**Author details**

developed. However, although genetic engineering of baculoviruses seems to be a thoroughly explored area, much work is still required to fully exploit the advantages of the system.

100 Current Issues in Molecular Virology - Viral Genetics and Biotechnological Applications

Vectors and cells with many advantageous characteristics have been developed; yet, it would be tantalizing to assemble all these features in a single system. As mentioned before, the addition of an IRES to the transfer vector to couple the recombinant ORF to an essential BV ORF enhanced the genetic stability of the recombinant virus providing sustained recombinant protein expression. However, this feature is still not commercially available and is not compatible with many commercial systems. Other alternatives that have been explored and may be assembled in new generation systems include: selection by rescue of a lethal gene deletion, deletion of baculovirus chitinase and cathepsin, expression of chaperones and other

The use of transgenic cell lines for expression of recombinant proteins is a convenient alter‐ native to baculovirus infection, since the protein is not expressed in an infection context. Selection systems for the generation of transgenic insect cell lines may be optimized. Systems based on site‐specific recombination would increase the rate of transgenic cell generation, thus simplifying clonal cell isolation. Negative selection systems should be explored as well. Additionally, the development of inducible expression systems would be very convenient,

The improvement of baculovirus bioinsecticides by means of genetic engineering is a chal‐ lenging subject. Genetic stability of recombinant baculovirus is an issue, and it is addressed by strategies such as the addition of an IRES (as mentioned before) and by deleting small regions with high recombination rates. Many genes from various sources are being tested for their ability to increase baculovirus biopesticidal propierties, although small RNA‐mediated silencing will probably emerge as an important alternative to foreign gene expression ap‐ proach. Host range modification is even more challenging. To address this question a system‐ atic study could start by replacing each of the baculovirus genes with related baculovirus homologs in search of functional complementation. Other various approaches may be envisaged. Also, bioinformatics studies in search of genes subjected to positive pressure are valuable to provide candidates of host‐specific interaction genes. These bioinformatics studies should be updated with the recently sequenced baculovirus genomes. The use of baculovirus to transduce mammalian cell lines and mammalian organism bring baculovirus in the gene therapy and vaccine fields. One of the most challenging objectives in this area is the program‐ ming of viral particles to target specific tissues or cell types. In this direction, the replacement of the baculovirus fusion protein by other fusion proteins have shown to modify baculovirus BV tropism, and the development of targeted baculovirus is crucial for exploiting their

From this overview of the field, it is clear that there is room for many strategies and approaches

to improve the various applications of genetically engineered baculoviruses.

folding proteins and expression of mammalian glycosylation pathway proteins.

since they are convenient for expression of proteins that affect cell physiology.

potential as gene therapy vectors.

Santiago Haase, Leticia Ferrelli, Matías Luis Pidre and Víctor Romanowski

\*Address all correspondence to: shaase@biol.unlp.edu.ar

Instituto de Biotecnología y Biología Molecular, Universidad Nacional de la Plata, Conicet, Argentina
