Serial passage

Last updated

Serial passage is the process of growing bacteria or a virus in iterations. For instance, a virus may be grown in one environment, and then a portion of that virus population can be removed and put into a new environment. This process is repeated with as many stages as desired, and then the final product is studied, often in comparison with the original virus.

Contents

This sort of facilitated transmission is often conducted in a laboratory setting, because it is of scientific interest to observe how the virus or bacterium that is being passed evolves over the course of the experiment. In particular, serial passage can be quite useful in studies that seek to alter the virulence of a virus or other pathogen. One consequence of this is that serial passage can be useful in creating vaccines, since scientists can apply serial passage and create a strain of a pathogen that has low virulence, yet has comparable immunogenicity to the original strain. [1] This can also create strains that are more transmissible in addition to lower virulence, as demonstrated by A/H5N1 passage in ferrets. [2]

Mechanism

Serial passage can either be performed in vitro or in vivo. In the in vitro method, a virus or a strain of bacteria will be isolated and allowed to grow for a certain time. After the sample has grown for that time, part of it will be transferred to a new environment and allowed to grow for the same period. [3] [4] This process will be repeated as many times as desired.

Alternatively, an in vivo experiment can be performed where an animal is infected with a pathogen, and this pathogen allowed time to grow in that host before a sample of it is removed from the host and passed to another host. This process is repeated for a certain number of hosts; the individual experiment determines this number.

When serial passage is performed either in vitro or in vivo, the virus or bacterium may evolve by mutating repeatedly. Identifying and studying mutations that occur often reveals information about the virus or bacterium being studied. Accordingly, after serial passage has been performed it can be valuable to compare the resulting virus or sample of bacteria to the original, noting any mutations that have occurred and their collective effects. Various significant outcomes may occur. The virulence of the virus may be changed, [5] or a virus could evolve to become adapted to a different host environment than that in which it is typically found. [5] Relatively few passages are necessary to produce a noticeable change in a virus; for instance, a virus can typically adapt to a new host within ten or so passages. [5]

Because serial passage allows for rapid evolution of a virus to its host, it can be used to study the evolution of antibiotic resistance; specifically, for determining what mutations could lead to the development of antibiotic resistance. [6]

History

The technique of serial passage has been around since the 1800s. In particular, Louis Pasteur's work with the rabies vaccine in the late 1800s exemplifies this method. [7]

Pasteur created several vaccines over the course of his lifetime. His work prior to rabies involved attenuation of pathogens, but not through serial passage. In particular, Pasteur worked with cholera and found that if he cultured bacteria for long periods of time, he could create an effective vaccine. [7] [8] Pasteur thought that there was something special about oxygen and this was why he was able to attenuate (create a less virulent version of) the bacteria. Pasteur also tried to apply this method to create a vaccine for anthrax, although with less success. [7]

Next, Pasteur wanted to apply this method to create a vaccine for rabies. However, rabies was, unbeknownst to him, caused by a virus, not a bacterial pathogen like cholera and anthrax, and for that reason rabies could not be cultured in the same way that cholera and anthrax could be. [8] Methods for serial passage for viruses in vitro were not developed until the 1940s, when John Enders, Thomas Huckle Weller, and Frederick Robbins developed a technique for this. These three scientists subsequently won the Nobel Prize for their major advancement. [9]

To solve this problem, Pasteur worked with the rabies virus in vivo. [7] [8] In particular, he took brain tissue from an infected dog and transplanted it into another dog, repeating this process multiple times, and thus performing serial passage in dogs. [7] These attempts increased the virulence of the virus. [7] Then, he realized that he could put dog tissue into a monkey to infect it and then perform serial passage in monkeys. [7] After completing this process and infecting a dog with the resulting virus, Pasteur realized that the virus was less virulent. [7] Mostly, Pasteur worked with the rabies virus in rabbits. [8] Ultimately, to create his vaccine for rabies, Pasteur used a simple method that involved drying out tissue. As is described in his notebook:

In a series of flasks in which air is maintained in a dry state…each day one suspends a thickness of fresh rabbit spinal tissue taken from a rabbit dead of rabies. Each day as well, one inoculates under the skin of a dog 1 mL of sterilized bouillion, in which has dispersed a small fragment of one of these desiccated spinal pieces, beginning with a piece most distant in time from when it was worked upon, in order to be sure that it is not at all virulent. [7]

Pasteur mostly used other techniques besides serial passage to create his vaccines. However, the idea of attenuating a virus through serial passage still holds.

Use in vaccines

One way to attenuate a virus to a host is by passing the virus in a different species. [5] The idea is that, as a strain of a virus becomes more adapted to a different species, that strain will become less adapted to the original host, thus decreasing in virulence with respect to the original host. [5] This is the implicit principle that Louis Pasteur was unknowingly making use of when he passed the rabies virus in monkeys and ended up with a virus that was less dangerous to dogs, for example. [7]

The process of serial passage yields a live vaccine. There are both advantages and disadvantages to this. Most notably, live vaccines are sometimes more effective and more long-lasting than inactivated or other types of vaccines. [10] [11] However, just as the virus evolved to become attenuated, it may reverse-evolve in the host, leading to infection. [11]

Experiments

Researchers have conducted many experiments using serial passage. Some of the experimental uses for serial passage include changing the virulence of a virus, to study the adaptive evolution or potential evolution of zoonotic diseases to new hosts, and studying antibiotic resistance.

Increasing virulence for use in animal modeling

When developing vaccines for viruses, the emphasis is on attenuating the virus, or decreasing its virulence, in a given host. Sometimes it is useful to employ serial passage to increase the virulence of a virus. Usually, when serial passage is performed in a species, the result is a virus that is more virulent to that species. [5]

For example, one study [12] used serial passage in baboons to create a strain of HIV-2 that is particularly virulent to baboons. Typical strains of HIV-2 only infect baboons slowly. [12] This specificity makes it challenging for scientists to use HIV-2 in animal models of HIV-1, because the animals in the model will only show symptoms slowly. The more virulent strain of HIV-2 could be practical for use in animal models, however. [12]

Another study by Kanta Subbaro involved a serial passage experiment in which mice were infected with SARS. [13] SARS usually does not make mice particularly sick, however, after the virus had undergone serial passage in the mice, it had become lethal. [13]

Changing the virulence of SARS in this way was important, because without a virulent form of SARS to infect laboratory animals, scientists would have been unable to test the effects of SARS in an animal model. [13]

More generally, this experiment also reflects a general medical principle: The virulence of a virus is mediated by the difficulty of its transmission.

Generally, if a virus kills its host too quickly, the host will not have a chance to come in contact with other hosts and transmit the virus before dying. In serial passage, when a virus was being transmitted from host to host regardless of its virulence, such as Subbaro's experiment, the viruses that grow the fastest (and are therefore the most virulent) are selected for. [13]

This principle has public health implications, because it suggests that, in very densely populated or overcrowded areas, such as slums or group quarantine facilities, natural selection may favour more virulent viruses.

This also helps explain why good hygiene is so important. Good hygiene selects against highly virulent viruses by lowering the ability of pathogens to transmit. [13]

Serial passaging has been used to produce mouse-adapted SARS-CoV-2. [14]

Influenza

The H5N1 virus is a particularly lethal strain of influenza. Currently, it can infect humans, but it is not contagious between humans. Still, over 600 people worldwide are known to have died from animal-transmitted H5N1 virus, [13] so the transmissibility of the virus is of major concern to scientists.

Several serial passage experiments have been conducted to determine the feasibility of the virus becoming transmissible in humans. In particular, Ron Fouchier and his colleagues did a 10-step serial passage experiment in ferrets. [13] In doing so, they created a strain of influenza that not only infected ferrets, but was transmissible between ferrets. [13] Notably, this strain was very similar to the original strain with which they had infected the first ferret—in other words, only a few mutations were necessary for the virus to become transmissible between ferrets. [13] [15] Similarly, researcher Yoshihiro Kawaoka found that a single mutation is necessary to make the virus transmissible in ferrets. [15]

Both Fouchier's research and Kawaoka's research were initially censored, per implications for bioterrorism. [15] The research was later published, but remained controversial. [15]

Serial passage is an artificial technique that is used in a laboratory setting, rather than a natural process. Accordingly, the likelihood that the H5N1 virus would actually mutate to become transmissible in humans is unknown; however, researcher Derek Smith created an evolutionary model to show that this is possible. [13]

Understanding how viruses jump between species

Another use of serial passage is in understanding how pathogens adapt to new species. By introducing a pathogen into a new host species and performing serial passage, scientists can observe as the pathogen adapts to its new host and pinpoint the mutations that allow for this adaptation. [5]

See also

Related Research Articles

<span class="mw-page-title-main">Myxomatosis</span> Rabbit disease caused by Myxoma virus

Myxomatosis is a disease caused by Myxoma virus, a poxvirus in the genus Leporipoxvirus. The natural hosts are tapeti in South and Central America, and brush rabbits in North America. The myxoma virus causes only a mild disease in these species, but causes a severe and usually fatal disease in European rabbits.

Virulence is a pathogen's or microorganism's ability to cause damage to a host.

<span class="mw-page-title-main">Avian influenza</span> Influenza caused by viruses adapted to birds

Avian influenza, also known as avian flu, is a bird flu caused by the influenza A virus, which can infect people. It is similar to other types of animal flu in that it is caused by a virus strain that has adapted to a specific host. The type with the greatest risk is highly pathogenic avian influenza (HPAI).

<span class="mw-page-title-main">Influenza A virus subtype H5N1</span> Subtype of influenza A virus

Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus which can cause illness in humans and many other species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza. It is enzootic in many bird populations, especially in Southeast Asia. One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia. It is epizootic and panzootic, killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread. Many references to "bird flu" and H5N1 in the popular media refer to this strain.

<i>Francisella tularensis</i> Species of bacterium

Francisella tularensis is a pathogenic species of Gram-negative coccobacillus, an aerobic bacterium. It is nonspore-forming, nonmotile, and the causative agent of tularemia, the pneumonic form of which is often lethal without treatment. It is a fastidious, facultative intracellular bacterium, which requires cysteine for growth. Due to its low infectious dose, ease of spread by aerosol, and high virulence, F. tularensis is classified as a Tier 1 Select Agent by the U.S. government, along with other potential agents of bioterrorism such as Yersinia pestis, Bacillus anthracis, and Ebola virus. When found in nature, Francisella tularensis can survive for several weeks at low temperatures in animal carcasses, soil, and water. In the laboratory, F. tularensis appears as small rods, and is grown best at 35–37 °C.

An emergent virus is a virus that is either newly appeared, notably increasing in incidence/geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious diseases and raise public health challenges globally, given their potential to cause outbreaks of disease which can lead to epidemics and pandemics. As well as causing disease, emergent viruses can also have severe economic implications. Recent examples include the SARS-related coronaviruses, which have caused the 2002-2004 outbreak of SARS (SARS-CoV-1) and the 2019–21 pandemic of COVID-19 (SARS-CoV-2). Other examples include the human immunodeficiency virus which causes HIV/AIDS; the viruses responsible for Ebola; the H5N1 influenza virus responsible for avian flu; and H1N1/09, which caused the 2009 swine flu pandemic. Viral emergence in humans is often a consequence of zoonosis, which involves a cross-species jump of a viral disease into humans from other animals. As zoonotic viruses exist in animal reservoirs, they are much more difficult to eradicate and can therefore establish persistent infections in human populations.

<span class="mw-page-title-main">H5N1 genetic structure</span>

H5N1 genetic structure is the molecular structure of the H5N1 virus's RNA.

Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that is endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV-1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species.

<i>Feline calicivirus</i> Species of virus

Feline calicivirus (FCV) is a virus of the family Caliciviridae that causes disease in cats. It is one of the two important viral causes of respiratory infection in cats, the other being Felid alphaherpesvirus 1. FCV can be isolated from about 50% of cats with upper respiratory infections. Cheetahs are the other species of the family Felidae known to become infected naturally.

The NS1 influenza protein (NS1) is a viral nonstructural protein encoded by the NS gene segments of type A, B and C influenza viruses. Also encoded by this segment is the nuclear export protein (NEP), formally referred to as NS2 protein, which mediates the export of influenza virus ribonucleoprotein (RNP) complexes from the nucleus, where they are assembled.

<span class="mw-page-title-main">Human mortality from H5N1</span>

Human mortality from H5N1 or the human fatality ratio from H5N1 or the case-fatality rate of H5N1 is the ratio of the number of confirmed human deaths resulting from confirmed cases of transmission and infection of H5N1 to the number of those confirmed cases. For example, if there are 100 confirmed cases of humans infected with H5N1 and 10 die, then there is a 10% human fatality ratio. H5N1 flu is a concern due to the global spread of H5N1 that constitutes a pandemic threat. The majority of H5N1 flu cases have been reported in southeast and east Asia. The case-fatality rate is central to pandemic planning. Estimates of case-fatality (CF) rates for past influenza pandemics have ranged from to 2-3% for the 1918 pandemic to about 0.6% for the 1957 pandemic to 0.2% for the 1968 pandemic. As of 2008, the official World Health Organization estimate for the case-fatality rate for the outbreak of H5N1 avian influenza was approximately 60%. Public health officials in Ontario, Canada argue that the true case-fatality rate could be lower, pointing to studies suggesting it could be 14-33%, and warned that it was unlikely to be as low as the 0.1–0.4% rate that was built into many pandemic plans.

An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by "killing" the pathogen.

<span class="mw-page-title-main">Rabies vaccine</span> Vaccines to prevent rabies in humans and animals

The rabies vaccine is a vaccine used to prevent rabies. There are several rabies vaccines available that are both safe and effective. Vaccinations must be administered prior to rabies virus exposure or within the latent period after exposure to prevent the disease. Transmission of rabies virus to humans typically occurs through a bite or scratch from an infectious animal, but exposure can occur through indirect contact with the saliva from an infectious individual.

The French Louis Pasteur (1822–1895) and German Robert Koch (1843–1910) are the two greatest figures in medical microbiology and in establishing acceptance of the germ theory of disease. In 1882, fueled by national rivalry and a language barrier, the tension between Pasteur and the younger Koch erupted into an acute conflict.

Porcine epidemic diarrhea is a condition caused by the porcine epidemic diarrhea virus that leads to severe gastrointestinal disease in pigs.

This glossary of virology is a list of definitions of terms and concepts used in virology, the study of viruses, particularly in the description of viruses and their actions. Related fields include microbiology, molecular biology, and genetics.

Biotechnology risk is a form of existential risk from biological sources, such as genetically engineered biological agents. The release of such high-consequence pathogens could be

<span class="mw-page-title-main">Host switch</span> Evolutionary change of the host specificity of a parasite or pathogen

In parasitology and epidemiology, a host switch is an evolutionary change of the host specificity of a parasite or pathogen. For example, the human immunodeficiency virus used to infect and circulate in non-human primates in West-central Africa, but switched to humans in the early 20th century.

<span class="mw-page-title-main">Animal vaccination</span> Process

Animal vaccination is the immunisation of a domestic, livestock or wild animal. The practice is connected to veterinary medicine. The first animal vaccine invented was for chicken cholera in 1879 by Louis Pasteur. The production of such vaccines encounter issues in relation to the economic difficulties of individuals, the government and companies. Regulation of animal vaccinations is less compared to the regulations of human vaccinations. Vaccines are categorised into conventional and next generation vaccines. Animal vaccines have been found to be the most cost effective and sustainable methods of controlling infectious veterinary diseases. In 2017, the veterinary vaccine industry was valued at US$7 billion and it is predicted to reach US$9 billion in 2024.

Gain-of-function research is medical research that genetically alters an organism in a way that may enhance the biological functions of gene products. This may include an altered pathogenesis, transmissibility, or host range, i.e., the types of hosts that a microorganism can infect. This research is intended to reveal targets to better predict emerging infectious diseases and to develop vaccines and therapeutics. For example, influenza B can infect only humans and harbor seals. Introducing a mutation that would allow influenza B to infect rabbits in a controlled laboratory situation would be considered a gain-of-function experiment, as the virus did not previously have that function. That type of experiment could then help reveal which parts of the virus's genome correspond to the species that it can infect, enabling the creation of antiviral medicines which block this function.

References

  1. ↑ "Serial passage". Biology online. Retrieved 16 April 2014.
  2. ↑ Herfst S, Schrauwen EJ, Linster M, Chutinimitkul S, de Wit E, Munster VJ, et al. (2012). "Airborne transmission of influenza A/H5N1 virus between ferrets". Science. 336 (6088): 1534–41. Bibcode:2012Sci...336.1534H. doi:10.1126/science.1213362. PMC   4810786 . PMID   22723413.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ↑ Chapuis É, Pagès S, Emelianoff V, Givaudan A, Ferdy JB (January 2011). "Virulence and pathogen multiplication: a serial passage experiment in the hypervirulent bacterial insect-pathogen Xenorhabdus nematophila". PLOS ONE. 6 (1): e15872. Bibcode:2011PLoSO...615872C. doi: 10.1371/journal.pone.0015872 . PMC   3031541 . PMID   21305003.
  4. ↑ Somerville GA, Beres SB, Fitzgerald JR, DeLeo FR, Cole RL, Hoff JS, Musser JM (March 2002). "In vitro serial passage of Staphylococcus aureus: changes in physiology, virulence factor production, and agr nucleotide sequence". Journal of Bacteriology. 184 (5): 1430–7. doi:10.1128/jb.184.5.1430-1437.2002. PMC   134861 . PMID   11844774.
  5. 1 2 3 4 5 6 7 Woo HJ, Reifman J (January 2014). "Quantitative modeling of virus evolutionary dynamics and adaptation in serial passages using empirically inferred fitness landscapes". Journal of Virology. 88 (2): 1039–50. doi:10.1128/JVI.02958-13. PMC   3911671 . PMID   24198414.
  6. ↑ Martínez JL, Baquero F, Andersson DI (October 2011). "Beyond serial passages: new methods for predicting the emergence of resistance to novel antibiotics". Current Opinion in Pharmacology. 11 (5): 439–45. doi:10.1016/j.coph.2011.07.005. PMID   21835695.
  7. 1 2 3 4 5 6 7 8 9 10 Smith KA (2012). "Louis pasteur, the father of immunology?". Frontiers in Immunology. 3: 68. doi: 10.3389/fimmu.2012.00068 . PMC   3342039 . PMID   22566949.
  8. 1 2 3 4 Schwartz, M. (2001). The life and works of Louis Pasteur. Journal of Applied Microbiology, 91 (4), 597-601.
  9. ↑ McCullers JA (September 2007). "Evolution, benefits, and shortcomings of vaccine management". Journal of Managed Care Pharmacy. 13 (7 Suppl B): S2–6. doi: 10.18553/jmcp.2007.13.s7-b.2a . PMC   10438138 . PMID   17874877.
  10. ↑ Hunt R. "'Vaccines: past successes and future prospects". Microbiology and Immunology On-line. Retrieved 5 May 2014.
  11. 1 2 "Types of Vaccines". National Institute of Allergy and Infectious Diseases. Retrieved 5 May 2014.
  12. 1 2 3 Locher CP, Witt SA, Herndier BG, Abbey NW, Tenner-Racz K, Racz P, Kiviat NB, Murthy KK, Brasky K, Leland M, Levy JA (January 2003). "Increased virus replication and virulence after serial passage of human immunodeficiency virus type 2 in baboons". Journal of Virology. 77 (1): 77–83. doi:10.1128/jvi.77.1.77-83.2003. PMC   140565 . PMID   12477812.
  13. 1 2 3 4 5 6 7 8 9 10 Zimmer C (2013). "Chapter 15". The Tangled Bank (second ed.). Robert and Co. Publishers. pp. 399–427.
  14. ↑ Pandey K, Acharya A (2021). "Animal models for SARS-CoV-2 research: A comprehensive literature review". Transboundary and Emerging Diseases (published October 2020). 68 (4): 1868–1885. doi:10.1111/tbed.13907. PMC   8085186 . PMID   33128861. Gu et. al. also generated a mouse-adapted SARS-CoV-2 from serial passage of human clinical isolate BetaCov/human/CHN/Beijing_IME-BJ05/2020 in aged mice (Gu et al., 2020). [...] Similarly, mouse-adapted SARS-CoV-2 is produced by serial passaging of virus in mouse lungs, which reduces virus potency but on the other hand also increases chances of mutations.{{cite journal}}: External link in |quote= (help)
  15. 1 2 3 4 Puiu T (3 May 2012). "H5N1 controversial paper shows that bird flu is only a genetic mutation away from mammal flu". ZME Science. Retrieved 26 April 2014.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.