Characterization and Mixed Infections of Three Strains of Vaccinia Virus: Wild Type, IBT-resistant and IBT-dependent Mutants

Abstract

SUMMARYThe characteristics of IBT-dependent (IBT D) and IBT-resistant (IBT R) mutants of vaccinia virus were compared with those of the wild type (wt) strain. The mutants did not differ from the wild type strain by their sedimentation in sucrose gradients. Minor differences in the polypeptide composition of the virus particles and in the neutralization of the three virus strains by anti-vaccinia human immunoglobulin were observed. Mixed infections of the viruses in HeLa cells enabled the growth of the strains under their unfavourable conditions (wt in the presence of IBT and IBT D in the absence of IBT).

Vaccinia Virus Envelope H3L Protein Binds to Cell Surface Heparan Sulfate and Is Important for Intracellular Mature Virion Morphogenesis and Virus Infection In Vitro and In Vivo

“…Processing of P4a and P4b proteins has been thought to be essential for the formation of IMV, since chemicals that inhibit such cleavages, directly or indirectly, blocked virion production (8,33,61). Inactivation of F18R, I7L, and L1R gene expression resulted in no core protein processing, and morphogenesis was blocked at IV conversion to IMV (15,41,65).…”

Proteolytic maturation of vaccinia virus core proteins: identification of a conserved motif at the N termini of the 4b and 25K virion proteins

“…The cleavage of the P4a, P4b and P25K precursor proteins during VV morphogenesis is apparently an obligatory reaction, because drugs that inhibit cleavage, either directly or indirectly [e.g. rifampicin (Katz & Moss, 1970b;Moss & Rosenblum, 1973;Miner & Hruby, 1989), a-amanitin (Villarreal et al, 1984), nicotinamide (Child et al, 1988) or isatin-fl-thiosemicarbazone (Katz et al, 1973)], block virus replication, suggesting that proteolytic processing plays a key role in poxvirus development. Very little is known concerning the pathways, biochemistry or mechanisms by which the VV core protein precursors P4a, P4b and P25K undergo proteolytic maturation during infection.…”

The Thiosemicarbazones

“…F.III). The IBT-dependent mutant was found to be able to grow in the absence of IBT during mixed infection with WT or IBT-resistant viruses (KATZ et al 1973c). Mode of action studies showed that the IBT-dependent mutant was blocked in its replication cycle in the absence of IBT at the same place the WT was blocked in its presence (Sect.…”

“…H) contain copper. In this regard it is of interst to note that IBTresistant mutants of both vaccinia and rabbitpox virus lose their resistance to the drug when grown in the presence of the wild-type virus (ApPLEYARD and WAY 1966;KATZ et al 1973c). …”