Microbiology Exam 3: Cusick

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Papoviruses

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-Includes Papilloma Viruses and Polymavirus families
-Human papillomaviruses (HPV): Cause warts and cervical cancer. Group #'s 16 and 18 strongly associated. >40% of adults have a HPV strain in oral mucosa can produce oral lesions; oral papillomas, oral carcinomas.
-Polymavirus: includes SV40 -prototypical oncogenic virus though does not cause cancer in humans

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Human papillomaviruses (HPV)

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-A papovirus (along with polymavuruses)
-Cause warts and cervical cancer.
->40% of adults have a HPV strain in oral mucosa can produce oral lesions; oral papillomas, oral carcinomas.
-small icosahedral capsid, double stranded circular DNA genome
-replicated and assembled in nucleus
-acquired by close contact, sexual contact also by fomites (towels),
-non enveloped so more resistant
-viruses encode oncogenes -proteins promote cell growth by binding and inhibiting p53 and Rb
-can cause lytic, persistent or latent infections can immortalize cells
-can cause warts- benign, self-limited proliferation of skin warts can be removed with liquid nitrogen (cryotherapy) or chemical means
-HPV groups #16,18 associated with cervical cancer
-Pap smears (Papanicolaou-stained cervical) smears used to detect cytological changes of epithelial cells characteristic of HPV infected cells (produce an excess of keratin)
-DNA molecular probes and PCR also used to detect
-can be treated by removal, or stimulators of the immune system

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Adenoviruses

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-naked medium-sized viruses
-linear, double-stranded genome
-icosahedral nucleocapsid
-transmitted by aerosol droplet, fecal-oral route
-being considered for gene therapy--example; encode wild-type CFTR gene in harmless adenovirus
-infect this virus into Cystic Fibrosis patient
-if lung cells become infected, can begin expressing WT CFTR gene
-clinical symptoms of Cystic Fibrosis could be cured
-Adenovirus associated diseases:
acute respiratory infections -most common infection an influenza like illness
acute contagious conjunctivitis (pink eye)
pharyngoconjunctival fever -a disease of infants characterized by fever, pharyngitis and conjunctivitis
gastroenteritis
frequently cause subclinical infections in adults

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The Human Herpesvirus family

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--large sized enveloped viruses--as with most other enveloped viruses
-killed by 70% isopropyl alcohol
-icosahedral nucleocapsid
-linear, double-stranded DNA
-replicate in the nucleus of the host cell
-have ability to establish latent infections
-can cause various types of oral infections
-cell mediated immunity important to resolve
-Diseases:
-HSV type 1: gingivostomatitis
-HSV type 2: herpes genitalis
-Varicella Zoster Virus: Chickenpox/Shingles
-Epstein Barr Virus: Infectious mononucleosis
-Cytomegalovirus: congenital abnormalities
-Human herpes virus 8: Kaposi's sarcoma.

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HSV type 1

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-Human herpesvirus family
-Primary Infection: Most kids wont present symptoms. If do: mild case of flu (fever, chills, malaise), or acute primary herpetic gingivostomatitis (like cold sores, but from initial infection--and with gingivitis. Small yellowish vesicles form which produce painful ulcers upon rupturing). Primary symptoms can last 2-3 weeks. Treatment is just supportive--relieve pain, and make sure kids drink even though painful)
-Latent infection: Resides in trigeminal ganglion. Reappears as cold sores. (recurrent herpes labialis) Emotional stress, trauma, or excess sun exposure can trigger. Treatment: Acyclovir 5% ointment (zovirax) can reduce sores. Recurrent infection can cause encephalitis?
-Worse complications of HSV 1 are possible if spreads to brain or eyes (keratoconjuctivitis) of newborn or immunosuppressed.
-Lesions generally above waist.
-Diagnosis: Multinuclear giant cells in scrapings. Viral antigens found with immunofluorescence. Serotyping and DNA homology needed to distinguish from HSV 2.
-Herpetic Whitlow: infection of fingers.

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HSV type 2

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-Human Herpesvirus family
-Causes herpes genitalis--spread by sexual contact. Affects mucosa of genital and anal regions.
-Becomes latent in lumbar and sacral ganglia.
-Can be dangerous if pregnant--virus can be transmitted to child's eyes or CNS during vaginal delivery. C-section prevents.
-Treatment: Acyclovir (ACV) and various derivitives, nucleoside analogs. (valacyclovir, penciclovir)
-Lesions generally below waist.
-Often no symptoms shown.

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Varicella Zoster Virus

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-Human herpesvirus family
-Chickenpox-->Shingles
-very contagious-may be spread by direct contact or droplets
-90% of all chickenpox occur in children under 9 years
-Local lesions occur in the skin after dissemination of the virus through the body
-lesions become encrusted and fall off in about one week
-latent infection can form in trigeminal ganglion or sacral ganglia
-initially infects mucosa of respiratory tract
-spread by reticuloendothelial system (macrophages) & Viremia
-primary infection more severe in adults, can lead to pnemonia sometimes fatal
-Shingles: reactivation of earlier infection. (2 different diseases in different age groups caused by same virus.) Predominantly an adult disease arising from childhood chickenpox infection. virus travels to ganglia to set up latent infection. reactivated by stresses similar to herpes. depressed immune system will activate in elderly. painful vesicles that occur on skin or mucosal surfaces along distribution of a sensory nerve. reactivation rarely causes disseminated disease. vesicular lesions commonly confined to particular area

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Epstein Barr Virus

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-Human Herpesvirus family
-Causes infectious mononucleosis: Can also be caused by CMV. Symptoms: high temps, sore throat and lymph glands (neck), general malaise. Transmitted by salive (kissing disease), mostly teenagers.
-Diagnose by positive heterophile test-- tests for heterophile antibodies (IgM).
-Causes hairy leukoplakia--white non-malignant lesions on tongue. Basically always in immunosuppressed. (AIDS)
-EBV is associated with Burkitt's Lymphoma--the most common neoplasm in children where EBV is endemic. A form of non-Hodgkins Lymphoma. (characterized by the absence of Reed-Sternberg cells (Hodgkin’s has RS cells).
-Also associated with Nasopharyngeal carcinoma.

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Cytomegalovirus

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-Human Herpesvirus family
-Large, dsDNA virus, enveloped
-Can be contracted in womb from mother--causing all kinds of congenital abnormalities including mental retardation, and problems with vision, hearing, etc. Major cause of birth defects in developed countries.
-Otherwise: many forms of disease. Especially a problem if have HIV.
-Can also cause mononucleosis.
-Women often show no symptoms.
-Acquired from blood, tissue, bodily secretions. (orally, sexually, etc)
-Establishes latency in immune cells

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Human Herpesvirus 8 (HHV8)

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-Causes Kaposi's Sarcoma: a tumor caused by the virus.
-Kaposi's often manifests as red/purple papules on skin. Also shows up in mouth 30% of the time--especially on palate, and sometimes on gums. 15% of the time it shows up first in the mouth.

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Poxviruses

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-linear, dsDNA virus, enveloped
-multiply in cytoplasm of host cell only time in which DNA synthesis occurs in cytoplasm
-encodes for DNA & RNA polymerases , nucleotide scavenging enzymes
-the largest of the viruses, very complex
-includes: variola viruses (smallpox), vaccinia virus -cowpox-used for gene therapy strategies, molluscum contagious virus (MCV) –STD
-small pox replication cycle: nucleus is Not involved in replication cycle of a DNA virus
-Spread of smallpox within body:
transmitted predominantly by inhalation. Replicates initially in upper respiratory tract. Disseminates through macrophages (lymphatic system) & by entering blood system (viremia). Characteristic rash formed upon spread to skin. Either death or recovery with prolonged immunity result
-Smallpox eradicated from globe, not terrorist threat
-Smallpox-acute, highly infectious, often fatal variola major strain -most lethal;
-other poxviruses:
--Molluscum contagiosum- causes wart like lesions--transmitted by close contact, sex, fomites (towels)
--Vaccinia virus -causes cowpox. Used as vaccine for smallpox word “vaccine” comes from the word for cow
--Monkeypox- similar virus, causes milder symptoms than smallpox

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Parvoviruses

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-smallest of the DNA viruses, single stranded
-can only replicate in actively growing cells--bone marrow cells, erythroid cells, leukemia cells etc.
-B19 strain- causes human disease
-cytolytic for erythroid precursor cells
-initial viremia and viral replication can cause anemia, and flu-like symptoms
-2nd stage caused by immune response; arthritis, or rash on face “slapped cheek” appearance most individuals experience subclinical infection
-serious complications can result from infection of individual who is already anemic (Sickle-cell anemia)

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Picornavirus Family

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-Polio virus -member of Enterovirus genus
-Coxsackie virus-member of Enterovirus genus
-Rhinovirus virus-member of Rhinovirus genus
-Hepatitis A virus-member of Heparnavirus genus
-Characteristics of Picornavirus Family: small (pico), single stranded, + strand RNA viruses, a naked picornavirus genome in cell sufficient to produce virus
-naked icoasahedral capsid structure
-replication cycle occurs in cytoplasm, does not go to nucleus
-enteroviruses and heparnaviruses resistant to acidic pH can be transmitted through GI tract
-rhinoviruses-sensitive to acidic pH
-Pathogenesis of picoviruses: most are very cytolytic except Hepatitis A--not as cytolytic. Paralysis caused by polio results from cytolytic killing of motor neurons
-Vaccine induced antibodies protect

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Poliovirus

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-A Picornavirus
-Positive stranded, SS RNA genome
-3 serological types based on capsid proteins
-Virus has affinity for motor neurons--causes paralysis
-transmitted by water with fecal contaminants
-replicates in the mucosa of the pharynx and GI tract before entering bloodstream
-travels to CNS to infect motor neurons of spinal chord
-initial symptoms; headache, vomiting, constipation and sore throat
-Paralysis or death may follow; asymmetric and flaccid paralysis
-Polio virus replication: all steps of replication occur in cytoplasm
-viral protease degrades CAP binding protein of ribosome
-CAP-modified nucleotide required for initiating eukaryotic translation
-translation of host proteins inhibited
-Polio virus contains unusual ribosome binding mechanism allows to translate its own proteins while host translation inhibited
-IPV -Inactivated Polio Vaccine –Salk: not as efficient at generating antibodies as Sabin
-OPV- Oral polio vaccine –Sabin. Mimics natural infection, produces better antibody response
-shed in feces of vaccinated person, good and bad--bad since immunocompromised persons can get polio from exposure certain % of other people will get polio from OPV vaccine
-most deaths result from respiratory complications iron lung used to treat

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Coxsackie Virus

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-very small, non-enveloped
-positive, SS RNA
-Hand, foot and mouth disease-associated with Type A Coxsackievirus
-causes fever, malaise, headache, vesicles that are painful appearing on palms, soles and the oral mucosal area
-belong to picornavirus family
-divided into 2 groups (A and B) based on lesions observed
-A- cause herpangina and hand-foot and mouth disease oral lesions of herpangina; throat, palate, or tounge
-oral lesions of hand-foot-mouth-buccal mucosa and gingival can distinguish two based on location of oral lesions
-lesions also found on hand and foot
-B-cause pleurodynia -devil’s grip- acute case of fever & chest pain
-myocarditis and pericarditis -inflammation of heart area
-juvenile diabetes -infect pancreatic beta cells

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Rhinoviruses

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-Picornoviruses
-small, ss rna, naked, icosahedral capsid
-main cause of common cold & upper respiratory tract infections
-over 100 serological types; why no vaccine for common cold
-sensitive to acidic pH, therefore not transmitted through GI tract
-transmitted by aerosols, person to person spread and fomites (door knobs sick person touched etc.)
-non-enveloped

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The Retroviruses

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-carry reverse transcriptase in genome
-enveloped viruses, “spikes”-glycoproteins used for attachment
-3 main groups of retroviruses;
1. oncovirus group (HTLV) - produce leukemias, lymphomas. truly oncogenic directly transform cells
2. lentivirus group (HIV) neurological & immunosuppresive. cause cancer primarily by suppressing immune system.
3. spumavirus group -no known human pathogens
-Human Immunodeficiency Virus (HIV) results in Acquired Immunodeficiency Syndrome (AIDS). enveloped, single stranded, + RNA retrovirus

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HIV/AIDS

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-Human Immunodeficiency Virus (HIV) results in Acquired Immunodeficiency Syndrome (AIDS)
-enveloped, single stranded, + RNA retrovirus
-kills helper (CD4) T cells and macrophages
-other cells infected: neuron cells, bone marrow cells, spleen cells
-destroys both cellular & humoral branches of specific immunity
-“full-blown AIDS”- causes dramatic immunosuppression
patients susceptible to wide variety of opportunistic infections
-Syndrome describes plethora of possible infections & symptoms
-gag- encodes for structural proteins
-pol-reverse transcriptase
-env-encode for envelope proteins
-repeats at end of genome used to integrate into host chromosome
-Mechanisms of HIV transmission: HIV carried in semen, serum, amniotic fluid, breast milk but NOT saliva. heterosexual transmission becoming more common
-HIV initially infects macrophages-binds CD4. macrophage infected cells can help transport throughout body
-an HIV infection of nervous system results in high mortality
-gp-120 glycoprotein of HIV used as attachment protein frequent rate of mutation makes vaccine creation difficult
-CCR5- of macrophages used as co-receptor-helps promote fusion
-HIV initially infects macrophages, progresses to gp-120 form that predominantly infects T-helper cells
-mutations in gp-120 result in increased affinity for CXCR4-chemokine receptor of T-helper cells
-knocking out T-helper cells destroys both humoral and cellular immunity
-life cycle of HIV inside macrophage or T-cell: HIV can slowly bud from cell or create multinucleated giant cells.
Malignant neoplasms associated with AIDS:
1. Kaposi’s Sarcoma- malignant neoplasm originating in blood vessels predominantly from the skin. characterized by abnormal vascular proliferation (cancer of the lining of the blood vessels). occurs on multiple sites, particularly lower extremities. spreads from initial nodules to lymph nodes and internal organs.
-HIV diagnostic tools: ELISA used as initial test, confirmed by Western blotting. an HIV+ test of a newborn baby only demonstrates mother infected (if baby remains HIV+ for over 6 months, then +)
-giant cell (syncytial) formation a characteristic CPE
-Examples of anti-HIV therapeutics: Nevirapine-directly inhibits Reverse Transcriptase
-Reverse Transcriptase: a combination of RNA-dependent-DNA polymerase AND RNAse H activity (to degrade initial RNA strand)

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Hepatitis

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-Symptoms associated with Hepatitis: fever, malaise, abdominal pain, anorexia, nausea, chills. hepatomegaly (enlarged liver). jaundice (yellowish color due to bile pigments). darkened urine (increased bilirubin). lymphadenopathy, muscle pain, weight loss, joint pain
-some recover, others develop chronic liver disease: 1. cirrhosis - can result in obstruction of portal circulation. 2. hepatomoic carcinoma
-increased serum levels of liver enzymes (due to liver cell damage) transaminases etc.
-incubation periods may differ among different viral strains
-Manifestations of hepatitis induced liver failure: decrease liver’s ability to store glycogen, regulate blood glucose levels. impair bilirubin metabolism. bilirubin a product of heme degradation. inhibition of urea synthesis (excess ammonia can be fatal)

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Hepatitis A

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-a ssRNA virus
-transmitted by fecal-oral route, viral particles shed in feces
-most common among young adults
-shellfish from contaminated water can cause as well as contaminated water, milk, food
-asymptomatic carriers preparing food & drinks (Ashton Kutcher)
-initial symptoms of hepatitis occur after an incubation period of around 3-6 weeks
-infections often self-limiting, recovery can occur within 4 months -low mortality rate
-more heat resistant than HIV virus, autoclaving recommended
-commonly found in younger individuals especially in populations with poor sanitation
-inactivated (killed) HAV vaccine offers good protection

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Hepatitis

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-Symptoms associated with Hepatitis: fever, malaise, abdominal pain, anorexia, nausea, chills. hepatomegaly (enlarged liver). jaundice (yellowish color due to bile pigments). darkened urine (increased bilirubin). lymphadenopathy, muscle pain, weight loss, joint pain
-some recover, others develop chronic liver disease: 1. cirrhosis - can result in obstruction of portal circulation. 2. hepatomoic carcinoma
-increased serum levels of liver enzymes (due to liver cell damage) transaminases etc.
-incubation periods may differ among different viral strains
-Manifestations of hepatitis induced liver failure: decrease liver’s ability to store glycogen, regulate blood glucose levels. impair bilirubin metabolism. bilirubin a product of heme degradation. inhibition of urea synthesis (excess ammonia can be fatal)

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Hepatitis A

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-a ssRNA virus
-transmitted by fecal-oral route, viral particles shed in feces
-most common among young adults
-shellfish from contaminated water can cause as well as contaminated water, milk, food
-asymptomatic carriers preparing food & drinks (Ashton Kutcher)
-initial symptoms of hepatitis occur after an incubation period of around 3-6 weeks
-infections often self-limiting, recovery can occur within 4 months -low mortality rate
-more heat resistant than HIV virus, autoclaving recommended
-commonly found in younger individuals especially in populations with poor sanitation
-inactivated (killed) HAV vaccine offers good protection

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Hepatitis B

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-A partially double stranded DNA virus: only hepatitis virus that is double stranded DNA; synthesis of DNA from RNA interrupted by production of virion, DNA synthesis completed upon infection of next host cell
-member of Hepadnavirus family
-less easily transmitted than hepatitis A, though B more severe
-vaccination - produces Anti- HBSAg antibodies--antibodies directed against hepatitis surface antigen
-Dane particle -describes infectious virion contains nucleic acid + protein shell
-excess production of protein shells result in production of empty spheres and filaments of protein coat can serve as decoy to divert immune system
-HBV is the most infectious bloodborne pathogen known! infection control precautions aimed at Hepatitis B have been shown to be successful against HIV and Hepatitis C
-tropism is specific for liver cells
-unusual replication cycle, replicates through RNA intermediate. Encodes for reverse transcriptase even though DNA virus!!
DNA can integrate into liver cell to cause persistent infection
integrated Hepatitis B. DNA has been detected in
-3 main modes of transmission; 1. blood (needlesticks, IV drug use), 2. sexual intercourse, 3. perinatally from mother to newborn
-incubation period averaging 1-6 months (longer than Hepatitis A)
-easier to obtain as dentist than HIV
-HBV concentrations in blood usually higher than HIV
-Chance of getting Hep B = 30% if needle stick, etc. Chance of getting HIV = .3% if stuck. Hep C is 3%.
-can result in a carrier state or chronic liver disease
-most likely transmission of Hepatitis B or C to dentist from patient is through a needlestick
-Replication of Hep B virus: DNA genome → RNA genome and then back to DNA genome via reverse transcriptase. Many non-infectious particles produced
-Acute vs. chronic hep B virus infection: Cellular immunity important for preventing chronic infection. a HBV carrier who experiences a subsequent infection with Hepatitis D -sever hepatitis. Primary Hepatocellular Carcinoma (PHC)--caused by integration of HBV genome, caused presumably by constant liver damage and regeneration of liver tissue
-Hepatitis B virus immunity: 1. HbsAg- HBV surface antigen--presence in blood indicates chronic infection. Anti-HbsAg (antibody) indicates either previous infection or immunization. 2. HbcAg - core antigen. Antibodies not raised against from vaccine, so indicates previous or current infection
-HBV vaccine will prevent PHC therefore anti cancer too!

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Hepatitis C virus

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-most common cause of transfusion-mediated hepatitis
-persons receiving blood transfusions at risk, persons receiving tattoos, body piercings from unsterilized needles
-death from hepatitis C effects on liver usually result from inhibition of urea synthesis
-Hepatitis C major risk factor for hepatocellular carcinoma and also a major risk factor for chronic hepatitis
-a flavivirus with + sense SS RNA genome
-envelope consists of LDL, VLDL (LDL, VLDL permit receptor mediated endocytosis in liver cells)
-transmitted primarily in infected blood, and sexual contact also in semen and vaginal secretions
-high % of asymptomatic carriers aids further transmission
-HCV- 3 types of diseases; alcohol, medications can exacerbate
- ≈15% acute hepatitis, cell-mediated immunity may resolve
- ≈70% chronic persistent infection, possible progression later to chronic active hepatitis, cirrhosis, liver failure
- ≈15% rapid progression to cirrhosis

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Hepatitis D

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-requires Hepatitis B virus
-only found in individuals with acute or chronic infections of Hepatitis B
-requires HBsAg for virions
-makes Hepatitis B infection much more severe
-extremely small SS RNA genome base paired to form rod shape
-RNA possesses ribozyme activity- can self cleave RNA genome to produce mRNA for delta antigen
-delta antigen encoded by small delta genome
-virion steals HBsAg from cell infected with Hepatitis B
-Fulminant Hepatitis -80% fatal: causes encephalitis, extensive jaundice, massive hepatic necrosis
-best prevention is HBV vaccine

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Coronaviruses

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-2nd most prevalent cause of common cold (behind rhinoviruses)
-predominantly in infants and children
-antibodies provide some protection, though not complete
-enveloped icosahedrals, very long + SS RNA genome
-unusual glycoproteins permit survival in GI tract--majority of enveloped viruses do not survive GI tract
-infections remain localized to upper respiratory tract epithelia--since virus grows optimally at 33’C to 35’C
-SARS (Severe Acute Respiratory Syndrome) a coronavirus: atypical pneumonia with high fever mortality approximately 10%, most likely transmitted by respiratory droplets

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Paramyxoviruses

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-enveloped helical nucleocapsid, SS negative strand RNA genome
-non-segmented genome (differs from orthomyxoviruses-segmented)
-cytopathic viruses, induce syncytia formation (multinucleated giant cells)
-transmitted by respiratory droplets, initiate infection in respiratory tract
-cell mediated immunity essential for control of infection
-cell mediated immunity causes many of the symptoms (rash of measles)
-members differ in glycoproteins existing as spikes on envelope
-hemagglutinin -important for attachment to host cell
-named for ability to hemagglutinate RBC’s
-neuraminidase -breaks down sialic acid of host, prevents clumping of viruses
-Measles, mumps, parainfluenza, RSV.
-There is a measles, mumps, rubella vaccine: composed of live attenuated vaccines. given as early as 15-24 months. 95% lifelong immunization with single dose. measles a great candidate for eradication since only infects humans, only one serotype, not many asymptomatic carriers yet transport of attenuated vaccine requires refrigeration

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Measles

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-A paramyxovirus.
-Enveloped, helical capsid, ssRNA
-non segmented genome--differs from orthomyxoviruses
-Measles-has hemagglutin
-spread by respiratory droplets to respiratory tract
-highly contagious, 95% vaccination rate required for herd immunity
-prodromal period of measles -not specific enough for diagnosis; often conjunctivitis, cough and a head cold & photophobia
-caused by spread of virus through lymphatic system & bloodstream
-specific symptoms-present as Koplik’s spots--small, irregular, grayish-white lesions on the upper buccal mucosa. a rapid increase in temperature also observed
-caused by T cells reacting against measles targeted endothelial cells lining the bloodstream
-can be fatal in immunocompromised or malnourished people
-Proper resolution of measles gives lifelong immunity
-encephalitis, pneumonia or death rare adverse outcomes
-giant cell pneumonia without rash-caused by lack of cellular immunity

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Parainfluenza

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-Paramyxovirus
-ssRNA, neg strand, enveloped, helical nucleocapsid. Non segmented genomes.
-Parainfluenza-has both hemagglutin & neuraminidase
-causes coldlike symptoms & serious respiratory tract disease
-cause pneumonia and croup in children
-croup = acute laryngotracheobronchitis
-causes symptoms similar to common cold in adults
-transmitted by respiratory droplets & direct contact
-surface spikes consist of hemagglutinin & neuraminidase and fusion proteins
-there is neither antiviral therapy nor a vaccine available, natural immunity does not appear to be lifelong

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Mumps

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-A paramyxovirus
-ssRNA, neg strand, naked helical capsid, non-segmented genome
-Mumps-has both hemagglutin & neuraminidase
-transmitted via respiratory droplets
-occurs worldwide, incidence highest in winter
-painful swelling of parotid glands, usually self-limiting and benign usually resolves within a week
-causes pain while eating, headache, general malaise
-complications; deafness in children, orchitis- painful swelling of testicles, usually in postpubertal males, can result in sterility
-attenuated vaccine has been effective at reducing incidence
-Pathogenesis of the Mumps virus: begins with infection of respiratory tract. viremia results in infection of parotid glands. parotitis- painful swelling of salivary glands. T-cells important for eliminating, immunity is life long

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RSV(Respiratory Synctial Virus)

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-RSV(Respiratory Synctial Virus)-has neither protein activity
-predominant cause of pneumonia and bronchiolitis in infants
-narrow bronchioles of infants more readily obstructed by virus induced necrotic “plugs” of mucus
-transmission by respiratory droplets & direct contact of contaminated hands with the nose or the mouth
-usually occurs in winter, very contagious
-only paramyxovirus member lacking both of the glycoproteins hemagglutinin & neuraminidase
-surface spikes are fusion proteins (NOT HA or neuraminidase)
-Ribavirin- guanosine analog used for severely hospitalized infants--passive immunization with anti-RSV IgG also used
-there is no vaccine

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Influenza viruses- types A, B, C

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-The only members of Orthomyxovirus family
-segmented, SS negative stranded RNA genome
-enveloped helical nucleocapsid, A, B or C type determined by
nucleocapsid present
-more resistant to drying than most enveloped viruses. can remain on doorknobs etc. for almost a day and be infectious
-influenza A responsible for global pandemics--because usually the one that can infect animals and mutate.
-flu symptoms: fever, runny nose, cough, headache, malaise, muscle ache
-hemagglutinin- viral attachment protein, promotes fusion
-neuraminidase- cleaves sialic acid, prevents clumping promotes release of budding virus from cell
-Diseases associated with influenza : secondary bacterial superinfection caused by lung damage often S. pneumoniae, H. influenzae, S. aureus

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Influenza A

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-Orthomyxovirus family (along with B and C)
-Segmented, ssRNA, - stranded.
-The one responsible for pandemics.
-Life cycle of Influenza A virus: 1. packaging of RNA segments into virion will be somewhat random
2. if 2 different A strains infect same strain, can be antigenic shift
3. a Zoonosis disease ability to infect birds, pigs other animals increases probability of eventual antigenic shift
-Antigenic drift vs. Antigenic shift: Antigenic drift is a mutation in particular gene. Antigenic shift is a major change based on reassortment of genome pieces
-segmented genome permits opportunity to undergo antigenic shift
-Influenza A strain can be classified by hemagglutinin & neuraminidase, avian flu strain is H5N1
-Prevention against influenza: amantadine (symmetrel) inhibits replication of Influenza A virus interferes with viral attachment and uncoating. beneficial to give to high-risk subjects during an epidemic
-vaccine -main mode of prevention and consists of killed virus. killed A and B influenza viruses, yet is an educated guess at which types of influenza will predominate the next year. live vaccine now available as nasal spray

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Reye's Syndrome

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-brain damage and liver damage occurs in children;
-Influenza B + aspirin
-encephalopathy occurs in brain
-most often seen in children between 4-12, peak incidence at 6
-illness has rapid onset and symptoms vary greatly can induce delirium , combative behavior and coma
-typically follows an upper respiratory infection or chickenpox by about one week
-vomiting rapidly followed by irritable & combative behavior
-seizures and coma can develop, quickly leading to death

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Prions

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-infectious amyloid proteins that cause TSE’s (proteinaceous infectious particle that lacks nucleic acid)
-originally classified as “slow viruses” since take a long time to show up
-cerebral disorders-neurons develop large vacuoles -“spongelike” appearance,
-1st example of disease that does not involve nucleic acid (viruses have nucleic acid)
-Transmissible spongiform encephalopathies caused by prions: 1. scrapie → in sheep 2. bovine spongiform encephalopathy (BSE or mad cow disease) → in humans and cattle. 3. kuru (“trembling”) → cannabilistic tribes of New Guinea
4. Creutzfeldt-Jakob disease → usually occurs in middle age (40-50’s)
-PrP (Prion Protein)-responsible for human TSE’s mad cow, BSE, CJD, kuru. A membrane-anchored cell-surface receptor in neurons. Evolutionary conserved throughout vertebrates
-Genetic knockout hamsters for PrP gene resistant to developing scrapie when injected with the infectious agent (WT hamsters would die).
-PrPSc catalyzes conversion of WT PrP (PrPC) to scrapie form PrPSc--a self-perpetuating process
-PrPC-mostly α-helices
-PrPSc-mostly β-pleated sheets

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The fungi

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-2 types; yeasts and molds
-are eukaryotic cells
-have cell wall
-dimorphic; can exist in 2 separate morphological forms--conversion can be regulated by temperature
-Yeast form when in body (37 C)
-have both asexual and sexual reproduction capabilities
-most are obligate aerobes, some are facultative aerobes
-none are obligate anaerobes
-Sabouraud’s agar -selective media for fungi, bacteria can’t grow--contains high concentrations of glucose, higher concentrations than most bacteria like. Also contains antibiotics such as choramphenicol & cycloheximide to inhibit the growth of bacteria
-use of selective media for growing fungi important since bacteria grow so much faster than eukaryotic cells