New Antiretrovirals Significantly Reduce HIV Viral Load

Recent research indicates that newer antiretroviral drugs are able to quickly reduce the likelihood of HIV transmission through sexual contact.

Scientists specifically evaluated how dolutegravir (Tivicay), an integrase inhibitor, reduces HIV viral load in semen. Drugs have a notoriously difficult time reaching this area of the body, which is thought to be a reservoir of the virus, according to a study published by the Journal of Infectious Diseases.

The findings from the study suggest that these new treatments improve the ability to prevent HIV transmission.

Antiretroviral treatments decrease the viral load in the blood to undetectable levels, with most patients achieving this within 6 to 9 months from treatment initiation. However, 5% to 25% of patients still have detectable levels of HIV in their semen.

“Therefore, in the case of serodiscordant couples, in which only 1 of the members is carrying the virus, in addition to condoms it is recommended that the seronegative person also takes antiretroviral drugs as prophylaxis while the viral load of their partner decreases in both blood and reservoirs,” said lead scientist Daniel Podzamczer, PhD.

Newer drugs, including integrase inhibitors such as dolutegravir, work even more rapidly to reduce the viral load.

“In this study we have focused on evaluating the rate of viral load drop in patients receiving these new treatments, namely dolutegravir,” said first author Dr Arkaitz Imaz. “We have measured the viral load in blood and semen before starting treatment, at 3 days, at 7, at 14, at 1 month, at 3 months, and at 6 months. We know that viral load drop goes quick during the first few days/weeks, then slower and it finally stabilizes. Adapting a complex mathematical-statistical model to our data and to the characteristics of our patients, we have been able to obtain a kinetic model of the specific viral load drop for each compartment, blood and semen, with this treatment regimen.”

In the study, scientists discovered the viral load dramatically decreases in the blood during the first few days, and then decreases in the semen during the second phase. They also found that despite this difference, the viral load in the semen becomes undetectable faster, since there is more to eliminate in the blood, according to the study.

"These results suggest the possibility of reducing the time of previous antiretroviral prophylaxis when using these new treatments," the researchers said.

Scientists also found that the fall pattern is more uniform in blood compared with semen, which shows the unpredictable nature of the HIV reservoir in semen. Currently, there is no proven association between the concentration of the drug in the semen and the reduction in viral load, according to the study.

"The concentration of dolutegravir in semen is more than enough to ensure viral load drop in this reservoir,” Dr Podzamczer said. "Because even though only 7-8% of the drug in the blood reaches the semen, the proportion of active drug is much higher than what the observed in blood. This was something that we did not know until now.”

Integrase inhibitors are currently the first-line HIV treatment due to the significant reductions in viral load. Additional studies are needed to evaluate the effect of other treatments, especially long-term antiretrovirals, on viral loads and their potential to reduce HIV activity, according to the authors.

“Our study reinforces this decision, especially in light of the current HIV transmission landscape,” Dr Imaz concluded. “If we reduce the time of viral load drop we clearly reduce the possibility of transmission, especially in groups at risk.”