HIV Semen Biology
HIV Biology
Human Immunodeficiency Virus (HIV) infects cells belonging to the immune system by first binding to specific receptors on the cell surface (either CD4 or CXCR4 / CCR5), then entering the cell.
Once inside the cell, HIV engineers a copy of its genetic information to become an integral part of the cell’s genes. It does not kill the cell it infects, but takes advantage of the cell’s machinery to make new virus particles that are released from the surface of the cell. The new virus then attaches to a new, uninfected (CD4) cell, to repeat the process.
Not all virus-infected cells constantly produce virus particles; some only do so when stimulated by another type of infection, such as the flu, or bacteria. Once stimulated, they produce new HIV particles, and then die. The continuous loss of CD4-cells, key players in immune health, gradually erodes the immune system, which leads to AIDS.
Most of the HIV-infected cells are in lymph nodes, a few circulate in the blood stream, and others are scattered throughout the body. Importantly, even after 40 years of research, the organ source of semen HIV is unknown.
Semen Biology
Semen is a complex and unusual body fluid. It does not exist anywhere within the body, it is created by ejaculation of cells and fluids from three tissues (epididymis, seminal vesicles and prostate) carried by two duct systems (vas deferens and urethra). Each semen specimen is unique.
The testis produces millions of sperm each day which take about 6 weeks to mature from spermatogoonia to stream-lined cells with a tail that moves. The sperm are produced inside tubes within the testis which protects them from the outside world. Once they gain tails, they leave the testis and enter the epididymis. Their transit through the epididymis takes another few weeks, and they are stored near the vas deferens, the tube that connects the testis/epididymis with the urethra in the penis.
At ejaculation, muscles in the epididymis, vas deferens, seminal vesicles and prostate all contract to force sperm and fluids out the opening of the urethra. The average specimen is about half a teaspoon in volume and contains approximately 100 million sperm and 2 million non-sperm cells. The non-sperm cells are either immature sperm that left the testis prematurely, and/or cells that belong to the immune system, including CD4-cells that could be infected with HIV.
HIV Therapy
To date there are about two dozen antiretrovirals, plus many drug combinations. The drugs either inhibit virus entry into cells, or inhibit some part of the HIV life cycle so the production of new virus particles is halted. Effective antiretroviral therapy reduces the number of free virus particles circulating in blood to zero, but it does not eliminate HIV infected cells, and it may not eliminate HIV from semen specimens.
One of BRF’s research initiatives explores therapy using HIV-resistant stem cells. This offers hope for a cure for HIV disease.
