Select Agents and Toxins

• National Select Agent Registry

• Established in 1996 after the OKC bombing

• Antiterrorism and Effective Death Penalty Act of 1996

• 42 CFR 72.6

• Responsibility of the Department of Health and Human Services

• 2001 - USA PATRIOT Act (42 CFR 73)

• Agents published

• Federal Register on March 18, 2005

• HHS - Human-related agents

• USDA - Agricultural-related agents

• http://edocket.access.gpo.gov/2005/pdf/05-5216.pdf

Select Agents and Toxins

• 7 CFR Part 331, 9 CFR Part 121, and 42 CFR Part 73

• Work with these agents require:

• FBI background investigation

• Mental health assessment

• Laboratory certification

• Training certification(s)

• Transfer and shipping documentation

• CDC’s role

• Laboratory Registration and Select Agents Tracking Program

• Designated by the HHShttp://www.selectagents.gov/Select%20Agents%20and%20Toxins%20List.html

Select Agent Viruses• Cercopithecine herpesvirus 1 (Herpes B virus)

• Crimean-Congo haemorrhagic fever virus

• Eastern Equine Encephalitis virus

• Ebola virus

• Lassa fever virus

• Lujo virus

• Marburg virus

• Monkeypox virus

• Reconstructed replication competent forms of the 1918 pandemic influenza virus containing any portion of the coding regions of all eight gene segments (Reconstructed1918 Influenza virus)

• South American Haemorrhagic Fever viruses

• Flexal

• Guanarito

• Junin

• Machupo

• Sabia

• Chapare

• Variola major virus (Smallpox virus)

• Variola minor virus (Alastrim)

• Tick-borne encephalitis complex (flavi) viruses

• Central European Tick-borne encephalitis

• Far Eastern Tick-borne encephalitis

• Kyasanur Forest disease

• Omsk Hemorrhagic Fever

• Russian Spring and Summer encephalitis

• Hendra virusNipah virusRift Valley fever virusVenezuelan Equine Encephalitis virus

USDA Select Agents AND TOXINSAfrican horse sickness virusAfrican swine fever virusAkabane virusAvian influenza virus (highly pathogenic)Bluetongue virus (exotic)Bovine spongiform encephalopathy agentCamel pox virusClassical swine fever virusFoot-and-mouth disease virusGoat pox virusJapanese encephalitis virusLumpy skin disease virusMalignant catarrhal fever virus(Alcelaphine herpesvirus type 1)Menangle virusPeste des petits ruminants virusRinderpest virusSheep pox virusSwine vesicular disease virusVesicular stomatitis virus Indiana subtypes IN2, IN3Virulent Newcastle disease virus 1

Arthropod-Borne Viral Diseases

Chapter 38

Introduction• Arthropod-Borne viruses:

Arboviruses

• Viruses transmitted by arthropods• Mosquitos

• Ticks

• Others

• Hundreds known

• Serious global health problem

• Cause hundreds of millions of infections each year• Millions of deaths per year

• Major impact on economies

• Often follow changes in climate

• Hurricanes/tropical storms

• Global warming

• Heavy Rainfall

Zoonoses

• A zoonotic agent is one that normally persists in animals in a non- or low-pathogenic state, but can cause disease in humans

• In most instances, transmission to humans is incidental

• It is also a dead-end for the virus

• The diseases are termed zoonoses (sing: zoonosis)

• Outbreaks of zoonoses are termed epizootic

• Persistence of a disease agent in a particular environment is termed endemic

• An epidemic of animal infections is termed enzootic

Togaviruses

• Family Togaviridae, genus Alphavirus

• Plus-strand RNA

• Can undergo recombination with other alphaviruses

• More than 30 viruses

• Enveloped

• Notable members

• Venezuelan equine encephalitis virus group

• Eastern equine encephalitis virus group

• Western equine encephalitis virus group

• Chikungunya virus

• O'nyong-nyong virus   

• Ross River virus 

• Semliki forest virus

Flaviviruses

• Family Flaviviridae

• Plus-strand RNA

• Enveloped

• Virus maturation on cytoplasmic membranes

• Dozens of known species

• Notable members

• Dengue virus group

• Japanese encephalitis virus group• JE virus

• West nile virus

• St. Louis encephalitis virus

• Tick-borne encephalitis virus group

• Yellow fever virus group

• Russian Spring-Summer encephalitis virus  

Bunyaviruses• Family Bunyaviridae

• Negative-strand or ambisense RNA

• Tripartite genomes

• Three gene segments

• S - small (nucleocapsid)

• M - medium (glycoproteins G1 and G2)

• L - large (RNA polymerase)

• Enveloped

• Dozens of known species

• Five genera

• Nairovirus

• Orthobunyavirus

• Phlebovirus 

• Hantavirus (rodent-borne)

• Tospovirus (plant viruses)

Bunyaviruses

• Notable members (arthropod-borne)

• Phleboviruses

• Toscana and Tehran viruses (Sandfly fever)

• Punto Toro virus (hemorrhagic fever)

• Rift Valley fever virus (hemorrhagic fever)

• Coltivirus

• Colorado tick fever

• Orthobunyavirus

• La Crosse virus (encephalitis)

Venezuelan Equine Encephalitis • First recognized as South American equine disease (1930s)

• Highly fatal

• Subsequently identified as human disease (1950s)

• Rarely fatal; instances of permanent neurological damage

• Until 1995, sporadic epizootic outbreaks of human and equine cases in SA

• Sometimes hundreds of thousands

• Mid 1990s outbreaks occurred in Central America and Mexico

• Similar alphaviruses in the VEE group were found in Florida (e.g. Everglades virus)

• Ecology

• Endemic vector: Culex species mosquitos

• Amplification hosts: rodents

• Epidemic vectors: Ochlerotatus and Psorophora spp. mosquitos

VEE Phylogenetics

Dengue• Four serotypes: 1-4

• Most important human arboviral pathogen

• About 50 million infections each year

• 2.5 billion people at risk

• Humans and other primates are amplifying hosts

• Endemic in Texas

• Peridomestic vectors

• Aedes aegypti

• Aedes albopictus

• Pathogenesis: Immunopathology

• Infection with first dengue virus results in dengue fever

• Second infection with another serotype can result in dengue hemorrhagic fever

• Inflammatory immune response

• Cytokine storm

Dengue Virus

Phylogenetics

West Nile Fever

• First isolated in the West Nile river district of Uganda (1937)

• Until U. S. outbreak it was an Old World disease

• Introduced to U. S. in 1999

• Most likely from Israel by container ship

• Ecology

• Vector: Culex mosquitos

• Amplifying hosts: birds

• Virus is now endemic in the U. S.

West Nile Fever

• Pathogenesis

• Historically, only known to cause a febrile illness

• 1996 Romanian outbreak resulted in unusually higher mortality and encephalitis

• 1998 Russian outbreak also had high incidence of neurological manifestations

• Arrival in U. S. resulted in tens of thousands of infections• Naive population

• Blood bank studies suggest only 1 in 5 show symptoms

• Molecular mechanisms are largely unknown• Animal studies suggest a chemokine response in the CNS may recruit

inflammatory cells

• CTL infiltrates kill neurons in mice infected with WNV

West Nile Virus

• Clinical outcomes• Completely asymptomatic (80%)

• West Nile fever - headache, confusion, complete recovery

• West Nile meningitis

• meningeal inflammation

• photophobia

• phonophobia

• Kernig sign (inability to straighten leg without pain)

• Brudzinski's sign (lift head and hips and knees flex)

• West Nile encephalitis

• encephalopathy (altered level of consciousness, lethargy, personality change)

• seizures

• CNS inflammation

• West Nile meningoencephalitis

• Acute flaccid paralysis

• May have long-term or indefinite weakness

Yellow Fever• Principally a disease of Africa and

South America

• It is thought that YFV arrived in the Americas during the slave trade

• Infected slaves, who had some genetic resistance, carried the virus, which then entered the local ecosystem after mosquito bites

• Two forms

• Urban Yellow Fever• Mosquito-human transmission cycle

• Aedes aegypti

• Jungle Yellow Fever• Mosquito-primate transmission cycle

with spillover to humans

• Aedes spp. in Africa

• Haemagogus and Sabethes spp. in South America

Yellow Fever Virus

• Genome

• 10.8 kb RNA

• Single ORF of 10.2 kb• Structural proteins

• nucleocapsid (C)

• Premembrane/membrane (prM/M) - involved in membrane fusion

• Envelope (E) - spike protein, HA activity, neutralizing antibody target

• Nonstructural proteins

• NS1 - expressed on cell membranes, including surface; involved in RNA synthesis

• NS2A - Interacts with NS3 and NS5 to regulate viral gene expression

• NS2B - Interacts with NS3 to form protease for viral polypeptide

• NS3

• NS4A - Involved with RNA synthesis

• NS4B - Involved with RNA synthesis

• NS5 - RNA polymerase and methyltransferase for 5’ Met-G cap formation

Yellow Fever• Pathogenesis

• Onset 3-6 days

• Sometimes a brief (48 hr) recovery period occurs, followed by jaundice

• Primary replication in lymph nodes

• Systemic infection• Liver, spleen, kidneys, bone marrow, lymph nodes

• Acute liver failure

• Apoptosis of hepatocytes

• Inflammation

• Immune infiltrates (immunopathology?)

• 10% mortality

• Control

• Virus first isolated in 1928

• YFV 17D live attenuated vaccine strain derived 1937

• 31 amino acid differences between vaccine strain and wild-type

Yellow Fever Vaccine

• Rare adverse events following vaccination

• Recent report of a death (Doblas et al. 2006. J Clin Virol. 36:156)• 26-year old Spanish woman planning to travel to Africa

• Developed yellow fever a few days after vaccination

• Died 10 days after vaccination

• Genome of recovered virus sequenced

• Only two silent mutations were found

• ChimeriVax Yellow Fever Vaccine Backbone

• Proprietary (Acambis, Inc)

• Reverse genetics system of 17D

• Replace E gene with E gene of choice

• Vaccine Candidates• West Nile ChimeriVax candidate is in clinical trials

• JEV Chimerivax

• DENV four serotype Chimerivax