Ziad M. Shehab

ADMINISTRATION OF LIVE VARICELLA VACCINE TO CHILDREN WITH LEUKAEMIA

Live varicella vaccine was given to twenty-three children with lymphoreticular malignancies, twelve whose chemotherapy was complete and eleven who were still receiving therapy. Seroconversion was observed in all twenty-three children, only one of whom lost his vaccine-induced antibody. Eight of the children experienced thirteen exposures to varicella, including four continuing exposures in their households. Varicella, manifested by the appearance of seven vesicular lesions, developed in only one. In all but two of the children an invitro blastogenic response to varicella/zoster-virus (VZV) antigen developed; both children had a biphasic rash after immunisation. A sibling of one of these children seroconverted without clinical evidence of varicella, presumably because of infection with vaccine virus. None of the other household contacts had significant rises in VZV antibody. VZV was not isolated from the blood, throat, or urine samples of the twenty-three vaccinees tested.

1161 CHLAMYDIA-ASSOCIATED LOWER RESPIRATORY TRACT INFECTIONS (LRI) IN CHILDREN OVER 1 YEAR OF AGE

Chlamydia trachomatis (Ct) is believed to be a cause of LRIs mainly in young infants. Close surveillance for LRIs was maintained since birth on a group of 1182 children. Over a period of 17 months, we obtained nasopharyngeal and throat swabs for acute LRI from 340 children. All specimens were cultured for viruses, Ct and Mycoplasma pneumoniae. One or more of these agents were isolated from 67% of LRIs. Ct was isolated from 3/52 (5.8%) of infants ≤6 months of age, 0/61 (0%) infants 7-12 months and 9/227 (4.0%) children 1-3 years with LRI. Infection with Ct in these 9 older children (ages 17-34 mos, med=21 mos) occured from December to April and was associated with a variety of syndromes and with concurrent isolation of other pathogens.Symptoms and signs included cough (9), rhinitis (8), fever (3), abnormal bronchial breath sounds (3), hoarseness (2), shortness of breath (2), stridor (2) and wheezing (1).These results suggest that Ct is associated with a diversity of LRIs in children >1 year of age, and may often be present with other pathogens.(Supported by NHLBI-SCOR Grant HL-14136)

Application of pooled monoclonal antibodies for 1-hr detection of respiratory syncytial virus antigen in clinical specimens

A fluorescein isothiocyanate-conjugated pool of monoclonal antibodies (MoAb) to respiratory syncytial virus (RSV) was prospectively evaluated for its utility as a direct, 1-hr test for the diagnosis of RSV infection. Direct nasopharyngeal swab smears collected from 109 infants and children with acute respiratory illnesses were studied and compared with results obtained by indirect immunofluorescence using bovine polyclonal anti-RSV antibody on eluted cells derived from pooled nasopharyngeal and throat swab specimens (a 2.5-3 hr procedure), and culture. The MoAb-direct smear method was at least 86%-89% sensitive and 95%-100% specific compared with either of the other procedures. Additional prospective evaluations, as well as retrospective studies on a selected bank of slides stored from the preceding year, established that this MoAb could also be used with confidence in testing where direct smears are not employed.

TOWARD THE ELIMINATION OF VARICELLA IN CHILDREN WITH LEUKEMIA

Varicella may produce significant illness in children with leukemia. To reduce morbidity, Varicella Vaccine (VV) was given as soon as possible following diagnosis of leukemia. Twenty-eight of 29 given VV no earlier than 1 year post diagnosis seroconverted; 1 developed mild varicella at 1 year and another at 2 years post immunization. In addition, 5 of 28 lost antibody. Only 10 of 17 children immunized earlier than 1 year post diagnosis had satisfactory responses to VV. Passive immunization was started at the time of diagnosis of leukemia to provide protection prior to the time active immunization could be successfully accomplished. VZIG produced low levels of antibody that was detectable <10-12 weeks. Patients who received transfusion of platelets, but not packed red blood cells, were found to have much higher antibody levels. Protection of children with leukemia can be achieved by giving VV one year post diagnosis. Prior to this time passive immunization, probably best accomplished with an intravenous product, could reduce morbidity from varicella in these high risk children.