MT38 - HIV

• Human Immunodeficiency Virus (HIV)


  Targets and overtime destroys the immune system, especially the CD4 T Cells, which are crucial in fighting infections and diseases
• Acquired Immunodeficiency Syndrome (AIDS)


  The most advance stage of HIV infection
• HIV


  Member of the RNA virus family Retroviridae, a type D retrovirus of the Lentivirus subfamily
• Two types of HIV


  • HIV-1
  • HIV-2
• HIV-1


  • Discovered independently by Luc Montagnier of France (1983) and by Robert Gallo and Jay Levy of the United States (1984)
• HIV-2


  • Discovered in 1986; it is related to HIV-1 but is a genetically distinct virus
  • Typically less virulent and progresses more slowly than HIV-1
  • If left untreated, it could still cause severe diseases
• Similarities between HIV-1 and HIV-2


  • Both types exhibit similar symptoms and could lead to AIDS if left untreated
• Differences between HIV-1 and HIV-2


  • Scope: HIV-1 is worldwide, HIV-2 is mainly in West Africa
  • Pathogenicity: HIV-1 is high, HIV-2 is low
  • Rate of Transmission: HIV-1 is high, HIV-2 is low
• Scope of HIV-1


  Believed to have originated from chimpanzees; spread worldwide through international travels (migration), unprotected sex
• Scope of HIV-2


  Originated from mangabey monkey, which are common in West Africa for decades already, particularly in Senegal, Guinnea-Bissau, and Ivory Coast
• Pathogenicity of HIV-2


  • Although they have similar routes of transmission, HIV-2 is less efficiently transmitted, limiting its spread within a certain region or area
  • HIV-2 is more endemic for decades
  • Prevalence of HIV-2 in this area, compared to the other parts of the world, is very high due to historical factors and introduction of the virus to the human population
• Rate of transmission


  HIV-1 is more predominant worldwide and is responsible for the majority of HIV infections globally, while HIV-2 is contained in West Africa only
• Former names of HIV


  • Human T-cell lymphotrophic virus type III (HTLV-III)
  • Lymphadenopathy-associated virus (LAV)
  • AIDS-associated retrovirus (ARV)
• Variants of HIV-1


  • Group M (main/major group): with 9 subtypes/ clades (A-D, F-H, J, K) – responsible for the majority of HIV-1 infections worldwide
  • Subtype C – predominant worldwide
  • Subtype B – most prevalent in the US and Europe
  • Group N (non-M/non-O, or new group) : these are rare
  • Group O (outlier group)
• Variants of HIV-2


  • Group A and Group B
  • Less common
  • Less genetically diverse
• These groupings are important in order for us to understand the genetic diversity and epidemiology of the virus, because these factors could influence their transmission, disease progression, and treatment outcome
• WHO Reports or Estimations on HIV (worldwide status)


  • In 2007: 33.2 million people living with HIV infection, 2.5 million people became newly infected, 2.1 million died of AIDS
  • In 2015: 37 Million people living with HIV infection, 1.1 Million died of-AIDS related causes
  • In 2016: 36.7 million people living with HIV infection, 1.8 million people became newly infected, 18.2 million receiving HIV treatment, 1 million died of AIDS-related causes
  • In 2022: 45.7 million people living with HIV infection
• Among all the countries worldwide, those in Sub-Saharan Africa have the highest rate of cases with HIV
• Countries in Sub-Saharan Africa with highest HIV prevalence


  • Eswatini
  • Lesotho
  • South Africa
• In 2022, Eswatini has the highest prevalence of HIV, with the rate of almost 26%
• HIV statistics in the Philippines


  • As of January 2023, there are 110,736 HIV cases reported
  • 10,111 new HIV cases reported since January 2017
  • 1,277 progressed to full-blown AIDS
  • 428 led to death
• Regions in the Philippines with the most number of reported HIV cases


  • National Capital Region (NCR)
  • Calabarzon (Region 4A)
  • Central Luzon (Region 3)
  • Central Visayas (Region 7)
  • Davao Region (Region 11)
• As of 2023, Central Visayas ranked 2nd, with a total of 1,454 cases
• Causes of the Prevalence of HIV in the Philippines


  • Low Awareness and Prevention
  • Stigma and Discrimination
  • Limited access to healthcare services
  • Injecting drug use
  • Lack of comprehensive HIV Prevention Programs
• Transmission of HIV


  Spread through: vaginal or seminal fluids, blood, and/or breastmilk
• Major routes of HIV transmission


  • Intimate sexual contact
  • Parenteral
  • Perinatal - from infected mother to infant
• Intimate sexual contact


  • The majority of cases of HIV infection have occurred by sexual transmission, through either vaginal or anal intercourse
  • Anal sex poses high risk, due to the vulnerability of the anal mucosa
  • Worldwide, 85% of the cases are from heterosexual contact. In the US, the largest number of cases are from anal intercourse in homosexual males
  • The presence of other STDs such as syphilis, gonorrhea, and genital herpes increases the likelihood of infection due to the disruption of protective mucous membranes
• One of the projects of the DOH is to provide free condoms and lubricants
• Parenteral transmission


  • This involves parenteral exposure to infected blood or other body fluids
  • Transmission has occurred through: sharing of contaminated needles by IV drug users, blood transfusions or the use of clotting factors, occupational injuries with needle sticks or other sharp objects, mucous membrane contacts in health-care workers exposed to infectious fluids
  • Body fluids considered to be potentially infectious: blood, semen, vaginal secretions, CSF, synovial fluid, pleural fluid, peritoneal fluid, pericardial fluid, amniotic fluid, other body fluids containing blood
  • Fluids that are not infectious unless containing visible blood: saliva, sputum, nasal secretions, tears, sweat, urine, vomit, feces
• In parenteral transmission, the virus bypasses our natural barriers, which is our skin and mucus membranes, as it enters our bloodstream directly
• Precautions such as using sterile syringes and equipment, implementing proper infection control measures in our healthcare settings, and screening of blood and organ donors are really important in reducing the risks of this kind of transmission
• Perinatal transmission


  • Mother-to-child or Vertical transmission
  • Transmission can occur during pregnancy, by transfer of blood during delivery, breastfeeding
  • We now have effective interventions like the anti-retroviral therapy, that the mothers can take during their pregnancy and delivery and to the new born and during its breastfeeding period, which can reduce the risk of HIV transmission and infection (< 1%)
  • Sometimes, cesarean delivery is also recommended to reduce the risk of transmission if the mother's viral load is already high
• HIV viral structure


  • HIV is classified as a retrovirus; it contains RNA as its nucleic acid and a unique enzyme, called reverse transcriptase, that transcribes the viral RNA into DNA
  • HIV is a spherical particle, 100 to 120 nm in diameter, which contains an inner core with two copies of single stranded RNA, surrounded by a protein coat or capsid and an outer envelope of glycoproteins embedded in a lipid bilayer
  • Envelope: derived from the host cell membranes; contains viral glycoproteins which are essential for the virus' entry to the host cells
  • Capsid: inside the viral envelope; surrounds the RNA
  • The glycoproteins are knoblike structures that are involved in binding the virus to host cells during infection
• Major HIV genes and their functions

  • pol: Codes for viral enzymes like reverse transcriptase, integrase, protease
  • gag: Codes for nucleocapsid and core proteins
  • env: Codes for envelope glycoprotein
  • tat: Codes for transactivator of transcription protein, important in regulating viral transcription and enhancing viral gene expression
  • rev: Codes for regulator of virion expression protein, essential in exporting partially spliced / unspliced viral DNA from the nucleus to the cytoplasm
  • nef: Codes for negative factor protein, downregulating cell surface receptors, enhance viral replication, and modulate host cell signaling pathways
  • vpu, vpr, vif
• HIV proteins of serodiagnostic importance

  • HIV-1: gp41 (envelope transmembrane protein), gp160/120 (envelope external protein), p24 (core structural protein)
  • HIV-2: gp34 (envelope transmembrane protein), gp140 (envelope external protein), p26 (core structural protein)
• gp34 and gp140 of HIV-2, forms the viral envelope spikes that mediate the viral entry to host cells
• Negative Factor


  Downregulating cell surface receptors, enhance viral replication, and modulate host cell signaling pathways
• HIV Proteins of Serodiagnostic Importance


  • vpu
  • vpr
  • vif
• gp41


  Envelope (transmembrane protein), facilitates entry of virus to host cell; mediates fusion between viral and host cell membrane
• gp160/120


  Envelope (external protein), gp160 is the precursor of gp41 and 120, is initially sensitized as single polypeptide chain but has 2 sub-unit; important for the initial assembly and maturation of the virus