Erythema infectiosum, or fifth disease, has long been recognized as a common communicable disease of childhood. Since the identification of human parvovirus B19 (B19) in 1975, there has been increasing recognition of the spectrum of disease that can result from infection. Disease caused by B19 can vary depending on host factors. Infection in a normal host can be asymptomatic, manifest by a characteristic rash, or present with arthropathy. Primary infection during pregnancy can result in hydrops fetalis caused by fetal anemia. In an immunocompromised host infection may be prolonged and can present as chronic anemia without other features. Patients with sickle cell disease or other disorders of red blood cells may develop aplastic crisis during B19 infection. With the development of PCR for the detection of B19, the role of B19 in central nervous system infection is increasingly recognized. Case report. A 21/2-year-old girl presented in May, 1993, with pancytopenia and was diagnosed with acute lymphoblastic leukemia (low risk). Chemotherapy was given using the Australia and New Zealand Children's Cancer Study Group Study VI protocol. Treatment included vincristine, daunorubicin, L-asparaginase, prednisolone, cyclophosphamide, cytosine arabinoside, intrathecal methotrexate, mercaptopurine and oral methotrexate. Twenty months after diagnosis while receiving interval chemotherapy the child was admitted to hospital with a 2-week history of intermittent spiking fever and headache. She had been assessed by her general practitioner and treated with oral amoxicillin-clavulanic acid for a cough. Admission examination revealed a fever of 39°C with no apparent focus. A full blood count showed hemoglobin of 100 g/l, platelets of 92 × 109/l and a white blood cell count of 1.6 × 109/l (neutrophils 55% and lymphocytes 41%). Urinalysis and biochemistry were normal. Ceftazidime was given intravenously. After admission fevers persisted to 39.5°C, as did the headache. The child had two brief seizures associated with high fever; there was no past or family history of febrile seizures. There was progressive decline of the hemoglobin, platelets and white blood cell count. Examination remained normal with no meningism or neurologic abnormality. Results of a lumbar puncture on Hospital Day 3 are shown in Table 1. Cerebrospinal fluid (CSF) was cultured for bacteria and viruses, and antibiotic therapy was changed to intravenous cefotaxime. A computerized tomography head scan was normal.TABLE 1: CSF and PCR results Numerous investigations were negative, including CSF for Cryptococcus antigen and for Mycobacterium tuberculosis by culture and PCR. Studies for Toxoplasma (serology and PCR) were negative, as was cytomegalovirus PCR. Serology for Epstein-Barr virus was consistent with previous infection. Chest and sinus radiograms were normal. On Hospital Day 8 amphotericin B was commenced; cefotaxime was continued. Over Hospital Days 12 to 14 the headache and fever resolved. Amphotericin B and cefotaxime were stopped, and the child was discharged home on Day 16 with a diagnosis of a viral illness with meningitis. During the following week there was ongoing bone marrow suppression requiring interruption of oral chemotherapy. A bone marrow aspirate on Day 26 of the illness showed no evidence of leukemic relapse. A CSF obtained at the same time showed persistent abnormality. One month after hospitalization for this illness parvovirus B19 serology was positive for IgM and negative for IgG, and serum was strongly positive for B19 by PCR on the first round. Ten weeks later B19 IgM was still positive, B19 IgG was present and serum was positive for B19 by PCR, but only on the second round. Parvovirus B19 was detected in cerebrospinal fluid obtained during initial hospital admission and subsequently from repeat CSF 3 months later; CSF was negative for B19 by PCR 5 months after initial hospitalization. Six weeks after hospitalization there was spontaneous increase in hemoglobin, platelet count and white blood cell count. At no time was a rash present. The child is currently in remission, 3 years after the end of treatment. Laboratory methods.PCR. The nested PCR method was developed at the Auckland Public Hospital Virology Department. B19 recombinant plasmid DNA and positive control serum were obtained from B. Cohen (Virus Reference Laboratory, Central Public Health Laboratories, London, UK). Assay sensitivity was estimated to be ∼10 to 100 B19 genomes in a background of 1 μg of human DNA with the use of quantitated plasmid DNA. DNA was extracted from 200 μl of serum or CSF by standard methods using a sodium dodecyl sulfate lysis buffer plus proteinase K digestion, followed by phenol/chloroform extraction and ethanol precipitation. The DNA was resuspended in 50 μl of double distilled water. In the first round PCR 10 μl of DNA were used, followed by nested PCR with 2 μl of the first round product. Primer sequences were specific for the NS1 gene,1 first round amplification yielding a 446-base pair (bp) product and nested amplification yielding 235-bp internal product. PCR products were analyzed by 2% agarose gel electrophoresis followed by ethidium bromide fluorescence using UV light transillumination. Product identity was inferred from the electrophoretic comigration with amplified positive control product and the high level of specificity conferred by a nested PCR. Precautions taken to avoid false positive PCR results included separate laboratory rooms dedicated to specimen DNA preparation, PCR reagent/reaction preparation and PCR product amplification and detection. Blank control extractions accompanied all specimen DNA extractions. Further, no-DNA reactions were included in each PCR run to control for reagent contamination. Serology. Anti-B19 IgM and IgG antibodies were detected by enzyme-linked immunosorbent assay with kits obtained from MRL Diagnostics, Cypress, CA. B19 IgG reacts with B19 VP1 antigen bound to microwells. Subsequent detection was via a peroxidase-conjugated anti-human IgG antibody. IgM was similarly detected via a peroxidase-conjugated anti-human IgM (μ-chain-specific) antibody after first precipitating interfering IgG antibody. Discussion. This case clearly illustrates the atypical manifestations of B19 in an immunocompromised host, including chronic central nervous system (CNS) infection. The common signs of B19 infection in a normal host are primarily a result of the humoral immune response. A higher index of suspicion for this infection is needed in an immunocompromised host. Children undergoing chemotherapy who develop B19 infection can have a protracted period of bone marrow suppression.2-7 Intravenous gamma-globulin (IVIG) has been associated with clearance of viremia and resolution of bone marrow suppression.3 IVIG has also been used to treat B19 infection in primary immunodeficiency8, 9 and in patients with human immunodeficiency virus infection.4 Possible CNS infection in children with a clinical diagnosis of erythema infectiosum has been documented for some time.10, 11 With new techniques it has been possible to demonstrate B19 IgG and IgM12 and viral DNA by PCR13-16 in CSF. The cases of CNS infection reported to date have been in nonimmunocompromised children or adults, with associated features of bone marrow suppression and rash (Table 2).TABLE 2: Summary of reported cases of human parvovirus B19 CNS infection To our knowledge this is the first reported case of persistent CNS B19 infection. Given the lack of CSF contamination with blood, the CSF pleocytosis and the elevation in CSF protein, we believe this case represents true infection rather than falsely positive results. With the potential for treating B19 infection with IVIG infusion this case also illustrates the importance of considering B19 as a pathogen, especially in patients in whom one can predict that usual clinical features will not be present. Jan P. Sinclair, F.R.A.C.P. Margaret C. Croxson, F.R.C.P.A. Stephen M, Thomas. B.Sc. Lochie R. Teague, F.R.A.C.P., F.R.C.P.A. David C. Mauger, F.R.A.C.P. Starship Children's Hospital (JS, LT, DM) Virology Department; Auckland Public Hospital (KC, ST) Auckland, New Zealand

A 36 kd protein isolated from human T lymphocyte cell lines {MOLT-3, MOLT-4, H-9) was demonstrated to potentiate transactivation of the HIV-I promoter by the HIV-I Tat protein.This Tat associated protein (TAP) was detected in the intranuclear compartment by immunofiureseance staining of MOLT-4 cells.TAP was detected at very low levels in freshly isolated peripheral blood mononuclear cells and it's expression significantly increased after overnight culture in media containing 10% fetal calf serum.In contrast, TAP was not detected in the Chinese hamster ovary cell line or several monkey T cell lines.However, Chinese hamster ovary hybrid cells containing human chromosome 6 and 12 did express TAP.These findings are significant in view of the fact that Tat is required for HIV-I replication, that HIV-I does not infect primates, and that HIV infectivity of activated T lymphocytes is greater than that of resting T lymphocytes.In addition, the intranuclear localization of TAP implies a transcriptional role for the protein.Lastly, the data suggest that the protein or cofactors necessary for TAP activity are encoded by chromosome 6 or 12.