7 topics with concise reviews: definitions, key facts, and class questions.
Retroviruses are a unique family of RNA-containing viruses capable of synthesizing DNA from an RNA template using reverse transcriptase. The primary representative, which revolutionized modern infectiology and immunology, is the human immunodeficiency virus (HIV).
In this section, we will systematically examine retrovirus biology, epidemiology, and the insidious pathogenesis of HIV infection. You will study the clinical course of the disease from the acute phase to the AIDS stage, modern methods of microbiological diagnosis, as well as the principles of antiretroviral therapy and prevention.
Frequently asked questions in class: Instructors expect a clear understanding of the HIV virion structure, the functions of its enzymes (reverse transcriptase, integrase, protease), and the mechanism of CD4+ T-lymphocyte destruction. Pay special attention to the laboratory diagnostic algorithm: you must know when screening is ordered (ELISA/CLIA), how the confirmatory test works (immunoblotting), and what PCR (viral load) is used for. Focus maximum attention on these topics.
They are reverse-transcribing viruses. The presence of the reverse transcriptase enzyme allows them to synthesize DNA from a viral RNA template for subsequent integration into the genome.
Why is it difficult for the immune system to cope with HIV?
This is due to the hypervariability of the env gene region. In each new cycle of viral reproduction, altered variants of the gp120 surface protein are formed, which previously generated antibodies can no longer recognize.
Why does the number of people living with HIV continue to grow in developed countries?
The increase in the number of infected individuals in developed countries is associated not only with the emergence of new infections, but also with the widespread use of antiretroviral therapy, which prolongs patients' lives, thereby increasing the overall pool of carriers.
Why can antibodies not completely neutralize HIV?
The virus spreads from reservoir cells (macrophages, dendritic cells) via direct intercellular fusion. This mechanism allows it to transmit from cell to cell while avoiding release into the bloodstream and contact with neutralizing antibodies.
Why don't antibodies protect against disease progression in HIV infection?
The virus constantly mutates in the body, creating new structural variants called «quasispecies». Because of this, the antibodies produced have low neutralizing activity and are unable to provide protective immunity.
Why is PCR not used at the screening stage?
PCR is not used for primary diagnosis due to the high genetic variability of the virus. Mutations can alter the target regions of the genome, making the virus invisible to standard test systems at the initial stage.
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