1 Respiratory viruses. 2 Categories of Respiratory Viruses Orthomyxoviridae: Influenza virus Paramyxoviridae : Parainfluenza virus; Mumps virus; Measles;

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Respiratory viruses

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Categories of Respiratory Viruses

• Orthomyxoviridae: Influenza virus• Paramyxoviridae : Parainfluenza virus;

Mumps virus; Measles; Respiratory syneytical virus

• Togaviridae: Rubella Virus• Coronaviridae: Corona Virus; SARS virus• Adenoviridae : human Adenovirus • picornaviridae: Rhino Virus; • Reoviridae:

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Influenza virus

Orthomyxoviridae: Influenza virusInfluenza is a disease caused by Influenza virus ,a member of the

Orthomyxoviridae.

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Genome of Influenza virus

• 8 negative sense RNA nucleocapsid segments

• The 'RNP' (RNA + nucleoprotein) is in a helical form with the 3 polymerase polypeptides associated with each segment.

• The segmented genome promotes genetic diversity caused by mutation and reassortment of segments on infection with two different strains

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Virion

• spherical/ovoid, 80-120nm diameter,

• The inner side of the envelope is lined by the matrix protein, stable type-specific.

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Virion

• The outer surface of the particle consists of a lipid envelope from which project prominent glycoprotein spikes of two types, the haemagglutinin, ~135Å trimer (HA), and neuraminidase, ~60Å tetramer (NA).

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Haemagglutinin (HA)

• Encoded by RNA segment #4 • Can agglutinate red blood cells - hence the

nomenclature • Cleavage by host-cell protease is required (resulting

in HA1 and HA2) for infection to occur

• Hemagglutinin glycoprotein is the viral attachment protein and fusion protein , and it elicits neutralizing , protective antibody responses

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Neuraminadase (NA)

• Encoded by RNA segment #6 • Enzyme that uses neuraminic (sialic) acid as

a substrate • Important in releasing mature virus from cells

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ORTHOMYXOVIRUSES

M1 protein

helical nucleocapsid (RNA plus NP protein)

HA - hemagglutinin

polymerase complex

lipid bilayer membrane

NA - neuraminidase

type A, B, C : NP, M1 protein sub-types: HA or NA protein

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Influenza virus A

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Replication

• Influenza transcribe and replicates its genome in the target cell nucleus

• assemble and buds from the plasma membrane

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Influenza virus

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Antigen

• Soluble antigens: include ribonucleoprotein and M protein which are much stable in antigenicity.

• Surface antigens: include HA and NA which are much variable in antigenicity.

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Types• Influenza viruses are divided into 3 groups

determined by the ribonucleoprotein (RNP) antigen and M antigen:

• Group A - This group is the cause of epidemics and pandemics and has an avian intermediate host (IH)Group B - This group causes epidemics and has no IHGroup C - This group does not cause epidemics and causes mild disease

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TYPE A

++++

yes

yes

yes

shift, drift

yes

sensitive

sensitive

2

severity of illness

animal reservoir

human pandemics

human epidemics

antigenic changes

segmented genome

amantadine, rimantidine

zanamivir

surface glycoproteins

TYPE B

++

no

no

yes

drift

yes

no effect

sensitive

2

TYPE C

+

no

no

no (sporadic)

drift

yes

no effect

(1)

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Subtypes

• According to antigenicity of HA and NA, influenza virus is divided into subtypes such as HnNm( H1N2, et al )

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Variation and Epidemiology

 Antigenic drift: median or small epidemic.

Antigenic shift:large scale epidemic.

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Antigenic Shift Of Influenza virus

• Reassortment of genes is a common feature of Influenza A, but not B or C

• When two different "A" viruses infect the same cell, their RNA segments can become mixed during replication

• New viruses produced in this way may survive due to a selective advantage within the population

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Antigenic Drift of Influenza Virus

•Constant mutations in the RNA of influenza which lead to polypeptide mutations

•Changes are less dramatic than those induced by Shift

•If these mutations affect HA or NA they may cause localized epidemics

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Epidemic

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where do “new” HA and NA come from?

• 13 types HA• 9 types NA

– all circulate in birds

• pigs– avian and human

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where do “new” HA and NA come from?

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why do we not have influenza B pandemics?

• so far no shifts have been recorded

• no animal reservoir known

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Resistence

• The particles are relative labile ,not resistant to drying, etc.

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Pathogenesis

• Influenza is characterised by fever, myalgia, headache and pharyngitis. In addition there may be cough and in severe cases, prostration. There is usually not coryza 鼻炎(runny nose) which characterises common cold infections.

• Infection may be very mild, even asymptomatic, moderate or very severe

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Transmission

• Source of infection: patients and carriers.

• AEROSOL– 100,000 TO 1,000,000 VIRIONS

PER DROPLET

• 18-72 HR INCUBATION

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AerosolInoculationOf virus

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NORMAL TRACHEAL MUCOSA

3 DAYS POST-INFECTION 7 DAYS POST-INFECTION

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SYMPTOMS

• FEVER

• HEADACHE

• MYALGIA( 肌痛 )• COUGH

• RHINITIS( 鼻炎 )• OCULAR SYMPTOMS

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PULMONARY COMPLICATIONS

• CROUP (YOUNG CHILDREN)

• PRIMARY INFLUENZA VIRUS PNEUMONIA

• SECONDARY BACTERIAL INFECTION– Streptococcus pneumoniae– Staphlyococcus aureus– Hemophilus influenzae

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NON-PULMONARY COMPLICATIONS

• myositis (rare, > in children, > with type B)

• cardiac complications

• liver and CNS– Reye’s syndrome

• peripheral nervous system

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Immunity

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Lab Diagnosis

• Viral detection:

Respiratory secretions

( direct aspirate , gargle , nasal washings )

1. Cell culture in primary monkey kidney or madindarby canine kidney cells

2. Hemagglutination (inhibition)

Hemadsorption (inhibition)

3. IFA/ ELISA

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• Serology

hemagglutination inhibition

Hemadsorption inhibition

ELISA

immunofluoresence

complement fixation.

NT.

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Prevention

• Vaccines at best give about 70% protection. They may sometimes not be effective against the most recently evolved strains because the rate of evolution outpaces the rate at which new vaccines can be manufactured.

• This constant antigenic change down the years means that new vaccines have to be made on a regular basis.

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Types of Vaccine • Killed Whole Virus

Rather pyrogenic, not used today. • Live Virus

Attenuated strains were widely used in Russia but not elsewhere.

• Virus SubunitHA extracted from recombinant virus forms the basis of today's vaccines.For example, the WHO Recommendation for Influenza Vaccine, 1995-1996, contains two A strains and one B strain:-[A / Singapore / 6 / 86 (H1N1)+A / Johannesburg / 33 / 94 (H3N2)+B / Beijing / 84 / 93 ]

• SyntheticMuch research is being done to try and find a neutralising epitope that is more stable, and can therefore be used for a universal vaccine.

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CDC

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PB2PB1PA

HANANP

MNS

PB2PB1PA

HANANP

MNS

PB2PB1PA

HANANP

MNS

Attenuated Donor Master Strain

New Virulent Antigenic Variant Strain

X

Attenuated Vaccine Strain: Coat of Virulent strain with Virulence Characteristics of Attenuated Strain

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Treatment

• Amantadine and rimantadine are active against influenza A viruses. The action of these closely related agents is complex and incompletely understood, but they are believed to block cellular membrane ion channels, and inhibit an uncoating step and target the M2 membrane protein

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PREVENTION - DRUGS

• RIMANTADINE 金刚乙胺 (M2)• type A only

• AMANTADINE 金刚烷胺 (M2)• type A only

• ZANAMIVIR (NA)• types A and B, not yet approved for prevention but

studies show effective

• OSELTAMIVIR (NA)• types A and B

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TREATMENT - DRUGS

• RIMANTADINE (M2)• type A only, needs to be given early

• AMANTADINE (M2)• type A only, needs to be given early

• ZANAMIVIR (NA)• types A and B, needs to be given early

• OSELTAMIVIR (NA)• types A and B, needs to be given early

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OTHER TREATMENT

• REST, LIQUIDS, ANTI-FEBRILE AGENTS (NO ASPIRIN FOR AGES 6MTHS-18YRS)

• BE AWARE OF COMPLICATIONS AND TREAT APPROPRIATELY

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Paramyxoviridae

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Paramyxoviridae

• Genus Human pathogen

• Morbillivirus Measles virus

• Paramyxovirus Parainfluenza viruses,

Mumps virus

• Pneumovirus Respirtory syncytical

virus

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VirionVirion

• Large virion consists of a negative RNA genome in a helical nucleocapsid surrounded by an enevlope containing a viral attachment protein

• HN of paramyxovirus and mumps virus has hemagglutinin and neuraminidase.

• H of measles virus has hemagglutinin activity

• G of RSV lacks these activities

48M protein

helical nucleocapsid (RNA plusNP protein)

HN/H/G glycoprotein SPIKES

polymerasecomplex

lipid bilayer membrane

F glycoprotein SPIKES

PARAMYXOVIRUSESpleomorphic

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PARAMYXOVIRUS FAMILYproperties of attachment protein

GENUS GLYCOPROTEINS TYPICAL MEMBERS

Paramyxovirus

genusHN, F HPIV1, HPIV3

Rubulavirus Genus

HN, F HPIV2, HPIV4 mumps virus

Morbillivirus genus

H, F measles virus

Pneumovirus genus

G, F respiratory syncytial virus

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Replication , Pathogenesis and Immunity • Virus replicates in the cytoplasm• Virions penetrate the cell by fusion with the plasma

membrane• Viruses induce cell-cell fusion, causing

multinucleated giant cells• Paramyxoviridae are transmitted in respiratory

droplets and initiate infection in the respiratory tract• Cell-mediated immunity causes many of the

symptoms but is essential for control of the infection

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MMR vaccine

• Composition : live attenuated virus

Measles / Mumps / Rubella

• Vaccination schedule: at 15-24 months and at 4 to 6 years or before junior high school

• Efficiency: 95% lifelong immunization with a single dose

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Measles virus（麻疹病毒）

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Pathogenesis and Immunity

• Childhood infection almost universal, protection resulting from this is probably lifelong. Both man and wild monkeys are commonly infected

• In culture, produces characteristic intranuclear inclusion bodies and syncytial giant cells.

• Transmission and initial stages of disease similar to mumps, but this virus can also infect via the eye and multiply in the conjunctivae. Viraemia following primary local multiplication results in widespread distribution to many organs.

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Pathogenesis and Immunity

• After a 10-12 day incubation period• Dry cough, sore throat, conjunctivitis (virus may be

excreted during this phase!), followed a few days later by the characteristic red, maculopapular rash and Koplik's spots

• Towards the end of the disease, there is extensive, generalized virus infection in lymphoid tissues and skin.

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viremia

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DISSEMINATED SPREAD• LONGER TIME FOR

SYMPTOMS• IMMUNE RESPONSE• IF SYMPTOMS DUE

TO IMMUNE RESPONSE, USUALLY INFECTIOUS PRIOR TO SYMPTOMS

Adapted from Mims, Playfair, Roitt, Wakelin and Williams (1993) Medical Microbiology

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MEASLES - Koplik’s spots

Murray et al. Medical Microbiology

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Koplik's spots

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MEASLES - RASH

CDC - B.Rice Murray et al. Medical Microbiology

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DISEASE• FEVER• RESPIRATORY TRACT SYMPTOMS

• rhinorrhea, cough

• KOPLIK’S SPOTS• MACULOPAPULAR RASH

• T-cells ->endothelial cells

• CONJUNCTIVITIS• epithelial cells

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MEASLES GIANT CELL PNEUMONIA

Murray et al. Medical Microbiology

64Mims et al., Medical Microbiology 1993

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MEASLES ENCEPHALITIS

• 1/1000 cases

• sequelae– deafness– seizures– mental disorders

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SSPE

• sub-acute sclerosing panencephalitis– inflammatory disease– defective virus

• early infection with measles is a risk factor

• rare (7/1,000,000 cases of measles)

• decrease since vaccination program

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Treatment

• No

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Prevention

• Both live and killed vaccines exist. Vaccination with the live attenuated vaccine has been practised since the 1960's with a dramatic decline in the incidence of the disease .

• Trivalent live attenuated vaccine (MMR) usually given - all of these viruses best avoided during pregnancy!

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Mumps virus（腮腺炎病毒）

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Mumps virus

• Droplets spread the infection via saliva and secretions from the respiratory tract.

• Incubation period of 2-3 weeks

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Mumps virus• Malaise and fever is followed within a day by

painful enlargement of one or both of the parotid (salivary) glands

• A possible complication in males after puberty is orchitis - painful swelling of one or both testicles.

• Inflammation of the ovary and pancreas can also occur.

• Disease is usually self-limiting within a few days • Aseptic meningitis (usually resolving without

problems) or postexposure encephalitis (can prove fatal) are the most serious complications associated with mumps.

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Prevention and treatment

• Treatment: none (passive immunization has been used).

• Prevention: one invariant serotype therefore vaccines are viable - both formalin-inactivated and live attenuated exist, the latter now being widely used- see MMR.

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MUMPS

CDC - B.Rice

76Mims et al., Medical Microbiology 1993

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Mims et al., Medical Microbiology 1993

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Parainfluenza virus（副流感病毒）

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Important Characteristics

• Typing: Four types (1-4) : distinguished antigenically, by cytopathic effect, and pathogenically

• Hemeagglutinin and fusion F protein is found in the envelope

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Pathogenesis and Immunity

• Cause acute respiratory infections of man ranging from relatively mild influenza-like illness to bronchitis, croup (narrowing of airways which can result in respiratory distress) and pneumonia; common infection of children.

• Transmitted by aerosols.

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Lab Diagnosis

• Nasopharynx specimen is culture in a surrogate cell line in AGMK. Infected cell are detected by hemeadsorption or DFA

• DFA also can be done rapidly to identify the agent in direct specimen

• Serotypes 1-3 are comfirmed by hemeagglutination inhibition using standardized antisera

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Treatment

• No antiviral therapy is available

• Nursing the patient in a humidified atmosphere was commonly advised

• Dexamethasone 地塞米松 and budesonide布德松 have been approved ( for outpatient treatments)

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Prevention

• No, vaccines is not available

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Respiratory syncytial virus（呼吸道合胞病毒）

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Important Characteristics

• RSV is highly infectious, transmission by respiratory secretions.

• Primary multiplication occurs in epithelial cells of URT producing a mild illness. In ~50% children less than 8 months old, virus subsequently spreads into the L.R.T. causing bronchitis, pneumonia and croup.

• Has been suggested as a possible factor in cot death and asthma.

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Pathogenesis and immunity

Disorder Age

Bronchiolitis Fever, cough, dyspnea, and

pneumonia, cyanosis in children younger

or both than 1 year

Febrile rhinitis Children

and pharyngitis

Common cold Older children and adults

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Lab Diagnosis

• DFA

• Cell culture of nasopharyngeal specimen

• A rise in antibody titre using ELISA

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Treatment

• Ribavirin aerosol( 三 ( 氮 ) 唑核苷 , 病毒唑 ) is recommended for pneumonia in infants

• RSV - IGIV has been approved for infants born prematurely

• IFN

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Prevention

• Currently no effective vaccine! Also, infection does not result in lasting protection (c.f. mumps, measles) therefore repeated infections ('colds') occur throughout life - usually without serious consequences in adults.

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Adenoviruses（腺病毒）

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General Concepts

• Most Adenovirus infections involve either the respiratory or gastrointestinal tracts or the eye.Adenovirus infections are very common, most are asymptomatic. Most people have been infected with at least 1 type at age 15.

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Adenovirus

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Important Characteristics

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Replication

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Pathogenesis and Immunity

• Disease: At Risk:• Acute Respiratory Illness Military recruits, boarding schools,

• Pharyngitis Infants• Gastroenteritis Infants• Conjunctivitis All• Pneumonia Infants, military recruits• Keratoconjunctivitis All• Acute Haemorrhagic Cystitis Infants• Hepatitis Infants, liver transplant patients

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swimming pool conjunctivitis( 游泳池结膜炎 ; 红眼病 )

• Eye infections characterized by a mild conjunctivitis "swimming pool conjunctivitis" are caused by adenoviruses and have been linked to transmission in contaminated swimming pools.

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swimming pool conjunctivitis

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Lab Diagnosis

• Isolation of adenovirus can be accomplished in cell cultures derived from epithelial cells

• Immunoassays, including fluorescent antibody and enzyme-linked immunosorbent assays, PCR can be used to detect and type the virus in clinical samples and tissue cultures

• Serological assays such as CFA, HI, EIA and neutralization techniques have been used to detect specific antibodies.

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Treatment

• No

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Prevention

• Inactivated vaccines have been developed and are routinely used for military recruits in some countries

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Rubella Virus（风疹病毒）

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General Concepts

• Viruses have enveloped single stranded positive-sense RNA.

• Replication in cytoplasm and bud at plasma membrane

• Cause Rubella( german measles, 3-days measles)

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Epidemiology

• Occurrence: worldwide in prevalence( in winter and spring)

• Reservoir: Humans

• Mode of Transmission: Vertical transmission in case of CRS/ Infection in nonimmune children is usually transmitted by droplet spread or by direct contact with patients

• Who is at risk: Non-immunized children are at risk

• Incubation period: 2-3 weeks

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Pathogenesis Rubella enters and infects the

nasopharynx and lung and then spreads to the lymph nodes and reticuloendothelial system. The resulting viremia spreads the virus to other tissues and the skin. Circulating antibody can block the transfer of virus at the indicated points. In an immunologically deficient pregnant woman, the virus can infect the placenta and spread to the fetus

Virus

Congenital infection

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EFFECTS ON FETUS

• HEARING LOSS

• CONGENITAL HEART DEFECTS

• NEUROLOGICAL– PYSCHOMOTOR AND/OR MENTAL

RETARDATION

• OPHTHALMIC– CATARACT, GLAUCOMA, RETINOPATHY

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EFFECTS ON FETUS

• thrombocytopenia

• hepatomegaly

• splenomegaly

• intrauterine growth retardation

• bone lesions

• pneumonitis

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EFFECTS ON FETUS

• First trimester– 65-85% of neonates have sequelae

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EFFECTS ON FETUS

• 1964– 20,000 infants with permanent problems– 6,000 to 30,000 spontaneous abortions– 5,000 therapeutic abortions

• 1969 to present– maximum of 67 cases congential rubella/yr

• usually fewer than 10

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CONGENITAL INFECTIONS

• SHED VIRUS FOR A YEAR OR MORE AFTER BIRTH– nasopharynx, urine, feces

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CONGENITAL INFECTIONS

• EYE PROBLEMS

• GLANDULAR COMPLICATIONS– diabetes, – thyroid problems– deficiency growth hormone

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CONGENITAL / VERY EARLY INFECTIONS

• PROGRESSIVE RUBELLA PANENCEPHALITIS

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Lab Diagnosis

• Current rubella infection, in pregnant women can be confirmed by 4-fold rise in specific antibody titer between acute and convalescent-phase serum specimens by ELISA

• The Dx of CRS in the newborn may be confirmed by the presence of specific IgM antibody.

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Treatment

• There is no antiviral therapy available

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Prevention

• A single dose of live, attenuated rubella vaccine elicits a significant antibody response in approximately 98%-99% of vaccinated individuals

• It should not be given to immunocompromised patients

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Coronavirus（冠状病毒）

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Important Characteristics

• Virion: Spherical, 80-160nm in diameter, helical nucleocapside

• Genome: +ssRNA, linear, nonsegmented, 27-30kb, infectious

• Proteome: two glycoproteins and one phosphoprotein. Some viruses contain a third glycoprotein (hemagglutinin esterase)

• Envelope: contains large, widely spaced, club-or petal- shaped spikes. crown-like

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Virion structure• S-Spike

glycoprotein: receptor binding, cell fusion, major antigen

• M-Membrane glycoprotein: transmembrane - budding & envelope formation

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Pathogenesis and Immunity

• These viruses infect a variety of mammals & birds. The exact number of human isolates are not known as many cannot be grown in culture.

• They cause: common colds and have been implicated in gastroenteritis in infants.

• Transmitted by aerosols of respiratory secretions

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Rhinovirus（鼻病毒）

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Important Characteristics

• Rhinoviruses are picornaviruses similar to enteroviruses but differ from them in having a buoyant density in cesium chloride of 1.40 g/ml and in being Acid-labile

• Rhinoviruses are isolated commonly from the nose and throat but very rarely from feces.

• These viruses cause upper respiratory tract infections, including the common cold

122

Reovirus( 呼肠孤病毒 )

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Important Characteristics

• Virion: Icosahedal, 60-80nm in diameter, double capsid shell

• Genome: dsRNA

• Envelope: none

• Diseases: Acute respiratory tract infection and Gastrointestinal infections