Core encoding sequences of Hepatitis C virus in Ghanaian blood donors are predominantly mosaics of different genotype 2 strains and cannot distinguish subtypes

Background

Distribution of Hepatitis C virus (HCV) genotypes varies significantly worldwide. Genomic diversity between genotypes has implications for treatment, vaccine development and optimal design of HCV diagnostic assays. Molecular characterization of HCV in different geographical areas is therefore very essential for management and public health control of HCV infection. This study investigated the molecular epidemiology and characteristics of HCV genotypes in healthy individuals in Accra, Ghana.

Methods

An experimental study was carried out on blood samples obtained from voluntary blood donors. Two hundred samples were initially screened for HCV antibodies and infection was confirmed by RNA detection through RT-PCR of the 5′-untranslated region (5’UTR). The core gene sequences were analysed for HCV genotype determination by genotype-specific PCR; and then by cloning and direct sequencing followed by phylogenetic analysis. The sequences were further analysed in detail by similarity plotting.

Results

Molecular diagnosis confirmed the presence of HCV RNA in 2 out of 200 (1%) blood donors. Initial genotyping by genotype-specific PCR identified all two infections as subtypes 2a and 2b of genotype 2. Extensive evolutionary and genetic analyses indicated two epidemiological profiles. First, phylogenetic tree topologies clearly showed that, collectively, the core sequences of the Ghanaian HCV isolates belong to a single, distinct genetic group within HCV genotype 2 cluster, with high genetic similarity and rapid sequence variation in a single individual. Second, the sequences are mosaics comprising 2e and other genotype 2 subtype fragments. The analyses underscore a unique and complex HCV genotype 2 core sequence profile of the Ghanaian isolates.

Conclusions

Analysis of HCV core encoding sequences from Ghanaian blood donors in Accra confirmed predominance of genotype 2 HCV among healthy individuals. However, the isolates could not be classified into subtypes, possibly due to their complex sequence pattern that might suggest high mutability of the prevailing genotype. The core region of Ghanaian HCV therefore may not be suitable for distinguishing subtypes. These findings extend those from previous studies and thus underscore the need to search for subtype-informative region of Ghanaian HCV to elucidate the genetic diversity and factors determining outcome of HCV infections in Ghana.

Validation of an immunoblot assay employing an objective reading system and used as a confirmatory test in equine infectious anaemia surveillance programs

Equine infectious anaemia (EIA) is a blood borne disease that is listed among the notifiable diseases of the World Organisation for Animal Health (OIE). EIA is also regulated by the OIE for the international trading provisions and is generally subject to control programmes. Since 2011, Italy has been conducting a surveillance plan based on a three-tier diagnostic system, using a serological ELISA as screening test, an agar gel immunodiffusion test (AGIDT) as a confirmatory method, and an immunoblot (IB) as an alternative confirmatory assay for discordant results between the first two tests. As for the in-house competitive ELISA (c-ELISA) and the AGIDT, the Italian National Reference Laboratory for EIA (NRL) validated the IB according to the OIE guidelines, employing eight panels containing positive sera, including those from EIA virus (EIAV) proven infected horses, and negative horse, mule and donkey sera collected from different geographical areas. In addition, two international reference image panels were employed for the optimization and the validation of the digital image reading system adopted that allows an impartial measurement of the serum reactivity in the IB assay. The immunological reactivity to EIAV antigens, p26, gp45 and gp90 adsorbed on the IB membrane, determines the serological status of the animal and for EIA, a p26 positive band together with at least one of the other antigen defines a subject as serologically positive for EIAV. For validation, the parameters assessed were threshold values, analytical and diagnostic sensitivity and specificity, repeatability and reproducibility. These parameters were evaluated for each antigen as well as in combination, according to the diagnostic algorithm established above. The validation data defined the IB as having a satisfactory sensitivity, specificity, repeatability and reproducibility for all antigens and species tested. An instrumental recording of the results improves the confidence in using IB as a confirmatory test for EIAV, differently from the AGIDT that is read by an operator. The advantages of using the IB are its higher sensitivity, to that of the AGIDT, which allows an earlier detection of infection that reduces the risk of transmission and therefore the incidence of the EIA, and its higher specificity to that of the ELISA which is based on the discrimination of subjects reacting only against the p26, the antigen used by all ELISAs available, which are not considered as infected by EIAV. In particular, when this assay is used in outbreaks it can detect new cases earlier than the AGIDT, and therefore reduce the restriction period with an economic benefit for the animal owners and the public veterinary sanitary system.

[Hepatitis C virus screening: performances characteristics of a commercial automated chemiluminescent microparticle immunoassay (CMIA-ARCHITECT anti-HCV)]

OBJECTIVES

In spite of improvement of the third-generation enzyme immunoassay (EIA) for screening HCV antibodies, some non-specific reactions persist. With commercialisation of a new chemiluminescence microparticle immunoassay (CMIA), we assessed the specificity of 2 assays providing by Abbott Diagnostics: CMIA-ARCHITECT anti-HCV and MEIA-AxSYM HCV 3.0 for qualitative detection of HCV antibodies in serum sample of patients collected in CHU of Caen.

PATIENTS AND METHODS

Anti-HCV results of 9753 serum samples tested by MEIA-AxSYM V.3 (2004), 6135 tested by CMIA-ARCHITECT1 (April to December 2005) and 5598 tested by CMIA-ARCHITECT2 (February to August 2006) were retrospectively analysed. Prevalences were calculated according to S/C ratio. The serum samples with an average S/C ratio from 1 to 2 for CMIA-ARCHITECT2 were confirmed with an immunoblot assay (Chiron RIBA HCV 3.0 SIA).

RESULTS

The CMIA-ARCHITECT assays showed a strong discrimination between negative and positive samples. We observed a tiny distribution of negative results. The percentage of "low positive" was respectively 1.26% for the MEIA-AxSYM, 0.68% for the CMIA-ARCHITECT1 and 0.36% for the CMIA-ARCHITECT2. Thirty-three of 54 (61%) samples yielding S/C ratio between 1 and 2 in the initial screening analysis with the CMIA-ARCHITECT1 were tested negative with CMIA-ARCHITECT2. Among the 21 remaining, 62% of RIBA results were interpretable.

CONCLUSION

CMIA-ARCHITECT assays improve the anti-HCV screening with a decrease of low-positive reactivity. However, low-positive results persist for which it is difficult to distinguish false-positive from low titer of antibodies. Supplemental assays such as immunoblot can be recommended in particularly context to more improve specificity and HCV-RNA detection should exclude a seroconversion.

Comparative yield of HCV RNA testing in blood donors screened by 2.0 versus 3.0 antibody assays

BACKGROUND

Two HCV antibody tests (EIA 2.0 [EIA2], Abbott; and the Version 3.0 ELISA [EIA3], Ortho) are currently licensed for screening of US blood donors. Testing of donors for HCV RNA allows comparison of the sensitivities of the two antibody-screening assays.

STUDY DESIGN AND METHODS

All allogeneic blood donations at 13 US test sites were screened for HCV RNA by testing plasma minipools using an investigational assay (COBAS AmpliScreen HCV test, v2.0, Roche Molecular Systems). Some sites screened for HCV antibody by EIA2 and some used EIA3. The frequency of RNA-positive and antibody-negative (RNA-pos and Ab-neg) donations among donors screened by each antibody assay was compared. Antibody appearance was assessed in a donor follow-up study.

RESULTS

A total of 5.51 x 10(6) donations were screened for HCV RNA. Of these, 2.27 million were screened for antibody by EIA2, and 3.24 million by EIA3. Twenty-three donations were HCV RNA-pos and Ab-neg. The frequency of RNA-pos and Ab-neg donations was higher among donations screened by EIA2 (1 in 134,000), compared to those screened by EIA3 (1 in 540,000) (p = 0.001). Of the 17 RNA-pos and Ab-neg donations identified by test sites that used EIA2, 14 were retested by EIA3 and 10 (71%) were reactive. Most RNA-pos and Ab-neg donors appear to be in the process of seroconversion. Donors that were initially EIA2-negative and EIA3-reactive showed a more prolonged pattern of seroconversion compared to those that were initially nonreactive by both antibody assays. Four donors were EIA2-negative, EIA3-reactive, and RIBA-indeterminate (c33c) for at least 90 days, 1 for more than 317 days.

CONCLUSION

EIA3 would have detected the majority of RNA-positive donations missed by EIA2. Some RNA-positive donors are EIA2-negative and EIA3-reactive for a prolonged period of time.

Anti-HCV confirmatory testing of voluntary blood donors: comparison of the sensitivity of two immunoblot assays

BACKGROUND

In this study, the sensitivity of two commercially available anti-HCV immunoblot assays (HCV Western blot (Wellcozyme] and RIBA 3.0 SIA [RIBA-3, Chiron]) was compared in a voluntary blood donor population.

STUDY DESIGN AND METHODS

Four groups of donor samples were retrospectively tested in this study. Groups 1 and 2 were donor samples that gave positive or indeterminate band patterns, respectively, when originally tested on the HCV Western blot between 1994 and 1998. These samples were tested on the RIBA 3.0. Donor samples in Groups 3 and 4 were originally tested on RIBA-3 during 1998 and 1999 and gave positive or indeterminate blot results, respectively. In this study these two groups were tested on the HCV Western blot. Samples with discrepant results on the two immunoblot assays were selected for genotyping or serotyping.

RESULTS

The two immunoblots showed similar sensitivity to the core and NS5 proteins. However, of 35 samples positive on Western blot or RIBA-3, the Western blot failed to detect NS4 in 14 samples compared with only 5 for RIBA-3. As well, the Western blot failed to detect NS3 in 6 samples compared to 2 for RIBA-3. Five (27.8%) of 18 samples that were Western blot indeterminate due to core reactivity showed an additional NS3 band on RIBA-3. Of the samples with additional NS3 and/or NS4 reactivity on RIBA-3 that were genotyped or serotyped, all were HCV type 3.

CONCLUSIONS

Western blot and RIBA-3 showed similar sensitivity to the HCV core and NS5 proteins. However, RIBA-3 showed greater sensitivity to both NS3 and NS4 compared to the Western blot. The reduced sensitivity of the Western blot to the NS3 and NS4 proteins was observed with HCV type 3 samples.

HCV RNA in blood donors with isolated reactivities by third-generation RIBA

BACKGROUND

The objective of this collaborative study was to learn the proportion of HCV RNA-positive samples obtained from a population of donors with isolated anti-HCV reactivities by third-generation RIBA (RIBA-3) (indeterminate results).

STUDY DESIGN AND METHODS

During a 2-year period, 11 blood transfusion centers kept all samples with indeterminate RIBA-3 results to test them by PCR, using both local and commercial techniques.

RESULTS

Of the 758 RIBA-3 indeterminate samples, 10 (1.3%) were positive for HCV RNA: 3. 3 percent (6/180) and 1.3 percent (4/317) of samples with anti-core or anti-NS3 reactivity, respectively, and none of the 52 and 209 samples with anti-NS4 or anti-NS5 reactivity, respectively. HCV RNA-positive donors with anti-core reactivity were infected with different subtypes (1 with HCV subtype 1b, 1 with 2, 1 with 2a/2c, 2 with 3a, and 1 with 5a), and a follow-up indicated a chronic-carrier state in two of the six donors. Acute hepatitis was diagnosed in three of the four donors with anti-NS3 reactivity alone. Two of these three were IV drug users and were infected with subtype 1a.

CONCLUSION

HCV RNA-positive donors with indeterminate results in RIBA-3 are extremely rare, but they do exist. They were observed only when either anti-core or anti-NS3 was present. With such a RIBA-3 profile, PCR testing remains necessary to reveal an eventual acute or chronic HCV infection.