Altered interaction of the matrix protein with the cytoplasmic tail of hemagglutinin modulates measles virus growth by affecting virus assembly and cell-cell fusion

Clinical isolates of measles virus (MV) use signaling lymphocyte activation molecule (SLAM) as a cellular receptor, whereas vaccine and laboratory strains may utilize the ubiquitously expressed CD46 as an additional receptor. MVs also infect, albeit inefficiently, SLAM(-) cells, via a SLAM- and CD46-independent pathway. Our previous study with recombinant chimeric viruses revealed that not only the receptor-binding hemagglutinin (H) but also the matrix (M) protein of the Edmonston vaccine strain can confer on an MV clinical isolate the ability to grow well in SLAM(-) Vero cells. Two substitutions (P64S and E89K) in the M protein which are present in many vaccine strains were found to be responsible for the efficient growth of recombinant virus in Vero cells. Here we show that the P64S and E89K substitutions allow a strong interaction of the M protein with the cytoplasmic tail of the H protein, thereby enhancing the assembly of infectious particles in Vero cells. These substitutions, however, are not necessarily advantageous for MVs, as they inhibit SLAM-dependent cell-cell fusion, thus reducing virus growth in SLAM(+) B-lymphoblastoid B95a cells. When the cytoplasmic tail of the H protein is deleted, a virus with an M protein possessing the P64S and E89K substitutions no longer grows well in Vero cells yet causes cell-cell fusion and replicates efficiently in B95a cells. These results reveal a novel mechanism of adaptation and attenuation of MV in which the altered interaction of the M protein with the cytoplasmic tail of the H protein modulates MV growth in different cell types.     

Functional analysis of matrix proteins expressed from cloned genes of measles virus variants that cause subacute sclerosing panencephalitis reveals a common defect in nucleocapsid binding.

We have developed an in vitro nucleocapsid-binding assay for studying the function of the matrix (M) protein of measles virus (MV) (A. Hirano, A. H. Wang, A. F. Gombart, and T. C. Wong, Proc. Natl. Acad. Sci. USA, 89:8745-8749, 1992). In this communication we show that the M proteins of three MV strains that cause acute infection (Nagahata, Edmonston, and YN) bind efficiently to the viral nucleocapsids whereas the M proteins of four MV strains isolated from patients with subacute sclerosing panencephalitis (SSPE) (Biken, IP-3, Niigata, and Yamagata) fail to bind to the viral nucleocapsids. MV Biken (an SSPE-related virus) produces variant M sequences which encode two antigenically distinct forms of M protein. A serine-versus-leucine difference is responsible for the antigenic variation. MV IP-3 (an SSPE-related virus) also produces variant M sequences, some of which have been postulated to encode a functional M protein responsible for the production of an infectious revertant virus. However, the variant M proteins of Biken and IP-3 strains show no nucleocapsid-binding activity. These results demonstrate that the nucleocapsid-binding function is conserved in the M proteins of MV strains that cause acute infection and that the M proteins of MV strains that cause SSPE exhibit a common defect in this function. Analysis of chimeric M proteins indicates that mutations in the amino-terminal, carboxy-proximal, or carboxy-terminal region of the M protein all abrogate nucleocapsid binding, suggesting that the M protein conformation is important for interaction with the viral nucleocapsid.     

Relation Between the Chemical Structure and the Biological Activity of Hydroxystilbenes Against Botrytis cinerea

Abstract A Spanish strain of pepper mild mottle virus (PMMV-S) (A lonso et al. 1989) can be differentiated from the Italian PMMV (W etter et al. 1984) by the responses of Capsicum spp. with resistance genes to tobamoviruses, by radioimmunoassay and by the electrophoretic mobility of their viral particles. Moreover, the analysis of the electrophoretic mobility of the viral particles in agarose gels and that of the viral coat proteins in polyacrylamide-urea gels are reliable and rapid techniques for distinguishing PMMV isolates from other members of the tobamovirus group and thus can be used for diagnostic purposes. These results support the proposal of grouping these pepper viruses, including the "pepper strains" of TMV, as a new tobamovirus subgroup (PARES 1985, BETTI et al. 1987, WETTER et al. 1987, ALONSO et al. 1989).     

Phylogenetic analyses of pandemic influenza A (H1N1) virus in university students at Tobetsu, Hokkaido, Japan

Pandemic influenza H1N1 virus (A[H1N1]pdm09) emerged in 2009. To determine the phylogeography of A(H1N1)pdm09 in a single population, 70 strains of the virus were isolated from university students or trainee doctors at Tobetsu, Hokkaido, Japan, between September and December 2009. The nucleotide sequences of the HA1 region of the HA genes and described phylogenetic relationships of the strains circulating among them were analyzed. It was found that the 70 isolates could be phylogenetically separated into three groups and that two epidemics were caused by different groups of the virus. The three groups were also distinguishable from each other by three amino acid changes: A197T, S203T and Q293H. The substitution of S203T, which is located in the antigenic site, suggests antigenic drift of the virus.     

Molecular Comparison of Dengue Type 1 Mochizuki Strain Virus and Other Selected Viruses Concerning Nucleotide and Amino Acid Sequences of Genomic RNA: A Consideration of Viral Epidemiology and Variation

Dengue-1 (D1) Mochizuki strain was examined for its nucleotide and amino acid sequences of genomic RNA and the data obtained were compared with those of other selected virus strains reported previously. Genomic regions corresponding to C, preM and M proteins were the major subjects of study. Parts of E protein were additionally examined. Among the D1 viruses investigated, the Mochizuki virus which was isolated in 1943 in Japan was shown to be close to Philippine 836-1 strain isolated in 1984 and Nauru Island strain isolated in 1974 at the respective places, in contrast with Thai AHF 82-80 strain isolated in 1980 and Caribbean CV1636/77 strain isolated in 1977. At the same time, a difference was noted between the Mochizuki and Philippine/Nauru strains at the cleavage site of preM/M junction: Mochizuki possessed RRGKR/S sequence whereas the Philippine/Nauru had RRDKR/S. The glycosylation site in preM and hydrophobic regions at the carboxyl termini of M and E were well conserved. Significances of the data are discussed in connection with viral epidemiology and variation.     

Structural proteins of poliovirus type 2 isolates

Seventeen strains of type 2 poliovirus isolated from vaccines and vaccine-contacts in Japan were analyzed for viral structural proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis. An alteration in electrophoretic mobility of VP1 was observed in most of the strains from paralytic patients and healthy vaccinees. The alteration in VP1 was observed at a high frequency among many strains, but no significant relation between the mobility change of VP1 and antigenic marker or rct/40 marker was observed. No alteration in mobility of other structural proteins was observed among the strains examined except for one with altered VP3. The results suggested that VP1 of Sabin type 2 strain was easily changeable during replication in human intestines.     

Mutants of simian virus 40 differing in plaque size, oncogenicity, and heat sensitivity

Takemoto, K. K. (National Institute of Allergy and Infectious Diseases, Bethesda, Md.), R. L. Kirschstein, and K. Habel. Mutants of simian virus 40 differing in plaque size, oncogenicity, and heat sensitivity. J. Bacteriol. 92:990-994. 1966.-Three mutants of simian virus 40 were isolated on the basis of the type of plaques produced in primary cultures of African green monkey kidney cells and designated as L (large), S (small), and M (minute) strains. Significant differences in oncogenicity for hamsters were observed, with the 50% oncogenic dose being 10(4.5) for the L, 10(5.2) for the S, and 10(5.8) for the M strains. All three strains were capable of transforming human diploid cells (W138 strain). At temperatures up to 41 C, the S and M mutants were capable of multiplying to titers almost equivalent to those obtained at 37 C. In contrast, infectious virus was not produced when cells were infected with the L mutant and were incubated at temperatures above 39 C, although complement-fixing viral and tumor antigens were formed. The temperature-sensitive phase of replication of the L strain was shown to be a late stage in viral maturation or assembly.     

Antigenic and genetic variation in influenza A (H1N1) virus isolates recovered from a persistently infected immunodeficient child.

Antigenic and genetic variations have been analyzed in eight consecutive isolates recovered from a child with severe combined immunodeficiency syndrome persistently infected with naturally acquired type A (H1N1) influenza virus over a 10-month period. Hemagglutination inhibition reactions and T1 oligonucleotide fingerprinting demonstrated that these viruses were related to strains causing outbreaks in the United States at that time (1983 to 1984) but that antigenic and genetic differences between consecutive isolates could be detected. This variation between isolates was examined further by sequencing the RNAs encoding the HA1 region of the hemagglutinin (HA) and the nucleoprotein (NP) in five of the consecutive isolates. Multiple point mutations were detected in both genes, and a deletion of one amino acid was detected in the HA. Depending on the isolates compared, 5.8 x 10(-3) to 17 x 10(-3) substitutions per nucleotide site per year were detected in the RNAs encoding the HA1, and 3.5 x 10(-3) to 24 x 10(-3) substitutions per nucleotide site per year were detected in the NP gene. Fifty-four percent of the base changes in the HA1 and 73% in the NP led to amino acid substitutions. A progressive accumulation of mutations over time was not observed, suggesting that the genetic diversity of these viruses may best be interpreted as the result of shifts in the population equilibrium (quasi-species) of replicating variant genomes.     

Antigenic anachronism of influenza viruses A(H2N2) in Leningrad in 1980. II. The laboratory characteristics of influenza A/Leningrad/80 viruses

As indicated by the results of the hemagglutination inhibition (HAI) test, influenza viruses A/Leningrad/80 contain hemagglutinin (HA), similar to that of virus A/Singapore/1/57 (H2N2). Neuraminidase contained in viruses A/Leningrad/80 belongs to serological subtype N2 and is similar to that of virus A/Singapore/1/57 (H2N2). No differences in the polypeptide composition of the virus-induced proteins of viruses A/Leningrad/527/80, A/Leningrad/549/80, A/Leningrad/553/80 and virus A/Singapore/1/57 used as reference have been detected in the study of their electrophoretic mobility in polyacrylamide gel, as well as the mobility of duplexes obtained by the hybridization of the virion and complement RNA of viruses A/Leningrad/553/80 and A/Singapore/1/57. The results of the HAI test with antisera to purified HA indicate that virus A/Leningrad/549/80 contains HA similar to that of viruses A(H2N2) isolated in 1957, but not in 1964. The HAI test with the sera of polecats having the infection permits the differentiation of viruses A/Leningrad/80 from epidemic viruses A(H2N2) isolated in 1957-1965, including reference virus A/Singapore/1/57. In relation to the latter, the isolates of 1980 are older antigenic mutants. The isolates of 1980 are distinguished from virus A(H2N2), isolated in 1975 from the system of persisting influenza infection in a tissue culture, by mutation in NS-gene and the properties of RNA-polymerase. The authenticity of the isolation of viruses A(H2N2) in Leningrad in 1980 has been proved.     

Measles virus assembly within membrane rafts

During measles virus (MV) replication, approximately half of the internal M and N proteins, together with envelope H and F glycoproteins, are selectively enriched in microdomains rich in cholesterol and sphingolipids called membrane rafts. Rafts isolated from MV-infected cells after cold Triton X-100 solubilization and flotation in a sucrose gradient contain all MV components and are infectious. Furthermore, the H and F glycoproteins from released virus are also partly in membrane rafts (S. N. Manié et al., J. Virol. 74:305-311, 2000). When expressed alone, the M but not N protein shows a low partitioning (around 10%) into rafts; this distribution is unchanged when all of the internal proteins, M, N, P, and L, are coexpressed. After infection with MGV, a chimeric MV where both H and F proteins have been replaced by vesicular stomatitis virus G protein, both the M and N proteins were found enriched in membrane rafts, whereas the G protein was not. These data suggest that assembly of internal MV proteins into rafts requires the presence of the MV genome. The F but not H glycoprotein has the intrinsic ability to be localized in rafts. When coexpressed with F, the H glycoprotein is dragged into the rafts. This is not observed following coexpression of either the M or N protein. We propose a model for MV assembly into membrane rafts where the virus envelope and the ribonucleoparticle colocalize and associate.     

Distinction between Epstein-Barr virus type A (EBNA 2A) and type B (EBNA 2B) isolates extends to the EBNA 3 family of nuclear proteins.

The Epstein-Barr virus (EBV) nuclear antigens EBNA 3a, 3b, and 3c have recently been mapped to adjacent reading frames in the BamHI L and E fragments of the B95.8 EBV genome. We studied by immunoblotting the expression of the family of EBNA 3 proteins in a panel of 20 EBV-transformed lymphoblastoid cell lines (LCLs) carrying either type A (EBNA 2A-encoding) or type B (EBNA 2B-encoding) virus isolates. Certain human sera from donors naturally infected with type A isolates detected the EBNA 3a, 3b, and 3c proteins in all type A virus-transformed LCLs (with a single exception in which EBNA 3b was not detected) but detected only EBNA 3a in LCLs carrying type B isolates. These results were confirmed with human and murine antibodies with specific reactivity against sequences of the type A EBNA 3a, 3b, or 3c expressed in bacterial fusion proteins. Conversely, selected human sera from donors naturally infected with type B strains of EBV identified the EBNA 3a encoded by both types of isolates plus two novel EBNAs present only in type B, and not in type A, virus-transformed LCLs; these novel proteins appear to be the type B homologs of EBNA 3b and 3c. The distinction between type A and type B EBV isolates therefore extends beyond the EBNA 2 gene to the EBNA 3 family of proteins. This has important implications with respect to the evolutionary origin of these two EBV types and also places in a new light recent studies which identified differences between type A and type B transformants in terms of growth phenotype (A. B. Rickinson, L. S. Young, and M. Rowe, J. Virol. 61:1310-1317, 1987) and of detection by EBV-specific cytotoxic T cells (D. J. Moss, I. S. Misko, S. R. Burrows, K. Burman, R. McCarthy, and T. B. Sculley, Nature [London] 331:719-721, 1988).     

Molecular genetic characterization of H5N1 influenza virus strains isolated from poultry in the Kurgan region in 2005

In the second half of 2005, a large-scale outbreak of influenza in poultry and wild birds was caused by a highly pathogenic H5N1 influenza virus in Russia. The level of pathogenicity is a polygenic trait, and most individual genes contribute to the influenza A virus pathogenicity in birds, animals, and humans. The full-length nucleotide sequences were determined for H5N1 strains isolated in the Kurgan region (Western Siberia). The structure of viral proteins was analyzed using the deduced amino acid sequences. The receptor-binding site of hemagglutinin (HA) in strains A/chicken/Kurgan/05/2005 and A/duck/Kurgan/08/2005 was typical for avian influenza viruses and contained Glu and Gly at positions 226 and 228, respectively. The structure of the basic amino acid cluster located within the HA cleavage site was identical in all isolates: QGERRRKKR. According to the neuraminidase structure, all H5N1 isolates from the Kurgan region were assigned to the Z genotype. Amino acid residues typical for the avian influenza virus were revealed in 30 out of 32 positions of M1, M2, NP, PA, and PB2, determining the host range specificity. One of the strains contained Lys at position 627 of PB2. Isolates from the Kurgan region were shown to have a remantadine-sensitive genotype. Both strains contained Glu at position 92 of NS1, indicating that the virus is interferon-resistant. Phylogenetic analysis related the Kurgan isolates to subclade 2 of clade 2 of highly pathogenic H5N1 influenza viruses.     

A candidate for a new serotype of human rotavirus

We investigated genetic and serological characteristics of a human rotavirus isolate from Indonesia which had a "super short" RNA electrophoretic pattern (A. Hasegawa, S. Inouye, S. Matsuno, K. Yamaoka, R. Eko, and W. Suharyono, Microbiol. Immunol. 28:719-722, 1984). This virus, strain 69M, was found by RNA-RNA hybridization to have a low degree of homology with the representative strains of all four human serotypes. Furthermore, it could not be classified by neutralization analysis into any of these serotypes. Therefore, this virus might belong to a new serotype.     

The 10,400- and 14,500-dalton proteins encoded by region E3 of adenovirus function together to protect many but not all mouse cell lines against lysis by tumor necrosis factor.

We have reported that the E3 14,700-dalton protein (E3 14.7K protein) protects adenovirus-infected mouse C3HA fibroblasts against lysis by tumor necrosis factor (TNF) (L. R. Gooding, L. W. Elmore, A. E. Tollefson, H. A. Brady, and W. S. M. Wold, Cell 53:341-346, 1988). We have also observed that the E1B 19K protein protects adenovirus-infected human but not mouse cells against TNF lysis (L. R. Gooding, L. Aquino, P. J. Duerksen-Hughes, D. Day, T. M. Horton, S. Yei, and W. S. M. Wold, J. Virol. 65:3083-3094, 1991). We now report that, in the absence of E3 14.7K, the E3 10.4K and E3 14.5K proteins are both required to protect C127 as well as several other mouse cell lines against TNF lysis. The 14.7K protein can also protect these cells from TNF in the absence of the 10.4K and 14.5K proteins. This protection by the 10.4K and 14.5K proteins was not observed in the C3HA cell line. These conclusions are based on 51Cr release assays of cells infected with virus E3 mutants that express the 14.7K protein alone, that express both the 10.4K and 14.5K proteins, and that delete the 14.7K in combination with either the 10.4K or 14.5K protein. The 10.4K protein was efficiently coimmunoprecipitated together with the 14.5K protein by using an antiserum to the 14.5K protein, suggesting that the 10.4K and 14.5K proteins exist as a complex in the infected mouse cells and consistent with the notion that they function in concert. Considering that three sets of proteins (E3 14.7K, E1B 19K, and E3 10.4K/14.5K proteins) exist in adenovirus to prevent TNF cytolysis of different cell types, it would appear that TNF is a major antiadenovirus defense of the host.     

Mycobacterium kumamotonense Sp. Nov. recovered from clinical specimen and the first isolation report of Mycobacterium arupense in Japan: Novel slowly growing, nonchromogenic clinical isolates related to Mycobacterium terrae complex

Three mycobacterium strains isolated from clinical specimens in Japan were provisionally assigned to the genus Mycobacterium based on their phenotypical characteristics. These isolates were further investigated to determine their specific taxonomic statuses. Mycolic acid analysis and 16S rRNA gene, rpoB, and hsp65 sequence data for the isolates showed that they are most similar to M. terrae complex. DNA-DNA hybridization studies indicated that the three strains were of two species and were distinguishable from M. terrae, M. nonchromogenicum, and M. hiberniae. Therefore, these strains represent two novel species within the genus Mycobacterium. However, one potential new species should have been considered as M. arupense with the 16S rRNA gene and hsp65 sequences similarities of 99.8% and 100% respectively; it was isolated from human specimens in the United States and was proposed in June 2006 as a new species. This report describes the first isolation of M. arupense in Japan, suggesting that the organism is clinically relevant. In addition, we propose the novel species designation Mycobacterium kumamotonense sp. nov. The type strain is CST 7247(T) (=GTC 2729(T), =JCM 13453(T), =CCUG 51961(T)).     

Single-point mutations of the M protein of a measles virus variant obtained from a patient with subacute sclerosing panencephalitis critically affect solubility and subcellular localization of the M protein and cell-free virus production

Subacute sclerosing panencephalitis (SSPE) is caused by variants of wild-type measles virus (MV). Such MV variants lack almost completely the ability to produce cell-free progeny virus. We recently isolated an MV variant that has only three amino acid mutations (L165P,L250P and Y282H) in the M protein compared with MV field isolates of the same genotype. In the present study, we analyzed the significance of these mutations with regard to the characteristics of the M protein and progeny virus production. We found that each of the three mutations rendered the M protein insoluble in 0.5% Triton X-100 and altered its subcellular localization, either when ectopically expressed alone using a plasmid-based expression system or when expressed in the context of viral replication. Moreover, each of the three mutations markedly, but not completely, impaired the ability of MV to produce cell-free progeny virus, with the degree of impairment being the same as for all three mutations together. These results suggest the possibility that the changes in the solubility and subcellular localization of the M protein determine the ability to produce cell-free progeny virus, at least to some extent, and play a role in the pathogenicity of variants causing SSPE.     

Genomic analysis of pandemic (H1N1) 2009 reveals association of increasing disease severity with emergence of novel hemagglutinin mutations

Experimental studies and epidemiological observations during the first wave of the pandemic (H1N1) 2009 suggest that a novel influenza A (H1N1) virus has significant pandemic potential based on high transmissibility of the virus. Substantial uncertainty remains regarding evolution of the clinical severity of this pandemic during the transition to the second wave which is currently underway in the Northern Hemisphere. We carried-out analysis of large volume of clinical, epidemiological and genomics data for assessment of evolution of the current pandemic in United States, Canada, United Kingdom, Australia and Japan based on official reports of public health agencies of corresponding countries. Analysis of reported sequences of virus strains isolated from postmortem samples indicates that 42.9% of individuals who died from laboratory-confirmed cases of the pandemic (H1N1) were infected with the hemagglutinin (HA) Q310H mutant virus. Overall, six of seven (86%) of virus isolates recovered from the necropsy samples have at least one mutation within the HA 301–316 or HA 219–240 regions. During the second wave of the pandemic (H1N1) 2009, there is an increased number of reported double mutant virus isolates with mutations within both of these HA regions. Mutations within HA 219-240 region at the position D239 (D239E/G/N) are reported with higher frequency. In addition, D239G mutants were detected more frequently in viruses isolated from patients with fatal outcomes and in isolates from lungs. Multiple viral isolates with the novel HA 301-316 mutations (I312V and P314S) have been documented. Statistically significant increase of detection of mutant viruses and H1N1-related death rates is documented in July-September reporting time periods. Our analysis seems to indicate that evolution of current pandemic is associated with notable changes in mortality rate among hospitalized patients and increasing number of reported cases of novel mutations of HA gene. Recently emerged HA mutants are: (1) detected in large proportion of virus isolates recovered from the postmortem samples; (2) documented in multiple independent reports around the world; (3) expanding within global viral population; (4) manifesting spatial and temporal patterns of association with increased mortality rate of hospitalized patients. Identification of candidate virus mutants with potential association to increasing disease severity should facilitate clinical and experimental testing of the validity of both “antigenic drift” and increase virulence hypotheses. The results of these follow-up experiments may have a significant impact on ultimate outcomes of current pandemic. Our analysis indicates the urgent need for international surveillance systems that track disease severity and individual patient influenza sequence data in a representative fashion. Information gained from this type of surveillance will direct experimental work that assesses influenza strain-specific features of virulence and transmissibility through carefully designed and timely executed laboratory studies. Practical implementation of these surveillance systems would facilitate the timely evidence-based resolution of critically important relationships between the antigenic drift of mutant strains and immunogenicity of existing vaccines which should be assessed in the laboratory setting during the course of the ongoing pandemic.     

Molecular biological differences between strains of Mycoplasma gallisepticum]

Differences in virulence of two Mycoplasma gallisepticum strains, S6 and A5969, are confirmed in experiments with chickens. Macromolecular discrepancies detected between these two strains are concerning the genomic size, electrophoretic spectra of DNA and proteins. Cross immunoblotting data with polyclonal and monoclonal antibodies reveal major immunogens of protein nature in both the strains. Homologous proteins with different electrophoretic mobility are detected in other four M. gallisepticum strains. A possible participation of these proteins of M. gallisepticum in adhesion to the host cells is discussed.     

Characterization of Two Strains of Cowpea Mild Mottle Virus Naturally Infecting Groundnut (Arachis hypogaea L.) in India

Two viruses were isolated from commercial groundnut plants showing mild mottle (MM) and severe mottle (SM) symptoms in the Rayalaseema area of Andhra Pradesh State, India. The host range of both the isolates was restricted to Fabaceae. The physical properties of both isolates were: DEP 10^-6 to 10^-7. TIP 70–85 C and LIV 5–8 days. Partially purified virus preparations contained slightly flexuous filamentous particles. In ELISA and gel diffusion tests both isolates reacted similarly with anusera to the carlaviruses cowpea mild mottle, cassia mild mosaic and potato M. Particle morphology. sedimentation coefficient, and estimated sizes of the coat proteins and RNAs gave additional evidence that the viruses were carlaviruses. Bemisia labaci transmitted only the MM isolate and the two isolates also differed in electrophoretic mobility of intact particles and amino acid composition of the coat proteins. The isolates are identified as distinct strains of cowpea mild mottle virus.