Mapping of deletions in the genome of the highly attenuated vaccinia virus MVA and their influence on virulence

Abstract

Different passages of the vaccinia virus strain Ankara (CVA wild-type) during attenuation to MVA (modified vaccinia virus Ankara) have been analysed to detect alterations in the genome. Physical maps for the restriction enzymes HindlII and XhoI have been established. Six major deletions relative to the wildtype strain CVA could be localized. They reduce the size of the entire genome from 208 kb (CVA wild-type) to 177 kb for the MVA strain. Four deletions occurred during the first 382 passages and the resulting variant (CVA 382) displays an attenuated phenotype similar to that of the MVA strain. The deletions are located in both terminal fragments, affect two-thirds of the host range gene K1L and eliminate 3.5 kb of a highly conserved region in the HindlII A fragment. During the next 190 passages leading to MVA two additional deletions appeared. Again, one is located in the left terminal fragment, and the other includes the A-type inclusion body gene. Neither of the deletions appear to participate in further attenuation of the virus. Rescue of the partially deleted host range region with the corresponding wild-type DNA restored the ability of the attenuated strains MVA and CVA 382 to grow in some non-permissive tissue cultures. Nevertheless, the complete host range of the wild-type strain was not recovered. Also, plaque-forming behaviour and reduced virulence were not influenced. From the data presented it may be concluded that the partially deleted host range gene is not solely responsible for attenuation.

Modified vaccinia virus Ankara protein F1L is a novel BH3-domain-binding protein and acts together with the early viral protein E3L to block virus-associated apoptosis

“…Vaccinia virus MVA (cloned isolate F6 at 582nd CEF passage), 42 and MVA-DE3L 15 were routinely propagated and titrated by vaccinia virusspecific immunostaining on BHK-21 cells to determine the numbers of infectious units (IU) per milliliter. Vaccinia virus MVA (cloned isolate II new ) 42,43 and MVA-DF1L were amplified and titrated on CEF.…”

“…Vaccinia virus MVA (cloned isolate II new ) 42,43 and MVA-DF1L were amplified and titrated on CEF. In experiments using MVA-DE3L, the MVA isolate F6 was used as a control, in experiments with MVA-DF1L, the control was MVA isolate II new .…”

Vaccine properties of a novel marker gene-free recombinant modified vaccinia Ankara expressing immunodominant CMV antigens pp65 and IE1

“…Analysis of the MVA genome revealed six major deletions [41]. Deletions II and III were developed and widely used for insertion of foreign genes to create recombinant MVA (rMVA) via homologous recombination [36,42].…”

“…However they all have the common problem of limited capacity to incorporate foreign genes. In contrast, MVA has the potential for large foreign gene capacity because the genome suffered six major deletions totaling nearly 30Kb [2], during its passage in CEF [41]. There is ample space to insert multiple genes from CMV involved in multiple stages of the virus life cycle as an approach to disable virus transmission.…”

Generation and evaluation of a recombinant modified vaccinia virus Ankara vaccine for rabies

“…During passage on these cells, the virus adaptation resulted in six major genomic openUP (June 2007) deletions of about 31,000 base pairs (or 15% of the wild type Vaccinia virus Ankara genome) [31] and [32]. Most of the deleted and truncated genes have been shown to be immuno-regulators, or involved in the host range of the virus and multiple gene defects will have to be corrected for reversion to wild type [32], [33], [34] and [35].…”