Nonenveloped viruses

The virus genome We have stated that the virus genome consists of either DNA or RNA, never both. Viruses differ in size, amount, and character of their nucleic acid. Both single-stranded and doublestranded nucleic acid is found in viruses, and the amount of nucleic acid per virion may vary greatly from one virus type to another. In general, in enveloped viruses the nucleic acid constitutes only a small part of the mass of the virus particle (1-2 percent), whereas in nonenveloped viruses the percent of the particle which is nucleic acid is much larger, often 25-50 percent. 

A series of aluminum(III) naphthalocyanines of potential value as PDT sensitizers has been synthesized. Thus, treatment of 2,3-dicyanonaphthalene with aluminum(III) chloride in refluxing quinoline for 2h gave 48% of ClAl(NPc).353,354 Hydrolysis gave HOAl(NPc), from which tri-alkylsiloxy derivatives could be made.354 Although nonenveloped viruses were resistant, various enveloped viruses were inactivated with aluminum(III) complexes of benzonaphthoporphyrazine sulphonic acids as sensitizers.355... 

Natural SPs are effective in inhibiting a wide range of enveloped viruses, whereas nonenveloped viruses are not significantly susceptible to these compounds. The degree of inhibitory activity varies with the compound and the virus. The current status of antiviral studies performed with the human pathogenic viruses more susceptible to these polysulfates is presented in this section. 

Although structural studies of enveloped viruses have lagged behind those of nonenveloped viruses, progress in combining high-resolution cryo-EM results with independently derived atomic structures of virion components has provided pseudo-atomic resolution structures. In terms of whole virus particles, the greatest advances have been accomplished with spherical icosahedral enveloped viruses from the... 

Members of the Parvovirus genus cause a number of diseases in mammals, including enteritis [37, 38] and childhood fifth disease. These nonenveloped viruses have a capsid with a diameter of 255 A that encases a double-stranded DNA genome and infect only cells that are in the S phase [39]. In canine parvovirus (GPV) the T=1 capsid is composed mainly of 60 copies of viral protein 2 (VP2). There is a small amount of VPS in the capsid that is the result of proteolytic cleavage of 17 residues from the amino terminus of VP2. Up to 20% of the 60 copies of VP2 in each capsid are replaced by VPl. VPl is the product of an alternative transcriptional splicing event that places an additional 153 amino acids at the N terminus [15]. No evidence for VPl was observed in the crystal structure [40]. 

STRUCTURAL BASIS OF NONENVELOPED VIRUS CELL ENTRY... 

Nodaviridae, 152, 153, 223 Nodaviruses, 10, 24—26 Nonenveloped virus cell entry, 455-482 Nonicosahedral particles, baculoviruses as, 387—390 Norwalk virus (NV) capsid protein, 14 gastroenteritis and, 25 heterologous expression investigation of, 3... 

Phenolic compounds are active against enveloped viruses but their activity against nonenveloped viruses is variable. Most are active in the presence of extraneous protein and are generally used at 2-5% dilutions. 

Ethyl alcohol and isopropyl alcohol have similar disinfectant properties. They are active against enveloped viruses but their action against nonenveloped viruses is variable. They are used at concentrations of about 70% in water it is necessary to have a wetting agent to assist penetration of the alcohols. Such alcohol solutions may be used to disinfect surfaces and to decontaminate centrifuge buckets. 

Several different plasma-derived factor VEI products are avaUable (see Table 100 ). These products are derived from the plasma of thousands of donors, and therefore potentially can transmit infection. Donor screening, testing plasma pools for evidence of infection, viral reduction through purification steps, and viral inactivation procedures (e.g., dry heat, pasteurization, and solvent detergent treatment) have all resulted in a safer product. No cases of HIV transmission from factor concentrates have been reported since 1986. However, there have been isolated reports of hepatitis C infection with the use of plasma-derived products. Additionally, there have been outbreaks of hepatitis A viral infections associated with plasma-derived products, likely because solvent detergent treatment does not inactivate this nonenveloped virus. Parvovirus has also been reported to be present in both plasma-derived and recombinant factor VIII products. " Finally, there remains concern about the possibility for infection with as yet unidentified viruses that currently used methods would not inactivate. 

As noted previously, enveloped animal viruses are surrounded by an outer phospholipid layer derived from the plasma membrane of host cells and containing abundant viral glycoproteins. The processes of adsorption and release of enveloped viruses differ substantially from these processes In nonenveloped viruses. To Illustrate lytic replication of enveloped viruses, we consider the rabies virus, whose nu-cleocapsld consists of a single-stranded RNA genome surrounded by multiple copies of nucleocapsld protein. Like... 

The viral clearance reduction factor, the common logarithm of the ratio between the total virus loads before and after clearance, is established for viruses known to contaminate the production process [50]. Individual step clearances are combined to obtain the total clearance reduction factor. This reduction factor is used in combination with an assessment of step robustness to classify the step as effective (>4 reduction factor and unaffected by small changes in process variables), moderately effective (4 > reduction factor > 1), or ineffective (<1 reduction factor) with respect to virus clearance [50]. Clearance factors are usually multiplied if the mechanism is different for two separate steps and sometimes are added if the mechanism is same [51]. In other cases, if two independent steps have similar mechanisms of clearance, only one step is included in the summation because virus particles removed via that mechanism would only be expected to be removed in the first step [3, 5]. A total clearance of 12-15 logs is desired for lipid-enveloped viruses and fewer logs for nonenveloped viruses (e.g., polio) [30]. 

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