Viral surface proteins

Vaccine candidates are based on the two viral surface proteins, gD and gB (80). Recombinant methods are used to express the proteins, either in Chinese hamster ovary (CHO) cells or in baculovims. The proteins are purified as subunits and formulated with different adjuvants. Clinical trials with these vaccine candidates have been performed, but the results to date have not been encouraging. 

Gripon P, Cannie I, Urban S (2005). EfScient inhibition of hepatitis B virus infection by acylated peptides derived from the large viral surface protein. J Virol 79 1613-1622 Harris RS, Liddament MT (2004) Retroviral restriction by APOBEC proteins. Nat Rev Immunol 4 868-877... 

The viral surface protein, gp 120, is capable of binding to a specific site on the CD4 molecule, found on the surface of susceptible cells (Table 13.10). Some CD4 negative cells may (rarely) also become infected, indicating the existence of an entry mechanism independent of CD4. 

Antiviral mechanisms (A). The organism can disrupt viral replication with the aid of cytotoxic T-lymphocytes that recognize and destroy virus-producing cells (viral surface proteins) or Ltillmann, Color Atlas of Pharmacology... 

Figure 11.29 Viral receptors. Influenza virus targets cells by binding to sialic acid residues (purple diamonds) located at the termini of oligosaccharides present on cell-surface glycoproteins and glycolipids. These carbohydrates are bound by hemagglutinin (interaction circles), one of the major proteins expressed on the surface of the virus. The other major viral surface protein, neuraminidase, iis an enzyme that cleaves oligosaccharide chains to release the viral particle at a later stage of the viral life cycle.

RSV is an enveloped vims that has been classified into subgroups A and B based on serological differences in the viral surface proteins [21, 54, 55] The genome is comprised of a 15,222 nucleotide, nonsegmented negative strand of RNA that encodes for ten viral proteins, as summarized in Fig. 2. The F (fusion),... 

Transgenic animals have also been con sidered for the production of vaccines GTC Biotherapeutics is currently working with the National Health Institute to devel op a malaria vaccine based on the produc tion of the viral surface protein antigen MSP-1 in goat milk. This antigen is diffi cult to express in conventional recombi nant production systems. 

The modern subunit vaccines, first marketed in 1987, were made by recombinant DNA techniques described earlier in this chapter. Because this vaccine consists solely of the viral surface protein or antigen to which the immune system responds, there is no risk for infection with HBV. 

B. Genetically modified eukaryotic cells that synthesize and secrete viral surface proteins. 

Because viruses contain RNA and not DNA, replication of viral genetic material is not subject to the same error-checking and repair mechanisms as is cellular DNA. Thus, mutations in viral RNA are relatively more common, and viruses, should they be able to survive the mutations, can evolve rather quickly to circumvent cellular or therapeutic drug antiviral countermeasures. Antiviral defenses oftentimes recognize viral surface proteins as foreign bodies, and deal with them accordingly. Cytokines... 

The fusion of liposomes with cells is envisioned to deliver their contents directly to the cytoplasm [15,26]. However, whereas the fusion is an essential cellular process in endocytosis, it appears that the liposome fusion with the cells occurs very rarely and is enhanced by reconstitution of viral surface proteins. Therefore, it is apparent that this process is largely controlled by membrane protein of a cell or virus. This can be done not by a simple fusion of bilayers with cells but by incorporating fusogenic proteins or, in vitro, addition of fusogens. 

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