HIV infections and Aids Flashcards
What does AIDS stand for?
Acquired Immunodeficiency syndrome
What is AIDS?
- An anthroponotic disease
- last stage of infection with Human immunodeficiency virus /HIV/
- presented by severe and irreversible immune deficiency leading to opportunistic infections and/or neoplasma occurrence
What family is the HIV virus from?
subfamily Lentiviridae, family Retroviridae
What are the two types of known HIV viruses?
Two types of HIV viruses are known, causing similar signs and symptoms:
HIV1 – distributed all over the world
HIV2 – endemic for West Africa
Low resistance of the virus in the environment
What is an anthroponotic disease?
Anthroponoses (Greek “anthrópos” = man, “nosos” = disease) are diseases transmissible from human to human. Examples include rubella, smallpox, diphtheria, gonorrhea, ringworm (Trichophyton rubrum), and trichomoniasis. Zoonoses (Greek “zoon” = animal) are diseases transmissible from living animals to humans
What is the source of infection of HIV?
Source of infection: infected person or carriers – 10-100 days after infection to the end of their life
What does the risk of infection depend on for HIV?
The risk for infection depends on the viral load in the source
Highest concentration of the virus in semen, vaginal secretions, blood, and CSF /just in those with neurological involvement/
What are the modes of transmission for HIV?
- Sexual contact
- Blood route
- Vertical transmission
How is HIV contracted by sexual contact?
More than 70% of the cases
Homosexual or heterosexual contact without protection by condoms
Easier way for infection of women after contact with infected men than the opposite
How is HIV transmitted through the blood route?
About 15% of cases
Realized by: blood transfusion, medical manipulations using contaminated tools, iv drug users, tattoo, shaving by contaminated razor, work with HIV infected /0,03%/
How is HIV transmitted vertically?
From infected mother to child
Low risk – 15-20%
Risk period: at the time of delivery
Infections of the child by breastfeeding in 30-50%
Where is AIDS most prominent?
About 42 million people are infected by HIV worldwide /1% of the global adult population aged 15-49 years/
Majority of infections remain in sub-Saharan Africa, where 5.2% of the population is thought to be infected
What is the prognosis for untreated HIV infection?
The prognosis in patients with untreated HIV infection is poor, with an overall mortality rate of more than 90% for an average period varying between 8-10 years after infection
Which are the target cells for HIV?
Cells, which express on their surface CD4 receptor:
Immune cells: 60% of T-lymphocytes /CD4 lymphocytes or so called T-helpers mainly/, monocytes, macrophages
Cells of the nervous system: astrocytes, glyocytes, dendritic cells
Organ cells: kidneys, hepatocytes, enterocytes, cardiocytes, Langerhans cells in the skin
What is the pathogenesis of HIV?
- Adherence between viral protein gp120 and different cells, which express CD4
- Penetration of the virus in the target cells mediated by fusion between gp-41 and cell membrane
- Viral replication in the target cells
- Integration of the provirus into the cells’ genome by integrases and replication together with cell’s DNA, producing new virions
- The new synthesized viruses are separated by proteases to new HIV viruses
- Death of the infected cells by lysis, syncytium formation, apoptosis
How does HIV cause immunosuppression?
Progressive death of CD4 leads to progression of immunosuppression and viral load increases again
/highest level at the end stage of the disease/=AIDS
development when patients are susceptible to opportunistic infections and malignancies
What is the mechanism of immunosuppression in HIV?
Damage and death of TCD4 mainly /referent range about 500/mm3
Depressed function of monocytes and macrophages – ineffective phagocytosis
TCD8 /T-suppressors/ - increased level in the beginning of the disease, leading to CD4:CD8<0,5. In the late stages – decreasing of CD8 number and CD4:CD8 becomes false normal but severe immunosuppression is presented at that time
B cells – production of anti HIV antibodies, which does not have protective functions, just important for the diagnosis
What are the different phases seen in AIDS?
- Early phase (acute retroviral syndrome, primary clinical complex)
- Asymptomatic phase (latent, chronic)
What is involved in the early phase?
3-6 weeks after infection
50-70% of patients – flu like symptoms: fever, weakness, muscle pain, sore throat, lymphadenopathy
/DD with inf. mononucleosis/, hepatomegaly, splenomegaly, rash, encephalopathy
WBC: leucocytosis, lymphocytosis,
High viral load with normal TCD4, positive p24 antigen, negative ELISA /’serological window’/
Infected person is contagious
Duration: 2-4 weeks and self-limiting course
At the end of this period - appearance of antibodies in the serum together with decreasing of viral load to the set point
What is involved in the asymptomatic/ latent/ chronic phase?
Duration: 7-16 years and it depends on:
Co-occurrence of another sexual-transmitted diseases
Pregnancy
Co-infection with EBV/HHV6
Iv drug users
Smokers/chronic alcocholism
HLA predilection:
B11, 27, 51, 57, 58 – slow progression
A23, B37 – fast progression
Lack of any symptoms
Progressive: decreasing of TCD4 count <500/mm3 and increasing of viral load
Patients are seropositive
What is the clinical presentation of AIDS?
At the end of second stage
First indicators: persistent enlarged lymph nodes
Low-grade fever
Sweating
Chronic diarrhea
Oropharyngeal candidiasis (thrush)
Vulvovaginal candidiasis, persistent or resistant
Hairy leukoplakia
Herpes zoster (shingles), involving two or more episodes or at least one dermatome
Peripheral neuropathy, Aseptic meningitis
Kaposi’s sarcoma
Ca coli uteri
