Viral infections….

and antivirals

Herpes simplex virus-Primary infection latency reactivation Recurrence-Recurrent stromal disease (immune mediated)

-lead to collagen disorganization and corneal scarring

-blindness requires corneal transplant --partly defined by the genetics of virus-Partly defined by genetics of the host

Infection of neurons

latency

reactivation

of HSV-1

axonal transport

Regulating HSV Lytic/ latent switch

HSV LAT RNA Latency Associated TranscriptAbundantly made at latency -No protein- miRNAs?

Adaptive cellular Immunity plays a role in latency

Varicella zoster virus (VZV)Only rare eye disease with varicella (primary infection)Major eye problems with zoster on the head

Varicella zoster virus (VZV)• Alphaherpesvirus , genetically related to HSV-1

• Smallest Herpesvirus 125 kbp genome,• Only close cousin is in monkeys

• Simian varicella

• Same targets as HSV-1 (skin and mucous membranes:- and sensory neurons for latency

• But a very different lifestyle from HSV-1

Virus is endemic; >95% infected-

Seasonal- Transmitted with direct contact or airborne droplets• late winter & spring

Disease:•Primary infection - chicken pox•Used to be 5000-9000/year hospitalized, 100/year deaths

Primary and reactivated VZV disease

Primary VZV infection - Chickenpox• Inhale by aerosol droplets

• Infects resident immune T cells and mono/dendritic cells in tonsils/Waldemyers ring

• Also Transfer to T cells in regional lymph nodes

• Reaches skin by T cell viremia - systemic spread

• Infiltration into skin –virus seeds dermal skin layers-

• Grows for 10-21 days- regulated by innate immunity

• Cleared by adaptive immunity• Problematic in adults- Pneumonia-

causes death. Why?

Lumpkin E A et al. 2010

Perry and Whyte 1998

Varicella Vaccination Live Attenuated- OKA

• 86-95% effective in children • Now mandated to 5+ years of age -two shots• long term protection from disease (not infection)•Not so effective in adults

•Herd Immunity- reduce spread in those not protected

•Shift the incidence of chicken pox to older ages (adults) where the complication and death rate rise sharply.

•No varicella-no boosting of immunity throughout life• Earlier zoster?

Establishment of the VZV latent state

• VZV in skinsensory nerve axons retrograde axon transport neuronal latency• VZV in T cells directly infiltrate ganglia neuronal latency• VZV spread over entire neuraxis over body autonomic and sensory ganglia

Then we get old……. Then we get old……(what would Michael Jackson have looked like?..)

Herpes zoster

-occurs in 1/5 to 1/3 of adults--1 in 20 get zoster on head

Termed HZO if VZV from 5th cranial nerve

Triggers of zoster?

Is there Subclinical reactivation?

What’s different from HSV-1 reactivation?

- frequency- intraganglionic spread- ganglionitis-ganglionic necrosis

Zoster- Risk FactorsZoster- Risk Factors

Age - 84% – after age 60

Cellular immune status – AIDS– Radiation Therapy– Cancer (esp. lymphoma)– medical immunosupression therapies

BMT & Transplants (30-55% in a year!)

CD4 appear more important than CD8 Cellular>>>>humoral immunity in control

Harpaz R et al 2008

Herpes Zoster -signsHerpes Zoster -signs Pain

-Before, during and after Vesicular skin lesions

Rarely cross midline Large lesions- wide area-

- viral replication in the ganglia

- mass delivery of virus to skin

HUTCHINSON’S SIGN (lesion on nose tip)- HZO

Fever & Depression. Tic (“tic deleroux”)

Some ocular infections, Pain and CNS disease occur without clinical zoster (“Sine Herpete”) DIAGNOSIS? -CSF and PCR

Examples of corneal zosterExamples of corneal zosterVZV Can infect every ocular tissue

to cause:-

Punctate epithelial keratitis (PEK) Dendritic keratitis

– -w/o terminal bulbi Stromal keratitis/inflammation

– -Harder to treat than HSV-1 Neurotrophic keratitis

– -Total loss of corneal sensation– -iatrogenic ulceration

Rarer Findings Uveitis, retinitis, Acute retinal necrosis. ACT FAST! Loss of retina in days

Neurotrophic KeratopathyNeurotrophic KeratopathyThe “diabetic foot” of the eyeThe “diabetic foot” of the eye

• ~ 8% of HZO patients develop total loss of corneal sensation

~ 3% of HZO patients develop neurotrophic ulceration

Iatrogenic insults are the main reason that neurotrophic corneas get into trouble.

VZV and Pain• Zoster affect 300,000 to 1 million

people a year in the US• 90% will seek prescribed

medication for pain• 30% will develop debilitating

chronic pain known as Post Herpetic Neuralgia (PHN)

• Many PHN patients get no benefits from any form of treatment

Why is there pain?Ganglionitis Ganglionic necrosisNeuronal connective plasticity and reorganizationDemyelyination Cell-Neuron Fusion-cytoplasmic mixing

Ocular/ neurological complications of VZV• Many types of

VZV neurological disease

• Most are rare and mis-diagnosed

• Persistent VZV in CNS vasculature or CNS/brain leads to ….

• Cognitive deficits

• Stroke• Headaches• Migraines?• seizures

Zoster Treatment

First, treat the eye and skin - remove virus

-3+ fold higher ACV HSV dose needed for effect on VZV- many physicians under-treat

Then:

Treat immune disease under antiviral cover

Treat acute pain- NSAIDS + antivirals

Treat the post-herpetic pain

Topical AcyclovirOral Valacylcovir

Things to try to Treat PHN– Anti-convulsants (affect central pain modulation by GABA

Gabapentin, lamotrigine, carbamazepine

– Anti-depressants (block serotonin/norepinephine re-uptake Tricyclics- Amytriptyline, venlafaxine

– Opioids (side effects-use as 2nd line only)

– Capsaicin patch (Quitenza)- depletes substance P

– Lidocaine patch with NSAID – Antivirals? Debatable- p[robably no active virus growth

– Steroids? Debatable- most PHN is not inflammatory

Many (1/3rd?) PHN patients receive less than 50% improvement from any current therapy

Vaccination to prevent zoster– Zostervax- same as varicella vaccine- 14X more virus

– VZV immune people get it. – Recommended > 50 yrs, may eventually need two doses – Is the only human herpesvirus vaccine so far

– Partial efficacy - not everyone is protected– 51% drop in zoster incidence– 68% fall in “burden of illness” (including PHN)

Adenovirus follicular conjunctivitisAdenovirus follicular conjunctivitisvs others-differential diagnosis vs others-differential diagnosis

Adenoviral Infections

• non-enveloped virus, • 34Kbp DS-DNA, many viral proteins

• At least 57+ identified Serotypes• Three major ocular diseases

•Epidemic Keratoconjunctivitis (8, 19 and 37+ several

new serotypes and interrecombinant strains)• Pharyngoconjunctival fever (3,4, & 7)

Epidemic Kerato-conjunctivitis transferred by hands, instruments, solutions. Adenoviruses survive >35 days on dry surface Many epidemics arise from optometrists and ophthalmologists offices.

you are the spreaders… Patients remain infectious for 14 days after onset of symptomsUsually One eye, then other (milder)Lasts 7 days -2 weeks

Source of new isolates- - Japan/Asia- Japan-EKC is a reportable disease- Hawaii west coast -mixing ground

Clinical SymptomsClinical Symptoms Foreign Body Sensation Tearing Photophobia Sore Throat Breathing Problems Conjuntivitis

NO ANTIVIRAL – YET– -Correct timely diagnosis an issue

After virus…...-Subepithelial infiltrates

(immune mediated)-last weeks to months - treat with steroids - requires slow withdrawal

Adenovirus EKC management Adenovirus EKC management

CMV and retinitis•80% are seropositive•Virus is endemic-

early childhood•Usually asymptomatic •Retinitis Rare outside

of HIV/AIDS-A major factor in “will to live”Of AIDS patients

SignsPhotophobiaEye Pain/rednessFloatersVision lossUsually initiates monocular

Other Viruses causing conjunctivitis or Eye Disease

CM and EBV herpesviruses affecting most people – may cause conjuntivitis and ,rarely, corneal keratitis

Entero/coxsaccivirus- Hemorrhagic conjunctivitis -begins as eye pain, then red, watery eyes with swelling,

- light sensitivity, and blurred vision.

HIV (and everything resulting from it) Newcastle disease virus Vaccinia Mollocsum contageosum (lid lesions) Papilloma (lid lesions) Measles (Conujuntivitis)

Important Ophthalmic antivirals

Triflorothymidine (viroptic) HSV-1>> VZV

Acyclovir and valacyclovir HSV-1 and VZV

Ganciclovir and valganciclovir CMV retinitis, Adeno,

Foscarnet (phosphonoformate) CMV (GCVr)> HSV,VZV

Cidofovir CMV (GCVr)

HAART HIV/AIDs

Trifluridine (viroptic)

Analog of deoxyuridine nucleoside

Incorporated into DNA

CF3 blocks base pairing in DNA

Has higher affinity for viral DNA pol over cell pol

Used topically only- toxic systemically

Acyclovir, gancyclovir and derivatives

Acyclovir (FDA licensed in 1981)Acyclovir (FDA licensed in 1981)UseHerpes simplex virus 0.1-3 ug/mlVaricella Zoster virus 5-20human cytomegalovirus 60-200 (not deemed “clinically effective”)

Safe in Long term Prophylaxis treatments - Herpes B and recurrent HSV 2

Prodrug mechanism- only active (and activated) in virus infected cellsVirtually non toxic in uninfected cell100 x more active in HSV—1 infected cell.Once activated, has higher affinity (50x) for HSV DNA polymerase over cellular DNA polymerase.

ACV Mechanism of Action

–HSV VZV Thymidine (nucleoside) Kinase activates it –ACV TP binds Viral DNA polymerase >>>>> cell pol–Incorporated into DNA - acts as DNA chain terminator

ACV - Resistance Readily arises in culture

– Defect /loss of viral TK – Mutation of DNA polymerase- alters ACV affinity

rarely occurs in vivo- why? – Latency in neurons– TK needed for HSV reactivation– TK- viruses don’t reactivate– – ACVR arise In AIDS patients with long treatments

Have Pol mutations: or Low persistent viral replication: or Have minimal TK levels sufficient to enable reactivation from latency

– Not sufficient to activate/ phoshorylate ACV

Valacyclovir“Valtrex”

Acyclovir

Liver

Oral forms of Acyclovir

ACV alone is degraded by the stomach

Valine Ester derivative has high oral- bioavailability

–e.g. 63-72% absorption vs 15% for ACV

Is de-esterified by liver on first pass ACV

Allows reduced dosing and taking by mouth

N

NN

N

N

OPh

O to 3’ end

To 5’ end

GMP

O

Gancyclovir

N

NN

N

N

O

OO

O

Gancyclovir and Valgancyclovir - drugs to combatHCMV disease

Ganciclovir (Cytovene)Ganciclovir (Cytovene)

used for hCMV – also used for adenovirus (for some serotypes, it works)– also used for stubborn VZV and HSV

works much better than ACV for CMV disease– retinitis and systemic disease in transplant patients

BUT

GCV Requires IV dosing but val-GCV (ester form) by mouth – GCV is More toxic than ACV- Why?

GCV-PPP also inhibits host cell polymerase- much less selective

– GCV Does not cross retinal/brain barriers well Often use ocular implants for retinitis GCV increases AZT toxicity- bad for HIV patients

GCV- Mechanism of action-a DNA chain terminator

–CMV has no TK gene

–CMV uses a protein kinase (UL97) to phosphorylate GCV (and ACV)

GCV Resistance• Arises due to long treatment for CMV diseases(upto 10% In Retinitis and organ transplants)

•Rare- mutations in UL97 protein kinase•( UL97 is needed for hCMV to efficiently assemble)

•Mutations in DNA polymerase that alter affinity

• High GCV-resistant CMV have both genes altered

GCV

N

NN

N

N

O

OO

O

Foscarnet (phosphonoformate, PFA)

• Mechanism of action:– All polymerases need P-P as cofactor– PFA analog of pyrophosphate (P-P)– binds to DNA polymerase – PFA blocks P-P binding– resistance – altered DNA polymerase

• Efficacy/toxicity– active on nucleoside resistant viruses

• Acts at different site to GCV/ACV – Toxic in bone, kidney, neuronal deposits

• Uses:– CMV retinitis and GCVr CMV in transplants– rare use on HSV and VZV ARN– Rare use on systemic HSV and VZV

OH P P OH

OOH

OHO

OH P CH

O

OH

OH

O

PFA

P-P

Nucleoside phosphonates•Cidofovir •Initially ID as anticancer agent•Licensed for CMV retinitis

•Analogs of dNMPs – no initial P step needed• CDV has long intracellular half life

•Has activity to many viral DNA polymerases•Works against :

many adenoviruses, poxviruses, -(used if smallpox resurrects?) herpesviruses , polyomaviruses, HBV? Could be the universal antiviral drug in not so toxic

Lipid Conjugate Technology Lipid Conjugate Technology Exploits Natural Phospholipid PathwaysExploits Natural Phospholipid Pathways

O P

O

O-

O

H H

O(CH2)15CH3

HO

N

N

O

NH2

CMX001CMX001CMX001CMX001

Cidofovir

Non-polar tail

OP

O

O-

O

HO H

O

O

(CH2)14CH3

N+

Polar head

LysolecithinLysolecithinLysolecithinLysolecithin

Broadly active against dsDNA viruses

Approved for treatment of CMV retinitis in patients with AIDS

Requires intravenous infusion

Black box warning for renal impairment and neutropenia

Orders of magnitude more potent than CDV; broadly active

Initially being developed for adenovirus, CMV and smallpox

Orally available

No evidence of nephrotoxicity or myelotoxicity

CMX001CMX001CidofovirCidofovir