Initiation rate of adenovirus DNA synthesis in infected cell

Modelling heterogeneity in viral-tumour dynamics: The effects of gene-attenuation on viral characteristics

The use of viruses as a cancer treatment is becoming increasingly more robust; however, there is still a long way to go before a completely successful treatment is formulated. One major challenge in the field is to select which virus, out of a burgeoning number of oncolytic viruses and engineered derivatives, can maximise both treatment spread and anticancer cytotoxicity. To assist in solving this problem, an in-depth understanding of the virus-tumour interaction is crucial. In this article, we present a novel integro-differential system with distributed delays embodying the dynamics of an oncolytic adenovirus with a fixed population of tumour cells in vitro, allowing for heterogeneity to exist in the virus and cell populations. The parameters of the model are optimised in a hierarchical manner, the purpose of which is not to obtain a perfect representation of the data. Instead, we place our parameter values in the correct region of the parameter space. Due to the sparse nature of the data it is not possible to obtain the parameter values with any certainty, but rather we demonstrate the suitability of the model. Using our model we quantify how modifications to the viral genome alter the viral characteristics, specifically how the attenuation of the E1B 19 and E1B 55 gene affect the system performance, and identify the dominant processes altered by the mutations. From our analysis, we conclude that the deletion of the E1B 55 gene significantly reduces the replication rate of the virus in comparison to the deletion of the E1B 19 gene. We also found that the deletion of both the E1B 19 and E1B 55 genes resulted in a long delay in the average replication start time of the virus. This leads us to propose the use of E1B 19 gene-attenuated adenovirus for cancer therapy, as opposed to E1B 55 gene-attenuated adenoviruses.

Strands hybridize in postreplicative adenovirus overlap recombination

We describe a postreplicative mechanism for adenovirus overlap recombination. An adenovirus minichromosome system was used to study overlap recombination driven by adenovirus DNA replication. Crossing-over appeared to occur equally at, but not within, the borders of the overlap between partner molecules. We propose that recombination in the minichromosome system proceeds through an intermediate formed by direct hybridization of complementary sequences on displaced strands generated by adenovirus-specific DNA replication. Some, but not all, heterologous regions in the intermediate are susceptible to mismatch correction. This pathway is intrinsically nonreciprocal and differs significantly from other adenovirus recombinational mechanisms that have been described previously.

Analysis by in situ hybridization and autoradiography of sites of replication and storage of single- and double-stranded adenovirus type 5 DNA in lytically infected HeLa cells

The distribution in the different compartments of infected nuclei of double-stranded (ds) and single-stranded (ss) adenovirus type 5 (Ad5) DNA and of the sites of viral DNA replication were examined on thin sections of Low-icryl-embedded material. The DNA is visualized with a biotinylated viral probe and immunogold labeling of biotin, and its replication is monitored by high-resolution autoradiography after short pulses with tritiated thymidine. The first detectable sites of viral DNA, named early replicative sites, contained all the ss and ds viral DNA and viral replicative activity. At a later stage of nuclear transformation, they gave rise to two new structures. The compact fibrillar ssDNA accumulation sites enlarged greatly and became transformed functionally to become a transient site of accumulation of large numbers of ss replicative intermediates. Double-stranded viral DNA and its replicative activity shifted primarily into immediately surrounding fibrillogranular peripheral replicative zones. Ad5 DNA replication continues in the ssDNA accumulation sites but it is intermittent, whereas in the peripheral replicative zones it is continuous. Still later in infection, a single, large, centrally located mass of dense fibrils, the viral genome storage site, developed in each nucleus which proved to be the main site of storage of nonreplicating, nonencapsidated, ds viral genomes. We discuss the possible distribution of the various viral DNA replicative intermediates among these virus-induced intranuclear structures.