“ANTIVIRAIS E VACINAS”

Prof. Oscar Bruna Romero, Pharm., PhDLaboratorio de Agentes Recombinantes

ANTIVIRAL DRUGSViral cycle1) adsorption and penetration into cell2) uncoating of viral nucleic acid3) synthesis of regulatory proteins4) synthesis of RNA or DNA5) synthesis of structural proteins6) assembly of viral particles7) release from host cell

Sites of Drug Action

Fusion Inhibitors

Enfuvirtide. Binds to the HIV gp41 subunit of the viral envelope glycoprotein, preventing the conformational changes required for fusion of the viral and cellular membranes. By blocking fusion (entry into cell), FUZEON prevents HIV from infecting CD4 cells.

Maraviroc. Binds to CCR5 preventing interaction with gp120. Also known as “chemokine-receptor antagonist”.

Uncoating inhibitorsAmantadine and Rimantadine

Inhibit the uncoating of viral RNA therefore inhibiting replication (some viruses are resistant)

Used in the prevention and treatment of Influenza A only

Nucleic acid synthesis inhibitorsAcyclovir

• an acyclic guanosine derivative• Phosphorylated by viral thymidine kinase• Di-and tri-phosphorylated by host cellular

enzymes• Inhibits viral DNA synthesis by:

– 1) competing with dGTP for viral DNA polymerase

– 2) chain termination

Mechanism of ResistanceAcyclovir

• Alteration in viral thymidine kinase

• Alteration in viral DNA polymerase

• Cross-resistance with valacyclovir, famciclovir, and ganciclovir

Antiretroviral Agents

1) Fusion inhibitors2) Reverse Transcriptase Inhibitors

NucleosideNonnucleoside

3) Protease inhibitors

Combinational therapies (I)Synthesis and assembly inhibitors

NucleosideReverse Transcriptase Inhibitors

• Zidovudine (AZT)• Didanosine • Lamivudine • Zalcitabine • Stavudine• Abacavir

Mechanism of ActionZidovudine (AZT)

• A deoxythymidine analog

• competitively inhibits deoxythymidinetriphosphate for the reverse transcriptase enzyme

• causes chain termination

Nonnucleoside Reverse Transcriptase Inhibitors

• Nevirapine• Delavirdine• Efavirenz

Mechanism of Action• Bind to site on viral reverse transcriptase,

resulting in blockade of RNA and DNA dependent DNA polymerase activity

• do not compete with nucleoside triphosphates

• do not require phosphorylation• these drugs can not be given alone

Protease Inhibitors• Indinavir• Ritonavir• Saquinavir• Nelfinavir• Amprenavir

Protease Inhibitors• The protease enzyme cleaves precursor

molecules to produce mature, infectious virions

• these agents inhibit protease and prevent the spread of infection

• These agents cause a syndrome of altered body fat distribution, insulin resistance, and hyperlipidemia

Anti-Hepatitis Agents

Immune stimulating agent• Interferon Alfa / Beta• Pegylated Interferon Alfa

Virus replication inhibitor• Ribavirin

Combinational therapies (II)

Release (exit) inhibitorsZanamivir (Relenza®) Oseltamivir (Tamiflu®)

• Neuraminidase inhibitors. Zanamivir and Oseltamivir interfere with the release of progeny influenza virus from infected host cells, a process that prevents infection of new host cells and thereby halts the spread of infection in the respiratory tract

• Lack of enzime functionality prevents cleavage of sialic acid molecules that maintain the viral particles bound to the cell surface, thus preventing the release of new viruses and spread of Influenza(A and B) infections.

VACINAS ANTIVIRAIS

A primeira vacina: Edward JennerVacina para variola

Doença erradicada do mundo pela vacinaçãoUltimo caso 1977 em Somália

Vacinas à moda antiga

Até hoje, muitas vacinas seguem a “moda antiga”

BCG“Bacillus Calmette-Guerin”

Mycobacterium bovis

Paula Romero Rocha ®

Vacinas baseadas no uso domicrorganismo completo

A) Vivo-Atenuado Sarampo-Caxumba-Rubéola/MMRPolio (Sabin-oral)Catapora (Varicela-VVZ)Febre amarela (YFV)

B) InactivadoHepatite APolio (Salk)

Virus inactivados induzem anticorpos mais facilmente

B CD4Clase II

APC

CD8

Clase I

“Direct Priming” “Cross-Priming”

Virus atenuados induzem respostas imunes celulares contra as proteínas recombinantes mais facilmente

B CD4Clase II

APC

CD8

Clase I

“Direct Priming”“Cross-Priming”

Vírus

•HIV/AIDS• Dengue• Encefalite japonesa • Ebola• Madburg

• Gripe suina (Influenza A H1N1)• Gripe do frango (Influenza A H5N1)

Quase todas as vacinas antivirais que ainda precisamos necessitam induzir respostas imunes celulares fortes.

Vacinas atenuadas existentes hoje nao podem ser administradas em mulheres gravidas nem individuos imunocomprometidos pelo risco de acontecer uma

infecção produtiva.

Imaginem as novas vacinas que ainda faltam por ser desenvolvidas!!!

VACINAS DE SUBUNIDADE

A) Componentes isolados do patógeno (não para vírus)

- Polissacarídeo (Hib, Pneumococo, Meningococo)- Substâncias secretadas (toxoides, proteínas...)

B) Componentes recombinantes

- DNA /RNA - Bactérias - Vírus- Fungos (leveduras)

Vacinas de subunidade

Vamos então falar de quimeras modernas e de vacinas de

subunidade...

Vetores recombinantes- Fungos (leveduras)

Saccharomyces cerevisiae / pombePichia pastoris

- BactériasLactobacillus caseiShigella flexineriSalmonella enterica serovar Typhimurium e Typhi

- VírusAdenovirusPoxvirus (MVA, Fowlpox, Canarypox...)InfluenzaAAVBaculovírus

- DNA /RNA Plasmídeos pVAX, pcDNA3.1, pCI, ...

Hepatite B

Saccharomyces cerevisiae HBsAg Engerix B®

Papilomavirus

Saccharomyces pombe HPV-16/18/6/11 L1 VLP GARDASIL®

Recombinant baculovirus HPV-16/18 L1 VLP Cervarix™

PROTEÍNAS RECOMBINANTES VACINAIS:

AS QUIMERAS DO SÉCULO XX

Porém, em muitos casos de infecções virais, as proteínas purificadas não são eficientes como vacinas.

VACINAS DE DNA: AS QUIMERAS RECOMBINANTES MAIS SIMPLES

Porem, a tecnologia das vacinas de DNA precisa ser melhorada.

No momento não são suficientemente imunogênicas

e precisam de muito DNA para funcionar

VETORES VIVOS RECOMBINANTES: AS QUIMERAS DO SÉCULO XXI

Não seria bom poder pensar diferente quando falasemos

Vamos tomar vacina!

BACTERIAS

Poderia acabar sendo até

uma boa festa!!

LEVEDURAS

VETORES VIVOS RECOMBINANTES: AS QUIMERAS DO SÉCULO XXIExemplo: Os vírus recombinantes