Nasopharyngeal carcinoma (NPC) in Tunisia is characterized by its bimodal age distribution involving juvenile patients of 10-24 years and adult patients of 40-60 years. Three serological techniques were compared for primary diagnosis (N = 117) and post-treatment monitoring (N = 21) of NPC patients separated in two age groups. Immunofluorescence assay (IFA) was used as the "gold standard" for detection of IgG and IgA antibodies reactive with Epstein-Barr virus (EBV) early (EA) and viral capsid (VCA) antigens. Results were compared with ELISA measuring IgG and IgA antibody reactivity to defined EBNA1, EA, and VCA antigens. Immunoblot was used to reveal the molecular diversity underlying the anti-EBV IgG and IgA antibody responses. The results indicate that young NPC patients have significantly more restricted anti-EBV IgG and IgA antibody responses with aberrant IgG VCA/EA levels in 78% compared to 91.7% in elder patients. IgA VCA/EA was detected in 50% of young patients versus 89.4% for the elder group (P < 0.001). Immunoblot revealed a reduced overall diversity of EBV antigen recognition for both IgG and IgA in young patients. A good concordance was observed between ELISA and IFA for primary NPC diagnosis with 81-91% overall agreement. Even better agreement (95-100%) was found for antibody changes during follow-up monitoring, showing declining reactivity in patients in remission and increasing reactivity in patients with persistent disease or relapse. ELISA for IgA anti-VCA-p18 and immunoblot proved most sensitive for predicting tumor relapse. VCA-p18 IgA ELISA seems suitable for routine diagnosis and early detection of NPC complication.
To evaluate the genetic variability of hepatitis A virus (HAV) isolates in Tunisia, serum samples were collected from 99 patients in different Tunisian areas in 2003 containing 92 cases with acute hepatitis, five with severe acute hepatitis and two with fulminant hepatitis. The entire VP1 gene was amplified and sequenced. Sequences were then aligned and a phylogenetic analysis was performed. Additionally, the amino acid (aa) sequence of the VP1 was determined. The analysis of Tunisian HAV isolates revealed that all the isolates were sub-genotype IA with 96.4%-99.8% of identity and showed the emergence of two novel antigenic variants. The Tun31-03 antigenic variant, with a 38 aa deletion containing Met156, Val171, Leu174 and Ala176 and located between 150 and 187 aa of the VP1 protein where neutralization escape mutations, was found. The second antigenic variant, Tun36-03, was isolated from a patient with fulminant hepatitis and presented a substitution of Thr by Pro at position 10 of the VP1 protein. This amino acid is located in a peptide presenting an antigenically reactive epitope of the VP1 protein. This substitution has never been described previously.
Sera from 12 patients infected with human immunodeficiency virus and hepatitis B virus (HBV), on lamivudine as part of an antiretroviral therapy, were retrospectively analysed for the presence of HBV polymerase mutations by the line probe assay, INNO-LiPA HBV DR, and by the direct sequencing assay, TRUGENE™ HBV genotyping kit. Results at codons 180, 204 and 207 were compared for 44 samples. Full concordance was observed for 81.4% of the 129 analysed codons. Discordance involved only mixed populations: LiPA detected additional species in 19 codons and TRUGENE in five. Viral breakthrough occurred in seven patients, 12-33 months after lamivudine initiation. In five cases with close sampling available, both assays detected mutations before the rise in viral load, although earlier by LiPA for three patients. The time interval between the first mutant detection and viral escape ranged from 2 to 22 months. Mutations were detected in four of the five remaining patients: 1) at therapy initiation in a primary non-responder; 2) after 37 months, but replication became undetectable after tenofovir introduction; 3) transiently at 6 months by LiPA but treatment was ceased thereafter; 4) after 23 months but replication levels remained low during a 5-year follow-up. Interestingly, TRUGENE sequencing identified on late samples from three patients a variant carrying rtV173L plus rtL180M plus M204V mutations, having the in vitro characteristics of ‘vaccine escape’ mutants. Both assays appear to be valuable tools for the early detection of mutated HBV strains. The detection of genotypic resistance could improve therapeutic decision-making, although clinical or other virological factors may determine the rapidity of the viral breakthrough.
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