Respiratory viruses

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:

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

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

Virion spherical/ovoid, 80-120nm diameter, The inner side of the envelope is lined by the matrix protein, stable type-specific.

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).

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

Neuraminadase (NA) Encoded by RNA segment #6 Enzyme that uses neuraminic (sialic) acid as a substrate Important in releasing mature virus from cells

ORTHOMYXOVIRUSES type A, B, C : NP, M1 protein HA - hemagglutinin NA - neuraminidase helical nucleocapsid (RNA plus NP protein) lipid bilayer membrane polymerase complex M1 protein type A, B, C : NP, M1 protein sub-types: HA or NA protein

Influenza virus A

Replication Influenza transcribe and replicates its genome in the target cell nucleus assemble and buds from the plasma membrane

Influenza virus

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.

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 IH Group C - This group does not cause epidemics and causes mild disease

severity of illness animal reservoir human pandemics human epidemics antigenic changes segmented genome amantadine, rimantidine zanamivir surface glycoproteins TYPE A ++++ yes shift, drift sensitive 2 TYPE B ++ no yes drift no effect sensitive 2 TYPE C + no no (sporadic) drift yes no effect (1)

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

Variation and Epidemiology  Antigenic drift: median or small epidemic. Antigenic shift:large scale epidemic.

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

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

Epidemic

where do “new” HA and NA come from? 13 types HA 9 types NA all circulate in birds pigs avian and human

where do “new” HA and NA come from?

why do we not have influenza B pandemics? so far no shifts have been recorded no animal reservoir known

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

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

Transmission Source of infection: patients and carriers. AEROSOL 100,000 TO 1,000,000 VIRIONS PER DROPLET 18-72 HR INCUBATION

Aerosol Inoculation Of virus

NORMAL TRACHEAL MUCOSA 3 DAYS POST-INFECTION 7 DAYS POST-INFECTION

SYMPTOMS FEVER HEADACHE MYALGIA(肌痛) COUGH RHINITIS(鼻炎) OCULAR SYMPTOMS

PULMONARY COMPLICATIONS CROUP (YOUNG CHILDREN) PRIMARY INFLUENZA VIRUS PNEUMONIA SECONDARY BACTERIAL INFECTION Streptococcus pneumoniae Staphlyococcus aureus Hemophilus influenzae

NON-PULMONARY COMPLICATIONS myositis (rare, > in children, > with type B) cardiac complications liver and CNS Reye’s syndrome peripheral nervous system

Immunity

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

Serology hemagglutination inhibition Hemadsorption inhibition ELISA immunofluoresence complement fixation. NT.

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.

Types of Vaccine Killed Whole Virus Rather pyrogenic, not used today. Live Virus Attenuated strains were widely used in Russia but not elsewhere. Virus Subunit HA 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 ] Synthetic Much research is being done to try and find a neutralising epitope that is more stable, and can therefore be used for a universal vaccine.

CDC

Attenuated Donor Master Strain PB2 PB1 PA HA NA NP M NS Attenuated Donor Master Strain New Virulent Antigenic Variant Strain X Attenuated Vaccine Strain: Coat of Virulent strain with Virulence Characteristics of Attenuated Strain

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

PREVENTION - DRUGS RIMANTADINE金刚乙胺 (M2) AMANTADINE金刚烷胺 (M2) type A only AMANTADINE金刚烷胺 (M2) ZANAMIVIR (NA) types A and B, not yet approved for prevention but studies show effective OSELTAMIVIR (NA) types A and B

TREATMENT - DRUGS RIMANTADINE (M2) AMANTADINE (M2) ZANAMIVIR (NA) type A only, needs to be given early AMANTADINE (M2) ZANAMIVIR (NA) types A and B, needs to be given early OSELTAMIVIR (NA)

OTHER TREATMENT REST, LIQUIDS, ANTI-FEBRILE AGENTS (NO ASPIRIN FOR AGES 6MTHS-18YRS) BE AWARE OF COMPLICATIONS AND TREAT APPROPRIATELY

Paramyxoviridae

Paramyxoviridae Genus Human pathogen Morbillivirus Measles virus Paramyxovirus Parainfluenza viruses, Mumps virus Pneumovirus Respirtory syncytical virus

Virion 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

PARAMYXOVIRUSES pleomorphic HN/H/G glycoprotein SPIKES F glycoprotein helical nucleocapsid (RNA plus NP protein) lipid bilayer membrane polymerase complex M protein

PARAMYXOVIRUS FAMILY properties of attachment protein GENUS GLYCOPROTEINS TYPICAL MEMBERS Paramyxovirus genus HN, F HPIV1, HPIV3 Rubulavirus Genus HPIV2, HPIV4 mumps virus Morbillivirus genus H, F measles virus Pneumovirus genus G, F respiratory syncytial virus

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

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

Measles virus （麻疹病毒）

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.

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.

viremia

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

MEASLES - Koplik’s spots Murray et al. Medical Microbiology

Koplik's spots

MEASLES - RASH CDC - B.Rice Murray et al. Medical Microbiology

DISEASE FEVER RESPIRATORY TRACT SYMPTOMS KOPLIK’S SPOTS rhinorrhea, cough KOPLIK’S SPOTS MACULOPAPULAR RASH T-cells ->endothelial cells CONJUNCTIVITIS epithelial cells

MEASLES GIANT CELL PNEUMONIA Murray et al. Medical Microbiology

Mims et al., Medical Microbiology 1993

MEASLES ENCEPHALITIS 1/1000 cases sequelae deafness seizures mental disorders

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

Treatment No

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!

Mumps virus （腮腺炎病毒）

Mumps virus Droplets spread the infection via saliva and secretions from the respiratory tract. Incubation period of 2-3 weeks

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.

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.

MUMPS CDC - B.Rice

Mims et al., Medical Microbiology 1993

Mims et al., Medical Microbiology 1993

Parainfluenza virus （副流感病毒）

Important Characteristics Typing: Four types (1-4) : distinguished antigenically, by cytopathic effect, and pathogenically Hemeagglutinin and fusion F protein is found in the envelope

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.

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

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)

Prevention No, vaccines is not available

Respiratory syncytial virus （呼吸道合胞病毒）

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.

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

Lab Diagnosis DFA Cell culture of nasopharyngeal specimen A rise in antibody titre using ELISA

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

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.

Adenoviruses （腺病毒）

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.

Adenovirus

Important Characteristics

Replication

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

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.

swimming pool conjunctivitis

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.

Treatment No

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

Rubella Virus （风疹病毒）

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)

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

Pathogenesis Virus 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 Congenital infection

EFFECTS ON FETUS HEARING LOSS CONGENITAL HEART DEFECTS NEUROLOGICAL PYSCHOMOTOR AND/OR MENTAL RETARDATION OPHTHALMIC CATARACT, GLAUCOMA, RETINOPATHY

EFFECTS ON FETUS thrombocytopenia hepatomegaly splenomegaly intrauterine growth retardation bone lesions pneumonitis

EFFECTS ON FETUS First trimester 65-85% of neonates have sequelae

EFFECTS ON FETUS 1964 1969 to present 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

CONGENITAL INFECTIONS SHED VIRUS FOR A YEAR OR MORE AFTER BIRTH nasopharynx, urine, feces

CONGENITAL INFECTIONS EYE PROBLEMS GLANDULAR COMPLICATIONS diabetes, thyroid problems deficiency growth hormone

CONGENITAL / VERY EARLY INFECTIONS PROGRESSIVE RUBELLA PANENCEPHALITIS

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.

Treatment There is no antiviral therapy available

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

Coronavirus （冠状病毒）

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

Virion structure S-Spike glycoprotein: receptor binding, cell fusion, major antigen M-Membrane glycoprotein: transmembrane - budding & envelope formation

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

Rhinovirus （鼻病毒）

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

Reovirus (呼肠孤病毒)

Important Characteristics Virion: Icosahedal, 60-80nm in diameter, double capsid shell Genome: dsRNA Envelope: none Diseases: Acute respiratory tract infection and Gastrointestinal infections