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Growth and Maintenance of Vero Cell Lines

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Vero cells are derived from the kidney of an African green monkey, and are one of the more commonly used mammalian continuous cell lines in microbiology and molecular and cell biology research. This unit includes protocols for the growth and maintenance of Vero cell lines in a research laboratory setting.
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Growth and Maintenance of Vero Cell Lines
Nicole C. Ammerman*, Magda Beier-Sexton, and Abdu F. Azad
Department of Microbiology and Immunology, University of Maryland School of Medicine, 660
West Redwood Street, Howard Hall, Suite 324, Baltimore, Maryland 21201, 410-706-3337
(phone), 410-706-0282 (fax)
Nicole C. Ammerman: namme001@umaryland.edu; Magda Beier-Sexton: mbeie001@umaryland.edu; Abdu F. Azad:
aazad@umaryland.edu
Abstract
Vero cells are derived from the kidney of an African green monkey, and are one of the more
commonly used mammalian continuous cell lines in microbiology, and molecular and cell biology
research. This unit includes protocols for the growth and maintenance of Vero cell lines in a
research laboratory setting.
Keywords
Vero cells; cell culture techniques; cell line
INTRODUCTION
Derived from the kidney of an African green monkey (Cercopithecus aethiops) in the 1960s,
Vero cells are one of the most common mammalian continuous cell lines used in research.
This anchorage-dependent cell line has been used extensively in virology studies, but has
also been used in many other applications, including the propagation and study of
intracellular bacteria (e.g., Rickettsia spp.; UNIT 3A.4) and parasites (e.g., Neospora), and
assessment of the effects of chemicals, toxins and other substances on mammalian cells at
the molecular level. In addition, Vero cells have been licensed in the United States for
production of both live (rotavirus, smallpox) and inactivated (poliovirus) viral vaccines, and
throughout the world Vero cells have been used for the production of a number of other
viruses, including Rabies virus, Reovirus and Japanese encephalitis virus. The protocols
outlined in this appendix detail procedures for the routine growth and maintenance of Vero
cells in a research laboratory setting. There are several lines of Vero cells commercially
available (i.e., Vero, Vero 76, Vero E6), but they were all ultimately derived from the same
source, and the protocols in this unit can be used with any line of Vero cells.
BASIC PROTOCOL 1
PROPAGATION OF VERO CELL CULTURE FROM FROZEN STOCKS
For long term storage, Vero cells are kept either in liquid nitrogen or at -80°C. This protocol
describes how to start growing Vero cells obtained from frozen stock. After recovery from
frozen stock, Vero cells usually take 2-3 passages to reach their regular growth rate, and this
should be taken into account if planning to use the cells for experiments, infections, etc. It is
*Contact Author.
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Curr Protoc Microbiol. Author manuscript; available in PMC 2009 November 1.
Published in final edited form as:
Curr Protoc Microbiol
. 2008 November ; APPENDIX: Appendix–4E. doi:
10.1002/9780471729259.mca04es11.
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important to note that Vero cells are anchorage-dependent cells and therefore cannot be
grown in suspension.
Materials
Vero cell stock, frozen in liquid nitrogen or at -80°C
Dulbecco’s modification of Eagle medium (DMEM), supplemented with 10% heat-
inactivated fetal bovine serum (FBS), filter sterilized (see recipe)
15mL conical tubes, sterile
25cm2 or 50cm2 tissue culture flasks with vented caps, sterile
Serological pipets, sterile
70% ethanol solution (used for decontamination of laminar flow hood and objects
brought into the hood)
NOTE: All equipment and solutions coming into contact with cells must be sterile, and
proper sterile technique should be used.
NOTE: All cell culture incubations are performed in a humidified 37°C incubator with 5%
CO2.
NOTE: All solutions should be warmed to room temperature or 37°C before contacting
cells.
1. Quickly thaw vial (cryovial) of Vero cells by gently swirling in a 37°C water bath.
The water in the water bath is a potential source of contamination for the cells. To
reduce the risk of contamination, keep the O-ring and cap of the cryovial out of the
water.
2. In a laminar flow hood, decontaminate the vial by spraying with 70% ethanol.
3. Transfer the Vero cell suspension from the cryovial into a 15mL conical tube
containing 10mL of DMEM supplemented with FBS.
Frozen cell stocks will contain the cryopreservant dimethyl sulfoxide (DMSO),
which can be harmful to the cells. Therefore, after thawing the cells, it is necessary
to dilute and remove the DMSO before transferring the cells to tissue culture flasks.
Media other than DMEM can also be used for growing Vero cells. See
COMMENTARY for more information.
4. Pellet cells by centrifugation at 200 × g for 5 minutes at room temperature.
5. Remove and discard supernatant; resuspend cells in 5-10mL DMEM supplemented
with 10% FBS.
Vero cells recover better after freezing when initiated in a small (25cm2 or 50cm2)
tissue culture flask. If using a 25cm2 flask, resuspend the cells in 5mL media; if
using a 50cm2 flask, resuspend the cells in 10mL media.
6. Transfer Vero cell suspension to tissue culture flask with vented cap.
7. Incubate flasks in 37°C incubator with 5% CO2.
8. Monitor cells daily or every other day. Change media every 3-4 days. When cells
reach a >90% confluent monolayer, passage cells into new tissue culture flasks (see
BASIC PROTOCOL 2).
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Vero cells recover slowly after freezing; therefore, it may take a week or more
before the cells are ready to be passaged. It may take 2 or 3 passages before the
Vero cells reach their normal growth rate.
BASIC PROTOCOL 2
MAINTENANCE OF VERO CELL CULTURE
Vero cells are derived from normal kidney cells; because the cells are not transformed, they
have not lost their contact inhibition. When these cells reach confluency, they stop growing
and start to die; therefore, it is extremely important to monitor Vero cells and to subculture
them as they form confluent monolayers. Actively growing Vero cell cultures double
approximately every 24 hours (Nahapetian et al. 1986). Depending on the number of cells
seeded and the flask size, the cells usually need to be passaged 2-3 times per week. This
protocol describes a general method for the subculturing of Vero cells in 75cm2 tissue
culture flasks.
Materials
Vero cells grown to a confluent monolayer in a 75cm2 flask with vented cap
DPBS without calcium or magnesium, filter-sterilized (see APPENDIX 2A)
1X trypsin-EDTA in DPBS without calcium or magnesium, filter-sterilized (see
recipe)
DMEM supplemented with 10% heat-inactivated FBS, filter-sterilized (see recipe)
75cm2 tissue culture flasks with vented caps, sterile
15mL conical tubes, sterile
Serological pipets, sterile
NOTE: All equipment and solutions coming into contact with cells must be sterile, and
proper sterile technique should be used.
NOTE: All cell culture incubations are performed in a humidified 37°C incubator with 5%
CO2.
NOTE: All solutions should be warmed to room temperature or 37°C before contacting
cells.
1. Remove growth medium from confluent monolayer of Vero cells.
2. Wash cells with 10mL 1X DPBS.
Serum contains trypsin inhibitors, so it is important to rinse off any remaining
media with DPBS.
3. Add 5mL of 1X trypsin-EDTA and incubate cells at 37°C for 2-3 minutes, until
cells start to streak as they detach from the flask.
Gentle shaking or tapping of the flask may help cells detach.
4. Add 5mL DMEM with 10% FBS to inactivate the trypsin-EDTA.
5. Wash down cells in media, pipetting gently to break up any clumps of cells.
6. Remove cell suspension from flask and transfer to a sterile 15mL conical tube.
7. Centrifuge at 200 × g for 5 minutes at room temperature.
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8. Remove and discard supernatant; resuspend cells in 10mL DMEM with 10% FBS.
9. Prepare desired dilution of cells in a total of 12-20mL DMEM with 10% FBS and
add to 75cm2 cell culture flasks with vented caps.
Dilutions of 1:5 to 1:10 are typical for routine cell culture. See Table A.1 for
recommended total medium volumes for growth in various sizes of tissue culture
vessels.
10. Incubate flasks in 37°C incubator with 5% CO2.
Monitor cells daily or every other day. Change media every 3-4 days. When cells
reach a >90% confluent monolayer, passage cells again by repeating this protocol.
BASIC PROTOCOL 3
PREPARATION OF FROZEN STOCKS OF VERO CELL CULTURE
Maintenance of frozen stocks is extremely important when culturing cell lines. When
actively growing cells will not be needed for an extended period of time (3 weeks or more),
keeping frozen stocks allows researchers to discontinue regular subculturing, saving
valuable time and money. Also, very importantly, frozen stocks of cells provide a new
source of cells should contamination occur during subsequent passages. In order to maintain
an inventory of low-subculture Vero cells, frozen stocks should be prepared shortly after
initiating cultures from frozen stocks.
Materials
Vero cells grown to a confluent monolayer in a 75cm2 flask with vented cap
DPBS without calcium or magnesium, filter-sterilized (see APPENDIX 2A)
1X trypsin-EDTA in DPBS without calcium or magnesium, filter-sterilized (see
recipe)
DMEM supplemented with 20% heat-inactivated FBS, filter-sterilized (see recipe)
Dimethyl sulfoxide (DMSO)
Cryovials suitable for freezing at -80°C or liquid nitrogen, sterile
15mL conical tubes, sterile
Serological pipets, sterile
CAUTION: DMSO is hazardous; see UNIT 1A.3 for guidelines on handling, storage, and
disposal.
NOTE: All equipment and solutions coming into contact with cells must be sterile, and
proper sterile technique should be used.
NOTE: All solutions should be warmed to room temperature or 37°C before contacting
cells.
1. In laminar flow hood, add 1mL DMSO to 9mL of the supplemented DMEM (for a
final concentration of 10% DMSO) in a 15mL conical tube.
DMSO will dissolve cellulose acetate membranes commonly used for filter-
sterilization, so it should be added after the DMEM has been supplemented with
FBS. The DMSO can be filtered using nylon membrane filters; alternatively, only
open the DMSO bottle under sterile conditions in the laminar flow hood.
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2. Remove growth medium from confluent monolayer of Vero cells.
3. Wash cells with 10mL 1X DPBS.
Serum contains trypsin inhibitors, so it is important to rinse off any remaining
media with DPBS.
4. Add 5mL of 1X trypsin-EDTA and incubate cells at 37°C for 2-3 minutes, until
cells start to streak as they detach from the flask.
Gentle shaking or tapping of the flask may help cells detach.
5. Add 5mL DMEM with 20% FBS to inactivate the trypsin-EDTA.
6. Wash down cells in media, pipetting gently to break up any clumps of cells.
7. Remove cell suspension from flask and transfer to a sterile 15mL conical tube.
8. Centrifuge at 200 × g for 5 minutes at room temperature.
9. Remove and discard supernatant; resuspend cells in 10mL DMEM with 20% FBS
and 10% DMSO.
The DMSO and FBS help preserve the cells during the freezing and thawing
processes, respectively.
10. Aliquot 1mL of resuspended cells into each cryovial.
11. Freeze cells slowly to -80°C, then continue to store the cells at -80°C or in liquid
nitrogen (preferred).
It is ideal to freeze the cells with the temperature decreasing at a rate of -1°C per
minute. This can be achieved using freezing containers such as the Nalgene Cryo
1°C Freezing Container. Alternatively, the cells can be put at 4°C for several hours,
then at -20°C overnight, then at -80°C overnight, and then either kept at -80°C or
transferred into liquid nitrogen storage.
REAGENTS AND SOLUTIONS
Dulbecco’s modification of Eagle Medium (DMEM) supplemented with heat-
inactivated fetal bovine serum (FBS)—10% or 20% heat-inactivated FBS (see
APPENDIX 2A)
Bring to desired volume in DMEM
Filter-sterilize
Store at 4°C
To make 500mL DMEM with 10% FBS, add 50mL heat-inactivated FBS to 450mL DMEM.
To make 500mL DMEM with 20% FBS, add 100mL heat-inactivated FBS to 400mL
DMEM.
1X trypsin-EDTA in DPBS—Dilute 10X trypsin-EDTA in DPBS (see APPENDIX 2A) to
obtained the desired volume with a 1X final concentration.
Filter-sterilize
Store at 4°C
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To make 100mL, add 10mL 10X trypsin-EDTA to 90mL DPBS.
COMMENTARY
Background Information
Vero cells were originally isolated from the kidney of a normal (i.e., non-diseased) adult
African green monkey on March 27, 1962 by Y. Yasumura and Y. Kawakita at the Chiba
University in Chiba, Japan. At its 93rd passage, the cell line was brought to the National
Institute of Allergy and Infectious Diseases at the National Institutes of Health in the United
States, and was provided to the American Type Culture Collection (ATCC) in 1966. By the
end of the 1960s, Vero cell lines were being used across the globe, primarily in virology
laboratories.
Vero cells can be purchased from ATCC and the European Collection of Animal Cell
Cultures (ECACC) repositories. Commonly used Vero cell lines from the ATCC include
CCL-81 (Vero), CRL-1286 (Vero C1008), and CRL-1587 (Vero 76). Commonly used cell
lines from the ECACC include 84113001 (Vero), 85020206 (Vero C1008), 88020401
(Vero-WHO), and 85020205 (Vero 76).
Critical Parameters and Troubleshooting
Mycoplasma contamination—One of the most important issues when growing any cell
culture is contamination. To reduce the risk of contamination, always work with the cells in
a sterile, laminar flow hood, make sure all equipment and solutions that come into contact
with the cells are sterile, and use proper sterile technique when working in the hood. Many
researchers will maintain their cells with a low level of antibiotic added to the medium, most
commonly a penicillin/streptomycin mixture. This can also help to reduce extraneous
bacterial contamination; however, depending on the application for which the Vero cells will
be used, adding antibiotics may not be recommended (for example, if the cells are to be
infected with bacteria). See Sato and Kan 2001 for a discussion regarding the use of
antibiotics in mammalian cell cultures. One of the most common sources of contamination
in cell cultures is Mycoplasma. These bacteria are very small (< 1μm), and therefore
contamination with Mycoplasma may not be visible with the naked eye, making these
organisms difficult to detect. Several Mycoplasma detection kits are commercially available
(such as the MycoAlert kit from Lonza, see Mariotti et al. 2008), and procedures for
detection and treatment of Mycoplasma contamination are also outlined in APPENDIX 3B.
Vero cells should be regularly tested (once per month) for the presence of Mycoplasma
contamination. If cells are found to be infected, the recommended course of action is to
discard the cells and start new cultures from uninfected frozen stocks. There are also several
options for treating Mycoplasma-infected cells (see Uphoff and Drexler 2002), including
commercially available kits.
Culture media—The protocols in this appendix describe the growth and maintenance of
Vero cells using DMEM as the culture medium. While DMEM is a very common culture
medium, a variety of other media can also be successfully used with Vero cells. See Sato
and Kan 2001 for a description of different culture media that can be used with mammalian
cell lines.
Depending on the application, it may be desired or necessary to count the number of cells
(i.e., if a specific number of cells need to be analyzed, plated, etc.) The concentration of
cells in suspension (following trypsin treatment) can be determined using a hemacytometer.
See Phelan 2007 for a complete protocol for determining the number of viable cells in
solution.
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When the Vero cells will be used for bacterial infections, the dividing host cells can dilute
the infections, which, depending on the system, can confound the analysis of the results.
One technique that has been employed to address this issue is gamma irradiation. At
appropriate levels, irradiation does not kill the Vero cells, but does prevent cell division,
allowing bacterial growth in Vero cells without the complicating factor of host cell division
and growth. See Chen et al. 1995 and Zamboni et al. 2001 for examples of gamma-
irradiation of Vero cells prior to infection with Ehrlichia chaffeensis and Coxiella burnetii,
respectively.
Certain applications, such as vaccine production, may require the scaling-up of Vero cell
cultures. There are two growth systems used for the scaling-up of anchorage-dependent cell
lines: roller bottles and microcarriers. Roller bottles are cylindrical vessels, and the cells
grow on the inner surface of the tube. The bottles slowly revolve to continually bathe the
cells in growth medium. The surface area available for cell attachment can be even further
increased by growing the cells on microcarrier beads. The beads, usually around 0.2mm, can
be made of dextran, cellulose, gelatin, glass or silica, and can considerably increase the
surface area available for Vero cell growth. See Hegde et al. 2008 and Silva et al. 2008 for
examples of Vero cell growth using roller bottles and microcarriers, respectively, for the
production of viral vaccines.
Anticipated Results
When first starting a seed of Vero cells from frozen stock, the cells will usually need a
couple of passages before they start growing at their normal rate, which is doubling
approximately every 24 hours (Nahapetian et al. 1986). After this initial “start-up” period,
the cells will proliferate regularly throughout subsequent passages. The use of proper sterile
technique when subculturing the cells should result in successful propagation of the Vero
cells. An example of Vero cells at around 95% confluency is shown in Figure 1.
Time Considerations
When subculturing Vero cells at a ratio between 1:5 to 1:10, they will generally need to be
passaged 2-3 times per week. If splitting the cells at a 1:10 ratio, the medium might need to
be changed between subculturing.
Literature Cited
Chen SM, Popov VL, Feng HM, Wen J, Walker DH. Cultivation of Ehrlichia chaffeensis in mouse
embryo, Vero, BGM, and L929 cells and study of Ehrlichia-induced cytopathic effect and plaque
formation. Infect Immun. 1995; 63:647–655. [PubMed: 7822034]
Hegde R, Gomes AR, Byregowda SM, Hugar P, Giridhar P, Renukaprasad C. Standardization of large
scale production of homologous live attenuated PPR vaccine in India. Trop Anim Health Prod.
2008; 40:11–16. [PubMed: 18551773]
Mariotti E, Mirabelli P, Di Noto R, Fortunato G, Salvatore F. Rapid detection of Mycoplasma in
continuous cell lines using a selective biochemical test. Leukemia Research. 2008; 32:323–326.
[PubMed: 17586045]
Nahapetian AT, Thomas JN, Thilly WG. Optimization of environment for high density Vero cell
culture: effect of dissolved oxygen and nutrient supply on cell growth and changes in metabolites. J
Cell Sci. 1986; 81:65–103. [PubMed: 3733899]
Phelan MC. Basic techniques in mammalian cell tissue culture. Curr Protoc Cell Biol. 2007; Chapter
1(Unit 1.1)
Sato JD, Kan M. Media for culture of mammalian cells. Curr Protoc Cell Biol. 2001; Chapter 1(Unit
1.2)
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Silva AC, Delgado I, Sousa MFQ, Carrondo MJT, Alves PM. Scalable culture systems using different
cell lines for the production of Peste des Petits ruminants vaccine. Vaccine. 2008; 26:3305–3311.
[PubMed: 18486286]
Uphoff CC, Drexler HG. Comparative antibiotic eradication of Mycoplasma infections from
continuous cell lines. In Vitro Cell Biol. 2002; 38:86–89.
Zamboni DS, Mortara RA, Rabinovitch M. Infection of Vero cells with Coxiella burnetii phase II:
relative intracellular bacterial load and distribution estimated by confocal laser scanning microscopy
and morphometry. J Microbiol Methods. 2001; 42:223–232. [PubMed: 11118656]
Key References
Coté RJ. Aseptic technique for cell culture. Curr Protoc Cell Biol. 2001; Chapter 1(Unit 1.3) This
reference contains a protocol for proper sterile technique using a laminar flow hood.
Simizu, E.; Terasima, T., editors. Vero Cells – Origin, Properties and Biomedical Applications.
Department of Microbiology, Chiba University; Chiba, Japan: 1988. This reference describes the
history of the Vero cell line, and it also includes an English language translation of the original
article describing Vero cells (Yasumura and Kawakita 1963, below).
Yasumura Y, Kawakita Y. Studies on SV40 in tissue culture – preliminary step for cancer research “in
vitro.”. Nihon Rinsho. 1963; 21:1201–1215. article in Japanese. This is the original publication
describing the isolation and initial propagation of the Vero cell line.
Internet Resources
http://www.atcc.org The American Type Culture Collection (ATCC) website. The ATCC maintains a
cell repository, which includes Vero cells. This site provides additional information regarding the
growth and maintenance of Vero cells.
http://www.ecacc.org.uk The European Collection of Animal Cell Cultures (ECACC) website. The
ECACC maintains a cell repository, which includes Vero cells. This site provides additional
information regarding the growth and maintenance of Vero cells.
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Figure 1.
Vero 76 cells (ATCC #CRL-1587), approximately 95% monolayer. These cells will need to
be subcultured within one day.
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Ammerman et al. Page 10
Table A.1
Cell medium volume requirements
Vessel Total medium volume
25cm2 flask 4-6 mL
50cm2 flask 7-10 mL
75cm2 flask 12-20 mL
150cm2 flask 25-40 mL
96-well plate 100 μL (per well)
16mm dish 800 μL
35mm dish 2 mL
60mm dish 8 mL
Curr Protoc Microbiol. Author manuscript; available in PMC 2009 November 1.
... Vero cells were established from kidney tissue sampled from an African green monkey (C. sabaeus) (Ammerman et al., 2008;Naoki et al., 2014). They originated from a primary culture initiated in March 1962 by a group from Chiba University in Japan. ...
... They originated from a primary culture initiated in March 1962 by a group from Chiba University in Japan. Over the months of serial passages of these cells, the researchers obtained a series of sub-lines, one of which was chosen as the standard Vero cell line (Ammerman et al., 2008;Naoki et al., 2014). ...
... This cell lineage was widely distributed among research laboratories and has become one of the most common mammalian immortalized cell lines used in research (Ammerman et al., 2008). In the field of virology, these cells have gained prominence for being susceptible to a wide range of viruses, such as simian polyomavirus SV-40, rubella virus, arboviruses, adenoviruses, H5N1 influenza virus, Ebola hemorrhagic fever virus 19, SARS-CoV, and MERS-CoV (Ellis et al., 1979;Horimoto and Kawaoka, 2006;Zaki et al., 2012;Kiesslich and Kamen, 2020). ...
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... Vero cells are derived from the kidney of an African green monkey and are a model line close to fibroblasts, primarily present in human tissues due to their ability to form connective tissue. This makes it one of the more commonly used mammalian continuous cell lines in microbiology and molecular and cell biology research (Ammerman et al., 2008). THP-1 is a human leukemia monocytic cell line, which has been extensively used to study monocyte/macrophage functions, mechanisms, signaling pathways, and nutrient and drug transport (Chanput et al., 2014). ...
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... Vero cells were derived from the kidney of an African green monkey, cells were maintained in Dulbecco's Modified Eagle's Medium (DMEM), supplemented with 10% heat-inactivated FBS and penicillin-streptomycin solution 1% at 37 • C, 5% CO 2 atmosphere and > 95% humidity [58]. ...
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... Vero cells were derived from the kidney of an African green monkey, cells were maintained in Dulbecco's Modified Eagle's Medium (DMEM), supplemented with 10% heat-inactivated FBS and penicillin-streptomycin solution 1% at 37 • C, 5% CO 2 atmosphere and > 95% humidity [58]. ...
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