Dr Richard Hunt

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VIROLOGY - CHAPTER  SEVEN    

HUMAN IMMUNODEFICIENCY VIRUS AND AIDS  

PART ONE   

INTRODUCTION

VIDEO LECTURE

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VIDEO
25th anniversary of the discovery of the Human
Immunodeficiency Virus (HIV)

Jon Cohen
on AIDS in Latin America and the Caribbean
Science/BioCompare
 

The world pandemic of AIDS (Acquired Immunodeficiency Disease Syndrome) has been with us for more than twenty years and shows no signs of abatement. Three million people around the world die of AIDS each year and, so far, more than 25 million people have died of the disease. Today, at least 33 million people are infected and there are more than 14,000 new infections every day.

Since the late 1970's, HIV and AIDS have spread across the United States (figure 1) and around the world. In sub-Saharan Africa, more than 22 million people are living with HIV infection.

Despite major success in treating infected people in western countries, the disease has become the major cause of death in many third world countries in which chemotherapy reaches only a minority of the infected population. Attempts at making a vaccine have so far proved unsuccessful.

AIDS is caused by Human Immunodeficiency Virus (HIV) which is found in all cases of the disease. The primary targets of HIV are activated CD4+ T4 helper lymphocytes but it can also infect several other cell types including macrophages. It is the loss of T4 helper lymphocytes that leads to immunosuppression in the patient and the consequent fatal opportunistic infections.

HIV is a lentivirus, a class of retrovirus. The name lentivirus means slow virus, so called because these viruses take a long time to cause overt disease. Most lentiviruses target cells of the immune system and thus disease is often manifested as immunodeficiency. There are five known serogroups of lentivirus that infect primates, sheep and goats, horses, cats, and cattle.

There are two types of HIV: HIV-1 and HIV-2. These cause clinically indistinguishable disease, although the time to disease onset is longer for HIV-2. The worldwide epidemic of HIV and AIDS is caused by HIV-1 while HIV-2 is mostly restricted to west Africa.

Lentiviruses integrate into the host cell genome as a provirus in the same manner as other retroviruses. Unlike other retroviruses, which typically bud from the infected cell for a long period of time, HIV can lie dormant in the proviral form within a cell for many years, especially in resting (memory) CD4+ T4 lymphocytes, and may set up a lifelong infection. When these cells become reactivated, viral production occurs again and ultimately destroys the cell. Although HIV may disappear from the cells of the circulation, replication and budding continue to occur in other tissues in the absence of chemotherapy.  Unlike many other retroviruses, HIV is not transmitted through the germ line. 

In the infected patient, HIV can be detected by the presence of anti-HIV antibodies or by the presence of the virus itself using polymerase chain reaction (PCR) that detects viral RNA. PCR is very sensitive and can show HIV in situations in which it is not detectable immunologically.  

Frequently asked questions about HIV and AIDS

How many people, worldwide, are living with HIV infection today?  Go here	How many people are living with HIV infection in various regions of the world? Go here		What proportion of infected people in various regions are women? Go here
What are the major mechanisms of HIV transmission in different regions of the world? Go here		What is the proportion of the adult population (15-49 years of age) in different regions of the world that is living with HIV or AIDS? Go here
How many people have been infected by HIV in South Carolina? Go here or click on image	Reported cases of AIDS in South Carolina by race and sex 1990-2006 SC-DHEC	AIDS/HIV infection diagnosis by race in South Carolina by race and sex 1990-2005 SC-DHEC	AIDS distribution in South Carolina by county - 2005 SC-DHEC

WEB RESOURCES
South Carolina AIDS surveillance data
pdf

OTHER SECTIONS ON HIV

PART I HUMAN IMMUNODEFICIENCY VIRUS AND AIDS

PART II HIV AND AIDS, THE DISEASE

PART III COURSE OF THE DISEASE

PART IV PROGRESSION AND COFACTORS

PART V STATISTICS

PART VI  SUBTYPES AND CO-RECEPTORS

PART VII  COMPONENTS AND LIFE CYCLE OF HIV

PART VIII  LATENCY OF HIV

PART IX GENOME OF HIV

PART X  LOSS OF CD4 CELLS

PART XI  OTHER CELLS INFECTED BY HIV AND POPULATION POLYMORPHISM

APPENDIX I  ANTI-HIV VACCINES

APPENDIX II  DOES HIV CAUSE AIDS?

APPENDIX III  ANTI-HIV CHEMOTHERAPY