Overview of Zika - WHOreported congenital syndrome associated with Zika virus infection (WHO, June...
Transcript of Overview of Zika - WHOreported congenital syndrome associated with Zika virus infection (WHO, June...
Overview of Zika
Alan D.T. Barrett Department of Pathology
Sealy Center for Vaccine Development
University of Texas Medical Branch
Galveston TX
Disclaimer
• Over 700 papers in pubmed on Zika in the last 12 months.
• Impossible to stay up to date as field is moving so fast.
• Only including material in public domain.
ZIKV: 1947-2006
• Zika virus (ZIKV) causes Zika fever (ZF), an acute febrile illness
characterized by a rash, conjunctival injection, arthralgia, myalgia
and headache.
• The disease appears in all age groups with an incubation period
on the order of 3-14 days and a symptomatic phase lasting about
2-7 days.
• Treatment is largely symptomatic.
• The illness is mild in nature with a very low rate of hospitalization.
• The vast majority of patients make a full recovery and while death
is rarely reported, it has primarily occurred in the
immunocompromised or those with other complicating medical
conditions.
• Only 14 clinical cases in the literature from 1951-2006.
Map showing the known distribution of Zika virus based on serosurveys, virus
detection, and laboratory-diagnosed cases. Blue arrows show recent patterns
of spread deduced from phylogenetic studies
Weaver et al Antiviral Research, Volume 130, 2016, 69–80
ZIKV in the Americas
Current ZIKV activity
ZIKV transmission
• ZIKV is primarily transmitted by Aedes spp. Mosquitoes.
• Infectious ZIKV particles have been demonstrated in urine, saliva,
semen, blood products, and breast milk possible vehicles of
transmission.
• Male-to-female and male-to-male transmission of ZIKV have been
reported, but only from individuals with clinical signs/symptoms of
ZIKV infection.
• Establishing person-to-person transmission is difficult, as contacts
frequently have the same environmental exposures.
• Epidemiologic relevance of person-to-person transmission has yet to
be elucidated.
• Although viremia during infection is short-lived, typically lasting less
than 4 days, it appears that infectious virus may persist in semen and
body organs much longer (perhaps months) making it much more
difficult to prevent human-to-human transmission.
ZIKV serology
Serologic evidence in Africa of infection in forest-dwelling
birds, horses, cattle, ducks, bats, elephants, goats,
hippopotamuses, impala, kongoni, water buffalo, sheep,
wildebeest, rodents, and zebras
Serologic evidence in the Americas of infection in monkeys
and humans. No other species examined?
ZIKV 2007- present (ADEM and GBS)
• Most ZIKV infections are asymptomatic (75-80%).
• ZIKV outbreaks have been associated with increased rates of rare
autoimmune neurologic disorders such as Acute Disseminated
Encephalomyelitis (ADEM) and Guillain-Barre syndrome (GBS).
• Both conditions can result from a number of infectious diseases.
• The incidence is ADEM around one tenth that of GBS and little is known
about its occurrence following ZIKV infection.
• There appears to be about a 10- to 20-fold increase in GBS during ZIKV
outbreaks from the baseline incidence of 1-2 cases per 100,000 people.
• It has been reported that the clinical onset of ZIKV outbreak associated
GBS cases is more rapid than typical, with a median of 6 days from the
onset of signs of ZIKV infection to GBS symptoms.
Congenital Zika Syndrome
• Vertical transmission from mother to the fetus during pregnancy.
• Outcomes: placental insufficiency, fetal growth restriction, oligohydramnios,
ocular disorders, auditory impairments, CNS injury and fetal death.
• Signs of CNS injury associated with ZIKV include congenital microcephaly,
ventricular calcifications, migration defects, simplified gyral patterns,
dysgenesis of the corpus collosum and cerebellar hypoplasia.
• Congenital microcephaly is present at birth and is defined as having a head
circumference at least two standard deviations smaller than the mean for
gestational age, sex and ethnicity.
• The risk of congenital microcephaly is likely to be highest if women are
infected during the first trimester, and is estimated to be 1-15 in 100
pregnant women.
• Studies have demonstrated poor outcomes including microcephaly from
infections occurring in the second and third trimester. It is currently not
known whether intra-uterine transmission can occur in pregnant women
who have asymptomatic ZIKV infections.
Sub-Region Country / territory Suspected Zika Confirmed Zika Deaths among Zika cases
North America Mexico 0 314 0
Subtotal 0 314 0
Central America Belize 0 2 0
Costa Rica 2,090 58 0
El Salvador 11,631 46 0
Guatemala 1,089 1,162 0
Honduras 21,025 44 2
Nicaragua 0 207 0
Panamá 638 274 0
Subtotal 36,473 1,793 2
Latin Caribbean Cuba 0 1 0
Dominican Republic 2,370 73 0
French Guiana 6,700 483 0
Guadeloupe 6,320 379 0
Haiti 1,777 5 0
Martinique 26,650 12 0
Puerto Rico 10,535 1,170 1
Saint Martin 425 109 0
Subtotal 54,777 2,232 1
Andean Bolivia 99 11 0
Colombia 80,953 6,402 0
Ecuador 393 143 0
Peru 0 5 0
Venezuela 31,224 352 0
Subtotal 112,669 6,913 0
South Cone Argentina 1,613 19 0
Brazil 154,270 39,993 3
Paraguay 273 8 0
Subtotal 156,156 40,020 3
Non Latin
Caribbean
Aruba 0 17 0
Barbados 316 7 0
Bonaire 0 3 0
Curacao 0 73 0
Dominica 203 28 0
Grenada 0 1 0
Guyana 0 6 0
Jamaica 646 14 0
Saint Barthelemy 19 7 0
Saint Lucia 0 2 0
Saint Vincent and the Grenadines 0 2 0
Sint Maarten 0 7 0
Suriname 2,503 527 4
Trinidad and Tobago 0 16 0
United States Virgin Islands 228 21 0
Subtotal 3,915 731 4
Total 363,990 52,003 10
Cumulative Zika suspected and confirmed cases reported by countries and territories in the Americas, 2015-2016
Updated as of 2 June 2016
Countries and territories in the Americas with GBS in the context of Zika virus circulation. (WHO, June 2, 2016)
.
Countries and territories in the Americas reporting confirmed and suspected cases of Zika virus disease in pregnant women (WHO, June 2, 2016)
.
Countries and territories in the Americas with reported congenital syndrome associated with Zika virus infection (WHO, June 2, 2016)
.
Number of investigated cases of microcephaly and other congenital malformation of the CNS in Brazil by epidemiological week, EW 3 – EW 21 of 2016
Source: Data published by the Brazil Ministry of Health and reproduced by PAHO/WHO
Asymptomatic
Infections
1,600,000
West Nile Fever
350,000
Central nervous system
13,204
West Nile Clinical Manifestations (1999-2011)
“The Iceberg”
Death
1,352 0.1%
<1%
20%
80%
Asymptomatic
Infections
?????
Zika Fever
?????
Congenital Zika Syndrome
????
Zika Clinical Manifestations (2015-2016)
“The Iceberg”
Death
10 0.0%?
1-15%
20%
80%
Guillain-Barre syndrome 1%?
Viremia (active virus multiplication)
“FACTS”
• Viremia – low and transient in humans and NHPs (104 pfu/ml; 107
genome equivalents/ml)
• Sometimes can detect viremia by RT-PCR but cannot recover
infectious virus from serum. What does this mean?
• Hard to isolate virus from serum
• Sometimes no isolates from outbreak (Yap) or one (French Polynesia)
QUESTIONS:
• Human - mosquito - human transmission cycle? (like dengue)
• Humans are dead-end hosts? (like West Nile)
• Non-mosquito-transmission important?
• What are we missing?
• Will ZIKV be like “dengue” or “West Nile”?
• What do we do if ZIKV activity disappears in Summer 2016?
Complexities of evaluating flavivirus immune responses
• Flavivirus serology is a “minefield”. Hard to
serologically identify an infection as due to a
particular flavivirus unless the individual is
flavivirus-naïve.
• Karl Johnson called flaviviruses the “Hall of
Mirrors”
• Challenging to assess and interpret
immunological data due to cross-reactivity.
Zika cross-reactivity – flavivirus naive
Lanciotti et al., 2008
Lanciotti et al., 2008
Zika cross-reactivity – Zika as a secondary flavivirus infection
Yap Island results and flavivirus vaccines
• The neutralizing antibody titer may be higher against a previous
(primary?) flavivirus infection rather than the most recent
heterologous flavivirus (secondary?) infection.
• Individuals who have been previously vaccinated against yellow
fever, Japanese encephalitis, (candidate) dengue, or tick-borne
encephalitis can have a rapid and high neutralizing antibody titer
following infection by a heterologous flavivirus. Usually, seen with
mosquito-borne flavivirus infections (JE, YF and DEN vaccine).
• Will be complex interpreting immune responses following
immunization with candidate ZIKV vaccines in areas where other
flaviviruses co-circulate.
Candidate ZIKV vaccines
Candidate ZIKV vaccine candidates
• Estimated to be approximately 40 candidates. Not all in public
domain.
• All either in discovery or preclinical.
• “Advanced” candidates in mice and NHPs for immunogenicity.
• Phase I in Fall 2016?
Candidate ZIKV vaccines
Live attenuated (4): Recombinant ChimeriVax™ – Sanofi Pasteur;
Recombinant dengue-2 – Instituto Butantan/US NIH; Recombinant
chimeric 17DD – Bio-Manguinhos/Fiocruz; Recombinant ZIKV
infectious clone – UTMB/Evandro Chagas Institute/Brazil Ministry
of Health.
Formalin inactivated purified whole virus (5): Bharat Biotech;
ChimeriVax – Sanofi Pasteur; Bio-Manguinhos/Fiocruz; NewLink
Genetics; Instituto Butantan/ US NIH
Live vectored (4): Measles virus vector - Themis Bioscience/Institut
Pasteur; Lentivirus-vector – Institut Pasteur; MVA-VLP – GeoVax;
Simian Adenovirus – Jenner Institute
Candidate ZIKV vaccines
DNA/RNA (4): DNA – Bio-Manguinhos/Fiocruz; DNA plasmid
expressing VLP – US CDC; GLS-5700 DNA – Inovio/GeneOne
Life Science; DNA –prM/E – US NIH
Subunit E protein (5): Recombinant N-terminal 80% E plus Alhydrogel
or proprietary adjuvant from collaborator – Hawaii Biotech;
Synthetic Replikins peptides – Replikins; Recombinant E protein –
Protein Sciences/Sinergium Biotech/Mundo Sano; Recombinant
flagellin/E protein – VaxInnate; E protein/nanoparticles –Novavax
VLP-based (3): VLP - Bharat Biotech; VLP – Bio-
Manguinhos/Fiocruz; VLP - PaxVax
Animal models
Mice deficient in either interferon αβ (A129) and αβγ (AG129) receptors
• ZIKV not lethal (only viremia) in immunocompetent mice.
• Number of mouse strain/virus strain combinations where
ZIKV strains cause 100% lethal infections.
• A129 mouse model: MP1751 (Uganda, mosquito, 1962;
East African lineage), 106 pfu, intraperitoneal route in 6
week old mice.
• AG129 mouse model: 259249 (Panama, 2015; Asian
Lineage), 104 pfu, intraperitoneal route in 12 week old
mice.
Mouse pregnancy models
• Miner et al. Zika Virus Infection during Pregnancy in Mice
Causes Placental Damage and Fetal Demise. Cell
• Cugola et al. The Brazilian Zika virus strain causes birth
defects in experimental models. Nature.
• Li et al. Zika virus disrupts neural progenitor development and
leads to microcephaly in mice. Cell Stem Cell.
Models use immunocompetent mice.
SJL looks best mouse model?
ZIKV in NHPs
• Indian-origin rhesus macaques infected with French Polynesia Asian
lineage Zika virus were rechallenged with 104 PFU of the same virus
In all three animals, there is no evidence of plasma viremia at any
timepoint following rechallenge. Similar data with Uganda MR766
strain. (Wisconsin National Primate Research Center)
Human Challenge Model
• Interest in developing human challenge models as has
been done for dengue.
• Alternative/supplement traditional clinical trials.
• Ethical and safety considerations?
Correlates of Protection for flaviviruses How do we define protection?
Neutralizing antibody – surrogate for licensed flavivirus
vaccines
Lack of clinical disease
Reduced/lack of viremia
Memory? Important for live vaccines…. YF 17D
vaccine appears to give life-long protective immunity
after one dose. Inactivated vaccines need boosters
every 3-5 years.
Surrogate of protection for licensed flavivirus vaccines Flavivirus Live, subunit or
inactivated? Serotypes Test Quantity
Japanese encephalitis
Live and inactivated
1 PRNT/neutralization 1 in 10
Yellow fever Live 1 Log neutralization index PRNT/neutralization
0.7+ 1 in 10-50*
???
Tick-borne encephalitis
Inactivated 1? PRNT/neutralization 1 in 10
dengue Live 4 PRNT/neutralization? ?????
Zika ???? 1? PRNT/neutralization? ????
+ The level of antibody considered to be protective was an log10 neutralization index of 0.7
originally based on studies in nonhuman primates
* Seroprotective levels of neutralizing antibodies, measured by PRNT, have not been determined
Passive protection in animal models
Cell Host & Microbe 2016 19, 696-704DOI: (10.1016/j.chom.2016.04.013)
Dai et al. Cell Host & Microbe 2016 19, 696-704
DOI: (10.1016/j.chom.2016.04.013)
Passive protection of mice demonstrated
with mouse Fab
Flavivirus “serotypes”
• Studies to date indicate each mosquito-borne flavivirus species
has multiple genotypes, but only one serotype…. Except maybe
dengue?
• Yellow fever: 7 genotypes; one serotype
• Japanese encephalitis: 5 genotypes; one serotype
• Zika: 3 genotypes?; One serotype?
• Dengue: “Four serologically and genetically related viruses”; 4
serotypes? 4-6 genotypes per “serotype”.
Is ZIKV one serotype?
Amino Acid ML Tree: E Protein
Can we infer from other flaviviruses?
• Yes… but some caveats?
• Monovalent vaccine
• Induction of neutralizing antibodies could be potentially a surrogate
of protection…. But how would we measure a Zika-specific
neutralizing antibody response in vaccinees?
• Passive protection studies has been used in licensure of JE, TBE
and YF vaccines… what about Zika?
How do you do a flavivirus neutralization test? • De ja vue!
• Cell type, virus strain, and assay type will influence results.
• Plaque reduction neutralization test (PRNT)
PRNT50?
PRNT60?
PRNT80?
PRNT90?
• Micro-neut
• Flow cytometry
• A standardized, validated assay will be important to quantitate
neutralizing antibodies
What would be needed to develop a surrogate marker of protection
• Standards: Antibodies and validated assay to
measure marker of protection (NIBSC).
• Standards: qRT-PCR to measure viremia in
validated assay (PEI)
Use Zika vaccine development as the “blueprint” for “Vaccine development pathway” for emerging diseases?