Hepatitis B virus

Background

Microbiology

• Reverse-transcription double-stranded DNA (RT-dsDNA) virus
• Genotypes A through J vary in geographic distribution and clinical severity

Genotype	B	C	A	D	E-J
Clinical characteristics
Modes of transmission	Perinatal/vertical	Perinatal/vertical	Horizontal	Horizontal	Horizontal
Tendency of chronicity	Lower	Higher	Higher	Lower	No data
HBeAg positivity	Lower	Higher	Higher	Lower	No data
HBeAg seroconversion	Earlier	Later	Earlier	Later	No data
HBsAg seroclearance	More	Less	More	Less	No data
Histological activity	Lower	Higher	Lower	Higher	No data
Clinical outcomes
Response to interferon-α	Higher	Lower	Higher	Lower	Lower in G
Response to NRTIs	No significant differences				No data
Viroloical characteristics
Viral load	Lower	Higher	No data
Frequency of PC A1896 mutation	Higher	Lower	Lower	Higher	No data
Frequency of basal core promoter T1762/A1764 mutation	Lower	Higher	Higher	Lower	No data
Frequency of preS deletion utation	Lower	Higher	No data

Phases of Chronic Infection

• Phase 1: HBeAg + chronic infection (previously immune tolerant)
  • Viral replication including HBeAg without evidence of immune response
• Phase 2: HBeAg + chronic hepatitis (previously immune active)
  • Elevated liver enzymes and HBV DNA
• Phase 3: HBeAg – chronic infection (previously inactive carrier)
  • HBeAg clears and liver enzymes normalize, but ongoing low-level viral replication
• Phase 4: HBeAg – chronic hepatitis (previously HBeAg-negative chronic hepatitis)
  • Increasing viral load with fluctuating liver enzymes
• Phase 5: HBsAg negative
  • HBsAb positive or negative, other studies return to normal

Clinical Manifestations

Acute

• 75% are asymptomatic
• Symptoms range from self-resolving jaundice to fulminant liver failure in about 5%

Chronic

• Chronic hepatitis B begins as e antigen positive, usually with very high levels of HBV DNA and necroinflammation.
• Four types of chronic hepatitis B
  • Immunotolerant hepatitis B: HBV DNA levels (>20,000 IU/ml), HBeAg positive, with normal ALT
    • Common after vertical transmission and can persist for years before progressing to another form
  • HBeAg-positive immune-active chronic hepatitis B: HBsAg-positive, HBV DNA levels (>20,000 IU/ml), HBeAg positive, anti-HBe negative with elevated ALT
  • HBeAg-negative immune-active chronic hepatitis B: HBsAg-positive, HBV DNA levels (<20,000 IU/ml), HBeAg negative, anti-HBe positive, with elevated ALT
    • Results from anti-HBe seroconversion when a mutation decreases HBeAg expression
  • Inactive hepatitis B (healthy carrier): HBsAg for > 6 months without any evidence of necroinflammation and HBV DNA levels are < 2,000 IU/m
    • May still transmit it, but overall a better prognosis
• Hepatocellular carcinoma is a risk in chronic hepatitis B, but especially in certain populations including cirrhosis
• Polyarteritis nodosa
• Membranous nephropathy or membranoproliferative glomerulonephritis
• Sensorimotor neuropathy
• Sjogren syndrome

Investigations

• Hepatitis B serology

Management

Acute

• Supportive care

Chronic

• Diagnosed with HBsAg present for 6 or more months; HBV-DNA is variable
• Can be HBeAg positive or negative, with generally higher HBV DNA levels in HBeAg-positive patients
• ALT can be normal or elevated
• Liver biopsy shows chronic hepatitis and variable necroinflammation or fibrosis
• Bloodwork should be monitored every 3 months looking at ALT and HBV DNA to assess for indications for treatment

Indications for Treatment

• The goal of treatment is to decrease the risk of cirrhosis and hepaticellular carcinoma, so is generally reserved for those at higher risk of these sequelae
  • The risk is generally higher with higher HBV-DNA and HBsAg titres, and possibly higher ALT
• The decision to treat requires consideration of patient age, viral load, HBeAg, and evidence of significant liver disease (i.e. persistent ALT elevation, fibrosis or inflammation on biopsy, or non-invasive assessment of hepatic fibrosis)
• Treatment is generally indicated when:
  • HBV DNA >2000 IU/mL and ALT is elevated for 3-6 months (regardless of HBsAg)
  • Evidence of significant hepatic fibrosis (even if HBV DNA <2000 IU/mL and ALT normal)
  • Cirrhosis and detectable HBV DNA
• Treatment may also be indicated for other patients with elevated HBV DNA regardless of ALT level
  • If inactive for a year (e.g. HBeAg negative, HBeAb positive, normal ALT, and HBV DNA <2000 IU/mL), then can back off to q6-12mo

Treatment Regimens

• Choose one of pegylated-interferon (48 weeks), tenofovir (until 12 months post-HBeAg conversion), or entecavir (until 12 months post-HBeAg conversion)
  • Tenofovir or entecavir are preferred for treatment-naïve patients
  • Peg-IFN contraindicated in autoimmune disorders, uncontrolled psychiatric disease, cyptopenia, severe cardiac disease, uncontrolled seizures, and decompensated cirrhosis
  • Peg-IFN preferred in lamivudine resistance
  • Peg-IFN avoided if HBeAg negative
  • Tenofovir preferred in cirrhosis, ± entecavir
  • Tenofovir is safe in pregnancy
  • Entecavir avoided in lamivudine resistance
• Duration depends on what stage is being treated
  • HBeAg-positive patients
    • Peg-IFN for 48 weeks; however, if HBsAg >20000 IU/mL at week 24 then treatment should be stopped for futility
    • Tenofovir or entecavir for at least 12 months after HBeAg seroconversion (Ag to Ab), or until HBsAg loss
  • HBeAg-negative patients, or patients with cirrhosis or HCC, tenofovir or entecavir is continued until HBsAg loss
• Continue HCC surveillance regardless of treatment

Drug	Dose	Duration
		HBeAg positive	HBeAg negative	Cirrhosis	HCC
pegylated interferon α-2a	180 μg SC weekly	48 weeks	avoid
tenofovir disoproxil fumarate	300 mg PO daily	at least 12 months after HBeAg seroconversion, or until HBsAg loss	until HBsAg loss
tenofovir alafenamide	25 mg PO daily
entecavir	0.5 mg PO daily
lamivudine	do not use
adefovir	do not use

Inactive Chronic Hepatitis B

• Defined by HBeAg-negative, anti-HBeAb-positive, normal ALT, and HBV DNA <2000 IU/mL
• Monitor ALT q3mo for 1 year, then q6-12mo
• If ALT rises, check HBV-DNA and HBsAg for activity

HCC screening

• Screen if HBsAg-positive with cirrhosis, or HBsAg-positive at higher risk (Asian men >40yrs, black men >40yrs, Asian women >50yrs, family history, HDV coinfection)
• First-line is ultrasound every 6 months
• Second-line is AFP levels every 6 months

Prophylaxis in Immunosuppression

• Risk stratify based on type of immune suppression and serologic status
  • High-risk (>10%):
    • HBsAg positive, or HBsAg negative but HBcAb positive, plus B-cell depletion such as rituximab and ofatumumab
    • HBsAg positive, plus anthracyclines (doxorubicin, epirubicin), prednisone >10-20 mg/day for ≥4 weeks
  • Moderate-risk (1-10%)
    • HBsAg positive, or HBsAg negative but HBcAb positive, plus TNF-α inhibitors (etanercept, adalimumab, certolizumab, certolizumab, infliximab), other cytokine or integrin inhibitors (abatacept, ustekinumab, natalizumab, vedolizumab), and tyrosine kinase inhibitors (imatinib, nilotinib, ibrutinib)
    • HBsAg positive: prednisone <10 mg/day for ≥4 weeks
    • HBsAg negative but HBcAb positive: prednisone >10-20 mg/day for ≥4 weeks, antracycline derivatives (doxorubicin and epirubicin)
  • Low-risk (<1%)
    • HBsAg positive, or HBsAg negative but HBcAb positive, plus traditional immunosuppressants (azathioprine, 6-MP, methotrexate)
    • HBsAg negative or HBcAb positive, plus prednisone <10 mg/day for ≥4 weeks
• Concern especially with chronic steroids and rituximab
• Can have the following effects
  • Asymptomatic HBV DNA and ALT
  • Hepatic failure
  • Death
• If ≥7.5mg/d should be screened
  • HBsAg +/- HBcAb if they're adding a second agent (rituximab, TNF-alpha inhibitors, or other)
  • Refer to Hepatology or Infectious Diseases
• Prophylaxis with lamivudine until 6 months after chemotherapy

Further Reading

• Update on prevention, diagnosis, and treatment of chronic hepatitis B: AASLD 2018 hepatitis B guidance
• Hepatitis B virus genotypes: Global distribution and clinical importance. World J Gastroenterol. 2014;20(18):5427–5434. doi: 10.3748/wjg.v20.i18.5427