PATH 3020E Midterm (from quizlet)

"Virus"

Latin word for poison

Virus replication is

- Dependent on the host's protein synthesizing machinery

- Derived from pools of the required materials rather than from binary fission

- Located at sites not separated from the host cell content by a lipoprotein bilayer membrane

Viruses vary in size from

30 nm to 450 nm

Size of polio virus

30 nm

Size of poxvirus

450 nm

Viruses can be observed only by

electron microscope

Composition of viruses

nucleic acid core and outer protein coat

Nucleic acid core of viruses

DNA or RNA, NOT both

Why classify the virus?

- To describe the characteristics

- To provide an identity (name)

- Additional research and properties can be associated

Group viruses based on similarity

- Structure

- Genomic compositions

- Host

- Biology

ICTV

International Committee on Taxonomy of Viruses

ICTV

- Created in 1966 at the International Congress of Microbiology

Goals of ICTV

- To develop an internationally agreed taxonomy of viruses

- To establish internationally agreed names for virus taxa

- To communicate the decision reached concerning the classification and nomenclature of viruses to virologists by holding meetings and publishing reports

- To maintain an Official Index of agreed names of virus taxa

How many orders in 2018

14

How many families in 2018

143

How many subfamilies in 2018

64

How many genuses in 2018

865

How many species in 2018

4958

Most of the viruses infecting plants are

RNA viruses

Largest by nucleic acid composition. ssRNA (+)

Closteroviridae

The only family that cause disease in both plants and animals. ssRNA (-)

Bunyaviridae

Largest family that causes significant loss to food and fiber crops ssDNA

Geminiviridae

Most members that infect vertebrates are

RNA viruses

HIV is caused by

ssRNA (RT) Retroviridae

Influenza is caused by

ssRNA (-) Orthomyxoviridae

Polio is caused by

ssRNA (+) Picronaviridae

Rabies is caused by

ssRNA (-) Rhabdoviridae

West Nile fever is caused by

ssRNA (+) Flaviviridae

TMV

Tobacco mosaic virus

TMV milestones

First:

- Infectious nucleic acid

- Local lesion assay for a plant virus

- Protoplast infection system for a plant virus

- Identification of viral gene for cell-to-cell movement of viral RNA in plants

- RNA virus shown to disassemble co-translationally in vitro and in vivo

- Plant gene for virus resistance cloned (N gene)

West Nile Virus is a

mosquito-borne disease

First case of WNV

Uganda in 1937

WNV family

Flaviviridae

WNV genus

Flavivirus

WNV virions

spherical in shape

WNV virion size

50 nm in diameter

WNV is a

single strand RNA molecule

WNV encodes

polyprotein that is processed to give 10 viral proteins

WNV symptomatology

- No symptoms in most of the patients

Febrile illness - 1 in 5 patients develop fever with other symptoms

- Headache

- Body aches

- Joint pain

- Vomiting

- Diarrhea

- Rash

Do most patients recover from WNV?

Yes

1 in 150 patients develop severe illness affecting central nervous system

- High fever

- Headache

- Neck stiffness

- Stupor

- Disorientation

- Coma

- Tremors

- Convulsions

- Muscle weakness

- Vision loss

- Numbness

- Paralysis

People with certain medical conditions such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants are

also at a greater risk

Recovery from severe illness might take

several weeks or months

Some effects to the central nervous system

might be permanent

About how many people who develop severe illness affecting the central nervous system die?

1 out of 10

Detection of the WNV or its genetic materials in serum or cerebrospinal fluid done by

serological, virological, molecular

Serological

Enzyme linked immunosorbent assay (ELISA)

Virological

virus isolation

Molecular

- Reverse transcriptase Polymerase chain reaction (RT-PCR)

- Quantitative PCR (qPCR or Real-time PCR)

Treatment and prevention of WNV

- No vaccines are available

- Supportive clinical management

- Close monitoring for symptom development

- Mosquito control program

Other animals affected by WNV

horse, rodents, lemurs, sheep, camels, cows, dogs, frogs, alligators, crocodiles

Horses

could die due to nervous system infections

Rodents

laboratory mice and hamsters are highly susceptible

Lemurs

capable of maintaining virus in local circulation

Sheep

could cause miscarriage

What animals are resistant to WNV?

guinea pigs, rabbits, and adult rats

What acts as reservoirs for WNV?

birds

What virus is transmitted by birds and pigs?

Nipah virus

NiV

Nipah virus

NiV family

Paramyxoviridae

NiV genus

Henipavirus

Size of NiV

40 to 600 nm in diameter

What type of virus is NiV?

single stranded negative-sense RNA

NiV kb in length

18.3

NiV encodes

6 structural proteins

Where was NiV initially identified?

Sungai Nipah village in Malaysia when a pig farmer was diagnosed with encephalitis

In 1999, how many humans were infected with NiV?

300 with more than 100 deaths

In 2001, different strains of NiV were found in

Bangladesh

In 2001, person-to-person transmission was reported in

India

Transmission of NiV

direct contact with infected bats, infected pigs, other NiV infected people

Signs and symptoms of NiV

- Fever and headache for one-two weeks

- Drowsiness, disorientation, and mental confusion

- May progress to coma within 24-48 hours

- Latent infections with subsequent reactivation of Nipah virus and death have also been reported months and even years after exposure

Diagnosis of NiV

- Molecular: RT-PCR (throat and nasal swabs, cerebrospinal fluids, urine and blood) in early stage

- Serological: ELISA (in later stage)

- Autopsy: in fatal cases

Treatment of NiV

limited to supportive care

Virus transmitted by pets

rabies

Rabies family

Rhabdoviridae

Rabies genus

Lyssavirus

Rabies virion shape

bullet

Rabies size

180 nm long and 75 nm wide

Rabies type

non-segmented, negative strand RNA

Transmission/exposure of rabies

- Bite of a rabid animal

- Infectious material from rabid animals gets into eyes, nose, mouth, or wound

- Inhalation of aerosolized rabies virus

- Patting a rabid animal or contact with blood, urine, or feces of rabid animal

Symptoms of rabies

- Similar to flu: weakness, fever, headache

- Symptoms could last for days

- Discomfort/itching at the site of bite

- Cerebral dysfunction, anxiety, confusion, agitation

- Abnormal behavior, hallucination, and insomnia

Once clinical signs of rabies appear

the disease is nearly fatal and survival is rare

Disease prevention of rabies includes

administration of both passive antibody through an injection of human immune globulin and a round of injections with rabies vaccine

Diagnosis of rabies

- In humans, no single test is sufficient

- RT-PCR for the presence of virus in saliva

- Serum and spinal fluid are tested for antibodies to rabies virus

- Skin biopsy for rabies antigen in the cutaneous nerves at the base of hair follicles

Prevention of rabies

- Vaccinate your pet

- Maintain control of your pets to reduce their exposure to wildlife

- Spay or neuter to decrease the number of stray animals

- Report any stray or ill animals to animal control

What is a vaccine?

A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters

How do vaccines work?

Virus/bacteria enters body => lymphocytes (immune cells) produce antibodies (protein molecules) => antibodies fight antigens (invaders)

Vaccines work by training the immune system to recognize and combat pathogens

- Part of pathogen is introduced to body

- Vaccines are prepared from same pathogens that causes the disease

- Vaccines contain weakened or killed germs and introduced usually by injection

- Immune system reacts to vaccine in a similar way that it would if it were being invaded by the disease—by making antibodies

- The antibodies destroy the vaccine pathogen just as they would the disease germs—like a training exercise

- Then they stay in the body giving it immunity

Live virus vaccines

use the weakened (attenuated) form of the virus

Examples of live virus vaccines

measles, mumps, and rubella (MMR) vaccine and the varicella (chickenpox) vaccine

Killed (inactivated) vaccines

are made from a protein or other small piece taken from a virus or bacteria

Examples of killed vaccines

whooping cough (pertussis) vaccine

Toxoid vaccines

contain a toxin or chemical made by the bacteria or virus; they make you immune to the harmful effects of the infection, instead of the infection itself.

Examples of toxoid vaccines

diphtheria and tetanus vaccines

Biosynthetic vaccines

contain manmade substances that are very similar to pieces of the virus or bacteria

Examples of biosynthetic vaccines

Hepatitis B vaccine

List of classifications in order

domain, kingdom, phylum, class, order, family, genus, species

Tospoviridae order

Bunyavirales

Bunyavirales

- 12 families

- 11 out of the 12 include animal and human viruses transmitted by mosquitoes and ticks

- 1 family is a plant virus transmitted by thrips