David R. Scholl

Rapid antiviral DNA-DNA hybridization assay for human cytomegalovirus.

A rapid DNA-DNA hybridization technique that can be accomplished in 4 to 5 days was compared with plaque reduction assay to determine its reliability in performing antiviral assays for human cytomegalovirus (HCMV). The assay involves lysing infected cells, direct wicking of denatured DNA onto membranes and hybridization using a 125I-labeled HCMV DNA probe. Using ten ganciclovir sensitive clinical HCMV strains for comparison, the DNA hybridization technique correlated well with the plaque assay. Clinical HCMV strains previously identified as resistant to ganciclovir were also readily identified. The DNA-DNA hybridization assay is less tedious and more rapid than plaque reduction assays, and thus, provides an excellent alternative for evaluation of the antiviral activity of drugs against HCMV.

Functional Modification of the Plasmid RP1-specified Pilus by Caulobacter vibrioides

SUMMARY: Caulobacter strains which contain plasmid RP1 are resistant to carbenicillin, kanamycin and tetracycline and can serve as donors of the plasmid, but such R+ strains are not susceptible to the RP1-specific phage PRR1. Since both conjugation and phage PRR1 infection are mediated by the plasmid-specified pilus, the lack of phage binding suggests some functional alteration of the pilus. In this report we demonstrate that RP1 pili are produced by Caulobacter R+ cells, but unlike the RP1 pili produced by PRR1-susceptible strains, the Caulobacter R+ pili do not inactivate phage PRR1. Antibody produced against Caulobacter R+ pili prevents phage PRR1 binding to RP1 pili from PRR1-susceptible strains of Pseudomonas aeruginosa and Escherichia coli, and also inhibits plasmid transfer by those strains. Antibody produced against RP1 pili from P. aeruginosa and E. coli inhibits plasmid transfer both by those strains and by Caulobacter R+ donors. Phage PRR1 rendered non-infectious by RNAase treatment prevents plasmid transfer by P. aeruginosa and E. coli but not by Caulobacter.

Cloning of a Partial Length cDNA Encoding the C‐Terminal Portion of the 75‐77‐kDa Antigen of Trypanosoma cruzi

ABSTRACT It has been suggested that several Trypanosoma cruzi antigens have possible protective epitopes which may be suitable vaccine candidates. We found previously that animals resistant to T. cruzi infection produced antibodies against the 75‐77‐kDa parasite antigen. To test the ability of the recombinant form of this antigen to protect animals from T. cruzi infection, the cDNA which encodes a portion of the 75‐77‐kDa antigen was cloned using a cDNA library constructed in an orientation‐specific bacteriophage expression vector (λgt11) from poly (A)+ RNA of Brazil strain epimastigotes. One clone, named SFS‐40, was selected by screening the library using affinity purified antibodies specific for the 75‐77‐kDa parasite antigen as probe. The cDNA corresponding to the 1.7‐kilobase insert of SFS‐40 was subcloned into plasmid vectors and characterized. The cDNA sequence encodes a polypeptide of about 40 kDa. The putative product of the cDNA was homologous to members of the 70‐kDa stress protein family. When epimastigotes were shifted from 29° C to 37° C, there was no change in the level of SFS‐40 mRNA. In contrast, the 70‐kDa heat shock protein mRNA of the parasite was increased about four fold by this treatment.

Modification of EcoRI restriction sites by Caulobacter vibrioides: Plasmid RP1; endonuclease susceptibility; stalked bacteria

Abstract A comparison of Eco RI digestion profiles of plasmid RP1 isolated from Caulobacter vibrioides WS48 and Escherichia coli CSH29 demonstrated that Eco RI sites were modified by WS48.