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HIV-negative partners face infection risk

By Nicole Namubiru

Doctors explain why it’s best to use protection in a discordant relationship

If a couple is in a long term sexual relationship and one of them is HIV-positive and the other is negative, scientists refer to them as a `discordant couple’. Dr Raymond Mwebaze, a general physician at St. Raphael of St. Francis Hospital Nsambya, says discordant couples are becoming quite common.   “It is common that you will find HIV discordant couples some of which are discordant by choice,” he says.

Dr Mwebaze is describing an intriguing phenomenon of an HIV-negative person deliberatively choosing to be in a relationship with an HIV-positive person.  Traditionally, it is unexpected that anyone who is HIV-negative would be in sexual contact with one who is positive.

But that was in the past days, before the Anti-RetroViral (ARV) drugs were introduced and contracting HIV was like being sentenced to death.

Part of the reason that HIV-negative people are deliberatively choosing to be in a relationship with an HIV-positive person is that studies and findings on HIV transmission have proved that it is possible for a negative partner to be in an active sexual relationship with another that is positive for quite some time and not contract the virus.  But there is a danger. “It is not a guarantee that the HIV negative partner will remain uninfected if they continue in an active sexual relationship with their HIV positive partner. This is because it is not clear what the reasons for discordance are,” cautions Dr Ben Kiwanuka of Mukwaya General Hospital. He advises such couples to nevertheless use protection during sex.

“Chances of contracting the virus cannot be ruled out,” he says.

The human body has several infection fighting mechanisms, one of which is called lymphocyte or white blood cell-mediated immunity. One of the White Blood Cells (WBCs) is known as the T-cell lymphocyte (T-cell). There are two main types of T-cells. One type has molecules called CD4 on its surface which helps organise the immune system to respond to infection.The other T-cell has a molecule called CD8 which destroys cells that are infected and produces antiviral substances.

Usually, when there is an infection, the number of WBCs in the blood increases to fight the infection. It does this by the CD4 replicating itself.

Scientists have found that HIV cannot live or survive outside a T-cell but, unfortunately, HIV has found a way of attaching itself to CD4 cells. The more the CD4 replicates, the more the virus also replicates. This is how HIV multiplies itself in the human body. In the process, the CD4 cells get infected and are attacked and destroyed by the CD8 cells.

Even while a person with HIV feels well and has no symptoms, billions of CD4 cells are infected by HIV. Meanwhile, in a counter attack as the immune system attempts to protect the infected person, thousands of CD8 cells attack and destroy thousands of infected CD4 cells each day.

The measure of white blood cells (WBCs) per cubic millimetre of blood in a person’s body is what doctors call the CD4 count. In a normal adult body there are 4,000 to 10,000 (average 7,000) WBCs per cubic millimetre of blood.

However, as HIV infection progresses, more and more CD4 cells are destroyed. So a person’s CD4 count gives a good idea of how far the virus has progressed. Scientists believe most HIV transmission is from people with CD4 counts under 350.

Dr Mwebaze says scientists believe that in a discordant sexual relationship, the negative partner might have a difference in their cell receptors that the virus fails to find its way into the CD4 cell.

He bases on a famous study done in Nairobi on the so-called ‘Nairobi Prostitutes’ who were found to be HIV negative even when they had had unprotected sex with several partners, some of whom were found to be HIV positive.

“They were found to have changes on their cell surfaces that are presumed to be protective. The receptors on the surface of the cells on which the HIV virus should attach itself and enter the cell may be different from the normal. This means that the virus cannot penetrate into the cell,” he says.

“The other plausible factor could be as a result of the presence of Immunoglobulin A (IgA) anti-bodies in the body fluid at the point of sexual entry. It could be in the vaginal secretions or the semen. These anti-bodies don’t allow the virus to survive in the secretion. This could also protect a person from getting infected by the virus even if they have sexual contact with a positive person,” he adds.

He says it could also be that if someone is taking Anti-RetroViral (ARV) drugs correctly and gets proper feeding, their CD4 count is bound to be higher. He says chances of transmitting the virus to the negative partner become minimalbecause the virus is nearly suppressed. As a result, Dr Mwebaze says, HIV transmission will reduce if more people test and those found positive start taking medicine early. “The drug could wipe out the virus to levels that are almost not infective,” he says, “This could put their viral load to less than 20 copies per ml a level of viral load that is almost non infective.” But the viral load can rise and the HIV-negative partner in the relationship can then get infected. This pre-existing danger of infection is the reason doctors advise the HIV-negative partner in a discordant sexual relationship to protect themselves by using a condom.

“Anyone not protecting themselves is still prone to HIV. This cannot be ruled out,” says Dr Kiwanuka. He adds: “More research is being done by our very own doctors on the subject. The previous findings have shown that a patient who has successfully suppressed the virus and having their CD4 going up will barely transfer the virus to another person but this does not rule out the possibility that they may transfer the virus.”

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