AntiRetroViral (ARV) drugs assist by interfering with and interrupting viral replication and thus allowing now's immune system to recover. What then happens is that so long as the patient remains adherent to the medications (for treatment to be effective, adherence rates of over 97% are expected, which means a patient should miss, if at all, a maximum of one dose per 30days. It's that strict!), and barring appearance of viral resistance, the viral load (i.e no. of viral particles) should decline as the immune system recovers (as evidenced by general increase in especially levels of CD4 immune cells and declining incidence of common opportunistic infections such as T.B and cryptococcal meningitis).

The viral load will decline to such low levels that it remains or becomes undetectable, key word here being UNDETECTABLE. It doesn't mean that there're no viral particles, it just means that the machines we currently have are not sensitive enough to detect the few viral particles that are present.

I should hasten to add, too, that there are what we call sacrosanct sites where the virus 'hides' and drugs cannot get to it, examples being the brain, the testes and the liver. In the brain, there's what we call the Blood-Brain Barrier (BBB or big bad boy ). In this BBB, research has shown that there exists a glycoprotein that ACTIVELY pumps out ARV molecules and prevents the drugs from achieving therapeutic levels in the brain. In the testes, there too exists a Testicular-Blood Barrier which also prevents drug molecules from crossing and concentrating in the testes. These mechanisms are thought to have evolved over time to prevent harmful stuff from gaining entry into and accumulating in these organs but, to the extent that it prevents us from achieving therapeutic concentrations of drugs in there, then it serves to our disadvantage. Call it a double-edged sword.

Of importance here too, it's worth remembering that viruses in general, including HIV, aren't organisms per se like say bacteria or fungi but rather are just genetic material. We have both DNA viruses (e.g Hepatitis B virus - HBV) and RNA viruses (e.g HIV). Viruses thus are obligate inracellular (can only exist viably inside a LIVING cell) and thrive by hijacking the normal cell division to replicate themselves.

These then are the reasons we recommend to patients that, no matter the undetectable viral levels, they must continue taking their ARVs as well as minimize risky sexual behavior (unprotected sex). As part of therapeutic monitoring, HIV +ve patients on ARVs have their biochemical and viral load tests done consistently every 6months.

Question has already been answered. A -ve test result in a patient previously confirmed as +ve and subsequently put on ART (AntiRetroviral Therapy) isn't an indicator of total absence of virus. It's -ve because the viral load is undetectable, not because the virus is absent. Which is more or less what the first link you gave is trying to say in other words.

Your second link talks mainly about discordant couples having unprotected sex if the +ve one is on treatment and their viral load is undetectable. I just told if the sacrosanct sites where the virus hides, one of which is the testes. Question is, would you advocate for any woman to take that risk? I know I wouldn't. The study results talk of 96% reduction but what of the remaining 4%? And finally, the article concludes, and I quote:

“If you want to have your risk of transmitting to others be zero, be on antiretrovirals religiously and also use condoms,” Vermund says.

Need I say any more?

For information purposes, here's an article that tries to explain the concept of 'failure to achieve therapeutic concentration in the brain':

http://www.ncbi.nlm.nih....C3227164/?report=classic

If I understand @Maka's question correctly, He's asking... If he goes for a test, WITH A PARTNER, are there chances that the said partner could test -Negative, but are in actual fact +Positive?

And if that were the case, isn't that information that should be out in the general public. How many people are going for test, feeling 'safe', and going on to contract the virus? SCARY STUFF!!

Ok @Mukiri, you bring up a different angle to his query that I hadn't foreseen.

In the HIV life cycle, it ordinarily takes about 3weeks to 6 months for the virus to appear in blood after initial sexual exposure. This period can vary, either shorter or longer, depending on your initial immune system prior to exposure. This is what is generally known as the window period of the infection, i.e. the period during which one is HIV +ve and infectious (i.e. capable of infecting others) but the virus isn't yet detectable in blood. That's why it's generally recommended to repeat the test 30days and 90days (3 months) after the initial test. The vast majority of people, well over 90%, have a measurable/detectable immune response within 3 months.

I know at the back of your mind is probably a curiosity about the mechanisms of testing, a curiosity I now seek to assuage. There generally are two types of HIV tests that we use locally:

i. Antibody-based tests e.g. Western blot and ELISA (Enzyme-Linked ImmunoSorbent Assay) test. These generally test for the anti-HIV antibodies. This means that after the initial exposure, the virus must replicate enough for the body to mount an immune response whose antibodies are then detected by the test. This explains the latent or lag-period during which it is possible to get a -ve test even though one is actually +ve.

Being an antibody-based test, two main candidates are especially likely to give false +ve (as opposed to the aforementioned false -ve) results:
- candidates of a HIV vaccine test.
-young babies born of HIV +ve mothers, since babies get and rely on maternal antibodies until such a time that their immune systems are mature enough to make their own (see a brief explanation here: http://biology.stackexch...ze-their-own-antibodies).

The rapid tests commonly used in hospitals and VCT Centres fall under this category.

ii. Antigen-based tests e.g. PCR and p24 tests. These tests detect the actual viral DNA (the antigen) in blood long before the body has had a chance to mount an immune response to it. For this reason then, it is the most accurate but also very expensive. Locally, we only use it routinely for Early Infant Diagnosis (EID) through KEMRI as research clearly shows general improvement in quality of life if ART is initiated early for HIV +ve infants. Remember too that the virus tends to 'hide' in the brain and can thus cause some CNS-deficiency if treatment is delayed.

p24 is no longer widely used due to its lack of sensitivity and the fact that it is only applicable at a specific time in the course of infection, just before the body begins to mount an immune response.

I hope this is clear now my friends. Kama kuna maswali mengine, yalete pia. @Lolest! uliza yako pia mblo.