Overexpression (Oex) and knockdown (KD) studies are indispensable approaches for basic and clinical research to determine the role of a gene. The research field has been revolutionized by the discovery of RNAi technology in the last century. However, accessibility of such studies in vitro are always dependent on the ability to bring either the gene of interest (GOI) or a specific shRNA/siRNA sequence into the desired cell system; summarized as ‘gene delivery’. 

Many different methods of gene delivery were developed which can be divided into two main categories, viral and non-viral. 

      Non-viral methods include physical methods such as microinjection or electroporation and chemical methods, such as lipofection. However, these methods have their limitations since many cell types are not accessible by this kind of targeting and, as a major drawback, reproducible results are hard to achieve due to deviating transfection rates.

      Viral gene delivery methods make use of the natural characteristics of viruses and therefore have a multitude of advantages: 

• Viruses are naturally evolved vehicles which transfer their genes into a host very efficiently. This makes them desirable for engineering virus vector systems for gene delivery. 

• Viruses exhibit different host ranges depending on which family they belong to. This tremendous diversity allows for the best possible gene delivery system for any specific scientific approach and any specific cell system. 

• The host can either be a specific cell type for in vitro studies or it can even be a specific animal model for in vivo studies.

SIRION BIOTECH`s expertise is genetic engineering by using a broad range of viral vector technologies. 

• Viral Vectors developed and used by SIRION BIOTECH are based on RNA and DNA viruses thus being able to process different genomic structures and host ranges.

• In addition, viral vectors developed by SIRION BIOTECH are replication deficient which guarantees vector safety.

• By refining vector design and virus production, expression properties are optimized and virus retargeting achieved.  

In summary, this viral expertise gives you a perfect tool for gene delivery in almost all cell systems in vitro and gene engineering in vivo, respectively.

Let us start with different viral vectors serving as the main players:

Adenovirus (AV): 

Adenoviruses are non-enveloped double stranded DNA viruses (36 kb) with an icosahedral structure. In total, more than 50 different human serotypes are known so far. Most of the adenovirus mediated diseases in humans are mild acute respiratory, gastrointestinal and ocular infections with a high rate of infection.

Recombinant adenoviruses have become a standard tool in gene delivery in vitro and in vivo, vaccination and gene therapy. Several features of AV biology have made such viruses the vectors of choice for these applications. 

• A striking advantage is their highly efficient gene knockdown and overexpression potential into nearly all eukaryotic cells, even primary cells independently whether dividing or not. 

• Since viral titers can be titrated easily, highly reproducible results can be obtained and hence, standard variations minimized. 

• Adenoviral gene delivery is transient, since after infection, DNA is transferred into the nucleus and persists in epichromosomal DNA which is not accessible for the host replication machinery.

SIRION BIOTECH`s adenoviral vector platform is based on the genome of the human adenovirus serotype 5 (Ad5). The company ‘s proprietary AdenoONE Bac recombination system combines both the positive and the negative selection. This restricts the number of recombination events to 1, resulting in a cloning efficiency higher than 98%. Furthermore, patent pending BAC technology guarantees production times of less than 6 weeks from cloning to final virus preparation and highest product purity. 

Lentivirus:

Lentivirus is a genus of slow viruses of the Retroviridae family characterized by a long incubation period. A prominent member of this genus is the “human immunodeficient virus” (HIV). Lentiviruses are enveloped viruses with a single stranded RNA genome. Special features are the viral proteins Reverse Transcriptase and Integrase which enable the transcription from RNA into DNA followed by stable and random integration into the host genome. These remarkable gene delivery properties combined with cell entry properties can also transduce non-dividing cells, and make them highly attractive as gene modification tools. 

SIRION BIOTECH`s lentiviral vector platform allows for constitutive as well as inducible gene modification. It offers a reliable system for highest gene overexpression or knockdown from vector cloning to a functional tested stable cell pool in less than 6 weeks.