Novel bovine viral diarrhea virus (BVDV) virus-like particle vaccine candidates presenting the E2 protein using the SpyTag/SpyCatcher system induce a robust neutralizing antibody response in mice.

Bovine viral diarrhea virus (BVDV) is a pathogen of commercial consequence in cattle. Although many modified live and killed vaccines are commercially available, their drawbacks precipitate the need for new effective vaccines. Virus-like particles (VLPs) are a safe and powerful technology used in several human and veterinary vaccines; however, it is difficult to produce large amounts of BVDV VLPs. In this study, we generated red-spotted grouper nervous necrosis virus (RGNNV) VLPs presenting the BVDV E2 protein (domain I to IIIb) of the Nose (BVDV-1) or KZ-91-CP (BVDV-2) strain by exploiting SpyTag/SpyCatcher technology. Mice immunized twice with 30 µg of RGNNV VLPs conjugated with 10 µg of E2 proteins of the Nose or KZ-91-CP strain with a 14-day interval elicited high (1:512,000 to 1:1,024,000) and moderate (1:25,600 to 1:102,400) IgG titers against E2 proteins of homologous and heterologous strains, respectively. In addition, this prime-boost regimen induced strong (1:800 to 1:3,200) and weak (~1:10) neutralization titers against homologous and heterologous BVDV strains, respectively. Our results indicate that conjugation of the E2 protein to RGNNV VLPs strongly enhances the antigenicity of the E2 protein and that RGNNV VLPs presenting the E2 protein are promising BVDV vaccine candidates.

Generation of a photocontrollable recombinant bovine parainfluenza virus type 3.

Bovine parainfluenza virus type 3 (BPIV3) is a promising vaccine vector against various respiratory virus infections, including the human PIV3, respiratory syncytial virus, and severe acute respiratory syndrome-coronavirus 2 infections. In this study, we combined the Magnet system and reverse genetic approach to generate photocontrollable BPIV3. An optically controllable Magnet gene was inserted into the H2 region of the BPIV3 large protein gene, which encodes an RNA-dependent RNA polymerase. The generated photocontrollable BPIV3 grew in specific regions of the cell sheet only when illuminated with blue light, suggesting that spatiotemporal control can aid in safe clinical applications of BPIV3.

Rapid Serotyping of Salmonella Isolates Based on Single Nucleotide Polymorphism-Like Sequence Profiles of a Salmonella-Specific Gene.

Although serotyping is the most important method of identification of taxonomy in Salmonella, conventional serotype determination with a complete set of antisera is time consuming and laborious. Recently, rapid serotyping procedures with polymerase chain reaction (PCR) have been developed. In this study, we established a novel PCR-based rapid serotyping method that employs a unique target gene. Alignment study of Salmonella-specific gene (Salmonella enterotoxin [stn]) revealed a correlation between the stn gene sequence and the serotype of the organism. In 750 bp of stn gene, 55 nucleotides indicated single nucleotide polymorphism (SNP)-like polymorphism, and the correlation between the SNP-like polymorphism and the serotype of the organism suggests that SNP-like sequences in stn gene can serve as an index for serotyping. To develop a rapid serotyping method based on the SNP-like polymorphism, we selected serotype-associated 12 SNP-like sites in the stn gene and established a method based on high-resolution melting (HRM) and PCR, which identifies nucleotides at SNP-like sites within 1.5 h. This newly established rapid serotyping procedure (stn-HRM) could identify nine serotypes, including the frequently isolated serovar Enteritidis. These nine serotypes cover 64.3% of cases of Salmonella, as reported by the World Health Organization/Global Foodborne Infection Network (WHO/GFN) Country Databank from 2001 to 2010. In this study, we employed a unique target gene, stn, which is completely independent of the genes that were targeted in previously reported rapid serotyping procedures. Therefore, the results obtained by our newly developed stn-HRM procedure are independent of the results obtained by other procedures. Besides, stn-HRM can ensure accurate identification of the bacterial species as stn is a Salmonella-specific gene. It is expected that the combination of newly constructed stn-HRM and previously reported procedures could further improve the credibility of Salmonella isolate serotyping.

Efficacy and safety of sodium RISedronate for glucocorticoid-induced OsTeoporosis with rheumaTOid arthritis (RISOTTO study): A multicentre, double-blind, randomized, placebo-controlled trial.

OBJECTIVE: No evidence has shown the efficacy of Sodium Risedronate (Risedronate) for glucocorticoid-induced osteoporosis (GIO) in patients with Rheumatoid arthritis (RA). The aim of this study was to explore the effectiveness and safety of Risedronate for GIO complicated with RA. METHODS: This was a six-month randomized, double-blind, placebo-controlled trial of 95 patients with GIO complicated with RA from 19 centers. The primary endpoint was the change from baseline in lumbar spine bone mineral density (L-BMD). Secondary endpoints included changes in femoral neck and total hip BMD and bone turnover markers, as well as rheumatoid arthritis Disease Activity Score with 28-joint counts. Incident of non-traumatic spine fractures and adverse events were tracked as safety endpoints. RESULTS: Increase in L-BMD was significantly greater in the Risedronate group compared to the Placebo group (Risedronate: 3.49% [95% CI: 1.92-5.05] vs Placebo: 0.12% [95% CI: -2.07 to 2.30], p < .0001). No significant difference was found in the femoral neck and total hip BMD. Although adverse events were observed in 28 patients, none were considered serious. Non-traumatic vertebral fractures were identified in 10 patients. CONCLUSION: Risedronate was effective in increasing L-BMD and was well tolerated in patients with GIO complicated with RA.

Influence of Intermittent Cold Stimulations on CREB and Its Targeting Genes in Muscle: Investigations into Molecular Mechanisms of Local Cryotherapy.

Local cryotherapy is widely used as a treatment for sports-related skeletal muscle injuries. The molecular mechanisms are unknown. To clarify these mechanisms, we applied one to three 15-min cold stimulations at 4 °C to various cell lines (in vitro), the tibialis anterior (TA) muscle (ex vivo), and mouse limbs (in vivo). In the in vitro assay, cyclic AMP (cAMP) response element binding protein 1 (CREB1) was markedly phosphorylated (p-CREB1), and the CREB-binding protein (CBP) was recruited to p-CREB-1 in response to two or three cold stimulations. In a reporter assay with the cAMP-responsive element, the signals significantly increased after two to three cold stimulations at 4 °C. In the ex vivo study, CREB-targeting genes were significantly upregulated following two or three cold stimulations. The in vivo experiment disclosed that cold stimulation of a mouse limb for 9 days significantly increased mitochondrial DNA copy number and upregulated genes involved in mitochondrial biogenesis. The results suggest that local cryotherapy increases CREB transcription and upregulates CREB-targeting genes, in a manner dependent on cold stimulation frequency and duration. This information will inform further investigations into local cryotherapy as a treatment for sports-related skeletal muscle trauma.

Trisaccharide containing α2,3-linked sialic acid is a receptor for mumps virus.

Mumps virus (MuV) remains an important pathogen worldwide, causing epidemic parotitis, orchitis, meningitis, and encephalitis. Here we show that MuV preferentially uses a trisaccharide containing α2,3-linked sialic acid in unbranched sugar chains as a receptor. Crystal structures of the MuV attachment protein hemagglutinin-neuraminidase (MuV-HN) alone and in complex with the α2,3-sialylated trisaccharide revealed that in addition to the interaction between the MuV-HN active site residues and sialic acid, other residues, including an aromatic residue, stabilize the third sugar of the trisaccharide. The importance of the aromatic residue and the third sugar in the MuV-HN-receptor interaction was confirmed by computational energy calculations, isothermal titration calorimetry studies, and glycan-binding assays. Furthermore, MuV-HN was found to bind more efficiently to unbranched α2,3-sialylated sugar chains compared with branched ones. Importantly, the strategically located aromatic residue is conserved among the HN proteins of sialic acid-using paramyxoviruses, and alanine substitution compromised their ability to support cell-cell fusion. These results suggest that not only the terminal sialic acid but also the adjacent sugar moiety contribute to receptor function for mumps and these paramyxoviruses. The distribution of structurally different sialylated glycans in tissues and organs may explain in part MuV's distinct tropism to glandular tissues and the central nervous system. In the crystal structure, the epitopes for neutralizing antibodies are located around the α-helices of MuV-HN that are not well conserved in amino acid sequences among different genotypes of MuV. This may explain the fact that MuV reinfection sometimes occurs.

A single L288I substitution in the fusion protein of bovine parainfluenza virus type 3 enhances virus growth in semi-suitable cell lines.

The bovine parainfluenza virus type 3 BN-CE vaccine strain was obtained by serial passage of the BN-1 strain in chicken embryonic fibroblasts (CEF). We previously identified a substitution (L288I) in the fusion (F) protein between the two strains. To examine the effect of the substitution on CEF adaptation and attenuation, we generated a recombinant BN-1 strain with the L288I substitution in the F protein (FL288I-EGFP). FL288I-EGFP replicated more efficiently than a recombinant BN-1 strain (wt-EGFP) in semi-suitable cell lines, suggesting that the L288I substitution was established in the BN-1 strain during the process of adaptation in CEF.

Differential induction of type I interferons in macaques by wild-type measles virus alone or with the hemagglutinin protein of the Edmonston vaccine strain.

Measles vaccines are highly effective and safe; however, the mechanism(s) underlying their attenuation has not been well understood. In this study, type I IFNs (IFN-α and IFN-ß) induction in macaques infected with measles virus (MV) strains was examined. Type I IFNs were not induced in macaques infected with wild-type MV. However, IFN-α was sharply induced in most macaques infected with recombinant wild-type MV bearing the hemagglutinin (H) protein of the Edmonston vaccine strain. These results indicate that the H protein of MV vaccine strains may have a role in MV attenuation.

Influenza A virus hemagglutinin and neuraminidase mutually accelerate their apical targeting through clustering of lipid rafts.

UNLABELLED: In polarized epithelial cells, influenza A virus hemagglutinin (HA) and neuraminidase (NA) are intrinsically associated with lipid rafts and target the apical plasma membrane for viral assembly and budding. Previous studies have indicated that the transmembrane domain (TMD) and cytoplasmic tail (CT) of HA and NA are required for association with lipid rafts, but the raft dependencies of their apical targeting are controversial. Here, we show that coexpression of HA with NA accelerated their apical targeting through accumulation in lipid rafts. HA was targeted to the apical plasma membrane even when expressed alone, but the kinetics was much slower than that of HA in infected cells. Coexpression experiments revealed that apical targeting of HA and NA was accelerated by their coexpression. The apical targeting of HA was also accelerated by coexpression with M1 but not M2. The mutations in the outer leaflet of the TMD and the deletion of the CT in HA and NA that reduced their association with lipid rafts abolished the acceleration of their apical transport, indicating that the lipid raft association is essential for efficient apical trafficking of HA and NA. An in situ proximity ligation assay (PLA) revealed that HA and NA were accumulated and clustered in the cytoplasmic compartments only when both were associated with lipid rafts. Analysis with mutant viruses containing nonraft HA/NA confirmed these findings. We further analyzed lipid raft markers by in situ PLA and suggest a possible mechanism of the accelerated apical transport of HA and NA via clustering of lipid rafts. IMPORTANCE: Lipid rafts serve as sites for viral entry, particle assembly, and budding, leading to efficient viral replication. The influenza A virus utilizes lipid rafts for apical plasma membrane targeting and particle budding. The hemagglutinin (HA) and neuraminidase (NA) of influenza virus, key players for particle assembly, contain determinants for apical sorting and lipid raft association. However, it remains to be elucidated how lipid rafts contribute to the apical trafficking and budding. We investigated the relation of lipid raft association of HA and NA to the efficiency of apical trafficking. We show that coexpression of HA and NA induces their accumulation in lipid rafts and accelerates their apical targeting, and we suggest that the accelerated apical transport likely occurs by clustering of lipid rafts at the TGN. This finding provides the first evidence that two different raft-associated viral proteins induce lipid raft clustering, thereby accelerating apical trafficking of the viral proteins.

Unexpected radiation laryngeal necrosis after carbon ion therapy using conventional dose fractionation for laryngeal cancer.

Carbon ion therapy is a type of radiotherapy that can deliver high-dose radiation to a tumor while minimizing the dose delivered to organs at risk. Moreover, carbon ions are classified as high linear energy transfer radiation and are expected to be effective for even photon-resistant tumors. A 73-year-old man with glottic squamous cell carcinoma, T3N0M0, refused laryngectomy and received carbon ion therapy of 70 Gy (relative biological effectiveness) in 35 fractions. Three months after the therapy, the patient had an upper airway inflammation, and then laryngeal edema and pain occurred. Five months after the therapy, the airway stenosis was severe and computed tomography showed lack of the left arytenoid cartilage and exacerbation of laryngeal necrosis. Despite the treatment, 5 and a half months after the therapy, the laryngeal edema and necrosis had become even worse and the surrounding mucosa was edematous and pale. Six months after the therapy, pharyngolaryngoesophagectomy and reconstruction with free jejunal autograft were performed. The surgical specimen pathologically showed massive necrosis and no residual tumor. Three years after the carbon ion therapy, he is alive without recurrence. The first reported laryngeal squamous cell carcinoma case treated with carbon ion therapy resulted in an unexpected radiation laryngeal necrosis. Tissue damage caused by carbon ion therapy may be difficult to repair even for radioresistant cartilage; therefore, hollow organs reinforced by cartilage, such as the larynx, may be vulnerable to carbon ion therapy. Caution should be exercised when treating tumors in or adjacent to such organs with carbon ion therapy.

Carbocisteine reduces virus-induced pulmonary inflammation in mice exposed to cigarette smoke.

Carbocisteine (S-CMC) inhibits viral infection and prevents acute exacerbation of chronic obstructive pulmonary disease. We recently demonstrated the protective effects of NF-E2-related factor (Nrf) 2 against influenza virus (FluV)-induced pulmonary inflammation in mice exposed to cigarette smoke (CS). In our current study, we investigated the effects of S-CMC on Nrf2 activation in cultured macrophages, and in mice infected with influenza after exposure to CS. Nuclear translocation of Nrf2 and the expression of Nrf2-targeted antioxidant genes, such as heavy and light subunits of γ glutamyl cysteine synthetase and heme oxigenase-1, were enhanced in a dose-dependent manner after treatment with S-CMC in peritoneal and alveolar macrophages of wild-type mice, but not in those of Nrf2-deficient mice. Nuclear translocation of Nrf2 in macrophages was inhibited by the phosphatidylinositol 3-kinase inhibitor, LY294002. Phosphorylated Akt, Nrf2, and heme oxigenase-1 were induced in the alveolar macrophages of the lungs in wild-type mice after S-CMC administration. The extent of oxidative stress, inflammatory cell infiltration, pulmonary edema, and goblet cell hyperplasia was suppressed by S-CMC administration in the lungs of wild-type mice after exposure to both CS and FluV. Our findings suggest that S-CMC reduces pulmonary inflammation and mucus overproduction in mice exposed to CS after infection with FluV via the activation of Nrf2.

Mode of swine hepatitis E virus infection and replication in primary human hepatocytes.

The aim of this study was to investigate the infection and replication of swine-derived hepatitis E virus (HEV) in primary cultured human hepatocytes (PHCs). Hepatocytes were cultured from the resected normal livers of patients with metastatic tumours. These cultured hepatocytes were infected with swine-derived genotype 3 or 4 HEV. Viral replication was monitored using reverse transcriptase-quantitative PCR. The amount of HEV RNA increased in the culture media and cells following infection. Immunofluorescence staining implied that the spread of HEV infection in hepatocytes was attributed mainly to cell-to-cell transmission via the cell membrane. The sequences of the inoculated and propagated HEV were determined to examine whether sequence variation occurred during infection. Sequence analysis showed that there were no differences between inoculated and propagated HEV, demonstrating that in vitro infection and replication of swine HEV in PHCs occurred without sequence variation.

F-actin modulates measles virus cell-cell fusion and assembly by altering the interaction between the matrix protein and the cytoplasmic tail of hemagglutinin.

Actin filament (F-actin) is believed to be involved in measles virus (MV) assembly as a cellular factor, but the precise roles remain unknown. Here we show that Phe at position 50 of the MV matrix (M) protein is important for its association with F-actin, through which the function of the M protein is regulated. In plasmid-expressed or MV-infected cells, a coimmunoprecipitation study revealed that the wild-type M (M-WT) protein associated strongly with F-actin but only weakly with the cytoplasmic tail of the hemagglutinin (H) protein. Since the F50P mutation allowed the M protein the enhanced interaction with the H protein in return for the sharply declined association with F-actin, the mutant M (M-F50P) protein strongly inhibited MV cell-cell fusion and promoted the uptake of the H protein into virus particles. The abundantly incorporated H protein resulted in the increase in infectivity of the F50P virus, although the virus contained a level of genome RNA equal to that of the WT virus. When the structure of F-actin was disrupted with cytochalasin D, the M-WT protein liberated from F-actin interacted with the H protein as tightly as the M-F50P protein, suppressing cell-cell fusion and promoting virus assembly comparably efficiently as the M-F50P protein. The cell-cell fusion activity of the WT virus appeared to be upheld by F-actin, which prevents the M protein interaction with the H protein. Our results indicate that F-actin in association with the M protein alters the interaction between the M and H proteins, thereby modulating MV cell-cell fusion and assembly.

α-Selective ribofuranosylation of alcohols with ribofuranosyl iodides and triphenylphosphine oxide.

Ribofuranosylation of a variety of alcohols with ribofuranosyl iodides in the presence of a base and triphenylphosphine oxide afforded the corresponding α-ribofuranosides with diastereoselectivities ≥ 99:1. This reaction can be carried out under mildly basic conditions and is thus compatible with acid-sensitive functional groups.

Wild-type measles virus with the hemagglutinin protein of the edmonston vaccine strain retains wild-type tropism in macaques.

A major difference between vaccine and wild-type strains of measles virus (MV) in vitro is the wider cell specificity of vaccine strains, resulting from the receptor usage of the hemagglutinin (H) protein. Wild-type H proteins recognize the signaling lymphocyte activation molecule (SLAM) (CD150), which is expressed on certain cells of the immune system, whereas vaccine H proteins recognize CD46, which is ubiquitously expressed on all nucleated human and monkey cells, in addition to SLAM. To examine the effect of the H protein on the tropism and attenuation of MV, we generated enhanced green fluorescent protein (EGFP)-expressing recombinant wild-type MV strains bearing the Edmonston vaccine H protein (MV-EdH) and compared them to EGFP-expressing wild-type MV strains. In vitro, MV-EdH replicated in SLAM(+) as well as CD46(+) cells, including primary cell cultures from cynomolgus monkey tissues, whereas the wild-type MV replicated only in SLAM(+) cells. However, in macaques, both wild-type MV and MV-EdH strains infected lymphoid and respiratory organs, and widespread infection of MV-EdH was not observed. Flow cytometric analysis indicated that SLAM(+) lymphocyte cells were infected preferentially with both strains. Interestingly, EGFP expression of MV-EdH in tissues and lymphocytes was significantly weaker than that of the wild-type MV. Taken together, these results indicate that the CD46-binding activity of the vaccine H protein is important for determining the cell specificity of MV in vitro but not the tropism in vivo. They also suggest that the vaccine H protein attenuates MV growth in vivo.

Role of Nrf2 in host defense against influenza virus in cigarette smoke-exposed mice.

Influenza virus is a common respiratory tract viral infection. Although influenza can be fatal in patients with chronic pulmonary diseases such as chronic obstructive pulmonary disease, its pathogenesis is not fully understood. The Nrf2-mediated antioxidant system is essential to protect the lungs from oxidative injury and inflammation. In the present study, we investigated the role of Nrf2 in protection against influenza virus-induced pulmonary inflammation after cigarette smoke exposure with both in vitro and in vivo approaches. For in vitro analyses, peritoneal macrophages isolated from wild-type and Nrf2-deficient mice were treated with poly(I:C) and/or cigarette smoke extract. For in vivo analysis, these mice were infected with influenza A virus with or without exposure to cigarette smoke. In Nrf2-deficient macrophages, NF-κB activation and the induction of its target inflammatory genes were enhanced after costimulation with cigarette smoke extract and poly(I:C) compared with wild-type macrophages. The induction of antioxidant genes was observed for the lungs of wild-type mice but not those of Nrf2-deficient mice after cigarette smoke exposure. Cigarette smoke-exposed Nrf2-deficient mice showed higher rates of mortality than did wild-type mice after influenza virus infection, with enhanced peribronchial inflammation, lung permeability damage, and mucus hypersecretion. Lung oxidant levels and NF-κB-mediated inflammatory gene expression in the lungs were also enhanced in Nrf2-deficient mice. Our data indicate that the antioxidant pathway controlled by Nrf2 is pivotal for protection against the development of influenza virus-induced pulmonary inflammation and injury under oxidative conditions.

RSOsPR10 expression in response to environmental stresses is regulated antagonistically by jasmonate/ethylene and salicylic acid signaling pathways in rice roots.

Plant roots play important roles not only in the absorption of water and nutrients, but also in stress tolerance. Previously, we identified RSOsPR10 as a root-specific pathogenesis-related (PR) protein induced by drought and salt treatments in rice. Transcripts and proteins of RSOsPR10 were strongly induced by jasmonate (JA) and the ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC), while salicylic acid (SA) almost completely suppressed these inductions. Immunohistochemical analyses showed that RSOsPR10 strongly accumulated in cortex cells surrounding the vascular system of roots, and this accumulation was also suppressed when SA was applied simultaneously with stress or hormone treatments. In the JA-deficient mutant hebiba, RSOsPR10 expression was up-regulated by NaCl, wounding, drought and exogenous application of JA. This suggested the involvement of a signal transduction pathway that integrates JA and ET signals in plant defense responses. Expression of OsERF1, a transcription factor in the JA/ET pathway, was induced earlier than that of RSOsPR10 after salt, JA and ACC treatments. Simultaneous SA treatment strongly inhibited the induction of RSOsPR10 expression and, to a lesser extent, induction of OsERF1 expression. These results suggest that JA/ET and SA pathways function in the stress-responsive induction of RSOsPR10, and that OsERF1 may be one of the transcriptional factors in the JA/ET pathway.

The F gene of the Osaka-2 strain of measles virus derived from a case of subacute sclerosing panencephalitis is a major determinant of neurovirulence.

Measles virus (MV) is the causative agent for acute measles and subacute sclerosing panencephalitis (SSPE). Although numerous mutations have been found in the MV genome of SSPE strains, the mutations responsible for the neurovirulence have not been determined. We previously reported that the SSPE Osaka-2 strain but not the wild-type strains of MV induced acute encephalopathy when they were inoculated intracerebrally into 3-week-old hamsters. The recombinant MV system was adapted for the current study to identify the gene(s) responsible for neurovirulence in our hamster model. Recombinant viruses that contained envelope-associated genes from the Osaka-2 strain were generated on the IC323 wild-type MV background. The recombinant virus containing the M gene alone did not induce neurological disease, whereas the H gene partially contributed to neurovirulence. In sharp contrast, the recombinant virus containing the F gene alone induced lethal encephalopathy. This phenotype was related to the ability of the F protein to induce syncytium formation in Vero cells. Further study indicated that a single T461I substitution in the F protein was sufficient to transform the nonneuropathogenic wild-type MV into a lethal virus for hamsters.

Remarkable similarity in genome nucleotide sequences between the Schwarz FF-8 and AIK-C measles virus vaccine strains and apparent nucleotide differences in the phosphoprotein gene.

The Schwarz FF-8 (FF-8) and AIK-C measles virus vaccine strains are currently used for vaccination in Japan. Here, the complete genome nucleotide sequence of the FF-8 strain has been determined and its genome sequence found to be remarkably similar to that of the AIK-C strain. These two strains are differentiated only by two nucleotide differences in the phosphoprotein gene. Since the FF-8 strain does not possess the amino acid substitutions in the phospho- and fusion proteins which are responsible for the temperature-sensitivity and small syncytium formation phenotypes of the AIK-C strain, respectively, other unidentified common mechanisms likely attenuate both the FF-8 and AIK-C strains.

Amino- and carboxyl-terminal ends of the bovine parainfluenza virus type 3 matrix protein are important for virion and virus-like particle release.

Paramyxovirus matrix (M) proteins are key drivers of virus particle assembly and budding at the plasma membrane. To identify regions important for the M protein function, we generated a series of deletion mutants of the bovine parainfluenza virus type 3 (BPIV3) M protein. We found that M proteins lacking 10 amino acids in the amino-terminal end (ΔN10) or 4 amino acids in the carboxyl-terminal end (ΔC4) did not support M-deficient BPIV3 virion release and M protein-induced virus-like particle (VLP) release. Both ΔN10 and ΔC4 retained M protein-M protein and M protein-nucleocapsid (N) protein interactions. However, neither was transported to the plasma membrane. Our results indicate that both amino- and carboxyl-terminal ends of the BPIV3 M protein are essential for M protein transport to the plasma membrane, where it facilitates virion and VLP release.