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3.Laboratory examination

HIV/AIDS Laboratory examination methods include HIV antibody examination, viral load examination, CD4+T lymphocyte examination and p24 antigen examination. The HIV1/2 antibody examination is the gold criterion, and the viral load measurement and CD4+T lymphocyte count are the important indices to judge the progression, clinical administration of drugs, curative effect and prognosis of the disease. For babies under 18 months, HIV infection diagnosis can be conducted by nucleic acid examination with two positive results as reference for diagnosis, and can be confirmed by antibody examination after 18 month old.
3.1 HIV1/2 antibody examination: inclusive of screening tests (containing primary screening and reexamination) and confirmatory tests
HIV1/2 antibody screening tests include ELLSA test and rapid test (rapid test-paper test and gelatin particle agglutination test) etc. The ELLSA is the commonly used screening method, but should be conducted with VCT. Rapid test can also be adopted. HIV antibody is often validated by immune Western Blot (WB) test.If the screening result is HIV-negative, a HIV1/2 antibody negative report can be given,. If the result is positive, positive report cant be offered, but a HIV antibody to be re-examined report instead.
If the HIV-1 (or HIV-2) positive is validated through reexamination, a HIV-1(or HIV-2) antibody positive confirmation report can be given, but should be kept secret, and meanwhile counseling and report work should be done
3.2Viral load measurement
Viral load is usually expressed by copy number of HIV RNA each milliliter in blood plasma (c/ml). The viral load is often measured with RT-PCB, NASBA NucliSens and bDNA. The test methods for different viral loads are compared in Table 1.







Standard: (1.5 edition)

bDNA. 3.0 edition

Nuclisens HIV-1 QT:





Extra-sensitive: (1.5 edition)


Depending on Specimen quantity




Subtypes added

1.0 edition: only B subtype available



1.5 edition: B-G

Sample quantity








EDTA or heparin


Blood plasma

Blood plasma, PBMC, semen, tissue, etc

Whole blood, blood plasma, PBMC, semen, tissue, etc

Measurement sample required

The blood plasma is separated within 6 hours? and frozen at -20 or -70 before transportation

The blood plasma is separated within 4 hours? and frozen at -20 or -70 before transportation

The blood serum or blood plasma is separated within 4 hours and frozen at -20 or -70 before transportation

The basis of viral treatment, the evaluation of treatment efficacy and the adjustment of regimen can be considered as reference indic
3.3CD4+ T cell examination CD4+ T cell is the major target cell of HIV infections. After HIV has infected the human body, the CD4+ T cells will be progressively reduced, a CD4+/DE8+ cell proportion inversion phenomenon will appear and cell immune function will be damaged. If it is treated with HAART, THE CD4+ T cells might increase in different degrees at different stages.
The CD4+ lymphocyte sub-group measurement commonly used at present is a fluid cell technology, with which, the absolute number of CD4+ T cells can be acquired directly or converted from the white cells after counting and classification. If fluid cell instrument is not available to measure the CD4+ T cells, the absolute number of lymphocytes can used as a reference.
The absolute number of CD4+ T cells has a clinical significance in understanding the immune state of the organism and the course of disease, identifying the stage of disease and the initiation of treatment, judging the effect of treatment and the clinical complication of a person infected with HIV.
The interval of CD4+ T cell count measurement can be decided by clinical doctor in accordance with the actual situation of patients. Generally speaking, the infected persons without symptoms should be examined once a year, the HIV/AIDS patients with CD4+ T cell count between 200-350/mm3 and having not initiated AVT should be examined once half a year, and those who have already received ART treatment should be examined once each 3 months in the first year, and once half a year after treatment over a year and state of illness being stable. es for the early diagnosis of HIV infections.

4.Onset mechanism

4.1 Viral infection course
4.1.1 Primary infection
To enter the cells in human body, HIV needs to rely on the acceptors on the surface of susceptible cells, including the first acceptor and the second acceptor. The outer-membrane glucoprotein gp120 of HIV-1 first combines with the first acceptor, and then with the second acceptor, and changes its conformation and separate from gp41, finally leading to its combination with host cell and entering the cell.
Within 24-48 hours after entering the human body, the HIV can reach local lymph nodes, and about 5 days afterward, viral components can be detected in the spherical blood. Then viral blood symptoms will appear, and lead to acute infection.
4.1.2 HIV infection course in the cell of human body
Adsorption and penetration: after infecting human body, HIV-1 selectively adsorbs on the CD4 acceptor of target cells and then enters the host cells assisted by auxiliary acceptors.
Cyclization and integration: virus RNA, by the action of reverse tramscriptase, forms a cDNA, by the action of polymerase, forms a non-covalent combined double stranded DNA, and by the action of integrase, the newly formed double stranded DNA integrates into the host cell chromosome DNA. The integrated viral double stranded DNA is just a provirus.
Transcription and translation: the provirus is activated and transcribed to form a viral RNA. Some RNA, after added with a cap and a tail, become offspring gene group RNA, and others, after slicing, become mRNA, and are transcribed and translated into viral structural protein and non-structural protein on the nucleolus protein. The synthetic viral protein is saccharified and processed on the endoplasmic reticulum ribosome, and, under the action of proteinase, is cracked and forms the protein and enzyme of the offspring viruses.
Assembly, mature and budding: Gaq protein and viral RNA combine to assemble a capsid, and through budding from cytoplasmic membrane, acquire a viral membrane, and become a matured viral particle.
4.1.3 Three clinical outcomes after HIV infection
The failure of immune system to remove the viruses will lead to chronic infection with three clinical outcomes, manifested in typical progression, rapid progression and long-time non-progression. The major factors that influence the clinical outcomes of HIV infection are viruses, host immunity and genetic background, etc.

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