Question

1. Explain how animal viruses exhibit host and tissue tropism?

2. How could humans evolve to resist rhinovirus infection? Is such evolution likely? Why or why not?

3. Define host range. Which viruses do you know that have a narrow host range, and which have a broad host range?

4. What roles do viruses play in natural ecosystems?

Please answer all the questions if you dont know all of them please dont answer. Also write neat. Thank you

Answer 1

Question 1

Host tropism refer to the process where virus or any other pathogen decide which cells could be easily infected by them. The host tropism is decided by the :

I. Biochemical receptor complex present on the cell surface of the host.

II. The cells of the host must be susceptible as well as permissiveness to establish virus infection.

For example, HIV virus show tropism for CD4 cells in case of AIDS.

Similarly, tissue tropism means the specific tissue in the body of host that are easily attacked by virus and other pathogen and easy to replicate there. The tissue tropism is decided by these factors:

I. Presence of specific receptor that help in attaching to the virus.

II. Presence of transcription factor that help in replication of virus.

III. Viral tropogen molecular nature.

Question 2

Human rhinovirus are mainly responsible for causing respiratory problem in humans. These virus mainly have receptor for the attachment of specific cells of human. These cells in human are " ICAM1 " (intercellular adhesion molecule 1 and "LDLR" (low density lipoprotein receptor). Human could evolve to resist this virus infection by changing these two receptor protein structure. Such evolution are less likely to occur because these two proteins play an important role in the cell- cell interaction. If their structure get disturbed, they might lose their function.

Question 3

The host range means range of host that could be infected with given strain of virus. Small pox virus are having narrow host range because they could infect only humans. Bacteriophage are broad range virus

Question 4

Viruses play an important role in the marine ecosystem. They are able to destroy harmful algal blooms that kills the other organism in marine ecosystem. They are also imortant in carbon recycling in nature.