Virology 2 & 3 Flashcards
- Discuss the processes involve in transmission from one person to another .
vertical transmission: spread of the virus from an individual of one generation to its offspring in urtero (commonly by crossing the placenta, or contamination of the oviduct)
horizontal transmission: spread of the virus from one individual to another
- List the 6 basic ways that viruses are transmitted.
respiratory fecal-oral transmission by close contact transmission by insect vector transmission by animal vector direct injection
- Discuss viral entry into a host, including the most common entry sites.
majority infection transmitted by respiratory route
second most common site of entry is the gastrointestinal tract
the next most common is through mucous membranes such as genitalia or mouth
most common animal vector is via skin by mosquito, via insect defection and scratching of bite or through inhalation of dried excrement
- How do viruses potentially initiate an infection.
.
- Describe the processes involved in the spread of virus through the host in the two basic types of infections (local and dissemenated)?
localized infection at the organ or tissue of entry and the immune system is important in stopping the spread from cell to adjacent cell
disseminated infections spread through the blood exposing the entire system to the possibility of infection
- Using aseptic meningitis as an example, be able to describe the basic steps involved in a disseminated infection.
localized replication of site of entry is followed by spread to the lymphatic system
viruses must penetrate the basement membranes of mucosal membranes (pro-inflammatory cytokines? via matrix metaloprotinases)
virus is carried to lymph node by dendritic cells and has some capacity to replicate in lymph node cells and reach the blood
- Describe ways in which viruses directly damage cells and relate this to the causation of symptoms.
- host shut off
synthesis (sustained will kill the cell)
selective inhibition of host proteins - Inhibition of host cell protein
inhibition of host translation
change phosphorylation of DNA dependent RNA polymerase (Pol II)
interfere with splicing of host mRNA
interfere with transport of host mRNA to cytoplasm - Interfere with cell cycle
pushing cells to enter S phase and then hijacking replication “hardware” - triggering apoptosis AFTER replication
encode elements to block and also initiate apoptosis (HIV gp120 envelope protein triggers apoptosis of uninfected cells)
- Define cytopathic effect and be able to list examples.
cytopathic effect is shape/structural changes in host cell due to virus
shrinkage of cell nucleus
cell rounding and detachment from plate (disruption of tight junctions)
development of inclusion bodies (nuclear or cytoplasmic) including viral proteins
cell cell fusion (syncytium formation via enveloped virus) glycoproteins on cell membrane cause fusion
- Discuss the differences between acute and persistent infection.
acute: host is able to clear the infection, host may or may not show symptoms
persistent infection: host doesn’t clear infection; includes latent and chronic infections, these infections last at least 6mo after initial infection
(virus can exhibit both)
- Describe the differences between latent and chronic infection. What is the most significant difference between latent and chronic infection?
latent infections: during the latent periods, the virus is present but not infectious; reactivation can occur with virus shed asymptomatically and recrudescence when virus replication is associated with symptoms (Herpes)
chronic infection: infectious virus can be isolated form the host at any time following acquisition (Hep B)
- Define “incubation period” and explain what a virus is doing drug this time.
the incubation period is the time between infection and rise in positive blood antibodies, during this time it may appear that the viral load decreases as the virus breaks apart in replication
- Define “productive infection,” “abortive infection,” and “subclinical or asymptomatic infection.”
production infection: infection of a cell that results in the production and release of infectious virus , the cell is permissive for the virus
non-productive: infection of a cell that result in the failure to produce infectious virus, the cells are said to be non-permissive for viral replication
subclinical/asymptomatic infection: virus infects the host and triggers an immune response in the absence of specific (or any) symptoms
- Recognize the association between some viral infections and human malignancies.
viruses can cause changes in cell cycle from primary cells (limited passing) to immortalized cells that will continue to pass due to mutation in cellular growth regulation gene mutation or with additional mutations, transformed cells, which include loss of contact inhibition
these changes in cell cycle can lead to virus causing cancer through insertional mutagenesis (retroviruses) or chronic transforming retroviruses
- Be able to list which virus is associated with which malignancies.
HTLV- Adult T-cell Leukemia
HHV 8 (immunosuppressed)-Kaposi’s Sarcoma, lymphoma, Castleman’s
HPV- cervical, anogenital, skin, head and neck cancers
Epstein-Barr virus (immunosuppressed)- lymphomas, nasopharyngeal cancer, GI cancers
Hepatitis C and Hepatits B- hepatocellular carcinoma (**important risk factor)
Merkel Cell tumor polymer virus- Merkel cell carcinoma
Human cytomegalovirus- possibly gliomas and GI tumors
Discuss the salient features of respiratory spread of virus. Describe the mechanism and features that increase spread.
the most common mechanism
viruses increase coughing and sneezing, and also induce secretion of copious amounts of mucous and fluid contaminated with virus
*virus can survive for several hours or days on contaminated surfaces and objects
