IAS: 3TC infant prophylaxis during breast-feeding reduces HIV infection rate at six months

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Daily dosing with 3TC (lamivudine, Epivir) for infants of HIV-positive mothers reduces the risk that a baby will acquire HIV infection from its mother through breast-feeding, according to the results of a joint Tanzanian/Swedish study presented last week at the Third International AIDS Society Conference on HIV Treatment and Pathogenesis in Rio de Janeiro, Brazil.

The MITRA study was conducted in Dar es Salaam, Tanzania’s largest city. It recruited pregnant HIV-positive women with a median age of 26 years and median CD4 cell count of 419 cells/mm3. The vast majority of mothers were asymptomatic (WHO stage 1: 89%), but 13.7% had CD4 cell counts below 200 cells/mm3 and thus had a high risk of transmitting HIV to their infants perinatally.

Mothers received treatment according to the PETRA trial protocol, which had tested AZT/3TC (Combivir) given from week 36 of pregnancy until one week after delivery as prophylaxis against mother-to-child transmission. Infants received AZT/3TC for one week after birth, and then received daily treatment with 3TC (4mg/kg) throughout the breast-feeding period. Mothers were counselled to stop breast-feeding by six months after birth, although 22% were still breast-feeding 26 weeks after birth.

Glossary

control group

A group of participants in a trial who receive standard treatment, or no treatment at all, rather than the experimental treatment which is being tested. Also known as a control arm.

historical control

A comparison group of people not taking an experimental drug, taken from previous clinical trials (when old data is compared to new data).

advanced HIV

A modern term that is often preferred to 'AIDS'. The World Health Organization criteria for advanced HIV disease is a CD4 cell count below 200 or symptoms of stage 3 or 4 in adults and adolescents. All HIV-positive children younger than five years of age are considered to have advanced HIV disease.

WHO stage

A simplified system to describe four clinical stages of HIV-related disease, based on clinical parameters (symptoms, weight loss and different opportunistic infections) rather than decreasing CD4 cell count. Stage I is asymptomatic, stage II mild symptoms, stage III advanced symptoms and stage IV severe symptoms (an AIDS diagnosis).

mother-to-child transmission (MTCT)

Transmission of HIV from a mother to her unborn child in the womb or during birth, or to infants via breast milk. Also known as vertical transmission.

HIV infection was significantly less frequent in 3TC-treated infants at six months compared to a historical control group of infants born to mothers who participated in the original PETRA study. Infection was diagnosed using an Amplicor HIV-1 DNA assay, which is the only reliable method of detecting HIV infection in infants.

4.9% of the 3TC-treated infants were HIV-positive by month six, compared to 11.9% of the historical control group (p=0.003). The rate of infection at six months was only slightly higher than the infection rate at week six among the 3TC-treated infants (3.4%).

A potential limitation of this study is that the majority of mothers stopped breast-feeding within six months of delivery, leading some experts to suggest that it is difficult to disentangle the effect of early weaning from the effect of 3TC. However the median duration of breast-feeding was 20 weeks, suggesting an extended period of risk for most infants. The research group did not present any analysis of transmission risk according to maternal baseline characteristics, particularly baseline CD4 cell count, and there was no information on maternal viral load in plasma or breast milk, so it is not possible to determine whether 3TC prophylaxis was more successful for infants of mothers with less advanced HIV disease.

References

Kilewo C et al. Prevention of mother to child transmission of HIV-1 through breastfeeding by treating infants prophylactically with lamivudine in Dar es Salaam, Tanzania. Third International AIDS Society Conference on HIV Treatment and Pathogenesis, Rio de Janeiro, abstract TuPe5.3P01, 2005.