الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Acute lymphoblastic leukemia accounts for 75% of all childhood leukemias. Over the last few decades, the number of children and adolescents who survive their cancer has dramatically increased, which is the result of better treatment strategies and better supportive care. However, they are at risk of potential long-term consequences of therapy.
All arms of the immune system appear to be affected in children treated for leukemia. While intensive therapy improved leukaemia survival, it also caused transitory immunodeficiency in the form of hypogammaglobulinemia, which resulted in the loss of protective antibody levels against vaccine-preventable infections supplied by previous immunization. Children could function as a reservoir for an additional spread of these viruses in the population. Immune reconstitution must be rapidly accomplished following the cessation of chemotherapy. However, it is unknown to what extent the immune system recovers after treatment.
Varicella is an acute, highly contagious viral disease. It is caused by primary infection with the varicella-zoster virus, highly transmissible via respiratory droplets or direct contact with characteristic skin lesions of the infected person. The disease is typically mild and self-limited, but it may cause significant morbidity and mortality in immunocompromised children, and severe complications may arise.
The study was conducted on two groups, each consisting of 44 children treated for acute leukemia at the Pediatric Hematology and Oncology Unit of Alexandria University Children’s Hospital. Children in group 1 were on maintenance chemotherapy and in remission ≥ 1 year, while group 2 have completed chemotherapy ≥ 6 months. The level of varicella IgG antibody was assessed by VZV IgG ELISA, it was considered positive (protective) above 0.77 u/ml.
In group 1 (patients on maintenance chemotherapy), males were slightly more represented than females (61.4% vs 38.6%). The median age at the time of the study was 6 years. Most of the studied patients were B-ALL (86.4%) while only (13.6%) were T-ALL. Only 5 (11.4%) were varicella IgG positive, while the remaining 39 (88.6%) were negative with a median IgG titer of 0.07 u/ml. In group 2 (off-therapy patients), 56.8% of patients were males versus 43.2% females. The median age at the time of the study was 10 years, and the median duration since completion of chemotherapy was 24.5 months. Most of the studied patients were B-ALL (93.2%) while only 6.8% were T-ALL. Only 9 (20.5%) were Varicella IgG positive while the remaining 35 (79.5%) were negative with a median IgG titer of 0.12u/ml. In both groups, age of diagnosis, the gender, duration of chemotherapy, type of ALL, and intensity of the treatment protocol did not significantly affect the varicella antibody titer.
Age at the time of the study and the loss of protective immunity have significant associations in all 88 patients and in both groups, where seropositivity of varicella increased with age with p=<0.001, 0.035, 0.034 respectively. This suggests that older children at the time of assessment are more likely to express protective antibody titer than younger children.