LAM3_66-80 Flashcards
What type of virus is LCMV?
Arenavirus, single-stranded enveloped RNA virus.
LCMV strains are closely related antigenically, but can vary in 4 properties. List these properties.
- Rate of replication
- Tissue tropism
- Pathogenicity
- Immunogenicity
What strains of the LCMV have been used extensively to develop and study mouse models of virus-induced immune injury?
Neurotropic and viscerotropic strains.
True or False. LCMV can infest both insect and mammalian cells.
True
True or False. Natural infection of LCMV in immunocompromised adult mice is usually self-limiting and asymptomatic.
False. Natural infection in immunocompetent adult mice is usually self-limiting and asymptomatic.
What are the four basic patterns of LCMV clinical disease that are recognized from the study of experimentally induced infection?
- Cerebral form - 5-6 days after intracranial inoculation in immunocompetent mice
- Visceral form - adult mice after inoculation with viscerotropic strains
- Runting and death - in neonatally infected suckling mice
- Late-onset disease - in previously asymptomatic carrier mice that develop immune complex glomerulonephritis. Usually the result of prenatal or neonatal infection and occurs in PI mice around 9-12 months of age.
Which laboratory animals can be infected with LCMV? Which of these species are known transmitters of the disease?
Mice, hamsters, guinea pigs, and NHP can be infected.
Hamsters can transmit virus to other hamsters and mice, and are the primary source of human LCMV.
What are the BSL requirements for LCMV?
BSL-2 practices, containment equipment, and facilities are suitable for:
- activities utilizing known or potentially infectious body fluids
- cell culture passaged of laboratory-adapted strains
- adult mice with mouse-brain-passaged strains
BSL-3 is required for:
- all work with infected hamsters
- high potential for aerosol production
- production quantities or high concentrations of infectious materials
- manipulation of infected transplantable tumors, field isolates, and clinical material from human cases
- any strain shown to be lethal in NHPs
BMBL, p 216
How does LCMV usually enter an animal facility?
Infected biologicals or by feral mice, which are natural reservoirs.
How do LCMV carrier mice develop?
Carrier mice develop as a result of asymptomatic prenatal or neonatal infection.
True or False. Infection of LCVM in adult mice is acute because of the onset of effective immunity. Spread of the disease is halted.
True.
Describe LCVM shedding in the adult hamster.
The adult hamster can remain viremic and viruic for many months.
What is the primary source of human LCVM infection?
Hamsters
What is LCMV the prototype for?
Virus-induced T lymphocyte-mediated immune injury and immune complex disease.
How is LCMV diagnosed?
Serologically by IFA or ELISA tests.
Why are false negative results for LCMV seen?
Carrier mice may develop poor humoral immune responses that can lead to false negative results.
Differential diagnosis for LCMV.
Neurological clinical signs rule/out: MHV, MEV, meningoencephalitis from metastatic bacterial infection, trauma, neoplasia, and toxicity.
Early-onset disease rule/out: Other causes of early mortality including MHV, ectromelia virus, Reovirus 3 infection Tyzzer’s disease or husbandry-related insults.
List ways to prevent and control LCMV in a mouse colony.
Selective testing and culling can be done because the mouse to mouse spread is slow. For mice that are replaceable, depopulation is a more reliable option. Valuable stock can be rederived, but check progeny to rule out in utero transmission.
How is LCMV controlled in hamsters?
Infected hamsters excrete a large amount of the virus in urine and saliva. Exposed hamsters should be destroyed.
List other ways humans can contract LCMV.
Humans can contract LCMV by exposure to contaminated cell cultures, transplantable tumors and vaccines.
Give the ways in which LCMV can complicate research.
- stimulate or suppress immunological responses in vivo or in vitro and replicate in cells used in immunological studies
- immune complex disease can complicate long-term experiments and morphological interpretations
- illness and death in infected animals.
What type of virus is Sendai virus (SV)?
- family Paramyxoviridae
- subfamily Paramyxovirinae
- genus Respirovirus.
- antigenically related to human parainfluenza virus 1
True or False. Sendai virus is a single stranded DNA virus whose lipid solvent-resistant envelope contains glycoproteins with hemagglutinating, neuramidase and cell fusion properties.
False. Sendai virus is a single stranded RNA virus whose lipid solvent-sensitive envelope contains glycoproteins with hemagglutinating, neuramidase, and cell fusion properties.
What mammalian cell lines does SV grow best in?
Monkey kidney, Baby hamster kidney (BHK-21), and mouse fibroblast (L).
What are the clinical signs of SV in mice?
- In adult mice, hunched position, erect hair coat, rapid weight loss, dyspnea, chattering sounds and crusting around the eyes. Highly susceptible adults may die.
- The infection is lethal in suckling mice.
- Athymic mice and immunosuppressed mice are at high risk and may develop wasting syndrome.
What strain is resistant to clinically apparent SV? Which is highly susceptible?
C57BL/6 resistant
DBA/2 are highly susceptible
Does prenatal infection occur with SV?
No
Enzootic infection of SV is commonly detected in postweaned (_ to _ weeks old) and is associated with seroconversion within _-_days and the termination of infection.
Enzootic infection is commonly detected in postweaned (5 to 7 weeks old) and is associated with seroconversion within 7-14 days and the termination of infection.
What other species are susceptible to SV infection?
Rats, hamsters, and guinea pigs
True or False. Viral replication of SV during natural infection is restricted to the respiratory tract tract.
True
Explain the gross lesions seen in the lungs of mice infected with Sendai virus.
Partial to complete consolidation of the lungs. Individual lung lobes are meaty and plum-colored. The cut surface may exude a frothy serosanguinous fluid. Pleural effusions or abscesses caused by secondary bacterial infections are sometimes seen. Fluid may accumulate in the pleural and pericardial cavities.
What cell types does SV target?
Airway epithelium and type II pneumocytes. Type I pneumocytes less severely affected.
How does mouse genotype determine the histologic pattern of pneumonia seen in SV infection?
Susceptible mice (e.g. DBA/2) usually have significant bronchopneumonia and interstitial pneumonia.
The interstitial pneumonia component may be less prominent in resistant mice (e.g. C57BL/6).
How is SV diagnosed?
Clinical signs of respiratory disease are highly suggestive of SV infection.
IFA or ELISA can be used to diagnose the disease. Antibody can be detected 7 days post infection. Histopathology, immunohistochemistry, and viral isolation can be used to confirm the infection. RT-PCR can also be used to detect the disease.
Give the differential diagnosis for SV.
PVM, though the disease is usually milder, and bacterial pneumonias.
How can SV be controlled once found in a colony of mice?
Allow the disease to “burn-out” by having a 4-6 week quarantine period, where no new animals are introduced to the colony either as adults of by breeding.
How can SV infection complicate research?
- immunosuppression
- inhibit growth of transplantable tumors
- pulmonary changes can compromise interpretation of experimentally induced lesions
What type of virus is Pneumonia Virus of Mice?
- enveloped RNA virus
- genus Pneumovirus
- family Paramyxoviridae
- subfamily Pneumovirinae
True or False. Natural PVM infection in mice is asymptomatic.
True.
What are the clinical signs associated with PVM in immunodeficient mice?
Dyspnea, listlessness, and wasting may occur.
PVM causes natural infections of what species?
PVM causes natural infections of mice, rats, hamsters, and possibly other rodents and may be infectious for rabbits.
Describe the gross and histological lesions with EDIM.
- Grossly, lesions are primarily in the gastrointestinal tract, but thymic atrophy can be associated with infections related stress.
- Intestine often distended, flaccid, and filled with grey-green gaseous liquid or mucoid fecal material that soils the pelage.
- Stomach often contains curdled milk
- Virus preferentially infects terminally differentiated enterocytes in SI & LI, which accounts for age-related susceptibility (the number of such cells decreases as intestinal tract matures)
- Villar epithelial cells contain vacuolization with cytoplasmic swelling, giving villi a clubbed appearance
What is the hallmark of MHV infection.
Syncytia at margins of necrosis
What are the differentials for MHV infection?
Other diseases that cause diarrhea, runting or death in suckling mice or wasting disease in immunodeficient mice including, EDIM, mousepox, Reovirus 3, Tyzzer’s disease and salmonella. Mouse encephalomyelitis virus infection and neoplasms should be considered when neuro signs are present.
- inappetance (failure to suckle) is a distinguishing characteristic
What clinical signs are seen with MEV infection?
Flaccid posterior paralysis, which may be preceded by weakness in the forelimbs or hindlimbs. Mice are otherwise alert. Mice die because of the inability to obtain food and water. With recovery, a gait disturbance may be present due to a chronic demyelinating phase.
