What is HIV? How does it gets transmitted?

What is a Virus

       A virus is small infectious micro-organism which have the ability to replicate inside the cells of other living organisms. They can grow and multiply rapidly only in a host tissue. It is 100 times smaller than the bacteria.It contains Nucleic acid either DNA or RNA as the genetic material, an outer Protein Capsid. Examples are DNA virus are Pox virus, Herpes, Hepadna and Hepatitis virus etc., Examples are RNA virus are Influenza virus, Ebola virus, dengue virus etc., Virus,also known as Phage which infects and replicates inside a bacterium is known as bacteriophage.

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What is Retro-virus

     Retro-virus is a RNA virus, infects the host cell with its unique specialized enzyme called Reverse Transcriptase. It converts its RNA to DNA similar to host DNA. The formed retroviral DNA gets incorporated into the host DNA and gets multiplied along with the host DNA. Hence it is also called Immunodeficiency virus. Examples of Retro-virus are HIV virus, T-cell Leukemia etc., The structure consists of Inner Core with  RNA as genetic material, Ribonucleo protein, Outer protein coat called Capsid and enzymes like Reverse transcriptase, RiboNuclease, Integrase. Receptors composed of Glycoproteins 120 and 41 on the phospholipid bilayered envelope.
                                       
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Epidemiology

     South Africans were the largest population of the world affected with HIV. Globally, 36.7 million people have been affected  in 2016 and nearly 5.9 millions are from South Africa. There were nearly 1 million deaths have been observed globally in 2016. Among the HIV infected persons, half of the members were Men and remaining half were Women which can get easily transmitted highly through sexual intercourse. HIV has grown silently in India over the past decade.

Etiology/ Risk factors

  • Human Immuno deficiency virus infection / Aquired Immuno Deficiency Syndrome  is caused a Retro-virus called Human Immuno Deficiency virus.
  • Enzymes like Reverse Transcriptase, Integrase, Protease etc., of Retrovirus plays an important role in causing HIV infection to the host cell.
  • Unprotected sexual Intercourse with HIV infected partner transmits the HIV virus from the opposite sex partner majorly. 
  • Travelling to HIV endemic area or living in such area is also a major risk factor of AIDS.
  • Sharing of Syringes or needles already used by HIV infected persons. 
  • Transmission through blood transfusions from HIV infected person.
  • Transmission from infected mother to foetus.

Pathophysiology of HIV Virus

  • Retrovirus comes in contact with the host cell membrane with the help of Glycoprotein (gp)120 and 41 receptors non-covalently.  
  • Entry of retro-virus into the host cell cytoplasm and converts its RNA into DNA with the help of Reverse transcriptase enzyme.
  • Transcription can be defined as the conversion of DNA copy to m-RNA during gene expression . Retrovirus has the ability of Reverse transcription, where viral RNA is coverted to DNA similar to that of host cell DNA.
  • The newly formed viral DNA slowly gets incorporated into the host DNA with the help of enzyme Integrase. Viral DNA becomes a part of host DNA and starts multiplying by Replication of DNA into multiple copies.
  • Transcription process occurs during which the DNA will be copied and converted into m-RNA.The viral RNA transcript produced in multiple copies followed by translation where proteins get synthesized from m-RNA.
  • Protease enzyme of virus helps in the formation of outer protein coat layer called Capsid. All the parts like RNA and capsid assembled to form a new virion.
  • The newly formed virions or virus particles will be released out from the host cell into the external environment and starts infecting other host cells.
   Image result for life cycle of retrovirus in host cell

Signs and Symptoms

  • Headache, Meningitis, Encephalitis
  • Joint pain
  • Swelling of Lymph nodes
  • GIT disturbances like Esophagitis, Nausea, Vomiting and Diarrhoea
  • Night sweats
  • Skin rashes
  • Fever lasting more than a month
  • Respiratory disorders like pneumonia and Tuberculosis
  • Dry cough and sore throat
  • Muscle pain
  • Fatigue and tiredness
  • Unexplained Weight loss by 10 % of body mass
  • HIV virus destroys T-Lymphocytes and weakens the Immune system
  • Development of Tumours in different parts of  the body.

Diagnosis

  • ELISA-Enzyme Linked Immunosorbent Assay to detect HIV infection.
  • Westren Blotting Technique, is followed if HIV is positive for ELISA.
  • Indirect Immunoflourescence test.
  • Radio Immunoprecipitation test.
  • Molecular testing by PCR (Polymerase Chain Reaction)

Treatment

  • Anti-Retro-viral therapy(ART) is the most common treatment given to HIV-infected persons.
  • It is the combination of HIV drugs which may not cure HIV, but increases the lifespan of the infected person in a healthier way and also reduces the risk of HIV transmission.
  • Anti-Retroviral drugs include Nucleoside reverse transcriptase inhibitors, Non-nucleoside reverse transcriptase inhibitors, Protease Inhibitors, Fusion Inhibitors etc.,
  • Nucleoside RT Inhibitors like Zidovudine, Stavudine, Lamivudine, Abacavair etc.,act by inhibiting Reverse transcriptase enzyme thereby inhibiting formation of viral RNA to DNA.
  • Non-nucleoside RT Inhibitors like Nevirapine, Delavirdine, Efavirenz etc., act by inhibiting the incorporation of viral DNA into the host DNA thhereby inhibiting the replication of virus asssociated host DNA.
  • Protease Inhibitors like Indinavir, Saquinavir, Ritonavir etc., act by inhibiting the protease enzyme which helps in maturation of virus to form capsid layer. 
  • Fusion Inhibitors like Enfuvirtide act by inhibiting the fusion of gp120 and 41 receptors of HIV virus to the host cell surface.
  • Treatment slows down the growth, replication and progession of virus.

Preventive Measures

  • Screening of blood and blood products.
  • Educate in safe sex practices. Avoid intercourse with multiple partners.
  • Early detection and treatment of sexually transmitted diseases.
  • Avoid sharing of syringes and needles used by others.
  • Avoid breast feeding by HIV-infected mothers to their babies. 
  • Avoid taking drugs and excess Alcohol.

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