Paratransgenesis
Encyclopedia
Paratransgenesis is a technique that attempts to eliminate a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

 from vector populations through transgenesis
Transgenesis
thumb|300px|right|A diagram comparing the genetic changes achieved through conventional plant breeding, transgenesis and cisgenesisTransgenesis is the process of introducing an exogenous gene – called a transgene – into a living organism so that the organism will exhibit a new property and transmit...

 of a symbiont of the vector. The goal of this technique is to control vector-borne diseases
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

. The first step is to identify proteins
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that prevent the vector species from transmitting the pathogen. The genes
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 coding for these proteins are then introduced into the symbiont
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

, so that they can be expressed in the vector. The final step in the strategy is to introduce these transgenic symbionts into vector populations in the wild.

The first example of this technique used Rhodnius prolixus
Rhodnius prolixus
Rhodnius prolixus is the second most important triatomine vector of the Chagas parasite due to its efficient adaptation to the human domicile in northern South America, where sylvatic populations also exist, and in Central America where it is exclusively domestic...

which is associated with the symbiont Rhodococcus rhodnii. Rhodnius prolixus
Rhodnius prolixus
Rhodnius prolixus is the second most important triatomine vector of the Chagas parasite due to its efficient adaptation to the human domicile in northern South America, where sylvatic populations also exist, and in Central America where it is exclusively domestic...

is an important insect vector of Chagas's disease
Chagas disease
Chagas disease is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. T. cruzi is commonly transmitted to humans and other mammals by an insect vector, the blood-sucking insects of the subfamily Triatominae most commonly species belonging to the Triatoma, Rhodnius,...

 that is caused by Trypanosoma cruzi
Trypanosoma cruzi
Trypanosoma cruzi is a species of parasitic euglenoid trypanosomes. This species causes the trypanosomiasis diseases in humans and animals in America...

. The strategy was to engineer R. rhodnii to express proteins such as Cecropin A that are toxic to Trypanosoma cruzi or that block the transmission of Trypanosoma cruzi.

In order to perform paratransgenesis, there are several requirements:
  • The Symbiotic bacteria
    Symbiotic bacteria
    Symbiotic bacteria are bacteria living in symbiosis with another organism or each other. For example, Zoamastogopera, found in the stomach of termites, enable them to digest cellulose....

     can be grown in vitro easily.
  • They can be genetically modified
    Genetic engineering
    Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...

    , such as through transformation with a plasmid
    Plasmid
    In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...

    containing the desired gene.
  • The engineered symbiont is stable and safe.
  • The association between vector and symbiont cannot be attenuated.
  • Field delivery is easily handled.
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