ParamyxoviridaeParamyxoviridae -All members initiate infection in RT -Parainfluenza & RSV Remain limited to respiratory epithelium - Mumps & measles become disseminated throughout the body and produce generalized disease

PARAMYXOVIRIDAE

Paramyxovirinae Pneumovirinae PARAMYXOVIRIDAE Two sub- families

The Paramyxovirinae subfamily is divided into 4 genera, 3 of which are important: 1.Genus respirovirus: which include parainfluenza viruses 1 & 3 viruses 2.Genus Rubulavirus which include parainfluenza virus 2 &4 as well as mumps virus 3.Genus morbillivirus which include the measles (rubeola) virus

The Pneumovirinae subfamily is divided into two genera: 1. Genus pneumovirus which include respiratory syncytial virus RSV 2. Genus metapneumovirus which include: human metapneumovirus

Human Metapneumovirus The human metapneumovirus which is a respiratory pathogen first described in It appears to be widespread in young adults & older persons. Human metapneumovirus is able to cause a wide range of respiratory illnesses from MILD UR TO SEVERE LRT DISEASE

The paramyxoviruses are enveloped particles, Large ( nm in diameter). The viral genome is composed of: a negative sense linear single stranded, non segmented RNA molecule. MORPHOLOGY

Structural proteins are complexed with RNA to form the nucleocapsid. The nucleocapsid is surrounded by a lipid envelope that is superimposed with spikes (glycoprotein in nature). MORPHOLOGY

These spikes differentiated into two types: - “haemagglutinin-neuraminidase” spike (HN) - “fusion” (F) spike. MORPHOLOGY

“HN” and “F” spikes are both antigenic, They are responsible for: - host cell attachment, - mediation of membrane fusion, - haemolysin activity The are key factors in infection and pathogenesis. MORPHOLOGY

Characteristics of the genera in the subfamilies of the family Paramyxoviridae PropertyParamyxovirinaePneumovirinae Respiro Rubula MorbilliPneumo metapneumo Human viruses Parainfluenza 1,3 Mumps, parainfluenza 2,4a,4b MeaslesRSV Human metapneumo virus Serotypes 1 each 12?? F Prot _______ Haemolysin NO HAEMOLYIN NO HA NO NA HA NA +2 NO NA

The activities of the surface glycoprotein F glycoprotein …. Also carries Hemolysin activity HN glycoprotein ….Hemagglutination and neuraminidase activities Hemagglutination of erythrocytes is more efficient by H glycoprotein that lacks neuraminidase activity

The difference between the orthomyxo & paramyxoviruses OrthomyxovirusesParamyxoviruses Diseases caused in humans Influenza types A, B and CParainfluenza 1-4 infections, RSV diseaes, mumps and measles genomessRNA 8 segmented, -ve sense ssRNA nonsegmented –ve sense Fusion of virus with cell EndosomePlasma membrane Transcription of viral RNA HOST CELL NUCLEUSHost cell cytoplasm Genetic reassortment frequentRare Rate of antigentic change highlow

Parainfluenza Viruses Parainfluenza viruses are ubiquitous and cause common respiratory illness of varying severity in all age groups Transmission: droplet

Parainfluenza Viruses TYPE 1,2,& 3 are particularly considered major pathogens of severe respiratory tract disease in infants & young children Type 4 does not cause severe disease even on primary infection.

Parainfluenza Viruses 1ry infections in young children usually result in Rhinitis Pharyngitis However children with primary infection caused by serotypes 1,2 or 3 may have serious illness ranging from: –Laryngeotracheobronchitis (croup/stridor) –Bronchiolitis & pneumonia mainly type 3 age < 6month

Croup : stridor Caused mainly by serotype 1 & 2 age month incubation period 2 to 6 days –subglottal sweling, which endangers the airway. –The principal differential diagnosis is epiglottitis caused by Haemophilus influenza. MOST IMPORTANT Acute laryngeo-tracheobronchitis

PARAMYXOVIRIDAE Two sub- families Paramyxovirinae Genus respirovirus: Parainfluenza 1 &3 Genus Rubulavirus Parainfluenza 2 & 4 and mumps virus Genus morbillivirus measles virus Pneumovirinae –Pneumovirus RSV Metapneumovirus metapneumovirus

Pneumovirinae 1. Genus pneumovirus which include respiratory syncytial virus RSV 2. Genus metapneumovirus which include: human metapneumovirus

Respiratory syncytial virus

RSV is a paramyxovirus that lacks: – haemagglutinin & – neuraminidase activity. The F peplomer as well lacks –haemolysin activity.

Respiratory syncytial virus RSV is transmitted via droplet infection. Viral replication occurs in the epithelial cells of the nasopharynx. Viraemia has not been detected.

Alarming!!!!!! RSV is the most important cause of LRT illness in infants and young children. It is the main cause of: –Bronhiolitis (about 50%) –Pneumonia (25%) under one year of age.

Pathogenesis of Respiratory syncytial virus Involvement of the: immune response in the pathogenesis of some RSV respiratory symptoms especially bronchiolitis has been the subject for much speculation.

Laboratory diagnosis of parainfluenza & RSV s 1. Detection of viral antigen & \ or viral nucleic acid: Antigen detection: -Clinical specimens (exfoliated nasopharyngeal cells, nasopharyngeal secretions, aspirates or washes) by: - IF or ELISA techniques - N.A detection from the same specimens could be done using PCR

Laboratory diagnosis of respiratory tract infections (parainfluenza & RSV ) 2. Isolation & identification of the virus : The virus grow readily on T.C.C. identification is by: - the C.P.E; - I.F ( to detected V.AG.) & - or PCR (to detect V.N.A.). In parainfluenza viruses: haemadsorption & haemagglutination may be used for specific identification.

Laboratory diagnosis of respiratory tract infections parainfluenza & RSV 3. Serology : Virus specific IgA are protective but disappear within few months.

Treatment of parainfluenza & RSV infection Treatment is mainly symptomatic and include neubulized cold or hot steam with careful monitoring of the upper airway. Ribavirin delivered in the form of small particle aerosal may be effective in life threatening infections.

Immunity to Parainfluenza & RSVs It is apparent that serum neutralizing antibodies are only partially protective. Reinfections are common and can occur in presence of viral antibodies but the severity of the disease is lowered.