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Overview
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Human immunodeficiency virus (HIV) targets the immune system, and if untreated, causes acquired immune deficiency syndrome (AIDS). Around the world, 38 million individuals are currently living with HIV. Of those, 1.7 million people were newly infected in 2019 and 690,000 have died of AIDS-related illnesses.1 Two main types of HIV exist—HIV-1 and HIV-2. They are very similar structurally and both ultimately lead to AIDS. Globally, HIV-1 is more widespread while HIV-2 is restricted to Western and Central Africa. HIV-2 is less virulent with a longer progression into AIDS but induces diseases of the central nervous system more frequently.

 

 

What are the stages of HIV infection?

Assuming no treatment is taken, there are three stages in the progression of HIV infection:2

 

  • Acute — usually occurs about 3 weeks post-exposure. During this phase, the virus replicates rapidly in CD4 T-cells, which is indicated by high viral load and high rate of CD4 T-cell destruction. This is when the host is the most infectious.
  • Chronic — also known as clinical latency or asymptomatic HIV infection, the chronic phase is the second stage of infection. Viral replication is low and without treatment, those infected will progress to AIDS within 10+ years.
  • AIDS — at this point, the virus has tremendously damaged the immune system and the host can no longer fight opportunistic infections.

Definition of advanced HIV disease

The World Health Organization (WHO) defines four clinical stages of HIV disease—stage 1 through 4, based on the severity of symptoms and coinfections and progression to AIDS.

 

For adults, adolescents and children older than five years, advanced HIV disease is defined as having a CD4 T-cell count <200 cells/mm3 or WHO stage 3 or 4 event. All children younger than 5 years old with HIV are considered as having advanced HIV disease.3

How is HIV diagnosed?

Antibody tests are the most widely used diagnostic tests to detect HIV infection. It can take about 28 days post-exposure (window period) for HIV-specific antibodies to be detected. Nucleic acid tests (NAT) help determine the viral load in patients. The 2015 World Health Organization (WHO) “Clinical Guidelines: HIV Diagnosis” provides diagnostic test recommendations for different patient groups.4

Biology of HIV infection

HIV is a retrovirus with a genome of 9.8 kilobases coding for a very small number of proteins and with a high mutation rate. The lipid envelope surrounding the core is derived from host cells and is studded with glycoproteins, which are of paramount importance during infection and for eliciting immunogenicity. The envelope protein gp120 binds to CD4 to fuse with T-cells and macrophages. Upon entry into the host cell, the viral RNA is reverse transcribed to DNA, which then integrates into the host genome and gets replicated using the hijacked host machinery. This results in the activation of immune responses instantly, resulting ultimately in depletion of the CD4+ T-cell population through various mechanisms.5

HIV-mediated CD4+ T-cell depletion

HIV-mediated CD4+ T-cell depletion is believed to occur through several stages—(i) enhanced T-cell production upon infection, (ii) accelerated destruction of T-cells through immune responses, (iii) accelerated T-cell production as a response to T-cell depletion through cytokine signaling in the lymph nodes, (iv) accelerated viral replication resulting in the destruction of progenitor cells in the bone marrow, thymus and peripheral lymphoid systems.

 

Interested in preparing for the IVDR? Visit our IVDR page to learn more about the measures you can take to prepare your lab.

HIV Monitoring
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BD FACS™ Loader, BD Multitest™ and BD Tritest™ products as intended on this page, BD Trucount™ Tubes, BD FACSPresto™ Near-Patient CD4 Counter, BD FACSPresto™ Cartridge, BD FACSCanto™ II Flow Cytometer and BD FACSLyric™ Flow Cytometer with the BD FACSuite™ Clinical and BD FACSuite™ applications are in vitro diagnostic medical devices bearing a CE mark.

BD Flow Cytometers are Class 1 Laser Products.  

BD FACSPresto™ Near-Patient CD4 Counter System is for point of care use.

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