Replication of phage RNA

The West Nile virus mutant spectrum is host-dependant and a determinant of mortality in mice

To define the impact of mosquitoes and birds on intrahost WNV population dynamics, the mutant spectra that arose as a result of 20 serial in vivo passages in Culex pipiens and young chickens were examined. Genetically homogeneous WNV was serially passaged 20 times in each host. Genetic diversity was greater in mosquito-passaged WNV compared to chicken-passaged WNV. Changes in the viral consensus sequence occurred in WNV passaged in mosquitoes earlier and more frequently than in chicken-passaged WNV. Analysis of synonymous and nonsynonymous variation suggested that purifying selection was relaxed during passage in mosquitoes. Mortality in mice was significantly negatively correlated with the size of the WNV mutant spectrum. These studies suggest that mosquitoes serve as sources for WNV genetic diversity, that birds are selective sieves, and that both the consensus sequence and the mutant spectrum contribute to WNV phenotype.

Viral double-stranded RNA, cytokines, and the flu

The symptoms of the flu, such as fever, drowsiness, and malaise, are the sole means by which this common clinical syndrome is defined. The syndrome is usually the first clinical manifestation of both acute bacterial and viral infections. In the case of acute bacterial infections, several proinflammatory cytokines induced by bacterial products have been implicated as the causative agents of the flu syndrome. Viruses induce similar cytokines to bacteria, plus substantial amounts of interferon-alpha (IFN-alpha), although the direct association of these cytokines with the viral flu syndrome is less clear. Furthermore, the viral inducer(s) of cytokines has not been defined. The best candidate cytokine inducer associated with a majority of viral infections is virus-associated double-stranded RNA (dsRNA). This review examines the essential physical properties of toxic dsRNA, the cytokines induced by it, its viral and cellular sources, evidence for its presence in infected cells, its quantities in normal and infected cells, its cytotoxic mechanisms, and its cell-penetration properties. Toxic effects of viruses and dsRNA are compared. Energetics and extraction artifact issues are also discussed. Whereas most research on dsRNA toxicity has employed synthetic dsRNA, studies with virus-associated dsRNA are featured when available. Finally, a model for how viral dsRNA might initiate systemic disease is presented.

Anti-nucleic acid antibodies in systemic lupus erythematosus patients and their families. Incidence and correlation with lymphocytotoxic antibodies

Anti-RNA antibodies were found in 82% of 28 systemic lupus erythematosus (SLE) probands and in 16% of 124 of their family members. The incidence in 76 control family members was only 5%. In the SLE family members, the antibodies were found exclusively in 21% of the 94 close household contacts of the probands. The incidence of anti-native DNA (nDNA) antibodies was 68% for the SLE probands. The incidence of anti-nDNA antibodies in close household contacts of the probands was 6%, which was not significantly different from the 1% incidence found in control families. Lymphocytotoxic antibodies occurred in 57% of the SLE family members as a whole and in 68% of the close household contacts. In the SLE probands, lymphocytotoxic antibodies correlated with anti-single-stranded RNA (poly A) and anti-nDNA but not with anti-double-stranded RNA (poly A-poly U). On the other hand, lymphocytotoxic antibodies in the household contacts correlated with anti-double-stranded RNA (poly A-poly U) but not with anti-poly A or anti-nDNA. The anti-RNA antibodies were present in consanguineous household contacts but not in nonconsanguineous household contacts. These findings strengthen the hypothesis that both an environmental agent, possibly a virus, as well as the genetic response are important in the pathogenesis of SLE. Family members may therefore be a logical population in whom to search for specific antibodies to a viral agent.

Structure of the poly(G) polymerase component of the bacteriophage f2 replicase

A rifampicin-resistant poly(G) polymerase has been purified from f2 sus 11-infected cells. The poly(G) polymerase is believed to represent part of the f2 replicase on the basis of several criteria. It is present only in infected cells and shares the characteristic rifampicin resistance of crude f2 replicase activity. Partially purified poly(G) polymerase preparations exhibit replicase activity, synthesizing f2 "lus"strand RNA from denatured, partially double-stranded f2 RNA template. Highly purified poly(G) polymerase preparations, although lacking replicase activity, contain a protein which is electrophoretically identical to the protein product of the viral replicase cistron.

The nucleotide sequence at the 5'-terminus of the Q RNA minus trand

The sequence of the first 52 nucleotides at the 5'-end of the Qbeta minus strand has been determined and found to be complementary in an antiparallel fashion to the 3'-terminal region of the Qbeta plus strand. There are few similarities between the corresponding sequences of Qbeta plus and minus strands; however, both have a hydrogen-bonded loop close to the 5'-end. The sequence of the 3'-terminal region of the plus strand was deduced: there are no termination signals within the last 32 nucleotides. A notable homology exists between the 3'-ends of Qbeta and R17 RNA.

In vitro product of a ribonucleic acid polymerase induced by influenza virus

The ribonucleic acid (RNA)-dependent RNA polymerase induced in the microsomal fraction of cells infected with influenza virus synthesized a mixture of single-and double-stranded RNA in vitro. The single-stranded RNA sedimented mainly in the 8S region on sucrose density gradients, with a smaller proportion of the RNA sedimenting at 18S. This sedimentation pattern corresponds closely to that of incomplete influenza virus RNA. The double-stranded RNA formed in vitro sedimented at 11S, but molecules which may be replicative intermediate, sedimenting at 14 to 20S, were also detected in the in vitro reaction product. Similar species of RNA were detected in vivo by pulse-labeling infected cells at the time of polymerase harvest, but the proportion of each RNA species was different, most of the RNA being single-stranded and sedimenting in the 18S region. An 11S double-stranded RNA was also synthesized in vivo. Pulse chase analysis of the double-stranded RNA synthesized in vitro showed that most is stable, and only a small proportion turns over during the reaction. A proportion of the RNA formed in vitro could be annealed to RNA formed in infected cells and to RNA extracted from purified virus.

Immunochemical measurement of double-stranded RNA of uninfected and arbovirus-infected mammalian cells

A quantitative complement fixation assay which specifically measures double-stranded RNA has been used to study this RNA extracted from uninfected and arbovirus-infected cells. The double-straned RNA of the uninfected BHK-21 cells sedimented in the 12S region in sucrose gradients. The double-stranded RNA of Sinbis virus-infected cells, as measured immunochemically, included a predominant peak at 12S, a smaller 18S peak, and polydisperse material extending into the 26-30S region. All classes of this RNA detected immunochemically showed a sharp thermal denaturation curve, and increased in amount progressively during infection, with the 12S peak predominant at all times.

Complementary nuclear RNA's of murine sarcoma-leukemia virus complex in transformed cells

The high molecular weight RNA (S(20,w) = 69S) of murine sarcomaleukemia virus (MSV-MLV) complex dissociated into 37S subunits when heated to 95 degrees C for 2 minutes. Specific annealing tests revealed that the viral RNA had complementarity with two heterogeneous RNA species from the nuclei of cells (78 A1) transformed by and chronically infected with this virus complex. The two nuclear RNA species that hybridized with the viral RNA had sedimentation constants ranging from 31-36S and 18-22S, respectively. There was no specific annealing between viral RNA and the cytoplasmic RNA of the 78 A1 cells. The detection of the complementary RNA strands of MSV-MLV suggests that this oncogenic virus complex may replicate in a fashion similar to that of the non-oncogenic RNA viruses, but may differ in that the complementary strands are found in the nucleus rather than in the cytoplasm of the transformed cells.

Replication of viral RNA: RNA synthetase from Escherichia coli infected with phage MS2 or Qb

An RNA synthetase is formed in Escherichia coli after infection with bacteriophages containing RNA. Specific annealing techniques revealed that, from the very outset of the reaction in vitro, the partially purified enzyme-template complex synthesizes parental-type plus strands, namely, MS2-RNA when isolated from cells infected with MS2 phage and Q(beta)-RNA in the case of cells infected with Q(beta) phage. This is in contrast to the situation found with Q(beta) replicase primed with Q(beta)-RNA, where the initial product is the complementary strand.