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Perfil de produção de anticorpos após vacinação para hepatite B em doadores sanguíneos positivos para antiHBc e negativos para HBsAg e anti-HBs

by de Ribeiro, Paula Machado

Abstract (Summary)
Antibody to hepatitis B core antigen (anti-HBc) is considered a sensitive and specific serum marker of hepatitis B vírus (HBV) infection. Anti-HBc can be found in serum samples from persons who have been exposed to HBV. Infrequently, anti-HBc is detected in the absence of either hepatitis B surface antigen (HBsAg) or antibody to hepatitis B surface antigen (anti- HBs). The significance of finding anti-HBc as the sole marker of HBV infection remains uncertain. There are five possible explanations for this finding. First, could be due to falsepositive results of the tests. Second, the loss of anti-HBs with time after resolution of HBV infection. Third, absence of HBsAg or indetectable HBsAg in individuals carriers of HBV.Fourth, the ?window phase? when HBsAg has disapperead before anti-HBs becomes detectable. Finally, a passive transfer of anti-HBc is possible. It is very important to healthservices and patients distinguish whether isolated anti-HBc is related to false-positive results or to a prior exposure to HBV resolved or not. Almost always in a previous exposure to HBV a single injection of HBV vaccine always leads to an anamnestic anti-HBs response (anti-HBs titer exceeding 50 IU/l after 30 days after the first vaccination), providing evidence against chronic infection and enhancing protective immunity. For the false-positive results situation it?s expected a primary anti-HBs response (anti-HBs titers exceeding 10 IU/l after the third vaccination).The aim of this study was to evaluate the response to hepatitis B recombinant vaccine in blood donors positive for anti-HBc but negative for HBsAg and anti-HBs in Recife. It was a quasi- experimental study without control group. Twenty-four blood donors with an age range of 22-76 years recieved three 20 mcg doses of Engerix-B® at 0, 1 and 6 months. Sera from each subject were obtained and tested for anti-HBs, after first and third vaccination, by ezyme-linked fluorescent immunoassay (commercial kit VIDAS®). After the first and third vaccinations, the anti-HBs titers exceeding or equal to 10 IU/ l (seroprotection) was 61,9% and 87,5%, respectively. This study observed anamnestic response as 38% and the primary response was found as 47,6%. This study found frequencies comparable with some others regions of the world. There was no anti-HBs response in three (12,5%) subjects. HBV DNA determination by PCR analysis was done in those who did not responded after vaccination but anyone was positive. In conclusion, this study using HBV vaccination was useful to detect false positive results (primary response) or past infection by HBV (anamnestic response) in our blood donors. For whom no specific follow-up is required. This strategy is the most practical approuch to clarify the meaning of isolated anti-HBc in most of blood donors
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Luiz Cláudio de Arraes Alencar

School:Universidade Federal de Pernambuco

School Location:Brazil

Source Type:Master's Thesis

Keywords:Isolated anti-HBc Hepatitis B HBV Marcadoressorológicos HBV-DNA Serological markers vaccine

ISBN:

Date of Publication:10/27/2005

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