Poxviruses and Smallpox Quiz
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Questions and Answers

What type of genome do poxviruses possess?

  • Double stranded DNA (correct)
  • Single stranded DNA
  • Single stranded RNA
  • Double stranded RNA

    • Which characteristic of poxviruses allows them to be viewed under light microscopy?

  • Their unusual shape
  • Their small size
  • Their large size (correct)
  • Their unique color

    • What mechanism do poxviruses employ to counteract the antiviral response of infected cells?

  • Blocking cell division
  • Inhibiting the production of interferons
  • Enhancing the immune response
  • Producing a decoy receptor for interferons (correct)

    • How was smallpox transmitted among individuals?

    <p>By respiratory droplets and close contact</p> Signup and view all the answers

    What evidence suggests that smallpox has been known to humans for thousands of years?

    <p>Ancient remains and phylogenetics</p> Signup and view all the answers

    What was the first outpatient AIDS clinic in the United States?

    <p>Ward 86</p> Signup and view all the answers

    Which event marked the first public acknowledgment of AIDS by a U.S. President?

    <p>Ronald Reagan's mention in 1985</p> Signup and view all the answers

    What is the primary function of the gp120 protein in HIV?

    <p>Attaches to the CD4 receptor on T cells</p> Signup and view all the answers

    What characterizes the chronic phase of HIV infection?

    <p>Low-level viremia is controlled</p> Signup and view all the answers

    What is the mutation rate of HIV during replication compared to human DNA?

    <p>1 in 10,000 base pairs</p> Signup and view all the answers

    What leads to the opportunistic infections in AIDS patients?

    <p>Decline of CD4 T cells</p> Signup and view all the answers

    What is the principal reason HIV is not easily cleared from the body?

    <p>Latency of integrated proviruses</p> Signup and view all the answers

    TB is considered a leading cause of death among which population?

    <p>People living with HIV</p> Signup and view all the answers

    What function does HIV protease serve in the viral life cycle?

    <p>Cleaves precursor proteins for new virus assembly</p> Signup and view all the answers

    What is the primary focus of antiretroviral therapy (ART) in HIV treatment?

    <p>To block viral replication at multiple steps</p> Signup and view all the answers

    What does HAART stand for in HIV treatment?

    <p>Highly-active antiretroviral therapy</p> Signup and view all the answers

    Which of the following statements about PrEP is correct?

    <p>PrEP can reduce the chances of getting HIV from sex by up to 99%</p> Signup and view all the answers

    What is a significant challenge in the treatment of HIV regarding latent viruses?

    <p>They can reactivate when ART is discontinued</p> Signup and view all the answers

    What is one of the goals set for 2040 regarding HIV/AIDS?

    <p>To achieve the '95-95-95' targets</p> Signup and view all the answers

    What does U=U represent in the context of HIV treatment?

    <p>Undetectable equals untransmissible</p> Signup and view all the answers

    Which antiretroviral drug was the first approved for HIV treatment?

    <p>AZT</p> Signup and view all the answers

    What is one of the key reasons why a vaccine for HIV has been difficult to develop?

    <p>HIV is highly mutable and can rapidly change</p> Signup and view all the answers

    What is the primary risk associated with Dengue virus secondary infections?

    <p>Increased symptom severity due to antibody-dependent enhancement</p> Signup and view all the answers

    Which characteristic is true about the dengue disease symptoms?

    <p>A significant percentage of infections are asymptomatic</p> Signup and view all the answers

    What role do Fc gamma receptors play in dengue virus infections?

    <p>They help in binding and facilitating dengue virus entry into cells</p> Signup and view all the answers

    Which statement is accurate regarding the current understanding of the dengue vaccine?

    <p>It poses risks only to previously uninfected individuals</p> Signup and view all the answers

    What similarities exist between dengue and Zika viruses?

    <p>Zika antibodies can cross-react with DENV, increasing severe risk</p> Signup and view all the answers

    Which of the following describes a key characteristic of RSV?

    <p>Re-infections are common due to the variability of the virus</p> Signup and view all the answers

    What is the common transmission route for RSV?

    <p>Direct respiratory contact</p> Signup and view all the answers

    What is the role of Wolbachia in combating DENV infections?

    <p>It decreases DENV transmission in mosquitoes</p> Signup and view all the answers

    How does the live attenuated DENV vaccine work?

    <p>It provides a primary infection response even in uninfected individuals</p> Signup and view all the answers

    What is the significance of molecular clock analysis in the context of DENV?

    <p>It helps trace back DENV transmission to humans</p> Signup and view all the answers

    What is the significance of reassortment in influenza viruses?

    <p>It leads to large changes in immunogenicity and virus evolution.</p> Signup and view all the answers

    Which pandemic was characterized by a significant impact on younger age groups, particularly in 2009?

    <p>H1N1 Swine flu pandemic</p> Signup and view all the answers

    Why is the H5N1 avian influenza virus considered highly pathogenic in domestic poultry?

    <p>It causes dramatic and unpredictable spread among birds.</p> Signup and view all the answers

    What leads to the vertical transmission of endogenous retroviruses?

    <p>Infection of germ line cells.</p> Signup and view all the answers

    What percentage of individuals over 50 years old had antibodies neutralizing the 2009 H1N1 strain?

    <p>33%</p> Signup and view all the answers

    What major change in immunogenicity can occur due to reassortment?

    <p>Altered ability to trigger immune responses.</p> Signup and view all the answers

    What is a potential consequence of the HPAI spread beyond birds?

    <p>It raises concerns about reassortment or mutations impacting human health.</p> Signup and view all the answers

    What does the term 'endogenization of a virus' refer to?

    <p>Infection leading to permanent integration into host DNA.</p> Signup and view all the answers

    What aspect of the 1918 H1N1 outbreak is significant regarding its immunogenicity?

    <p>No significant immunogenic changes occurred.</p> Signup and view all the answers

    What has been identified as a significant barrier to zoonosis in viral infections?

    <p>Most animal viruses cannot replicate in humans.</p> Signup and view all the answers

    What was unique about the 1918 influenza virus compared to previous strains circulating in humans?

    <p>It was closely related to avian virus sequences.</p> Signup and view all the answers

    Which of the following best describes antigenic drift?

    <p>Point mutations in existing human influenza variants.</p> Signup and view all the answers

    What is a significant challenge in developing effective influenza vaccines?

    <p>Predicting the circulating strains can be complex.</p> Signup and view all the answers

    Which population group has historically experienced the highest mortality rate from influenza?

    <p>Very young children and older adults.</p> Signup and view all the answers

    What is the primary mechanism behind antigenic shift in influenza viruses?

    <p>Reassortment of RNA segments from different strains.</p> Signup and view all the answers

    Why did the 1918 influenza pandemic lead to a massive increase in mortality among healthy adults?

    <p>Cross reactive immune responses may have contributed to unusual severity.</p> Signup and view all the answers

    What is the function of the HA protein in influenza viruses?

    <p>It mediates receptor binding and is a target for antibodies.</p> Signup and view all the answers

    Which of the following statements is true regarding avian influenza infections in humans?

    <p>They can lead to severe outcomes with high viral loads.</p> Signup and view all the answers

    Which of the following best describes the spread of the 1918 influenza pandemic?

    <p>It spread rapidly through US military troops.</p> Signup and view all the answers

    What was a notable impact of the 1918 influenza pandemic on indigenous populations in Alaska?

    <p>Major loss of adult population and life expectancy.</p> Signup and view all the answers

    What is one reason the poliovirus vaccine has been successful in eradicating polio?

    <p>There is no animal reservoir</p> Signup and view all the answers

    Which characteristic best describes the measles virus?

    <p>Single-stranded negative sense RNA genome</p> Signup and view all the answers

    Which protein on the measles virus is crucial for binding to host cell receptors?

    <p>Hemagglutinin protein</p> Signup and view all the answers

    What phenomenon occurs due to the depletion of memory lymphocytes during a measles infection?

    <p>Immune suppression</p> Signup and view all the answers

    How does measles virus contribute to 'immune amnesia'?

    <p>By eliminating the antibody repertoire globally</p> Signup and view all the answers

    What is the estimated basic reproduction number (R0) for measles virus?

    <p>15</p> Signup and view all the answers

    What is a significant historical outcome associated with the measles epidemic in the Faroe Islands?

    <p>Long-lasting immunity developed for over 65 years</p> Signup and view all the answers

    What response was initiated in California following the Disneyland measles outbreak?

    <p>Education on vaccine application for kindergartners</p> Signup and view all the answers

    What is the main vector responsible for the transmission of dengue virus?

    <p>Mosquitoes</p> Signup and view all the answers

    What type of vaccine is the measles vaccination?

    <p>Live attenuated vaccine</p> Signup and view all the answers

    What is a common complication associated with measles infection?

    <p>Subacute sclerosing panencephalitis (SSPE)</p> Signup and view all the answers

    Which disease is caused by a flavivirus and can lead to hemorrhagic fever?

    <p>Dengue</p> Signup and view all the answers

    What crucial factor allows dengue virus to replicate in both humans and mosquitoes?

    <p>Ability to use host proteases</p> Signup and view all the answers

    What is a significant barrier to achieving herd immunity for measles?

    <p>High vaccine coverage threshold of over 90%</p> Signup and view all the answers

    What was the purpose of variolation?

    <p>To provide immunity against smallpox</p> Signup and view all the answers

    Who is credited with developing the first vaccine and what was its source?

    <p>Edward Jenner - Cowpox</p> Signup and view all the answers

    What differentiates inactivated poliovirus (IPV) from attenuated oral poliovirus (OPV)?

    <p>OPV protects against intestinal infection, while IPV does not.</p> Signup and view all the answers

    What percentage of the global population is still not immune to smallpox?

    <p>70%</p> Signup and view all the answers

    What is a significant risk associated with the use of the oral poliovirus vaccine (OPV)?

    <p>Development of vaccine-derived poliovirus</p> Signup and view all the answers

    Why was the development of HeLa cell lines important for poliovirus research?

    <p>They enabled growth of the virus outside a human host.</p> Signup and view all the answers

    What is a key characteristic of picornaviruses?

    <p>Their RNA serves both as the genome and mRNA.</p> Signup and view all the answers

    Which viral disease was eradicated globally by 1980?

    <p>Smallpox</p> Signup and view all the answers

    What type of disease can monkeypox exhibit in humans?

    <p>Genital ulcers</p> Signup and view all the answers

    What is one of the most critical factors contributing to poliovirus's success as a pathogen?

    <p>Highly contagious and stable in the environment</p> Signup and view all the answers

    What factor aids in the transmission of MPOX in certain populations?

    <p>Increased mobility and international travel</p> Signup and view all the answers

    What significant development did Jonas Salk contribute to vaccine history?

    <p>Developed the inactivated polio vaccine</p> Signup and view all the answers

    Which characteristic of the cowpox vaccine made it effective against smallpox?

    <p>It was derived from a closely related virus.</p> Signup and view all the answers

    What is the most significant factor for RSV vaccine development?

    <p>Evasion of innate immunity</p> Signup and view all the answers

    Which population is most susceptible to severe RSV illness?

    <p>Babies less than one year old</p> Signup and view all the answers

    How does the RSV F glycoprotein behave during the fusion process?

    <p>Changes shape dramatically</p> Signup and view all the answers

    What role does neuraminidase (NA) play in influenza virus infection?

    <p>It aids in the release of virions from infected cells</p> Signup and view all the answers

    What type of influenza virus primarily causes seasonal epidemics and pandemics?

    <p>Type A</p> Signup and view all the answers

    How does vaccination of pregnant women impact infants regarding RSV?

    <p>It offers protection against RSV</p> Signup and view all the answers

    What seasonal pattern is observed with RSV infections?

    <p>Strong seasonality with peaks in winter</p> Signup and view all the answers

    What is a potential risk associated with the original RSV vaccine?

    <p>Enhancement of severe disease upon infection</p> Signup and view all the answers

    Influenza's segmented genome allows for what critical evolutionary event?

    <p>Reassortment of genes from different viruses</p> Signup and view all the answers

    What triggers a cytokine storm during severe influenza infections?

    <p>Overproduction of cytokines by immune cells</p> Signup and view all the answers

    Which of the following is true regarding the influenza life cycle?

    <p>Genome segments are packaged and released from the cell</p> Signup and view all the answers

    Which statement accurately describes the seasonal pattern of influenza infection?

    <p>Infection peaks in late fall/winter in both hemispheres</p> Signup and view all the answers

    What is the primary host range for influenza viruses?

    <p>Aquatic birds, humans, and farm animals</p> Signup and view all the answers

    In RSV vaccine development, which protein is favored for immunization?

    <p>Prefusion F protein</p> Signup and view all the answers

    What is the primary characteristic of the HIV virus?

    <p>It is a retrovirus that uses reverse transcriptase.</p> Signup and view all the answers

    How is the Koala Retrovirus (KoRV) primarily transmitted?

    <p>Both horizontally and vertically.</p> Signup and view all the answers

    Which cell type is primarily targeted by HIV?

    <p>CD4+ T cells</p> Signup and view all the answers

    What is the significance of syncytin in mammalian biology?

    <p>It facilitates nutrient exchange between mother and fetus.</p> Signup and view all the answers

    What role does the co-receptor play in HIV infection?

    <p>It allows gp120 to attach to the CD4 receptor.</p> Signup and view all the answers

    What did Howard Temin and David Baltimore discover that earned them the Nobel Prize?

    <p>The existence of reverse transcriptase.</p> Signup and view all the answers

    Which group of HIV is responsible for the majority of cases globally?

    <p>HIV Group M</p> Signup and view all the answers

    What is the mode of transmission for HIV?

    <p>Through sexual contact, blood, and breastfeeding.</p> Signup and view all the answers

    What complicates the entry of HIV into host cells?

    <p>The requirement for two distinct receptors.</p> Signup and view all the answers

    Which of the following statements about endogenous viral elements (EVEs) is true?

    <p>EVEs are viral sequences integrated into a host genome.</p> Signup and view all the answers

    Which of the following is a consequence of CD4+ T cell depletion due to HIV?

    <p>Severe immunosuppression.</p> Signup and view all the answers

    Endogenization in KoRV allows for which of the following processes?

    <p>Vertical transmission to offspring.</p> Signup and view all the answers

    Which of the following accessory proteins is associated with the HIV viral life cycle?

    <p>Reverse transcriptase, protease, and integrase.</p> Signup and view all the answers

    Which viral characteristic is linked to the slow progression of HIV-related disease?

    <p>Lentivirus classification.</p> Signup and view all the answers

    What transmission event likely led to HIV's transfer from chimpanzees to humans?

    <p>Consumption of bushmeat during butchering.</p> Signup and view all the answers

    Study Notes

    Poxviruses

    • Family: Poxviridae
    • Double-stranded DNA genome
    • First vaccine developed; only human virus completely eradicated
    • Very large; 170-250 kb linear dsDNA genome
    • Replicates in the cytoplasm
    • Visible with light microscopy
    • Tightly packed genome; no introns/overlapping genes
    • Immunomodulation experts; block interferon signaling
    • Smallpox transmission: respiratory droplets, fomites/contact
    • Smallpox lethality: 30%
    • Origin: >3000 years ago in India, China, Africa; endemic in Asia by 1000 CE, Europe by 1800s
    • Phylogenetic analysis of ancient remains used to sequence and date smallpox

    Poxvirus Vaccines

    • Variolation: early form of vaccination (16th century China) – dried smallpox material applied to skin/inhaled
    • Cowpox protection against smallpox (1790s Jenner): milkmaids exposed to cowpox were immune to smallpox
    • Current smallpox vaccine: live attenuated; unknown origin/attenuation history

    Other Poxviruses

    • Poxviruses infect many mammals (cowpox from cows, monkeypox from small mammals)
    • Cross-species transmission can occur but human-to-human spread after transmission may be limited
    • Smallpox globally eradicated by 1980
    • Monkeypox (MPOX) is endemic in parts of Africa; recent spread in gay community (2022)

    Picornaviruses (Polio)

    • Family: Picornaviridae, genus: Enterovirus
    • Single-stranded positive-sense RNA genome (8 kb)
    • Fecal-oral transmission
    • No envelope
    • Protein shells
    • Three serotypes (variants)
    • Diseases: paralysis, meningitis, “summer cold”
    • Replication: Cleaves large polyprotein; associated with lipid membranes
    • Poliovirus Replication Stages: Ingested -> oropharyngeal & intestinal mucosa -> reaches blood via lymph nodes ->enters CNS via retrograde axonal transport

    Poliovirus Epidemiology and Vaccine Development

    • Most infections are mild/asymptomatic; US: 0.5-1.0% paralysis, 30% permanent, 5-10% death (respiratory failure)
    • Poliovirus: 1950s; iron lungs to aid breathing
    • Polio Vaccine Development:
      • Inactivated Poliovirus Vaccine (IPV) (Salk, 1955): killed virus (no replication); injected; induces serum antibodies but does not prevent intestinal infection
      • Oral Poliovirus Vaccine (OPV) (Sabin, 1959): live attenuated, oral, induces mucosal immunity; potential for reversion of virulence to Vaccine-Associated Paralytic Poliomyelitis (VAPP), so this is no longer used

    Measles

    • Family: Paramyxoviridae, genus: Morbillivirus
    • Single-stranded negative-sense RNA genome (15-16 kb)
    • Respiratory transmission
    • Diseases: measles, subacute sclerosing panencephalitis (SSPE), immunosuppression
    • R0 (Basic Reproduction Number) for measles: 15+ (highly contagious)

    Measles Characteristics

    • Genome encodes 6 proteins; hemagglutinin (binds host cells), nucleoprotein (protects genome)
    • Spreads into and out of body; infects macrophages/dendritic cells -> lymph nodes -> additional lymph tissues & organs -> airway epithelium -> released by coughing/sneezing.
    • Causes immunosuppression (immune amnesia); eradicates memory B and T cells, eliminating antibody repertoire.
    • SSPE: Rare, chronic brain infection.
    • Herd immunity: crucial for measles control, achieved through infection or vaccination. Measles virus has a high herd immunity threshold.

    Measles and Vaccination

    • Live-attenuated vaccine (chicken cells), very effective, long-lasting immunity.
    • Effectiveness of vaccine: 1781 measles outbreak in the Faroe islands (no infection for 65 years) and herd immunity.
    • Disneyland 2014 outbreak spurred vaccination campaigns.
    • COVID-19 pandemic hindered measles campaigns.

    Zika and Dengue Viruses

    • Family: Flaviridae, genus: Flavivirus
    • Single-stranded positive-sense RNA genome
    • Vector-borne transmission (mosquitoes)
    • Diseases: hemorrhagic fever, encephalitis
    • Dengue: 4 serotypes; antibody-dependent enhancement (ADE) increases severe disease risk in subsequent infection
    • ADE: Antibodies enhance virus entry into cells.
    • Zika: typically mild symptoms but severe outcomes in pregnant women
    • Dengue transmission: human and primate cycles (zoonotic spillover)

    RSV

    • Family: Pneumoviridae, genus: Orthopneumovirus
    • Single-stranded negative-sense RNA genome
    • Respiratory transmission
    • Primarily upper respiratory tract infection in adults; lower respiratory tract in young children (pneumonia, respiratory failure)
    • RSV: strongly seasonal.
    • Immunopathogenesis: major challenge for vaccine development.
    • New RSV vaccine candidate (Moderna) in trials; effective at preventing lower respiratory disease; vaccination of pregnant women protects babies.

    Influenza

    • Family: Orthomyxoviridae
    • Single-stranded negative-sense RNA genome
    • Segmented genome Various hosts (avian, human, pig, etc.)
    • Respiratory transmission
    • Seasonal and pandemic patterns—Influenza A, B, C
    • Seasonal epidemics; pandemics are caused by reassortment: causing large changes in immunogenicity
    • Antigenic drift: point mutations
    • Antigenic shift: reassortment

    Ancient viruses (Retroviruses, HERVs)

    • Retroviruses convert RNA into DNA, inserting into host genome
    • Human endogenous retroviruses (HERVs): “fossil viruses”
    • Vertical transmission; present in germline
    • Co-option of viral sequences by host – Syncytin (fetal placenta)
    • Koala Retrovirus (KoRV): currently infecting koalas
    • Endogenous Prosimian Immunodeficiency Viruses (EIDVs)
    • Lentiviruses (HIV)

    HIV and AIDS

    • Family: Retroviridae, genus: Lentivirus
    • Single-stranded positive-sense RNA, reverse-transcribing
    • Transmission: sexual contact, blood, breastfeeding
    • HIV lifecycle: entry, reverse transcription, integration, assembly, release
    • HIV targets CD4+ T cells (helper T cells)
    • Acute phase: flu-like symptoms, high viremia
    • Chronic phase: gradual loss of CD4+ T cells, potentially leads to AIDS – opportunistic infections
    • Antiretroviral therapy (ART): treatment to block viral replication
    • Prevention methods: PrEP (Pre-Exposure Prophylaxis)

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    Test your knowledge on poxviruses and their unique characteristics. This quiz covers the genomic structure, transmission mechanisms, and historical significance of smallpox. Explore how these viruses interact with host immune responses and their visibility under microscopy.

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