Introduction
- Using laboratory animals in viral culture has been critical in virology research, particularly for studying viral pathogenesis, vaccine development, and therapeutic interventions.
- While animal cell cultures have become the primary method for growing viruses, certain viruses still require live animal hosts for propagation, isolation, or study.
- Laboratory animals are also used to study the immune response to viral infections and to test antiviral drugs.
Role of Laboratory Animals in Virology
- Laboratory animals provide an in vivo environment for viruses that either do not grow well in cell cultures or are difficult to isolate from human or environmental samples.
- They serve as models for understanding virus replication, transmission, pathogenesis, and the host immune response.
- Animal models also enable the developing and testing of vaccines, antiviral drugs, and other therapies.
Common Laboratory Animals Used in Viral Culture
Mice (Mus musculus)
Mice are the most commonly used laboratory animals in virology due to their genetic homogeneity, small size, and well-established immunological profiles.
- Use in Virology:
- Viral Infections: Mice are used for propagating and studying a variety of viruses, including influenza, herpes viruses, rabies, coronavirus, and mouse-adapted strains of human viruses.
- Host Response: Mice are valuable for studying how viruses interact with the immune system, the progression of infection, and the effects of viral vaccines and treatments.
- Genetically Modified Mice: Transgenic mice or knockout mice can be engineered to express specific genes or lack others, providing insights into the role of particular proteins or receptors in viral infections.
- Examples of Viruses Studied in Mice:
- Influenza virus: Mice are often used to study influenza pathogenesis and to test antiviral drugs like oseltamivir.
- Lymphocytic choriomeningitis virus (LCMV) infects mice and is commonly used in immune response and neurotropism studies.
- West Nile virus (WNV): Mice serve as a model for studying neuroinvasive infections caused by WNV.
Rats (Rattus norvegicus)
Rats are used in viral research for similar purposes as mice but offer certain advantages, such as a larger size for tissue sampling and longer observation periods.
- Use in Virology:
- Infection Models: Rats study respiratory infections (e.g., respiratory syncytial virus, influenza) and hepatitis viruses.
- Vaccine Development: Rats are used in preclinical testing of vaccines for hepatitis B, rabies, and enteric viruses.
- Drug Testing: Rats are often used to evaluate antiviral drug efficacy and toxicity.
- Examples of Viruses Studied in Rats:
- Hantavirus: Rats have been used to study hantavirus infections, especially in the lungs and kidneys.
- Herpesvirus: Rats have been used to study certain herpesviruses (e.g., cytomegalovirus) and neuroinvasive infections.
Guinea Pigs (Cavia porcellus)
Guinea pigs are especially important in immunology and vaccine research, as they have a similar immune system to humans, making them suitable for studying human-related infections.
- Use in Virology:
- Viral Infections: Guinea pigs are used to propagate respiratory viruses and herpes viruses.
- Allergic Reactions: Guinea pigs are often used to study allergic diseases triggered by viruses or investigate antiviral treatments’ effectiveness.
- Vaccine Testing: They are used to develop vaccines for tuberculosis, pneumonia, and HIV.
- Examples of Viruses Studied in Guinea Pigs:
- Coxsackievirus: Guinea pigs are often used to study enteroviral infections like coxsackievirus.
- Pneumovirus includes human metapneumovirus (hMPV), which can cause upper respiratory tract infections.
Non-human Primates
Non-human primates, such as rhesus monkeys (Macaca mulatta) and squirrel monkeys (Saimiri spp.), share a high degree of genetic similarity with humans, making them invaluable for studying human-like viral infections.
- Use in Virology:
- Model for Human Infections: Non-human primates study viruses that infect humans, including HIV, hepatitis C, Zika virus, and Ebola.
- Vaccine Development: They are essential in the preclinical evaluation of vaccines, such as HIV and Ebola.
- Antiviral Drug Testing: Monkeys are often used to test antiviral drugs, as their responses to treatment closely mimic those in humans.
- Examples of Viruses Studied in Non-human Primates:
- HIV: Rhesus monkeys are used to study the pathogenesis of HIV infections and to test HIV vaccines and therapies.
- Ebola: Non-human primates are a key model for testing Ebola virus vaccines and understanding the pathology of hemorrhagic fever.
Chickens (Gallus gallus domesticus)
Chickens, particularly embryonated eggs, have long been used in virology for virus propagation, especially for viruses that infect birds or require specific cell types for replication.
- Use in Virology:
- Viral Propagation: Chicken embryos (embryonated eggs) are used to grow avian influenza and other avian viruses.
- Vaccine Production: Embryonated eggs are used to produce vaccines, such as flu vaccines.
- Viral Study: Chicken models are used to study viruses such as Newcastle disease virus and avian influenza.
- Examples of Viruses Studied in Chickens:
- Avian influenza: Embryonated eggs are used to study various strains of avian influenza and develop vaccines.
- Newcastle disease virus infects poultry, and chickens are used to study virus pathogenesis and immune responses.
Advantages of Using Laboratory Animals in Viral Culture
- Complex Host Response: Animals provide a more complex and accurate representation of the immune system’s response to viruses than cell culture.
- In Vivo Pathogenesis: Animals allow the study of viral pathogenesis—how the virus spreads and causes disease in different tissues and organs.
- Vaccine Development: They are indispensable in developing and testing new vaccines and antiviral therapies before clinical trials.
- Virus Characterization: Animal models help characterize new viruses, understand their transmission, and study the severity of infection in a whole organism.
Limitations of Using Laboratory Animals in Viral Culture
- Ethical Concerns: Using animals in research raises ethical concerns regarding animal welfare. Researchers must follow strict guidelines and ensure humane treatment.
- Cost and Resources: Animal research requires significant resources, including care, maintenance, and specialized facilities.
- Limited Virus Spectrum: Not all viruses can be cultured or studied in all animal species. Some viruses only infect specific species or require specific environmental conditions.
- Species Differences: The immune response or pathogenesis in animals may not fully mimic human conditions, potentially limiting the extrapolation of results to human diseases.