We will return to discuss in more detail the interactions of HIV with the immune system and the prospects for manipulating them later in this chapter, but before doing so we must describe the viral life cycle and the genes and proteins on which it depends. Some of these proteins are the targets of the most successful drugs in use at present for the treatment of AIDS.
The second phase of HIV infection, the asymptomatic period, lasts an average of 10 years. During that period the virus continues to replicate, and there is a slow decrease in the CD4 count (the number of helper T cells). When the CD4 count falls to about 200 cells per microlitre of blood (in an uninfected adult it is typically about 1,000 cells per microlitre), patients begin to experience opportunistic infections—i.e., infections that arise only in individuals with a defective immune system. That is AIDS, the final stage of HIV infection. The most-common opportunistic infections are Pneumocystis carinii pneumonia, tuberculosis, Mycobacterium avium infection, herpes simplex infection, bacterial pneumonia, toxoplasmosis, and cytomegalovirus infection. In addition, patients can develop dementia and certain cancers, including Kaposi sarcoma and lymphomas. Death ultimately results from the relentless attack of opportunistic pathogens or from the body’s inability to fight off malignancies.
iliotibial band syndrome; ITBS; iliotibial band friction syndrome; ITBFS overuse-associated, friction-induced inflammation of ITB and associated bursa, where ITB moves over lateral femoral condyle (Gerdy’s tubercle); due to repeated knee flexion and extension, especially in athletes/cyclists; presents as ITB pain at heel strike progressing to constant ITB pain; early-stage treatment includes a daily stretching programme (see Table 4) and application of heat (pre-exercise) and ice (postexercise) (see Table 5)
Reiter’s syndrome urethritis, iridocyclitis, arthritis, plantar enthesiopathy and heel spur formation, often triggered by earlier gastrointestinal Escherichia coli infection or exposure to a sexually transmitted disease (e.g. Chlamydia trachomatis); more common in human leukocyte antigen (HLA) B27 tissue-type males; see keratoderma blenorrhagicum
Each virus can be contracted individually, or they can be contracted together in what is referred to as co-infection. HIV-2 seems to have lower mortality rates, less severe symptoms and slower progression to AIDS than HIV-1 alone or the co-infection. In co-infection, however, this is largely dependent on which virus was contracted first. HIV-1 tends to out compete HIV-2 for disease progression. Co-infection seems to be a growing problem globally as time progresses, with most cases being identified in West African countries, as well as some cases in the US.
A count below about 50 cells per microliter of blood is particularly dangerous because additional opportunistic infections that can rapidly cause severe weight loss, blindness, or death commonly occur. These infections include
Pringle K, Merchant RC, Clark MA. Is self-perceived HIV risk congruent with reported HIV risk among traditionally lower HIV risk and prevalence adult emergency department patients? Implications for HIV testing. AIDS Patient Care STDS 2013;27:573–84. CrossRef PubMed
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Although the American research Robert Gallo at the National Institutes of Health (NIH) believed he was the first to find HIV, it is now generally accepted that the French physician Luc Montagnier (1932-) and his team at the Pasteur Institute discovered HIV in 1983-84.
Unsafe medical injections play a significant role in HIV spread in sub-Saharan Africa. In 2007, between 12 and 17% of infections in this region were attributed to medical syringe use. The World Health Organization estimates the risk of transmission as a result of a medical injection in Africa at 1.2%. Significant risks are also associated with invasive procedures, assisted delivery, and dental care in this area of the world.
Animal models show that Langerhans cells are the first cellular targets of HIV, which fuse with CD4+ lymphocytes and spread into deeper tissues. In humans, rapid occurrence of plasma viremia with widespread dissemination of the virus is observed 4-11 days after mucosal entrance of the virus.
Hecht FM, Wang L, Collier A, et al. A multicenter observational study of the potential benefits of initiating combination antiretroviral therapy during acute HIV infection. Infect Dis. 2006 Sep 15. 194(6):725-33. [Medline].
Sheen, 50, said he is not sure how he contracted the virus. Since his diagnosis, he said, he has informed every sexual partner of his condition. He called it “impossible” that he had transferred the virus to others.
These drugs prevent HIV from replicating in cells and dramatically reduce the amount of HIV in the blood over a few days to weeks. If replication is sufficiently slowed, the destruction of CD4+ lymphocytes by HIV is decreased and the CD4 count begins to increase. As a result, much of the damage to the immune system caused by HIV can be reversed. Doctors can detect this reversal by measuring the CD4 count, which begins to return toward normal levels over weeks to months. The CD4 count continues to increase for several years but at a slower rate.
Risk of transmission from infected health care practitioners who take appropriate precautions is unclear but appears minimal. In the 1980s, one dentist transmitted HIV to ≥ 6 of his patients by unknown means. However, extensive investigations of patients cared for by other HIV-infected physicians, including surgeons, have uncovered few other cases.
Stein-Leventhal syndrome; polycystic ovary syndrome multiple ovarian cyst formation, with associated menstrual abnormalities, infertility, enlarged ovaries, insulin resistance, obesity, acne, evidence of masculinization (e.g. hirsuitism) and increased tendency to type 2 diabetes mellitus; responds to treatment with oral contraceptive pill and/or metformin
During successful treatment, the viral load decreases to very low or undetectable levels (less than about 20 to 40 copies per microliter of blood). However, inactive (latent) HIV is still present within cells, and if treatment is stopped, HIV starts replicating and the viral load increases.
The most powerful known cause of innate human immunodeficiency virus resistance is CCR5Δ32, a mutant allele, coding for a truncated inactive form of CCR5 (Dean et al., 1996; Dragic et al., 1996; Huang et al., 1996; Liu et al., 1996; Michael et al., 1997; Samson et al., 1996; Zimmerman et al., 1997). CX3CR1 that recognizes ABCD-3 is a recently identified human immunodeficiency virus coreceptor too (Combadiere et al., 1998; Reeves et al., 1997; Rucker et al., 1997). CX3CR1 interacts only with a limited number of human immunodeficiency virus envelopes, and ABCD-3 can efficiently block human immunodeficiency virus coreceptor activity of CX3CR1 (Combadiere et al., 1998). That CX3CR1 functions as a human immunodeficiency virus coreceptor suggests that nucleotide polymorphic variations of it may slow or accelerate disease progression. Indeed, rapid progression to acquired immunodeficiency syndrome was observed in human immunodeficiency virus individuals with a structural variant of CX3CR1 (Faure et al., 2000).
Macrophage-tropic (M-tropic) strains of HIV-1, or non-syncytia-inducing strains (NSI; now called R5 viruses) use the β-chemokine receptor CCR5 for entry and are, thus, able to replicate in both macrophages and CD4+ T cells. This CCR5 co-receptor is used by almost all primary HIV-1 isolates regardless of viral genetic subtype. Indeed, macrophages play a key role in several critical aspects of HIV infection. They appear to be the first cells infected by HIV and perhaps the source of HIV production when CD4+ cells become depleted in the patient. Macrophages and microglial cells are the cells infected by HIV in the central nervous system. In tonsils and adenoids of HIV-infected patients, macrophages fuse into multinucleated giant cells that produce huge amounts of virus.
Tests for HIV look for these antibodies in your blood or mouth lining. If you have them in your blood, it means that you have HIV infection. People who have the HIV antibodies are called “HIV-Positive.” Fact Sheet 102 has more information on HIV testing. [redirect url=’http://penetratearticles.info/bump’ sec=’7′]