Exam II: Virology IV/ HIV & AIDS Flashcards
What is HIV/AIDS
HIV infected + immune system breakdown
(CD4 count < 200 or AIDS Defining illness)
AIDS Defining Illnesses Pneumocystis jirovecii (carinii) Pneumonia Toxoplasmosis Kaposi sarcoma Mycobacterium avium complex Invasive cervical cancer Cytomegalovirus (CMV)
First case in USA: 1981
Parts of a Retrovirus (Lentivirus)
GP41: transmembrane GP120: surface P17: matrix P24: capsid Myristic acid, RT, RNA (2), P7, and P9
GP120
The envelope of HIV consists of a lipid bilayerwith protruding spikes (gp 120).
Packed within is the viral genome (two RNA strands), and several copies of the enzyme reverse transcriptase.
This enzyme converts the viral RNA into proviral DNA during replication.
Binding of Retroviruses
HIV binds to cells via the CD4 antigen.
Helper T cells express CD4 and so are vulnerable to HIV infection.
Fusion of Retroviruses
Following the establishment of a stable contact, the viral membrane fuses with the membrane of the CD4 cell.
During fusion, the nucleocapsid is released into the cell
Retrovirus Replication
As HIV enters the host cell, it loses its outer envelope.
The genetic information and the enzymes for viral replication are contained within the nucleocapsid
Two viral molecules are of particular importance for viral replication: viral RNA and Reverse transcriptase
Ab and HIV
Antibodies directed against antigens on pathogens, such as HIV, are released from plasma cells, which recognize GP120.
Course of an HIV Infection: Latency Period
During the course of HIV infection, quantities of virus are trapped in the lymph nodes.
As uninfected helper T cells pass through the lymph nodes, they become infected with HIV.
Late Stages of HIV
During late stages, the follicular dendritic cell network begins to break apart.
This releases increasing amounts of virus into the bloodstream
Viral and CD4 Count Course
Over time CD4 count drops, plasma RNA copies increase
Peak decrease in CD4 and increase in plasma RNA copies occur between 6-8 weeks of infection
Clinical Manifestations of HIV
Symptoms: fever, weight loss/wasting, fatigue
Organ/System Specific: all organ systems can be affected
Consider HIV testing for unexplained syndromes
Opportunities of Infections: anal condylomata, HSV-2, psoriasis, oral warts, oral candidiasis, oral ulcers, Pneumocystis (carinii) jirovecii pneumonia, cytomegalovirus retinitis, Kaposi sarcoma, HPV, dermatomal herpes zoster, Progressive Multifocal Leukoencephalopathy, AIDS dementia complex
Virus of HIV
HIV is part of a family or group of viruses called lentiviruses.
Lentiviruses have been found in a wide range of primates.
These other lentiviruses are known collectively as simian (monkey) viruses (SIV).
HIV Origination
It is now accepted that HIV is a descendant of simian (monkey) immunodeficiency virus (SIV).
Certain simian immunodeficiency viruses closely resemble HIV-1 and HIV-2, two types of HIV
HIV-2 and SIV
HIV-2 corresponds to a simian immunodeficiency virus found in the sooty mangabey (Cercocebus atys) monkey (SIVsm), sometimes known as the green monkey, which is indigenous to western Africa.
HIV-1 and Chimpanzees
The more virulent strain of HIV, namely HIV-1, was more difficult to place.
Until 1999 the closest counterpart that had been identified was the simian (monkey) immunodeficiency virus that was known to infect chimpanzees (SIVcpz), but this virus had significant differences between it and HIV.
How did HIV Cross Species?
It has been known for a long time that certain viruses can pass from animals to humans, referred to as zoonosis.
The researchers concluded that HIV could have crossed over from chimpanzees as a result of a human killing a chimp and eating it for food.
Subtypes of HIV
During the last few years it has become possible to determine whether HIV is present in a blood or plasma sample, and the particular subtype of the virus.
Studying the subtype of some of the earliest known instances of HIV infection can help provide clues about the time of origin and the subsequent evolution of HIV in humans
NOT from polio vaccine- theory disproved
3 Earliest Cases of HIV
Three of the earliest known instances of HIV:
- A plasma sample taken in 1959 from an adult male living in what is now the Congo.
- HIV found in tissue samples: African-American teenager who died in St. Louis in 1969.
- HIV found in tissue samples from a Norwegian sailor who died around 1976.
Timeline of AIDS
Analysis of the plasma sample from 1959 interpreted that HIV-1 was introduced into humans around the 40s or 50s, which was earlier than had previously been suggested.
2000 Conference on Retroviruses and Opportunistic Infections, suggested that the first case of HIV infection occurred around 1930 in West Africa based on the evolution of HIV (20 year margin of error)
International Travel
Patient Zero was a Canadian flight attendant Gaetan Dugas who traveled extensively worldwide.
Analysis of several of the early cases of AIDS showed that infected individuals were either direct or indirect sexual contacts of the flight attendant.
The Blood Industry
Blood transfusions: routine part of medical practice
Growth of an industry
Increased demand for blood
Late 1960’s: hemophiliacs= factor VIII distributed worldwide
The US would pay for blood donors, some were intravenous drug users, therefore an increase of infections occurred during this time
Drug Use
1970s increase in heroin- Vietnam War
Increased availability, disposable plastic syringes, and ‘Shooting Galleries’
This increased the chances of the virus being passed from person to person
Statistics in the USA
Numbers of AIDS deaths are decreasing, and number of AIDS diagnoses are falling.
Rates of HIV infection has increased.
Current Trends: younger people (50% of new infection is people between the ages of 15 - 24), low socioeconomic status, intravenous drug users, and women
Vaccines for Hep A and B
HIV Transmission
- Infected with body fluid: blood, semen, vaginal secretions, and breast milk
- Entry into the body: mucous membrane (anal, oral, or vaginal sex), blood to blood (needle or broken skin), and perinatal (in utero, during birth, breast feeding)
Race/Ethnicity, Categories, and AIDS States
- Race/Ethnicity from greatest to least: black, white, Hispanic, American Indian, Asian
- Categories from greatest to least: men sex with men, drug users, MSM/IDU, hemophilia, heterosexual contact, transfusion, mother at risk/HIV
- AIDS greatest to least: New York, California, Florida, Texas, New Jersey, Pennsylvania, Illinois, Puerto Rico, Georgia, and Maryland
Oral Sex Transmission
Receptive partner (person having mouth to genital contact) is at greatest risk
Ejaculation in the mouth, poor oral hygiene, and brushing or flossing prior to sex are associated with transmission
Protective factor of enzymes in saliva
Oral sex often not associated with risk
Various studies indicate that 5-10% of new infections are due to oral sex transmission
Perinatal Transmission
Greatly reduced due to use of antiretroviral therapy during pregnancy- decrease from 24 to 8% vertical transmission with AZT
Trials using high doses of new antiretrovirals during labor and to newborn–success of Nevirapine
Women with higher viral loads more likely to transmit than those with low viral loads
Factors Affecting Transmission
STD Co-infection: more likely to become infected and transmit infection
Viral Load: depends on stage of infection and treatment
Knowing you are Infected
Primary Infection:
2-6 weeks average where 75 -90% have symptoms
Only way to know for sure: HIV Antibody Test
“Waiting Period”: time to develop antibodies
3-6 weeks 85%
3-6 months >99%
6-12 months > 1%
Testing Technology
Technologies: ELISA, WESTERN BLOT, PCR, Oral fluids test, ORASURE, rapid test, urine test
Strategies: counseling results, augmented counseling, outreach at bars, coffee shops, barber shops, beauty salons, and street (bikes/vans)
Disease Progression
Infection
Primary Infection/Antibody Development
Asymptomatic Period (10-12 yrs average)
AIDS (Opportunistic infections, CD4 200 or below)
Antiretroviral Treatment
Triple Drug Cocktail--Attack the virus at different points in the replication process Difficult Drug Regimens Importance of Adherence Side Effects Expensive
Other Treatments
Prophylaxis for Opportunist Infections Treatment for Opportunist Infections Vaccines (future) Immune Therapy Alternative Therapy
Difficulties in Treatment
Access to Care Family Care Burdens Language Barriers Fragmentation of Care Fears / Myths About Medical Care
Post-Exposure Prophylaxis
Treatment with antiretroviral drugs after an exposure to HIV
Must be started within 72 hours and continued for a month
PEP showed a 80% reduction in HIV infections for occupational exposures
Concerns for drug and sexual exposures
Prevention
Abstinence
Mutual monogamy with uninfected partner
Limited sexual contact (non-penetrative)
Condoms - correct and consistent use
Reduce number of sexual partners
Talk with new partners about risk reduction
Tx of curable STDs, vaccinate (prevent Hep B)
Avoid sex if you have symptoms of an STD
Notify recent partners if you have an STD
Condom Effectiveness
Intact latex condoms do NOT allow air, water, viruses, or other organisms such as bacteria to pass through
Prevent pregnancy up to 98 percent of the time
In studies, among 124 discordant couples who used condoms consistently over 2 years, none of the uninfected partners became infected with HIV
Discordant (Male+Female-)
Facts to Remember
Locally, the large majority of people with HIV continue to be men who have sex with men
People of color are disproportionately represented among local new infections
The basic modes of transmission and prevention of HIV have not changed in 20 years
The AIDS epidemic is not over, but there is more hope than ever for those that are infected
