# Better understanding of HIV treatment in young children

## Mathematics and biology

How fast does the number of virus particles in the blood decrease when you start HIV treatment? And how quickly does the number of white blood cells increase? With her background in mathematical biology, Juliane Schroeter has found answers to these questions. With this, she is taking a first step toward better informing clinicians in the timing and choice of alternative treatment strategies for young HIV patients. Schroeter will defend her thesis at Utrecht University on 19 October.

## Quality of life

Children born with HIV depend on HIV medications throughout their lives. These antiretroviral drugs keep the virus from attacking the immune system and thus allow it to function properly. However, the drugs have side effects, such as headaches, diarrhea, fatigue, nausea and vomiting. To improve children's quality of life, scientists are looking for a way to cure them "functionally": stopping the medication without the virus returning. Worldwide, there are 1.5 million people infected with HIV. Ten percent are children under the age of 10.

## Mathematical models

Curing children with HIV functionally, requires an understanding of the body's response to HIV medication. Schroeter developed mathematical models that describe how the amount of virus particles on the one hand, and white blood cells on the other develop over time in individual patients. She used the blood samples of thousands of European children in whom treatment was started within six months after birth and eventually lead to viral suppression. The blood samples came from large cohort studies.

## Only two factors

Schroeter found that the time it takes a child to suppress the virus can be predicted based on just two factors: the amount of virus particles in the blood, and the status of the immune system at the start of treatment. The prerequisite is that no complications occur during treatment. The PhD candidate also developed models showing how the number of immune cells recover in the first year of life when the immune system is still developing. Eventually, the degraded numbers of immune cells return to healthy values once treatment has been initiated.

## First step

In her research, Schroeter shows that it is very important to start treatment early for children infected with HIV. In this way, the damage done to the immune system is minimized. The time then needed to suppress the virus is shorter. With her research, Schroeter is taking a first step toward better informing clinicians in the timing and choice of alternative treatment strategies for young HIV patients. As a result, treatment is more effective, has fewer side effects and may ultimately lead to functional cure.

This research is part of EPIICAL, a collaborative effort to improve the lives of children with HIV.