Virology 2 Study Material PDF

 Family: Poxviridae Subfamily: Chordopoxvirinae Genus: Genus: Molluscipoxvirus Orthopoxvirus Molluscum contagiosum Vaccinia virus C...

 Family: Poxviridae Subfamily: Chordopoxvirinae Genus: Genus: Molluscipoxvirus Orthopoxvirus Molluscum contagiosum Vaccinia virus Cowpox virus Variola virus  Poxviruses are the largest and most complex human viruses.  It include Small pox (variola) , Cow pox, Vaccinia, which are antigenically related, and Molluscum contagiosum virus which causes benign skin warts (shiny, painless papules).  The virus is large brick shape (200 x 400 nm) observed by light microscope, enveloped with inner membrane enclosing the core which is linear DS DNA.  The virus contain all the enzymes necessary for its replication.  It replicate in the cytoplasm forming Guarnieri's inclusion bodies. The disease show a very characteristic skin rash. Structure of a pox virus  Small pox was the most dangerous one ; two variants of the disease exists: variola major and variola minor with mortalities of 25 and 1 % respectively.  1950 (50 million cases per year in the world).  1967 (10 to 15 million cases per year ).  Last case in somalia 1977.  Lab accident in 1978, England.  However, vaccine, prepared from Vaccinia virus, given by skin scarification, has successfully eradicated the virus, in 1980, because:  The smallpox vaccine was the first successful vaccine to be developed.  The process of vaccination was first publicized by Edward Jenner, who acted upon his observation that milkmaids who caught the cowpox virus did not catch smallpox. 1. Small pox is an exclusive human pathogen (no animal reservoir exists). 2. No chronic carrier exists. 3. Single serotype protects against all infections. 4. The disease exhibits visible pustules (allows quarantine and vaccination of contacts). 5. Stable and inexpensive vaccine is available.  Diagnosis:  Treatment: Supportive treatment. Vaccination:  Calf lymph vaccine: prepared by inoculation of Vaccinia virus on shaved skin of calves and collection of vesicle fluid in 40% glycerol and 0.5% phenol.  Lyophilized vaccine (Egg vaccine): prepared from Vaccinia virus in embryonated eggs.  Both vaccines are applied intradermally by scratching. Vaccination by bifurcated needle  Complications of vaccination: 1. Bacterial infection of the vaccination site. 2. Generalized vaccinia: spread of the virus through the blood causing generalized skin lesions. Usually occur in immunocompromised children.  The lesions of this disease are small, pink, wart like tumors on the face, arms, back, and buttocks.  It is more frequent in children than in adults and it spread by direct and indirect contact e.g. barbers, common use of towels. Molluscum contagiosum fleshy lesions with umbilicated centres on the face Laboratory diagnosis: 1. Tzanck test: demonstration of multinucleated giant cells with internuclear inclusion bodies in scrapings from the lesion. 2. Tissue culture: demonstration of cytopathogenic effect on human diploid fibroblasts. 3. Detection of IgM in newborns indicates intrauterine infection.  A large family of viruses having the following common characters: 1. Large enveloped icosahedral with linear DS DNA. The envelop contain spikes. 2. Replication occurs in the nucleus and gain its envelop from the nuclear membrane and is released after cell lysis. 3. Show latent infection (persist indefinitely in hosts with periodic reactivation). 4. Some members are oncogenes (HSV type 2 , EBV). 5. Are susceptible to antiviral chemotherapy.  Members of the family are classified into three group A. alpha [ Herpes Simplex Virus (HSV) types 1 & 2 and Varicella Zoster Virus (VZV)]. B. beta [Cytomegalovirus (CMV), human herpes virus 6 &7]. C. gamma [Epestein-Barr Virus (EBV) ].  HSV type 1 HSV type 2 i. Clinical Painful Ulcers Painful ulcers with symptoms fever & lymphadenopathy ii. Infection Upper part of the body lower part of the site (head, throat, chest) body (genitals) iii. Transmission *By contact (kissing, *By sexual contact. sharing glass). * Infection may be * Primary infection transmitted to occurs in children neonates during 2-3 years old, pregnancy or autoinfection to other delivery. parts of the skin or eyes is possible.  HSV type 1 HSV type 2 iv. Latency: In trigeminal ganglia In sacral ganglia of of enervating neurons enervating neurons v. Oncogenicity No Yes (cervical carcinoma)  HSV-1 & HSV-2 share many characters including DNA homology, antigenic determinants, tropism and symptoms. However, both can be differentiated serologically.  HSV-1 primary infection appears as painful ulcers at any part of the body but usually appears as gingivostomatitis.  Recurrent infection appears at the lips borders as Herpes labialis (cold sores) , infection of fingers (Herpes whitlow) or eye infection (kerato-conjunctivitis) which may led to blindness, skin cause herpatic eczema , and encephalitis with 50% mortality may happen. Herps labialis Herps labialis  Herps Herps whitlow gingivostomatitis Herpatic eczema  Recurrence usually occur at the same primary site and is induced by fever, local trauma, sun light, emotional stress or menstruation.  Recurrence occur in spite of high titre of circulating antibodies i.e. cell mediated immunity plays the main role in protection. Laboratory diagnosis: 1. Tzanck test: demonstration of multinucleated giant cells with internuclear inclusion bodies in scrapings from the lesion. 2. Tissue culture: demonstration of cytopathogenic effect on human diploid fibroblasts. 3. Detection of IgM in newborns indicates intrauterine infection. Tzanck test Treatment Idoxuridine, vidarabine and acyclovir ointments are used for herpatic keratitis. Intravenous acyclovir is useful in encephalitis. Cortisone is contraindicated as anti-inflammatory.  VZV causes varicella (chickenpox) with recurrence causing zoster (shingles) i.e. one virus causing two different diseases.  a. Varicella (Chickenpox) ‫الجديرى‬  Highly communicable respiratory infection, usually occurring in epidemics in winter, very mild when compared to small pox.  Initial replication of the virus occurs in the respiratory tract followed by viremia characterized by fever and skin vesicular rash starting on the trunk and then speeding to the limbs and face vesicular rash is also found on the scalp c.f. other vesicular diseases.  The disease is mild or even asymptotic in children and severe in neonates and adults. Infection usually develops life long immunity.  Antibodies are formed before viremia and cellular immunity before latency. Neonatal chickenpox. Severe varicella occurs in the infant when maternal disease develops between 5 days before delivery and 2 days postpartum Child with varicella Characteristic skin rash of varicella  b. Zoster (shingles) ‫العصب المكشوف او العصب الحى‬  Recurrent endogenous infection for cell mediated immunosuppressed adults.  Disease starts as severe pain due to inflammation of sensory nerves and ganglia and then vesicles (usually in crops c.f. varicella) appears in the enervated area, usually unilateral in trunk. Unilateral herps zoster.  Diagnosis:  Tzanck test: demonstration of multinucleated giant cells with internuclear inclusion bodies in scrapings from the lesion.  Tissue culture: demonstration of cytopathogenic effect on human diploid fibroblasts. Treatment: Chickenpox: calamine lotion or crystal violet Shingles: Acyclovir  Chicken Pox Shingles (Varicella) (Zoster) i. Infection: 1 st droplet or Recurrent contact infection (endogenous infection) (exogenous infection) ii. Intensity: Mild in children, Sever in sever in neonates and immunocompromized less commonly adults. adults iii. Lesions: Itchy vesicular rash Painful vesicles in in trunk then limbs, groups, usually face as well as scalp unilateral, in sensory nerves, ganglia. iv. Time: Cold whether All over the year (winter)  Chicken Pox Shingles (Varicella) (Zoster) v. Treatment: Calamine lotion or Acyclovir crystal violet vi. Diagnosis: Tzanck test and The same culture on human diploid fibroblasts  Small Pox Chicken Pox Cause: Pox virus VZV Incidence: Eradicated Very common Modes of Lesion progress from Lesion appear in stage to another crops evolution: Time of Relatively slow Rapid evolution: Lesions: Deep, scaring Superficial, slightly scaring  CMV is a common human pathogen, infecting about 2.5% of all newborns and about 50% of adults in the developed world.  The virus is transmitted orally, sexually, congenitally and by blood transfusion.  The virus could be isolated from saliva, blood, tears, milk, feces, semen, vaginal and cervical secretions.  Mode of transmission:  Congenital. Acquired infection: a. Perinatal infection. b. Postnatal infection. - Infected secretions. - Blood transfusion. - Organ transplantation.  Clinical pictures:  Usually infection is asymptomatic (normal persons).  Congenital infection may result in microcephaly, jaundice, hepatosplenomegally, respiratory distress, CNS manifestations or mental retardness in newborns.  Activation usually results in pneumonia or disseminated disease (hepatitis, encephalitis...etc.) continue  GIT infection in AIDS patients cause diarrhea.  Laboratory Diagnosis: 1. Detection of cytomegalic cells with internuclear inclusion bodies. 2. Culture: only on human diploid fibroblasts and detection of the characteristic CPE within 1-2 weeks. 3. Increase in specific antibody titer. (it show 4 fold increase). 4. DNA probe.  Treatment:  Ganciclovir is approved for treatment of CMV infection (high resistant).  Live attenuated vaccine that induces both humoral and cellular immunity was developed.  EBV is associated with two diseases 1. Infectious mononucleosis (IM) or kissing disease (glandular fever). 2. African Burkitt lymphoma (ABL). It is also associated with nasopharyngeal carcinoma and B cell lymphoma.  Infectious Mononucleosis (IM)  EBV infection is transmitted by saliva and may remain asymptomatic and become latent in B lymphocytes.  Reactivation starts as pharyngitis with gross elargment of tonsils, lymphadenopathy , splenomegaly , fever and malaise and is rarely fatal in normal individuals.  Chronic EBV infection may result in  a persistent low grade fever and fatigue.  Lymphoma in immunosupressed patients  EBV stimulates B lymphocytes proliferation in cell cultures i.e. immortalize it.   Treatment:  Aspirin is usually enough to control the pain caused by sore throat and lymphoadenopathy.  Corticosteroid course for less than 14 days , in cases of pharyngeal oedema and sever abdominal pain due to splenomegaly/ lymphoadenopathy.  Rupture spleen requires immediate blood transfusion, anti-shock measures, and splenectomy.  African endemic Burkitt Lymphoma  It is a poorly differentiated B-cell lymphoma of the jaw and face that is endemic to the children of the malarial regions of Africa. African Burkitt lymphoma  Burkitt's lymphoma (or "Burkitt's tumor", Burkitt lymphoma or "malignant lymphoma, Burkitt's type") is a cancer of the lymphatic system (in particular, B lymphocytes).  It is named after Denis Parsons Burkitt, a surgeon who first described the disease in 1956 while working in equatorial Africa.  Laboratory Diagnosis: 1. Demonstration of atypical lymphocytes (It is non specific). 2. Paul-Bunnell (Monospot) test: sheep and bovine RBCs + Patient serum (contains heterphile IgM antibodies) Agglutination 3. DNA probe for patients peripheral lymphocytes “specific test”.  They are small icosahedral naked DS DNA viruses.  It Includes two groups A. Papillomaviruse ‫السنطة او نفرة الحمار‬ B. Polyomaviruses  Papillomaviruses  It is transmitted by close contact and infects the epithelial cells resulting in benign outgrowth of cells into warts.  According to its type warts may appear in hand ,foot or head and neck or anogenital.  Persistent cervical infection, may result in cervical carcinoma.  Warts are treated surgically. Common Warts Common Warts  Polyomaviruses  Rarely cause infections in kidneys or lungs in imunocompromised persons.  They are icosahedral naked DS DNA viruses.  They induce latent infection.  Some are oncogenic, but for animals only.  Approximately 100 serotypes were identified from which around 42 infects humans.  Human viruses spread by droplets, contact or oral fecal.  Several diseases are caused by such large number of serotypes, however the following are the most common diseases. i. Acute pharyngitis and pneumonia. ii. Pharyngoconjunctivitis, usually derived from swimming pools in summer. iii. Conjunctivitis or keratoconjunctivitis. iv. Acute hemorrhagic cystitis in children. v. Gastroenteritis. Pharyngoconjunctival fever. Lesions Adenovirus conjuctivitis. Acute of the palate due to infection with onset follicular conjunctivitis adenovirus type associated with preauricular lymphadenopathy and watery