VARICELLA-ZOSTER VIRUS ( VZV ) (HHV3) Introduction Varicella - zoster virus (VZV) Virus causes two different diseases. Virus causes two different diseases. I. Varicella (chickenpox) Acute mild highly contagious disease, occur in epidemics, among children result from primary infection with the virus. Latent in sensory ganglion. Latent in sensory ganglion. II. Zoster (shingles) Response of the partially immune host to reactivation of varicella virus present in a latent form in sensory ganglion result in zoster. Response of the partially immune host to reactivation of varicella virus present in a latent form in sensory ganglion result in zoster. Sporadic disease of adults. Sporadic disease of adults. Characterized by vesicular cutaneous rash limited in distribution to part of the skin innervated by a single sensory ganglion. Characterized by vesicular cutaneous rash limited in distribution to part of the skin innervated by a single sensory ganglion. Properties of the virus VZV is morphologically identical to HSV. (spherical, nm in diameter, enveloped virus), icosahedral nucleocapsid. Genome: ds DNA, size 125 kbp. Electron micrograph of VZV particles. Cytopathic changes are more focal & tend to spread much more slowly than those induced by HSV. Pathogenensis Source Patients with varicella or zoster lesion (highly contagious). Mode of transmission Respiratory droplet. Respiratory droplet. Route of entry Mucosa of upper respiratory tract or conjunctiva. Replication Replicate first locally in the regional lymph node. Replicate first locally in the regional lymph node. Spread After local replication in the regional LN, the virus circulate in the blood ( primary viremia), to invade & replicate in the liver & spleen, followed by secondary viremia. After local replication in the regional LN, the virus circulate in the blood ( primary viremia), to invade & replicate in the liver & spleen, followed by secondary viremia. Lastly the virus localize in the skin & mucous membrane (target organ). Lastly the virus localize in the skin & mucous membrane (target organ). Lesion in target organ Skin & mucosal lesions initiated by viral infection of capillary endothelial cells & epidermal cells, result in swelling of epithelial cells, ballooning with accumulation of tissue fluid (vesicle formation). Skin & mucosal lesions initiated by viral infection of capillary endothelial cells & epidermal cells, result in swelling of epithelial cells, ballooning with accumulation of tissue fluid (vesicle formation). Sever form varicella Occur in neonates, or IC. patients, here varicella lesion can occur in other organ like liver & lungs with multinucleated giant cells. Occur in neonates, or IC. patients, here varicella lesion can occur in other organ like liver & lungs with multinucleated giant cells. Viral shedding Respiratory secretions. Respiratory secretions. Latent The virus become latent in the dorsal root sensory ganglion. The virus become latent in the dorsal root sensory ganglion. Reactivation Trigger factor is weaning of immunity, allows viral replication to occur in dorsal root ganglion result in Trigger factor is weaning of immunity, allows viral replication to occur in dorsal root ganglion result in 1- Acute inflammation in the sensory nerves & ganglia. 1- Acute inflammation in the sensory nerves & ganglia. 2- Distribution of lesion in the skin (vesicles) corresponds closely to the area of innervation from an individual dorsal ganglion ( dermatomal distribution). 2- Distribution of lesion in the skin (vesicles) corresponds closely to the area of innervation from an individual dorsal ganglion ( dermatomal distribution). Clinical findings I. Varicella ( chickenpox) Mild disease among children. Mild disease among children. Sever disease occur in immunocompromised patients & neonates. Sever disease occur in immunocompromised patients & neonates. Incubation period is days. Subclinical varicella is unusual. Characterized by fever, generalized vesicular eruption of skin & mucous membranes. Characteristics of rash: vesicular, generalized on the trunk, then on the face, limbs, buccal & pharyngeal mucosa in the mouth. All stage of skin lesion macules, papules, vesicles & crusts seen at one time. The rash lasts about 5 days, & most children develop several 100s skin lesions. Complications Rare in normal children, include Rare in normal children, include 1- Encephalitis especially in neonatel varicella (limited immunity), mortality 30%. 1- Encephalitis especially in neonatel varicella (limited immunity), mortality 30%. 2- Varicella pneumonia most common complication in neonates, adults, immunocompromised patients, with primary infection. 2- Varicella pneumonia most common complication in neonates, adults, immunocompromised patients, with primary infection. II. Zoster (shingles) Usually occur in immunocompromised, but occasionally develops in healthy adults. Usually occur in immunocompromised, but occasionally develops in healthy adults. Starts with sever pain in the area of skin or mucosa supplied by one or more groups of sensory nerves & ganglia (often only a single ganglion involved). Starts with sever pain in the area of skin or mucosa supplied by one or more groups of sensory nerves & ganglia (often only a single ganglion involved). The trunk, head,& neck are most commonly affected, with ophthalmic branch of trigeminal nerve involved in 10-15% of cases. The trunk, head,& neck are most commonly affected, with ophthalmic branch of trigeminal nerve involved in 10-15% of cases. Within a few days a crop of vesicles appears over the skin supplied by the affected nerves (dermatomal distribution). Within a few days a crop of vesicles appears over the skin supplied by the affected nerves (dermatomal distribution).Complications 1- Post-herpetic neuralgia Common, protracted pain that may continue for months. 1- Post-herpetic neuralgia Common, protracted pain that may continue for months. 2- VZV pneumonia 2- VZV pneumonia Responsible for deaths that occur in immunosuppressed patients with zoster (< 1% of patients). Responsible for deaths that occur in immunosuppressed patients with zoster (< 1% of patients). Chicken pox Shingles Laboratory Diagnosis Diagnosis is clear from clinical presentations. Samples: vesicle fluid & scrapings form the base of skin lesions. I. Direct Methods 1. Cytology 1. Cytology Smears from base of the lesions will reveal characteristic multinucleate giant cells ( Tzanck smear). Smears from base of the lesions will reveal characteristic multinucleate giant cells ( Tzanck smear). 2. Electron microscopy Herpesviruses can be recognized by the morphologic appearance of the viral particles in vesicular fluid examined by EM. 2. Electron microscopy Herpesviruses can be recognized by the morphologic appearance of the viral particles in vesicular fluid examined by EM. 3. Immunofluorescence cytology Smears from the lesions can be examined by immunofluorescence to detect VZV antigen. 3. Immunofluorescence cytology Smears from the lesions can be examined by immunofluorescence to detect VZV antigen. 4. PCR 4. PCR PCR assays for VZV available & have been used in the diagnosis of VZV encephalitis from CSF specimens. PCR assays for VZV available & have been used in the diagnosis of VZV encephalitis from CSF specimens. II. Virus isolation Type of cell culture is human fibroblasts, for the identification of VZV replication: identification of VZV replication: 1- CPE produced by VZV is produced within 3-7 days, consists of a typical ovoid focal pattern. 1- CPE produced by VZV is produced within 3-7 days, consists of a typical ovoid focal pattern. 2- Immunofluorescence of the cell sheet by monoclonal antibodies is the method of choice for identification. 2- Immunofluorescence of the cell sheet by monoclonal antibodies is the method of choice for identification. III. Serology 1- Specific VZV IgG in paired acute & convalescent sera. 2- Specific VZV- IgM. Techniques Complement fixation test (CFT) most frequently used test. It is perfectly adequate for the diagnostic purposes. Immunofluorescence test (IF) more sensitive than CFT. Enzyme immnuoassay (EIA) These are the most sensitive methods available & therefore are the preferred method. These are the most sensitive methods available & therefore are the preferred method. Epidemiology Varicella is highly communicable, common epidemic disease of childhood (mostly in children < 10 years), adult cases do occur. More common in winter & spring. Spread airborne droplets. Patients are infectious shortly before the appearance of vesicles to about 5 days later. Zoster occur sporadically, chiefly in adults without seasonal prevalence. Prevention 1- A live attenuated varicella vaccine was approved in 1995 for general use. The vaccine is highly effective in children (80-85%), but less in adults( 70%). Isolation of patient with varicella from exposed to IC patients & neonates, because of serious squeals of pneumonia, encephalitis & death. IC. patients exposed to varicella, VZV.Ig & acyclovir administration used to modify the disease (prophylactic use). Treatment: 1- Varicella in normal children is mild disease & require no treatment. 2- Sever varicella ( neonates, immunocompromised patients ) is potentially fatal that require treatment 3- Varicella zoster immune globulin used to prevent the development of the illness, & has no therapeutic value once the varicella has started. 4- Infants born to women with peripartum chickenpox (from 5 days before delivery), VZIG to infant reduces severity & mortality of neonatal infection. 5- Antiviral compound shown to be effective including: Acyclovir ( treatment of choice). Famciclovir. Valacyclovir. Foscarnet. Acyclovir ( treatment of choice). Famciclovir. Valacyclovir. Foscarnet. Epstein-Barr virus (EBV)(HHV4) Introduction Epstein Barr virus (herpes virus) is a causative agent: 1- Primary infection: result in a disease called Acute infectious mononucleosis (heterophile positive disease). mononucleosis mean polyclonal stimulation of B lymphocytes. 2- Latent: B Lymphocytes. 3- Re-activation : EBV is a factor in development of Naso-pharyngeal Carcinoma. Burkitts Lymphoma. Burkitts Lymphoma. Properties of the virus 1- EBV have the general properties of herpesviruses (spherical, large size, enveloped, with icosahedral nucleocapsid, DNA virus). 2- Genome is DNA, contain 172 kbp. 3- Viral antigens: Latent antigen: (produced by latently infected B cells, include EBNAs, and LMPs, there presence indicate that EBV genome is present). Early antigen: (non structural protein, it indicate the onset of productive viral replication). Late antigen: (Structural protein and viral capsid antigen and viral envelope glycoproteins). Latent antigen: (produced by latently infected B cells, include EBNAs, and LMPs, there presence indicate that EBV genome is present). Early antigen: (non structural protein, it indicate the onset of productive viral replication). Late antigen: (Structural protein and viral capsid antigen and viral envelope glycoproteins). 4- Target cell for EBV is the B lymphocyte. Pathogenesis of Infectious Mononucleosis Source: Human with viral excretion in saliva, patients shed low levels of virus for weeks to months after infection. Mode of transmission: EB virus is transmitted by infected saliva & respiratory droplets. (kissing disease). Initial viral replication occur in epithelial cells of the oropharynx or surface B lymphocytes, & salivary glands. Interaction of EBV virus with cellular receptor: The EBV initiate infection by binding to viral receptors on B cells (CR2 or CD21). The EBV initiate infection by binding to viral receptors on B cells (CR2 or CD21). Spread: virus is spread by blood stream & disseminated through the body to liver, spleen, & lymph nodes. The proliferation & expansion of EBV infected cells with activated T- cells result in enlargement of these organ. The proliferation & expansion of EBV infected cells with activated T- cells result in enlargement of these organ. Most people shed the virus in saliva for weeks to months after infection. Latent phase: Latent site lymphoid cells, small number of infected lymphocytes persist for lifetime of the host (one in 10 6 of B cells ). Latent site lymphoid cells, small number of infected lymphocytes persist for lifetime of the host (one in 10 6 of B cells ). Reactivation of EBV: evident by Increased of virus in saliva & usually is clinically silent. Reactivate infection in immunocompromised (immunosuppressive drugs, or diseases) carries serious consequences. The EBV infected B lymphocytes express differentiated functions : 1- Secretion of immunoglobulin: 1- Secretion of immunoglobulin: IgA & IgG are common, whereas IgM synthesis is rare. IgA & IgG are common, whereas IgM synthesis is rare. Auto antibodies are typical of the disease, like rheumatoid factor, antinuclear antibodies. Auto antibodies are typical of the disease, like rheumatoid factor, antinuclear antibodies. Heterophil antibodies that react with antigen on sheep erythrocytes. Heterophil antibodies that react with antigen on sheep erythrocytes. 2- Expressed B-cell activation products e.g CD Expressed B-cell activation products e.g CD Expression of viral gene in the infected cells including six different EBV antigens ( EBNA1-6) and two latent membrane proteins (LMP1, LMP2). 3- Expression of viral gene in the infected cells including six different EBV antigens ( EBNA1-6) and two latent membrane proteins (LMP1, LMP2). 4- Few infected B-cells release virus particles (