Association between Human Parvovirus B19 (HP B19) and Acute Lymphoblastic Leukemia in Children.

Human Parvovirus B19 (HP B19), a single stranded DNA virus, is a global and common infectious pathogen in humans. Transmission of infection occurs via the respiratory route, through blood-derived products administered parenterally or through vertical transmission. The virus has tropism for rapidly dividing erythrocyte precursors. Usually infection by Human parvovirus B19 is mild & self limiting in healthy children while in children with hemoglobinopathy or hemolytic anemia the condition may be critical causing aplastic crisis due to short life span of red blood cells. Also, immunocompromized patients may develop serious complications like myocarditis, encephalitis & hepatitis. ALL, the most common cancer occurring in children, was recently described in association with HP B19. This study investigated this association.

We compared between the presence of HP B19 DNA in CSF of 20 ALL cases at time of diagnosis before its disappearance by the developing immune system and its presence in CSF of 10 age and sex matched controls. The study showed the presence of HP B19 DNA in CSF of 4 ALL cases (20%) but in neither of the control group. It showed that cases of ALL positive for HP B19 DNA tend to be younger than ALL cases negative for HP B19 DNA. They were of common pre-B immunophenotype. They all had lower Hb, platelet and white blood cell count, this may be due to apoptotic effect of the NS1 protein of the HP B19 virus. It is important to state that the 4 ALL cases were screened for the state of their humoral immunity, the principle immune response against HP B19, and all of them had normal total IgG. Such finding may suggest that this association may surpass a mere opportunistic infection and that HP B19 may be incriminated in the pathogenesis of ALL. Further studies to prove the presence of HP B19 DNA in leukemia cells at the time of diagnosis as wellas further investigations are required on a larger scale to clarify the interaction between the HP B19 and the immune system in the hematological malignancies.