Elsevier

Journal of Clinical Virology

Volume 63, February 2015, Pages 12-17
Journal of Clinical Virology

Hepatitis B virus infection in post-vaccination South Africa: Occult HBV infection and circulating surface gene variants

https://doi.org/10.1016/j.jcv.2014.11.032Get rights and content

Highlights

  • •

    This study observed a reduction in the prevalence of OBI post-hepatitis B vaccine introduction, compared to the pre-vaccine era.

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    When considering HIV infection, the prevalence of OBI rather increased in the post-vaccine introduction population.

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    HBV surface gene sequencing detected subgenotypes A1, A2 and D4.

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    No vaccine escape mutants were observed after nearly two decades of universal hepatitis B vaccination in South Africa.

Abstract

Background and objective

The aim of this study was to investigate the prevalence of occult hepatitis B virus (HBV) infection and the HBV surface (S) gene variants circulating in the South African population after nearly two decades of universal hepatitis B vaccination.

Study design

From a previous serosurvey, 201 serum samples with serological evidence of exposure to HBV were identified and these were stratified into post- and pre-vaccine introduction populations. For all samples, HBV DNA was screened and quantified using a real-time PCR assay and results analysed together with HBV serological markers. Where HIV results were available, subset analysis was performed. The HBV S gene was PCR-amplified and sequences analysed for a total of 37 isolates.

Results

The prevalence of occult HBV infection reduced from 70.4% in the pre-vaccine introduction era to 66.0% post-vaccine introduction. There was an association between HIV infection and an increase in prevalence of occult HBV infection within the post-vaccine introduction population, although this was not statistically significant. Furthermore, sequence analysis revealed the following HBV subgenotypes; A1 (n = 34), A2 (n = 2) and a rare D4 isolate. HBV S gene variants, including diagnostic escape mutants were isolated.

Conclusion

There was a decline in the prevalence of occult HBV infection in post-vaccination South Africa, although the disease burden remains significant in the HIV co-infected population. After nearly two decades of a universal hepatitis B vaccination programme, no positive selection of vaccine escape mutants were observed.

Section snippets

Background

South Africa is hyper-endemic for hepatitis B virus (HBV) infection which is associated with fatal chronic sequelae such as liver cirrhosis, end-stage liver disease and hepatocellular carcinoma (HCC) [21], [27]. Prior to hepatitis B vaccine introduction, the burden of hepatitis B in the country was chiefly driven by the high prevalence (>10%) of childhood (<5 years) infections accounting for ∼3 million potentially fatal chronic HBV infections [19], [44].

In keeping with the World Health

Objective

The aim of this study was to examine the prevalence of OBI and investigate the HBV S gene variants circulating in a South African population post-vaccine introduction.

Study design

From a previous health facility-based hepatitis B serosurvey [2], 201 serum samples which tested positive for serological makers of exposure to HBV; HBsAg and/or antibody to HBV core antigen (anti-HBc), were identified out of a total sample size of 1206. These serologically exposed samples were the focus of this study. The serum samples were stratified by age based on the year (1995) the hepatitis B vaccine was introduced into EPI-SA, into a post-vaccine introduction population (POVP, 1–16 year

HBV S gene amplification and sequencing

For amplification of HBV DNA in the S region, a conventional nested PCR assay was performed using two sets of primer pairs (first round: S1 = 5′-CCTGCTGGTGGCTCCAGTTC-3′, S2Na = 5′-CCACCATTCK(G/T)TTGACATACTTTCCA-3′ and second round: S6Bs = 5′-GATCCGAGGACTGGGGAC-3′, S7Ps = 5′-GGTTAGGGTTTAAATGTATAC-3′) in a two-step reaction for all HBV DNA positive samples with viral loads >35.7 IU/ml (detection limit by this PCR assay). The cycling conditions used for amplification of the S gene were as outlined

Sample population

Serum samples (N = 201) were collected from various health facilities from five of the nine provinces in South Africa; Gauteng (49.8% [n = 100]), North West (40.3% [n = 81]), Mpumalanga (6.0% [n = 12]), Limpopo (3.5% [n = 7]), and the Northern Cape (0.5% [n = 1]). Of the 201 serum samples, 62 (30.8%) were classified by age into the POVP and 139 (69.2%) into the PRVP based on national introduction of the vaccine in 1995 (Table 1). The demographic background of the sample population has been described

Discussion

The distinction between the prevalence of OBI in the South African population nearly two decades post-introduction of universal hepatitis B vaccination has not been explored. A previous study conducted in children (aged 1–2 years) from the Eastern Cape province of South Africa determined that HBV DNA detection by a nested PCR assay in HBsAg negative serum samples significantly reduced from 6.5% in the unvaccinated cohort to 0.3% in those with documented proof of vaccination [16]. In the current

Funding

This work was supported by grants from the National Health Laboratory Services (NHLS) Research Trust [grant number: GRANT004_94329] and the Poliomyelitis Research Foundation (PRF) [grant number: 11/74 (MSc)].

Competing interests

None declared.

Ethical approval

Ethical clearance to conduct this study was approved by the Medunsa Research and Ethics Committee (MREC) (MREC/P/22/2012: PG).

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