Study finds t-cell level returns to normal with time

Most children with HIV who have low levels of a key immune cell eventually recover levels of this cell after they begin treatment, according to a new study conducted by researchers at UCLA and other institutions in the US and Brazil.

The researchers were funded by the National Institutes of Health.

''We were pleased to find that the vast majority of children experience immune system recovery with effective therapy,'' said Dr. Paul Krogstad, professor of paediatric infectious diseases and of molecular and medical pharmacology at the David Geffen School of Medicine at UCLA, and the study's first author. ''Our study also provided the most detailed information to date about the timing of this recovery in school-age children.''

Krogstad is also a member of the UCLA AIDS Institute and Center for AIDS Research.

CD4+ t cells are a major target of HIV. In about 15 per cent of adult patients, the cells fail to rebound after the virus has been suppressed with medication, a scenario that is associated with life-threatening illnesses.

The new study, which was published online in the journal AIDS, was intended to determine to what extent children who were infected with HIV around the time of birth were at risk for this condition and whether this failure carried with it a major risk for serious infection.

The failure of CD4+ t cells to rebound occurs only infrequently in young children with HIV, said Rohan Hazra, a study author and the chief of the maternal and paediatric infectious disease branch at the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, which provided much of the funding for the study.

''The comparatively few children whose CD4+ cells failed to rebound did not appear to be at any greater risk for serious infection than children with higher CD4+ counts,'' he said.

Hazra added that the findings do not appear to change treatment recommendations for children with HIV: anti-retroviral treatment to suppress the virus and periodic follow-up examinations to detect the first signs of any serious infections.

To conduct their analysis, researchers reviewed data from three research networks caring for more than 3,700 children in the US, Central and South America, and the Caribbean who were infected with HIV before or during birth.

The researchers followed the CD4+ cell counts of 933 children who were at least 5 years old when they started anti-HIV treatment. Healthy CD4+ cell counts range from 500 to 1,200 cells per blood sample. Fewer than 500 cells per sample is considered low, and 200 or fewer per sample is considered very low. After one year of anti-HIV treatment, 86 per cent of children in the study achieved CD4+ counts of 500 or more. After two years of anti-HIV treatment, 92 per cent surpassed this threshold.

The researchers also reviewed the children's records for signs of serious illness during the course of their treatment. Known as CDC Category C events, these illnesses are a sign of the seriously weakened immune system in people with AIDS. A total of nine children experienced such events.

The occurrence of these events did not differ statistically between those having CD4+ cell counts below 500 at the time of the event (four children) and those with counts above 500 (five children).

The study authors noted that compared to adults with low CD4+ counts at the beginning of treatment, CD4+ counts in children increase to 500 or more with time after treatment has begun.

Yet, despite such increases, some children had Category C conditions or other significant illnesses during the first three years of HIV treatment. The researchers wrote that additional studies are needed to understand this higher risk of illness.

Additional funding was provided by several NIH institutes: the National Institute on Drug Abuse, the National Institute of Allergy and Infectious Diseases, the Office of AIDS Research, the National Institute of Mental Health, the National Institute of Neurological Disorders and Stroke, the National Institute on Deafness and Other Communication Disorders, the National Heart Lung and Blood Institute, the National Institute of Dental and Craniofacial Research, and the National Institute on Alcohol Abuse and Alcoholism.