Viral Serology: Hepatitis Markers and HIV Testing

What is hepatitis?

Inflammation of the liver caused by primary hepatitis viruses, ionizing radiation, chemicals, or autoimmune diseases.

What are the common signs and symptoms of hepatitis?

Hepatomegaly, jaundice, dark urine, and light feces.

What laboratory findings are associated with hepatitis?

Elevated bilirubin and ALT levels.

How is Hepatitis A (HAV) transmitted?

Fecal-oral route, close person-to-person contact, or ingestion of contaminated food or water.

What is the incubation period for Hepatitis A?

28 days.

What is the disease course of Hepatitis A?

Acute and self-limiting; there is no carrier state or chronic stage.

What is the primary laboratory diagnosis for Hepatitis A?

Liver Function Test (ALT), Total Bilirubin, and Antibodies to HAV (EIA and RIA).

What is the marker of acute Hepatitis A?

IgM Anti-HAV.

What does IgG Anti-HAV indicate?

Result of natural infection or immunization.

What are the transmission routes for Hepatitis B (HBV)?

Sexual contact, blood, parenteral, and perinatal/vertical.

What is the incubation period for Hepatitis B?

30 to 180 days.

What are the possible disease courses for Hepatitis B?

Acute, chronic, or fulminant; may also be a chronic asymptomatic carrier.

What is the first serological marker to appear in Hepatitis B?

Hepatitis B Surface Antigen (HBsAg).

What does HBeAg indicate?

Active replication of the virus and a high degree of infectivity.

What does IgM Anti-HBc indicate?

Current or recent infection; detects the 'Core Window Period'.

What is the significance of IgG Anti-HBc?

Persists for the lifetime of the individual and serves as a lifelong marker of HBV infection.

What is the most frequent cause of chronic liver infection?

Hepatitis C (HCV).

What is the incubation period for Hepatitis C?

7 weeks (range is 2 to 30 weeks).

What is the standard treatment for Hepatitis C?

Combination of pegylated interferon-a (PEG IFN-a) and ribavirin.

What family does Hepatitis C belong to?

FLAVIVIRIDAE - HEPACIVIRUS.

What is the primary cause of liver transplantation?

Chronic liver infection due to Hepatitis C.

What is the role of hepatitis B immune globulin (HBIG)?

Administered within 24 hours of exposure to HBsAg-positive blood to nonimmunized patients.

What is the significance of Anti-HBs?

Appears during recovery from acute hepatitis B and persists for years.

What indicates a favorable diagnosis in Hepatitis B?

Anti-HBe marker.

What is the primary laboratory test for diagnosing Hepatitis B?

Serum HBsAg.

What is the marker for convalescence in Hepatitis B?

Anti-HBe.

What is the significance of HBsAg?

Indicates active HBV infection, either acute or chronic.

What does the presence of Anti-HBs indicate?

Immunity to Hepatitis B, either through recovery or vaccination.

What is Anti-HCV IgG commonly detected by?

Sensitive EIAs or CLIAS using recombinant and synthetic antigens.

When do HCV antibodies become detectable after exposure?

8 to 10 weeks.

What does detectable HCV RNA indicate?

Current hepatitis C infection.

What is the purpose of measuring viral load in hepatitis C?

To monitor the effectiveness of therapy and determine HCV genotype.

What testing method is recommended by the CDC for HCV confirmation?

Nucleic acid testing (NAT) for HCV RNA.

What is Hepatitis D also known as?

Delta Hepatitis.

What type of virus is Hepatitis D?

Unclassified, ssRNA virus.

How can Hepatitis D be transmitted?

Through sexual contact, body fluids, or perinatal/vertical transmission.

What are the two ways Hepatitis D infection can occur?

As co-infection with HBV or as a superinfection in chronic HBV carriers.

Which tests are available for HDV detection?

HDV antibodies via ELISA and HDV RNA via RT-PCR.

What does IgM Anti-HDV indicate?

Acute or chronic hepatitis D.

What does IgG Anti-HDV indicate?

Recovery or chronic hepatitis D.

What does HDV RNA indicate?

Active HDV infection.

What is the transmission route for Hepatitis E?

Fecal-oral route.

What is the incubation period for Hepatitis E?

2 to 6 weeks.

What is the disease course for Hepatitis E?

Self-limiting illness with recovery occurring by 4 to 6 weeks.

What are the four genotypes of Hepatitis E?

HEV1, HEV2, HEV3, and HEV4.

What is a significant risk associated with Hepatitis E?

High rate of mortality in pregnant women.

What tests are available for HEV detection?

IgM Anti-HEV, IgG Anti-HEV, and HEV RNA.

What does IgM Anti-HEV indicate?

Current or new hepatitis E.

What does IgG Anti-HEV indicate?

Current or former hepatitis E.

What does HEV RNA indicate?

Current HEV infection.

What is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS)?

Human Immunodeficiency Virus (HIV).

How is HIV primarily transmitted?

Through intimate sexual contact and contact with blood or other body fluids.

What are the two main serotypes of HIV?

HIV-1 and HIV-2.

Which subtype of HIV is most predominant worldwide?

Subtype C.

Which subtype of HIV is most prevalent in the US, Europe, and Australia?

Subtype B.

What are the core components of HIV?

Structural genes including gag, pol, and env.

What is the function of accessory/regulatory genes in HIV?

To control and enhance the virus's replication.

What does the gag gene code for in HIV?

Proteins that form the inner shell of the virus, such as p55, p24, p17, p9, and p6.

What is the function of the pol gene in HIV?

It codes for viral enzymes essential for replication, including reverse transcriptase (p66/p51), integrase (p31), and protease (p10).

What do the env genes encode?

Viral envelope proteins, including the gp160 precursor, which is cleaved into gp120 and gp41.

What is the role of gp120 in HIV?

It binds to the CD4 antigen receptor on host cells, facilitating viral entry.

What are the co-receptors used by HIV to enter host cells?

CXCR4 for T lymphocytes (T-tropic or X4 strains) and CCR5 for macrophages (M-tropic or R5 strains).

What happens after HIV binds to co-receptors?

The gp41 glycoprotein changes shape, mediating the fusion of the viral envelope with the host cell membrane.

What occurs during reverse transcription in the HIV lifecycle?

The enzyme reverse transcriptase creates double-stranded DNA from the viral RNA genome.

What is a provirus in the context of HIV?

Viral DNA integrated into the host cell's genome, which can remain latent.

What triggers viral gene expression in HIV-infected cells?

Activation of the infected host cell by an antigen or cytokines.

What is the result of viral replication in the HIV lifecycle?

Viral particles assemble and bud from the host cell membrane, acquiring their envelope.

What is the first stage of HIV infection?

Stage 1: Acute HIV Infection, characterized by a rapid burst of viral replication and flu-like symptoms.

What happens to CD4 T-cell counts during acute HIV infection?

There is a temporary decrease in peripheral blood CD4 T-cell count.

What characterizes Stage 2 of HIV infection?

Clinical latency with stable CD4 counts, but the virus remains active in lymphoid tissues.

What defines Stage 3 of HIV infection (AIDS)?

Profound immunosuppression, very low CD4 T-cell counts, and the presence of opportunistic infections.

What is the CD4 count threshold for Stage 3 HIV infection?

Less than 200 cells/uL.

When do antibodies to HIV typically become detectable?

About 6 weeks after primary infection.

What is the normal CD4+ count range in healthy individuals?

450 to 1,500 cells/uL.

What is the normal CD4+:CD8+ ratio in healthy individuals?

2:1.

How does the CD4+:CD8+ ratio change in HIV infection?

It can drop to 1:2 or 0.5:1.

What happens to viral replication after the host's immune response develops?

Viral replication slows down as the immune system keeps the virus in check.

What is the significance of the p24 antigen in HIV infection?

It indicates an initial burst of viral replication and can be detected in the laboratory.

What are the first antibodies produced in response to HIV?

Antibodies against the gp41 transmembrane glycoprotein.

What is the role of regulatory genes in HIV?

They control the production of other viral proteins, enhance infectivity, and help the virus evade the immune system.

What are Long-Term Nonprogressors (LTNP) in HIV?

Individuals who remain asymptomatic for over 10 years with stable CD4 counts and low viral loads without therapy.

What is the process of maturation in HIV?

Precursor proteins are cleaved by viral protease into mature proteins in the final virus particles.

What is the role of the chemokine co-receptors in HIV entry?

They are necessary for the virus to enter host cells after initial binding to CD4.

What is the significance of the gp160 precursor protein?

It is cleaved into gp120 and gp41, which are crucial for viral attachment and entry.

What happens during the budding process of HIV?

Viral particles acquire their envelope and are released from the host cell.

What is the CD4 count listed for Stage 3 HIV?

A CD4 count of less than 200 cells/mm³.

How do viremia and CD4 counts change during acute infection?

During acute infection, viremia is high and CD4 counts drop.

What is the standard screening test for HIV?

ELISA (Enzyme-Linked Immunosorbent Assay).

What is the gold standard confirmatory test for HIV?

Western Blot.

What do the first-generation ELISA tests detect?

Antibodies to only HIV-1.

What improvement did second-generation ELISA tests provide?

They detected antibodies to both HIV-1 and HIV-2 with improved specificity and sensitivity.

What is the principle behind third-generation ELISA tests?

They use a sandwich technique to detect antibodies in patient serum.

What does the fourth-generation ELISA test detect?

HIV-1 antibodies, HIV-2 antibodies, and p24 antigen.

What is unique about fifth-generation ELISA tests?

They can differentiate between HIV-1 and HIV-2 infections.

What is a positive result criterion for Western Blot?

At least two out of three bands: p24, gp41, and gp120/gp160 must be present.

What does an indeterminate result in Western Blot testing indicate?

Some bands are present, but criteria for a positive result are not met.

What is seroconversion?

The change from antibody negative to antibody positive in response to HIV infection.

What factors can lead to a false negative HIV test result?

Heat inactivation of serum, recent exposure to certain vaccines, and testing before seroconversion.

What is the purpose of qualitative nucleic acid tests (NATs) in HIV testing?

To detect the presence of HIV RNA or DNA in the blood.

What is the role of drug resistance testing in HIV management?

To determine if the HIV strain is resistant to specific antiretroviral medications.