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Immunogenicity and safety of 4 vs. 3 standard doses of HBV vaccination in HIV-infected adults with isolated anti-HBc antibody

Background Presence of isolated anti-HBc antibody is common in HIV-infected patients in endemic areas and could be caused by prior HBV infection with loss of anti-HBs antibody. The role of vaccination in these patients remains controversial and is based largely on limited and low quality data. We, therefore, conducted this study to determine immunogenicity and safety of 4 vs. 3 standard doses of HBV vaccination in HIV-infected adults with isolated anti-HBc antibody. Methods An open-label, randomized controlled trial was conducted among HIV-infected patients visiting HIV clinic of the Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand between July and September 2017. Inclusion criteria included ≥ 18 years of age, currently on a stable antiretroviral regimen, CD4+ cell count ≥ 200 cells/mm3, plasma HIV-1 RNA < 20 copies/mL, and isolated anti-HBc antibody. The participants were randomized to receive either 3 standard doses (20 µg at month 0, 1, 6) or 4 standard-doses (20 µg at month 0, 1, 2, 6) of IM HBV vaccination, and were evaluated for anamnestic response at week 4 and vaccine response at week 28. Results Of the 97 patients screened, 54 (32 male, mean age of 46 years) were enrolled and 27 were allocated to each of the vaccination groups. Anamnestic response occurred in 25.9% vs. 33.3% in 3-dose group vs. 4-dose group, respectively (p = 0.551). The vaccine response rates at week 28 were 85.2% in 3-dose group vs. 88.9% in 4-dose group (p = 1.000); geometric mean titer of anti-HBs antibody at week 28 was 63.8 and 209.8 mIU/mL in 3-dose group and 4-dose group, respectively (p = 0.030). No adverse events were reported. Conclusions An anamnestic response occurred in one-third of Thai HIV-infected patients with isolated anti-HBc antibody who received one dose of HBV vaccination; however, the majority were still unprotected. The use of either 3 or 4 standard-doses of vaccination was highly effective and should be recommended in all HIV-infected individuals with isolated anti-HBc antibody. Trial registration ClinicalTrials.gov; NCT03212911. Registered 11 July 2019, https://clinicaltrials.gov/ct2/show/NCT03212911 Electronic supplementary material The online version of this article (10.1186/s12981-019-0225-3) contains supplementary material, which is available to authorized users.


Background
Hepatitis B virus infection is common in HIV-infected patients, particularly in endemic areas for both viruses. HIV and HBV co-infection also causes higher morbidity and mortality than each infection alone, resulting in

AIDS Research and Therapy
*Correspondence: rchaiwar@gmail.com 1 Division of Infectious Diseases, Department of Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand Full list of author information is available at the end of the article high rates of HBV reactivation and replication, acceleration of HBV progression to chronic hepatitis, cirrhosis and eventually hepatocellular carcinoma [1][2][3][4]. Therefore, HBV vaccination is strongly recommended in all HIV-infected patients with no evidence of prior HBV exposure or immunity [3,4]. However, HIVinfected patients were found to have decreased serological response to HBV vaccination comparing to normal individuals (18-85% vs. > 90%) [5][6][7][8][9], with faster rates of antibody decline after acquiring protective anti-HBs Ab titers [3,10,11]. Various studies have been conducted to determine the optimal HBV vaccination regimen that induced the best immunologic response. The newly proposed regimens: 3 double doses (40 mcg at month 0, 1, 6), 4 double doses (40 mcg at month 0, 1, 2, 6) and 4 standard doses (20 mcg at month 0, 1, 2, 6), resulted in higher response rates [12][13][14]. In contrast, a study in Thailand [15] found that the standard vaccination schedule was highly effective (with a response rate of 88.6%). The 4-double-dose and 4-standard-dose regimens could not significantly increase the response rate (95.4% and 93.2%, respectively).
Presence of isolated anti-HBc antibody is common in HIV-infected patients and could be caused by prior HBV infection with loss of anti-HBs antibody or an occult HBV infection with low level and intermittent viremia [9,[16][17][18][19][20][21][22][23]. Those in the prior group may be at risk of reactivation or reinfection due to the lack of protective immunity and strongly require HBV vaccination [24][25][26]. Anamnestic response to a single dose of HBV vaccination in these population was low (7-32.5%) [9,[27][28][29] compared to those without HIV (41.6%) [27,30]. Hence, a single-dose HBV vaccination is not recommended. Although the European and the DHHS guidelines currently recommend giving a 3 standard doses of HBV vaccination in HIV-infected patients with isolated anti-HBc antibody without routine checking of HBV DNA [31,32], these are based on limited and low quality data. Three trials conducted in the US [9], Switzerland [28] and Italy [33] demonstrated 63%, 60% and 52.6% response rates to 3 standard doses of HBV vaccination, respectively, while a trial in France [34] showed an 89% response rate to a reinforced 3-double-dose vaccination after showing no response to a single standard dose. However, no randomized controlled trial or headto-head comparison trial was available, and a trial on a 4-standard-dose regimen has never been conducted in this population.
Therefore, we conducted this randomized controlled trial to compare the immunogenicity at week 28 and safety of 4 vs. 3 standard doses of HBV vaccination in HIV-infected patients with isolated anti-HBc antibody. Secondary objectives were to determine the percentage of participants with anamnestic response at week 4, the percentage of high-level responders (with anti-HBs Ab ≥ 100 mIU/mL) at week 28, the intensity and frequency of vaccine adverse event (AE), the geometric mean titers of anti-HBs antibody at week 28; and the factors associated with anamnestic response at week 4 and vaccine response at week 28 of both vaccination regimens.
Eligible participants were randomized, with 1:1 allocation ratio and a block size of 4, into 2 groups: (1) 3-dose group receiving recombinant HBV vaccine, produced by the Center for Genetic Engineering and Biotechnology, Cuba (Heberbiovac-HB) 20 µg IM at month 0, 1 and 6; or (2) 4-dose group receiving the same HBV vaccine 20 µg IM at month 0, 1, 2, and 6. Each participant received a diary to record the intensity and frequency of vaccine-related adverse events, containing checklists of occurrence and severity of local reactions at injection sites (edema, redness, pain) or systemic reactions (fever, fatigue, headache) up to 7 days after vaccination. Baseline data were collected including sex, age, contraception method, risk of HIV acquisition, history of intravenous drug use (IVDU) or men who have sex with men (MSM) status, time since HIV diagnosis, cART regimen(s), duration of cART, and all previous results of CD4+ cell counts and plasma HIV-1 RNA. Following laboratory tests were performed at baseline: hepatitis markers (anti-HBs antibody, HBs antigen, anti-HBc antibody, and anti-HCV Ab using CMIA technique by ARCHITECT i2000SR immunoassay analyzer (Abbott Ireland Diagnostics Division, Sligo, Ireland), CD4+ cell count using BD Tritest threecolor reagents, and plasma HIV-a RNA using Roche Cobas AmpliPrep/Cobas Taqman HIV-1 Test, version 2.0, with a limit of detection of 20 copies/mL. At weeks 4 and 28 after the first dose of vaccine, plasma was tested for anti-HBs Ab titer. All tests were performed by technical staff masked to the participants' group allocation.

Definitions of terms
Anamnestic response is defined as having anti-HBs antibody ≥ 10 mIU/mL at week 4 after the first dose of vaccine [9,33,34].
cART active against HBV is defined as a regimen containing either lamivudine, emtricitabine, or tenofovir [35].
Occult HBV infection is the presence of HBV DNA in serum without HBs antigen [33,36].

Statistical analysis
Categorical data were presented as frequency and percentage (%), and continuous data as mean ± standard deviation (SD) or median (interquartile range: IQR) as appropriate. Chi-square test or Fisher's exact test were used to compare proportions between groups, while Student's T-test or Mann-Whitney U test were used to compare continuous data. Predictive factors associated with response to HBV vaccination were tested in logistic regression analysis and characteristics with p < 0.10 in the univariate analysis were included in multivariate models on the basis of a backward-stepwise procedure. A 2-sided test was used to indicate statistical significance at p-value of < 0.05. Analyses were based on the intention to treat. All statistical analyses were performed using StataCorp. 2015. Stata Statistical Software: Release 14. College Station, Tx: StataCorp LP.
From previous findings, we estimated that the percentage of responders in the 3-standard-dose vaccination would be 60% [9,28], compared to 90% in the 4-standard-dose vaccination at week 28 [34]. In order to detect the difference with 90% power and 2-sided α of 0.05, a sample size of 48 participants per group was required, with a total number of 96 participants.

Results
From July to September 2017, 97 HIV-infected patients were screened for eligibility; 43 patients declined to participate the study. The remaining 54 participants were enrolled and 27 each were randomized to receive 3 or 4 standard-doses of HBV vaccination (Fig. 1). There were no dropouts throughout the trial.

Baseline characteristics
Of the 54 enrolled participants, 32 were male (59.3%). The mean age in the 3-dose and 4-dose groups was 45.8 ± 13.5 years and 46.6 ± 11.0 years, respectively. Baseline characteristics of participants in both vaccination groups are shown in Table 1. There was no statistically significant difference in any factor between the 2 groups.
Of all factors evaluated, none were found to be predictive of response to vaccination at week 28, with statistical significance (Additional file 1: Table S2).

Adverse events
No local (edema, redness, and pain) or systemic (fever, fatigue, headache) adverse events to either vaccination regimen were reported in this trial.

Discussion
In this study of HBV vaccination regimens in Thai HIVinfected patients with isolated anti-HBc antibody, the response rate at week 28 after the first dose of vaccination in the 3-standard-dose regimen was very high (85.2%), and the response rate to the 4-standard-dose vaccination schedule was similar (88.9%). This finding differed from previous trials done in Italy, the US, and Switzerland, of which the vaccine response rates were quite low, varying from 52.6 to 63% [9,28,33]. Nonetheless, this high vaccine response was similar to the finding in another trial conducted in Thai HIV-infected patients without any   [15]. The vaccine response rate to the standard HBV vaccination from both Thai studies were almost as high as that from most studies in non-HIV individuals (> 90%) [9,11,37,38]. It is possible that certain genetic or environment factors may play a role in variation of vaccination response between the Asian and Caucasian population. Our study also demonstrated that the geometric mean titer at week 28 after the first dose of vaccination was significantly higher in the 4-standard-dose than that in the 3-standard-dose group. This finding was similar to previous studies and might reflect a more durable immunological response after adding another dose of vaccine to or doubling the dose of vaccine in the vaccination regimen; however, a confirmation by longer follow-up of anti-HBs antibody titer is needed to evaluate for long-term persistence of immunity. This study could not demonstrate any predictive factors for favorable vaccine response at week 28 after the first dose of vaccination; this is similar to another study [28].
For the anamnestic response to a single-dose HBV vaccination in HIV-infected patients with isolated HBc antibody, the rates of 25.9% and 33.3% among the 3-standard-dose and 4-standard-dose groups, respectively, in our study were higher than the rate of 7% in a previous trial conducted in the metropolitan area of Thailand (7%) [29], but were corresponded with those in other studies from various regions [9,27,28,33]. One trial has demonstrated that HIV acquisition through IVDU was a predictive factor for favorable anamnestic response [28]. However, in that trial the proportion of IVDU population was much higher than in our study (43% compared to 1.9%). On the other hand, our study found that age < 45 years old was a predictive factor of higher anamnestic response. This could possibly be explained by stronger immunological memory in younger individuals [39][40][41]. A nadir CD4+ cell count ≥ 100 cells/mm 3 was also found to be a predictor of higher anamnestic response. This finding is logical since better immunological response could be expected in those with higher nadir CD4+ cell count [42,43]. Although the anamnestic response occurred considerably in both of the study groups in this study, the majority of patients still remained unprotected after a single-dose HBV vaccination. Therefore, a single dose vaccination is not adequate and could not be recommended as a standard practice.
This study confirms that HBV vaccination, either using 3 standard doses or adding another dose of vaccine, is considerably safe. There were no serious local or systemic adverse events reported.
There are several limitations of this study. First, the sample size recruited to the study is smaller than the recruitment plan, and this could affect the power of the trial to detect some differences which may exist. However, this sample size limitation occurs similarly in most trials conducted to evaluate this population. A multicenter trial should be done to overcome this limitation. Second, the HBV DNA test was not performed. However, 90.7% of the study population received tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) or lamivudine (3TC). Not performing HBV DNA test is unlikely to affect the outcomes. Third, we were unable to perform longer follow-up for anti-HBs antibody titers to evaluate immune persistence; a plan to follow up at 1 year or longer after vaccination is underway.

Conclusions
This study demonstrated that in Thai HIV-infected patients with isolated anti-HBc antibody, anamnestic response occurred considerably in both vaccination regimens, but the majority of population still remained unprotected. Hence, a single dose vaccination is not  recommended. The usual 3 standard doses of HBV vaccination was highly effective with a high response rate, and adding another standard dose to the vaccination regimen can slightly improve this rate without any statistical significance. However, the 4-dose regimen produces significantly higher antibody titer that may have benefit in the long run. The use of either 3 or 4 standard-doses of HBV vaccination was highly effective and safe; this should be recommended in all HIV-infected individuals with isolated anti-HBc antibody.

Additional file
Additional file 1: Table S1. Comparison of characteristics between those who had and did not have anamnestic response (anti-HBs ≥ 10 mIU/mL at week 4). Table S2. Comparison of characteristics between responders and non-responders (anti-HBs ≥ 10 mIU/mL) at week 28.
Authors' contributions NL participated in participant enrollment, data analysis, data interpretation, and drafted the manuscript. JP participated in patient randomization and data collection. WK participated in participant enrollment. KS participated in trial design, data interpretation, and revised the manuscript critically for important intellectual content. RC participated in the trial design, data analysis, data interpretation, and drafted the manuscript. All authors read and approved the final manuscript.