Most reconstituted CD4 cells naive after HAART in children with HIV

Immune repopulation after highly active antiretroviral therapy (HAART) is different in children than in adults, according to a report in the April 15th issue of the Lancet.

In particular, reconstituted CD4 cells in adults tend to be memory cells carrying the CD45RO marker, while new CD4 cells in children tend to be naive T cells carrying the CD45RA marker, Dr D M Gibb, of the Medical Research Council Clinical Trials Unit, in London, UK, and other investigators for the Paediatric European Network for Treatment of AIDS Steering Committee say in the journal.

The investigators monitored immune repopulation in 25 vertically HIV-infected children for 1 year after HAART. Treatment with HAART brought about a 3-log reduction in plasma HIV RNA load that lasted for at least 1 year. Treatment also induced a ‘substantial increase in median CD4 cells,’ the authors write, from 403 cells/mm3 at baseline to 650 cells/mm3 at 24 weeks and 631 cells/mm3 at 48 weeks.

At 48 weeks, 71% of the reconstituted CD4 cells in these children were naive cells, Dr Gibb and colleagues say. This contrasts with adult patients, in whom ‘the initial rise in CD4 cells after HAART is due to expansion of CD45RO memory cells.’ The team attributes this difference to the presence of functioning thymus tissue in children.

The findings ‘raise important questions about therapeutic strategies to be followed in children,’ the investigators note. ‘Compared with adults, the presence of a functioning thymus in children may allow alternative approaches to treatment, including removal of memory cells, the major reservoir of HIV-1, which would not be possible in adults.’