Infectious Disease Target

What is Infectious Disease?

Infectious diseases in this case are a group of diseases which are caused by pathogenic organisms such as bacteria, viruses, fungi and parasites. They are usually harmless and can be found in or on the human body and are part of its normal flora. Nonetheless, they become pathogenic under certain circumstances such as when the immune system is weakened or where a new strain of pathogen is introduced. Transmission of infectious diseases occurs via multiple pathways: can be transmitted from one person to another, from one person to another through a vector such as an insect or an animal or through ingestion of food or water that has been contaminated. Other examples of infectious diseases include the recent COVID-19 whose cause is the SARS-CoV-2 virus; HIV/AIDS, which attacks the immune system; Tuberculosis, a bacterial disease that affects the lungs; and malaria which is a disease transmitted by mosquitoes.

Infectious Diseases and Their Mechanisms of Action (MOA): A Comprehensive Overview

Infectious diseases are diseases which are caused by pathogenic microorganisms including bacteria, viruses, fungi and parasites that invade and affect host organisms. It is important to classify these diseases based on the mechanism of action in order to understand the reasons behind their occurrence and in order to create different therapeutic and preventive strategies. Below, we outline the primary MOAs utilized by pathogens to cause disease:Below, we outline the primary MOAs utilized by pathogens to cause disease:

1. Direct Cellular Damage

MOA: Lysogeny is the process where pathogen directly damage or kill host cells as a means of their life cycle or through the secretion of toxins.

• Bacterial Example: Pneumonia is caused by Streptococcus pneumoniae by invading and damaging lung tissues.

• Viral Example: The Influenza virus affects the cell death in the respiratory part of the body.

2. Toxin Production

MOA: The pathogens release toxins that affect normal cell functionality or cause cell death resulting into the symptoms of the disease.

• Bacterial Example: It is Clostridium botulinum which releases a poisonous substance known as botulinum toxin causing an illness known as botulism.

3. Immune Response-Mediated Damage

MOA: Pathogens cause an over expression or an unmodulated immune response that is detrimental to the host’s tissues.

• Bacterial Example: Streptococcus pyogenes can cause rheumatic fever that implies that the immune system affects the heart.

• Viral Example: Severe dengue is caused by the Dengue fever virus where immune system is involved in the vascular leakage and shock.

4. Mechanical Blockage

MOA: Pathogens mechanically interfere with the ducts or passages of the body thus hindering normal functioning.

• Parasitic Example: Ascaris lumbricoides the round worm affects the large intestine and causes intestinal obstruction.

5. Exploiting Host Resources

MOA: Pathogens are parasites that require the host for food, reproduction and shelter, and they may cause diseases that affect the host’s nutrition or drain the host’s nutrient reserves without killing it.

• Parasitic Example: Plasmodium spp. Malaria is a disease that parasites red blood cell for reproduction.

• Bacterial Example: In the so called latent TB infection, Mycobacterium tuberculosis is known to feed on the host nutrients.

This classification therefore helps to make the point that pathogens can cause disease in a number of ways and that pathogens are not all alike and interactions with hosts are not simple. Further elucidation of these MOAs is important for the development of countermeasures against infectious diseases.

 

Table of Therapeutic and Diagnostic Targets in MOA-Based Infectious Diseases

In the area of infectious diseases, knowing the mode of action of the pathogens is vital for the formulation of appropriate treatments as well as improvement of diagnostic procedures. The following is a table showing the major MOAs and the therapeutic and/or diagnostic targets that are implicated with them. It offers a systematic approach by relating certain pathogens to possible interventions whilst emphasizing on molecular or cellular markers that are useful in recognizing infections. This systematic approach helps the researchers and clinicians to understand the management of the infectious diseases and for that the concept of precision medicine has been introduced for better treatment and diagnosis.

MOA	Pathogen Type	Therapeutic Target	UniProt ID	Therapeutic Example	Diagnostic Biomarker	Diagnostic Method
Direct Cellular Damage	Viral	HIV protease	P03367	Ritonavir (HIV)	Viral RNA or DNA	PCR
	Bacterial	Penicillin-binding proteins (PBPs)	Varies	Penicillin (Streptococcus pneumoniae)	Pathogen identification	Culture and sensitivity testing
Toxin Production	Bacterial	Botulinum toxin	P10844	Antitoxin (Botulism)	Toxin detection	Serum, stool, or food samples testing
Immune Response-Mediated Damage	Various	Immunosuppressants/Corticosteroids	-	Corticosteroids (Severe dengue)	Antibodies, CRP	Serology, CRP testing
Mechanical Blockage	Parasitic	Antihelminthic drugs	-	Albendazole (Ascaris lumbricoides)	Eggs or larvae	Stool samples
Exploiting Host Resources	Parasitic	Antiparasitic drugs (Plasmodium metabolism)	-	Artemisinin (Malaria)	Parasites in blood