Zika: Infection,, and Protection Roxanne P. Liles, Ph.D., MLS(ASCP) CM Assistant Professor of Biology Louisiana State University at Alexandria 318-473-6518 rliles@lsua.edu Zika Virus Basics Virion: Enveloped o Glycoproteins E and M embedded in envelope o Anti-E antibodies are protective o Glycosylated residues vary among strains and other flaviviruses Genome: Positive sense (messenger) ssrna virus Arbovirus Zika Virus Basics Flaviviridae Family o Dengue o West Nile o Japanese encephalitis o Yellow fever virus Flaviviridae Flavivirus Disease Vector Vaccine *Dengue (serotypes 1-4) Severe febrile, rash, arthralgia Hemorrhagic fever Misdiagnoses of Chikungunya Immune Enhancement infection Zika Self-limiting, mild, febrile illness Neurological complications of the fetus and adults West Nile 80% Asymptomatic Fever, rash, headache Encephalitis, meningitis Aedes aegypti Aedes aegypti A. albopictus Aedes sp Anopheles sp Culex sp Culiseta sp Live, recombinant, tetra valent, multidose (YF-17d) None None *Japanese encephalitis *Yellow fever virus <1% develop clinical illness Fever, headache, vomiting Neurologic Seizures in children Acute phase: fever, muscle pain Toxic phase: fever, jaundice, albuminuria Culex sp. Aedes sp. Haemogogus sp. Inactivated virus, multi-dose, JE-vax Safe, single dose effective, affordable UTMB.edu Aedes aegypti mosquito Tropical and subtropical distribution Diurnal feeding habits Adapted to urban dwellings Resistant to many control measures o Eggs withstand drying Virus Biological vector o Dengue o Chikungunya o Yellow fever o West Nile o Zika Zika Virus Transmission Cycle Maintained in nature o Vertebrate host o Arthropod vector Amplifying host 1
Global Distribution of Aedes sp. Approximate U.S. Range of Aedes sp. Zika Virus Lyle R. Petersen, M.D., M.P.H., Denise J. Jamieson, M.D., M.P.H., Ann M. Powers, Ph.D., and Margaret A. Honein, Ph.D., M.P.H. March 30, 2016DOI: 10.1056/NEJMra1602113 Virus Spread Timeline 1947: Scientists conducting yellow fever surveillance isolate novel virus from a sentinel rhesus monkey in Zika forest 1948: Virus recovered from Aedes sp. mosquito in the Zika forest. 1952: First human infections detected in Uganda and the United Republic of Tanzania in a study demonstrating the presence of neutralizing antibodies to Zika virus in sera. Virus Spread Timeline 2007: Zika outbreak on Yap Island in South Pacific, RT- PCR detection of Zika. 2013: French Polynesia outbreak with high incidence of microcephaly 2014: Zika virus imported into Americas by sporting event(?) 2015: Autochthonous Zika virus circulation in the Americas. 1954: The virus is isolated from a young girl in Nigeria. Zika Virus Global Distribution Zika Disease Acute infection o 2-7 days duration Viremia 1-5 days after mosquito bite Asymptomatic infection Virus cleared after 2 weeks *Serological studies inconclusive for detection of Zika virus infection due to Flavivirus cross-reactivity 2
Microcephaly Smaller than average head Fetal neurological damage o Underdeveloped brain o Impaired hearing and sight Greatest risk during 1 st trimester Causes include o Alcohol / drug abuse o Malnutrition o Environmental toxins o Infectious agents (TORCH) Microcephaly Infectious agents (TORCH) o Toxoplamsa o Other (HIV, Varicella, Syphillis) o Rubella o Cytomegalovirus o Herpes Simplex Detected upon ultrasound (U.S. ~20wks) or birth *Pre-Zika Brazil set limit at 10 th percentile Zika Virus and Microcephaly Zika causes Microcephaly (Centers for Disease Contol 4/13/16) o ZIKV RNA detected: Placenta Amniotic fluid Fetal tissues o Anti-ZIKV IgM antibody Amniotic fluid Cerebrospinal fluid o Mechanism of vertical transmission unknown o Spectrum of congenital disease unknown o Rates of transplacental transmission unknown Guillain-Barre Syndrome Acute inflammatory demyelinating neuropathy Muscle weakness and rapid onset paralysis Autoimmune condition Triggered by molecular mimicry of infection o C. jejuni o HIV o Influenza Full recovery in most cases Zika Virus and Guillain-Barre Syndrome Retrospective study of French Polynesia outbreak o 42 Gullain-Barre Syndrome cases o anti-zikv IgG or IgM present o Neutralizing antibodies in 100% of GBS cases Hypothesized mechanisms: Sequential arbovirus infection exacerbates immune response Zika virus mimics host proteins Enhanced tropism and direct nerve damage ZIKV envelope E protein vary by strain, may enhance pathogenicity Treatment Acute Zika virus infection o Pain / fever medicine Guillain-Barre Syndrome o Hospitalization o Close monitoring o Plasma exchange Microcephaly condition o Supportive care o Long term effects unknown 3
Human Transmission Vector-borne o Humans are amplifying host Blood-borne o Blood supply transmission -Brazil Sexual transmission o Semen 28 day donation deferral o Saliva Zika virus RNA detected post viremic phase Maternal transmission o Transplacental o Vertical transmission rates vary by trimester o Breast milk (may contain Zika Virus RNA) Clinical history o Travel to endemic regions o Exposure to vector Laboratory Findings o Leukopenia o Activated lymphocytes o Albuminemia o Thrombocytopenia Serology IgM Antibody capture o IgM increases within1 week - months o ELISA o Cross reactivity with Flaviviridae o (Yellow fever, Dengue, West nile) o Plaque reduction neutralization test (PRNT) Differentiates antibody specificity Labor intensive and costly Requires live virus Reverse transcriptase PCR (RT-PCR) to detect nucleic acid o Transient serum viremia 1wk after onset of illness o 10 weeks post infection in maternal serum with congenital infection o Saliva samples exhibit greater sensitivity than serum o Urine contains higher viral load, longer duration than serum Diagnosis for travelers in endemic Zika virus regions Immunohistochemistry analysis o Fetal tissues Specimen collection o Body fluids 2-6⁰C or -70⁰C Serum /CSF 0.5-1.0ml Urine, saliva, semen, amniotic fluid 1.0ml o Fetal tissues Formalin fixed or frozen Confirmation using PRNT 4
Blood products o FDA Investigational Test to screen blood products Roche fully automated, high volume system Zika virus Nucleic acid screen for RNA in plasma o Endemic regions not accepting blood donations (screen for WNV) Protection Life-long immunity after acute infection Vaccine Development o Current ZIKV strains exhibit 99% sequence identity Considerations modifying YF-17d with E and M glycoproteins Differential E glycoprotein glycosylation o Antibody-Enhancement due to cross reactivity with Flaviviridae ZIKV protective antibodies and YFV YFV immunization not protective for ZIKV Antibody Immune Enhancement Antibodies produced against one viral subtype from a previous infection (ex.denv1) Acute Infection and Primary Response Subsequent infection with different subtype (DENV2) stimulates anamnestic response Antibodies fail to neutralize virus Phagocytic cells become virally infected, because virus was not inactivated IgM first class of antibody secreted IgG account for 80% of antibodies Results in higher viral loads in host Diamond, M. S. Evasion of innate and adaptive immunity by flaviviruses.immunology and Cell Biology 81, 196 206 (2003). Anamnestic Response Antibody Antigen Interaction Neutralization Opsonization Complement Cascade 5
Antibody Immune Enhancement (AIE) Antibody Immune Enhancement (AIE) AIE results in higher viral loads AIE causes more, severe disease Increasing concern in arbovirus endemic regions Consideration for flavivirus vaccine development http://www.the-scientist.com/images/march2013/dengue_virus.jpg http://www.the-scientist.com/images/march2013/dengue_virus.jpg Protection Vector control programs o Eliminate standing water o Larvicides o Simple traps Genetically engineered mosquitoes o Release of homozygous males yield nonviable offspring o Endosymbiont Wolbachia infected mosquitoes Lab Safety Zika virus is classified as a Level 2 pathogen Sensitive to potassium permanganate 24 hour contact with ether > 60 degrees C Resistant to 10% ethanol Epidemic Outlook Questions Recent global emergence of Dengue, Chikungunya, and Zika Common underlying mechanism o Urbanization o Globalization o Increase in vector range Viral mutations influence transmission and virulence Naïve population Roxanne P. Liles, Ph.D., MLS(ASCP) CM Assistant Professor of Biology Louisiana State University at Alexandria 318-473-6518 rliles@lsua.edu 6