Three cases of simultaneous seroconversion to hepatitis C virus (HCV) in a hemodialysis unit initiated the investigation of the viral strains of 14 seropositive patients in the unit by nucleotide sequencing. The results showed that five patients had been infected with the same viral strain, and indicated that two other patients were sharing a second strain. Transmission was not related to blood transfusions and not associated with the dialysis machines, but occurred between patients treated on the same shift. The number of cases was higher than expected from the serological data. Thus, spread of virus may occur at high frequencies in environments where parenteral routes are made accessible, in spite of rigorous preventive measures. This may raise concern that non-transfusion associated spread of HCV may be present and unnoticed in several hospital settings.

ABSTRACT. Objective. To evaluate viral vaccination immunity and booster responses in children treated successfully for acute lymphoblastic leukemia by chemotherapy and to study the response to treatment of antibody-producing plasma cells that are important for persistence of humoral immunity.Methods. Forty-three children who were in continuous first remission for a median of 5 years (range: 2-12 years) were studied. Before the leukemia was diagnosed, all children had been immunized against measles, mumps, and rubella according to the Swedish National immunization program. We analyzed levels of serum antibodies against measles and rubella by enzyme immunoassays. Avidity tests for measles antibodies were concomitantly performed by enzyme-linked immunosorbent assay for measles virus immunoglobulin G detection. The proportion of plasma cells in bone marrow was studied by flow cytometry at different times during treatment and follow-up. Children who lacked protective levels of antibodies to vaccination antigens were reimmunized. Serum was collected 3 months after immunization to assess vaccination responses.Results. After completion of the treatment, only 26 of the 43 children (60%) were found to be immune against measles and 31 (72%) against rubella. The proportion of bone marrow plasma cells decreased during treatment but returned to normal after 6 months. Revaccination caused both primary and secondary immune responses. Six of the 14 children without immunity failed to achieve protective levels of specific antibodies against measles and 3 against rubella.Conclusions. Our finding of loss of antibodies against measles and rubella in children treated with intensive chemotherapy suggests that reimmunization of these patients is necessary after completion of the treatment. To determine reimmunization schedules for children treated with chemotherapy, vaccination responses need to be studied further. A n increasing number of children survive leukemia as a result of improved and more intense chemotherapy. Other factors that influence outcome are improved supportive care including platelet transfusions, treatment with growth factors such as granulocyte colony-stimulating factor, and prophylactic antibiotic treatment. 1,2 Few studies have focused on potential long-term immunologic consequences of chemotherapy in survivors of childhood leukemia. Short-term (Ͻ2 years) effects of chemotherapy on immune function have previously been documented in children who were treated for malignancies, including acute lymphoblastic leukemia (ALL). 3,4 In those children, severe Band T-cell depletion results in clinical complications related to immune incompetence, 5,6 although the total B-and T-cell counts resolve quantitatively 6 months to 1 year after cessation of therapy. [7][8][9][10] In earlier studies, children who were treated with chemotherapy had lower levels of antibodies against common viral vaccination antigens such as measles, mumps, rubella, and polio. 11 The clinical implications, if any, of this finding are not completely und...

Acute respiratory tract infections are caused by a large number of viruses. Diagnostic methods have until recently been available only for a limited number of these viruses. With the objective to achieve sensitive assays for all respiratory viruses, a rational workflow in the laboratory, and a short turn-around time, a real-time PCR diagnostic platform for daily rapid detection of 15 respiratory viruses was developed. The system was evaluated on 585 stored nasopharyngeal aspirates from hospitalized children. Previous analysis by immunofluorescence and virus isolation identified viruses in 37% of the samples while the new PCR diagnostic panel detected 57% virus positive samples. The new platform was introduced in the laboratory in October 2007 and has then fully replaced the standard immunofluorescence assay for rapid detection of viruses and virus isolation.

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The antibody response to the envelope proteins of hepatitis C virus (HCV) may play an important role in controlling the infection. To allow molecular analyses of protective antibodies, we isolated human monoclonal antibodies to the E2 envelope glycoprotein of HCV from a combinatorial Fab library established from bone marrow of a chronically HCV-infected patient. Anti-E2 reactive clones were selected using recombinant E2 protein. The bone marrow donor carried HCV genotype 2b, and E2 used for selection was of genotype 1a. The antibody clones were expressed as Fab fragments in E. coli, and as Fab fragments and IgG1 in CHO cells. Seven different antibody clones were characterized, and shown to have high affinity for E2, genotype 1a. Three clones also had high affinity for E2 of genotype 1b. They all bind to conformation-dependent epitopes. Five clones compete for the same or overlapping binding sites, while two bind to one or two other epitopes of E2. Four clones corresponding to the different epitopes were tested as purified IgG1 for blocking the CD81-E2 interaction in vitro ; all four were positive at 0n3-0n5 µg/ml. Thus, the present results suggest the existence of at least two conserved epitopes in E2 that mediate inhibition of the E2-CD81 interaction, of which one appeared immunodominant in this donor.

The incidence of norovirus-associated gastroenteritis and the molecular epidemiology of norovirus strains were studied during three seasons (2000-2001, 2001-2002, and 2002-2003) among patients of all ages, mainly from the Stockholm region in Sweden. A total of 3,252 fecal samples were analyzed by reverse transcription-PCR. The incidences of norovirus infection among adults were 23, 26, and 30% during the three seasons studied and 18, 11, and 15% among children 0 to 15 years of age. During the first season, all norovirus strains detected by PCR were typed either by reverse line blot hybridization or nucleotide sequence analysis. During the two successive seasons, a total of 60 norovirus-positive strains from the beginning, peak, and end of the seasons were selected for nucleotide sequence analysis. We identified two dominant norovirus variants over the seasons: a new norovirus variant, recently described as the GGIIb genetic cluster, dominated among children during the first season, and during the following two seasons, a GGII-4 variant dominated. Our data suggest that norovirus infections are common, not only among adults, but also among children, and that some strains may predominantly affect children.

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Enteric viruses play an important role in pediatric diarrhea during the winter season in China. A combination of microscopic examination of stool samples with specific EIA assays to detect virus antigen in stool specimens may be suitable for routine diagnostics.