Chapter 6 Viruses
Viral capsids can be (a)____________ (b)___________ (c)___________
(a) helical, (b) polyhedral (c) have a complex shape
RNA viruses can contain _________that can be directly read by the ribosomes to synthesize viral proteins. Viruses containing __________ must first use the it as a template for the synthesis of +ssRNA before viral proteins can be synthesized.
+ssRNA, −ssRNA
VIRAL DETECTION ____________________________ are distinct observable cell abnormalities due to viral infection. These can include loss of ___________ to the surface of the container, changes in cell ________ from flat to round, shrinkage of the nucleus, vacuoles in the cytoplasm, fusion of cytoplasmic membranes and the formation of multi nucleated syncytia, inclusion bodies in the nucleus or cytoplasm, and complete cell lysis.
Cytopathic effects (CPEs), adherence, shape
_________________ -portion of the phospholipid membrane of host surrounds the virus. Uses spikes made of glycoproteins embedded in its envelope to bind to host cells.
Enveloped viruses
Herpesvirus (300,000x) _________,__________. HSV-1 and HSV-2genital herpes -_____________ virus (the cause of chicken pox and shingles). -_____________virus (implicated in mononucleosis and some cancers). Extremely widespread among humans. More than 90% of adults have been infected with at least one of these, and a latent form of the virus remains in almost all humans who have been infected.
Enveloped, dsDNA virus Varicella zoster Epstein-Barr
Similar to rapid, over-the-counter pregnancy tests, ________________ for viral antigens require a few drops of _______ or _________ applied to a membrane filter. The membrane filter has been previously modified and embedded with ___________ to viral antigen and internal controls. _______________ is added to the filter, with the targeted antibody attached to the antigen (in the case of a positive test). Excess conjugate is washed off the filter. ___________ is added to activate the enzyme-mediated reaction to reveal the color change of a positive test.
Enzyme immunoassays (EIS), diluted patient serum or plasma, antibody, Antibody conjugate, Substrate
RNA Viruses Examples:
Flaviviruses: yellow fever, West Nile, Dengue, Zika, Coronavirus, Rhinovirus - common cold, Polio, Norovirus "winter vomiting bug".
_________________ and _______________ are the two large glycoproteins on the outside of the viral particles. •_____________ mediates binding of the virus to target cells and entry of the viral genome into the target cell. •_______________ is involved in the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral particles. •They are antigens to which antibodies can be raised. Influenza A viruses are classified into subtypes based on antibody responses to HA and NA.
Hemagglutinin (HA) and neuraminidase (NA) HA NA
At the tips of these spikes are structures that allow the virus to attach and enter a cell, hemagglutinin spikes (H) or enzymes like the neuraminidase (N) influenza virus spikes that allow the virus to detach from the cell surface during release of new versions. _______________ are often identified by their H and N spikes. For example: _______________
Influenza viruses, H1N1 influenza
____________- capsomere subunits form capsid surrounding nucleic acid. Uses spikes made of glycoproteins from its capsid to bind to host cells.
Naked viruses
VIRUSES AND CANCER ____________ viruses: Experts estimate that up to 13% of human cancers are caused by viruses. ______________ virus: Carries genes that directly cause cancer, Virus produces proteins that induce a loss of growth regulation in the cell.
Oncogenic, Transformation
______________- A MISFOLDED ROGUE FORM OF A NORMAL PROTEIN (PRPC) FOUND IN THE CELL.
PRION
BACTERIOPHAGE CLASSIFICATIONS ____________ phages typically lead to the death of the cell through cell lysis. _____________ phages, on the other hand, can become part of a host chromosome and are replicated with the cell genome until such time as they are induced to make newly assembled viruses, or ___________ viruses. .
Virulent, Temperate, progeny
Characteristics of Viruses: 1. infectious, _____________ pathogens 2. Obligate intracellular parasite with ________ and cell-type specificity. 3. _______ or ________ genomes (never both). 4. Genome is surrounded by a ____________ capsid and, in some cases, a _____________ membrane studded with viral _____________. 4. Lack ___________ for many products needed for successful reproduction, requiring exploitation of host-cell genomes to reproduce.
acellular, host, DNA or RNA, protein, phospholipid, glycoproteins, genes
HEMAGGLUTINATION TEST FOR VIRUSES Row A: Erythrocytes do not bind together and will sink to the bottom of the well plate; this becomes visible as a red dot in the center of the well. Row B: Many viruses have hemagglutinins that causes ______________(virus present) of erythrocytes; the resulting hemagglutination forms a lattice structure that results in red color throughout the well. Row C: Virus-specific antibody, the viruses, and the erythrocytes are added to the well plate. The virus specific antibodies __________ agglutination effect, as can be seen as a red dot in the bottom of the well.
agglutination, inhibit
In this transmission electron micrograph, a____________- a virus that infects bacteria, is dwarfed by the bacterial cell it infects.
bacteriophage
Papillomavirus (HPV) (warts) Limited to the __________ cells of stratified epithelium, the only tissue in which they replicate Responsible for: warts, genital warts, several kinds of cancer (form pre-cancerous lesions (Often transmitted sexually)
basal cells
A ________________ is a disease with symptoms that are recurrent or persistent over a long time. Some viral infections can be _________ if the body is unable to eliminate the virus. HIV is a virus that is an example of this. Once a person becomes infected with HIV, the virus can be detected in tissues continuously thereafter, but untreated patients often experience no symptoms for years. However, the virus maintains persistence through several mechanisms that interfere with immune function, altering immune cells and eventually, a progression of the disease leading to acquired immunodeficiency syndrome (AIDS).
chronic infection, chronic
ANIMAL VIRUSES- INFLUENZA VIRUS After binding to host receptors, animal viruses enter through _____________- engulfment by the host cell or through membrane __________. Many viruses are _____________, meaning they only infect a certain type of host; and most viruses only infect certain types of cells within tissues. This specificity is called a ______________. Influenza virus replicates in the ____________.
endocytosis, fusion, host specific, tissue tropism, nucleus
Influenza -_______________, ___________ virus -Commonly known as "the flu" -symptoms go from mild to severe (death) -Three of the four types of influenza viruses affect humans: Type A, Type B, and Type C. -Type D has not been known to infect humans, but is believed to have the potential to do so. -Yearly vaccinations against influenza are recommended -Influenza spreads around the world in yearly outbreaks, resulting in about three to five million cases of severe illness and about 290,000 to 650,000 deaths. -In the 20th century, three influenza pandemics occurred (all Influenza type A): _____________ influenza in 1918 (17-100 million deaths), __________ influenza in 1957 (two million deaths), Hong Kong influenza in 1968 (one million deaths). The World Health Organization declared an outbreak of a new type of influenza A/H1N1 to be a pandemic in June 2009 (Swine flu).
enveloped, RNA Spanish Asian Hong Kong
HIV, an __________, ___________ retrovirus, attaches to a cell surface receptor of an immune cell and fuses with the cell membrane. Viral contents are released into the cell, where viral enzymes convert the single-stranded RNA genome into _______ and incorporate it into the host genome. +ssRNA-->dsDNA-->integration
enveloped, icosahedral, DNA
EMBRYO OR HOST ANIMAL CAN SERVE AS AN INCUBATOR FOR VIRAL REPLICATION The cells within chicken eggs are used to culture different types of viruses. Cultivation is important for: 1) _______________,_______________ of pathogenic viruses in clinical specimens. 2) production of __________ (ex. influenza) 3)basic _________________. Many viruses have a tissue ____________, and must therefore be introduced into a specific site for growth. Viruses can be replicated in various locations within the egg, including the ____________ membrane, the ________________, and the _____________.
identification, diagnosis, vaccines, research studies, tropism, chorioallantoic, amniotic cavity, yolk sac
Some viruses are capable of remaining hidden or dormant inside the cell in a process called __________. For example the chickenpox virus can reactivate in the form of shingles, usually manifesting as a painful, localized rash on one side of the body, emerging from the ganglia in which the virus was dormant.
latency
TEMPERATE- LYSOGENIC CYCLE A temperate bacteriophage has both lytic and lysogenic cycles. In the ____________ cycle, phage DNA is incorporated into the host genome, forming a prophage, which is passed on to subsequent generations of cells. Environmental stressors such as starvation or exposure to toxic chemicals may cause the prophage to be excised and enter the lytic cycle.
lysogenic
VIRUSES CULTIVATED IN VITRO Cells for culture are prepared by separating them from their tissue _____________. (a) Primary cell cultures grow attached to the surface of the culture container. __________________ slows the growth of the cells once they become too dense and begin touching each other. At this point, growth can only be sustained by making a ________________. (b)_______________ cell cultures are not affected by contact inhibition. They continue to grow regardless of cell density.
matrix, Contact inhibition, secondary culture, Continuous
CULTIVATION OF VIRUSES Lytic viruses form __________, on plates containing a "lawn" of cells - clear spots where cells have been lysed.
plaques
In humans, the viruses cause ____________________, including the common cold, which are typically mild, though rarer forms such as SARS (Severe acute respiratory syndrome), MERS (Middle East respiratory syndrome) and COVID-19 (Coronavirus disease 2019) can be lethal. They are enveloped viruses with a positive-sense single-stranded RNA genome.
respiratory infections
The size of a virus is __________ relative to the size of most bacterial and eukaryotic cells and their organelles.
small
PRION AFFECTS ON THE BRAIN ________________________________ in human and animals. Is a rare degenerative disorder that affects the brain and nervous system. The accumulation of rogue proteins causes the brain tissue to become spongelike, killing brain cells and forming holes in the tissue, leading to brain damage, loss of motor coordination, and dementia. Includes: kuru, fatal familial insomnia, Gerstmann-Straussler-Scheinker disease, and Creutzfeldt-Jakob disease. There is no cure, and the disease progresses rapidly, eventually leading to death within a few months or years.
transmissible spongiform encephalopathy
