Type: Prelims Only

Why in the News?

Researchers in Sweden have developed a new blood test, PrecivityAD2, which is about 90% accurate in identifying Alzheimer’s Disease (AD) in people experiencing cognitive symptoms.

What is Alzheimer’s Disease (AD)?

• Alzheimer’s disease is the most common type of dementia (loss of memory and cognitive abilities).
• It is a progressive disease beginning with mild memory loss and possibly leading to loss of the ability to carry on a conversation and respond to the environment.
• Alzheimer’s disease involves parts of the brain that control thought, memory, and language.
• Brain cell connections and the cells themselves degenerate and die, eventually destroying memory and other important mental functions.
• Memory loss and confusion are the main symptoms.
• No cure exists, but medication and management strategies may temporarily improve symptoms.

How PrecivityAD2 Test works?

• The test measures a combination of two ratios within a blood sample:

1. Plasma Phosphorylated-tau217 (p-tau217) to Not-Phosphorylated-tau21: The test measures the ratio of p-tau217 to non-phosphorylated tau21. Tau proteins are associated with the formation of neurofibrillary tangles in the brain, a hallmark of AD.
2. Amyloid-beta (AB42 and AB40): The test also measures the ratio of two types of amyloid-beta proteins, AB42 and AB40. Amyloid plaques are another key pathological feature of AD.

• Both tau and amyloid-beta proteins are considered pathological hallmarks of AD.

Benefits of PrecivityAD2

• Early Detection: PrecivityAD2 can diagnose AD at the early stage of mild cognitive impairment, enabling timely intervention and management.
• Accurate Identification: With an accuracy rate of around 90%, the test provides reliable results, reducing the chances of misdiagnosis.
• Non-Invasive: Unlike current diagnostic methods that involve complex PET scans or lumbar punctures, PrecivityAD2 requires only a simple blood draw.
• Cost-Effective: The test is expected to be more affordable compared to expensive PET scans and cerebrospinal fluid analysis, making AD diagnosis more accessible.
• Ease of Use: The blood test simplifies the diagnostic process, making it easier for primary care physicians to screen for AD.
• Wider Reach: By reducing the complexity and cost of diagnosis, more patients can be tested, particularly in resource-limited settings.

Significance of the Test

• Standard of Care: PrecivityAD2 has the potential to become the standard first-line test for AD diagnosis, replacing more invasive and costly methods.
• Support for Early Intervention: Early and accurate diagnosis allows for timely intervention, which is crucial for managing AD and improving patient outcomes.
• Reduction in Misdiagnosis: The test’s high accuracy rate can help reduce the rates of misdiagnosis, particularly in primary care settings.

Feasibility for India:

• In India, the current diagnostic tools for Alzheimer’s disease primarily include MRI and regular PET scans.
• Advanced diagnostic tools like amyloid or Tau PET scans are not yet commercially available.
• The introduction of PrecivityAD2 in India will require approval from the Drug Controller General of India (DCGI) and other relevant regulatory bodies.

Why in the News?

Research suggests that around 8% of the human genome is composed of Endogenous Retroviruses (ERVs) often referred to as ‘zombie’ regions.

What are Endogenous Retroviruses (ERVs)?

• ERVs are remnants of ancient viral infections that have integrated into the genome of the host species.
• When these retroviruses infect germ cells (sperm or egg cells), their genetic material can be passed down to the next generation, becoming a permanent part of the host’s DNA.
• Zombie Regions:
  • They refer to inactive viral sequences within the genome that no longer produce functional viruses but remain as embedded genetic fossils.
  • These regions are a result of retrovirus integration that has lost its ability to replicate and produce proteins, yet they persist in the host’s DNA.

Evolutionary Significance of ERVs:

• In the life cycle of a retrovirus, reverse-transcribed DNA is integrated into the host’s DNA with the help of integrase.
• The viral DNA, called a provirus, hijacks human cells, turning them into virus-making factories.
• Over tens of thousands of years, many retroviruses have left genomic elements in human genome, contributing to evolutionary processes.
• Example:
  • Syncytins are genes thought to have descended from ERVs and are crucial for placental development. These genes originally came from viruses and were acquired during mammalian evolution.

Their Contribution to Human Biology

• ERVs are highly expressed in the placenta and may influence conditions like preeclampsia.
• Researchers found that a particular RNA derived from an ERV is dysregulated in early-onset preeclampsia, suggesting it could be used as a biomarker for the condition.
• ERVs play a role in cell-type differentiation during embryo development.
• A protein called MERVL-gag is derived from an ERV. This transition is crucial for producing pluripotent stem cells capable of forming different cell types.
• Researchers also found that a human ERV element LTR10 affects tumour formation in colorectal cancer.