protein expressed in HearNPV infected cells, however, only 44D11 could neutralize HearNPV infection. The results further showed that 44D11 may not interact with a receptor binding epitope, rather it was demonstrated to inhibit syncytium formation in cells expressing the HaF protein. The results imply that the monoclonal antibody 44D11 recognizes a region within HaF2 that may be involved in the F-mediated membrane fusion process.

Role of hydrogen sulfide in paramyxovirus infections.

Hydrogen sulfide (H2S) is an endogenous gaseous mediator that has gained increasing recognition as an important player in modulating acute and chronic inflammatory diseases. However, its role in virus-induced lung inflammation is currently unknown. Respiratory syncytial virus (RSV) is a major cause of upper and lower respiratory tract infections in children for which no vaccine or effective treatment is available. Using the slow-releasing H2S donor GYY4137 and propargylglycin (PAG), an inhibitor of cystathionine-γ-lyase (CSE), a key enzyme that produces intracellular H2S, we found that RSV infection led to a reduced ability to generate and maintain intracellular H2S levels in airway epithelial cells (AECs). Inhibition of CSE with PAG resulted in increased viral replication and chemokine secretion. On the other hand, treatment of AECs with the H2S donor GYY4137 reduced proinflammatory mediator production and significantly reduced viral replication, even when administered several hours after viral absorption. GYY4137 also significantly reduced replication and inflammatory chemokine production induced by human metapneumovirus (hMPV) and Nipah virus (NiV), suggesting a broad inhibitory effect of H2S on paramyxovirus infections. GYY4137 treatment had no effect on RSV genome replication or viral mRNA and protein synthesis, but it inhibited syncytium formation and virus assembly/release. GYY4137 inhibition of proinflammatory gene expression occurred by modulation of the activation of the key transcription factors nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF-3) at a step subsequent to their nuclear translocation. H2S antiviral and immunoregulatory properties could represent a novel treatment strategy for paramyxovirus infections. RSV is a global health concern, causing significant morbidity and economic losses as well as mortality in developing countries. After decades of intensive research, no vaccine or effective treatment, with the exception of immunoprophylaxis, is available for this infection as well as for other important respiratory mucosal viruses. This study identifies hydrogen sulfide as a novel cellular mediator that can modulate viral replication and proinflammatory gene expression, both important determinants of lung injury in respiratory viral infections, with potential for rapid translation of such findings into novel therapeutic approaches for viral bronchiolitis and pneumonia.

ChemInform Abstract: Stereocontrolled Total Synthesis and Biological Evaluation of (‐)‐ and (+)‐Petrosin and Its Derivatives.

ChemInformVolume 46, Issue 13 Natural Products ChemInform Abstract: Stereocontrolled Total Synthesis and Biological Evaluation of (-)- and (+)-Petrosin and Its Derivatives. Hiroki Toya, Hiroki Toya Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorTakahito Satoh, Takahito Satoh Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorKentaro Okano, Kentaro Okano Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorKiyosei Takasu, Kiyosei Takasu Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorMasataka Ihara, Masataka Ihara Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorAtsushi Takahashi, Atsushi Takahashi Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorHaruo Tanaka, Haruo Tanaka Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorHidetoshi Tokuyama, Hidetoshi Tokuyama Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this author Hiroki Toya, Hiroki Toya Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorTakahito Satoh, Takahito Satoh Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorKentaro Okano, Kentaro Okano Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorKiyosei Takasu, Kiyosei Takasu Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorMasataka Ihara, Masataka Ihara Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorAtsushi Takahashi, Atsushi Takahashi Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorHaruo Tanaka, Haruo Tanaka Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this authorHidetoshi Tokuyama, Hidetoshi Tokuyama Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, JapanSearch for more papers by this author First published: 12 March 2015 https://doi.org/10.1002/chin.201513279Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume46, Issue13March, 2015 RelatedInformation

NICTABA and UDA, two GlcNAc-binding lectins with unique antiviral activity profiles.

ObjectivesThis study aimed to assess the antiviral properties of a unique lectin (NICTABA) produced by the tobacco plant, Nicotiana tabacum.MethodsCellular assays were used to investigate the antiviral activity of NICTABA and Urtica dioica agglutinin (UDA). Surface plasmon resonance (SPR) studies were performed to study the sugar specificity and the interactions of both lectins with the envelope glycoproteins of HIV-1.ResultsThe N-acetyl-d-glucosamine (GlcNAc)-binding lectins exhibited broad-spectrum activity against several families of enveloped viruses including influenza A/B, Dengue virus type 2, herpes simplex virus types 1 and 2 and HIV-1/2. The IC50 of NICTABA for various HIV-1 strains, clinical isolates and HIV-2 assessed in PBMCs ranged from 5 to 30 nM. Furthermore, NICTABA inhibited syncytium formation between persistently HIV-1-infected T cells and uninfected CD4+ T lymphocytes and prevented DC-SIGN-mediated HIV-1 transmission to CD4+ target T lymphocytes. However, unlike many other antiviral carbohydrate-binding agents (CBAs) described so far, NICTABA did not block HIV-1 capture to DC-SIGN+ cells and it did not interfere with the binding of the human monoclonal antibody 2G12 to gp120. SPR studies with HIV-1 envelope glycoproteins showed that the affinity of NICTABA for gp120 and gp41 was in the low nanomolar range. The specific binding of NICTABA to gp120 could be prevented in the presence of a GlcNAc trimer, but not in the presence of mannose trimers. NICTABA displayed no antiviral activity against non-enveloped viruses.ConclusionsSince CBAs possess a high genetic barrier for the development of viral resistance and NICTABA shows a broad antiviral activity profile, this CBA may qualify as a potential antiviral candidate with a pleiotropic mode of action aimed at targeting the entry of enveloped viruses.

Stereocontrolled total synthesis and biological evaluation of (−)- and (+)-petrosin and its derivatives

Total synthesis of (−)- and (+)-petrosin was accomplished. Stereocontrolled construction of the quinolizidine ring was achieved through a diastereoselective Mannich reaction and an aza-Michael reaction. Head-to-tail dimerization was performed by assembly of the two monomers using Suzuki–Miyaura cross coupling and subsequent ring-closing metathesis to construct the 16-membered ring. Biological evaluation of synthetic (−)- and (+)-petrosin and its derivatives indicated that the bispiperidine structure was necessary for the inhibition of syncytium formation.

Generation of HIV-1 potent and broad neutralizing antibodies by immunization with postfusion HR1/HR2 complex

The envelope glycoproteins are major targets for HIV vaccines. The N-terminal and the C-terminal regions of the gp41 interact to form six helix bundles that are responsible for the fusion between the viral and the target cell membranes. Monoclonal antibodies (Abs) able to disrupt the formation of this complex or to interfere with it could inhibit HIV fusion. Most of the well described gp41-specific broadly neutralizing Abs target conformational epitopes within the membrane proximal region of gp41 (MPER) and recognize linear peptides. In this study, a stable human transfected cell line, expressing a well folded heptad repeat regions 1 (HR1)/HR2 postfusion complex was developed. Transfected cells were highly immunogenic in mice and allowed the generation of 40 complex specific B-cell clones. Three of them were able to neutralize efficiently both HIV-1 laboratory adapted virus and primary isolates from different clades. Two neutralizing Abs (Nabs) FC-2 and FC-3 bound to a recombinant folded gp140 and blocked with a high potency HR1/HR2 fusion complex formation in vitro. The conformational epitopes of the three antibodies are different to 2F5, 4E10, D5 or NC-1 and mainly located in the MPER region. Abs were capable of inhibiting syncytium formation by blocking spatial interactions between HR1 and HR2 regions. These findings suggest that immunogenicity of gp41 is achievable and that the use of a fusion complex expressing human cell line is a highly potent immunogen to generate neutralizing antibodies against gp41 envelope glycoprotein.

Inhibitory Effect of Chondroitin Sulfate Type E on the Binding Step of Human T-Cell Leukemia Virus Type 1

Cell surface heparan sulfate proteoglycans (HSPGs) are involved in the binding and entry of human T-cell leukemia virus type 1 (HTLV-1) into host cells, while sulfated polysaccharides such as heparin inhibit HTLV-1 infection. Chondroitin sulfate proteoglycans (CSPGs) are classified as another major type of proteoglycans. Here, we examined the effect of four types of chondroitin sulfate (CS) on HTLV-1 infection. Accordingly, a human T cell line, MOLT-4, was inoculated with cell-free HTLV-1 in the presence or absence of soluble CS, and the synthesis of reverse-transcribed HTLV-1 DNA within cells 20 h after inoculation was detected using polymerase chain reaction (PCR). Among the four types of CS (A, C, D, and E), the E type (CSE), which was derived from the squid cartilage, exhibited anti-HTLV-1 activity. Furthermore, we observed that CSE directly interacted with recombinant HTLV-1 envelope (Env) proteins and inhibited the binding of HTLV-1 virions to MOLT-4 cells, indicating that the interaction between Env and CSE plays a significant role in its anti-HTLV-1 activity. In addition, CSE inhibited syncytium formation that was induced by HTLV-1-producing cells. When CSE was mixed with the synthetic fusion inhibitor peptide corresponding to the ectodomain of the Env transmembrane subunit (TM) gp21, the HTLV-1 infection was further inhibited when compared with the inhibitory effect of each compound alone. Thus, further elucidation of the in vitro antiviral mechanism of CSE shown in this study will lead to the development of CSE-like molecules for the entry inhibition of HTLV-1.

Trafficking Inhibition of Bruceanol B as a Radical-Producing Antibiotic

Bruceanol B, isolated from a soil microbe strain DS4, generated oxygen radicals in Bacillus subtilis lysates. Bruceanol B inhibited the trafficking of viral glycoprotein in virus-infected baby hamster kidney (BHK) cells. Bruceanol B also effectively inhibited syncytium formation in a dosedependent manner. However, glycoprotein synthesis was not affected by the compound. Results indicate that bruceanol B generating oxygen radical has inhibitory activity in the trafficking of viral glycoprotein of BHK cell.

Anti-bacterial and Anti-viral Activities of Extracts from Terminalia chebula Barks

Effects of methanol extract of Terminalia chebula on antibacterial activity and the generation of superoxide radical in Bacillus subtilis, as well as on syncytium formation and cytopathic activity in virus-infected baby hamster kidney cells were examined. The extract effectively inhibited syncytium formation in a concentration-dependent manner, and infectious virus production was markedly reduced. However, glycoprotein synthesis was not affected. These results collectively indicate that methanol extract of T. chebula potentially inhibit glycosylation by acting as a suppressor of intracellular glycosylation trafficking.

Anti-bacterial and Anti-viral Activity of Extracts from Paeonia lactiflora Roots

Methanol extracts of Paeonia lactiflora roots (Radix Paeaniae Lactiflora) had antibacterial activity against Bacillus subtilis. These extracts generated superoxide radicals in the B. subtilis lysate. However, the radicals were strongly detoxified by the addition of superoxide dismutase, an indication that superoxide radicals are important in the antibacterial actions of the extracts. The root extracts also showed a pivotal inhibition role in trafficking of viral glycoprotein in virusinfected baby hamster kidney (BHK) cells. The methanol extract effectively inhibited syncytium formation in a concentration-dependent, and it did not affect glycoprotein synthesis. These results suggest that oxygen radical affect the transport process of viral glycoprotein without its synthesis.

Mutations in the Stalk Region of the Measles Virus Hemagglutinin Inhibit Syncytium Formation but Not Virus Entry

Measles virus (MV) entry requires at least 2 viral proteins, the hemagglutinin (H) and fusion (F) proteins. We describe the rescue and characterization of a measles virus with a specific mutation in the stalk region of H (I98A) that is able to bind normally to cells but infects at a lower rate than the wild type due to a reduction in fusion triggering. The mutant H protein binds to F more avidly than the parent H protein does, and the corresponding virus is more sensitive to inhibition by fusion-inhibitory peptide. We show that after binding of MV to its receptor, H-F dissociation is required for productive infection.

Microvirin, a Novel α(1,2)-Mannose-specific Lectin Isolated from Microcystis aeruginosa, Has Anti-HIV-1 Activity Comparable with That of Cyanovirin-N but a Much Higher Safety Profile

Microvirin (MVN), a recently isolated lectin from the cyanobacterium Microcystis aeruginosa PCC7806, shares 33% identity with the potent anti-human immunodeficiency virus (HIV) protein cyanovirin-N (CV-N) isolated from Nostoc ellipsosporum, and both lectins bind to similar carbohydrate structures. MVN is able to inhibit infection by a wide variety of HIV-1 laboratory-adapted strains and clinical isolates of different tropisms and subtypes in peripheral blood mononuclear cells. MVN also inhibits syncytium formation between persistently HIV-1-infected T cells and uninfected CD4(+) T cells and inhibits DC-SIGN-mediated HIV-1 binding and transmission to CD4(+) T cells. Long term passaging of HIV-1 exposed to dose-escalating concentrations of MVN resulted in the selection of a mutant virus with four deleted high mannose-type glycans in the envelope gp120. The MVN-resistant virus was still highly sensitive to various other carbohydrate binding lectins (e.g. CV-N, HHA, GNA, and UDA) but not anymore to the carbohydrate-specific 2G12 monoclonal antibody. Importantly, MVN is more than 50-fold less cytotoxic than CV-N. Also in sharp contrast to CV-N, MVN did not increase the level of the activation markers CD25, CD69, and HLA-DR in CD4(+) T lymphocytes, and subsequently, MVN did not enhance viral replication in pretreated peripheral blood mononuclear cells. Therefore, MVN may qualify as a useful lectin for potential microbicidal use based on its broad and potent antiviral activity and virtual lack of any stimulatory properties and cellular toxicity.

ChemInform Abstract: A New Sulfated β-Galactan from Clams with Anti-HIV Activity.

A new polysaccharide composed of galactan sulfate with a β-(1→3)-glycosidic linkage has been isolated from the marine clam species Meretrix petechialis. The polysaccharide was homogeneous in its composition containing d-galactose. The glycosidic linkage was examined by 2D DQF-COSY and 2D NOESY spectroscopy. The coupling constant of anomeric proton was 7.8 Hz, suggesting a β-galacto configuration. The downfield shift of H-2 of galactose residue demonstrated the presence of 2-O-sulfonate group. TQF-COSY confirmed that the C-6 position was substituted with a sulfonate group. The anti-HIV activity of the polysaccharides has been evaluated by the inhibition of syncytia formation. The fusion index and percentage fusion inhibition of sulfated galactan were 0.34 and 56% at 200 μg/mL.