Order: Mononegavirales & Family: Paramyxoviridae Flashcards
Where does the name Mononegavirales come from?
mono = single
nega = RNA genome
What 4 families are members of Mononegavirales?
- Paramyxoviridae - parainfluenza, canine distemper, Newcastle disease virus, Hendra, Nipha virus, Rinderpest, measles, mumps
- Filoviridae - ebola
- Rhabdoviridae - vesicular stomatitis virus, rabies virus
- Pneumoviridae - respiratory syncytial virus
Distinguishing characteristics of Mononegavirales families:
Are Paramyxoviruses enveloped? What is their genome like? Where do they replicate?
yes - covered with large spikes
single molecule of helical negative-sense ssRNA with 7-8 ORFs coding for 10-12 proteins (NP, P, M, F, L, HN, H, G)
cytoplasm with budding from plasma membrane
What 2 things are characteristically found in host cells infected by Paramyxovirus?
- syncytium formation
- intracytoplasmic/intranuclear inclusion bodies
Paramyxoviridae vs. Pneumoviridae:
Paramyxoviridae replication:
negative sense (3’ to 5’) to positive sense (5’ to 3’)
Paramyxovirius replication cycle:
negative sense!
What proteins are responsible for attachment, fusion, nucleoprotein formation, transcriptase formation, and matrix protein formation in Paramyxoviridae and Pneumoviridae? What extra proteins does Pneumoviridae have?
- ATTACHMENT (hemagglutinin, induction of immunity): H, G
- FUSION (penetration, spread, induction of immunity): F, F
- NP (protection of genome RNA): N, N
- TRANSCRIPTASE (RNA transcription): L and P/C/V, L and P
- MATRIX (stability): M, M
(both lack neuraminidase)
SH, M2
How do Orthomyxoviruses and Paramyxoviruses compare with respect to viruses, genome, presence of RNA polymerase, capsid structure, envelop presence, size, surface spikes, and giant cell formation?
What are 3 conserved biological properties of Paramyxoviridae?
- CELL FUSION: giant cell formation
- PERSISTENT INFECTION: noncytocidal infection
- ANTIGENIC PROPERTIES: related antigens in measles, canine distemper, rinderpest, mumps, parainfluenza, and NDV
How are Paramyxoviruses able to spread throughout host cells?
budding viruses from infected cell cause viral-infected cells to produce viral fusion proteins (F, NH), causing uninfected cells to bind to and fuse with the infected cell
- SYNCYTIA FORMATION
What animals are affected by Newcastle Disease Virus (NDV)? What may act as carriers? What are 6 common results of infection?
- chickens, turkeys, domestic/wild birds (+ humans)
- sea birds, waterfowl, psittacines (pass in feces)
- greenish-dark, watery diarrhea**
- respiratory and neurological signs
- edema of the head, especially around eyes
- drop in egg production
- death within 24-48 hours, and continuing for 7-10 days
What makes Newcastle Disease Virus (NDV) and Paramyxoviruses especially virulent?
differential HN and F cleavage makes virus polyphasic/polybasic
What are the 3 pathotypes/strains of Newcastle disease virus (NDV) in the US?
- LENTOGENIC - mild pathogenicity (Hitchner B-1, F, LaSota); used for vaccine purposes
- MESOGENIC - moderate pathogenicity (Komarov)
- VELOGENIC - severe pathogenicity (Herts, GB Texas, Melano)
What are the 3 major economic impacts of Newcastle Disease Virus (NDV)?
- high mortality
- decrease in body weight gain
- decrease in egg production
- virulent strains are reportable and can result in trade restrictions
What are the 3 tropisms of Newcastle Disease Virus (NDV)?
- respiratory tract
- GI tract
- nervous system
What are the 5 forms of Newcastle Disease Virus based on their virulence/tropism?
- DOYLE’S FORM: acute lethal infection of all ages; hemorrhages of the digestive tract (very virulent)
- BEACHE’S FORM: acute lethal infection of all ages; respiratory and neurological signs
- BEAUDETT’S FORM: mesogenic, less pathogenic form; death in young birds when used in a vaccine
- HITCHNER’S FORM: lentogenic form; mild respiratory signs (used as a live vaccine)
- ASYMPTOMATIC ENTERIC NDV: enteric form in chiefly gut infection with lentogenic virus
In what 4 ways can Newcastle Disease Virus (NDV) virulence be assessed?
- mean death time (MDT) in chicken egg embryos
- intracerebral pathogenicity index (ICPI) in day-old chicks
- intravenous pathogenicity index (IVPI) in 6-week-old chicks
- intracloacal pathogenicity test in 6-to-8-week-old chicks
What 5 factors affect the severity of Newcastle Disease Virus infection?
- virulence of the virus
- doses and age - some strains require higher doses to infect the host; young are most susceptible
- general health of the birds - stress (malnutrition, parasitism, dampness, environment) = severe long-term course
- immune status of birds - presence of lack of antibodies (vaccination)
- species of birds - chickens > waterfowl/psittacines
Newcastle disease virus (NDV) replication cycle:
How does Newcastle disease virus (NDV) use F and HN proteins to fuse with host cell membranes?
- F trimer is present on the viral membrane surface deactivated, while HN has its 4 heads down
- HN turns its 4 heads up and binds to the host cell sialic acid receptors
- upon receptor binding, F trimer binds to HN
- F is now activated and transforms into the HRA and HRB pre-hairpin intermediate
- refolding of the HRB linker forms a gap and fuses both membranes together
Where does the initial replication of Newcastle disease virus (NDV) occur in the host? What 3 things happen next?
mucosa of the upper respiratory tract
- primary viremia disseminates the virus throughout the body and parenchymal organs
- secondary viremia leads to CNS infection
- 100% morbidity with 90% mortality
What 2 things tend to result in species that show few/no signs of infection with Newcastle disease virus (NDV)?
- carrier state
- cyanosis and edema in ornamental outgrowths (combs and wattles) due to URT mucosa replication
What 3 postmortem lesions are expected in Newcastle disease virus (NDV) infection?
- hemorrhagic internal organs, like tracheal mucosa, proventriculus, and intestinal mucosa - characteristic pinpoint lesions between proventriculus and gizzard
- edema of head and neck
- edema, hemorrhage, necrosis, or ulceration of lymphoid tissue
What are the 8 most common clinical features of Newcastle disease virus (NDV) infection?
- torticollis
- abundant oral secretions
- greenish fecal material
- severe dyspnea and gasping
- hemorrhagic proventricular papillae
- hemorrhagic trachea
- cecal tonsil necrosis
- soft-shelled, roughened, deformed eggs
What is commonly seen in the brain with velogenic/viscerotropic Newcastle disease virus (NDV) infection?
perivascular cuffing (inflammation around blood vessels)
Clinical and pathological features of velogenic viscerotropic Newcastle disease virus (NDV):
A = hemorrhage in lymphoid patch in the lower eyelid (characteristic early feature)
B = focal hemorrhage and necrosis of cecal tonsils
C = hemorrhagic foci in proventriculus
D = mottled spleen with multifocal necrosis
E = paresis
F = brain lesion (gliosis)
G = virual nucleocapsid protein in spleen
H = viral RNA in cecal tonsils
What is exotic Newcastle disease virus (NDV)? What is a hypothesis to its introduction into the US? What is the most common lesion found upon infection?
viscerotropic velogenic strain (VVNDV) causing reportable disease, but not reported in the US
smuggling backyard and gamefowl —> 2002-2003 outbreak in CA, NV, AZ, TX, Mexico
hemorrhagic, ulcerative, and necrotizing lesions in the GI tract epithelium and associated lymphoid tissues
What samples from live/dead birds can be taken for Newcastle disease virus (NDV) diagnosis? What 3 lab tests are commonly done?
LIVE = tracheal, cloacal, and fecal swabs, sera
DEAD = tissues from lungs, kidneys, intestines, spleen, brain, liver, and heart
- serology: hemagglutination inhibition test, ELISA, PCR, sequencing
- pathogenicity assessments: plaque test in chicken embryo fibroblast cultures, mean death time, intracerebral pathogenicity index, intravenous pathogenicity index
- detection of viral nucleic acids by rtPCR
How is Newcastle disease virus (NDV) inoculated? What lesions are seen in embryos?
- into 10-12 days old hen embryonated eggs via CAM or allantoic sac
- grows well on chicken embryo fibroblast cell culture
hemorrhagic lesions with encephalitis and embryo death within 34-72 days
When are Newcastle disease virus (NDV) vaccines given? What is a major drawback?
2-4 weeks of age or at 1 day of age via conjunctiva
- live
- inactivated
- newplex: virus antibody complex
- lentogenic strains (LaSota live attenuated): eye drops, water, spray
- during outbreaks = mesogenic strain IM + booster 3-4 weeks later
vaccine-induced immunity is short-lived = 8-10 weeks due to strain variation in virulence