Frequency of Hepatitis B Virus Envelope Antigen and Antibodies Among Chronic Carriers in Ibadan,Nigeria

Abstract

Hepatitis B virus (HBV) infection is a major health challenge in sub-Saharan Africa with a prevalence rate of >7%. It is an important clinical problem due to its potential adverse sequelae, including hepatocellular carcinoma. The additional challenge of its associated chronic infection makes its prevention difficult despite the widely available vaccine. Infectious chronic HBV carriers are likely to be the most common source of HBV infection in the community. This study aims to study the degree of infectiousness of HBV carriers by testing for HBV envelope antigen (HBeAg) and antibody among HBV carriers attending the gastrointestinal clinic at University College Hospital (UCH, Ibadan, Nigeria). This is a cross-sectional study among 129 consecutively recruited HBV infected individuals who gave informed consent to participate in the study. The participants of the study were recruited from clients attending the gastrointestinal clinic of UCH. The sera obtained from the participants were tested for HBsAg, HBeAg, and antibodies to HBV envelope antibodies (HBeAb) using commercially available enzyme-linked immunosorbent assay (ELISA) test kits by DIA.PRO (Diagnostic Bioprobes Srl, Milan, Italy) according to the manufacturer's instruction. Of 129 samples collected, 63 (48.8%) tested positive for HBeAg, whereas 72 (55.8%) tested positive for HBeAb (p = 0.012); HBeAg prevalence was higher in females than males and also prevalent among the age group of 31–40 years. Seventy-four (57.4%) of the participants also tested positive for both HBeAg and HBeAb, whereas 55 (42.6%) were negative for both. This study shows that there is a high level of infectiousness among HBsAg-positive individuals in Ibadan, Nigeria.

Introduction

Hepatitis B Virus (HBV) is an important public health disease globally, with >250 million people infected with the virus (23), and an annual mortality of between 500,000 and 1.2 million attributed to HBV infection (21). HBV is known to cause a spectrum of acute and chronic diseases that ranges from inactive chronic carrier status to progressive chronic hepatitis that leads to end-stage cirrhosis and primary liver cancer (22). When a chronic carrier rate is >7% in a population, it is categorized as highly prevalent or hyperendemic. HBV infection is hyperendemic in sub-Saharan Africa (SSA) with an estimate of >250,000 chronic infections. In Nigeria, the HBV infection rate could be as high as 39% in some parts of the country (2,4,6,7,16,17,19).

HBV is an enveloped DNA virus belonging to the family hepadnaviridae (8). The virus has semicircular double-stranded DNA that codes for six proteins, three of which are important markers for diagnosis, disease progression, infectiousness, and management. These markers include hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg), and HBV envelope antigen (HBeAg). HBsAg is detectable in the blood of acutely or chronically infected individuals and this marker is primarily used in the screening test for HBV infection. Antibody to HBsAg (HBsAb) is protective and denotes passive and active immunity. HBsAb is only detectable when the virus is cleared from the system. The presence of antibodies to HBcAg denotes exposure to HBV infection and detection of IgM to HBcAg can be used to differentiate chronic and acute HBV infection. HBV envelope antigen is an important marker of HBV replication. Its detection signifies high levels of HBV DNA in the blood of infected individuals (9,13) and high infectivity. Antibodies to HBV envelope antigen (HBeAb) appears when HBeAg is cleared and its presence indicates a transition to the inactive carrier state of HBV infection defined as few or no HBV DNA viral load copies

Reducing new viral hepatitis infection by 90% and deaths due to viral hepatitis by 65% by 2030 is part of the vision of the global health strategy on viral hepatitis. Identifying and treatment of individuals infected with HBV will be an important plan in achieving this target. It is essentially important to identify HBV-infected individuals who are infectious and are more likely to transmit the virus to unprotected persons for treatment. This can be done by testing all HBsAg-positive persons for HBeAg. This study is designed to identify HBV-infected persons who are infectious among people attending the gastrointestinal clinic of the University College Hospital (UCH), Ibadan, Nigeria.

Methods

Study design

This cross-sectional study was carried out at the UCH, a tertiary health institution located in Ibadan, the capital of Oyo State. Individuals attending the gastrointestinal clinic of the hospital were recruited for the study. Ethical approval was obtained from the University of Ibadan (UI)/UCH ethical committee (UI/UCH ethical committee) with the number UI/EC/18/0204.

Study area

This study was conducted in Ibadan. The city has a population of 3,552,000 by the year 2020 (12). The UCH was established in 1957 with the aim of research, training, and provision of service. It has 820 beds and receives patients from all over the country, especially southwestern Nigeria. The gastrointestinal clinic is conducted by the internal medicine department. The clinic is run two times a week. The clinic for new incoming patients is conducted once a week with an average of 28 new patients per week.

Study population

Individuals attending the gastrointestinal clinic of the UCH within the study period who has a history of HBV infection were consecutively recruited into the study. The study participants were new attendees of the clinic and are known HBsAg carriers.

Sample collection, transportation, and storage

Five milliliters of blood were drawn from each patient. Sera were separated from the blood sample after collection and immediately stored at −20°C in the freezer for hepatitis B enzyme-linked immunosorbent assay (ELISA) tests.

Analysis

The serum samples were tested for HBsAg, HBeAg, and HBeAb antibody. This was done using ELISA kits by DIA.PRO (Diagnostic Bioprobes Srl, Milan, Italy) according to the manufacturer's instruction. All the serum samples were first tested for HBsAg. Those who tested positive for HBsAg were then further tested for HBeAg and HBeAb. The optical density (OD) of the plates was read using the Emax Endpoint Microplate Reader (Molecular Devices) and results were calculated based on cutoff values, set as the mean value of three negative controls +0.12 OD according to the manufacturer's instruction. Samples with equivocal results were retested and if afterward remains equivocal were regarded as negative.

Data analysis

All data in this study were analyzed using descriptive statistics and chi square was used to determine the significance of the association. A statistical significance value of 0.05 was used.

Results

A total of 129 individuals aged 19–69 years (mean 40.25) were recruited for this study. Sixty-three (48.8%) of them were males. Table 1 describes the study population. All the individuals tested positive for HBsAg. Of the 129 individuals tested for HBeAg and HBeAb, 63 (48.8%) were positive for HBeAg, whereas 72 (55.8%) were positive for HbeAb. Of the 63 (48.8%) participants who tested positive for HBeAg, 29 were males, whereas 34 were females (Table 2). Also, 72 (55.8%) participants tested positive for HBeAb of which 23 were males and 49 females. Participants aged 31–40 years had the highest prevalence of HBeAg, whereas those between 31–40 and 41–50 years had the highest prevalence of HBeAb, which is significant. Tables 2 and 3 describes the age and gender distribution of HBeAg and HBeAb among the participants (p = 0.012). Table 4 describes HBeAg and HBeAb co-positivity and negativity among the study population. Seventy-four (54.4%) and 55 (42.6%) were positive and negative for both HBeAg and HBeAb, respectively.

Table 1.

Age and Gender Distribution of Participants

Age	Male	Female	Total
30 and below	14	17	31
31–40	24	17	41
41–50	15	15	31
51 and above	10	17	26
Total	63	66	129
Mean	40.25

Table 2.

Distribution of Hepatitis B Envelope Antigen Across Age and Gender Among the Study Population

Variables	Number tested	Number positive (%)	Number negative (%)	x²	p
Gender
Male	63	29 (46.0%)	34 (54.0%)	0.203	0.652
Female	66	34 (51.5%)	32 (38.5%)
Age group
30 and below	31	9 (29.0%)	22 (71.0%)	3.148	0.369
31–40	41	25 (61.0%)	16 (39.0%)
41–50	31	20 (64.5%)	11 (35.5%)
50 and above	26	9 (24.0%)	17 (65.0%)

Table 3.

Distribution of Antibodies To Hepatitis B Virus Envelope Antigen Across Age and Gender Among the Study Population

Variables	Number tested	Number positive (%)	Number negative (%)	x²	p
Gender
Male	63	23 (36.5%)	40 (63.5%)	0.011	0.012
Female	66	49 (74.2%)	17 (25.8%)
Age group
30 and below	31	18 (58.1%)	13 (41.9%)	1.430	0.698
31–40	41	21 (51.2%)	20 (48.8%)
41–50	31	19 (61.3%)	12 (38.7%)
51 and above	26	14 (53.9%)	12 (46.2%)

Table 4.

Frequency of Both Hepatitis B Envelope Antigen and Antibodies to Hepatitis B Virus Envelope Antigen Positivity and Negativity Among Study Population

Variables	Number tested	Number positive for both Ag/Ab (%)	Number negative for both Ag/Ab (%)
Male	63	17 (27.0%)	46 (73.0%)
Female	66	57 (86.4%)	9 (13.6%)
Total	129	74 (57.4%)	55 (42.6%)

Discussion

The burden of HBV infection in Nigeria is high with a reported prevalence of about 8.1%. Although the country has viral hepatitis prevention program that targets children especially newborns, health care workers, health care waste handlers, and blood transfusion recipients, other people who do not fall into these categories have limited information about the virus nor is there any prevention strategy in place for them. There is a need to monitor HBV-infected individuals for infectivity as part of the national HBV control program. This will aid the HBV prevention program. This study has shown that approximately two-fifths of HbsAg-positive individuals are also positive for HBeAg, which is a marker of active viral replication and transmission. This may be taken as an indication of active HBV in the Nigerian population.

This study investigates the prevalence of HBeAg and antibody among HBV-positive individuals. A positivity of 48.9% for HBeAg was observed in this study. This is higher than 17% by Taura et al. in Kano (20), 8.6% by Ijoma et al. (10) and 30% by Mbaawuaga et al. (13) but lower than 81.8% reported by Forbi et al. among HBsAg-positive individuals in north-central Nigeria. These differences may be due to the different regions of the county as it has been reported that the prevalence of HBV varies across the different regions in Nigeria (7). The high prevalence of HBeAg reported in Nigeria reflects a pool of individuals who are highly infectious and serve to sustain viral transmission and evolution in the Nigerian population, which could drive the future burden of liver cancer associated with HBV higher.

HBeAb is the antibody produced against HBeAg and its presence in the serum indicates low infectivity and remission of the disease or transmission of the virus (11). A prevalence of 55.6% of HBeAb antibody was observed in this study; this is quite higher compared with 8.0% reported by Odimayo et al. (18) among HBsAg seropositive individuals, 13% reported by Mbaawuaga et al. (14) and 4.7% by Mohammed et al. (15). The high prevalence of HBeAb observed in this study is keeping in line with 51.6% reported by Abah and Aminu among a population of pregnant women in Nigeria (1). The differences in study observation of HBeAb may be due to the difference in the study population.

The prevalence of HBeAg/Ab-positive samples was 54.4%; this is higher than 3.8% reported by Bamidele et al. (3) among pregnant women in Abeokuta, Ogun State, Nigeria. This disparity/variation in prevalence may be as a result of some patients showing other serological cases and methods employed in laboratory analysis of the sample. Fifty-five (42.6%) of the participants were negative for both HBeAg and HBeAb. This could indicate individuals who are clearing the infection or are at the early stage of infection. The rate of negativity observed is <20% prevalence reported by Chinenye et al. (5) among pregnant women in southwestern Nigeria. This difference could be due to the different populations investigated.

Conclusion

This study has shown that HBV replication and transmission is still on the high side. To reduce the prevalence of this deadly disease in Nigeria, more awareness should be created on the virus nationwide. Vaccination should also be made readily available not only to high-risk groups and children but also to everyone. Efforts should also be made to check HBV carriers for their infectious state.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

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