Cross-packaging

Cross-packaging is the packaging of viral genomes into the virion shell of other viruses. 

Rabinowitz, J. E. et al. (2002). Cross-packaging of a single adeno-associated virus (AAV) type 2 vector genome into multiple AAV serotypes enables transduction with broad specificity. J. Virol. 76, 791-801. 

Because many steps in lentiviral infection (reverse transcription, nuclear transport, and integration) depend on cellular cofactors (65, 66, 68-70), there may be serious limitations in the use of nonhuman lentiviral vectors in primary human tissues. Replication of lentivimses is highly adapted to their natural host, indicating that cross species variability of cellular factors essential for vims replication, and thus vector transduction, may impair the transduction efficiency of nonhuman lentiviral vectors in human cells. These restrictions may be overcome by the use of chimeric lentiviral vectors. Indeed, cross-packaging of FIVRNAby HIV-1 and SIV packaging systems has been demonstrated, and viral proteins were able to... 

Some flexible packaging is fabricated by converters into bags and pouches. Bag material is either small monolayer or large multiwall with paper as a principal substrate. Pouches are small and made from laminations. Bags usually contain a heat-sealed or adhesive-bonded seam mnning the length of the unit and a cross-seam bonded in the same fashion. 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Specifications and Standards Test Methods. Hydroxyethylcellulose is included in the Hst of materials that are in compHance with requirements of the U.S. EDA for use in adhesives and in resinous and polymeric coatings employed on the food-contact surfaces of metal, paper, or paperboard articles, and other substrates intended for use in food packaging as specified in CER 21. HEC made dispersible by cross-linking with glyoxal is cleared only as an adhesive and as a component of paper and paperboard in contact with food. It has not been cleared as a direct food additive. 

The commercial grades available in the 1970s used either zinc or sodium as the cross-linking ion and ranged in melt flow index from 0.4 to 14. The main application of the ionomer resins has been for packaging film. The polymer is particularly useful in composite structures to provide an outer layer with good heat sealability. The puncture resistance of film based on ionomer film has the puncture resistance of a LDPE film of twice the gauge. 

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