Serology of Viral Infections Practice Flashcards

These flashcards cover the structure, immune response, and clinical serology of various viral infections including Hepatitis A-E, EBV, CMV, VZV, HTLV, and HIV as presented in the MEDL 315L lecture notes.

What are the three main components of a virus mentioned in the lecture?

Core DNA or RNA, a protein coat (capsid), and an outer glycolipid/protein envelope (host derived).

By what two methods are new viral particles released from a host cell?

Cell lysis or “budding” off the cell surface.

What is the primary role of antibodies in neutralizing viruses?

Preventing attachment and penetration.

Which specific effector cells and proteins destroy virus-infected cells by inducing cell death?

Cytotoxic T cells using perforin and proteases (granzymes).

What does ADCC stand for in the context of the host immune response?

Antibody-dependent cell-mediated cytotoxicity.

How does Hepatitis C Virus (HCV) evade the host immune system?

By blocking the degradation of viral nucleic acid.

Which viruses are noted for their ability to suppress the host immune system?

CMV, HIV, and EBV.

In adult laboratory testing, what does the presence of specific IgM suggest?

Current or recent infection.

In newborn laboratory testing, what does the presence of specific IgG indicate?

The antibody is maternally derived.

Which two primary hepatitis viruses are transmitted via the fecal-oral route?

Hepatitis A virus (HAV) and Hepatitis E virus (HEV).

What are the three parenteral route hepatitis viruses?

Hepatitis B virus (HBV), Hepatitis D virus (HDV), and Hepatitis C virus (HCV).

What serological marker combination indicates immunity to Hepatitis A?

A (+) total anti-HAV along with a (–) IgM anti-HAV.

How are HEV-3 and HEV-4 genotypes mainly transmitted?

Consumption of infected pork.

What percentage of infected infants develop chronic Hepatitis B infection?

$$90\%$$

What is the first serological marker to appear in an active HBV infection?

Hepatitis B surface antigen (HBsAg).

Which HBV marker indicates a high degree of infectivity and active viral replication?

Hepatitis Be antigen (HBeAg).

What does the presence of IgM anti-HBc indicate in HBV serology?

Current or recent acute infection; it also detects the “core window.”

Which antibody marker indicates immunity to Hepatitis B?

Anti-HBs (Surface antibody).

What is the specific requirement for Hepatitis D Virus (HDV) to infect a host?

It requires the presence of HBV.

What serological markers define an HDV superinfection in chronic HBV carriers?

(+) for anti-HDV and IgG anti-HBc.

Which HCV genotype is responsible for $70\%$ of infections in the US?

Genotype 1.

What is the preferred screening and diagnostic marker for Hepatitis C?

Anti-HCV IgG.

To which specific receptor on B cells does Epstein-Barr Virus (EBV) bind?

CD21 (C3d receptor).

What are heterophile antibodies in the context of EBV?

Antibodies that react with horse, sheep, and bovine RBCs.

What percentage of lymphocytes and atypical lymphocytes are typically seen in IM laboratory findings?

$>50\%$ lymphocytes and $>10\%$ atypical lymphocytes.

Which EBV antibody is considered the best marker for acute Infectious Mononucleosis (IM)?

IgM anti-VCA ( viral capsid antigen).

When do anti-EBNA (EBV nuclear antigens) antibodies typically appear?

During convalescent IM.

What specific malignancy is associated with EBV and common in AIDS patients?

CNS lymphomas.

What is a major complication for CMV negative transplant patients receiving an organ?

High risk of graft-versus-host-disease (GVHD).

Where does Varicella-Zoster Virus (VZV) remain in a lifelong latent state?

Dorsal root, autonomic, and cranial ganglia.

What is the main method to detect VZV DNA in clinical samples?

Real-time PCR.

What is the genus and family of the Rubella virus?

Genus: Rubrivirus; Family: Togaviridae.

What fatal, degenerative CNS disease is caused by the Rubeola (Measles) virus?

Subacute sclerosing panenchphalitis (SSPE).

What is the clinical hallmark of a Mumps infection?

Parotitis.

Which human retrovirus is associated with adult T-cell leukemia/lymphoma?

Human T-Cell Lymphotropic virus (HTLV-I).

What is the major structural difference between the HIV core and its envelope?

The core consists of a protein coat (capsid) with two copies of ssRNA, while the outer envelope is a lipid bilayer with glycoproteins.

Which HIV-1 group is responsible for nine subtypes (A, B, C, D, F, G, H, J, K)?

Group M.

To which host cell protein does the HIV gp120 protein bind?

CD4.

Which chemokine coreceptor is required for HIV to infect T lymphocytes?

CXCR4.

Which chemokine coreceptor is required for HIV to infect macrophages?

CCR5.

When is HIV DNA referred to as a “provirus”?

When it is integrated into the host genome.

How does HIV protect itself from recognition by Cytotoxic T cells (CTLs)?

By downregulating the expression of MHC-I molecules on infected host cells.

What characterizes a “long-term nonprogressor” (LTNP) in HIV infection?

Asymptomatic for more than $10$ years without therapy, with normal or mildly decreased CD4 counts and low viral load.

What defines Stage 3 HIV infection (AIDS) in terms of CD4 count?

$$\leq 200\,Cell/\mu L$$

What is the CD4 count range for Stage 2 HIV staging?

$$200-499\,Cell/\mu L$$

What is the definition of Stage 0 HIV infection?

Early infection with one positive HIV test followed by a negative or indeterminate test within $6$ months.

What does the 2014 CDC recommended fourth-generation combination immunoassay detect?

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

What is the estimated laboratory detection time for HIV after exposure using the current algorithm?

$15-17$ days.

In the previous testing algorithm, which three bands were required for a positive Western blot?

p24, gp41, and gp120/gp160.

What is the purpose of Pre-exposure prophylaxis (PrEP)?

To prevent HIV infection in high-risk individuals.

Which laboratory method is used for CD4 T-cell enumeration?

Flow cytometry.

What T-cell ratio is characteristic of untreated HIV individuals?

A CD4 T:CD8 T-cell ratio less than $1:1$.

When can HIV RNA first be detected in patient plasma after infection?

$11$ days.

What are two common methods for measuring quantitative HIV viral load?

qPCR and branched chain DNA (bDNA).

What do genotype resistance assays detect in HIV monitoring?

Mutations in reverse transcriptase and protease genes.

How are results reported in an HIV genotype resistance assay?

Resistance, possible resistance, or no evidence of resistance.

What is measured in an HIV phenotype resistance assay?

The ability of HIV from clinical samples to grow in the presence of antiretroviral drugs.

Why is serologic testing unreliable for infants less than 18 months of age?

Maternal antibodies in infant serum complicate the results.

What is the preferred molecular method for diagnosing HIV in infants?

Qualitative HIV-1 DNA PCR.

At what age range is serologic testing used to confirm an HIV diagnosis in children born to HIV-positive mothers?

$12$ to $18$ months.