Team:VIT Vellore
ANTIBIOTICS
Are they really the solution to everything?
What are antibiotics?
Antibiotics are one kind of antimicrobial peptides active against bacteria. They may either kill the bacteria, or inhibit their growth (bactericidal and bacteriostatic, respectively). The first antibiotic discovered was Penicillin in 1928, and was a boon to humankind. Now, the injuries that would have been fatal were treated and cured using antibiotics. Several dozens of antibiotics were discovered in the period from 1950s-1970s. After that, there has been a void in antibiotic development from the 1990s, and there has been no new antibiotic released since then.
Disadvantages of Antibiotics
One of the reasons why antibiotics became so popular, is that it had very broad activity, which was very well understood at the time. This meant that a single antibiotic could be used for infection caused due to multiple different bacteria, which made diagnosis easier.
Currently, with more understanding of the body’s normal microflora, it was found that the antibiotic decimate even the beneficial bacteria, which harms immunity in the long run. Another disadvantage of antibiotics is the resistance some bacteria develop.
What is antibiotic resistance?
Misuse of antibiotics and the lack of newer drugs has led to the bacteria developing certain mechanisms to protect themselves from the antibiotics used. This essentially leaves the drugs used ineffective. If the bacteria become resistant to all the current antibiotics, we will revert to a pre-antibiotic era, where people die from infections caused due to simple small cuts and scratches.
What is Phage Therapy?
Viruses which are predators of bacteria, specifically are called bacteriophages, or phages for short. Using these phages to tackle bacterial infections is a therapy which has been practiced for centuries, even before the discovery of Penicillin. Eastern European countries has been researching phages as a possible therapy, and now that the antibiotics have stopped working, phage therapy is a valid alternative therapy.
Taking that into account, we worked on a genetically engineered phage as our therapy.
Conventional Phage Therapy: How does it work?
Viral attachment & DNA injection
Bacteriophages seek out compatible bacteria by using the J-protein as recognition factors. They attach to the surface markers on the bacteria and prepare for DNA injection (In case of DNA viruses). Then, viruses employ a wide variety of methods for penetration into the bacteria. All of which lead to the cell wall and membrane being breached and the viral DNA being inserted into the cell.
Degradation or Lytic override
Bacteria with strong immune systems such as CRISPR developed against the Viral DNA degrade the injected phage genome. If the bacteria has a weak immune system, viral genes responsible for lysis are expressed, leading to the production of viral lysis decision proteins.
Replication & Assembly
Viral lysis decision proteins activate viral genes leading to the production of viral protein machinery and DNA. Viral proteins accumulate inside the cell.
Lysis & Release
Viruses burst the bacterial cell after reaching a certain critical concentration, free to infect more cells.
ARM'D UP: A Better Solution
Viral attachment & DNA injection
Uses modified J proteins to recognize bacteria. Phages attach to the surface markers of our choosing and prepare for DNA injection. Viruses employ a wide variety of methods for penetration into the bacteria. All of which lead to the cell wall and membrane being breached and the viral DNA being inserted into the cell.
CRISPR evasion
Unlike the previous case, Degradation is Prevented from happening using the CRISPR evasion system which prevents the maturation of the guide RNA by inhibiting the activity of vital enzyme.
Absence of non-AMR
Expression system is suppressed, forcing the virus into the lysogenic cycle, preventing its destruction. The recombined lysogenic cell is prevented from occurring conversion to AMR by the same system which detects the presence of the resistance genes.
Presence of AMR
AMR genes are recognized by a novel system that we call antisense, which utilizes RNAi along with nuclease activity to detect and destroy resistance mRNAs. In the presence of AMR genes, the expression system is activated, leading to the production of viral proteins and DNA, with modified J proteins to increase range of treatment.
Lysis
Viruses with a different J protein are produced, which can infect a different species or strain of bacteria. This increases the range of treatment while still retaining the super specificity of the viruses.
What happens if a normal cell develops resistance?
If a non-AMR bacterium transforms into an AMR bacterium by means of mutation, transformation, or horizontal gene transfer, the self complementary loops that would have formed in the absence of AMR unfold to bind to the resistance mRNA and this would in turn result in the production of the CRO protein and thus the activation of the viral lytic phase.
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