How HIV is tested, Diagnosis, Prevention, Treatment

HIV Tested and Diagnosis

HIV caused acquired immunodeficiency syndrome (AIDS). HIV is an RNA virus that belongs to family retroviridae. The most important retrovirus, human immunodeficiency virus HIV-1, and HIV-2 belong to the genus lentivirus. HIV can be detected by PCR and ELISA. HIV core is surrounded by a nucleocapsid and composed of a protein coat.

HIV caused diseases

  • Acquired immunodeficiency syndrome(AIDS).

Opportunistic Infection associated with HIV infection

  • Mycobacterial infections
  • Salmonellosis
  • Varicella-zoster
  • Epstein Barr virus
  • Candidiasis
  • Pneumocytosis
  • Cryptococcosis
  • Aspergillosis
  • Toxoplasmosis

Antigen Variation

  • HIV undergoes a frequent antigenic variation of core and envelope antigens.
  • Two antigenic types of HIV have been – HIV-1 and HIV-2.
  • Antigen variation occurs within both HIV – 2 and HIV -2.
  • HIV-1 represents the original isolation from America, Europe, and other western countries, whereas HIV-2 represents isolates from West Africa.
  • HIV-1 strains have been classified into two ten subtypes, A to J.
  • Subtypes C is the most prevalent in India and China.

Cell Tropism

  • HIV infects the cells expressing at their surface the CD4 antigen, which is the receptor for the virus.
  • The infected CD4 expresses a high level of GP 120 on the surface of infected cells leading to the fusion of these cells with CD4 protein of uninfected neighboring cells. The lysis of intertwined cells, at last, happens to bring about the consumption of countless uninfected cells from the flow.

Diagnosis Of Human Immunodeficiency Virus(HIV)

Diagnosis of human immunodeficiency virus infection includes specific tests for human immunodeficiency virus and tests for immunodeficiency.

Specific Tests for HIV Infections

  1.  Antigen detection: p24 antigen
  2. Virus isolation
  3. Detection of virus nucleic acid
  4. Antibody detection

Non-Specific Tests for HIV infection

  1. Total and different leucocyte count
  2. T- lymphocyte subset assy
  3. IgG and IgM level
  4. Skin Test

Antigen Detection for HIV infections

  • The p24 antigen in the earliest virus marker to appear in the blood.
  • The p24 antigen capture assay ELISA can be the detection of the antigen.

Virus Isolation for HIV infection

  • For diagnosis, the virus is not routinely isolated.
  • The patient’s lymphocytes are co-cultivated with uninfected human lymphocyte in the presence of interleukin-2. Viral replication can be detected by a demonstration of reverse transcriptase activity and presence of viral infection

Detection of Viral Nucleic Acid

  • Viral nucleic corrosive can be distinguished by polymerase chain reaction(PCR).
  • It is also useful for diagnosis in the window period.

Antibody detection for HIV infection

  • Exhibition of antibodies is the least complex and most normally utilized system for the conclusion.
  • It might take half a month to months for antibodies to show up after disease.
  • HIV infection when remains negative for antibodies during the window period, when initial viral replication takes 2-3 weeks.
  • The diagnosis of HIV infection made by detecting serum antibody to viral protein both core or envelope.

Screening test for HIV

  1. ELISA Test

  • It is a profoundly touchy and explicit test.
  • It is an extremely good screening test and most laboratories use a commercial ELISA kit that contains both HIV-1 and HIV-2.
  • Saliva is an acceptable alternative to serum for antibody testing by ELISA. 

     2. Rapid Tests

  • These tests take under 30 minutes and don’t require costly hardware.

    3. Simple Test

  • They take 1-2 hours and don’t require costly hardware.

Western Blot Test

  • In this test, HIV proteins are separated by polyacrylamide gel electrophoresis.
  • The isolated proteins are smeared on to portions of nitrocellulose paper.
  • These strips are reacted with test sera.
  • Antibodies of HIV proteins, if present in test serum, combined with fragments of HIV.
  • The strips are washed and reacted with enzyme-conjugated anti-human globulin.
  • A suitable substrate is the added which produces color bands.
  • The position of the color band on the strip indicates the fragments of antigens.
  • A positive response with proteins speaking to the three qualities stifler, pol, and env is decisive proof of HIV response.
  • The test is also considered positive if it shows bands against at least two of the following proteins: p24, GP 41, and GP 60/120.
  • A positive in any one screening test may not be accepted without confirmation.
  • It was the practice to use the western blot test for the confirmation.
  • The practice is now to perform either two different types of ELISA or an ELISA with different any of the rapid tests. A serum positive in the two tests is viewed as positive.

Strategies For HIV Testing

Strategy 1: 

The serum is subjected once to E/R/S test and if positive, the sample is taken as HIV infected and if negative, the serum is considered to be free of HIV. The strategy is used for ensuring donation safety. For this reason, an exceptionally touchy and entirely dependable test unit must be utilized.

Strategy 2A:

A serum sample is considered negative if the first E/R/S test reports it so, but if positive, it is retested with a second E/R/S test based on a different antigen preparation and different test principle. If found positive in the second E/R/S test also, it is reported as positive, otherwise as negative. This technique is utilized for HIV reconnaissance.

Strategy 2B:

The serum sample is processed as in strategy 2A, but a sample positive with the first E/R/S test and negative with the second test is subjected to the third E/R/S test. If the third test is positive, the sample is considered equivocal, such a person should be retested after 2-4 weeks.
 If the third test is negative, it is reported negatively. Two or three different E/R/S test based on the different test principle is used. If the first to three different E/R/S  based on a different antigen preparation and different test principle is used.
If the first two tests are positive, a positive report can be given to the patient after post-test counseling. Strategy 2B is used to diagnose an individual with symptoms suggestive of aids clinically.

Strategy 3:

It is similar to strategy 2A, with the added confirmation by a third test E/R/S test. The third test ought to again be founded on various antigen arrangements or test standards. A serum testing positive on all three E/R/S tests is reported positive.
A serum specimen negative in thrid E/R/S is considered equivocal. Such persons should be retested after three weeks. If this specimen also proves an equivocal result, the individual considered to be negative for the HIV antibody. This strategy is used for the diagnosis of HIV infection in asymptomatic individuals.

Prevention Of HIV

  • The use of condoms can prevent transmission or virus through sexual routes.
  • Contaminated syringes or needles should not be shared.
  • All blood and blood products are to be screened for HIV.
  • No effective vaccine has yet been found out.

Treatment Of HIV

  • Specific treatment with antiretroviral drugs is the mainstay in the management of HIV infection.
  • Highly active antiretroviral therapy(HAART) is effective in the inhibition of HIV replication in most HIV- infected individuals.
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