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.
