RESUMO
Canine distemper virus (CDV) belongs to morbillivirus, including measles virus (MeV) and rinderpest virus, which causes serious immunological and neurological disorders in carnivores, including dogs and rhesus monkeys, as recently reported, but their vaccines are highly effective. The attachment glycoprotein hemagglutinin (CDV-H) at the CDV surface utilizes signaling lymphocyte activation molecule (SLAM) and Nectin-4 (also called poliovirus-receptor-like-4; PVRL4) as entry receptors. Although fusion models have been proposed, the molecular mechanism of morbillivirus fusion entry is poorly understood. Here, we determined the crystal structure of the globular head domain of CDV-H vaccine strain at 3.2 Å resolution, revealing that CDV-H exhibits a highly tilted homodimeric form with a six-bladed ß-propeller fold. While the predicted Nectin-4-binding site is well conserved with that of MeV-H, that of SLAM is similar but partially different, which is expected to contribute to host specificity. Five N-linked sugars covered a broad area of the CDV-H surface to expose receptor-binding sites only, supporting the effective production of neutralizing antibodies. These features are common to MeV-H, although the glycosylation sites are completely different. Furthermore, real-time observation using high-speed atomic force microscopy revealed highly mobile features of the CDV-H dimeric head via the connector region. These results suggest that sugar-shielded tilted homodimeric structure and dynamic conformational changes are common characteristics of morbilliviruses and ensure effective fusion entry and vaccination.
Assuntos
Vírus da Cinomose Canina , Polissacarídeos , Internalização do Vírus , Vírus da Cinomose Canina/química , Vírus da Cinomose Canina/imunologia , Animais , Polissacarídeos/química , Polissacarídeos/metabolismo , Cães , Cinomose/virologia , Cinomose/prevenção & controle , Cristalografia por Raios X , Hemaglutininas Virais/química , Hemaglutininas Virais/metabolismo , Multimerização Proteica , Vacinação , Conformação Proteica , Vacinas Virais/imunologia , Vacinas Virais/química , Receptores Virais/metabolismo , Receptores Virais/química , Modelos MolecularesRESUMO
The geographical distribution of plant resources is of great significance for studying the origin, distribution, and evolution of species. Climate and geographical factors help shape the distribution of plant species. Dendrobium is a commonly used traditional medicine and a precious economic crop in China. Owing to the over-exploitation and increasing medicinal demand of Dendrobium species plants, systematic investigation of the geographical distribution of the plants and analysis of their potential distribution under climate change are important for protecting Dendrobium plants. We adopted DIVA-GIS to analyze the georeferenced records of 76 species of the Dendrobium species collected from 2166 herbarium records. We analyzed the eco-geographical distribution and species richness of the genus Dendrobium to simulate the distribution of current and future scenarios using MaxEnt. The results revealed the distribution of Dendrobium in 30 provinces of China, with species abundance in Yunnan, Guangxi, Guangdong, and Hainan. Our model identified the following bioclimatic variables: precipitation in the driest months and the warmest seasons, isothermality, and range of annual temperature. Among them, annual precipitation is the most crucial bioclimatic variable affecting the distribution of 16 selected Dendrobium species. The change of climate in the future will lead to an increase in habitat suitability for some Dendrobium species as follows: D. officinal 2.12%, D. hancockii by 6.00%, D. hercoglossum by 8.25%, D. devonianum by 7.71%, D. henryi by 9.40%, and D. hainanense by 13.70%. By contrast, habitat suitability will dramatically decrease for other Dendrobium species: D. chrysotoxum by 0.89%, D. chrysanthum by 12.68%, D. fimbriatum by 5.07%, D. aduncum by 11.44%, D. densiflorum by 18.47%, D. aphyllum by 8.05%, D. loddigesii by 16.45%, D. nobile by 5.41%, D. falconeri by 8.73%, and D. moniliforme by 10.61%. The reduction of these species will be detrimental to the medicinal and economic value of the genus Dendrobium. Therefore, targeted development and reasonable management strategies should be adopted to conserve these valuable resources.
Assuntos
Mudança Climática , Dendrobium , China , Ecossistema , TemperaturaRESUMO
The measles virus (MV) is a major cause of childhood morbidity and mortality worldwide. We previously established a mouse monoclonal antibody, 2F4, which shows high neutralizing titers against eight different genotypes of MV. However, the molecular basis for the neutralizing activity of the 2F4 antibody remains incompletely understood. Here, we have evaluated the binding characteristics of a Fab fragment of the 2F4 antibody. Using the MV infectious assay, we demonstrated that 2F4 Fab inhibits viral entry via either of two cellular receptors, SLAM and Nectin4. Surface plasmon resonance (SPR) analysis of recombinant proteins indicated that 2F4 Fab interacts with MV hemagglutinin (MV-H) with a KD value at the nm level. Furthermore, we designed a single-chain Fv fragment of 2F4 antibody as another potential biopharmaceutical to target measles. The stable 2F4 scFv was successfully prepared by the refolding method and shown to interact with MV-H at the µm level. Like 2F4 Fab, scFv inhibited receptor binding and viral entry. This indicates that 2F4 mAb uses the receptor-binding site and/or a neighboring region as an epitope with high affinity. These results provide insight into the neutralizing activity and potential therapeutic use of antibody fragments for MV infection.
Assuntos
Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Fragmentos Fab das Imunoglobulinas/imunologia , Vírus do Sarampo/imunologia , Sarampo/imunologia , Anticorpos de Cadeia Única/imunologia , Proteínas Virais/imunologia , Anticorpos Neutralizantes/biossíntese , Anticorpos Neutralizantes/genética , Anticorpos Antivirais/biossíntese , Anticorpos Antivirais/genética , Epitopos/imunologia , Células HEK293 , Humanos , Fragmentos Fab das Imunoglobulinas/biossíntese , Fragmentos Fab das Imunoglobulinas/genética , Sarampo/virologia , Nectinas/antagonistas & inibidores , Nectinas/imunologia , Nectinas/metabolismo , Ligação Proteica , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária/antagonistas & inibidores , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária/imunologia , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária/metabolismo , Anticorpos de Cadeia Única/biossíntese , Anticorpos de Cadeia Única/genética , Internalização do VírusRESUMO
The genus Morbillivirus includes measles virus, canine distemper virus and rinderpest virus. These are highly contagious and exhibit high mortality. These viruses have the attachment glycoprotein, hemagglutinin (H), at the virus surface, which bind to signaling lymphocyte activation molecule (SLAM) and Nectin 4 as receptors for the entry. However, the molecular mechanism for this entry has been limitedly understood. Here we summarize the current topics, (1) newly identified receptor, Nectin 4, (2) crystal structures of H-receptor complexes and (3) detail biochemical studies of the H-F communication for the entry. These provide insight on the mechanism of morbillivirus entry event and furthermore drug developments.
Assuntos
Infecções por Morbillivirus/virologia , Morbillivirus/genética , Morbillivirus/patogenicidade , Animais , Antígenos CD/química , Antígenos CD/metabolismo , Moléculas de Adesão Celular/metabolismo , Cristalização , Desenho de Fármacos , Hemaglutininas Virais/química , Hemaglutininas Virais/metabolismo , Humanos , Fusão de Membrana , Infecções por Morbillivirus/genética , Ligação Proteica , Estrutura Quaternária de Proteína , Receptores de Superfície Celular/química , Receptores de Superfície Celular/metabolismo , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/metabolismo , Vacinas ViraisRESUMO
Recent outbreaks in monkeys have proven that canine distemper virus (CDV) causes diseases in a wide range of mammals. CDV uses SLAM and nectin4 as receptors to replicate in susceptible animals. Here, we show that human nectin4, but not human SLAM, is fully functional as a CDV receptor. The CDV Ac96I strain hardly replicated in nectin4-expressing human epithelial NCI-H358 cells, but readily adapted to grow in them. Unsurprisingly, no amino acid change in the H protein was required for the adaptation. The original Ac96I strain possessed a truncated C protein, and a subpopulation possessing the intact C protein was selected after growth in NCI-H358 cells. Other CDV strains possessing the intact C protein showed significantly higher growth abilities in NCI-H358 cells than the Ac96I strain with the truncated C protein. These findings suggest that the C protein is functional in human epithelial cells and critical for CDV replication in them.