CORRELATION BETWEEN THE ANTIBODY RESPONSE TOWARD SPECIFIC HCV PROTEINS AND HCV VIRAL LOAD

Abstract

Background: Hepatitis C virus (HCV) is an RNA virus causing acute or chronic infection and affecting more than 2% of population worldwide. The firstline tests for diagnosis of HCV infection are 3rd or 4th generation enzyme immunoassays - ELISA and CIA. They indicate the presence of antibodies against HCV in serum. These tests are characterized by high sensitivity and specificity, but they cannot distinguish past, acute or chronic infection, and sometimes produce false positive results. Confirmatory tests, such as recombinant immunoblot-line immune assay (LIA), and quantitative PCR, are used to validate the positive antibody response. The recombinant immunoblot assay can be used to determine the specificity of antibody to HCV. The aim of the present study is to determine the correlation between the anti-HCV response in confirmatory immunoblot assay and the HCV viral load, measured by PCR.

Materials and methods: Twenty-nine anti-HCV positive sera were included in the study. Third generation ELISA assay was used for anti-HCV screening of the samples and for detection of anti-HCV antibodies against specific HCV proteins. Third generation line immunoassay INNO-LIA HCV Score, based on the principle of an enzyme immunoassay, was used as a confirmatory test. The HCV viral load was measured by quantitative PCR method – Abbott Real Time HCV (Abbott Molecular Inc., USA) with linear sensitivity range from 1.08 Log 10 IU/ml (12 [IU/ml]) to 8.00 Log 10 IU/ml (100 000 000 [IU/ml]).

Results: HCV RNA was quantified in all studied samples. Ten of 29 serum samples (34%, Group I) were HCV RNA negative. The rest of the samples were HCV RNA positive as follows: 3 serums were with minimal viral load from < 12 to 10 000 IU/ml (10%, Group II); 3 serum samples –between 10 000 and 100 000 IU/ml (10%, Group III); 10 serum samples – between 100 000 and 1 000 000 IU/ml (34%, Group IV) and in 3 serum samples HCV RNA concentration was over 1 000 000 IU/ml (10%, Group V).

Conclusion: HCV screening strategies involving anti-HCV detection by ELISA combined with recombinant immunoblot assay can be the method of choice in laboratories with limited equipment and finances.