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195 Hepatitis C Virus-Specific Immune Response Among Egyptian Healthcare Workers at High Risk of Infection Without Viremia or Seroconversion*

Abdelwahab, S1,2; Rewisha, Eman3; Sobhy, Maha2; Galal, Iman2; Zakaria, Zainab A2; Mahmoud, Mohamed A3; Capone, Stefania4; Folgori, Antonella4; Hashem, Mohamed5; El-Kamary, Samer S5; Strickland, G Thomas5; Cortese, Riccardo4; Nicosia, Alfredo4

JAIDS Journal of Acquired Immune Deficiency Syndromes: April 2011 - Volume 56 - Issue - p 82
doi: 10.1097/01.qai.0000397377.46814.19

1Department of Microbiology and Immunology, Faculty of Medicine, Minia University, Minia, Egypt; 2Egyptian Company for Blood Transfusion Services (Egyblood)/VACSERA, Agouza, Giza, Egypt; 3National Liver Institute, Menoufia University, Menoufia, Egyp t4Okairòs, Via dei Castelli Romani 22, 00040 Pomezia, Rome, Italy; and 5International Health Division, University of Maryland School of Medicine, Baltimore, Maryland, USA

*Supported by FP6 Contract # 0374435 to the HEPACIVAC Consortium Hepatitis C Virus (HCV)-specific cell-mediated immunity (CMI) occurs in exposed individuals e.g. IV drug users without detecting viremia or seroconversion. We investigated the HCV-specific CMI response in seronegative, aviremic healthcare workers (HCWs) at the National Liver Institute (NLI), who are at high risk of HCV infection since more than 70% of their patients are HCV-infected. We quantified the CMI responses in 24 Egyptian HCWs with a recent history of a needle stick injury and who remained seronegative and aviremic for at least four months. An enzyme-linked immuno-spot (ELISPOT) assay was used to quantify interferon gamma (IFN-γ) production in response to 7 HCV genotype 4a overlapping 15mer peptide pools and phenotyped the responding cells by flow cytometry. A positive HCV-specific IFN-γ response (>55 spot forming cells; SFC/million PBMC) was elicited for 2-6 HCV peptide pools in 11 (46%) of the HCW while 13 (54%) subjects responded to one or none of the pools tested with a total mean of 1308 (SEM ±384) and 78 (±21) IFNγ SFC, respectively (p=0.002). CD4 T cells were the main source of IFN-γ as determined by flow cytometry. In summary, the majority of HCW demonstrated HCV-specific T cell responses for multiple HCV peptides without detectable HCV antibodies or RNA suggesting that clearance of low levels of HCV exposures occurs much more frequently than is generally appreciated and supports the concept that an appropriate immunologic stimulus could markedly improve protective immunity. Taken together, these data support the notion that a protective HCV vaccine is feasible.

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