Host-virus relationship

Peri, B.A. and Watson, D.W. (1948) Studies on host-virus relationships lysogenesis in a strain of Clostridium madisonii. Proceedings of the 48th Annual Meeting of the Society of American Bacteriologists, vol. 1, p. 26. 

Host-virus relationships. 2. Pathology, Cellular. 3. Viruses —Reproduction. I. Series. 

The host cell provides part of the protein synthesis and replication machinery for the phage. That the host cell provides even specific factors and that this aspect of host-virus relationship is still not understood is illustrated by a few observations which will be mentioned only briefly. 

In a relationship of parasitism the population that benefits, the parasite, normally derives its nutritional requirements from the population that is harmed, the host. The host-parasite relationship is characterized by a relatively long period of contact, which may be directly physical or metabolic. Normally, the relation is as specific as for example the viruses, which are obligate intracellular parasites of bacterial, fungal, algal, and protozoan populations. 

Figure 19 Bacteriophages Attach in Order to Penetrate Bacterial Cell. Basic Host Cell - Virus Relationship Established. (Phage. http //en. wikipedia.oig/wiki/File Phage.jpg by Dr Graham Beards http //en.wikipedia. org/wiki/User Graham Beards is licensed under CC BY-SA 3.0 http // creativecommons.org/ licenses y-sa/3.0/) Reference Appendix 2, Explanations to the Figures...

The endoparasite C. sonorensis has evolved with the ability to generate extrachromosomal genetic elements in the form of multiple double-stranded, superhelical DNA molecules. These DNA molecules are amplified in the calyx cell nucleus, packaged into viruses, and secreted in a complex process of viral maturation, which also provides a complex double viral envelope. One viral envelope is assembled in the cell nucleus, and the other is obtained during budding from the calyx cell surface into the oviduct lumen. Viral envelopes, which are derived from cellular membranes, may mediate species-specific virus host cell and tissue interactions. This could be one important aspect of the species-specific endoparasite-host relationship fundamental to parasite survival. 

It is also possible that polydnaviruses were originally virulent in C. sonorensis, but the virus-wasp relationship has evolved toward mutualism (103). Obligate symbiosis enables the host to acquire functions that improve its chances for survival the mutualist also benefits by securing its passage to the host progeny. Polydnaviruses may be optimal mutual-... 

Aciclovir is a member of a group of nucleoside derivatives termed acyclonucleosides, in that there is an incomplete sugar ring. The structural relationship to 2 -deoxyguanosine should be very clear. Aciclovir is converted into its monophosphate by the viral enzyme thymidine kinase - some viruses also possess enzymes that facilitate their replication in the host cell. The viral enzyme turns out to be much more effective than that of the host cell, and conversion is, therefore, mainly in infected cells. The monophosphate is subsequently converted into the triphosphate hy the host cell enzymes. Aciclovir triphosphate inhibits viral DNA polymerase, much more so than it does the host enzyme, and so terminates DNA replication. 

Fraser MJ, Smith GE, Summers MD (1983), Acquisition of host cell DNA sequences by baculovirus relationship between host DNA insertion and FP mutants of Autographa californica and Galleria mellonella nuclear polyhedrosis viruses, Virology 47 287-300. 

Finally, another potential interplay between UVR and viruses occurs when they coexist with their host in a type of mutualistic relationship, where the nucleic acid of the virus is integrated in the genome of the host and is replicated with it (lysogenic state). Ultraviolet C radiation produced by germicidal lamps (max. at 254 nm) has normally been used, among other stressors, to induce the shift from lysogenic to lytic state in a complex mechanism involving the DNA repair SOS system of the host [93]. However, natural or simulated solar UVR seems not to be very efficient in this process [94,95]. 

There are some molecular biologists and biochemists who believe that a total description of the physics and chemistry of the cell would readily extrapolate to a total description of the organism. For example, the entire nucleotide sequence of at least one simple virus is now known. But does such a specification say all there is to say about the properties of the virus Or are there other things to say which, as I believe, can only be specified in terms of the history of the virus as an organism, its relationship to its environment and to its host or potential host cells. 

Abstract The assembly of the N-terminus heptad repeats of the respiratory syncytial virus (RSV) F protein into a trimeric complex that associates with the C-terminus heptad repeats to form a six-helix bundle is a critical step in the process of vims-host fusion and represents an intramolecular protein-protein interaction. Screening campaigns using replicating virus assays have identified several structurally distinct but mechanistically similar chemotypes that interfere with RSV fusion by disrupting the function of the F protein six-helix bundle. This chapter summarizes structure-activity relationships and mechanistic insights associated with the most prominent RSV fusion inhibitors and the key issues in the development of potential clinical candidates. 

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