Background: breast feeding accounts for up to 40% of perinatally acquired HIV infection in sub-Saharan Africa. HIV infected mothers are advised by World Health Organization (WHO) to completely avoid breast feeding only if replacement feeding is acceptable, feasible, affordable, safe and sustainable (AFASS). Methods: data were obtained from 3 Ministry of Health PMTCT programs in Central Province, Kenya. HIV positive pregnant women received AZT starting at 28 weeks + intrapartum SD-NVP if CD4>350 or TARGA if CD4<350. HIV exposed infants received AZT + NVP. Infant formula, water filters and thermos flasks were provided to women opting not to breast-feed their infants. ADN-PCR for HIV was obtained at 6 weeks of age. Results: most mothers (66-96%) opted for replacement feeding (RF). Eight hundred and eighty one infants received RF either from birth or after initial breast feeding or cow´s milk. Five hundred and fifteen infants (58%) were discharged after reaching 6 months of age; 272 (31%) were still active (<6 months). There were 59 defaulters (6.7%) and 12 relocations (1.4%). Twenty three infants died (2.6%). HIV-infected infants were more than 10 times more likely to die before 6 months of age than HIV-uninfected infants [OR 10.55 (2.51-41.5) P < 0.001]. Morbidity was low; the incidence of diarrhoea and respiratory tract infection was 15.3 and 42.4 per 100 person-years respectively. Interpretation: it is possible to support safe replacement feeding in resource-limited contexts under routine program conditions within public sector health facilities by employing a feeding methodology that is feasible for mothers and safe for infants.

Introducción: la lactancia materna es responsable de hasta un 40% de los contagios perinatales del virus de la inmunodeficiencia humana (VIH) en el África subsahariana. La OMS aconseja evitar por completo la lactancia materna solo si la lactancia artificial es aceptable, factible, asequible, segura y sostenible (AFASS). Material y métodos: se analizaron datos de tres programas del Ministerio de Salud para la prevención de la transmisión vertical (PTV) del VIH, en la Provincia Central de Kenia. Las gestantes VIH+ recibieron información y consejo sobre cómo proteger al bebé durante el embarazo, el parto y el periodo de lactancia. Se administró zidovudina (AZT) desde la vigésimo octava semana, más nevirapina -dosis única- (SD-NVP) intraparto si los linfocitos CD4 eran mayores de 350 cel/mm³, o tratamiento antirretroviral de gran actividad (TARGA) si eran menores de 350 cel/mm³. Los neonatos expuestos recibieron AZT + NVP. Se suministró lactancia artificial (LA), filtros de agua y termos a las madres que optaron por no lactar a sus hijos. Se realizó reacción en cadena de la polimerasa (PCR) para ADN-VIH-1 a las seis semanas de vida. Las madres incluidas en el programa recibían apoyo psicológico individualizado y a través de terapias de grupo. Resultados: la mayoría de las madres (66-96%) se decidieron por la LA; 881 lactantes recibieron leche artificial bien desde el nacimiento o tras un periodo inicial con lactancia materna o con leche de vaca; 515 (58%) fueron dados de alta a los seis meses de edad; 272 (31%) permanecían en el programa (niños < 6 meses) en el momento del análisis de datos. Hubo 59 (6,7%) pérdidas de seguimiento y 12 (1,4%) traslados a otros programas. Un total de 23 (2,6%) lactantes fallecieron. Los neonatos infectados por VIH tuvieron diez veces más probabilidades de morir antes de cumplir seis meses que los no infectados (odds ratio [OR]: 10,55; IC 95% [intervalo de confianza del 95%]: 2,51-41,5), p < 0,001). La morbilidad fue baja; la incidencia de diarrea y de infecciones respiratorias fue de 15,3 y de 42,4 por cada 100 personas/año, respectivamente. Conclusiones: es factible y seguro apoyar la lactancia artificial para madres seropositivas y sus bebés en entornos con escasos recursos en programas integrados en instituciones sanitarias del sector público.

The observation that murine thymocytes increase their proliferation to interleukin 1 (IL-1) in the presence of phytohemagglutinin (PHA) when pre-incubated with interleukin 2 (IL-2) allowed the introduction of a modified assay for the measurement of IL-1 or the search of thymocyte-inducing proliferative activities in biological samples. Pre-incubation of thymocytes for 24 hr with 50 u/ml IL-2, followed by washings, elicited their maximal response to IL-1 in the usual lymphocyte activating factor (LAF) assay. This suggests that sequential events lead to thymocyte activation. The responsiveness is three to five fold greater than, and the total time of assay is the same as that of the LAF assay. Interestingly, pre-incubation with IL-2 renders thymocytes more sensitive than responsive to crude monocyte conditioned media. The use of the MTT colorimetric method for the assessment of thymocyte proliferation, and of the lectin jacalin as a co-mitogen are suggested as alternatives to be used in co-stimulatory assays.

Diverse conditions for stimulating human mononuclear cells to release thymocyte costimulatory factors were tested for their contribution to the generation of supernatants high titers of these monokines. Activity titers increased with LPS concentration, reaching a plateau between 1 and 10 microng/ml. Indomethacin did not modify the monokine, but the assay for thymocyte costimulatory activity was substantially affected by inhibitory substances produced by the monocytes in the absence of indomethacin. The use of nylon wool columns to trap the cells was shown to be effective in raising cellular densities without decreasing activity titers. As result, the yield per cell could be maintained even in the absence of serum, an important step toward the goal of purifiying bioactive from crude broths.