Crash course Flashcards by Neema Njeri

What is the fundamental difference between viruses and bacteria?

Viruses are obligate intracellular parasites that lack cellular structure and metabolism; bacteria are cellular organisms with independent metabolism.

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What are the essential components of a virus?

Nucleic acid (DNA or RNA) and a protein coat (capsid); some viruses also have an envelope.

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How do viruses differ in their genetic material?

Viruses can have either DNA or RNA, which can be single-stranded (ss) or double-stranded (ds), and may be linear or circular.

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What are the two main types of viral symmetry?

Icosahedral (spherical) and helical (rod-like).

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What is the difference between an enveloped and a non-enveloped virus?

Enveloped viruses have a lipid bilayer from the host membrane; non-enveloped viruses lack this, making them more resistant to environmental stress.

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What are the two major ways viruses are classified?

Baltimore Classification (based on nucleic acid type and replication strategy) and ICTV Classification (based on order, family, genus, species).

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What are the seven Baltimore Classification groups?

I: dsDNA (e.g., Herpesvirus)
II: ssDNA (e.g., Parvovirus)
III: dsRNA (e.g., Reovirus)
IV: (+) ssRNA (e.g., Picornavirus)
V: (-) ssRNA (e.g., Orthomyxovirus)
VI: ssRNA with reverse transcriptase (e.g., Retrovirus)
VII: dsDNA with reverse transcriptase (e.g., Hepadnavirus)

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What are the main steps of the viral replication cycle?

Attachment, Penetration, Uncoating, Replication, Assembly, Release.

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What are the two main mechanisms of viral entry?

Endocytosis (clathrin-mediated or caveolin-mediated) and membrane fusion.

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Which viruses use reverse transcriptase?

Retroviruses (HIV) and Hepadnaviruses (HBV).

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What are the major outcomes of viral infection in a host cell?

Lytic infection: Cell destruction
Persistent infection: Long-term viral presence
Latent infection: Dormant virus with possible reactivation
Oncogenic transformation: Virus-induced cancer (e.g., HPV, EBV)

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What are common viral cytopathic effects (CPEs)?

Cell rounding, syncytia formation (fusion), inclusion bodies, apoptosis.

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What is the primary innate immune defense against viruses?

Interferons (IFN-α, IFN-β), NK cells, macrophages.

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Which immune cells are crucial in controlling viral infections?

CD8+ T cells (cytotoxic T lymphocytes, CTLs).

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What are the two types of viral vaccines?

Live attenuated (e.g., MMR, polio [Sabin])
Inactivated/killed (e.g., HepA, polio [Salk])

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What is the genetic material of Influenza virus?

(-) ssRNA, segmented.

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What is antigenic shift vs. antigenic drift in Influenza?

Antigenic drift: Minor mutations → seasonal flu
Antigenic shift: Major reassortment → pandemics

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What is the receptor for HIV entry into cells?

CD4 (primary) and co-receptors CCR5/CXCR4.

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What is the cause of mononucleosis?

Epstein-Barr virus (EBV).

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What is the leading viral cause of congenital infections?

Cytomegalovirus (CMV).

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What type of genome does Hepatitis B virus (HBV) have?

Partially double-stranded DNA with reverse transcription.

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What is the most common cause of viral gastroenteritis?

Norovirus.

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What is the gold standard for diagnosing viral infections?

PCR (Polymerase Chain Reaction).

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Which test is commonly used for HIV diagnosis?

ELISA followed by Western Blot or PCR.

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What are inclusion bodies, and in which viruses are they seen?

Aggregates of viral proteins in infected cells: Negri bodies → Rabies virus Owl’s eye inclusions → CMV Cowdry bodies → HSV, VZV

What is antigenic drift?

Gradual accumulation of small mutations in viral genes, leading to partial immune evasion. Example: Seasonal influenza changes.

What is the mechanism of action of Maraviroc?

It is a receptor-binding inhibitor that blocks the CCR5 co-receptor, preventing HIV entry.

What is the function of Enfuvirtide in HIV treatment?

It binds to gp41 and prevents fusion of HIV with the host cell membrane.

Name a drug that inhibits HIV reverse transcription.

Zidovudine (NRTI), Efavirenz (NNRTI).

What is antigenic drift?

A gradual accumulation of small mutations in influenza genes, leading to new viral strains.

What is antigenic shift?

A major genetic reassortment in influenza A viruses, leading to new subtypes and potential pandemics.

Give an example of an inactivated vaccine.

Inactivated Polio Vaccine (IPV).

What is an advantage of inactivated vaccines?

They are safer as they cannot revert to cause disease.

What is a disadvantage of inactivated vaccines?

They require multiple doses to induce a strong immune response.

What is the transmission route of Hepatitis A?

Fecal-oral.

What is the transmission route of Hepatitis C?

Blood and body fluids.

Which of the two causes chronic infection?

Hepatitis C (in 70% of cases).

Name five viruses that cause viral gastroenteritis.

Rotavirus, Norovirus, Astrovirus, adenovirus 40/41, coronaviruses, calciviruses

How does an ELISA test work?

It detects viral antibodies or antigens using enzyme-linked reactions that produce a color change.

What is the purpose of Immunofluorescence Assay (IFA)?

It detects viral antigens by using fluorescently labeled antibodies.

What are prions?

Abnormal infectious proteins that cause neurodegenerative diseases.

Name a disease caused by prions.

Creutzfeldt-Jakob Disease (CJD).

How does HPV cause cervical cancer?

The E6 and E7 proteins inhibit tumor suppressor proteins (p53 and Rb), leading to uncontrolled cell division.

Name an HPV vaccine.

Gardasil.

Name three risk factors for acquiring HIV.

Unprotected sex, intravenous drug use, mother-to-child transmission.

What enzyme integrates HIV DNA into the host genome?

Integrase.

Name a drug that inhibits HIV integrase.

Raltegravir, Dolutegravir

How does rotavirus cause diarrhea?

It infects the small intestine, damages villous enterocytes, and disrupts electrolyte absorption.

Name three viruses that cause hemorrhagic fever.

Ebola, Lassa fever virus, Dengue virus.

What is the characteristic oral lesion seen in measles?

Koplik’s spots.

Name a serious complication of measles.

Encephalitis.

What are Negri bodies?

Eosinophilic inclusion bodies seen in neurons infected with rabies virus.

How is rabies transmitted?

Through bites or scratches from infected animals.

What is the significance of HBsAg in Hepatitis B?

It indicates an active infection.

What does the presence of anti-HBs antibodies mean?

Immunity due to past infection or vaccination.

Name a virus that causes viral encephalitis.

Herpes Simplex Virus (HSV).

How is poliovirus transmitted?

Fecal-oral route.

Name an antiviral used for herpes simplex infections.

Acyclovir.

How does acyclovir work?

It inhibits viral DNA polymerase, preventing DNA replication.

How does the immune system clear rotavirus?

Secretory IgA antibodies neutralize the virus.

Name a rotavirus vaccine.

Rotarix.

Name a mosquito-borne virus.

Dengue virus.

Name a tick-borne virus.

Crimean-Congo hemorrhagic fever virus.

Where does HIV remain latent?

In CD4+ T cells.

Why is HIV latency a challenge for treatment?

Latent reservoirs are not affected by antiretroviral therapy (ART).

Outline 5 complications of measles

Bronchopneumonia, otitis media, croup, diarrhea, blindness, encephalitis

List symptoms and complications of congenital rubella syndrome

- sensorineural hearing loss - ocular abnormalities- cataracts, glaucoma, retinopathy - cardiac abnormalities- PDA, PA stenosis - abortion/stillbirth -CNS: mental retardation, hypotonia, microcephaly, encephalitis - hepatosplenomegaly - anemia and thrombocytopenic purpura

Discuss how each stage of viral replication cycle of HIV can be a target for antiviral therapies

Attachment: Maraviroc (CCR5 antagonist) Entry(fusion): Enfuvirtide (fusion inhibitor) Reverse transcription: Zidovudine, Tenofovir (NRTIs); Efavirenz, Nevirapine (NNRTIs) Integration: Raltegravir, Dolutegravir (integrase inhibitors) Budding: Bevirimat( maturation inhibitor, experimental) Maturation: lopinavir, Darunavir ( protease inhibitors)

Complications of mumps

Encephalitis Deafness Orchitis Oophoritis Neuritis & myelitis GBS Myocarditis Arthritis

Viruses found in the gut and are not associated with gastroenteritis

1.Members of picornaviridae: * poliovirus * coxsackie * enteroviruses * hepatitis A&E 2. Adenoviruses 1-39 3. Reoviruses

Structure and proteins in rotavirus

* dsRNA with 11 segments VP4 protein- attachment VP7- attachment and entry NSP4- endotoxin that promotes ca2+ influx into enterocyte. It also prevents reabsorption of water and sodium

Signs that a child is suffering from rotavirus

Sunken fontanelle, sunken abdomen, few or no tears, dry mouth or tongue, decreased skin tugor, sunken eyes and cheeks * including diarrhea and vomiting