RESUMO
The detection of neutralizing antibodies against vaccinia virus is a valuable tool for the investigation of previous smallpox vaccination. Compulsory smallpox vaccination ended in Brazil during the early 1970s, although the vaccine was available until the late 1970s. The threat of smallpox as a biological weapon has called the attention of public health authorities to the need for an evaluation of the immune status of the population. Based on our previous experience with a micro plaque reduction neutralization test (PRNT) for the evaluation of yellow fever immunity, a similar test was developed for the detection and quantification of vaccinia neutralizing antibodies. A cross-sectional study to test the repeatability and validity of plaque reduction neutralization test (PRNT) for vaccinia antibodies was performed in 182 subjects divided into two categories: subjects above 31 years old and the other > or = 35 years old. Cases were subjects considered to have been vaccinated with vaccinia virus if they declared vaccination history or evidenced vaccination marks. The assay is carried out in 96-well plates, provides results within 30 h, is easily performed, has good sensitivity (92.7%) and specificity (90.8), excellent repeatability (ICC 0.89 (0.88; 0.92)) and is thus suitable for use in mass screening of a population's antibody levels.
Assuntos
Anticorpos Antivirais/análise , Vaccinia virus/imunologia , Vacínia/imunologia , Vacínia/virologia , Adolescente , Adulto , Idoso , Animais , Anticorpos Antivirais/biossíntese , Linhagem Celular , Criança , Chlorocebus aethiops , Estudos Transversais , Humanos , Pessoa de Meia-Idade , Testes de Neutralização/métodos , Testes de Neutralização/normas , Reprodutibilidade dos Testes , Vacina Antivariólica/imunologia , Vacínia/diagnóstico , Vaccinia virus/crescimento & desenvolvimento , Ensaio de Placa Viral/normasRESUMO
The vaccinia virus F11L gene product was identified during search for additional factors involved in the control of post-replicative viral gene transcription elongation. F11L is a 1065 base pairs (354 aminoacids) gene expressed early during infection with no attributed function. The F11L gene is conserved in many but not all poxviruses. The essential presence of the F11L gene was tested using two different genetic methods. F11L gene disruption by insertion of a selectable cassette containing the Escherichia coli guanine phosphoribosyl transferase gene driven by the viral early-late 7.5K transcriptional promoter resulted exclusively in recombinant viruses containing both the wild type and disrupted alleles, indicating that the F11L gene was essential. However, an alternative test, using transient dominant selection to insert nonsense mutations into the F11L gene, proved that the F11L gene was non-essential for growth in culture. These experiments suggest that misleading results can be obtained using gene insertional mutagenesis as a test of essential presence of the gene. The experiments also provide genetic data on the probability of co-insertion of linked mutations in vaccinia virus genome using transient dominant selection.