Lecture 2- Viruses And Protozoa

Question 1

Attachment

Answer 1

Attachment, penetration, synthesis + release= stages of a viral infection
Attachment=
-viral proteins on the capsid or envelope bind to specific protein receptors; cell surface receptors facilitate viral entry
-receptors have other cellular functions; exploited by the virus and viral receptors bind to carbohydrate components

Question 2

Specificity

Answer 2

-some viruses are highly host specific; small pox virus and human specialist
-influenza A; wide range of mammals and birds
-specificity it’s important in the case of immunisation

Question 3

Synthesis

Answer 3

-synthesis of viral proteins in cytoplasm
-replication of viral genome; DNA viruses typically replicate in nucleus, RNA viruses replicate in cytoplasm
-assembly of progeny virus particles

Question 4

Release/Exit

Answer 4

*lysis
-naked viruses and pox viruses leave cell by rupturing the cell membrane
-usually results in death of the host cell

*budding
-enveloped viruses, envelope contains host lipids and carbohydrates
-host cell does may not die

Question 5

Viral diseases

Answer 5

2 aspects
1. Transmission - host to host transport
2. Symptoms- cellular impacts

Question 6

Symptom generation

Answer 6

-cell destruction
-changes to gene expression
-immune response degradation

Question 7

Infection

Answer 7

-through a break in the mucous membranes; mouth or throat, cold sores
-via the eye/genitals= genital herpes
-directly via minor abrasions in the skin; herpes whitlow, herpes gladiatorum

Question 8

Reactivation and latency + symptoms

Answer 8

-when latent viral DNA is not integrated into host genome= limited expression of viral genes
-reactivation due to= physical (e.g. injury UV light, hormones)
-psychological (e.g. stress, emotional upset)

Symptoms:
-fluid filled vesicles
-more dangerous in the immunocompromised

Question 9

Poxviridae

Answer 9

-causes diseases in vertebrates and invertebrates
-smallpox; large complex virus
-cowpox
-monkeypox

Question 10

RNA viruses

Answer 10

• Poliovirus
• Norovirus
• Influenza
• Rotavirus
• Hantavirus
• Ebola
• Coronaviruses (CoVs)

Question 11

Poliovirus and Poliomyelitis

Answer 11

Poliovirus= enterovirus
- + stranded RNA virus
-naked
-immunisation
-WHO eradication programme

Poliomyelitis= poliovirus- transmitted by ingestion
Initial symptoms= sore throat and nausea
-viremia may occur; if persistent —> enters the CNS = destruction of motor cells and paralysis occurs
Prevention= vaccination

Question 12

Retrovirus

Answer 12

-DNA becomes integrated into the host chromosome
-retrovirus DNA = transcribed to yield mRNA
-may retain in a latent state within the cells; provirus

Question 13

Problems with antivirals

Answer 13

-identification of virus-specific target
-generation of resistant variants

Question 14

Protozoa;
Parasite vs Pathogen

Answer 14

Not always clear if Protozoa are parasites or pathogens
-insect transmitted = more likely parasites
(Systemic long-term infections, intracellular phase + hard to treat)
-pathogens= often faecal oral transmitte (shorter term diseases)

Question 15

Faecal oral transmission

Answer 15

-giardia= found in intestinal tracts of animals + environment
-amoebic dysentery
-cryptosporidium

Question 16

Acanthamoeba and Naegleria

Answer 16

Acanthamoeba sp
= damages cornea and can cause fatal encephalitis

Question 17

Trichomonas vaginalis

Answer 17

-most common protozoan causing human disease
-lives in the genitourinary system of men + women
-transmitted almost exclusively via sex
-infection in women = vaginitis
-infection in men= asymptomatic

Question 18

Toxoplasma

Answer 18

T.gondii = causative agent of toxoplasmosis
-widely distributed parasites
-wild + domestic mammals and birds are major reservoir
-infection due to= consumption of undercooked meat containing the parasite + ingestion/inhalation of contaminated soil
-protozoan can cross the placenta + infection the foetus

Question 19

Toxoplasma gondii

Answer 19

-most infections = asymptomatic
-toxoplasmosis = only in small number of people; fever-producing illness combined with other symptoms + self-limited infection
-toxoplasmosis= more severe in AIDS patients + foetus

Question 20

Trypanosoma Cruzi

Answer 20

-causes Chagas’ disease
-endemic in central+ South America
-opossums + armadillos = primary reservoir
-transmission = bite of insects in genus triatoma
- “kissing bugs” = feed preferentially from blood vessels in the lip
-parasite-induced heart disease = cause of death in Latin America

Question 21

Trypanosoma brucie

Answer 21

Trypanosoma brucei
• Causes African sleeping sickness
• The insect vector is the tsetse fly
• Three stages;
• Site of the fly bite becomes a lesion with dead tissue
• Fever, lymph node swelling, and headaches
• Meningoencephalitis
• Infections characterized by cyclical waves of infection
• Clearing tsetse fly habitats reduce the cases of disease

Question 22

Leishmania

Answer 22

-causes leishmaniasis
-endemic in parts of the tropical and subtropics
-common hosts =wild +domestic dogs and small rodents
-transmitted by= sand flies

Question 23

Plasmodium

Answer 23

-causative agent of malaria
-4 species cause malaria= p.falciparum, p.vivax, p.ovale and p.malariae
-malaria= endemic throughout the tropics + subtropics
-mosquitos= vector
-3 prominent stages

Question 24

Malaria vaccine

Answer 24

2 vaccines = target the first stage of the parasites lifecycle before it gets to the liver
-built using= proteins from the malaria