HIV stands for human immunodeficiency virus. It is contracted by sexual contact, contaminated blood, and mother-to-child transmission. It targets T lymphocytes, cells that are vital for a healthy immune system. HIV gradually weakens the immune system over the long term, and sufferers develop serious diseases, known as “opportunistic diseases” as they are caused by microorganisms that are harmless for those with a healthy immune system.
Acquired immunodeficiency syndrome (AIDS) is the final stage of HIV infection, when those infected develop one or more opportunistic diseases.
The clinical symptoms of HIV vary according to the different stages of the disease. The first stage is known as primary infection, when those infected may have no symptoms or may develop flu-like symptoms after an incubation period of several weeks (high fever, muscle pain, headaches, diarrhea).
After the primary infection stage comes an asymptomatic stage that can last for several years. During this period, the virus is more discreet, but those infected remain contagious. HIV gradually weakens the immune system, leading to other symptoms such as weight loss, fever, skin infections, diarrhea, and cough.
If left untreated, the disease develops into acquired immunodeficiency syndrome, or AIDS, the final stage of HIV infection. This stage is characterized by the emergence of “opportunistic” diseases, which take advantage of the weakened immune system. AIDS sufferers may contract any number of bacterial, fungal, and parasitic infections, as well as some cancers.
Treatments have been developed to stop HIV spreading in seropositive patients, allowing them to maintain a functional immune system. These treatments are known as triple therapies or multiple therapies, since they combine several antiretroviral molecules. Antiretroviral drugs can cause side effects, including nausea, vomiting, tiredness, loss of appetite, fever, diarrhea, and skin reactions. There is currently no treatment that can completely eliminate HIV from the body. Although there is no available vaccine, individuals that are under retroviral treatment and with low viral loads are less prone to transmit the virus.
Resistance to the virus in rare cases
Some HIV carriers show no symptoms for several years – these “Elite controllers” (roughly less than 1% of those infected with HIV) can go for more than a decade without developing AIDS in the absence of antiretroviral treatment. A tiny percentage of Caucasians (less than 1%) are even resistant to HIV infection. This resistance is caused by a mutation in the “CCR5” chemokine receptor gene, which is a receptor for the virus.
Emergence in the 1980s
AIDS was first described in 1981, but retrospective studies on serum specimens from Zaire (now Congo) indicate that the virus has existed since 1959 and had already spread within Africa between 1970 and 1980. It is possible that HIV was originally contained within an isolated population before spreading as a result of increasing urbanization and population movements. At least thirty African monkey species (including chimpanzees, green monkeys, mangabeys, and mandrills) are naturally infected by retroviruses closely related to HIV known as simian immunodeficiency viruses (SIVs), which do not result in AIDS in these animals.
One of the two human viruses, HIV-2, is closely related to the SIV that infects mangabey monkeys living in West Africa. It is therefore possible that humans may have been contaminated after being bitten by these monkeys. HIV-1 may have been spread by chimpanzees; some chimpanzees in Cameroon and Gabon are carriers of an SIV that is closely related to HIV-1. It is difficult to give a precise estimate of when these viruses might
Since 1981, when the HIV epidemic was discovered, the virus has spread from Africa to North America and subsequently to Europe. Homosexuals with multiple partners were the first to be affected in the United States. The epidemic was then observed in blood transfusion patients, hemophiliacs, and drug addicts, emphasizing the risks of blood-borne transmission. In Asia, the disease only emerged around 1986-87, firstly in Thailand and then in other Southeast Asian countries. Prostitution and intravenous drug use were major factors in the spread of HIV in these countries. The most common mode of HIV transmission worldwide is currently heterosexual intercourse. It is estimated that some 34 million people are currently infected.
At the Institut Pasteur
Research on HIV/AIDS is one of the major targets of the Institut Pasteur in Paris and the Institut Pasteur International Network, in the countries that are most affected by the epidemic.
In Paris, around ten teams are focusing on HIV. Their work covers most of the current priority research areas, particularly the development of infection, virus variability, mechanisms by which HIV enters and replicates in human cells, virus transmission (including mother to child) and regulation, the pathophysiology of infection, human immune response to the virus, natural protection in humans, and treatments and candidate vaccines.
This research is carried out in close partnership with the French National Agency for Research on AIDS and Viral Hepatitis (ANRS), and the Vaccine Research Institute (VRI).