VirusTech Core Facility

Viral vectors are a key technology for researchers, since it allows the delivery in an efficient and reproducible manner of genes into cells in order to label specific cohorts, control neural activity, as well as gain/loss-of –function experiments to test the role of different genes in cellular processes. The production of viruses requires special expertise and installations, as well as work permits specifically designed for each lab and virus.

The core facility specializes in the production and concentration of Lentiviral and Adeno Associated Viruses (AAVs), but it aims to develop and optimize the production of other types of viruses such as Adenovirus (AV), retroviruses, rabies virus and Herpes simplex viruses (HSV).

The VirusTech Facility is a newly created core facility directed by Dr. Emma R. Andersson and Dr. Jens Hjerling-Leffler, and managed by Dr. Albert Blanchart, located at the Department of Cell and Molecular Biology (CMB), C5.

Its primary purpose is to produce and distribute quality viral vectors to our fellow researchers within Karolinska Institutet and investigators world-wide. The VirusTech facility is a non-profit facility hosted and sponsored by StratNeuro, that produces viral vectors on a fee-for-service basis, in accordance with KI policies for core facilities. Its primary goal is to serve the investigators at KI, but services are also available to other academic centers within Sweden and world-wide.

VirusTech Core Facility Images

Type of Viruses offered by us to your research

The VirusTech Facility offers both Lentiviruses and Adeno Associated Viruses (AAV), each of which has different capabilities, weakness and strengths (see table below).

The core facility also offers consulting in order to help researchers to decide which type would fit their need for a specific project.

Vector Lentiviral AAV
Family Retroviridae Parvoviridae
Cargo ssRNA ssDNA
Packaging capacity (kB) 7-9 4-5
Chromosomal integration Yes No
Infects post-mitotic cells Yes Yes
Chance of oncogene activation Yes No

Lentiviral Vectors 

These viruses belong the family retroviridae, subfamily Orthoretroviridae, genus Lentivirus, characterized for long incubation periods (lente-, Latin for “slow”). The virions (or virus particles) are enveloped, spherical and within a size range of 80-100 nm in diameter. Inside the envelope (a lipid membrane derived from portions of the host cell membranes (phospholipids and proteins), but include some viral glycoproteins) resides the nucleocapsids or core where the single strand of viral RNA is packaged. One of the most striking features of this virus, from the retroviridae family, is its ability to infect both dividing and non-dividing cells and its ability to integrate a significant amount of viral RNA into the DNA of the host cell, which qualifies them as one of the most efficient methods for gene delivery.

  • Require BL2 Containment
  • Can theoretically carry payload up to 9 Kb (10 and 11 Kb have also been reported)
  • Safety concerns regarding to insertional mutagenesis.
  • Use of vesicular stomatitis virus G glycoprotein (VSV-G) allows for ultracentrifugation concentration, higher titters, but proves to have cytotoxic effects on producing cells so virus are obtained by transient transfection.
  • Production is achieved through trans-complementation, using second and third generation vectors.
  • Lentiviruses transduce most cell types within the central nervous system (CNS) in vivo.

Picture of lentiviral vectors viruses

Lentivirus Production by co-transfection. Virions are produced by transfecting three different plasmid into the hosting cells (HEK293 Lenti-X®), this methods ensures high degree of biosafety, since the risk of replicant competent lentiviruses is significantly reduced due to the separation of cis-acting sequences (transgene plasmid in the figure), required for the transfer of the viral genome to target cells, from the trans-acting sequences encoding the viral proteins (gag, pol and env VSV-G). Both types of construct are introduced in the same cell to produce the virions. We are currently producing viruses based in the 2nd generation packaging systems (but 3rd generation packaging systems are also available upon customer's request), this means that all accessory genes have been deleted and the genes necessary for viral replication (pol), viral surface proteins (env: VSV-G) and viral core proteins (gag) are provided in separate construct. One advantage of this system is that the packaging and envelop vectors work with 2nd and 3rd generation transgene vectors, and thus a wider range of possibilities are available.

Adeno Associated Viruses (AAVs)

Small viruses that can carry relatively small payload, but they do not exhibit pathogenicity nor cytotoxicity in the host organism. They can mediate gene transfer to both mitotic and non-mitotic cells, they lack the risk of oncogene activation, since they can exist stably in an episomal state with a low rate of chromosomal integration. AA virions are small (20-25 nm diameter) and have no enveloped, they carry ssDNA and they are defective virus dependent on the presence of a helper virus for replication.

  • Require BSL2 safety level lab
  • They carry a small payload up to 4.5 Kb
  • No pathogenic and replicant-defective.
  • AAV dsDNA in host cells is maintained in an “episomal” state (not integrated in the host genome).
  • Transgene expression mediate by recombinant AAV vectors can persist for months and up to several years.
  • Can be package with different serotypes that confer different infectious spectrum (tropism):

Picture of adeno associated viruses

AAV viruses and production. A) AAV are non-enveloped, icosahedral and small. They package ~4.7 kB, flanked by ITR singled stranded DNA containing two Open Reading Frames encoding for Replication (rep) and capside (cap) proteins. B) We currently work with recombinant AAV, meaning that AAV ssDNA no longer contains the cap and rep genes but the transgene which will be introduced in the host cells. Therefore, production of these viruses is achieved by co-transfection of the transgene vector and an AAV helper plasmids that contains the necessary genes for the packaging and virus production within the host cells.

Serotype Tropism Comments
AAV1 CNS, skeletal muscle, Heart  
AAV2 CNS, photoreceptor cells Neurons, general tropism in all brain areas
AAV4 CNS, Lung  
AAV5 CNS, photoreceptor cells, Lung Astrocytes, hippocampal neurons, Selective retrogade Transport
AAV6 skeletal muscle, Lung Retrogade transduction
AAV7 skeletal muscle, Liver  
AAV8 CNS, photoreceptor cells, skeletal muscle, Heart, Liver, Pancreas High specificity in Auditory Cortex
AAV9 CNS, skeletal muscle, Heart, Liver, Lung Neurons, hippocampus, auditory cortex

AAV pseudotyping: Define as the mix of a capsid and genome from different viral serotypes. We currently have in stock some plasmids for AAV production purchased from PasmidFactory including pDM and pDG  (Wild type AAV2 serotype), and a series of pDP including rep2 (structural protein from AAV2 serotype) and different cap proteins (capsid protein) conferring different tropisms depending which cap proteins are coded. 

Before Starting a Project

  1. Obtain the work permits for the viruses to be produced (more information can be found in the biosafety website from Karolinska Institutet), that you will be using when the core facility delivers them to you. Be sure to be familiar with the institutional guidelines for virus use and disposal.
  2. Obtain the desired expression vector to package in the type of virus you have decided to use (The core facility can help with that, and we also offer packaging plasmid systems for lenti and AA viruses).

What to provide to the core:

  1. Obtain the necessary Material Transfer Agreement (MTA) if needed. If the customer provides a plasmid purchased from a company or a non-profit organization (i.e. AddGene), it is the customer's obligation to contact the depository entity (laboratory or company which produced the plasmid), to find out if some MTA agreement must be fulfilled, in order for the VirusTech core facility to work with those plasmids.
  2. Download, fill and submit the order form that can be downloaded in the “Services and Ordering” section.
  3. Download the L-anmälan (Permits and notifications for Genetic Modified Microorganisms work) documents in Swedish and/or in English (word). Read the Guidelines and Instructions to fill the document (pdf).

Once all these documents have been properly filled and signed they should be send to the Core facility.

Once the documents have been revised and approved by the Facility and the biosafety department at KI, the investigator must:

  1. Provide the core facility with the expression vector (plasmid) at the right concentration: ≥150 µg of transgene AAV plasmid and  ≥300 µg of the LV expression vector at a concentration of at least 0.30 µg/µl (preferably ≥ 1µg/µl). The DNA should have been purified using an endotoxin-free protocol (e.g. Endo-free maxi/mega/Giga plasmids purification kits or equivalent).
  2. High Quality DNA: Plamid DNA should be checked for purity and have an A260/280 ratio no lower than 1.8 (the actual value of this ratio must be provided to the core). See below in each type of virus for further details.
  3. Additional SmaI/SrfI digestion analysis on the AAV transgene plasmids should be performed and the results should be also submitted to the core (see AAV sections for further details).

Services and Ordering

Production of Lentivirus:

Packaging and production of Lentivirus. Packaging plasmid of 2nd generation (provided by two different plasmids, i) the Envelope Plasmid, coding for VSV-G, ii) Packaging Plasmid with the gag, pol, tat and rev genes), which are capable of package both 2nd and 3rd generation transfer plasmids. All our Lentivirus are produced using the VSV-G envelop to concentrate the viruses by ultracentrifugation and obtain high titters adequate for in vivo experiments.

Services include:

  • Transfection and supernatant collection
  • Concentration by double step centrifugation, to suitable volumes stated by the customer
  • Quality control assay include a physical titter (vg/mL) by RT-qPCR or functional titter (IFU/mL) by FACS when appropriated. The titration is requested by the customer.

Note: For a successful virus production the VirusTech core recommends to transform the expression plasmids into E. coli strains recommended for use when cloning unstable inserts such as lentiviral DNA containing direct repeats, prior the DNA prep and purification. Such strains can be obtained from different companies such One Shot™ Stbl3™ #C737303 (Invitrogen, ThermoFisher) or NEB Stable competen E. coli #C30540I (NEB).

Price List for Lentiviral production:

  1. KI users
Product Prices(1) (SEK) Volume Titters in IFU/mL (vg/mL) Timeline(2)
Non-concentrate supernatant 3.600-3.900 100 mL ~105-106 3 weeks
Concentrated small volumes 4.900-5.100 50-80 µl ≥109 (1011) 4 weeks
Concentrated big volumes 4.900-5.100 500-1000 µl ≥108 (1010) 4 weeks

(1) Prices vary depending in the quality control assay performed.
(2) From the time the plasmid is received depending on the current queue.

  1. External users:

Product Prices (1) (SEK) Volume Titters in IFU/mL (vg/mL) Timeline (2)
Non-concentrate supernatant 4.600-4.900 100 mL ~105-106 3 weeks
Concentrated small volumes 5.900-6.100 50-80 µl ≥109 (1011) 4 weeks
Concentrated big volumes 5.900-6.100 500-1000 µl ≥108 (1010) 4 weeks

(1) Prices vary depending in the quality control assay performed.
(2) From the time the plasmid is received depending on the current queue.

Ordering Lentivirus production:

  1. Download the order form
  2. Fill it out an submit to: or

Production of AAV:

Production and packaging available from different pseudotypes. Purchased from PlasmidFactory which holds the license from the German Cancer Research Center, we provide the user with several serotypes to choose from, depending on their needs:

  • AAV helper plasmid pDP1 (rep2/cap1)
  • AAV helper plasmid pDG  (rep2/cap2)
  • AAV helper plasmid pDP5 (rep2/cap5)
  • AAV helper plasmid pDP8.ape (rep2/cap8)

Services include:

  • Transfection and supernatant collection
  • Virus precipitation.
  • Crude Purification by centrifugation, discontinuous Iodixanol gradient and anion exchange using adsorption membrane.
  • Buffer exchange and concentration by centrifugation filter devices
  • Filtration
  • Quality control assay include a physical titter (vg/mL) by RT-qPCR or functional titter (IFU/mL) by FACS when appropriated. The titration is requested by the customer.

Note: AAV vector plasmids are notorious for the instability and frequent deletion of the ITRs when propagated in E. coli. For this reason, it is important to carefully confirm the integrity of every preparation. Even the best plasmid preparations contain significant quantities (5–15%) of DNA containing small deletions in the ITR, which during cloning procedures can be randomly selected and amplified. The integrity of the ITRs is typically monitored by restriction enzyme analysis sufficient to identify small deletions (20 bp). Most commonly this is achieved with digestion with Sma I or Srf I, which cut twice within an unstable portion of the ITR. Because of these stability issues, most investigators utilize a recombination deficient E. coli strain, such as SURE (Agilent Technologies, ref#200152) or NEB stable (NEB, ref#C3040I) for AAV vector plasmid propagation and cloning.

Material provided and price list:

~500 µl in chosen size aliquots, titer ≥1010 vg/mL (viral genomes/mL). Prices include titration by qPCR or FACS:

Physical titration: 4900 SEK/virus for KI users; 5800 SEK/virus for external users.

Functional titration (if available): 5100 SEK/virus for KI users, 6100 SEK/virus for external users.

Ordering AAV production:

  1. Download the order form
  2. Fill it out and submit to: or


(Coming soon)

Picture Gallery

site under construction

Contact us


Dr. Emma R. Andersson

Dr. Jens Hjerling-Leffler

Lab coordinator/manager

Laboratory coordinator

Albert Blanchart Aguado

Organizational unit: Andersson, Emma

Scientific technician

Laboratory technician

Hongyan Xia

Organizational unit: Department of Medical Biochemistry and Biophysics (MBB), C2


The facility is located at the Department of Cell and Molecular Biology (CMB), von Eulers väg 1-3, SE-171 65 Solna, Sweden


Telephone: (+46) 8 524 87 387