Direct binding of peptides to MHC class I molecules on living cells. Analysis at the single cell level.

To directly assess the binding of exogenous peptides to cell surface-associated MHC class I molecules at the single cell level, we examined the possibility of combining the use of biotinylated peptide derivatives with an immunofluorescence detection system based on flow cytometry. Various biotinylated derivatives of the adenovirus 5 early region 1A peptide 234-243, an antigenic peptide recognized by CTL in the context of H-2Db, were first screened in functional assays for their ability to bind efficiently to Db molecules on living cells. Suitable peptide derivatives were then tested for their ability to generate positive fluorescence signals upon addition of phycoerythrin-labeled streptavidin to peptide derivative-bearing cells. Strong fluorescent staining of Db-expressing cells was achieved after incubation with a peptide derivative containing a biotin group at the C-terminus. Competition experiments using the unmodified parental peptide as well as unrelated peptides known to bind to Kd, Kb, or Db, respectively, established that binding of the biotinylated peptide to living cells was Db-specific. By using Con A blasts derived from different H-2 congenic mouse strains, it could be shown that the biotinylated peptide bound only to Db among > 20 class I alleles tested. Moreover, binding of the biotinylated peptide to cells expressing the Dbm13 and Dbm14 mutant molecules was drastically reduced compared to Db. Binding of the biotinylated peptide to freshly isolated Db+ cells was readily detectable, allowing direct assessment of the relative amount of peptide bound to distinct lymphocyte subpopulations by three-color flow cytometry. While minor differences between peripheral T and B cells could be documented, thymocytes were found to differ widely in their peptide binding activity. In all cases, these differences correlated positively with the differential expression of Db at the cell surface. Finally, kinetic studies at different temperatures strongly suggested that the biotinylated peptide first associated with Db molecules available constitutively at the cell surface and then with newly arrived Db molecules.

Parents living with HIV in a high-income country: do patients need specific support?

The number of HIV-infected persons with children and caregiving duties is likely to increase. From this statement, the present study was designed to establish how HIV infected caregivers organise their parenting routines and to determine their support needs. A further aim was to ascertain caregivers' perception of conspicuous behaviours displayed by their children. Finally, it sought to determine the extent to which the caregivers' assessment of their parenting activity is influenced by the required support and their children's perceived conspicuous behaviours. The study design was observational and cross-sectional. Sampling was based on the 7 HIV Outpatient Clinics associated with the national population-based Swiss HIV Cohort Study. It focused on persons living with HIV who are responsible for raising children below the age of 18. A total of 520 caregivers were approached and 261 participated. An anonymous, standardised, self-administered questionnaire was used for data collection. The data were analysed using descriptive statistical procedures and backward elimination multiple regression analysis. The 261 respondents cared for 406 children and adolescents under 18 years of age; the median age was 10 years. The caregivers' material resources were low. 70% had a net family income in a range below the median of Swiss net family income and 30% were dependent on welfare assistance. 73% were undergoing treatment with 86% reporting no physical impairments. The proportion of single caregivers was 34%. 92% of the children were living with their HIV infected caregivers. 80% of the children attended an institution such as a school or kindergarten during the day. 89% of the caregivers had access to social networks providing support. Nevertheless, caregivers required additional support in performing their parenting duties and indicated a need for assistance on the material level, in connection with legal problems and with participation in the labour market. 46% of the caregivers had observed one or more conspicuous behaviours displayed by their children, which indicates a challenging situation. However, most of these caregivers assessed their parenting activity very favourably. Backward elimination multiple regression analysis indicated that a smaller number of support needs, younger age of the eldest child and fewer physical impairments on the part of the caregiver enhance the caregivers' assessment of their parenting activity. Physicians should speak to caregivers living with HIV about their parenting responsibilities and provide the necessary scope for this subject in their consultation sessions. Physicians are in a position to draw their patients' attention to the services available to them.

Demonstration of the effectiveness of zinc in diarrhoea of children living in Switzerland.

We designed a double-blinded randomized clinical trial of zinc (10 or 20 mg of zinc sulphate for 2-5 month-old or 6-59 month-old children, respectively, during 10 days) vs. placebo in otherwise healthy children aged 2 months to 5 years who presented with acute diarrhoea (i.e. ≥3 stools/day for less than 72 h). Eighty-seven patients (median age 14 months; range 3.1-58.3) were analysed in an intention-to-treat approach. Forty-two patients took zinc and 45 placebo. There was no difference in the duration nor in the frequency of diarrhoea, but only 5% of the zinc group still had diarrhoea at 120 h of treatment compared to 20% in the placebo group (P = 0.05). Thirty-one patients (13 zinc and 18 placebo) were available for per-protocol analyses. The median (IQR) duration of diarrhoea in zinc-treated patients was 47.5 h (18.3-72) and differed significantly from the placebo group (median 76.3; IQR 52.8-137) (P = 0.03). The frequency of diarrhoea was also lower in the zinc group (P = 0.02). CONCLUSION: zinc treatment decreases the frequency and severity of diarrhoea in children aged 2 months to 5 years living in Switzerland. However, the intention-to-treat analysis reveals compliance issues that question the proper duration of treatment and the choice of optimal pharmaceutical formulation.