Overview of Zika. Alan D.T. Barrett Department of Pathology Sealy Center for Vaccine Development University of Texas Medical Branch Galveston TX

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1 Overview of Zika Alan D.T. Barrett Department of Pathology Sealy Center for Vaccine Development University of Texas Medical Branch Galveston TX

2 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.

3 ZIKV: 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

4 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

5 ZIKV in the Americas

6 Current ZIKV activity

7 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.

8 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?

9 ZIKV 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.

10 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.

11 Cumulative Zika suspected and confirmed cases reported by countries and territories in the Americas, Updated as of 2 June 2016 Sub-Region Country / territory Suspected Zika Confirmed Zika Deaths among Zika cases North America Mexico Subtotal Central America Belize Costa Rica 2, El Salvador 11, Guatemala 1,089 1,162 0 Honduras 21, Nicaragua Panamá Subtotal 36,473 1,793 2 Latin Caribbean Cuba Dominican Republic 2, French Guiana 6, Guadeloupe 6, Haiti 1, Martinique 26, Puerto Rico 10,535 1,170 1 Saint Martin Subtotal 54,777 2,232 1 Andean Bolivia Colombia 80,953 6,402 0 Ecuador Peru Venezuela 31, Subtotal 112,669 6,913 0 South Cone Argentina 1, Non Latin Caribbean Brazil 154,270 39,993 3 Paraguay Subtotal 156,156 40,020 3 Aruba Barbados Bonaire Curacao Dominica Grenada Guyana Jamaica Saint Barthelemy Saint Lucia Saint Vincent and the Grenadines Sint Maarten Suriname 2, Trinidad and Tobago United States Virgin Islands Subtotal 3, Total 363,990 52,003 10

12 Countries and territories in the Americas with GBS in the context of Zika virus circulation. (WHO, June 2, 2016).

13 . Countries and territories in the Americas reporting confirmed and suspected cases of Zika virus disease in pregnant women (WHO, June 2, 2016)

14 Countries and territories in the Americas with reported congenital syndrome associated with Zika virus infection (WHO, June 2, 2016).

15 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

16 West Nile Clinical Manifestations ( ) 0.1% Death 1,352 80% 20% <1% Central nervous system 13,204 West Nile Fever 350,000 Asymptomatic Infections 1,600,000 The Iceberg

17 Zika Clinical Manifestations ( ) 0.0%? Guillain-Barre syndrome 1%? 20% 1-15% Death 10 Congenital Zika Syndrome???? Zika Fever????? 80% Asymptomatic Infections????? The Iceberg

18 Viremia (active virus multiplication) FACTS Viremia low and transient in humans and NHPs (10 4 pfu/ml; 10 7 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?

19 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.

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21 Zika cross-reactivity flavivirus naive Lanciotti et al., 2008

22 Zika cross-reactivity Zika as a secondary flavivirus infection Lanciotti et al., 2008

23 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.

24 Candidate ZIKV vaccines

25 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?

26 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

27 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

28 Animal models

29 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), 10 6 pfu, intraperitoneal route in 6 week old mice. AG129 mouse model: (Panama, 2015; Asian Lineage), 10 4 pfu, intraperitoneal route in 12 week old mice.

30 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?

31 ZIKV in NHPs Indian-origin rhesus macaques infected with French Polynesia Asian lineage Zika virus were rechallenged with 10 4 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)

32 Human Challenge Model Interest in developing human challenge models as has been done for dengue. Alternative/supplement traditional clinical trials. Ethical and safety considerations?

33 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.

34 Surrogate of protection for licensed flavivirus vaccines Flavivirus Japanese encephalitis Live, subunit or inactivated? Live and inactivated Serotypes Test Quantity 1 PRNT/neutralization 1 in 10 Yellow fever Live 1 Log neutralization index PRNT/neutralization Tick-borne encephalitis in 10-50*??? 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 log 10 neutralization index of 0.7 originally based on studies in nonhuman primates * Seroprotective levels of neutralizing antibodies, measured by PRNT, have not been determined

35 Passive protection in animal models

36 Passive protection of mice demonstrated with mouse Fab Dai et al. Cell Host & Microbe , Cell DOI: Host & Microbe ( /j.chom ) 19, DOI:

37 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.

38 Is ZIKV one serotype?

39 Amino Acid ML Tree: E Protein

40 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?

41 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) PRNT 50? PRNT 60? PRNT 80? PRNT 90? Micro-neut Flow cytometry A standardized, validated assay will be important to quantitate neutralizing antibodies

42 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)

43 Use Zika vaccine development as the blueprint for Vaccine development pathway for emerging diseases?