Open Access

Hepatitis B virus genotypes and evolutionary profiles from blood donors from the northwest region of China

Virology Journal20096:199

DOI: 10.1186/1743-422X-6-199

Received: 21 July 2009

Accepted: 17 November 2009

Published: 17 November 2009

Abstract

Hepatitis B virus (HBV) is prevalent in China and screening of blood donors is mandatory. Up to now, ELISA has been universally used by the China blood bank. However, this strategy has sometimes failed due to the high frequency of nucleoside acid mutations. Understanding HBV evolution and strain diversity could help devise a better screening system for blood donors. However, this kind of information in China, especially in the northwest region, is lacking. In the present study, serological markers and the HBV DNA load of 11 samples from blood donor candidates from northwest China were determined. The HBV strains were most clustered into B and C genotypes and could not be clustered into similar types from reference sequences. Subsequent testing showed liver function impairment and increasing virus load in the positive donors. This HBV evolutionary data for China will allow for better ELISA and NAT screening efficiency in the blood bank of China, especially in the northwest region.

Introduction

Hepatitis B virus (HBV) poses a great threat to humans, with serious consequences including liver cirrhosis, hepatocellular carcinoma and polyarteritis nodosa [1]. This infection is prevalent in Asia, Africa, Southern Europe and Latin America [2]. Roughly 2 billion people, one-third of the world's population, have serological evidence of past or ongoing infection with HBV. Approximately 5-10% of infected adults and 80-90% of children become chronic carriers of HBV [3, 4]. China has been heavily affected over a considerable period of time; consequently about 10% of the population are carriers or sufferers [5].

Because of the high prevalence of HBV, the blood bank of China must screen donors for HBV infection [6]. All samples from blood donors are tested for HBV surface antigen (HBsAg) and alanine amino transferase (ALT). HBsAg is currently identified by ELISA, and ALT is tested for using dynamic enzyme methods. Undoubtedly, such screening is instrumental in reducing the risk of HBV transmission through blood transfusion [7]. However, as mutations can occur in different viral stains, ELISA occasionally fails to detect HBV-infected donors [811].

DNA tests have revealed that HBV strains from blood donors vary in different geographical areas. Occult HBV infection, which threatens the safety of blood transfusion, is linked at least in part to the genetic distance of the viral strains [12]. Nucleic acid testing (NAT) for HBV in a large number of blood donors has identified HBV DNA-positive but HBsAg-negative donors, providing a unique opportunity to investigate HBV infection in more detail [13, 14].

Although the DNA test is superior to ELISA and can overcome some of its disadvantages, in China the higher cost and imperfect protocols have prevented widespread use. Consequently, until now, ELISA has remained the major testing method in China. To improve HBsAg testing, it is necessary to probe HBV virus evolution, because evolutionary analysis will help to promote ELISA innovations [15]. However, data about HBV evolution in Chinese donors, especially in the northwest region of China, is not yet available, creating a hurdle for the development of more efficient testing.

Here we reported that 11 HBV strains from northwest China blood donor candidates were mostly clustered into B and C genotypes. These pathogens, which appear to have developed from a common parent, could not be clustered into similar genotypes from the reference sequences. This points to a high mutation frequency of HBV. Follow-up testing showed liver function impairment and increased virus load in these positive donors. Our research has supplied HBV evolution data and will pave the way for improving ELISA and NAT screening in the blood bank of China.

Materials and methods

Blood donor recruitment and sample collection

120 donors, negative for anti-HCV and anti-HIV antibodies, were analyzed. All recruited donors were unremunerated volunteers from either urban or rural areas. They were medically assessed and via a questionnaire denied any known risk factors for viral infection. Donors found to be HBV carriers were also asked to give follow-up blood samples for further study. The study was approved by the Ethics Committee of Fourth Military Medical University and written informed consent was obtained from the participants.

HBV serological marker determination

Testing for HBV serological markers, including HBs, anti-HBs, anti-HBe, HBe and anti-HBs, were performed by ELISA using an automatic enzyme detection system (Tecan, Swiss) and a commercial kit (InTec Products, China) according to the manufacturers' protocols. For the quantitative detection of the markers, serum from blood donors was applied to AXSYM MEIA (Abbott Diagnostics, Germany). To measure the ALT level, serum was separated and run through an automatic biochemistry analyzer (Hitachi, Japan) using Kit (Shanghai Fousun Long March Medical Scince.Co.Ltd. China).

2.3 DNA analysis

NAT was adapted for the current study as previously described [16]. Briefly, 120 donor blood samples were divided into 10 pools with 12 samples each pool. DNA from the blood samples was extracted according the manufacturer's protocol (Qiagen, Germany) and mixed [16]. Real-time PCR was used to detect HBV in each pool, following the manufacturer's instructions (Qiagen, Germany). If a positive reaction was observed, the pool was divided into 6 samples and real-time PCR was repeated. If there was a second positive test, each individual sample was tested. After that, quantitive PCR was employed for to quantify viral load.

As Katsoulidou et al. described [17], positive samples were genotyped using nest-PCR. Briefly, the first-round PCR primers (outer primer pairs) and second-round PCR primers (inner primer pairs) were designed on the basis of the conserved nature of nucleotide sequences in the regions of the pre-S1 through S genes. At the end, agar electrophoresis was employed to discern genotype.

11 HBV DNA reactive samples were randomly picked out (hereafter referred to as donors 1 to 11). From these samples, HBV DNA was extracted from 1.0 mL of serum using a kit (Qiagen GmbH, Germany), according to the manufacturer's instructions. Then, sequence analysis, beginning from the S region of HBV genome, was performed by an external company (Sunbiotech. Ltd China) using an ABI sequencing system.

Phylogenetic analysis

HBV genome phylogenetic analysis was performed by multiple sequence alignment using the ClustalW v1.83 program [18]. For this purpose, HBV sequences from the donors and reference sequences from the GenBank database http://www.ncbi.nih.gov were aligned.

Results

NAT screening of 11 HBV-infected donors

To screen the HBV-infected donors, NAT was employed based on real-time PCR. In the first round of screening, there were 6 positive pools (Fig. 1A, 60%). A single positive HBV sample was eventually identified by repeat real-time PCR. There were 12 reactive blood donors, representing about 9% of all the recruited donors.
Figure 1

NAT screening of 11 reactive samples from 120 blood donors. To screen the HBV infected donors, NAT was employed. 120 donor blood samples were divided into 10 pools with 12 samples in each pool. Real-time PCR was used on each pool. If a positive reaction was observed, the pool was narrowed until a single reactive sample was detected. Quantitive PCR was then performed against positive samples. A, reactive sample counts of each pool in the first round of detection; blank represents HBV-reactive sample counts and black is the total sample counts in the pool; B, lower HBV DNA copies of reactive samples in the NAT-reactive samples; C higher HBV DNA copies of reactive samples in the NAT-reactive samples.

Next, HBV DNA load in the positive donors was measured. As shown in Figures 1B and 1C, donors 3, 4, 5 and 7 had several hundred virus copies, while donors 1,2,6,8,9,10 and 11 had lower virus loads.

The serological and personal data of the HBV DNA-reactive donors are noted in Tables 1 and 2. Consistent with virus load, donors 3, 4, 5 and 7 had higher ALT levels (Table 1 and Fig. 1C), which were all beyond the upper limit (20 IU.L-1) for blood donors formulated by China. On the other hand, serological marker analysis of HBV in the samples showed that donors 3 and 4 were more contagiousness, as they were HBsAg, HBeAg and anti-HBc positive (Table 2). Although HBsAg in donor 6 was negative (Table 2), HBV DNA testing proved there were few virus copies (Fig. 1B).
Table 1

Data of blood donors with positive HBsAg reaction

NO.

Year

Femal/Male

ALT(U.L-1)

1

26

M

17

2

44

F

12

3

32

F

39

4

22

M

49

5

39

M

29

6

50

M

19

7

25

M

47

8

41

F

15

9

21

F

19

10

43

M

20

11

35

F

21

Table 2

Serological markers of donors bearing HBV

NO.

HBs

Anti-HBs

HBe

Anti-HBe

Anti-HBc

1

+

+

-

-

+

2

+

-

-

+

+

3

+

-

+

-

+

4

+

-

+

-

+

5

+

-

+

-

-

6

-

-

-

-

-

7

+

+

-

-

+

8

+

-

-

+

+

9

+

+

-

-

+

10

+

-

-

-

+

11

+

-

-

+

-

Total

10

3

3

3

8

The major HBV strains in local donors were B and C genotypes

HBV strains vary in different regions and different strains may contribute to ELISA test failure. To further discern the HBV type in the infected samples, all 11 positive samples underwent HBV genotyping by PCR (Fig. 2A). 9 virus strains, from approximately 81% of all the positive samples, belonged to the B or C group, but 2 D genotype strains (19%) were also observed (Fig. 2B). Furthermore, the HBV DNA load in cases with the C subtype was higher than that in the B or D genotypes (Fig. 1B and 1C).
Figure 2

Genotyping of HBV reactive blood donors. All positive samples from the blood donors were subjected to DNA extraction and then genotyping by nest-PCR. A, gel electrophoresis of PCR products after nest-PCR in genotype analysis (data represents one of three independent experiments); B, sample counts of each genotype according A.

HBV strains from local donors evolved from common parents

HBV has evolved in recent years. This evolution has resulted in blood transfusion transmission because of ELISA test failures. Since most of the HBV strains in the current study belonged to the B or C genotypes, we further sequenced the HBV-DNA positive samples to make a phylogenetic appraisal. Fortunately, all the strains were successfully sequenced. Then, a phylogenetic tree was made, joined by reference sequence from GeneBank using Clustal W 1.83 software. According to the tree, the 2 donor samples belonging to the D genotypes (donors 2 and 10) were highly homogenic, while the 4 C strains (donors 3, 4, 5 and 7) came from a common 'parent' (Fig. 3). With the 5 B strains, the situation was more complex. Although they derived from the same root, two evolutionary directions were identified. As shown in Figure 3, the virus strain from donors 1 and 8 was clustered, while the strain from donors 6, 9 and 11 belonged to another group.

On the whole, however, the strains could not be clustered into a similar subtype using reference sequences, which proves the high mutation rate of HBV.
Figure 3

Phylogenetic analysis of HBV strains from the blood donors. HBV genome sequencing was carried out. Some available sequences from the GenBank database were used to construct the tree with the Clustal W v1.83 program. Figures in the lower part of the tree are the blood donors' numbers; characters in the other part of the tree are serial numbers in GeneBank; characters in the right bracket refer to HBV genotype.

Infection of HBV-positive donors worsened in the following 3 years

To monitor HBV infection after the preliminary analysis, we tracked the positive blood donors in the following years. Two years later, donor 6, who was negative reaction in the preliminary serological test, became reactive against HBsAg, while the other donors displayed increased positive markers of infection (Table 3). Repeat ALT testing showed that the liver function of these donors was, at least partly, impaired (Table 4). We noted that the level of ALT in donor 3 decreased because she received anti-viral therapy (Table 4). Virus load was serially quantitated by real-time PCR. As shown in Table 5, the number of virus copies increased in all reactive donors, except donor 3 (who was being treated). Once again, several hundred HBV copies were detected in donor 6.
Table 3

Quantitive levels of serological markers of HBV in reactive donors two years later

NO.

HBs(nq.mL-1)

Anti-HBs

(mIU.mL-1)

HBe

(ncuq.mL-1)

Anti-HBe

(ncuq.mL-1)

Anti-HBc

(ncuq.mL-1)

donor 1

2.8

32.1

0.02

6.2

11.8

donor 2

3.1

41.0

0.08

5.9

8.3

donor 3

15.2

192.5

2.5

121.8

31.2

donor 4

19.8

288.1

10.1

117.4

15.7

donor 5

62.9

162.3

8.4

125.9

12.1

donor 6

1.9

24.2

0.01

2.7

0.9

donor 7

7.5

69.8

8.7

18.1

11.9

donor 8

12.7

32.2

0.09

7.3

7.1

donor 9

13

33.9

0.01

6.9

5.9

donor10

2.6

42.3

0.02

8.5

6.7

donor11

12.5

51.7

0.07

6.6

6.8

ncu: national clinical unit.

Table 4

ALT levels in the consecutive test of HBV reactive donors

Time(month)

ALT(U.L-1)

 

3

6

9

12

15

18

21

24

27

30

33

36

donor 1

18

20

19

26

30

33

39

40

49

56

60

63

donor 2

11

15

18

24

32

43

49

51

59

67

N

N

donor 3

35

50

57

68

78

90

102

110

123

151

130

107

donor 4

55

54

55

62

68

65

71

75

80

86

90

96

donor 5

32

34

39

40

40

47

48

46

50

56

57

59

donor 6

20

20

19

26

28

23

39

40

45

46

N

48

donor 7

47

53

57

56

58

60

61

59

70

76

80

87

donor 8

12

14

15

12

18

25

21

25

20

26

32

34

donor 9

14

14

17

20

19

21

22

25

20

21

N

N

donor 10

21

20

29

26

28

23

29

30

N

40

41

40

donor 11

26

25

29

27

28

33

29

31

38

41

35

44

N: no test.

Table 5

Virus load in the following test of HBV reactive donors

Time(month)

Virus Copy

 

6

12

18

24

30

36

donor 1

6.1E1

7.9 E1

8.8 E1

10 E2

15 E3

21 E3

donor 2

2.1 E1

5.3 E1

6.7 E1

8.2 E2

11.8 E1

N

donor 3

2.8 E2

5.4 E2

2.3 E3

3.5 E3

1.2 E3

2.1 E3

donor 4

3.9 E2

8.3 E2

4.3 E3

7.5 E3

0.3 E4

32.0E4

donor 5

1.6 E2

44 E2

1.3 E3

4.5 E3

3.2 E4

4.9 E4

donor 6

1.2 E1

3.9 E1

6.2 E1

9.8 E2

11 E2

1.7 E3

donor 7

3.2 E2

24.1 E2

86.7 E2

2.5 E3

8.2 E3

14.1 E3

donor 8

5.7 E1

6.3 E1

7.5 E1

9.4 E2

10.1 E2

14.9 E3

donor 9

1.3 E1

4.2 E1

5.9 E1

7.2 E2

7.8 E2

9.3 E3

donor 10

8.6 E1

9.9 E1

16.7 E1

2.5 E2

5.3 E2

14.6 E2

donor 11

4.5 E1

5.6 E1

16.8 E1

4.1 E2

12.3 E2

25.3 E2

N: no test. E1:101; E2:102;E3:103;E4:104.

Discussion

NAT has been globally adopted in blood banks to detect infectious pathogens, especially in developed nations [16]. With a proper pool size, it can detect several virus copies in a sample. In this way, the testing window period of pathogens, which is one of the most important risk factor in transfusion medicine, can be overcome. However, due to lower numbers of virus copies during early stages of infection, NAT sometimes produces false negative results. Consequently, pool size becomes a key factor in interpreting NAT. In the current study, our NAT system could detect 10 copies of HBV. This sensitivity was enough to detect the virus in a 6-sample pool.

Other disadvantages have prevented the wider uptake of NAT [19]. One complex issue is how to determine the appropriate blood donor pool size [20, 21]. We screened 11 reactive samples from 120 blood donors using NAT. The samples were divided into 10 pools and each pool contained 12 samples. In effect, 3 real-time PCRs were run before the single reactive sample was found. If we made larger pools, perhaps more real-time PCRs would have been performed, given the high prevalence of HBV in China. We found that the test results from NAT were almost perfectly consistent with ELISA testing (9.16% V.S 8.33%, P > 0.05), although the latter failed in donor 6 due to lower HBV virus copy numbers. We therefore agree with earlier authors that ELISA can be used as the first round test and NAT in the second round analysis [22].

In 1988, Okamoto et al. categorized HBV into A, B, C and D types according the genome sequence diversity [23]. There are now 8 known genotypes of HBV, from A to H, with a genome difference greater than 8% [24, 25]. Genotypes A, B, C and D are all observed in China. Consistent with other reports, we confirmed that the B and C genotypes are the most common in China [26]. Genotype of HBV is significant to prognosis and test strategy [27]. We found that blood donors with the C genotype had higher virus loads and more serious liver impairment in the following years, which is consistent with the findings of other researchers [28].

According to our serological data, the 11 positive samples could be divided into two major groups: 6 subjects (54.5%) were anti-HBc positive without detectable antibodies to surface antigen, whereas 3 (27.2%) were positive for both anti-HBc and anti-HBs. These results indicate that occult HBV infection can occur in blood donors [29, 30]. It has been reported that occult HBV infection without anti-HBs is more dangerous because cases of transmission by donations carrying anti-HBc without anti-HBs have been documented, while no evidence of transmission has been found when donors were both anti-HBc and anti-HBs reactive [31, 32].

Phylogenetic analysis is a method commonly used to trace virus evolution [33]. With HBV, an evolutionary tree can be drawn from a partial sequence or the whole genome [34]. We made a genome tree and, surprisingly, found that the strains in our region could not be clustered into similar types using reference sequences. The reason may be the high mutation rate of HBV, for which there is considerable supporting evidence [35, 36]. However, virus subtypes B or C, which were found in the present study, are clues suggesting different evolutionary roots. We likewise did not detect recombinant HBV strains, which have occasionally been reported as intertypes [37, 38]. Recombinant HBV strains, if present, might contribute to the diverse phylogenetic profile in our region. On the other hand, the virus strains we detected that were of the same type had clearly developed from the same progenitors, which suggested that local HBV evolution had specific characteristics. This phenomenon is relevant for both ELISA and NAT improvement.

In summary, the 11 HBV strains from northwest China blood donor candidates which we identified were mostly clustered into B and C genotypes. These organisms could not be clustered into similar types using reference sequences. Follow-up testing showed liver function impairment and increasing virus load in the positive donors. The study provides evolutionary data about HBV in China and could lead to improvements in ELISA and NAT screening efficiency in the blood bank of China.

Declarations

Acknowledgements

We are thankful for the support of the Blood Bank of Xi'an, PLA.

Authors’ Affiliations

(1)
Department of Blood Transfusion, Xijing Hospitalthe Fourth Military Medical University
(2)
Department of Clinic Molecular Research Center & Clinic Diagnostic Laboratory, Xijing Hospital, Fourth Military Medical University
(3)
Department of Molecular Genetics, Third Military Medical University
(4)
Department of Electron Microscope,Centralab, Fourth Military Medical University

References

  1. Ganczak M, Szych Z, Korzen M: Preoperative vaccination for HBV at Polish hospitals as a possible public health tool to limit the spread of the epidemic: A cross-sectional study. Vaccine 2009, 27: 3969-74. 10.1016/j.vaccine.2009.04.042View ArticlePubMedGoogle Scholar
  2. Hong WD, Zhu QH, Huang ZM, Chen XR, Jiang ZC, Xu SH, Jin K: Predictors of esophageal varices in patients with HBV-related cirrhosis: a retrospective study. BMC Gastroenterol 2009, 9: 11. 10.1186/1471-230X-9-11PubMed CentralView ArticlePubMedGoogle Scholar
  3. Mendy M, D'Mello F, Kanellos T, Oliver S, Whittle H, Howard CR: Envelope protein variability among HBV-Infected asymptomatic carriers and immunized children with breakthrough infections. J Med Virol 2008, 80: 1537-46. 10.1002/jmv.21221View ArticlePubMedGoogle Scholar
  4. Kao JH, Chen PJ, Lai MY, Chen DS: Sequence analysis of pre-S/surface and pre-core/core promoter genes of hepatitis B virus in chronic hepatitis C patients with occult HBV infection. J Med Virol 2002, 68: 216-20. 10.1002/jmv.10188View ArticlePubMedGoogle Scholar
  5. Liu SL, Dong Y, Zhang L, Li MW, Wo JE, Lu LW, Chen ZJ, Wang YZ, Ruan B: Influence of HBV gene heterogeneity on the failure of immunization with HBV vaccines in eastern China. Arch Virol 2009, 154: 437-43. 10.1007/s00705-009-0315-yView ArticlePubMedGoogle Scholar
  6. Shang G, Yan Y, Yang B, Shao C, Wang F, Li Q, Seed CR: Two HBV DNA+/HBsAg- blood donors identified by HBV NAT in Shenzhen, China. Transfus Apher Sci 2009, 4: 3-7. 10.1016/j.transci.2009.05.001View ArticleGoogle Scholar
  7. Jongerius JM, Wester M, Cuypers HT, van Oostendorp WR, Lelie PN, Poel CL, van Leeuwen EF: New hepatitis B virus mutant form in a blood donor that is undetectable in several hepatitis B surface antigen screening assays. Transfusion 1998, 38: 56-9. 10.1046/j.1537-2995.1998.38198141499.xView ArticlePubMedGoogle Scholar
  8. Carman WF: The clinical significance of surface antigen variants of hepatitis B virus. J Viral Hepat 1997,4(Suppl 1):11-20. 10.1111/j.1365-2893.1997.tb00155.xView ArticlePubMedGoogle Scholar
  9. Ashton-Rickardt PG, Murray K: Mutants of the hepatitis B virus surface antigen that define some antigenically essential residues in the immunodominant a region. J Med Virol 1989, 29: 196-203. 10.1002/jmv.1890290310View ArticlePubMedGoogle Scholar
  10. Kupski C, Trasel FR, Mazzoleni F, Winckler MA, Bender AL, Machado DC, Schmitt VM: Serologic and molecular profile of anti-HBc-positive blood bank donors in an area of low endemicity for HBV. Dig Dis Sci 2008, 53: 1370-4. 10.1007/s10620-007-0019-7View ArticlePubMedGoogle Scholar
  11. Hou J, Wang Z, Cheng J, Lin Y, Lau GK, Sun J, Zhou F, Waters J, Karayiannis P, Luo K: Prevalence of naturally occurring surface gene variants of hepatitis B virus in nonimmunized surface antigen-negative Chinese carriers. Hepatology 2001, 34: 1027-34. 10.1053/jhep.2001.28708View ArticlePubMedGoogle Scholar
  12. Allain JP: Occult hepatitis B virus infection: implications in transfusion. Vox Sang 2004, 86: 83-91. 10.1111/j.0042-9007.2004.00406.xView ArticlePubMedGoogle Scholar
  13. Chevrier MC, St-Louis M, Perreault J, Caron B, Castilloux C, Laroche J, Delage G: Detection and characterization of hepatitis B virus of anti-hepatitis B core antigen-reactive blood donors in Quebec with an in-house nucleic acid testing assay. Transfusion 2007, 47: 1794-802. 10.1111/j.1537-2995.2007.01394.xView ArticlePubMedGoogle Scholar
  14. Brojer E, Grabarczyk P, Liszewski G, Mikulska M, Allain JP, Letowska M: Characterization of HBV DNA+/HBsAg- blood donors in Poland identified by triplex NAT. Hepatology 2006, 44: 1666-74. 10.1002/hep.21413View ArticlePubMedGoogle Scholar
  15. Chen WN, Oon CJ, Toh I: Altered antigenicities of hepatitis B virus surface antigen carrying mutations outside the common "a" determinant. Am J Gastroenterol 2000, 95: 1098-9.PubMedGoogle Scholar
  16. Lelie N, Heaton A: Hepatitis B - a review of the role of NAT in enhancing blood safety. J Clin Virol 2006,36(Suppl 1):S1-2. 10.1016/S1386-6532(06)80001-6View ArticlePubMedGoogle Scholar
  17. Katsoulidou A, Paraskevis D, Magiorkinis E, Moschidis Z, Haida C, Hatzitheodorou E, Varaklioti A, Karafoulidou A, Hatzitaki M, Kavallierou L, Mouzaki A, Andrioti E, Veneti C, Kaperoni A, Zervou E, Politis C, Hatzakis A: Molecular characterization of occult hepatitis B cases in Greek blood donors. J Med Virol 2009, 81: 815-25. 10.1002/jmv.21499View ArticlePubMedGoogle Scholar
  18. Thompson JD, Higgins DG, Gibson TJ: CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res 1994, 22: 4673-80. 10.1093/nar/22.22.4673PubMed CentralView ArticlePubMedGoogle Scholar
  19. Busch MP: Should HBV DNA NAT replace HBsAg and/or anti-HBc screening of blood donors? Transfus Clin Biol 2004, 11: 26-32. 10.1016/j.tracli.2003.12.003View ArticlePubMedGoogle Scholar
  20. Sato S, Ohhashi W, Ihara H, Sakaya S, Kato T, Ikeda H: Comparison of the sensitivity of NAT using pooled donor samples for HBV and that of a serologic HBsAg assay. Transfusion 2001, 41: 1107-13. 10.1046/j.1537-2995.2001.41091107.xView ArticlePubMedGoogle Scholar
  21. Yoshikawa A, Gotanda Y, Itabashi M, Minegishi K, Kanemitsu K, Nishioka K: HBV NAT positive [corrected] blood donors in the early and late stages of HBV infection: analyses of the window period and kinetics of HBV DNA. Vox Sang 2005, 88: 77-86. 10.1111/j.1423-0410.2005.00602.xView ArticlePubMedGoogle Scholar
  22. Sato S, Ohhashi W, Ihara H, Sakaya S, Kato T, Ikeda H: Efficacy of HBV NAT of pooled donor samples. Transfusion 2002, 42: 660. 10.1046/j.1537-2995.2002.00142.xView ArticlePubMedGoogle Scholar
  23. Okamoto H, Tsuda F, Sakugawa H, Sastrosoewignjo RI, Imai M, Miyakawa Y, Mayumi M: Typing hepatitis B virus by homology in nucleotide sequence: comparison of surface antigen subtypes. J Gen Virol 1988,69(Pt 10):2575-83. 10.1099/0022-1317-69-10-2575View ArticlePubMedGoogle Scholar
  24. Goedel S, Rullkoetter M, Weisshaar S, Mietag C, Leying H, Boehl F: Hepatitis B virus (HBV) genotype determination by the COBAS AmpliPrep/COBAS TaqMan HBV Test, v2. J Clin Virol 2009, 45: 232-6. 10.1016/j.jcv.2009.05.021View ArticlePubMedGoogle Scholar
  25. Kiesslich D, Crispim MA, Santos C, Ferreira Fde L, Fraiji NA, Komninakis SV, Diaz RS: Influence of hepatitis B virus (HBV) genotype on the clinical course of disease in patients coinfected with HBV and hepatitis delta virus. J Infect Dis 2009, 199: 1608-11. 10.1086/598955View ArticlePubMedGoogle Scholar
  26. Chen M, Zhang D, Zhen W, Shi Q, Liu Y, Ling N, Peng M, Tang K, Hu P, Hu H, Ren H: Characteristics of circulating T cell receptor gamma-delta T cells from individuals chronically infected with hepatitis B virus (HBV): an association between V(delta)2 subtype and chronic HBV infection. J Infect Dis 2008, 198: 1643-50. 10.1086/593065View ArticlePubMedGoogle Scholar
  27. Tsai MC, Chen CH, Lee CM, Chen YT, Chien YS, Hung CH, Wang JH, Lu SN, Yen YH, Changchien CS, Hu TH: The role of HBV genotype, core promoter and precore mutations in advanced liver disease in renal transplant recipients. J Hepatol 2009, 50: 281-8. 10.1016/j.jhep.2008.09.013View ArticlePubMedGoogle Scholar
  28. Zumbika E, Ruan B, Xu CH, Ni Q, Hou W, Chen Z, Liu KZ: HBV genotype characterization and distribution in patients with HBV-related liver diseases in Zhejiang Province, P.R. China: possible association of co-infection with disease prevalence and severity. Hepatobiliary Pancreat Dis Int 2005, 4: 535-43.PubMedGoogle Scholar
  29. Manzini P, Girotto M, Borsotti R, Giachino O, Guaschino R, Lanteri M, Testa D, Ghiazza P, Vacchini M, Danielle F, Pizzi A, Valpreda C, Castagno F, Curti F, Magistroni P, Abate ML, Smedile A, Rizzetto M: Italian blood donors with anti-HBc and occult hepatitis B virus infection. Haematologica 2007, 92: 1664-70. 10.3324/haematol.11224View ArticlePubMedGoogle Scholar
  30. Bhatti FA, Ullah Z, Salamat N, Ayub M, Ghani E: Anti-hepatits B core antigen testing, viral markers, and occult hepatitis B virus infection in Pakistani blood donors: implications for transfusion practice. Transfusion 2007, 47: 74-9. 10.1111/j.1537-2995.2007.01066.xView ArticlePubMedGoogle Scholar
  31. Satake M, Taira R, Yugi H, Hino S, Kanemitsu K, Ikeda H, Tadokoro K: Infectivity of blood components with low hepatitis B virus DNA levels identified in a lookback program. Transfusion 2007, 47: 1197-205. 10.1111/j.1537-2995.2007.01276.xView ArticlePubMedGoogle Scholar
  32. Gerlich WH, Glebe D, Schuttler CG: Deficiencies in the standardization and sensitivity of diagnostic tests for hepatitis B virus. J Viral Hepat 2007,14(Suppl 1):16-21. 10.1111/j.1365-2893.2007.00912.xView ArticlePubMedGoogle Scholar
  33. Dorman KS: Identifying dramatic selection shifts in phylogenetic trees. BMC Evol Biol 2007,7(Suppl 1):S10. 10.1186/1471-2148-7-S1-S10PubMed CentralView ArticlePubMedGoogle Scholar
  34. Fares MA, Holmes EC: A revised evolutionary history of hepatitis B virus (HBV). J Mol Evol 2002, 54: 807-14. 10.1007/s00239-001-0084-zView ArticlePubMedGoogle Scholar
  35. Kawabe N, Hashimoto S, Harata M, Nitta Y, Murao M, Nakano T, Shimazaki H, Arima Y, Komura N, Kobayashi K, Yoshioka K: The loss of HBeAg without precore mutation results in lower HBV DNA levels and ALT levels in chronic hepatitis B virus infection. J Gastroenterol 2009, 44: 751-6. 10.1007/s00535-009-0061-7View ArticlePubMedGoogle Scholar
  36. Ntziora F, Paraskevis D, Haida C, Magiorkinis E, Manesis E, Papatheodoridis G, Manolakopoulos S, Beloukas A, Chryssoy S, Magiorkinis G, Sypsa V, Hatzakis A: Quantitative detection of the M204V HBV minor variants by amplification refractory mutation system real-time polymerase chain reaction (ARMS rt-PCR) combined with molecular beacon. J Clin Microbiol 2009, 47: 2544-50. 10.1128/JCM.00045-09PubMed CentralView ArticlePubMedGoogle Scholar
  37. Wang Z, Liu Z, Zeng G, Wen S, Qi Y, Ma S, Naoumov NV, Hou J: A new intertype recombinant between genotypes C and D of hepatitis B virus identified in China. J Gen Virol 2005, 86: 985-90. 10.1099/vir.0.80771-0View ArticlePubMedGoogle Scholar
  38. Yang J, Xing K, Deng R, Wang J, Wang X: Identification of Hepatitis B virus putative intergenotype recombinants by using fragment typing. J Gen Virol 2006, 87: 2203-15. 10.1099/vir.0.81752-0View ArticlePubMedGoogle Scholar

Copyright

© Hu et al; licensee BioMed Central Ltd. 2009

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.