Team:Freiburg/Project/Coli Strains
Information about viruses and bacteria
German Measles
The Rubella Virus (RV) is the only member of the genus Rubiviridae and belongs to the family of Togaviridae. It contains single-stranded plus-sense RNA, which encodes three structural and two non-structural proteins 1). Two of the structural proteins are the envelope proteins E1 and E2 that form heterodimers arranged in groups of three and are distributed all over the viruses surface 2). As the glycoprotein E1 appears to be immunodominant 3), we decided to use it with the respective sequence as RV antigen for the DiaCHIP and let it be synthesized by IDT.
The Rubella Virus is transmitted via airborne infection with humans as the only known hosts. It causes the rubella disease, also known as German measles or Rubeola. After the first infection the virus persists in the body for the whole life providing lifelong immunity and the diseases can therefore be referred to as typical for childhood. It goes along with exanthemas, fever, headache, rheumatic pains and swollen lymph nodes. The infection can anyways for some patients be asymptomatic as well. In contrast, in rare cases it can come to complications. Those are more frequent if the patient already reached adulthood. In such cases arthritis, bronchitis, encephalitis and inclusion of heart damages are conceivable 4).
As RV can also cross the placenta, pregnant women getting infected in the beginning of their pregnancy might lose their child due to a spontaneous abort. The children can also be born but in many cases suffer from congenital rubella syndromes 5) such as deformities of the heart, cataracts or labyrinthine deafness.
Therapies are only symptomatic but there is vaccination available that could prevent the disease what is especially recommended to women planning to get pregnant.
Herpes Simplex
A lot of people might have already had little blisters in the area of the lip that disappeared after some days. In most cases those might have been provoked by the Herpes Simplex Virus Type 1 (HSV1).
HSV1 belongs to the Human Herpesviruses, as well as the Varicella Zoster Virus, and is therefore part of the family of Herpesviridae. It contains double-stranded DNA and an envelope consisting of at least 10 viral proteins surrounds the capsid. Most of these proteins are glycoproteins, one of which is the glycoprotein G that we express as HSV antigen. It is the glycoprotein differing the most among species so it allows their discrimination 6). Glycoprotein G is important for the attachment to the cell and the entry of the virus into it 7).
There are two different types of Herpes Simplex Virus with about 99% of identity in the gene regions. Both types are transmitted via the contact of mucous membranes. Type 1 – the one we are working with – can be transmitted via kissing, type 2 is mainly transmitted via sexual contact. Below we are only referring to the Herpes Simplex Virus Type 1. It remains in the body in a latent state and several outbreaks during life are possible. As about 85-90% of the world’s population is seropositive the primary infection often takes place prior to the age of five due to a transmission from the parents to their child 8). The infection of newborns is dangerous to life.
After intruding the body the virus proliferates and is shed via the mucous membrane. It also infiltrates neurons in which it persists lifelong, as already mentioned. In very severe cases the virus can cause encephalitis as well as meningitis. The reasons for sudden outbreaks of the virus are not clearly understood. A suppression of the immune system or stress are only some possible explanations.
A therapy with anti-viral drugs is possible, for cutaneous infections in facial or rather labial areas the application of corticoids is however usually sufficient 9).
Tetanus
If the ambulance is called to take care of an injured person often the first thing they do is to perform a preventing vaccination against Clostridium tetani. This is a little anaerobic gram-positive rod-shaped bacillus that forms spores. These can even survive in inhospitable areas and are present in soil. They can enter the human body easily via small wounds which is why injured people are at high risk of getting infected with C. tetani but cannot transmit the infection to other individuals.
In regions where people are not vaccinated and good health care is not provided, tetanus, which is caused by the bacterium, is a very common cause of death following injuries. The bacterium produces two toxins, named tetanospasmin and tetanolysin. The former was found to cause tetanus by reaching the bone marrow via the nerves. There it is responsible for provoking hypersensitivity, increased reflexes and spasms 10). The latter causes damage to the heart muscle and blood components 11).
For our DiaCHIP we expressed a part of the tetanospasmin protein that is generally referred to as tetanustoxin. It consists of a heavy and a light chain that are linked by disulfide bonds 12). We worked with the carboxyl-terminal domain of the heavy chain that is able to bind to the target membrane and allows the internalization of the actual toxic region of the light chain 13). As we did not express any of the toxic fragments there was no need for special safety measures. The toxin fragment interfering with the neuronal system was not expressed and the part we used is not able to reproduce itself.
After an infection with C. tetani the first symptoms are headache, muscle and dorsal pain and a feeling of being tired. Additionally, the patient may feel some tautness in the area of the injury and reveal sensitivity to light and noise. If the patient is not taken care of, the infection is manifested by local stiffening of muscles, mainly those in the area of the jaw and neck. In the following progression the patient will suffer from high fever and muscle spasms. Those will at first be located in the face but spread over the whole body what causes the typical extended position. The immense tension in the muscles due to the effect of the toxins can cause lesions as well as dislocations of the joints or broken bones. As a consequence, many patients suffer from shortened muscles, ankylosis (stiffness of the joints) or spine deformity. In case of the lack of appropriate health care, death due to suffocation or cardiovascular failure is common and occurs partially despite previous vaccination.
To avoid long-term effects due to an infection with C. tetani or even death, the wound is excised and surgically taken care of. Additionally, the patient will be treated with antibiotics and will be given antibodies targeting the toxin.
Varicella Zoster / Herpes Zoster
An infection going along with red and itching skin that nearly every person in the world suffers from…most might know it as chickenpox and might not even remember the first infection as this often takes place during childhood. The infection is caused by the Varicella Zoster Virus (VZV) that belongs to the family of Herpesviridae, the same family as the Herpes Simplex Virus, and contains double-stranded DNA surrounded by a capsid. A tegument fills the space between this capsid and the envelope 14). This outer layer contains different viral envelope glycoproteins, one of which is the glycorprotein E we used for the DiaCHIP as VZV antigen 15). It forms heterodimers with the glycoprotein I and was found to play an important role in cell-cell attachment as well as facilitating the entry of the virus and the assembly of the virion 16).
VZV is transmitted via droplet infection or by having contact with blisters or mucous membranes. Following the first contact with the virus and with an incubation time of about two weeks the patient suffers from fever and exanthemas that normally heal without leaving scars. This first infection is called Varicella Zoster or, as mentioned above, chickenpox. In the United States for example more than 95 percent of persons older than 20 years were seropositive for VZV 17).
As the virus resides in some ganglions of the body, mostly elderly or immune deficient people might again be afflicted with the disease that is then called Herpes Zoster. It manifests itself in exanthemas restricted to the area of the respective ganglion that is affected. Additionally, the patients are very sensitive to skin contact, have a fever and feel pain. In some cases the reactivation of the virus can lead to neuritis.
Normally the infection with the virus, the primary infection as well as the reactivation of the virus, are not life threatening and in most cases end without consequences for the patient. The primary infection is only a threat for newborns and immune deficient patients where a hemorrhagic development can be lethal. If adults are for the first time exposed to the virus it can also cause much more severe damage. The development of defects in the central nervous system is one of the most prominent consequences 18).
There is a live attenuated varicella vaccine available that is mainly applied for children and risk patients. Passive immunization with IgG antibodies is often the choice for exposed pregnant women and newborns within a time span of about 48 hours 19).
Syphilis
One of the most common sexually transmittable diseases nowadays, besides AIDS, is Syphilis that is also a chronical disease. It is caused by the bacterium Treponema pallidum subsp. pallidum, which is a gram-negative member of the family of four Spirochaetaceae and exhibits a spiral shape 20).
T. pallidum has a rather small genome as it lacks many coding regions e.g. for metabolic enzymes. Nonetheless, its gene encodes the bacterioferritin protein TpF1 that was found to be immunogenic and useful for serodiagnosis of different stages of syphilis 21). This is why we used this recombinant protein as T. palldium antigen for the DiaCHIP.
The bacterium is very difficult to cultivate in vitro, partly due to the absence of some metabolic capabilities. Humans are the only natural hosts of T. pallidum and can be passed from one individual to another not only during sex but also via kissing if there are small lesions in the mucous membrane through which they can escape and enter 22).
After infection with T. pallidum there are four stages of syphilis distinguishable. Primary syphilis is characterized by chancre at the place of infiltration but normally heals during a time span of three to 7 weeks. Additionally, in this first phase the patient might suffer from swollen lymph nodes.
The secondary syphilis manifests itself in exanthemas and moistening areas of the skin, mainly in the genital area and between fingers and toes, which are highly infectious. There might also show up enanthemas on mucous membranes and the patient might lose its hair.
The symptoms of these first two stages of syphilis often fade after about three months and a latency period of variable time, up to years, may follow. The patient is still contagious in the early time of this period but loses this characteristic after a while.
If the infection with T. pallidum reaches the next stage, inner organs are affected what may lead to hepatitis or damages involving the aorta for example. This is also the first stage in which the neuronal system is mostly battered. At latest a neurosyphilis develops during quaternary syphilis and the patient suffers from psychoses and the nerves shed their myelinisation.
It is also possible that organisms of T. pallidum are transmitted via the bloodstream from mother to child causing congenital syphilis. Depending on the immune response of the fetus consequences may vary from fetal death to fetal damage or an infected newborn. The defects can also have a wide range and affect growth, internal organs like liver or spleen and the neuronal system. The onset of these effects can start only after years but also immediately after birth 23).
If the disease is noticed early enough a treatment with penicillin can lead to a cure with, in best cases, no permanent harm 24).
