Clinical Testing and Diagnosis of HBV, HCV and HIV

HBV, HCV and HIV?are three distinct viruses (DNA virus, RNA virus and?retro-virus, respectively) with distinct differences—including affected organ systems, life cycles and host cell integration. There are also several similarities however—such as their main modes of transmission and favorable treatment outcomes with antiviral drugs. The detection of HIV, HCV and HBV should at least include the scenarios such as post-exposure, blood donation, pre-operative screening, prenatal & postnatal care (if at risk), etc. Here below introduces prevalence, transmission, diagnosis and treatment of HIV, HCV and HBV.

Hepatitis B

WHO estimates that 254 million people were living with chronic hepatitis B infection in 2022, with 1.2 million new infections each year. In 2022, hepatitis B resulted in an estimated 1.1 million deaths, mostly from cirrhosis and hepatocellular carcinoma (primary liver cancer).

Approximately 50%–70% of people with acute hepatitis B are asymptomatic. Without testing, people with HBV infection can unknowingly transmit the virus to others. In severe conditions (yellowing of the skin and eyes, dark urine, etc.), acute hepatitis can lead to liver failure, which can be life-threatening. Although most people will recover from acute illness. If hepatitis B virus is not eliminated within 6 months, it may develop into chronic hepatitis B, leading to substantial morbidity and mortality.

The hepatitis B virus (HBV) is a small DNA virus with unusual features similar to retroviruses (Fig 1). The infectious HBV virion (Dane particle) has a spherical, double-shelled structure 42 nm in diameter, consisting of a lipid envelope containing HBsAg that surrounds an inner nucleocapsid composed of hepatitis B core antigen (HBcAg) complexed with virally encoded polymerase and the viral DNA genome. HBeAg (a variant of the HBcAg) is important for the immune evasion properties of HBV. The genome of HBV is a partially double-stranded circular DNA of about 3.2 kilobase (kb) pairs. The viral polymerase is covalently attached to the 5′end of the minus strand.

The typical course of acute hepatitis B is shown in Fig. 2. HBV DNA followed shortly afterward by HBsAg?and HBeAg?are the first viral markers detected in serum, their persistence is a marker of chronicity. HBeAg correlates with the presence of high levels of HBV replication and infectivity. Within a few weeks of appearance of viral markers, HBeAg is usually cleared early during acute hepatitis B, at the peak of clinical illness, whereas HBsAg and HBV DNA usually persist in the serum for the duration of clinical symptoms and are cleared with recovery.

Antibodies to the HBV proteins arise in different patterns during acute hepatitis B. Anti-HBc?generally appears shortly before onset of clinical illness. Anti-HBe?usually appears shortly after clearance of HBeAg, often at the peak of clinical illness. Thus, loss of HBeAg and appearance of anti-HBe is a favorable serological marker during acute hepatitis B, indicating the initiation of recovery.

Anti-HBs?arises late during infection, usually during recovery or convalescence after clearance of HBsAg. Anti-HBs persists after recovery, being the antibody associated with immunity against HBV. However, still 10%-15% of patients who recover from hepatitis B do not develop detectable anti-HBs and have anti-HBc alone as a marker of previous infection. For this reason, anti-HBc testing is the most reliable means of assessing previous infection with HBV, whereas anti-HBs testing is used to assess immunity and response to HBV vaccine. The serological manifestations of hepatitis B infection can be found in Table 1.

Table 1. Serological manifestations of different courses during hepatitis B infection.

Hepatitis C

Globally, an estimated 50 million people have chronic hepatitis C virus infection, with about 1.0 million new infections occurring per year. WHO estimated that in 2022, approximately 242 000 people died from hepatitis C, mostly from cirrhosis and hepatocellular carcinoma (primary liver cancer).

The hepatitis C virus is a bloodborne virus. It is most commonly transmitted through contact with infected blood, HCV can be passed through mother to child and via sexual practices but these modes of transmission are less common.

Acute HCV infections are usually asymptomatic. When symptoms do appear, they may include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine and yellowing of the skin or eyes (jaundice). Around 30% of infected persons spontaneously clear the virus within 6 months of infection without any treatment. The remaining 70% of persons will develop chronic HCV infection. Of those with chronic HCV infection, the risk of cirrhosis ranges from 15% to 30% within 20 years.

HCV infection is diagnosed in 2 steps:

1. Serology testing for anti-HCV identifies people who have been infected with the virus.

2. If positive for anti-HCV, a nucleic acid test for HCV RNA is needed to confirm chronic infection and the need for treatment. This test is important because about 30% of people infected with HCV spontaneously clear the infection by a strong immune response without the need for treatment. Although no longer infected, they will still test positive for anti-HCV.

HIV

Human immunodeficiency virus (HIV) is a virus that attacks the body’s immune system. Acquired immunodeficiency syndrome (AIDS) occurs at the most serious stage of infection. In this stage, these illness (certain cancers and some neurological conditions) takes advantage of your weakened immune system which makes you extreme susceptible. ?

WHO estimates there were an estimated 39.9 million people living with HIV at the end of 2023, 65% of whom are in the African Region. In 2023, an estimated 630 000 people died from HIV-related causes and an estimated 1.3 million people acquired HIV.

HIV is a type of retrovirus, which is roughly spherical with a diameter of about 120 nm, around 100,000 times smaller in volume than a red blood cell. It is composed of two copies of single-stranded RNA that codes for the virus' nine genes enclosed by a conical capsid composed of 2,000 copies of the viral protein p24 (Fig. 3). As the most abundant protein of HIV, detection of p24 protein's antigen can be used to identify the presence of HIV in a person's blood and diagnose HIV/AIDS.

The virus can remain dormant in the human body for up to ten years after primary infection; during this period the virus does not cause symptoms. HIV-1 is more virulent and infective than HIV-2, and is the cause of the majority of HIV infections globally. HIV-2, is largely confined to West Africa.

Following an exposure that leads to infection, there is a variable amount of time called the eclipse period in which no existing diagnostic test is capable of detecting HIV (Fig. 4). Times to reactivity for each type of diagnostic test are depicted below the graph, from the earliest (nucleic acid amplification test, NAAT) to the latest (IgG sensitive assay).

The CDC and APHL HIV testing algorithm utilizes an HIV-1/2 antigen-antibody immunoassay as the initial test, with positive test results followed by an HIV-1/2 differentiation assay (Fig. 5). Specimens that were repeatedly reactive by the fourth-generation assay and yet negative by the HIV-1/2 differentiation procedure were to be tested using an HIV-1 RNA qualitative PCR assay to determine if HIV-1 was present, causing a positive antigen result on the fourth-generation screening test.?

The Treatment of HBV, HCV and HIV

HBV Infection: Chronic but Preventable Disease

Current treatment strategies do not allow complete viral eradication in HBV infection. An effective vaccination against HBV has been supplied since the early 1980s. Approximately 84% of children worldwide (92% in the Asian region) received three doses of hepatitis B vaccine and are thus probably protected from HBV infection for life.

HCV: On the Path Toward Elimination

Interferon was the first drug used to treat the infection and, with addition of ribavirin, cure rates (sustained virologic response, SVR) around 54–56% were achieved. However, problems come from reinfection that can occur even after a successful treatment (as treatment does not result in any protective HCV-specific immunity). At this time, no effective vaccination is available for hepatitis C.

HIV: On Our Way to Global Control

WHO and UNAIDS have recommended Treatment as Prevention for HIV to be widely implemented. It has been demonstrated that effective treatment suppresses the viral load, and this correlates with a significantly decreased chance of transmission to uninfected individuals by Antiretroviral therapy.

Another important step toward HIV control is targeted provision of pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP). It has been demonstrated that taking tenofovir disoproxil fumarate/emtricitabine every day or “on demand” before high-risk exposure is effective in preventing HIV infection in people who have high-risk sexual contacts or in people who inject drugs (PWID) who share needles.

Mother-to-child transmission is another crucial aspect as it can be nearly fully prevented if both the mother and infant are provided with antiretroviral drugs as early as possible in pregnancy and during the period of breastfeeding.

YHLO’s Solution to Evaluate 3H?Condition

YHLO’s blood bank panel supports the diagnosis of HBV, HCV and HIV. YHLO has successfully obtained its first IVDR Class D CE certification for our HBeAg, more certificates are coming. Additionally, our infection panel cares about other infective diseases such as EBV, Respiratory disease, etc.

References:

[1] Centers for Disease Control and Prevention (CDC). Testing for HCV infection: an update of guidance for

clinicians and laboratorians. MMWR Morb Mortal Wkly Rep. 2013;62:362-5.

[2] Centers for Disease Control and Prevention and Association of Public Health Laboratories. 2018 Quick

reference guide: Recommended laboratory HIV testing algorithm for serum or plasma specimens.

Published January 27, 2018

[3] Hurt, Christopher B et al. “Selecting an HIV Test: A Narrative Review for Clinicians and Researchers.”

Sexually transmitted diseases vol. 44,12 (2017): 739-746.

[4] Leoni, Maria C et al. “HIV, HCV and HBV: A Review of Parallels and Differences.” Infectious diseases

and therapy vol. 7,4 (2018): 407-419.

[5] Liang, T Jake. “Hepatitis B: the virus and disease.” Hepatology (Baltimore, Md.) vol. 49,5 Suppl (2009):

S13-21.

[6] WHO Global hepatitis report 2024: action for access in low- and middle-income countries