# Presentation: 271679

## CURRENT STATUS OF WEST NILE VACCINE DEVELOPMENT

**Alan D.T. Barrett**
- Department of Pathology,
- Sealy Center for Vaccine development
- Center for Biodefense and Emerging Infectious Diseases,
**U**niversity of **T**exas **M**edical **B**ranch at Galveston

## Major flavivirus diseases

- Dengue
- Japanese encephalitis
- Tick-borne encephalitis
- West Nile
- Yellow fever

## Current flavivirus vaccines

**Live attenuated**
- Israel turkey meningoencephalomyelitis  (V)
- Japanese encephalitis  (B)
- Wesselsbron (V)
- Yellow fever (H)
**Inactivated**
- Japanese encephalitis (H)
- Kyasansur Forest disease (H)
- West Nile (V)
- Tick-borne encephalitis (H)
- H = human, V = veterinary, B = both

## West Nile vaccines

- Human vaccine.
- Veterinary vaccine.

## West Nile Virus Transmission Cycle

**West Nile Virus Transmission Cycle**

- Mosquito vector

- Incidental infections

- Bird
- reservoir hosts

- Incidental  infections

## Potential hosts of West Nile virus

- At least 225 species of birds
- At least 49 species of mosquito
- At least 28 species of mammals, inc. cats, dogs, sheep, llama, wolf, goats, squirrels, skunks, etc...
- Alligators.....

## West Nile virus

- Family: *Flaviviridae*
- Genus: *Flavivirus*
- Japanese encephalitis group
- 		*Cacipacore virus*
- 		*Koutango virus*
- 		***Japanese encephalitis virus***
- 		*Murray Valley encephalitis virus*						(Alfuy virus)
- 		***St. Louis encephalitis virus***
- 		***Usutu virus***
- 		***West Nile virus***
- 			(Kunjin virus)
- 		*Yaounde virus*

## Approaches to developing vaccines

- Inactivated virus
- Live attenuated
- Recombinant poxviruses
- Infectious clone-derived live attenuated
- Chimeric viruses
- Subunit
- Yeast
*E. coli*
- Baculovirus
- DNA/RNA

## JE vaccine does not induce neutralizing antibodies against WNV

- Kanesa-Thasan et al AJTMH 66: 115-116, 2002.
- Volunteers immunized with inactivated JE vaccine and bled after vaccination.
- Sera did not contain antibodies that neutralized WNV.
- Inactivated JE vaccine will not protect against WNV?

## West Nile vaccine in Israel

- Investigated Israel Turkey meningoencephalomyelitis virus (ITMV) as vaccine in 3 week old geese.
- Live attenuated chick embryo adapted vaccine developed in 1975 (103EID50/0.5ml).
- No NT ab but 92% protection in geese.
- Why does ITME vaccine protect against WNV challenge?

## Inactivated vaccine protects geese against WN challenge

- Studies in Israel
- Prepared mouse brain formalin-inactivated WN vaccine based on goose (NY-like) strain.
- Geese challenged with WN virus by ic route
- Killed WN virus gave 52-80% protection

## Veterinary vaccine I

- Available in some areas during 2001
- Manufactured by Fort Dodge Animal Health.
- Formalin-inactivated, Killed Vaccine; two doses, 1ml, IM, 3 weeks apart
- $20-30 per dose
- Booster doses required annually
- Effectiveness?

## Veterinary vaccine II

- Ng et al Dev Biol Stand 114: 221-227, 2003
- Amount of antigen in dose not stated.
- NT abs higher than WNV DNA vaccine in horses at day 14 post second dose.
- 17/19 horses NT ab positive (1:5) @ 1 year post vaccination.
- 1/19 vaccinated horses had viremia following challenge  94% preventable fraction.

## Veterinary vaccine III

- Nusbaum et al Avian Dis 47: 750-752, 2003
- Immunized Chilean flamingos and red tailed hawks IM with 0.2ml commercial inactivated vaccine. None of 13 birds tested had detectable ab to WNV.
- Tesh et al EID 8: 1392-97, 2002
- 8/9 hamsters had HI & CF ab; 5/9 had low PRNT (1:10-40);
- 2/9 hamsters had viremia (_<_ 20,000 pfu/ml) post challenge with 10,000 pfu WNV

## Inactivated vaccine for humans?

- Baxter-Immuno have inactivated tick-borne encephalitis vaccine marketed in Europe.
- TBE formalin-inactivated cell culture
- 2 doses, 2-13 weeks apart; booster 1 year,
- re-boost every 3-5 years
- >95% seroconversion after two doses
- Using same technology for inactivated WN vaccine?

## West Nile DNA vaccine I

- Davis et al. J. Virol. 75, 4040-47, 2001
- prM & E genes from WN –NY
- JEV transmembrane signal sequence
- Immunize: one dose by IM route
- Mice – 3-week-old female ICR; challenge ip 1000LD50 at 6 weeks post-immunization or via mosquito  100% protection.
- Equines – 4 of various ages; challenge via mosquito  seroconversion & no viremias

## West Nile DNA vaccine II

- Yang et al. JID 184:809-16, 2001
- Synthetic C gene from WN –NY
- Used human Ig secretory leader signal
- Immunize: one dose by im route
- Mice – 6-8-week-old female Balb/c
- Antigen specific humoral and cellular immune responses
- Antigen specific Th1 and CTL response
- No challenge studies.

## WN DNA vaccine III

- Turell et al. EID 9: 1077-81,2003
- 0.5mg DNA vaccine (Davis et al vaccine) by oral or IM routes in fish crows (*Corvus ossifragus*).
- 9/9 IM vaccine and 4/8 oral vaccine immunized birds survived WNV challenge.
- No NT abs prior to challenge and no sterile immunity following challenge.

## Lanciotti et al. 1999. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern U.S. [Science 286:2333-337.]

## Kunjin virus as a vaccine?

- Hall et al PNAS 100:10460-64, 2003
- KUN virus in plasmid.
- 4-5 week old Balb/c mice immunized i.m. with KUN plasmid
- Viremia very low.
- PRNT: 1:10-20
- 0.1-1ug KUN plasmid DNA protected mice from challenge
- 1ug protected mice against ic or ip challenge 20pfu WNV

## Canarypox-vectored vaccines

- Veterinary vaccines; used in Europe
- KANAPOXTM derived from ALVAC
- Applicable to mouse, ferret, dog, car, horse, pig & primates
- WNV prM/E vectored vaccine
- Antivector immunity does not interfere with booster immunizations.
- Can be combined with live & inactivated vaccines as immunogens.

## Recombinant WN-E protein

- Wang et al. J Immun 167: 5273-5277, 2001
- Thioredoxin 100%E and mbp-80%E
- Immunize  C3H/HeN mice with 20ug rE-fusion protein
- Serum PRNT = 1280
- Mice protected from 10LD50 challenge
- Limited passive protection
- Other recombinant proteins being evaluated by other laboratories

## ChimeriVaxTM Technology Platform

*Chimeric live attenuated vaccines utilizing yellow fever 17D as a vector for envelope genes of other flaviviruses*
- ChimeriVaxTM-JE (Japanese encephalitis)
- ChimeriVaxTM-DEN (Dengue)
- ChimeriVaxTM-WN (West Nile)

## Derivation of Attenuated Yellow Fever 17D Virus Strain

|  | Asibi Virus |
| --- | --- |
|  |  |
|  | 176 passes in chick embryo tissue |
|  |  |
|  | 17D Attenuated Variant
(17D-204 p233-239)
(17DD p286-288) |

## ChimeriVaxTM

- Promising vector for novel flavivirus vaccines
- Less neurovirulent than parental YF 17D
- Infectivity (viremia) similar to YF 17D
- Neutralizing antibody responses similar to YF 17D
- Protects against severe challenge (e.g. JEV by IC route in monkeys)
- Not infectious for mosquitoes
- Well-tolerated and immunogenic in humans (JE)

## ChimeriVaxTM-WN Used WN-NY #383-99 for prM & E genes

- Human vaccine
- WN-F107-V316-R-440
- ChimeriVax-WN 104 pfu sc  protects 12/12 monkeys against ic challenge of 105 pfu WN-NY99  no viremia/clinical signs

- Veterinary vaccine
- WN wildtype
- Johnson et a Med Vet Ent 17:235-43, 2003
- ChimeriVax-WN replication restricted in mosquitoes  *Cx. tritaeniorhynchus*, *Cx. nigipalpus*, *Cx. quinquefasciatus*, *Ae. aegypti* and *Ae. albopictus*.

## ChimeriVaxTM-WN is not efficacious in Fish Crows (Corvus ossifragus)

- Langevin et al AJTMH 69: 78-80, 2003
- ChimeriVax-WN failed to prevent viremia (8/8) in immunized birds.
- 2/8 birds succumbed to WNV challenge
- Yellow fever virus does not replicate in birds.

## DEN4/WN chimeras

- Pletnev et al. PNAS 99: 3036-41, 2002; Pletnev et al. Virol 314:190-95, 2003
- Used DEN4 backbone with WN prM/E genes.
- WN neurovirulence reduced 20,000-fold in 3-day-old mice
- WN neuroinvasiveness reduced >10,000-fold in 3 week old mice
- IP immunization with 1000 ffu  1:1200 PRNT
- _>_90% mice resistant to 100LD50 challenge
- WN/DEN4 chimera gave 100-fold reduction in viremia compared to WN or DEN4 in rhesus monkeys
- Prevented viremia in WN challenged monkeys