Effect of hepatitis B immunoglobulin on interruption of HBV intrauterine infection

Abstract

AIM: To evaluate the efficacy of hepatitis B immunoglobulin (HBIG) in interrupting hepatitis B virus (HBV) intrauterine infection during late pregnancy.

METHODS: We allocated 112 HBsAg positive pregnant women into 2 groups randomly. Fifty seven cases in the HBIG group received 200 IU (unit) HBIG intramuscularly every 4 wk from the 28 wk of gestation to the time of delivery, while 55 cases in the control group received no special treatment. HBsAg, HBeAg, HBcAb, HBeAb, HBsAb and HBV DNA levels were tested in the peripheral blood specimens from all of the mothers at 28 wk of gestation, just before delivery, and in blood from their newborns within 24 h before administration of immune prophylaxis.

RESULTS: The intrauterine infection rate in HBIG group and control group were 10.5% and 27.3%, respectively, with significant difference (P < 0.05). It showed ascendant trend as HBV DNA levels in the peripheral blood increased before delivery.

CONCLUSION: HBIG is potent to cut down HBV intrauterine infection rate significantly when administered to pregnant women regularly during late pregnancy. The possibility of HBV intrauterine infection increases if maternal blood HBV DNA ≥ 10⁸ copies/mL.

Key Words: $[Keywords]

INTRODUCTION

China is a high incidence area of hepatitis B virus (HBV) infection, with a mean HBsAg positive rate of about 10%. Forty to fifty percent of chronic HBV carriers are caused by vertical transmission, which ranks it among the important modes of HBV infection and an important reason of so many HBV carriers in the crowd. Also, it has close correlations with chronic hepatitis, liver cirrhosis and liver cancer. Intrauterine transmission is one of the main resources of hepatitis B virus (HBV) vertical infection, but there is no definite prophylaxis up to now[1-6]. Through HBV DNA quantitation by fluorogenic quantitative polymerase chain reaction (FQ-PCR), we evaluated the efficacy of HBIG in interrupting HBV intrauterine infection during late pregnancy and analyzed the relation between maternal HBV DNA level and the rate of intrauterine transmission.

MATERIALS AND METHODS

Patients

The subjects were drawn from pregnant women who had undergone regular prenatal check-up, and had been admitted for labor and followed up at the Obstetric Department of the Third Affiliated Hospital of Sun Yat-Sen University from December 1999 to October 2001.

The following eligible criteria should all be met: (1) single pregnancy; (2) gestational age ≤ 28 wk; (3) HBsAg positive in serum; (4) normal liver and kidney functions; (5) serial tests were negative for HAV, HCV, HDV and HEV; (6) exclusion of fetal anomalies by B-ultrasonography; (7) no receipt of other agents that were under research, anti-virus, immunomodulating, cytotoxic or steroid hormones during pregnancy; (8) their husbands were not HBV carriers or hepatitis B patients; and (9) ability to give written informed consent.

Methods

A total of 112 pregnant women according to the criteria set above and their newborns of 112 cases were chosen. The pregnant women were randomly divided into a HBIG group (57 cases) and a control group (55 cases). Each case in the HBIG group received 200 IU of HBIG ( produced by Sichuan Shuyang Pharmaceutical Ltd.) intramuscularly (im) every four weeks from 28 wk of gestation till delivery, while patients in the control group were given no special treatment. Blood specimens were tested for HBsAg, HBeAg, HBsAb, HBeAb, and HBcAb by enzyme linked immunosorbent assay (ELISA, assay kits produced by Zhongshan Biological Products Ltd.), and HBV DNA quantitation by FQ-PCR (assay kits produced by Da’an Genetic Diagnosis Center of Sun Yat-Sen University) in all the subjects at 28 wk and on the day of delivery, and their newborns (blood from femoral vein) 24 h after birth before the administration of immune prophylaxis. All the subjects followed-up regularly during pregnancy.

HBV intrauterine infection was defined as follows: HBsAg and/or HBV DNA positive in peripheral blood of newborns in 24 h after birth before the administration of active or passive immune prophylaxis.

Statistics

The quantity of HBV DNA was transformed to the form of log₁₀ and then expressed as mean ± SD. All data were analyzed as χ² (chi-square) test for positive difference and t test for comparisons of means between the 2 groups using SPSS 10.0 for windows. For all comparisons, P < 0.05 was considered statistically significant.

RESULTS

Clinical characteristics of pregnant women

There were no significant differences between the two groups as for age, nation, gravidity, abortive parity, gestational weeks, way of delivery, or pregnant complications (P > 0.1, Table 1).

Table 1 Clinical characteristics of pregnant women of each group.

Characteristics	HBIG group (n = 57)	Control group (n = 55)
Age (yr)	26.9 ± 1.8	27.8 ± 2.8
Nationality of Han	57	55
Gravidity	1.5 ± 0.9	1.9 ± 1.2
Abortive parity	0.6 ± 0.7	0.7 ± 1.0
Gestational weeks	39.5 ± 1.9	39 ± 1.3
Rate of cesarean section	27 (47.4%)	25 (45.5%)
Threatened abortion	7	5
Threatened premature labour	2	2
Premature rupture of membrane	0	0
Pregnancy induced hypertension syndrome	1	1
Premature delivery	0	1
Postmature labour	0	0
Elderly primipara	0	0
Medical and surgical associated diseases	2	2
HBeAg positive rate	36 (63.2%)	28 (50.9%)
HBV DNA level (log10)	5.75 ± 2.98	5.54 ± 3.09

Intrauterine transmission of HBV

There were 6 cases of intrauterine infection in HBIG group. The counterpart in control group was 15. HBV intrauterine infection rate in HBIG group and control group were 10.5% and 27.3%, respectively, with significant difference (P < 0.05, Table 2).

Table 2 Characters of neonatal HBV intrauterine infection.

	Neonates n	HBsAg	HBeAg	HBcAb	HBeAb	HBsAb	HBV DNA	n	Intrauterine infection n (%)
Control group	55	+	-	+	+	-	-	2	15 (27.27)
		-	-	-	-	-	+	3
		-	-	-	+	-	+	3
		-	+	+	-	-	+	3
		-	-	+	+	-	+	4
HBIG group	57	+	-	+	+	-	-	1	6 (10.53)
		+	+	+	-	-	-	1
		-	-	+	-	-	+	4

Intrauterine transmission and the level of HBV DNA in maternal serum

The levels of HBV DNA were divided into 7 grades according to the fluorescent signals set by the operation manual, with grade 0 (< 10⁵ copies/mL), grade 1 (< 10⁶ copies /mL), grade 2 (< 10⁷ copies/mL), grade 3 (< 10⁸ copies/mL), grade 4 (< 10⁹ copies/mL), grade 5 (< 10¹⁰ copies/mL), and grade 6 (< 10¹¹ copies/mL). The intrauterine infection rate increased with the increase in HBV DNA level in maternal blood, with odds ratio (OR) increasing. The results of rank correlation and χ² test indicated that although it showed an ascendant trend, there were no significant differences in intrauterine infection rate between grade 2 and grade 1, grade 3 and grade 2, grade 5 and grade 4. But there was significant difference between grade 3 and grade 4 (P < 0.05, Table 3).

Table 3 HBV DNA levels in blood of mothers at delivery and HBV intrauterine infection.

HBV DNA grade	Mothers (n)	Intrauterine infection		Value of OR
		n	Percentage (%)
Grade 0 (< 105copies/mL)	26	0	0	...
Grade 1 (< 106copies/mL)	22	0	0	...
Grade 2 (< 107copies/mL)	15	2	13.33	1.00
Grade 3 (< 108copies/mL)	13	2	15.38	5.55
Grade 4 (< 109copies/mL)	32	15	46.88	26.91
Grade 5(< 1010copies/mL)	4	2	50.00	30.50

Safety

No adverse events such as fever, rigor, skin rash, inflammation and scleroma at local injected area, or impairment of renal function as well as other discomforts were found during the medication of HBIG. As to Apgar score and development reference such as weight and height of the newborns at delivery, there were no significant difference between the 2 groups (P > 0.1, Table 4).

Table 4 Development indices of neonates and Apgar score (mean ± SD).

	Weight (kg)	Height (cm)	1-minute Apgar score
HBIG group	3.05 ± 0.25	48.0 ± 1.4	10 ± 0.0
Control group	3.04 ± 0.45	48.1 ± 1.5	9.9 ± 0.3

DISCUSSION

Several studies have proved that maternal infectivity is the most important factor in intrauterine transmission of HBV[7], in which HBV DNA shows directly the condition of replication and infectivity of the virus in vivo. The latter can be exactly reflected through HBV DNA quantitation by FQ-PCR test clinically[8,9]. With the prominent sensitivity and specificity of the FQ-PCR test, our study indicated that the intrauterine infection rate had significant correlation with the level of HBV DNA in the maternal serum before delivery, which showed an ascendant trend; the intrauterine infection rate significantly increased at the level of HBV DNA ≥ 10⁸ copies/mL, which was consistent with the findings by Ngui et al[10]. Those findings suggest that the threshold of HBV DNA ≥ 10⁸ copies/mL is a potent index of HBV intrauterine infection. To those pregnant women whose serum levels of HBV DNA are high and have high infectivity, we propose to apply highly effective and safe anti-viral medicines to compress the replication of HBV and, therefore, rapidly and dramatically decrease HBV DNA level to interrupt intrauterine infection[11].

In this study, the intrauterine infection rate in the HBIG group and control group were 10.5% and 27.3%, respectively, which suggested that the intramuscular administration of HBIG regularly before delivery could effectively interrupt HBV intrauterine infection[12]. HBIG is a kind of passive antibody. One of its components, HBsAb, can combine with HBsAg, activate the complements, clear HBV, lower the level of virus in maternal blood, and thereby prevent and decrease the infection of normal cells. It was reported that the interruptive effect of HBV intrauterine infection by HBIG might correlate with the acquisition of neonatal passive immune, because placenta could transmit the antibody of IgG actively from mother to fetus during late pregnancy[13]. However, HBsAb was detected in none of the newborns in our study. The potential reason might be that the HBV level in maternal blood was so high (higher than the quantity that can be neutralized by the passive antibody) that the HBIG administrated to mother might not be enough to enter fetal body through placenta. So, we consider to increase the quantity of HBIG in our further studies of HBV intrauterine interruption.

We found that some newborns were HBsAg and HBV DNA negative but HBeAg positive in their blood drawn from femoral vein within 24 h after birth. Whether HBeAg can pass placenta is still under hot debate. It has been suggested that HBeAg can be more easily transmitted via placenta than HBsAg in that it is smaller than the latter and is free from agglutination[14]. HBeAg or the compound of HBeAg and α-HBeIgG can pass the barrier of placenta by means of active-transfer in human body[15]. One study also showed that some babies of HBV infected mothers were HBeAg positive and HBsAg negative in femoral blood at birth, and HBsAg titres of the mothers were significantly higher than HBeAg titres (200 times or more). So the positive HBeAg in neonatal serum could not be interpreted as contamination or leakage from the placenta, but can only be explained by that HBeAg can indeed cross placenta[16]. In our study, babies who were only HBeAg positive were born by mothers who were both HBsAg and HBeAg positive. Moreover, the sensitive and specific HBV-infection marker of HBV DNA quantitation were negative in neonatal peripheral blood, and HBeAg disappeared by 9-12 mo of age. So HBeAg in the neonatal peripheral blood is less likely to be an index of intrauterine infection, but transmitted passively from maternity.