PCR AND ELISA

Polymerase Chain Reaction (PCR)
Polymerase Chain Reaction (PCR) is a widely used laboratory technique in molecular biology to amplify specific DNA sequences. It was developed by Kary Mullis in 1983. The process involves the following steps:

• Denaturation: The double-stranded DNA is heated to separate it into two single strands.
• Annealing: The temperature is lowered to allow primers to attach to the DNA template.
• Extension: DNA polymerase extends the primers to form a new DNA strand.

PCR is essential for various applications, including genetic research, medical diagnostics, forensic science, and biotechnology. It allows for the detection and analysis of DNA even from small or degraded samples.

Enzyme-Linked Immunosorbent Assay (ELISA)
Enzyme-Linked Immunosorbent Assay (ELISA) is a common laboratory technique used to detect and quantify antigens (proteins, hormones, and antibodies) in a sample. The procedure involves the following steps:

• Coating: An antigen is immobilized on a solid surface, typically a microplate.
• Blocking: Non-specific binding sites are blocked with a blocking agent.
• Binding: A specific antibody is added, which binds to the antigen.
• Detection: A secondary antibody, conjugated with an enzyme, binds to the primary antibody.
• Substrate Addition: A substrate is added, which the enzyme converts into a detectable signal, usually a color change.  

ELISA is widely used in diagnostics for diseases, including HIV, and in various research applications to measure the concentration of substances in biological samples. It is valued for its sensitivity, specificity, and versatility.

Category

Details

Definition

Viruses transmitted by arthropods (e.g., mosquitoes, ticks).

Transmission Vectors

Mosquitoes (e.g., Aedes, Culex), Ticks (e.g., Ixodes), Sandflies, and other arthropods.

Human Diseases

Dengue Fever, Zika Virus, Chikungunya, Yellow Fever, West Nile Virus, Japanese Encephalitis.

Symptoms

Fever, headache, rash, joint pain, muscle pain, hemorrhage, encephalitis (varies by virus).

Geographical Spread

Tropical and subtropical regions; some arboviruses are found in temperate zones.

Prevention

Vector control (e.g., mosquito nets, insect repellents), vaccination (for specific viruses), surveillance.

Diagnosis

Serological tests (e.g., ELISA), molecular tests (e.g., PCR), viral culture.

Treatment

Mostly supportive care; antiviral treatments are limited; vaccines available for some (e.g., Yellow Fever).

Notable Arboviruses

Dengue Virus, Zika Virus, Chikungunya Virus, Yellow Fever Virus, West Nile Virus, Japanese Encephalitis Virus.

Aspect

Details

Objective

To enhance global capacity to detect, prevent, and control arbovirus outbreaks.

Initiating Organization

World Health Organization (WHO).

Key Activities

- Strengthening surveillance systems for early detection.

- Coordinating research efforts to develop vaccines and treatments.

- Enhancing public health response capabilities.

- Promoting vector control strategies.

- Facilitating information sharing and collaboration among countries.

Significance

Addresses the rising threat of arbovirus outbreaks due to factors like climate change and urbanization.

Impact

Aims to reduce the incidence and burden of arbovirus-related diseases globally.

Aspect

Details

Scientific Family

Psychodidae

Subfamily

Phlebotominae

Common Genera

Phlebotomus (Old World), Lutzomyia (New World)

Distribution

Tropical and subtropical regions, including parts of Asia, Africa, the Americas, and the Mediterranean

Habitat

Humid environments; typically found in forested areas, caves, and animal burrows

Behavior

Nocturnal; most active during dawn and dusk

Feeding

Female sandflies feed on blood for egg development; males feed on plant juices

Reproduction

Females lay eggs in moist environments; larvae develop in organic-rich soil

Disease Transmission

Vectors for diseases like leishmaniasis, Chandipura virus, and bartonellosis

Control Measures

Insect repellents, bed nets, environmental management to reduce breeding sites

Aspect

Details

Scientific Classification

Family: Rhabdoviridae

Genome

Single-stranded negative-sense RNA

Structure

Enveloped, bullet-shaped or bacilliform virions

Genera

Lyssavirus, Vesiculovirus, Novirhabdovirus, and more

Notable Species

Rabies virus (Lyssavirus), Vesicular stomatitis virus (Vesiculovirus), Chandipura virus (Vesiculovirus)

Hosts

Vertebrates (mammals, fish) and invertebrates (insects)

Transmission

Bites (e.g., rabies), insect vectors (e.g., sandflies for Chandipura virus)

Diseases

Rabies, vesicular stomatitis, encephalitis (e.g., Chandipura virus infection)

Diagnosis

PCR, ELISA, virus isolation

Prevention

Vaccination (e.g., rabies), vector control, protective clothing

PRACTICE QUESTION

Q: With reference to the Rhabdoviridae family, consider the following statements:

1. The Rhabdoviridae family includes viruses that infect animals, plants, and humans.
2. Rabies virus is a member of the Rhabdoviridae family.
3. All Rhabdoviridae viruses have a segmented genome.

Which of the statements given above is/are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2, and 3

Answer: (a)