User:Nikkicalvert/Cowpox

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The genome for the CPXV is over 220kbp. This makes it the largest genome in the Orthopoxviral species. It can be divided into three different regions. There are two end regions called R1 and R2 and a main central region that is roughly half of the size of the genome. There are also inverted terminal repeats that are located at the terminal sites of the genome and measure around 10kbp. These inverted terminal repeats can then be divided into two more distinct regions. The first section is around 7.5kbp long and includes a coding region. The other section includes a terminal region that can be repeated up to as many times as thirty and is composed of 50 nucleotides. The CPXV genome encodes only 30-40% of products of which are involved in the pathogenesis of the virus. The CPXV genome has the most complete set of genes out of all of the orthopoxviruses. This unique feature of CPXV makes it ideal to be able to mutate into different strains of the virus. It is a double stranded DNA virus. The virus does have an envelope that surrounds the virion. The cowpox's genome allows the virus to encode its own transcription machinery along with its own DNA replication machinery. The replication then takes place in the cytoplasm after the virus is in the cell and the virion is uncoated. The virion is then assembled and released from the host cell.

The genome is arranged so that both of the ends contain the genes responsible for evading the defenses from the immune system of the host which is only activated in the extracellular portion. These receptors are able to be stopped by cytokine and chemokine secretion by blocking the cytokine and chemokine found extracellularly. This is the process responsible for attachment and entry of the virion into the host cell. Because of the large size of the genome, it makes the virus more likely and capable to fight back against the immunes system defenses. Out of all of the poxviruses, CPXV has the most cytokine responses that fight back against the immune system. It encodes cytokine receptors such as TNF, CrmB, CrmC, CrmD, and CrmE proteins. Another set of receptors that CPXV have are lymphotoxins such as IL-1ß, IFN-y, IFN 1, β-chemokines, and IL-18. However, not all of the receptors of CPXV are still not known. CPXV also encodes four tumor necrosis factors (TNF) and lymphotoxin which are the biggest group of homologous receptors for the virus. These receptors play a crucial role that are involved with the immune system.

CPXV has two different types of inclusion bodies. All of the poxviruses have basophilic inclusions also called B-type inclusion bodies. The B-type inclusion bodies contain the factory where the virus produces necessary elements for the replication and maturation of the virion. CPXV has another inclusion body that is unique to only some chordopoxviruses called acidophilic inclusion bodies also called A-type inclusion bodies (ATIs). The ATIs are encoded by the cpxv158 gene and is then made the protein ATIP which is a late protein. However, the importance of these ATIs in the life cycle are still not well known or understood and research is still being done to better understand them. It is known that replication can still continue without the cpxv158 gene, and that the replication cycle shows no difference between a fully encoded virion versus the virion that had deleted cwpx158 gene. However, with studies done on mice, the lesions that were caused by the CPXV-BR△ati were able to heal faster due to less tissue that was lost than the CPXV-BR lesions that took longer to heal and lost more tissue. This suggests that this gene helps supports the idea that ATIs are partly involved in how the host responds to the virus infection.

Another way that the virus is able to control and infect the host is by regulating cellular signaling pathways. During the infection, CPXV is known to use MEK/ERK/1/2/Egr-1, JNK1/2, and PI3K/Akt pathways. Some of these pathways are not unique only to CPXV, but how they function in response to the host is unique to this virus.

One notable protein in the CPXV is the p28 protein. It is made up of 242 amino acids and contains two domains, and N terminal KilA-N and a C-terminal RING domain. One of those domains, the N-terminal KilA-N domain, allows for DNA to bind to it. The KilA-N domain facilitates this p28 protein that is translated early in the replication cycle in the cytoplasm and is then located in the cytoplasm for the rest of the life cycle of the virus. There is current research still being done to determine if the p28 protein could be a requital for an essential macrophage factor that is needed for the DNA replication.