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Questions and Answers
Which of the following mechanisms does Human Cytomegalovirus (CMV) utilize to evade the host's immune response, specifically targeting MHC class I presentation?
Which of the following mechanisms does Human Cytomegalovirus (CMV) utilize to evade the host's immune response, specifically targeting MHC class I presentation?
- CMV directly inhibits the production of cytokines, thus preventing the activation of cytotoxic T lymphocytes (CTLs).
- CMV produces its own microRNAs to target and degrade host cell mRNA for class I MHC proteins, preventing their translation. (correct)
- CMV increases the stability of the MHC class I molecule and viral peptide complex, promoting increased presentation of viral antigens.
- CMV enhances the expression of MHC class II molecules to divert immune responses.
In the context of congenital CMV infection, what is the underlying mechanism that leads to the development of congenital abnormalities, particularly mental retardation, in affected infants?
In the context of congenital CMV infection, what is the underlying mechanism that leads to the development of congenital abnormalities, particularly mental retardation, in affected infants?
- CMV primarily infects maternal tissues, leading to the release of teratogenic factors that disrupt fetal development remotely.
- CMV triggers an overproduction of growth hormones in the fetus, causing disproportionate growth and developmental abnormalities.
- CMV directly stimulates rapid cell proliferation in the developing fetal brain, leading to abnormal neuronal network formation.
- CMV infection leads to the death of precursor cells in the developing fetus, disrupting normal organogenesis and neurological development. (correct)
A newborn presents with microcephaly, jaundice, and a purpuric rash resembling 'blueberry muffin' lesions. Serological tests confirm a congenital CMV infection. Which of the following pathophysiological processes is most directly responsible for the purpuric lesions observed in this infant?
A newborn presents with microcephaly, jaundice, and a purpuric rash resembling 'blueberry muffin' lesions. Serological tests confirm a congenital CMV infection. Which of the following pathophysiological processes is most directly responsible for the purpuric lesions observed in this infant?
- Direct viral infection of dermal cells leading to localized necrosis and hemorrhage.
- Thrombocytopenia resulting from CMV infection of megakaryocytes and impaired platelet production. (correct)
- Immune complex deposition in small blood vessels, triggering complement activation and vasculitis.
- Viral-induced inflammation causing increased vascular permeability and subsequent leakage of erythrocytes into the skin.
An immunocompromised patient with a history of CMV retinitis is being treated with antiviral medications. Despite initial improvement, the patient's condition worsens. Which of the following mechanisms would most likely explain the treatment failure?
An immunocompromised patient with a history of CMV retinitis is being treated with antiviral medications. Despite initial improvement, the patient's condition worsens. Which of the following mechanisms would most likely explain the treatment failure?
Which of the following diagnostic methods is most effective in differentiating between a primary CMV infection and a recurrent infection in an immunocompetent individual?
Which of the following diagnostic methods is most effective in differentiating between a primary CMV infection and a recurrent infection in an immunocompetent individual?
What is the most likely reason for the persistence of CMV in the kidney for extended periods?
What is the most likely reason for the persistence of CMV in the kidney for extended periods?
Why is CMV infection more likely to cause severe symptoms and complications in transplant recipients?
Why is CMV infection more likely to cause severe symptoms and complications in transplant recipients?
What is the significance of the 'owl's eye' inclusion in the context of CMV diagnosis?
What is the significance of the 'owl's eye' inclusion in the context of CMV diagnosis?
What is the rationale for limiting CMV treatment to immunocompromised patients?
What is the rationale for limiting CMV treatment to immunocompromised patients?
How do microRNAs produced by CMV contribute to immune evasion?
How do microRNAs produced by CMV contribute to immune evasion?
Flashcards
Human Cytomegalovirus (CMV)
Human Cytomegalovirus (CMV)
A double-stranded, enveloped linear DNA virus belonging to the Herpesviridae family, Beta-herpesvirinae subfamily.
Cytomegalic Inclusion Disease
Cytomegalic Inclusion Disease
In newborns, a condition caused by cytomegalovirus, characterized by enlarged cells with intranuclear inclusions.
CMV Symptoms
CMV Symptoms
Most adults and children are asymptomatic, but immunocompromised individuals will show more severe symptoms.
Symptoms of Congenital CMV
Symptoms of Congenital CMV
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Histological Diagnosis of CMV
Histological Diagnosis of CMV
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Treatment for CMV
Treatment for CMV
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CMV Immune Evasion
CMV Immune Evasion
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CMV Transmission
CMV Transmission
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CMV in Immunocompromised Patients
CMV in Immunocompromised Patients
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Study Notes
- Human Cytomegalovirus (CMV) is a double-stranded enveloped linear DNA virus.
- CMV belongs to the Herpesviridae family and the Betaherpesvirinae subfamily.
- Adults and children are usually asymptomatic unless immunocompromised.
- CMV can remain latent primarily in monocytes and reactivate when cell-mediated immunity decreases.
- CMV can persist in kidneys for years.
Symptoms of CMV
- Microcephaly (small head size).
- Long eyelashes and upturned nose
- Distinctive ears and retrognathia (overbite)
- Short neck
- Seizures and deafness
- Jaundice and purpura, resembling blueberry muffin lesions due to thrombocytopenia
- Thrombocytopenia and hepatosplenomegaly
Prevalence and Impact
- CMV is a leading cause of mental retardation in the U.S.
- It causes congenital abnormalities and is the most common cause of such abnormalities in the U.S.
- Primary infection during the first trimester of pregnancy causes congenital abnormalities.
- Infected infants excrete CMV in urine for several years.
- CMV occurs worldwide, with over 80% of adults having antibodies.
Diagnosis of CMV
- Histology reveals enlarged cytomegalic cells with a dense central "owl's eye," basophilic intranuclear inclusion body in tissue and urine.
- Serological tests like ELISA distinguish primary and recurrent infection by demonstrating IgG seroconversion.
- Rapid diagnosis involves viral antigen detection using immunoassays or rapid molecular diagnostic tests like PCR on tissue biopsy samples, blood, bronchoalveolar lavage, and urine.
- Culture is used in immunocompromised patients.
Treatment of CMV
- Treatment is only recommended in immunocompromised patients.
- Ganciclovir is moderately effective for retinitis and pneumonia.
- Valganciclovir, cidofovir, or fomivirsen (vitravene) treat CMV retinitis.
Immune Evasion Mechanisms:
- CMV destabilizes the assembly of MHC class I molecule and viral peptide complex, reducing presentation.
- CMV produces microRNAs that target the host cell's mRNA for class I MHC proteins, preventing their translation.
- CMV inhibits T cell activity and suppresses chemokine activity, preventing immune cell recruitment.
Impact on Immunocompromised Patients:
- Causes heterophil-negative mononucleosis with fever, lethargy, and abnormal lymphocytes.
- Can cause systemic infections like pneumonitis, esophagitis, and hepatitis.
- In AIDS patients, it leads to intractable colitis with diarrhea, retinitis, encephalitis, and blindness.
- Can result in failure of kidney transplants.
Additional Information
- CMV has the largest genome among human herpesviruses.
- Giant cells are formed, hence the name cytomegalovirus.
- Transmission occurs across the placenta, within the birth canal, or through breast milk.
- It can also be transmitted via saliva, sexually, through blood transfusions, or organ transplantation.
- In fetuses, CMV can cause cytomegalic inclusion disease, characterized by multinucleated giant cells with prominent intranuclear inclusions.
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