Intracellular events in the replication of defective interfering particles of vesicular stomatitis virus.

During a synchronous infection with both wild-type vesicular stomatitis virus (VSV) and the MS-T defective interfering (DI) particle at levels of high interference, total RNA synthesis was both reduced by 75% and shut off early as compared to the VSV infection alone. In the interfered infection the production of both VSV intracellular nucleocapsids and progeny virus was suppressed by 90% while there was a dramatic increase in intracellular MS-T nucleocapsids. There was a linear accumulation of MS-T nucleocapsids for only 5 hr with the maximum rate of synthesis being observed at 3 hr postinfection. The MS-T nucleocapsids contained genome-length, single-stranded 19 S DI RNA and were 40% of the positive (+)- and 60% of the negative (?)-strand sense. Neither the (+)- nor (?)strand of MS-T nucleocapsid RNA contained poly(A) sequences since none of the RNA or its ribonuclease digestion products bound to oligo(dT)-cellulose. We can detect no methylation of the nucleocapsid RNA and the 5′-termini were not blocked since both the (+)- and (?)-strands initiated with pppA.     

Channel catfish virus: physicochemical properties of the viral genome and identification of viral polypeptides

The establishment of a pseudolysogenic state accompanied by a phenotypic conversion in Azotobacter vinelandii strain O by phages A14, A21, A31, and A41 has been identified. Host cells can be recovered from the pseudolysogens by cultivation in phage-specific antiserum. Pseudolysogens continually give rise at a low rate to phage as a result of the occasional initiation of a lytic burst. As a result of the establishment of the pseudolysogenic state the host cells lose their polysaccharide coat, become flagellated and motile and acquire a yellow pigmented appearance. The four phages, although they differ serologically and molecularly, give rise to converted states that are indistinguishable except by the identification of the phage that is produced by it. On repeated subculturing each of the pseudolysogens will give rise to a stable or permanently converted cell that has the phenotype of the pseudolysogen, but from which it is no longer possible to obtain either host cells or phage.     

Factors which influence inactivation of vesicular stomatitis virus by fresh human serum.

Vesicular stomatitis virus (VSV) was inactivated by fresh human serum, but was less susceptible when grown in human cells. The action of fresh serum differed from that of bromelain, thermolysin, or phospholipase C since inactivation by these enzymes did not depend on host origin of the virus, and since the mutant VSV-tl 17 was more susceptible to these enzymes than VSV, although more resistant to fresh human serum. Host cell antigens may be the target for virolysis by fresh human serum since this activity was specifically increased when VSV was treated with heated anticellular sera. Interaction of fresh human serum with VSV allowed access of ribonuclease to the viral RNA. VSV pseudotypes formed with the simian retraviruses, Mason-Pfizer virus (M-P V) and baboon endogenous virus (BeV), were neutralized by the corresponding antibodies to the retraviruses but also showed increased susceptibility to anticellular sera. Excess of host cell antigen may explain the extreme sensitivity to human serum of VSV (BeV) pseudotypes obtained in dog cells, as well as the resistance of VSV (M-P V) prepared in HeLa cells.     

Persistent infection. I Interferon-inducing defective-interfering particles as mediators of cell sparing: possible role in persistent infection by vesicular stomatitis virus.

Defective-interfering (DI) particles have been implicated in modulating the lethal action of infectious virus during persistent infection. However, in the case of vesicular stomatitis (VS) virus, conventional [?]RNA DI particles (nonlethal themseleves) do not block the lethal action of infectious or cell-killing (CK) particles of VS virus, even though no new infectious virus is produced. The discovery of a class of interferon-inducing defective-interfering (DI → IF) particles with covalently linked, self-complementary [±]RNA, and the capacity of a single such particle to induce interferon, coupled with the demonstration that interferon action prevents cell killing by VS virus, led us to postulate that defective-interfering particles of the [±]RNA class present initially or arising during infection might activate the interferon system and prevent CK particle activity and hence contribute to the establishment and possible maintenance of persistent infection in some cell systems. We provide evidence to support this hypothesis: Single cell survival experiments established that GMK-BSC or mouse L cells retain the capacity to form colonies, i.e., are spared from killing, if they are pretreated with interferon-inducing [±]RNA DI-011 particles 24 hr prior to challenge with either homologous or heterologous viruses. Mouse interferon antiserum present during the pretreatment phase eliminated cell sparing. Pretreatment with DI-011 particles of GMK-Vero cells, which lack the capacity to produce interferon, did not spare these cells from the lethal action of VS virus. Activation of the interferon system by the [±]RNA class of defective-interfering particles provides a means whereby normally susceptible cells may survive in the presence of lethal virus — an aspect of persistent infection by VS virus not satisfactorily accounted for by current models.     

Effect of 12-O-tetradecanoyl-phorbol-13-acetate on the replication of Epstein-Barr virus. I. Characterization of viral DNA.

The tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), induces replication of Epstein-Barr virus (EBV) DNA in a virus-producing human lymphoblastoid cell line, P3HR-1, but not in a nonproducer cell line, Raji. A 6-fold increase in EBV genome copies per P3HR-1 cell parallels the increase in percentage of cells synthesizing viral capsid antigen. In situ cytohybridization with EBV-specific cRNA shows that most of the TPA-treated population participates in the virus-productive cycle. In Raji cells there is abortive induction with an increase in cells showing early antigen from <0.01% to approximately 10%, but there is no increase in EBV genome copies per cell. The optimal TPA concentration for induction of viral DNA replication is 10 ng/ml. EBV DNA synthesized in Raji cells superinfected by virus prepared from TPA-induced P3HR-1 cells is increased approximately 15-fold above that of Raji cells superinfected with control virus. The buoyant density of EBV DNA isolated from virus from TPA-induced cells or of DNA from Raji cells superinfected with TPA-induced and control virus is identical; viral DNA from all sources had the same S value. The XhoI restriction endonuclease digestion patterns of TPA-induced viral DNA and control viral DNA were the same as the viral DNA recovered from Raji cells superinfected with TPA-induced and control virus. Some differences were noted in the molar ratios of some of the fragments.     

Inhibition of vesicular stomatitis virus-defective interfering particle synthesis by Shope fibroma virus.

Undiluted passage of vesicular stomatitis virus (VSV) in a line of African green monkey kidney cells results in a cyclic synthesis of standard infectious VSV. This pattern of virus yield is due to the cyclic production of defective interfering (DI) particles [Perrault, J., and Holland, J. J. (1972). Virology50, 148–158; Palma, B. L., and Huang, A. S. (1974). J. Infect. Dis.129, 403–410; Holland, J. J., Villareal, L. P., and Briendl, M. (1976). J. Virol.17, 805–813]. When such cells were infected with Shope fibroma virus (ShFV) prior to serial undiluted passage of VSV, the normal cyclic yield of VSV was altered. Using two criteria for the determination of DI particles, i.e., the interference assay and the detection of physical particles by gradient technique, it was shown that ShFV exerted its effect by inhibiting the synthesis of VSV-DI particles. It is suggested that ShFV affects both the induction and the amplification of DI particles in this system. Experiments also indicate that the ShFV-mediated inhibition of VSV-DI particle synthesis is probably not due to poxvirus-induced inhibition of cellular macromolecular biosynthesis.     

Host range restriction of vesicular stomatitis virus on duck embryo cells.

Vesicular stomatitis virus (VSV) plaque formation and replication are restricted in duck embryo cells compared to chick embryo cells. Mutants of VSV which replicate normally on both chick and duck cells were isolated. The duck-adapted mutant, when passed through chick cells, retains its ability to grow normally on duck cells. This indicates that the ability of this virus to grow on duck cells is due to mutation rather than to host-controlled modification. VSV is restricted in duck cells but not in quail or pheasant embryo cells which follows the evolutionary relationship of these species. Newcastle disease virus and Rous sarcoma virus are restricted in duck cells also. Virus-specific protein synthesis of the wild-type VSV is greatly reduced in duck cells compared to chick cells. A structural protein of the duck cell-adapted mutant is altered.