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T M Chambers

Publications and source records attributed to T M Chambers.

34 records · Page 2Linked to original sources
PubMed1992

Evolution and ecology of influenza A viruses.

In this review we examine the hypothesis that aquatic birds are the primordial source of all influenza viruses in other species and study the ecological features that permit the perpetuation of influenza viruses in aquatic avian species. Phylogenetic analysis of the nucleotide sequence of influenza A virus RNA segments coding for the spike proteins (HA, NA, and M2) and the internal proteins (PB2, PB1, PA, NP, M, and NS) from a wide range of hosts, geographical regions, and influenza A virus subtypes support the following conclusions. (i) Two partly overlapping reservoirs of influenza A viruses exist in migrating waterfowl and shorebirds throughout the world. These species harbor influenza viruses of all the known HA and NA subtypes. (ii) Influenza viruses have evolved into a number of host-specific lineages that are exemplified by the NP gene and include equine Prague/56, recent equine strains, classical swine and human strains, H13 gull strains, and all other avian strains. Other genes show similar patterns, but with extensive evidence of genetic reassortment. Geographical as well as host-specific lineages are evident. (iii) All of the influenza A viruses of mammalian sources originated from the avian gene pool, and it is possible that influenza B viruses also arose from the same source. (iv) The different virus lineages are predominantly host specific, but there are periodic exchanges of influenza virus genes or whole viruses between species, giving rise to pandemics of disease in humans, lower animals, and birds. (v) The influenza viruses currently circulating in humans and pigs in North America originated by transmission of all genes from the avian reservoir prior to the 1918 Spanish influenza pandemic; some of the genes have subsequently been replaced by others from the influenza gene pool in birds. (vi) The influenza virus gene pool in aquatic birds of the world is probably perpetuated by low-level transmission within that species throughout the year. (vii) There is evidence that most new human pandemic strains and variants have originated in southern China. (viii) There is speculation that pigs may serve as the intermediate host in genetic exchange between influenza viruses in avian and humans, but experimental evidence is lacking. (ix) Once the ecological properties of influenza viruses are understood, it may be possible to interdict the introduction of new influenza viruses into humans.

Animals↗
PubMed1991

Influenza viral infection of swine in the United States 1988-1989.

Swine are an animal reservoir for influenza viruses capable of causing disease in humans. A serological survey in 1988-1989 demonstrates that subtype H1 influenza viruses continue to circulate at high frequency among swine in the north-central U.S.A. (average 51% incidence). Subtype H3 viruses antigenically similar to current human H3 viruses are circulating at low frequency (average 1.1%), particularly in the southeast U.S.A.

Animals↗
PubMed1991

Protection of chickens from lethal influenza virus infection by influenza A/chicken/Pennsylvania/1/83 virus: characterization of the protective effect.

The influenza A/chicken/Pennsylvania/1/83 (H5N2) virus is the first known example of an influenza virus isolated from a natural infection which contained primarily defective interfering particles (T. M. Chambers and R. G. Webster, J. Virol. 61, 1517-1523, 1987). In chickens, coinoculation of this virus together with the closely related but highly virulent influenza A/chicken/Pennsylvania/1370/83 virus results in reduced mortality compared to virulent virus infection alone (Bean et al., J. Virol. 54, 151-160, 1985). The biological basis of this protective effect has not been established. Protective activity required greater than or equal to 100-fold excess input of protecting virus over virulent virus, functioned effectively during the first generations of virulent virus multiplication, and also functioned against an antigenically heterologous (H7N7) virulent influenza virus. Protection was correlated with the complete inhibition of virulent virus spread to the brain of infected chickens. Plaque-purified chicken/Pennsylvania/1/83 virus depleted of defective interfering particles, and beta-propiolactone-inactivated virus, had no protective effect. These characteristics are consistent with the hypothesis that protection was the result of defective interfering particle-mediated interference with virulent virus multiplication within the respiratory tract of the chicken.

Animals↗
PubMed1990

Conditional expression of foreign genes by temperature-sensitive mutants of vaccinia virus.

To assess the utility of two temperature-sensitive (ts) mutant vaccinia viruses as vectors for the conditional in vitro expression of recombinant foreign genes, we have studied the kinetics of expression of foreign genes incorporated into these viruses. At nonpermissive temperature, 40 degrees C, these viruses were defective either in DNA synthesis or in virus assembly. Foreign gene expression was affected by the nature of the ts lesion and by the nature of the vaccinia promoter positioned upstream from the foreign gene. With both vector viruses, a foreign gene controlled by the p7.5 early-late promoter was expressed at both 33 degrees and 40 degrees C. With the DNA synthesis-defective vector virus, foreign gene expression controlled by the p11 DNA synthesis-dependent late promoter was inhibited at 40 degrees C, but could be turned on by shift to 33 degrees C. This ts expression system provides an alternative to use of drugs that inhibit DNA synthesis as a means for experimental manipulation of gene expression. Both vector viruses can be used with existing vaccinia virus expression technology.

DNA, Recombinant↗
PubMed1990

Molecular characterization of a new hemagglutinin, subtype H14, of influenza A virus.

Two influenza A viruses whose hemagglutinin (HA) did not react with any of the reference antisera for the 13 recognized HA subtypes were isolated from mallard ducks in the USSR. Antigenic analysis by hemagglutination inhibition and double immunodiffusion tests showed that the HAs of these viruses are similar to each other but distinct from the HAs of other influenza A viruses. Nucleotide sequence analysis showed that these HA genes differ from each other by only 21 nucleotides. However, they differ from all other HA subtypes at the amino acid level by at least 31% in HAI. Thus, we propose that the HAs of these viruses [A/Mallard/Gurjev/263/82 (H14N5) and A/Mallard/Gurjev/244/82 (H14N6) belong to a previously unrecognized subtype, and are designated H14. Unlike any other HAs of influenza viruses, the H14 HAs contained lysine at the cleavage site between HA1 and HA2 instead of arginine. Experimental infection of domestic poultry and ferrets with A/Mallard/Gurjev/263/82 (H14N5) showed that the virus is avirulent for these animals. Based on comparative sequence analysis of different HA genes, it is suggested that differences of 30% or more at the amino acid level in HA1 constitute separate subtypes. Phylogenetic analysis of representatives of each HA subtype showed that H14 is one of the most recently diverged lineages while H8 and H12 branched off early during the evolution of the HA subtypes. These latter two subtypes (H8 and H12) have been isolated very infrequently in recent years, suggesting that these old subtypes may be disappearing from the influenza reservoirs in nature.

Amino Acid Sequence↗
PubMed1989

Antigenic and molecular characterization of subtype H13 hemagglutinin of influenza virus.

Influenza A viruses with subtype H13 hemagglutinin display an unusual host range. Although common in shorebirds, they are very rare or absent in wild ducks; additionally, H13 viruses have been isolated from a whale. To study the molecular basis for this host range, we have determined the complete nucleotide sequences of the hemagglutinin genes of three H13 influenza viruses from different species or geographical areas: A/gull/Maryland/77, A/gull/Astrachan (USSR)/84, and A/pilot whale/Maine/84. Based on the deduced amino acid sequences, H13 hemagglutinin shares the basic structure of other type A hemagglutinin subtypes such as H3, but has clearly diverged from other completely sequenced subtypes. Unique features of H13 hemagglutinin include the occurrence, near the receptor binding pocket, of residues Arg/Lys-227 and Trp-229 (H3 numbering); the significance of these are unknown. The sequence of the HA1-HA2 cleavage site resembles those of avirulent avian influenza viruses. The whale H13 hemagglutinin is similar to those from gulls, supporting the hypothesis that influenza viruses from avian sources can enter marine mammal populations but are probably not permanently maintained there. Antigenic analysis using a panel of monoclonal antibodies suggests that, like other subtypes, H13 viruses are heterogeneous, with different antigenic variants predominating in the eastern versus the western hemispheres.

Amino Acid Sequence↗
PubMed1988

Protection of chickens from lethal influenza infection by vaccinia-expressed hemagglutinin.

To study the immune response of the chicken to specific influenza proteins, we have constructed a recombinant vaccinia virus containing the hemagglutinin gene of influenza A/Turkey/Ireland/1378/83 (H5N8). In mammalian cell culture the hemagglutinin expressed by this recombinant virus was full-length, cleaved into HA1 and HA2 in the absence of trypsin, and transported to the cell surface, confirming that other virus products are not required for cleavage activation. Chickens inoculated through the wing web with the live recombinant virus produced extremely low levels of hemagglutination-inhibiting or infectivity-neutralizing antibody. However, they were protected from lethal H5 influenza virus challenge. Protection extended to the antigenically distinct virulent H5 viruses, Chicken/Pennsylvania/1370/83 and Chicken/Scotland/59. Chemically bursectomized vaccinated chickens were not protected, whereas normal chickens with very low antibody levels (less than 10) obtained by passive transfer were protected in a dose-dependent fashion. This indicates that despite the low antibody titers induced by vaccination, protection was mediated by antibody.

Animals↗
PubMed1987

Defective interfering virus associated with A/Chicken/Pennsylvania/83 influenza virus.

The A/Chicken/Pennsylvania/1/83 influenza virus, isolated from a respiratory infection of chickens, is an avirulent H5N2 virus containing subgenomic RNAs (W.J. Bean, Y. Kawaoka, J.M. Wood, J.E. Pearson, and R.G. Webster, J. Virol. 54:151-160, 1985). We show here that defective interfering particles are present in this virus population. The virus had a low ratio of plaque-forming to hemagglutinating units and produced interference with standard virus multiplication in infectious center reduction assays. Subgenomic RNAs were identified as internally deleted polymerase RNAs. We have confirmed that this virus protects chickens from lethal H5N2 influenza virus infection. This protective effect appeared to be due to the inhibition of virulent virus multiplication. Additionally, subgenomic RNAs derived from polymerase RNAs were detected in 5 of 18 RNA preparations from animal influenza virus isolates. Therefore, defective interfering particles are sometimes produced in natural influenza virus infections, not just under laboratory conditions. These particles may be capable of suppressing the pathogenic effect of virulent virus infections in nature.

DNA-Directed RNA Polymerases↗
PubMed1987

Intracellular localization of the viral polymerase proteins in cells infected with influenza virus and cells expressing PB1 protein from cloned cDNA.

The biosynthesis, nuclear transport, and formation of a complex among the influenza polymerase proteins were studied in influenza virus-infected MDBK cells by using monospecific antisera. To obtain these monospecific antisera, portions of cloned cDNAs encoding the individual polymerase proteins (PB1, PB2, or PA) of A/WSN/33 influenza virus were expressed as fusion proteins in Escherichia coli, and the purified fusion proteins were injected into rabbits. Studies using indirect immunofluorescence showed that early in the infectious cycle (4 h postinfection) of influenza virus, PB1 and PB2 are present mainly in the nucleus, whereas PA is predominantly present in the cytoplasm of the virus-infected cells. Later, at 6 to 8 h postinfection, all three polymerase proteins are apparent both in the cytoplasm as well as the nucleus. Radiolabeling and immunoprecipitation analyses showed that the three polymerase proteins remain physically associated as a complex in either the presence or the absence of ribonucleoproteins. In the cytoplasm, the majority of the polymerase proteins remain unassociated, whereas in the nucleus they are present as a complex of three polymerase proteins. To determine whether a polymerase protein is transported into the nucleus individually, PB1 was expressed from the cloned cDNA by using the simian virus 40 late promoter expression vector. PB1 alone, in the absence of the other polymerase proteins or the nucleoprotein, accumulates in the nucleus. This suggests that the formation of a complex with other viral protein(s) is not required for either nuclear transport or nuclear accumulation of PB1 protein and that the PB1 protein may contain an intrinsic signal(s) for nuclear transport.

Animals↗
PubMed1985

Effect of human alpha A interferon on influenza virus replication in MDBK cells.

To determine the molecular mechanism whereby interferon induces resistance to influenza virus, we began an investigation of influenza virus replication in MDBK cells treated with recombinant human alpha A interferon. Negative- and positive-strand virus-specific RNA accumulation was monitored by blot hybridization with cloned probes. Primary transcription (transcription of infecting viral negative strands by the virion-associated polymerase) was inhibited by interferon treatment of MDBK cells. At moderate levels of interferon treatment (10 U/ml), this inhibition was restricted to transcripts of polymerase genes, whereas at higher levels of interferon treatment (50 U/ml), accumulation of all primary transcripts was markedly inhibited. Secondary transcripts and viral negative strands did not accumulate to any significant extent in interferon-treated MDBK cells. These results suggest that interferon-induced mechanisms which inhibit influenza virus replication in MDBK cells act at the level of primary transcription.

Animals↗
PubMed1984

Expression of defective-interfering influenza virus-specific transcripts and polypeptides in infected cells.

We have previously shown that influenza virus defective-interfering particle (DI) RNAs can be transcribed into polyadenylated complementary RNAs in vitro (Chanda et al., J. Virol. 45:55-61, 1983). In this paper we report that influenza virus DI RNAs can be transcribed into mRNAs in infected cells as well. The DI-specific RNAs (both plus and minus strands) were found to be synthesized in molar excess compared with RNAs of standard virus segments. In addition, two DI preparations (DI3 and DI7) produced novel polypeptides not present in standard virus-infected cells. These novel polypeptides in DI-infected cells were of PB2 origin, as were the major DI RNA species in both DI preparations. Furthermore, these polypeptides were shown to arise from the translation of functional mRNAs transcribed from DI3 and DI7 RNAs and not from either the degradation of PB2 protein or the incomplete translation of PB2 mRNA. Using mixed-infection tests with different DI preparations, we found that the ability of DI to produce detectable novel polypeptides does not necessarily confer any replicative or interfering advantage over other DI which do not produce detectable DI-specific polypeptides. The possible role of DI-specific polypeptides in DI-mediated interference is discussed.

Animals↗
PubMed1983

In vitro transcription of defective interfering particles of influenza virus produces polyadenylic acid-containing complementary RNAs.

Influenza virus defective interfering (DI) RNAs, which originate from polymerase genes by simple internal deletion, can be transcribed in vitro. These DI RNA transcripts contain covalently linked polyadenylic acid, and their synthesis is dependent on ApG or capped RNAs as primers. Furthermore, like the standard viral RNA transcripts, they are complementary in nature and are slightly smaller in size compared with the corresponding DI RNAs. Hybridization of the specific DI RNA transcripts with the corresponding DI RNA segments and analysis of the duplex RNA by gel electrophoresis indicate that they are not incomplete polymerase gene transcripts, but rather the transcripts of the DI RNAs. Since influenza virus DI RNAs contain both the 5' and the 3' termini and transcribe polyadenylic acid-containing complementary RNAs in vitro the mechanism of interference may differ from that of the 5' DI RNAs of Sendai and vesicular stomatitis viruses.

Defective Viruses↗
PubMed1982

Effect of ozonation on the mutagenicity of carcinogens in aqueous solution.

Ozone is a very strong oxidizing agent that may be used in water purification. The effect of ozonation on the mutagenicity of mutagens and/or carcinogens of diverse chemical structures was evaluated as measured by the Salmonella/microsome assay. The effect of ozonation of 36 mutagens and/or carcinogens has been evaluated and the results of 15 reported here. The mutagenicity of polycyclic aromatic hydrocarbons and aromatic amines was inactivated by ozone treatment, while alkylating agents, nitro aromatics, and nitroso compounds were not affected. Ozonation of hydrazines produced mutagenic intermediates that may be susceptible to base-catalyzed hydrolysis. Therefore, depending on the chemical present, ozonation may be useful in the treatment of waters containing organic carcinogens, including drinking water, waste-water effluents, and other aqueous waste materials containing carcinogens.

Alkylating Agents↗
PubMed1982

pH-sensitive mutagenic activity in ozone-treated 1,2-dimethylhydrazine in the Salmonella/microsome assay.

Treatment with ozone inactivates the mutagenicity of many carcinogens in aqueous solution. The colon carcinogen, 1,2-dimethylhydrazine (DMH) has been reported an exception; ozone treatment converts dimethylhydrazine from a non-mutagen into a mutagen. In the Salmonella/microsome assay, the mutagenicity of ozone-treated dimethylhydrazine was dependent on pH. The ozonation product was a strong mutagen in acidic solution but was not mutagenic in basic solution. The mutagenicity of the acidic ozonation product was inactivated by raising the pH of the solution. Unlike untreated dimethylhydrazine, its ozonation product in basic solution was not converted to a mutagen in this ozone-low pH system.

1,2-Dimethylhydrazine↗