What is HIV vaccine?

Definition

A
vaccine prevents disease by enabling the body’s immune
response to an infectious agent. Vaccines contain elements of the infectious agent
in preparations not meant to cause disease, but to stimulate production of
antibodies against the infectious agent. These antibodies
prevent disease development. Although rare cases of persons with immunity to the
human
immunodeficiency virus (HIV) have been reported, mostly,
natural immunity to HIV infection has not been effectively isolated or studied.

Development Challenges

Typical vaccine development procedures look at how the body naturally protects itself from reinfection with a disease-causing agent. If someone has mumps or measles as a child, that person will not suffer a second bout with the disease because his or her body has built up a natural immune antibody response to the viruses causing these diseases. Scientists look at antibodies produced by immune people and try to reproduce the same response with a vaccine. Researchers developing HIV vaccines are challenged because they lack this natural immune response model.

HIV infection is not a disease until the infection reduces a certain type of
white blood cell (CD4+ T cells) to a very low level. Once this CD4 count lowers
enough, the HIV infected person will have acquired immunodeficiency
syndrome (AIDS). Vaccines prevent disease, not infection.
People can carry HIV infections for years without developing AIDS. HIV vaccine
development aims to immunize against the infection, and not only against the
disease. This is another significant challenge for HIV vaccine development.

Impact

HIV vaccination provides hope for AIDS disease prevention and for protection against the transmission of HIV infection. Experiments with three main vaccine approaches involve deoxyribonucleic acid (DNA) vaccines, recombinant vector vaccines, and component vaccines. All three approaches aim to produce antibodies against HIV.

DNA vaccines use parts of the HIV genetic code, a tiny ring of HIV DNA called a
plasmid. Needle-free injection technology pushes DNA
plasmids directly into the skin cells and immune cells. Electroporation devices
increase skin cell plasmid uptake by using electrical pulses that open cell pores,
admitting the plasmids. Once inside skin immune cells, the HIV genes produce HIV
proteins (antigens). These antigens would provoke an immune antibody response and
provide protection against HIV infection.

Recombinant vector vaccines use a carrier to bring HIV genes into the body. A part of the HIV genetic code is combined with the genetic code of another virus, a virus that typically does not cause human disease. This recombinant DNA, after introduction to the body, becomes a vector for the HIV genes. As with DNA vaccines, the newly introduced HIV genes would produce HIV antigens, resulting in host antibody production and HIV immunity.

Both of the foregoing techniques involve modern genetic manipulations.
Component or protein vaccines, also known as subunit vaccines, use portions of HIV
to stimulate an immune response. This is the classic type of vaccine, but even
this classic approach now uses modern gene technology. Genetic
engineering is used to produce HIV portions used in these
component vaccines.

HIV vaccine development must overcome intricate challenges. Modern technologies provide hope and promise with this important disease prevention endeavor.

Bibliography

Grandi, Guido, ed. Genomics, Proteomics, and Vaccines. Hoboken, N.J.: John Wiley & Sons, 2004.

Morrow, Matthew P., and David B. Weiner. “DNA Drugs Come of Age.” Scientific American 303, no. 1 (July, 2010) 48-53.

Plotkin, Stanley A., Walter A. Orenstein, and Paul A. Offit. Vaccines. 5th ed. Philadelphia: Saunders/Elsevier, 2008.

U.S. Department of Health and Human Services. “Preventive HIV Vaccines.” Available at http://aidsinfo.nih.gov.

Watkins, David I. “Basic HIV Vaccine Development.” Topics in HIV Medicine 16, no. 1 (March/April, 2008): 7-8. Available at http://www.iasusa.org/pub/topics/2008/issue1/7.pdf.