Development of a live cell culture camelpox vaccine.

A Saudi isolate of camel orthopoxvirus was serially propagated on monolayers of camel kidney cell cultures. The attenuation of the 78th passage was tested in two susceptible camels. Two other susceptible camels were inoculated with vaccinia virus four times propagated in camel kidney cell cultures. The four inoculated camels showed no postinoculation clinical symptoms and formed neutralizing antibodies against both the camel orthopox and vaccinia viruses. No postchallenge clinical symptoms were observed in these four camels, while two non-inoculated contact control camels showed typical symptoms of generalized camelpox. These results indicated the safety and potency of the 78th passage of the Saudi isolate of camel orthopoxvirus (designated Jouf-78) to be used for production of live attenuated cell culture camelpox vaccine. The field testing of the vaccine was carried out on two farms using at least 10(3) TCID50 as a recommended field dose. None of the inoculated camels showed any postvaccination reaction and the serological tests showed seroconversion of many vaccinated field camels. The relationship between camel orthopoxvirus and vaccinia virus as well as the advantages of the live attenuated camelpox vaccine are discussed.     

D-loop formation by Brh2 protein of Ustilago maydis

Brh2, the ortholog of the BRCA2 tumor suppressor in Ustilago maydis, works hand in hand with Rad51 to promote repair of DNA by homologous recombination. Previous studies established that Brh2 can stimulate DNA strand exchange by enabling Rad51 nucleoprotein filament formation on replication protein A-coated ssDNA. But, more recently, it was noted that Brh2 has an inherent DNA annealing activity, raising the notion that it might have roles in recombination in addition to or beyond the mediator function. Here, we found that Brh2 can autonomously promote the formation of D-loops in reactions with plasmid DNA and homologous single-stranded oligonucleotides. The reaction differs from that catalyzed by Rad51 in having no requirement for cofactors or preloading phase on ssDNA. D-loop formation was most effective when Brh2 was mixed with plasmid DNA before addition of single-stranded oligomer. D-loop formation catalyzed by Rad51 was also enhanced when Brh2 was premixed with plasmid DNA. Brh2 rendered defective in Rad51 interaction by mutation in the BRC element was still capable of promoting D-loop formation. However, the mutant protein was unable to enhance the Rad51-catalyzed reaction. The results suggest a model in which Brh2 binding to plasmid DNA attracts and helps capture Rad51-coated ssDNA.