Immune response in HIV-1-infected children with thalassaemia given a primary course of DPT vaccine before acquiring HIV-1 infection

The effect of HIV infection on immune response to diphtheria and tetanus primary immunisation was investigated in 24 HIV-1-positive multi-transfused (MT) children with thalassaemia and compared with 48 HIV-1-negative MT thalassaemic children and 36 HIV-1-negative non-transfused (NT) children in the community. Diphtheria and tetanus antibody levels in the HIV-1-positive MT group were comparable with the two HIV-negative groups. The proportions of children with antibody titres below the protective level (i.e. <0.01 IU/ml) for antidiphtheria antibodies were 20.8, 16.6 and 16.6%, and 12.5, 12.5 and 13.9% for anti-tetanus antibodies in the three groups, respectively. On the other hand, delayed-type hypersensitivity (DTH) response to diphtheria and tetanus antigens was significantly depressed in the HIV-1-positive group compared with the HIV-negative controls. The mean percentages of both mature (CD20+) and immature (CD10+) B-cell counts were significantly higher in the HIV-1-positive group than in the HIV-negative MT and NT groups (p<0.05). Levels of serum immunoglobulins and spontaneously secreted immunoglobulins were significantly higher in the HIV-1-positive group compared with both HIV-negative groups. The HIV-1-positive group showed a mean (SD) IL-6 of 52.9 (28.8) pg/ml compared with 23.7 (12.1) pg/ml and a detection rate of 54.2% in the HIV-negative MT group, and 23.6 (8.2) pg/ml and a 50% detection rate in the HIV-negative NT group. The IL-2 level was significantly lower (p<0.05) in the HIV-1-positive group [41.7% detection rate and mean (SD) 28.8 (17.1) pg/ml] than in the HIV-negative MT and NT groups [75% and 83.3% detection rates and mean (SD) 57.2 (42.3) pg/ml and 99.3 (51.1) pg/ml, respectively]. During follow-up for 3 years, the frequency of major infections was significantly higher in the HIV-1-positive group than in the other two groups. Acute pneumonia and acute sinusitis were the predominant infections regardless of HIV status while primary bacteraemia, osteomyelitis, pyogenic meningitis and septic arthritis were common in the HIV-1-positive group. We conclude that, in HIV-1-infected children pre-immunised with DPT, DTH response to diphtheria and tetanus antigens might be more reliable than anti-diphtheria and anti-tetanus antibody levels in predicting susceptibility to major bacterial infections.