Comparative structure, morphogenesis and biological characteristics of the respiratory syncytial (RS) virus and the pneumonia virus of mice (PVM)

Adapted methods for monitoring influenza virus and respiratory syncytial virus in sludge and wastewater

Wastewater-based surveillance constitutes a valuable methodology for the continuous monitoring of viral circulation, with the capacity to function as an early warning system. It holds particular significance in scenarios where respiratory viruses exhibit overlapping clinical presentations, as occurs with SARS-CoV-2, influenza virus (IV), and respiratory syncytial virus (RSV), and allows seasonal virus outbreaks to be distinguished from COVID-19 peaks. Furthermore, sewage sludge, given it harbors concentrated human waste from a large population, serves as a substantial reservoir for pathogen detection. To effectively integrate wastewater-based epidemiology into infectious disease surveillance, the detection methods employed in wastewater samples must be adapted to the distinct characteristics of sludge matrices. In this study, we adapted and applied protocols for the detection of IV and RSV in sewage sludge, comparing their performance with the results obtained in wastewater. To assess the efficiency of these protocols, sludge and wastewater samples were spiked with IV and RSV RNA, either free or incorporated in lentiviral particles. Samples were concentrated using the aluminum hydroxide adsorption-precipitation method before viral RNA extraction. Absolute virus quantification was carried out by RT-qPCR, including an internal control to monitor potential inhibitory factors. Recovery efficiencies for both free IV and RSV RNA were 60 % in sludge, and 75 % and 71 % respectively in wastewater, whereas the values for IV and RSV RNA in lentiviral particles were 16 % and 10 % in sludge and 21 % and 17 % in wastewater respectively. Additionally, the protocol enabled the quantification of naturally occurring IV and RSV in wastewater and sludge samples collected from two wastewater treatment plants during the winter months, thus affirming the efficacy of the employed methodologies.

Biophysical and flavonoid-binding studies of the G protein ectodomain of group A human respiratory syncytial virus

The human Respiratory Syncytial Virus (hRSV) is the major causative agent of lower respiratory tract diseases in infants, young children and elderly. The membrane protein G is embedded in the viral lipid envelope and plays an adhesion function of the virus to host cells. The present study reports the production of the group A hRSV recombinant G protein ectodomain (edG) and its characterization of secondary structure and thermal unfolding by circular dichroism (CD), as well as the binding investigation of flavonoids quercetin and morin to this protein by fluorescent quenching. CD data reveal that edG is composed mostly of β-structure and its melting temperature is of 325 K. Fluorescence quenching experiments of hRSV edG show that the dissociation constants for the flavonoids binding are micromolar and the binding affinity for the edG/quercetin complex is inversely dependent on rising temperature while is directly dependent for the edG/morin interaction. The thermodynamic parameters suggest that hydrophobic contacts are important for the edG/morin association while van der Waals forces and hydrogen bonds contribute to the stabilization of the edG/quercetin complex. Thus, data reported herein may contribute to the development of new treatment strategies that prevent the viral infection by hRSV.

Evaluation of pneumonia virus of mice as a possible human pathogen

Pneumonia virus of mice (PVM), a relative of human respiratory syncytial virus (RSV), causes respiratory disease in mice. There is serologic evidence suggesting widespread exposure of humans to PVM. To investigate replication in primates, African green monkeys (AGM) and rhesus macaques (n = 4) were inoculated with PVM by the respiratory route. Virus was shed intermittently at low levels by a subset of animals, suggesting poor permissiveness. PVM efficiently replicated in cultured human cells and inhibited the type I interferon (IFN) response in these cells. This suggests that poor replication in nonhuman primates was not due to a general nonpermissiveness of primate cells or poor control of the IFN response. Seroprevalence in humans was examined by screening sera from 30 adults and 17 young children for PVM-neutralizing activity. Sera from a single child (6%) and 40% of adults had low neutralizing activity against PVM, which could be consistent with increasing incidence of exposure following early childhood. There was no cross-reaction of human or AGM sera between RSV and PVM and no cross-protection in the mouse model. In native Western blots, human sera reacted with RSV but not PVM proteins under conditions in which AGM immune sera reacted strongly. Serum reactivity was further evaluated by flow cytometry using unfixed Vero cells infected with PVM or RSV expressing green fluorescent protein (GFP) as a measure of viral gene expression. The reactivity of human sera against RSV-infected cells correlated with GFP expression, whereas reactivity against PVM-infected cells was low and uncorrelated with GFP expression. Thus, PVM specificity was not evident. Our results indicate that the PVM-neutralizing activity of human sera is not due to RSV- or PVM-specific antibodies but may be due to low-affinity, polyreactive natural antibodies of the IgG subclass. The absence of PVM-specific antibodies and restriction in nonhuman primates makes PVM unlikely to be a human pathogen.

Avian and human metapneumovirus

Pneumovirus infection remains a significant problem for both human and veterinary medicine. Both avian pneumovirus (aMPV, Turkey rhinotracheitis virus) and human metapneumovirus (hMPV) are pathogens of birds and humans, which are associated with respiratory tract infections. Based on their different genomic organization and low level of nucleotide (nt) and amino acid (aa) identity with paramyxoviruses in the genus Pneumovirus, aMPV and hMPV have been classified into a new genus referred to as Metapneumovirus. The advancement of our understanding of pneumovirus biology and pathogenesis of pneumovirus disease in specific natural hosts can provide us with strategies for vaccine formulations and combined antiviral and immunomodulatory therapies.

Dynamics of filamentous viral RNPs prior to egress

The final step in the maturation of paramyxoviruses, orthomyxoviruses and viruses of several other families, entails the budding of the viral nucleocapsid through the plasma membrane of the host cell. Many medically important viruses, such as influenza, parainfluenza, respiratory syncytial virus (RSV) and Ebola, can form filamentous particles when budding. Although filamentous virions have been previously studied, details of how viral filaments bud from the plasma membrane remain largely unknown. Using molecular beacon (MB)-fluorescent probes to image the viral genomic RNA (vRNA) of human RSV (hRSV) in live Vero cells, the dynamics of assembled viral filaments was observed to consist of three primary types of motion prior to egress from the plasma membrane: (i) filament projection and rotation, (ii) migration and (iii) non-directed motion. In addition, from information gained by imaging the 3D distribution of cellular vRNA, observing and characterizing vRNA dynamics, imaging vRNA/Myosin Va colocalization, and studying the effects of cytochalasin D (actin depolymerizing agent) exposure, a model for filamentous virion egress is presented.

Genome sequence of the non-pathogenic strain 15 of pneumonia virus of mice and comparison with the genome of the pathogenic strain J3666

Pneumonia virus of mice (PVM) is a member of the subfamily Pneumovirinae and is the closest known relative of respiratory syncytial virus. Both viruses cause pneumonia in their respective hosts. Here, the genome sequences of two strains of PVM, non-pathogenic strain 15 and pathogenic strain J3666, are reported. Comparison of the genome sequences revealed 59 nucleotide differences between the two strains, 37 of which were coding. The nucleotide differences were spread throughout the genome, affecting cis-acting regulatory regions and seven of the ten genes. Development of a reverse-genetics system for PVM should allow further elucidation of the functional importance of the genetic differences between the two strains identified here.

Animal pneumoviruses: molecular genetics and pathogenesis

Pneumoviruses are single-stranded, negative-sense, nonsegmented RNA viruses of the family Paramyxoviridae, subfamily Pneumovirinae, and include pathogens that infect humans (respiratory syncytial virus and human metapneumovirus), domestic mammals (bovine, ovine, and caprine respiratory syncytial viruses), rodents (pneumonia virus of mice), and birds (avian metapneumovirus). Among the topics considered in this review are recent studies focused on the roles of the individual virus-encoded components in promoting virus replication as well as in altering and evading innate antiviral host defenses. Advances in the molecular technology of pneumoviruses and the emergence of recombinant pneumoviruses that are leading to improved virus-based vaccine formulations are also discussed. Since pneumovirus infection in natural hosts is associated with a profound inflammatory response that persists despite adequate antiviral therapy, we also review the recent experimental treatment strategies that have focused on combined antiviral, anti-inflammatory, and immunomodulatory approaches.

Bovine respiratory syncytial virus (BRSV): a review

Bovine respiratory syncytial virus (BRSV) infection is the major cause of respiratory disease in calves during the first year of life. The study of the virus has been difficult because of its lability and very poor growth in cell culture. However, during the last decade, the introduction of new immunological and biotechnological techniques has facilitated a more extensive study of BRSV as illustrated by the increasing number of papers published. Despite this growing focus, many aspects of the pathogenesis, epidemiology, immunology etc. remain obscure. The course and outcome of the infection is very complex and unpredictable which makes the diagnosis and subsequent therapy very difficult. BRSV is closely related to human respiratory syncytial virus (HRSV) which is an important cause of respiratory disease in young children. In contrast to BRSV, the recent knowledge of HRSV is regularly extensively reviewed in several books and journals. The present paper contains an updated review on BRSV covering most aspects of the structure, molecular biology, pathogenesis, pathology, clinical features, epidemiology, diagnosis and immunology based on approximately 140 references from international research journals.

Filamentous particle formation by human parainfluenza virus type 2

Some paramyxoviruses form long filamentous virus particles: however, the determinants of filament formation and the role of such particles in virus transmission and pathogenicity are not clearly defined. By using conventional immunofluorescence microscopy, we found that human parainfluenza virus type 2 (HPIV2) forms filamentous particles ranging from 5 to 15 microm in length in virus-infected, polarized epithelial cells. The formation of filamentous particles was found to be virus type-specific and was not observed when the same cell types were infected with parainfluenza virus type 3 or Sendai virus, suggesting that different paramyxovirus genera exhibit distinct morphological properties. HPIV2 filamentous particle formation was found to be inhibited by cytochalasin D (CD) or jasplakinolide treatment in a dose-dependent manner. In the presence of 4 microg/ml CD or 1 microM jasplakinolide, the formation of filamentous particles was completely abolished, although similar haemagglutination and p.f.u. titres of virus were found to be released into the culture medium at 24 h post-infection. These observations indicate that host cell components, including the actin microfilament network, are important determinants of the morphology of parainfluenza viruses. The predominance of filamentous particles in polarized epithelial cells may reflect specific pathogenic roles of these particles in infection of human epithelial tissues.

Determination of the disulfide bond arrangement of Newcastle disease virus hemagglutinin neuraminidase. Correlation with a beta-sheet propeller structural fold predicted for paramyxoviridae attachment proteins

Disulfide bonds stabilize the structure and functions of the hemagglutinin neuraminidase attachment glycoprotein (HN) of Newcastle disease virus. Until this study, the disulfide linkages of this HN and structurally similar attachment proteins of other members of the paramyxoviridae family were undefined. To define these linkages, disulfide-linked peptides were produced by peptic digestion of purified HN ectodomains of the Queensland strain of Newcastle disease virus, isolated by reverse phase high performance liquid chromatography, and analyzed by mass spectrometry. Analysis of peptides containing a single disulfide bond revealed Cys(531)-Cys(542) and Cys(172)-Cys(196) linkages and that HN ectodomains dimerize via Cys(123). Another peptide, with a chain containing Cys(186) linked to a chain containing Cys(238), Cys(247), and Cys(251), was cleaved at Met(249) with cyanogen bromide. Subsequent tandem mass spectrometry established Cys(186)-Cys(247) and Cys(238)-Cys(251) linkages. A glycopeptide with a chain containing Cys(344) linked to a chain containing Cys(455), Cys(461), and Cys(465) was treated sequentially with peptide-N-glycosidase F and trypsin. Further treatment of this peptide by one round of manual Edman degradation or tandem mass spectrometry established Cys(344)-Cys(461) and Cys(455)-Cys(465) linkages. These data, establishing the disulfide linkages of all thirteen cysteines of this protein, are consistent with published predictions that the paramyxoviridae HN forms a beta-propeller structural fold.

Characterization of the interaction of the human respiratory syncytial virus phosphoprotein and nucleocapsid protein using the two-hybrid system

The interaction between the human respiratory syncytial virus phosphoprotein (P) and nucleocapsid (N) protein has been investigated using the two hybrid system in yeast and in tissue culture cells. Deletion analysis identified two regions in the P protein involved in this interaction. The immediate carboxy-terminal 20 amino acids were essential for interaction with the N protein. Point mutations in this region demonstrated that alteration of two conserved, phosphorylated, serine residues reduced binding to 50% of that of the native protein. The introduction of two proline residues to disrupt the predicted alpha-helical domain in this region dramatically reduced the ability of the mutant P protein to interact with the N protein. A second region which affected the interaction of the two proteins was located adjacent to the essential carboxy-terminal area. Deletion of this second region resulted in an increase in the strength of the interaction between the two proteins. These data shows that the RSV P protein, while having no amino acid sequence identity with the equivalent P protein of other negative strand viruses, is likely to have similar structural and functional features.

Rescue of synthetic minireplicons establishes the absence of the NS1 and NS2 genes from avian pneumovirus

We have determined the nucleotide sequences of the regions 3' and 5' proximal to the avian pneumovirus (APV) N and L genes, respectively. These sequences were used in the construction of a synthetic minireplicon construct in which the chloramphenicol acetyltransferase (CAT) reporter gene was flanked at its 3' end with the APV leader together with the APV N gene start signal and at its 5' end with the APV L gene end signal and the genome trailer region. The ability of T7 RNA polymerase runoff transcripts to direct the replication and expression of the CAT reporter gene in APV-infected cells demonstrated the ability of the putative leader and trailer regions to direct genome replication and gene expression. Furthermore, this confirms the absence of the NS1 and NS2 gene analogs within the APV genome. We were able to detect the expression of CAT protein from cells that had been infected with supernatants from the initially infected and transfected cells. These results have identified the cis-acting sequences of APV responsible for viral replication, gene expression, and packaging into virus-like particles.

Nucleotide sequence of the genes encoding the matrix and small hydrophobic proteins of pneumonia virus of mice

The nucleotide sequences of the genes encoding the matrix (M) protein and the small hydrophobic (SH) protein of pneumonia virus of mice (PVM) are described. The matrix protein gene contains a large open reading frame encoding polypeptide of 257 residues which shows considerable (38.6-42.1%) amino acid identity with the matrix proteins of other pneumoviruses. The matrix gene also contains a second, smaller, open reading frame (ORF) as seen with the equivalent genes of other pneumoviruses. The PVM second open reading frame is capable of encoding a polypeptide of 46 residues and shows no significant similarity with the proteins encoded by the equivalent open reading frames of the other pneumoviruses. The gene adjacent to that encoding the matrix protein encodes a small, 92 residue, polypeptide which has a central hydrophobic domain and is structurally similar to the small hydrophobic protein of respiratory syncytial virus.

Morphological studies of the respiratory syncytial virus induced bronchiolitis in experimentally infected calves

RSV-infections of the lower respiratory tract in infancy and early childhood are the most frequent causes of a hyperreactive bronchial system and obstructive lung disease. Studies concerning the morphological alterations of the bronchial mucosa during an RSV-infection are dependent on an experimental animal model. In this study the alterations of the lower respiratory tract from five infected colostrum-fed calves during the initial stage of the infection are described. BRSV strain 375 was applied as an aerosol on four consecutive days. The animals showed clinical symptoms already on the first day after infection. 7 days after the first infection the calves were necropsied. Lobular distributed atelectasis of the lung were found. The corresponding bronchioli were collapsed. The bronchiolar lumina were filled with a putrid exudate. In the bronchiolar wall a band-like lymphocytic infiltrate was found. By confocal laserscanning microscopy and by scanning electron microscopy intracellular viral components marked by an antibody against the viral P-protein were depicted. The intracellular virus inclusions were arranged along the bundles of filaments of the cytoskeleton. By transmission electron microscopy an alteration of the ciliogenesis and in cases of severe cell damage, cell death could be observed. The morphological findings suggest that the cytoskeleton plays an important role in the development of bronchiolitis.

Characterisation of the interaction between the nucleoprotein and phosphoprotein of pneumonia virus of mice

A protein blotting technique was used to study the interaction occurring between the pneumonia virus of mice N protein and other PVM encoded proteins expressed in infected cells. Measurement of the degree of binding indicated that the N protein specifically interacted only with the full-length 39 kDa P protein in infected cells. Truncated N-related proteins were synthesised in vitro and incubated with filter-bound full-length and truncated P proteins. The data suggested that many regions of the N protein are cooperatively involved in the binding process. It was also determined that both the amino and the carboxyl-terminal regions of the PVM P protein were essential for binding to N protein.

Sequence and in vitro expression of the phosphoprotein gene of avian pneumovirus

The phosphoprotein (P) gene of two subgroup A strains of avian pneumovirus comprised 855 nucleotides containing only one substantial open reading frame encoding a protein of 278 amino acids, with a predicted M(r) of 30,323. In vitro translation of P mRNA in a wheat germ system resulted in the synthesis of two polypeptides of M(r) 35,000. Comparison of the deduced P protein sequence with that of the known mammalian pneumoviruses revealed overall amino acid identities ranging from 31 to 34.5%, suggesting a distant relationship. However, there was a much higher identity (63.2-68.4%) in a region of 57 residues, which included a heptad repeat sequence.

Respiratory syncytial virus matures at the apical surfaces of polarized epithelial cells

Respiratory syncytial (RS) virus infects the epithelium of the respiratory tract. We examined the replication and maturation of RS virus in two polarized epithelial cell lines, Vero C1008 and MDCK. Electron microscopy of RS virus-infected Vero C1008 cells revealed the presence of pleomorphic viral particles budding exclusively from the apical surface, often in clusters. The predominant type of particle was filamentous, 80 to 100 nm in diameter, and 4 to 8 microns in length, and evidence from filtration studies indicated that the filamentous particles were infectious. Cytopathology produced by RS virus infection of polarized Vero C1008 cells was minimal, and syncytia were not observed, consistent with the maintenance of tight junctions and the exclusively apical maturation of the virus. Infectivity assays with MDCK cells confirmed that in this cell line, RS virus was released into the apical medium but not into the basolateral medium. In addition, the majority of the RS virus transmembrane fusion glycoprotein on the cell surface was localized to the apical surface of the Vero C1008 cells. Taken together, these results demonstrate that RS virus matures at the apical surface of polarized epithelial cell lines.

Assembly of enveloped respiratory syncytial virus particles within the cytoplasm of infected Vero cells

Electron microscopic examination of syncytia induced by a bovine respiratory syncytial virus strain in Vero cell cultures revealed the presence in the cytoplasm of assembled enveloped virus particles within inclusions of variable sizes. Moreover, budding virus particles were shown occasionally in the intracytoplasmic vesicles. These particles were filamentous in form, about 80-120 nm in diameter, variable in length, containing 12 nm diameter nucleocapsids, and looked like the extracellular particles budding at the plasma membranes. This is the first report on assembly of intracellular virus particles in cells infected by a member of the family Paramyxoviridae. Vero cell-dependent variations appear to be the factor leading to the defect in the late virus replication cycle.

Comparison of caprine, human and bovine strains of respiratory syncytial virus

A new continuous ovine kidney cell line allowing the growth of caprine, human and bovine respiratory syncytial virus was used to minimize host cell related variations for the direct comparison of the viral ultrastructures, serological relationships and structural protein profiles. Results show that all three strains are closely related although a closer relationship was found between bovine and caprine RS.

Direct observation of the budding and fusion of an enveloped virus by video microscopy of viable cells

Video-enhanced microscopy and digital image processing were used to observe the assembly, budding, and fusion of Respiratory Syncytial virus. Viral filaments were seen to bud from the plasma membrane of viable infected cells to a final length of 5-10 micron with an average speed of elongation of 110-250 nm/s. The rapidity of viral assembly and its synchronous occurrence (leading to the production of several viral particles per minute from the same surface domain) suggests a directed process of recruitment of viral components to an area selected for virus maturation. Virions were also seen to adsorb to the cell surface, and to fuse with the plasma membrane. These are the first real time observations of viral morphogenesis and penetration which are crucial events in the infectious cycle of enveloped viruses.

Respiratory syncytial virus glycoproteins

The proteins of respiratory syncytial (RS) virus were analyzed by SDS-polyacrylamide gel electrophoresis. Eight virion structural proteins with molecular weights of 180,000, 89,000, 48,000, 42,000, 34,000, 28,000, 25,000, and 21,000 were identified. These proteins were given tentative designations of L (180,000), G (89,000), F1 (48,000), NP (42,000), P (34,000), M (28,000), Vp25 (25,000), and F2 (21,000). The 89,000-, 48,000-, and 21,000-dalton polypeptides were glycosylated and could be purified on lentil-lectin sepharose columns. All three glycoproteins could be immunoprecipitated from extracts of infected cells but not from uninfected cells, suggesting that they are viral specified. The host cell affected the apparent molecular weights of the largest and smallest glycosylated polypeptides possibly by differences in glycosylation. The 48,000- and 21,000-dalton glycopolypeptides were disulfide linked subunits of a 68,000-dalton glycoprotein that was seen on unreduced gels. The 68,000-dalton glycoprotein was thus similar to the fusion (F) protein of paramyxoviruses. Treatment of infected cultures with tunicamycin, a drug that blocks glycosylation, inhibited syncytial formation and resulted in over a 1000-fold reduction of extracellular infectious virus. Virions purified from tunicamycin-treated cells had reduced amounts of all three glycosylated proteins. No new forms of these proteins were conclusively identified, suggesting that unglycosylated forms of RS glycoproteins were not incorporated into virion membranes.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Morphogenesis and structure of caprine respiratory syncytial virus

Cell cultures inoculated with caprine respiratory syncytial virus (RSV) were studied with light, fluorescent, and electron microscopy to determine the morphogenesis and structure of the virus. Small syncytia were seen after 36 hours in culture. After 48 hours in culture, syncytia were large and numerous and pleomorphic cytoplasmic inclusions were seen. These inclusions were more pronounced and numerous later in the infection cycle. Indirect immunofluorescence revealed a diffuse to granular cytoplasmic fluorescence with fluorescing fibrils on the cell surface. With the electron microscope, filamentous (100-160 nm) and spherical (90-160 nm) particles were seen budding off the cell membrane. The number of virus buds diminished with increased size of syncytia. Granular pleomorphic cytoplasmic inclusions were seen near the nucleus, and electron dense masses were seen just beneath the cytoplasmic membrane where large quantities of virus were budding from the cell surface. The first type of inclusion had distinct borders; the second diffuse borders and appeared to contain viral nucleoprotein. Negative staining revealed spherical, pleomorphic, and filamentous forms of the virus; the last form predominated. The virions were covered with club-shaped projections, and the nucleocapsids were seen as fragile strands frequently broken into fragments or as isolated rings. Morphogenesis and structure of the caprine RSV places this virus with the Pneumovirus genus of the Paramyxoviridae family.

Bovine respiratory syncytial virus infection of bovine embryonic lung cultures: enhancement of infectivity with diethylaminoethyl-dextran and virus-infected cells

The effects of incorporating diethylaminoethyl-dextran (DEAE-D) in the inoculum with bovine respiratory syncytial virus (BRSV) on the infectivity of BRSV was evaluated. A concentration of 40 microgram DEAE-D/ml provided maximal enhancement of infection as determined by the time of onset of cytopathic effect (CPE), the percentage of cells infected by the inoculum, and the amount of virus produced. When DEAE-D was used in the inoculum, the CPE appeared a day earlier, the percentage of cells infected by the inoculum, as determined by the fluorescent antibody test, was increased 11 times, and the viral titer was increased 2 times as compared to results obtained without DEAE-D. Bovine respiratory syncytial virus-infected cultures contained much cell-associated virus which could be liberated by sonication to increase the titer of virus stocks. The use of BRSV-infected cells rather than supernates from BRSV-infected cells increased the rate at which a cytopathic effect developed, although it did not substantially increase the titer of virus which was harvested. The use of DEAE-D in the inoculum and the passage of BRSV-infected cells instead of viral suspensions was found to be the quickest and most effective method of consistently obtaining BRSV with a titer of about 10(5.5) TCID50/ml.

Polypeptides of respiratory syncytial virus

Radiolabeled respiratory syncytial virus was purified from medium that had been harvested from infected HeLa cell monolayers before it contained much cellular debris. After isopycnic centrifugation in linear gradients prepared with sucrose dissolved in Hanks balanced salt solution, almost all the infectivity and most of the radioactivity were recovered in a single band with density from 1.16 to 1.23 g/cm3 and a peak at 1.2 g/cm3. Analysis by polyacrylamide gel electrophoresis resolved the purified virus into seven polypeptides of approximate molecular weights 20,000 to 80,000, of which the two largest and the smallest proved to by glycoproteins.

Herpes encephalitis. Rapid diagnosis and treatment with antiviral drugs

The use of specific IgM antibodies and direct electron-microscopic examination of brain biopsies or vesicle fluid was tested as means of raped diagnosis in 6 cases of herpes simplex encephalitis seen consecutively in Montreal. In 2 of 3 biopsies herpes viruses were seen by negative staining of a cell extract within 1 hr. In the negative case, the biopsy was done almost 1 month after onset. In 2 additional cases herpes virus particles were found directly in the fluid of isolated vesicles. In the last 2 cases, who survived, the diagnosis of herpes encephalitis rested upon the demonstration of a greater than 4-fold rise in complement fixing herpes simplex virus antibodies in convalescent sera and upon the appearance late in the course of the encephalitis of specific antibodies in the cerebrospinal fluid. The early appearance of specific IgM antibodies contributed to the diagnosis in 4 of the 6 cases. Antiviral therapy was attempted in alternate cases (3 cases) but was not successful. Brain biopsy is rarely performed for diagnostic purposes but when prompt antiviral therapy is contemplated, the examination of the biopsy material for herpes virus particles by electron microscopy in negative staining and thin sections can rapidly and reliably confirm the diagnosis.