Human Immunodeficiency Virus Flashcards
Retrovirus
HIV is a retrovirus, which means it is an RNA virus that is transcribed to DNA that inserts in the host genome.
Lentivirus
It is also a lentivirus, which means that it replicates slowly. There can be long gaps in time between infection and symptoms
Seroconversion
HIV can spread via blood or blood products, needles, semen, rectal or vaginal fluids, or breast milk. The virus preferentially infects CD4+ T-cells. Upon initial infection, there are acute symptoms which are typically flu-like. When the immune system begins producing antibodies against HIV, the patient is said to have seroconverted. Seroconversion happens weeks after initial infection.
Symptoms become progressively worse if the patient progresses to AIDS. The official definition of AIDS is when they have a CD4+ T-cell count below 200/ml (normal counts are 500-1500). AIDS is typified by rare infections such as Pneumocystic (fungal) pneumonias, pneumonia due to cytomegalovirus, toxoplasmosis, herpes simplex, or gastrointestinal protozoa. Some patients may develop a rare form of cancer of the lymph nodes or blood vessels called Kaposi’s sarcoma. The cancer is caused by Kaposi sarcoma herpesvirus (KSHV) that inserts its genes into the host DNA, interrupting their cell division control mechanisms. Kaposi’s sarcoma is 20,000 times more common in AIDS patients than in the general public.
ART/ARV
Antiretroviral therapy (ARV/ART) are one of the greatest medical breakthroughs of the last 50 years. They have turned HIV from a death sentence to being a manageable chronic disease.
The first ARV treatments became available in 1995 and 1996, a mere 14 years after the first HIV cases became known. They work by interrupting the virus’ life cycle in multiple ways. In fact, they are classified by what step in the virus reproduction cycle they inhibit.
They do not fully cure the disease, they only keep the viral load down. Each pill consists of at least 3 antiretroviral drugs.
Each type of ARV has its own various side-effects. Some are long-term, some short term. Resistance is becoming an issue in many locations, but is helped by using combination therapies.
Superinfection
People on ARV can still become infected with a new strain of HIV in addition to what they already have, which is called superinfection. Patients need to be carefully educated and monitored for this potential outcome, especially if they are very sexually active.
Vertical transmission
Transmission from mother to child is generally referred to as vertical transmission. The risk of vertical transmission increases with superinfection. Whether a child is infected during birth depends on fluid exposures. A woman can have twins, and have one child infected and one not.
There are about 13 million young women currently living with HIV, and 2.9 million children with HIV (1/3 die in infancy). Transmission can occur in utero, during delivery, or through breastfeeding. Breastfeeding is the most common type of transmission from mother to child.
Basic history of HIV, including spillover event and how human networks were involved
HIV is an emergent, zoonotic disease that originated in non-human primates as Simian Immunodeficiency Virus (SIV). SIV is commonly found among groups that eat non-human primates, and it is thought that there have been multiple spillover events from primates to humans. Samples suggest crossover from primates to humans occurred sometime between 1884 and 1924 somewhere near Kinshasha (Congo). African colonization history is responsible for much of the rest of HIV’s spread. Before 1910, there were no cities in West Africa with more than 10,000 people. However, later in the 20th century the population experienced tremendous growth and urbanization, including increases in transportation and the sex trade. By 1960, there were about 2,000 people infected in Africa. HIV was carried to East Africa in the 1970’s. East Africa was much more urbanized. Women had low social status, and the sex trade was prevalent. There was also a great deal of labor immigration. All of this combined to cause a more widespread epidemic. By the 1980’s, HIV reached sub-Saharan Africa. It probably reached the Americas first in Haiti around 1972. The first two cases in the US were reported in the MMWR in 1981. The reports included rare cases of Pneumocystis pneumonia among homosexual men.
How HIV is spread
HIV can spread via blood or blood products, needles, semen, rectal or vaginal fluids, or breast milk. The virus preferentially infects CD4+ T-cells. Upon initial infection, there are acute symptoms which are typically flu-like.
When HIV becomes AIDS
The official definition of AIDS is when they have a CD4+ T-cell count below 200/ml (normal counts are 500-1500).
Symptoms of AIDS
AIDS is typified by rare infections such as Pneumocystic (fungal) pneumonias, pneumonia due to cytomegalovirus, toxoplasmosis, herpes simplex, or gastrointestinal protozoa. Some patients may develop a rare form of cancer of the lymph nodes or blood vessels called Kaposi’s sarcoma. The cancer is caused by Kaposi sarcoma herpesvirus (KSHV) that inserts its genes into the host DNA, interrupting their cell division control mechanisms. Kaposi’s sarcoma is 20,000 times more common in AIDS patients than in the general public.
How ART/ARV works, and how the drugs are classified
They do not fully cure the disease, they only keep the viral load down. Each pill consists of at least 3 antiretroviral drugs.
Each type of ARV has its own various side-effects. Some are long-term, some short term. Resistance is becoming an issue in many locations, but is helped by using combination therapies.
Who is most at risk of HIV infection and why
Men who have sex with men (MSM) make up only 4% of the US population, but account for 78% of all new cases. Their rate is 44 times higher than for other men. This is largely due to the increased risk of blood exchange during anal sex (as compared to vaginal sex).
African Americans, Asian Americans, and Pacific Islanders also experience higher rates of HIV in the US than other groups. This largely is due to social stigma associated with homosexual behavior in these groups, or is due to low socioeconomic status and poor health care access.
How maternal transmission of HIV to a child can be prevented
The Pediatric AIDS Clinical Trials Group (PACTG) 076 AZT regimen is a series of ARV drugs given in different amounts during pregnancy, delivery and just after birth to prevent transmission of HIV to a child. It was designed by a collaboration of researchers across the country, and is highly effective.
How HIV is different in children than in adults
HIV presents differently in children than with adults. Children more commonly develop recurring opportunistic bacterial or viral infections, but are less likely to get cancers (Kaposi’s sarcoma). Children develop interstitial lung disease whereas infected adults rarely do, and the disease generally progresses more rapidly in them than in adults.
General HIV prevention methods
Potential methods of prevention include distribution of condoms, education, using ARV treatment prophylactically (reduces transmission by 60-80%), needle exchange programs, and male circumcision. (more on these methods in class). Testing for HIV is imperative. However, about 20% of HIV+ persons in the United States are unaware of their infection.
