Human Immunodeficiency Virus

Human Immunodeficiency Virus: The debate, the facts, and the

history since the 1980s

Casey Jordan Elison

Treasure Valley Community College

Abstract:

The exact origin of Human Immunodeficiency Virus (HIV) has been a debate and controversial topic since it was first recognized in the 1980’s. We have discovered what viruses are, their anatomy, how they affect hosts, and how they replicate, yet many viruses have continued to baffle us. A virus may or may not be living. The debate on this topic though, has remained alive and well. HIV is a virus as determined by its structure and specified in its name, but HIV is indeed very much a separate viral entity of which we have learned more about regularly. As of current, we have defined what HIV is, what it looks like, and the various types, groups, and sub-types. Beyond the structure of the virus and its biology, we have come to know the primary host cells, how it replicates, how it is spread, and what we, as the primary hosts, have been doing in an attempt to eliminate it. With all that we have learned about HIV, it is still fascinating that the origin of its existence and the means to its destruction are still conglomerations of theories.

Body:

Human Immunodeficiency Virus

The word virus originated as the Latin term for poison. This is very appropriate for its function, that being to harm. A virus is a nonliving particle, microscopic in size that infects the cells of a truly living organism. The basic structure of a virus, also referred to as a virion, is a nucleic acid surrounded by a covering (coat) known as a capsid. Capsids are formed from separate protein units called capsomers wrapped around a nucleic acid, hence the common name of “protein coat”. The morphology of this capsid (protein coat) is the primary source of categorization into viral types. There are four (4) main morphological virus types.

1) Helical viruses: composed of only one (1) capsomer stacked around a center core tube resembling a spiral staircase. This virion’s genetic material is enclosed inside the tube. 2) Icosahedral viruses: viruses that appear spherical in shape. They are made of multiple copies of capsomers that construct a ring bonded together to enclose the viral nucleic acid. 3) Enveloped viruses: a virus of which has a capsid surrounded by a modified form of the infected host cell’s cell membrane. This surrounding membrane constructs the “envelope”. 4) Complex viruses: a virus of which the capsid is neither icosahedral, nor helical, and usually has extra structures. These extra structures include: protein tails, or complex outer walls. Some even have a combination of all.

As viruses are acellular and unable to reproduce they must go through a process known as replication. The first stage of replication is absorption. Absorption is the contact with a host cell and attachment to the cell surface. The virus must then infect that host cell (penetration). Viruses enter the cell in different ways depending on the type and structure of the virus. Some inject their nucleic acid while attached to the outer wall of the cell, while others enter the cell as a whole particle and must uncoat themselves. At this point the nucleic acid of the virus merges and/or overruns the host cells own DNA, and uses the host cell for a process known as replication/duplication. After replicating/duplicating, the virus must then be assembled inside of the host cell and released. Release is usually achieved by the death of the host cell, although there are some exceptions to this.

Replication of a virus in a host cell has multiple effects on the morphology of the cell itself and/or to the genetic material of the host. Any morphological change to a host cell is classified as cytopathic effect. These cytopathic effects or virus-induced damage to cells often include cell rounding, disorientation, swelling or shrinking, detachment from the surface, cell death, and/or cell self destruction (lysis).

The argument as to whether or not viruses are alive still continues. While there is no difficulty in classifying organisms such as humans, or dogs. Viruses are a little more complicated. Viruses possess nucleic acid and are able to respond in a limited way to their environment. They also reproduce in a sense by replicating themselves, but they don’t have the cell structure that is used to classify the basic unit of life. The fact that viruses reproduce is also debatable