Antivirals, interferon and vaccines lect copy

ANTIVIRALS, ANTIVIRALS, INTERFERON AND INTERFERON AND

VACCINESVACCINES

EDWARD-BENGIE L. MAGSOMBOL, MD, EDWARD-BENGIE L. MAGSOMBOL, MD, FPCP, FPCC, DASNCFPCP, FPCC, DASNC

Assistant Professor in MicrobiologyAssistant Professor in MicrobiologyFatima College of MedicineFatima College of Medicine

The Viral

Replication Cycle:

Several Important Targets

for Antiviral Therapy

4 Ways to Combat Viruses:4 Ways to Combat Viruses:

1.1. Immune SystemImmune System

2.2. Antiviral therapyAntiviral therapy

3.3. Interferon therapyInterferon therapy

4.4. VaccinesVaccines

Viruses treatable with Viruses treatable with antiviralsantivirals

HSVHSVVZVVZVCMVCMVHIVHIV Influenza AInfluenza ARSVRSVHepatitis A, B and C virusesHepatitis A, B and C virusesPapillomavirusPapillomavirusPicornavirusPicornavirus

AntiviralsAntiviralsAPPROACH TO ANTIVIRAL CHEMOTHERAPYAPPROACH TO ANTIVIRAL CHEMOTHERAPY1. Adsorption, Penetration and Uncoating1. Adsorption, Penetration and Uncoating = little is known about the specific = little is known about the specific

reactions involvedreactions involved = only amantadine, rimantadine used vs = only amantadine, rimantadine used vs

influenza Ainfluenza A = HIV, rhino, EBV now being researched on= HIV, rhino, EBV now being researched on

2. Replication of Viral Nucleic Acids2. Replication of Viral Nucleic Acids = attack enzymes which catalyze replication= attack enzymes which catalyze replication = not present in uninfected cells= not present in uninfected cells = all RNA viruses, pox, herpes and = all RNA viruses, pox, herpes and adenovirusadenovirus

AntiviralsAntiviralsAPPROACH TO ANTIVIRAL APPROACH TO ANTIVIRAL

CHEMOTHERAPYCHEMOTHERAPY

3.3. Integration of Viral Genomes into Cellular Integration of Viral Genomes into Cellular GenomesGenomes

= as part of multiplication cycle = as part of multiplication cycle (retrovirus and its integrase)(retrovirus and its integrase)

= tumorigenesis (papovavirus, herpes)= tumorigenesis (papovavirus, herpes)

4. Synthesis of Viral Messenger RNA’s4. Synthesis of Viral Messenger RNA’s = virus-encoded RNA polymerases, = virus-encoded RNA polymerases,

capping enzymescapping enzymes

AntiviralsAntivirals

APPROACH TO ANTIVIRAL APPROACH TO ANTIVIRAL CHEMOTHERAPYCHEMOTHERAPY

5. Synthesis of Viral Proteins5. Synthesis of Viral Proteins

= viral mRNA translation different from = viral mRNA translation different from host mRNAhost mRNA

6. Viral Morphogenesis6. Viral Morphogenesis

= enzymes which cleave precursors for = enzymes which cleave precursors for viral capsid CHONsviral capsid CHONs

= ex. viral proteases= ex. viral proteases

AntiviralsAntiviralsCLASSES OF ANTIVIRAL AGENTSCLASSES OF ANTIVIRAL AGENTS Synthetic Antiviral AgentsSynthetic Antiviral AgentsI. Analogues of Ribonucleosides and I. Analogues of Ribonucleosides and

DeoxyribonucleosidesDeoxyribonucleosides = nucleic acids base or derivatives= nucleic acids base or derivatives = included into nucleic acid, usually DNA= included into nucleic acid, usually DNA = interfere with nucleic acid function= interfere with nucleic acid function = selectively inhibit viral polymerases= selectively inhibit viral polymerases A. A. Idoxuridine and TrifluorothymidineIdoxuridine and Trifluorothymidine = analogues of thymidine, inhibits viral DNA = analogues of thymidine, inhibits viral DNA

formationformation = inhibit multiplication of herpesviruses= inhibit multiplication of herpesviruses = used for topical treatment of herpes simplex = used for topical treatment of herpes simplex keratitiskeratitis = not for systemic use because of toxicity= not for systemic use because of toxicity

Herpes keratoconjunctivitisHerpes keratoconjunctivitis

Herpes simplexHerpes simplex

AntiviralsAntiviralsB. Vidarabine (Adenosine arabinoside, Ara-B. Vidarabine (Adenosine arabinoside, Ara-

A)A) = inhibits HSV and VZV multiplication= inhibits HSV and VZV multiplication = act as chain terminators; inhibit viral DNA = act as chain terminators; inhibit viral DNA

polymerase more than host DNA polymerasepolymerase more than host DNA polymerase = herpes simplex keratitis; herpes simplex = herpes simplex keratitis; herpes simplex

encephalitis (IV route)encephalitis (IV route)C. Acyclovir, FamciclovirC. Acyclovir, Famciclovir

= guanine linked to an open ring analogue of = guanine linked to an open ring analogue of ribose, deoxyriboseribose, deoxyribose

= thymine or cytosine derivative= thymine or cytosine derivative = phosphorylated by HSV and VZV TKinases= phosphorylated by HSV and VZV TKinases = topical or IV in mucocutaneous herpes simplex = topical or IV in mucocutaneous herpes simplex

in immunocompromised hosts and also in in immunocompromised hosts and also in genital genital

herpes simplex infectionsherpes simplex infections

CHICKENPOX (VARICELLA)CHICKENPOX (VARICELLA)

AntiviralsAntiviralsD. GanciclovirD. Ganciclovir= = close relative of acyclovir; inhibits close relative of acyclovir; inhibits

HSV multiplicationHSV multiplication = better substrate for HSV TK than = better substrate for HSV TK than

acycloviracyclovir = best inhibitor of CMV multiplication in = best inhibitor of CMV multiplication in

useuse = probably not a strict chain terminator = probably not a strict chain terminator

unlike acyclovirunlike acyclovir

AntiviralsAntiviralsE. Zidovudine (Azidothymidine, AZT, E. Zidovudine (Azidothymidine, AZT,

RetrovirRetrovir))= inhibits retrovirus reverse transcriptase (RT)= inhibits retrovirus reverse transcriptase (RT)= chain terminator because it does not possess a = chain terminator because it does not possess a

3’-OH group3’-OH group= demonstrated clinical efficacy in HIV = demonstrated clinical efficacy in HIV = others: zalcitabine, didanosine, stavudine, = others: zalcitabine, didanosine, stavudine,

lamivudinelamivudine nevirapine nevirapine = lamivudine: newer generation RT inhibitor = lamivudine: newer generation RT inhibitor

effective vs hepatitis Beffective vs hepatitis B= new antivirals that don’t look like nucleosides = new antivirals that don’t look like nucleosides

but still block RTbut still block RT

CYTOMEGALOVIRUSCYTOMEGALOVIRUS

AIDSAIDS

AntiviralsAntiviralsF. Ribavirin (Virazole)F. Ribavirin (Virazole)= = analogue of purine precursor of 5-analogue of purine precursor of 5-

aminoimidazole 4-carboxamideaminoimidazole 4-carboxamide

= wide spectrum: good vs RNA and DNA viruses= wide spectrum: good vs RNA and DNA viruses

= target: virus-encoded nucleic acid = target: virus-encoded nucleic acid polymerasespolymerases

= affects elongation and initiation (less extent)= affects elongation and initiation (less extent)

= for severe RSV infection (aerosol) in children= for severe RSV infection (aerosol) in children

= reduce mortality on patients with Lassa fever= reduce mortality on patients with Lassa fever

RSV RSV infectioninfection

(bronchiolitis(bronchiolitis

))

RESPIRATORY SYNCYTIAL RESPIRATORY SYNCYTIAL VIRUS VIRUS


OthersOthers= analogues of thymidine = analogues of thymidine (BVdU)(BVdU) and and

cytosine cytosine (FIAC)(FIAC) - good vs herpesvirus - good vs herpesvirus DNA polymerases with low toxicityDNA polymerases with low toxicity

= 2’, 3’-dideoxynucleosides act as chain = 2’, 3’-dideoxynucleosides act as chain terminators in retrovirus infections terminators in retrovirus infections including HIVincluding HIV

= phosphonoformic acid = phosphonoformic acid (foscarnet)(foscarnet) and and phosphonoacetic acid phosphonoacetic acid (PAA)(PAA) – potent – potent highly specific inhibitors of HSV DNA.highly specific inhibitors of HSV DNA.

= toxic to bones and kidney= toxic to bones and kidney


OthersOthers

methyl phosphonate derivative (s)-methyl phosphonate derivative (s)-HPMPA HPMPA

= inhibits DNA viruses ex. herpes, = inhibits DNA viruses ex. herpes, pox, adeno and retropox, adeno and retro

PMEAPMEA- for retrovirus, HIV and tumor - for retrovirus, HIV and tumor formationformation

AntiviralsAntiviralsAmantadine and RimantadineAmantadine and Rimantadine= = effective inhibitors of influenza A effective inhibitors of influenza A

multiplication; bind to and block H channelmultiplication; bind to and block H channel and prevent M1 proteins from dissociatingand prevent M1 proteins from dissociating from nucleocapsidfrom nucleocapsid= affects penetration and uncoating= affects penetration and uncoating= also inhibits budding and virus particle = also inhibits budding and virus particle

releaserelease= FDA approved for prophylaxis vs influenza A= FDA approved for prophylaxis vs influenza A= CNS side effects worse for amantadine than = CNS side effects worse for amantadine than

rimantadinerimantadine= useful for elderly, immunocompromised, = useful for elderly, immunocompromised,

allergies and in epidemicsallergies and in epidemics


Pleconaril= inhibits uncoating of Pleconaril= inhibits uncoating of rhinovirus by blocking a pocket on rhinovirus by blocking a pocket on the viral surface which controls the the viral surface which controls the uncoating processuncoating process

Same pocket is found among Same pocket is found among enterovirusesenteroviruses


Other Antiviral AgentsOther Antiviral Agents Isatin-B-thiosemicarbazoneIsatin-B-thiosemicarbazone= very potent inhibitor of Poxvirus= very potent inhibitor of Poxvirus

= at 3 mg/L – inhibits vaccinia multiplication = at 3 mg/L – inhibits vaccinia multiplication (90%)(90%)

= inhibits translation of late mRNA –> no viral = inhibits translation of late mRNA –> no viral capsid and CHON synthesis -> no progenycapsid and CHON synthesis -> no progeny

Marburan (n-methyl-IBT)Marburan (n-methyl-IBT) – a derivative of – a derivative of IBTIBT

= beneficial effects for smallpox contacts= beneficial effects for smallpox contacts

SMALLPOXSMALLPOX


2-2-HydroxylbenzylbenzimidazoHydroxylbenzylbenzimidazole (HBB) and Guanidinele (HBB) and Guanidine

= PICORNAVIRUSES (polio, echo, = PICORNAVIRUSES (polio, echo, coxsackie and coxsackie and FMD/enteroviruses)FMD/enteroviruses)

= interfere with replication of = interfere with replication of viral RNAviral RNA

= prevent the initiation of the = prevent the initiation of the synthesis of progeny (+) synthesis of progeny (+) strands by inhibiting protein 2Cstrands by inhibiting protein 2C

AntiviralsAntiviralsRifampicin and Rifamycin derivativesRifampicin and Rifamycin derivatives= = binds to bacterial RNA polymerasebinds to bacterial RNA polymerase

= prevent initiation of transcription= prevent initiation of transcription

= no binding to animal RNA polymerase= no binding to animal RNA polymerase

= inhibit multiplication of pox and adeno = inhibit multiplication of pox and adeno

= both early and late mRNAs are transcribed = both early and late mRNAs are transcribed

normally (viral polymerase not inhibited)normally (viral polymerase not inhibited)

= accumulation of immature virus particles = accumulation of immature virus particles that lack the normal dense spicule layer that lack the normal dense spicule layer


Arildone, Rhodanine, and Arildone, Rhodanine, and WIN 51711WIN 51711

= inhibit uncoating of = inhibit uncoating of Picornaviruses by making the Picornaviruses by making the virus more stable virus more stable

= does not affect absorption or = does not affect absorption or penetrationpenetration


Translation: AntisenseTranslation: Antisense= segments of DNA or RNA that = segments of DNA or RNA that

act as mirror images to critical act as mirror images to critical sections of viral genomessections of viral genomes

= fomivirsen: for CMV eye = fomivirsen: for CMV eye infections in AIDS patientsinfections in AIDS patients

= morpholino antisense: = morpholino antisense: experimentally suppress the ff:experimentally suppress the ff:

calicivirus, flavivirus, dengue, calicivirus, flavivirus, dengue, HCV, coronavirusesHCV, coronaviruses


Translation: RibozymesTranslation: Ribozymes= enzymes that cut apart viral DNA or RNA= enzymes that cut apart viral DNA or RNA

= ongoing work on Hepa C and HIV= ongoing work on Hepa C and HIV

AntiviralsAntiviralsInhibitors of ProteasesInhibitors of Proteases= precursors do not become the = precursors do not become the

functional functional

proteins; synthetic peptidesproteins; synthetic peptides

= (-) = (-) HIV protease:HIV protease: essential role in essential role in production of a functional virionproduction of a functional virion

= Saquinavir, indinavir, ritonavir, = Saquinavir, indinavir, ritonavir, nelfinavir, amprenavir – slip into the nelfinavir, amprenavir – slip into the hydrophobic active site of the hydrophobic active site of the enzymeenzyme

= combine with AZT and a 2= combine with AZT and a 2ndnd nucleoside analogue in tx of AIDSnucleoside analogue in tx of AIDS

AntiviralsAntiviralsInhibitors of Viral releaseInhibitors of Viral release= final stage is the release of the = final stage is the release of the

completed virus from the host cellcompleted virus from the host cell

= zanamivir (Relenza) and oseltamivir = zanamivir (Relenza) and oseltamivir (Tamiflu) block neuraminidase in the (Tamiflu) block neuraminidase in the surface of influenza virussurface of influenza virus

AntiviralsAntiviralsPromising New ApproachesPromising New Approaches Inhibition of AdsorptionInhibition of Adsorption

= many viral receptors have been = many viral receptors have been identifiedidentified

Targeted Introduction of Toxins into Targeted Introduction of Toxins into Infected CellsInfected Cells

= directed against infected cells= directed against infected cells

= ricin or the Pseudomonas exotoxin = ricin or the Pseudomonas exotoxin to CD4--- attach to gp120 --- to CD4--- attach to gp120 --- internalized into infected cellinternalized into infected cell


Introduction into Cells of Specific Introduction into Cells of Specific Anti-Sense RNA SequencesAnti-Sense RNA Sequences

= = many mRNA splice junctions have many mRNA splice junctions have been sequencedbeen sequenced

Preventing Interactions Among Preventing Interactions Among Protein MoleculesProtein Molecules

= = add excess oligopeptides with the add excess oligopeptides with the same sequence as that of the same sequence as that of the interacting sequenceinteracting sequence

InterferonsInterferons natural antiviral compoundsnatural antiviral compounds substances that have antiviral properties substances that have antiviral properties

in adjacent, noninfected cellsin adjacent, noninfected cells

Types of InterferonsTypes of Interferons

Type I:Type I: (1) Interferon alpha (1) Interferon alpha = maximal = maximal

antiviral activityantiviral activity

(2) Interferon Beta(2) Interferon Beta = intermediate = intermediate

antiviral activityantiviral activity

Type II:Type II: Interferon GammaInterferon Gamma = more = more lymphokine than antivirallymphokine than antiviral

InterferonsInterferonsRegulation of Interferon Regulation of Interferon

ExpressionExpression= not expressed in a normal resting = not expressed in a normal resting

cellcell

= labile repressors bind to = labile repressors bind to promoter elements, block promoter elements, block transcriptiontranscription

= production of labile suppressors = production of labile suppressors drop in viral infection and allows drop in viral infection and allows interferon synthesis to occurinterferon synthesis to occur

InterferonsInterferonsMechanism of actionMechanism of action= synthesis, secretion, diffusion and binding = synthesis, secretion, diffusion and binding

to cellular receptorsto cellular receptors

= taken up by uninfected cells= taken up by uninfected cells

= viral replication (-) via cellular enzymes = viral replication (-) via cellular enzymes

Type IType I

= (-) viral protein synthesis (very specific)= (-) viral protein synthesis (very specific)

= 2 enzymes activated:= 2 enzymes activated:

1. 1. oligo-A synthetaseoligo-A synthetase adenine nucleotide adenine nucleotide viral mRNA digestion viral mRNA digestion

2. protein kinase2. protein kinase ->phosphorylates EF-2 -> ->phosphorylates EF-2 -> blocks CHON synthesisblocks CHON synthesis

= block other stages of replication including = block other stages of replication including buddingbudding

InterferonsInterferons

Type II :Type II :

= antiviral effects mediated by:= antiviral effects mediated by:

1. nitric oxide synthetase—1. nitric oxide synthetase—increased intracellular nitric increased intracellular nitric oxide levels oxide levels

2. upregulation of MHC I and II 2. upregulation of MHC I and II expressionexpression

3. activation of monocytes, 3. activation of monocytes, macrophages and NK cellsmacrophages and NK cells

InterferonInterferon

InterferonsInterferonsClinical Uses:Clinical Uses: IFN-A :IFN-A :

= treatment of viral infections: = treatment of viral infections: condylomata acuminata and chronic hepa condylomata acuminata and chronic hepa B and CB and C

= prophylactic or therapeutic agent in = prophylactic or therapeutic agent in immunocomp. hosts (VZV, HSV 1 and 2)immunocomp. hosts (VZV, HSV 1 and 2)

= prophylaxis vs CMV in renal transplant= prophylaxis vs CMV in renal transplant

= treatment of AIDS-associated Kaposi’s = treatment of AIDS-associated Kaposi’s sarcoma and hairy cell leukemiasarcoma and hairy cell leukemia

IFN-G:IFN-G: immunostimulant in oncologic and immunostimulant in oncologic and immunedeficiency disordersimmunedeficiency disorders

Sites for Sites for effective effective action of action of various various AntiviralsAntivirals

versus versus VirusesViruses

VaccinesVaccines

TYPES OF VACCINES:TYPES OF VACCINES: 1. Inactivated Virus Vaccines1. Inactivated Virus Vaccines = complete inactivation of = complete inactivation of

infectivity with minimum loss of infectivity with minimum loss of antigenicityantigenicity

= ex. a. UV irradiation= ex. a. UV irradiation b. photodynamic inactivation b. photodynamic inactivation and white light and white light

irradiationirradiation c. beta-propiolactonec. beta-propiolactone d. formaldehyde (most d. formaldehyde (most

effective)effective)

VaccinesVaccines

2.2. Attenuated Active Virus VaccinesAttenuated Active Virus Vaccines = Jenner’s smallpox , Theiler’s yellow fever = Jenner’s smallpox , Theiler’s yellow fever

virus, Sabin poliovirus, MMR, adenovirusvirus, Sabin poliovirus, MMR, adenovirus

= repeated passage of human pathogens in = repeated passage of human pathogens in

other host speciesother host species

= effective in small amounts: amplification = effective in small amounts: amplification

effect effect

= recombinant DNA technology has = recombinant DNA technology has

improved attenuationimproved attenuation

POLIO VACCINEPOLIO VACCINE

MEASLESMEASLES

VaccinesVaccines

3. Subunit Vaccines3. Subunit Vaccines

= viral proteins that elicit = viral proteins that elicit formation formation

of neutralizing Ab’sof neutralizing Ab’s

= smaller range of Ab’s (IgA, IgM) = smaller range of Ab’s (IgA, IgM)

producedproduced

= genes of these CHONs now can = genes of these CHONs now can be be

clonedcloned

VaccinesVaccines4. Viral Vectors4. Viral Vectors = genes of viral CHONs inserted into = genes of viral CHONs inserted into

avirulent avirulent

viral vectorsviral vectors

= thymidine kinase gene of Vaccinia virus = thymidine kinase gene of Vaccinia virus

= genes are expressed without disease and = genes are expressed without disease and

Ab’s are producedAb’s are produced

= HA gene of influenza, glycoprotein B gene = HA gene of influenza, glycoprotein B gene

of herpesvirus, surface Ag of HBVof herpesvirus, surface Ag of HBV

= major limitation is the infectivity of = major limitation is the infectivity of

vaccinia itselfvaccinia itself

THANK THANK YOUYOU

Antivirals, interferon and vaccines lect copy

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