More than 30 years ago, the United States first reported Acquired Immune Deficiency Syndrome (AIDS), or AIDS, that occurred in homosexual people. According to its epidemic characteristics, it was first determined that its mode of transmission was sexual contact, and then it was discovered that there were also mother-to-child transmission and blood transmission. With the discovery of the pathogen, the human immunodeficiency virus (HIV), people have gradually determined that AIDS is caused by HIV infection and massive deletion of CD4+ T lymphocytes in the human body; and the way HIV invades the human body is mucous membranes and damaged skin.
The contact surface between the human body and the environment is composed of skin, mucous membranes and their derivatives. When the structure and function are complete, HIV cannot break through the skin and can only enter the human body from the mucosa (including the mucosa with complete structure and function). Therefore, the mucosa is the natural route of HIV-1 transmission.
For different ways of AIDS transmission, the way that HIV invades the human body is different. Viruses transmitted through blood invade the human body mainly through damaged skin; viruses transmitted through mothers and infants invade the human body mainly through the mucosa of the digestive tract; viruses transmitted through sexual contact invade the human body mainly through the mucous membrane of the reproductive tract and digestive tract.
The blood transmission of AIDS is mainly through blood as the carrier of HIV transmission. The blood and blood products of HIV-infected persons do not have the ability to enter a healthy human body. They need to use needles or other sharp instruments to break through the protective structure of the human skin before they can enter the body. Therefore, blood transmission is almost the people who help the virus invade the uninfected people without knowing it. As long as you don’t use HIV-carrying blood and blood products, and avoid sharps (such as needles used for intravenous drug use) punctured by the infected person’s blood, you can avoid HIV infection. But if HIV-contaminated blood comes into contact with mucous membranes, there is a risk of infection.
The mother-to-child transmission and sexual contact transmission of AIDS are mainly caused by the liquid secreted and released by the reproductive organs as the carrier of HIV transmission. Although the viruses in these secretions cannot invade the human body through the skin, they can invade the human body through various mucous membranes. It is known that HIV invades more mucosal sites. (1) Upper gastrointestinal mucosa, such as HIV-positive mother’s milk can contact the infant’s oral cavity, throat, esophagus and gastric mucosa; (2) Rectal mucosa, such as semen of HIV-positive individuals can contact rectal mucosa; (3) Female reproductive tract Mucosa, such as semen of I-HV-positive individuals can contact the mucosa of the vagina, uterus and fallopian tubes; (4) Male reproductive tract mucosa, such as the vaginal secretion of H1V-positive individuals can contact the male urethral mucosa.
Because HIV contacts a wide range of mucosal sites, and the structure of each site is different, different mucosal sites have different risks of infection after being exposed to HIV. The epithelial layer of the skin is a keratinized stratified flat epithelium, which has a good physical barrier function, so HIV can hardly penetrate the skin into the human body. Different from the skin, the mucous membrane surface is often covered with mucus. Due to the weak physical barrier, it is the site where most pathogens invade the human body. The epithelium of the mucosa related to HIV invasion includes single-layer columnar epithelium and stratified squamous epithelium. The single-layer epithelium includes the gastrointestinal mucosal epithelium and the genital mucosal epithelium above the inner neck of the uterus. It is the weakest physical structure in the HIV invasion pathway. Barrier. In the mucosa of the digestive tract, the rectal mucosa is the route of transmission with the highest risk of infection after exposure to HIV due to its weak physical barrier and large exposure to the virus during sexual transmission. There is a big difference between the upper gastrointestinal mucosa between adults and infants. Although the risk of HIV infection through the upper gastrointestinal mucosa in adults is extremely low, the infant’s gastric mucosal epithelium is composed of a single layer of epithelial cells and is immature. An important place for HIV invasion in breast milk.
The factors affecting the invasion of HIV through mucosa are very complex, and individual differences are huge. Some individuals may not be infected after repeated exposure to the virus in their mucous membranes, but the proportion of contact with uninfected individuals is very small. Although mucosal vaccines and mucosal microbicides are good methods to protect mucosa, vaccine development has not been successful; although antiviral drugs are used as topical microbicides to have a certain effect, there are still problems such as drug resistance. An in-depth understanding of HIV transmission routes and influencing factors will help to develop prevention methods for HIV transmission routes. Before there is no AIDS prevention and cure method, understanding the path of HIV invasion and deliberately avoiding contact with the virus will significantly reduce the spread of HIV.
