Lec.2 Flashcards
Viral Growth is detected by?
- Cytopathogenic
- Inclusion Bodies
- Hemadsorption
- Interference
- Fluorescent anti-body staining
- Detection of viral Antigens by
serology
Cytopathogenic
cell death (poliovirus), cluster formation
(adenovirus), giant cell formation (measles and mumps viruses) or cell
transformation (tumor viruses).
Inclusion Bodies
observed by light microscope. They are aggregates or just sites of
replication of the virus e.g. cytoplasmic Negri bodies in brain cells of rabies
infected animal, cytoplasmic Guarnieri′s bodies of poxvirus or nuclear bodies of
adenovirus or nuclear and cytoplasmic bodies in case of cytomegalovirus.
Hemadsorption
viruses which contain hemagglutinin spikes are
able to form clumps of RBCs if added to the tissue culture.
Interference
Host cells infected with a virus may acquire resistance to infection by a
second virus, of the same type or another one. Some viruses do not
produce CPE, however, their growth can be proved by their ability to interfere
with another CPE producing virus e.g. rubella and ECHO virus.
Local Infections
- Skin
- Respiratory Tract Infection affecting the mucos membrane
- Alimentary Tract
more than 60% of
diarrhea in infants are caused by
Rotavirus
The virus passes through lymphatics, blood (viremia), tissues or nerves, reaching the target tissue (tropism),
Systemic Infection
What should one take to prevent/before viremic phase
Administration of
neutralizing antibodies before the viremic phase could prevent the development of
the disease.
are characterized by short incubation period and short lasting
immunity
Local Infections
are characterized by long incubation period and
long lasting immunity
Systemic Infections
the virus remain hidden most of the time with intermittent
reactivation and development of the disease
Latent Infections
the virus usually has long incubation period and is always
shedding
Chronic Infection
are viruses with long incubation period and slow multiplication
Slow Infection
many viruses penetrate the placenta during
pregnancy causing congenital defect in the embryo.
Congential/Teratogenic Infection
resulting in transformation of infected cells.Viral
genes become integrated into host cell chromosome
Oncogenicity (tumor causing)
s, viral RNA acts as a template for synthesis
of viral DNA- through the action of reverse transcriptase. The DNA copy of the
viral RNA is integrated into the host cell chromosome
RNA tumor viruses
Epidemiology of viral Infections?
- Direct contact ( sexual transmission)
- Droplet Infection ( respiratory)
- Oral Fecal Infection (feces-flies-food-finger - 4F)
- Skin Puncture
Skin puncture through?
- Injection Hepatitis B
- Anthropods Yellow Fever
- Animal Bites Rabies Virus
- Agents preventing attachment
- Agent preventing uncoating
- Agents inhibiting the replication
- Agents preventing attachment (ie. neutralizing antibodies)
- Agent preventing uncoating (Amantadine and Rimantadine)
- Agents inhibiting the replication (—– &Interferons)
Inteferons are all non-specific except?
gamma which is specific.
They are species specific
Human Interferons
MOA Interfons?
They act by inhibiting the translation of viral mRNA, without affecting
the translation of human cellular mRNA, by attaching to certain cell surface
receptors triggering the formation of intracellular kinase.
Used mainly for prophylaxis in hepatitis B to delay the appearance of liver
cancer
Interferons
Measurement of viral antigen
(total count = active + inactive)
Measurement of infectivity
(active only)
How is viral antigen measured?
Electron Microscopy and Hemagglutinin
How is infectivity measurement calculated
- Cultivation and Enumeration of CPE
- Animal Inoculation nd determination of Lethal Dose (50)
pregnant lady infected with rubella should
get an abortion done
Diseases associated with high mortality
AIDS- yellow fever
Chronic Carriers
Hepatitis B
nosocomial infections?
Influenza
Lab diagnosis is depended on ?
- Microscopical examination to detect inclusion bodies
- Cultivation in tissue culture/chick embryo
- Serological Test (ie, ELISA/ Immunofluorescence)
- Detection of viral genetic Material
How is viral genetic material detected?
PCR, Electrophoretic Separation of RNA, Electrophoretic Separation of Restriction endonucleases
are the largest and most complex human viruses
Poxviruses
Examples of Proxvirus?
small
pox, cow pox, vaccinia
Causes Benign Skin warts
molluscum contagiosum ( PoxViruses)
The virus is large brick shape (200 x
400 nm) observed by light microscope,
enveloped with inner membrane enclosing
Smallpox (variola)
linear DS DNA
Smallpox (variola)
Eradication of small pox was successful because?
- Small pox is an exclusive human pathogen.
- Single serotype protects against all infections.
- The disease exhibits visible pustules (allows quarantine and
vaccination of contacts), with no chronic or asymptomatic carriers. - Stable and inexpensive vaccine is available.
How is small pox transmitted?
Refer to pg.12
Day 12: ppl with small pox experience?
fever, rash, headache
Complications of vaccinations include:
a- bacterial infection of the vaccination site.
b- Generalized vaccinia: spread of the virus through the blood causing generalized
skin lesions.
How are small pox vaccination administered?
Intradermally by scratching
2 types of vaccination
- Calf lymph vaccine
- Lyophilized vaccine
prepared from vaccinia
virus in embryonated eggs
Lyophilized vaccine
prepared by inoculation of
vaccinia virus on shaved skin of calves.
- Calf lymph vaccine:
Human Herpes Viruses
- Large enveloped icosahedral with linear DS DNA
- Replication occurs in the nucleus and gains its envelope from the nuclear membrane and is
released via tubules or vacuoles that communicate with the exterior. - Show latent infection
- Some members are Oncogenes
- Susceptible to anti-viral chemotherapy
Human Herpes Viruses?
- Alpha: Type 1 and Type 2 & Varicella Zoster
- Gamma: affects B-lymphocytes and Epithelial cells
- Beta: Monocytes and Lymphocytes
