Lecture 8 - Virology

Endogenous Retroviruses

Overview

• Objective: Understanding an example of an endogenous retrovirus causing disease.

• Focus on the impact of viruses on their animal hosts and the implications for zoonotic diseases.

Zoonotic Diseases Overview

• Definition: Zoonotic diseases (or zoonoses) are infections that spread between animals and humans.

• Example: Ebola Virus Disease

  • Involves both animal hosts and human transmission.

  • Significant public health concern due to its severe outcomes.

Ebola Virus Ecology and Transmission

• Animal-to-Animal Transmission:

  • Bats are the primary reservoir hosts for the Ebola virus.

  • Bats can spread the virus to other animals, including apes, monkeys, and duikers.

• Spillover Events:

  • Occurs when humans or other animals become infected via contact with the reservoir.

  • Often happens through hunting or preparation of wild animal meat.

• Human-to-Human Transmission:

  • Transmission occurs through direct contact with blood, body fluids, or remains of infected individuals.

  • Healthcare workers are at significant risk during outbreaks without proper protective measures.

• Survivor Challenges:

  • Survivors may face physical symptoms, like fatigue and muscle pain.

  • Stigma can affect their reintegration into communities.

Case Study: Koala Retrovirus (KoRV)

• Background:

  • Emerging virus affecting koalas over the last 30-40 years.

  • Notable decline in koala populations, with reductions of 50-60% recorded.

• Discovery:

  • KoRV is an endogenous retrovirus transmitted through germ cells.

  • Similar to gibbon ape leukaemia virus (GALV).

Endogenization of Koala Retrovirus

• Significance:

  • Provides a unique chance to study the history of viral infections in koalas,

  • KoRV-A has been documented as a successful integration into the koala genome.

KoRV Impacts

• Health Outcomes:

  • Evidence does not show direct establishment of lymphomas or immunodeficiencies linked to KoRV-A.

  • Further research needed to understand disease potential.

Infection Status in Zoos

• San Diego vs. Los Angeles Zoos:

  • San Diego Zoo: Low rates of neoplastic diseases due to limited outbreeding.

  • Los Angeles Zoo: Higher neoplastic disease rates due to inclusion of Australian koalas and higher KoRV found.

KoRV Variants and Implications

• KoRV-B Presence:

  • Link between the presence of KoRV-B and increased neoplasia.

  • Differences in viral genomes correlate with differing health outcomes.

Broader Implications of Endogenous Retroviruses

• Investigating the function of endogenous retroviruses in humans, particularly around autoimmunity.

• Link between human endogenous retroviruses (HERVs) and diseases like systemic lupus erythematosus confirmed by ongoing research.

Remaining Questions

• Presence of viral RNA in "Ebola free" patients raises questions about long-term effects of zoonotic viruses.

• Ongoing research aims to uncover underlying mechanisms and potential health impacts of these viral remnants.