Transfusion Transmitted Infections Overview

Study Notes

Transfusion Transmitted Infections (TTIs)

Transfusion-transmitted infections (TTIs) are infections caused by introducing a pathogen into a person via blood transfusion.
Objectives for the lecture include outlining blood bank measures to reduce TTI risk, blood donation criteria, and the factors involved in TTI establishment. The lecture also aims to name common pathogens, describe their characteristics, modes of transmission, pathogenesis, and diagnostic approaches.
Blood transfusion is the process of receiving blood or blood products intravenously. It is used to replace lost blood components or as a therapy.

Common Infectious Diseases Transmitted Through Blood Transfusion

RNA Viruses:
- HIV (Human Immunodeficiency Virus): The causative agent of AIDS. Enveloped, single-stranded RNA virus. Transmitted sexually, parenterally (blood transfusion, needle-sharing), tissue transplantation, and vertically (during pregnancy, childbirth, and breastfeeding)
- HTLV (Human T-cell Lymphotropic Virus): An oncogenic virus causing adult T-cell leukemia and lymphomas. Transmitted sexually, through blood transfusion, breast-feeding, and vertically.
- HCV (Hepatitis C Virus): An enveloped, single-stranded RNA virus causing hepatocellular carcinoma. Transmitted parenterally through needle sharing, blood transfusions, dialysis, and organ transplantation (less commonly, sexually and vertically).
DNA Viruses:
- HBV (Hepatitis B Virus): Double-stranded DNA virus, commonly causing hepatocellular carcinoma. Transmitted via sexual contact, contaminated needles, blood transfusions, organ transplants, and vertically.
- EBV (Epstein-Barr Virus): Enveloped DNA virus, known for causing infectious mononucleosis. Transmitted primarily through saliva. Blood transfusion and organ transplant may also be involved.
- CMV (Cytomegalovirus): Enveloped DNA virus commonly latent and asymptomatic. Transmitted by body fluids (especially saliva), sexually, vertically, and through blood transfusions and organ transplants.
Other agents:
- HHV-8 (Human Herpesvirus-8): Causes Kaposi's sarcoma (a tumor of endothelial cells). Transmitted through saliva, blood transfusion, and vertical transmission.
- Parvovirus B19: Non-enveloped DNA virus, causing anemia, abortion, polyarthritis, and aplastic crises. Transmitted via respiratory droplets, blood transfusion, and vertically.
- Bacteria (e.g., Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Klebsiella, Proteus, Yersinia enterocolitica): Often a result of improper donor procedures.
- Treponema pallidum (Syphilis): A bacterium; transmitted sexually and vertically, through blood transfusions.
Protozoa:
- Plasmodium species (Malaria): Transmitted through the bite of infected mosquitoes, transplacentally, and through blood transfusion. A parasite invading red blood cells and hepatocytes.
- Toxoplasma gondii: Causes toxoplasmosis. Transmitted through ingestion of contaminated foods or water, vertical transmission, and blood transfusions

Reducing the Risk of TTIs

Standard donor screening questionnaires
Screening of blood:
- PCR
- Bacterial cultures
- Antigen/antibody detection (e.g., HBV, HCV, HIV, HTLV, syphilis)
Pathogen inactivation techniques (chemicals and/or UV light)

Criteria for Blood Donation and Rejection

Age: 17-65 years old.
Weight: 50 kg or above
Normal pulse rate
Normal body temperature
Normal blood pressure
Hemoglobin concentration: >12 g/dL (women), >13 g/dL (men)
Medical history: Epilepsy, psychotic disorders, severe bleeding tendencies, thalassemia, sickle cell anemia, or malignancy
Infection: HIV, hepatitis, malaria, and syphilis

Factors in TTI Establishment

Viral window period (time between infection and detection)
False-negative lab results
Bacterial contamination
Asymptomatic, immunocompetent donors
Laboratory errors
Personal errors

HIV Replication Cycle

Adsorption: HIV attaches to CD4+ T-helper cells
Uncoating: Viral RNA released
Reverse transcription: Viral RNA converted to DNA
Integration: Viral DNA incorporated into host DNA
Transcription and protein synthesis
Assembly
Release: Budding from cell

Other Important Details

Pathogenesis describes how an infection develops.
Diagnosis methods include specific tests targeting the organism, antibodies, or viral nucleic acids.
Complications from TTIs can include splenic rupture, malignancies (like lymphoma), and other organ damage.