EFFECT OF HUMAN NEWBORN BCG IMMUNIZATION ON MONOCYTE VIABILITY AND FUNCTION AT 3 MONTHS OF AGE

SETTING: Immune response induced by BCG vaccination seems to reflect t he development of T-cell immunity and monocyte activation. Participant s were recruited from a large prospective study in infants from a subu rb in Santiago, Chile. OBJECTIVE: To determine whether newborn BCG imm unization changes the innate ability of cultured monocyte-macrophages to ingest and kill virulent mycobacteria in the absence of lymphocytes . DESIGN: The study population consisted of 15 three-month-old, tuberc ulin-positive infants immunized with BCG (Japanese) at birth, 13 rando mly-selected, age-matched tuberculin-nonreactive infants in whom BCG i mmunization was postponed until one year of age, and five BCG-immunize d, tuberculin-reactive adults. Adherent cells were cultured for 48 h. Monocyte-macrophage viability and number and viability of intracellula r Mycobacterium tuberculosis bacilli were assessed after an additional 2 h and 4 and 7 days of incubation. RESULTS: There was no difference in the mean number of adherent cells present after 48 h among the thre e study groups. Adherent cells from BCG-immunized infants and adults h ad a significantly higher viability after 7 days in culture than adher ent cells from non-immunized infants. The percentage of cells ingestin g h?. tuberculosis and the number of bacilli per cell after 2 h and 4 days was significantly higher in immunized infants and adults than in non-immunized infants. However, there was no evidence for increased ki lling of mycobacteria by cells from immunized infants and adults. CONC LUSION: These results suggest that BCG vaccination increases monocyte viability and the uptake of M. tuberculosis without enhancing the abil ity to kill ingested M. tuberculosis in the absence of lymphocytes.