Performance of indirect immunofluorescence assay, immunochromatography assay and reverse transcription-polymerase chain reaction for detecting human respiratory syncytial virus in nasopharyngeal aspirate samples

Comparison of the use of indirect immunofluorescence assay (IFA), immunochromatography assay (ICA-BD) and reverse transcription-polymerase chain reaction (RT-PCR) for detecting human respiratory syncytial virus (HRSV) in 306 nasopharyngeal aspirates samples (NPA) was performed in order to assess their analytical performance. By comparing the results obtained using ICA-BD with those using IFA, we found relative indices of 85.0 percent for sensitivity and 91.2 percent for specificity, and the positive (PPV) and negative (NPV) predictive values were 85.0 percent and 91.2 percent, respectively. The relative indices for sensitivity and specificity as well as the PPV and NPV for RT-PCR were 98.0 percent, 89.0 percent, 84.0 percent and 99.0 percent, respectively, when compared to the results of IFA. In addition, comparison of the results of ICA-BD and those of RT-PCR yielded relative indices of 79.5 percent for sensitivity and 95.4 percent for specificity, as well as PPV and NPV of 92.9 percent and 86.0 percent, respectively. Although RT-PCR has shown the best performance, the substantial agreement between the ICA-BD and IFA results suggests that ICA-BD, also in addition to being a rapid and facile assay, could be suitable as an alternative diagnostic screening for HRSV infection in children.

Seroprevalence of human parvovirus B19 in a suburban population in São Paulo, Brazil

OBJETIVO: Analisar a prevalência de anticorpos IgG ao parvovírus humano B19. MÉTODOS: Estudo transversal em uma comunidade de subúrbio de São Paulo, Brasil, de novembro 1990 a janeiro de 1991. Amostras aleatórias (N=435) e representativas de soro foram coletadas de crianças sadias a partir de 15 dias de idade e de adultos com até 40 anos. Os anticorpos IgG ao parvovírus humano B19 foram detectados pelo teste ELISA. RESULTADOS: A prevalência de anticorpos IgG ao parvovírus B19 foi de 87 por cento dos recém-nascidos. A prevalência de anticorpos IgG de origem materna decaiu exponencialmente até o 19o mês de idade. Baixa prevalência de anticorpos foi observada nos primeiros quatro anos de vida, aumentando até 72 por cento no grupo etário de 31-40 anos. A idade média de aquisição da primeira infecção nesta comunidade é de 21 ± 7 anos. A idade ótima para se vacinar as crianças desta comunidade com uma vacina hipotética é de um ano de idade. CONCLUSÕES: A prevalência de anticorpos IgG ao parvovírus B19 foi alta entre recém-nascidos e no grupo etário 31-40 anos. A análise por estrutura etária mostrou padrão similar aos estudos prévios relacionados à baixa prevalência de infecção em crianças que aumenta com a idade.

Construction of a recombinant plasmid pSH-G containing the rabies-virus glycoprotein G gene

A plasmid named pSH-G was constructed with the rabies-virus G-gene insert. This plasmid was transfected into eukaryotic BHK-21 cells and its stability tested. The presence of the pSH-G plasmid was confirmed by means of polymerase chain reaction (PCR) after each of ten cell passages, and the results were positive. The stable BHK-21/pSH-G+ clone obtained can be used in the study of rabies as well as in the production of vaccines.

Immune response to respiratory syncytial virus in young Brazilian children

We have evaluated the cellular and humoral immune response to primary respiratory syncytial virus (RSV) infection in young infants. Serum specimens from 65 patients <=12 months of age (39 males and 26 females, 28 cases <3 months and 37 cases > or = 3 months; median 3 ± 3.9 months) were tested for anti-RSV IgG and IgG subclass antibodies by EIA. Flow cytometry was used to characterize cell surface markers expressed on peripheral blood mononuclear cells (PBMC) from 29 RSV-infected children. There was a low rate of seroconversion in children <3 months of age, whose acute-phase PBMC were mostly T lymphocytes (63.0 ± 9.0 percent). In contrast, a higher rate of seroconversion was observed in children >3 months of age, with predominance of B lymphocytes (71.0 ± 17.7 percent). Stimulation of PBMC with RSV (2 x 10(5) TCID50) for 48 h did not induce a detectable increase in intracellular cytokines and only a few showed a detectable increase in RSV-specific secreted cytokines. These data suggest that age is an important factor affecting the infants' ability to develop an immune response to RSV

Detection of human parvovirus B19 in a patient with hepatitis

Parvovirus B19 has been associated by some investigators with cases of severe hepatitis. The aim of the present study was to determine the presence of active parvovirus B19 infection among 129 Brazilian patients with non-A-E hepatitis. The patients were assayed for antibodies against parvovirus B19, IgM class, by ELISA. In IgM-positive cases, parvovirus B19 DNA was assayed by PCR in serum and liver tissue and parvovirus VP1 antigen in liver tissue was assayed by immunohistochemistry. Antibodies against parvovirus B19, IgM class, were detected in 3 (2.3 percent) of 129 patients with non-A-E hepatitis. Previous surgery and blood transfusions were reported by these 3 patients. One patient was a 56-year-old female with severe hepatitis, with antimitochondrial antibody seropositivity and submassive necrosis at liver biopsy, who responded to corticosteroid therapy. Strong evidence for active parvovirus B19 infection was found in this patient, with parvovirus B19 DNA being detected by PCR in liver tissue. Furthermore, parvovirus VP1 antigen was also detected in liver tissue by immunohistochemistry. The other two IgM-positive patients were chronic hepatitis cases, but active infection was not proven, since neither viral DNA nor antigen were detected in their liver tissues. This and other reports suggest a possible relation between parvovirus B19 infection and some cases of hepatitis