PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
I. INTRODUCTION TO VIRUSES
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GENERAL CHARACTERISTICS
Obligatory intracellular parasites
Contain DNA or RNA
No ribosomes
No ATP-generating mechanism
Contain a protein coat
Some viruses are enclosed by an envelope
Some viruses have spikes
Most viruses infect only specific types of cells in one host
Host range is determined by specific host attachment sites
and cellular factors
10/28/2022
John Jeamel Igpuara, SPh
MORPHOLOGY OF VIRUSES
a. Polyhedral virus; “many sides”
Icosahedron; 20 triangular faces, 12 corners
e.g. Mastadenovirus, Poliovirus, Adenovirus
VIRUS SIZES
Covid-19 (SARS-CoV-2) – 60-140 nanometers
Rhinovirus – common cause of colds/flu
b. Enveloped icosahedral virus
e.g. Herpesvirus, Human herpesvirus (HHV)
VIRION STRUCTURE
i.
Nucleic Acid (DNA only / RNA only) NOT BOTH!!
ii.
Capsid; made of capsomeres (protein)
iii.
Envelope (lipids, proteins, carbohydrates)
iv.
Spikes (glycoprotein projection)
Non-enveloped virus = naked virus
o More resistant to changes
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
c. Enveloped helical virus
e.g. Influenzavirus
10/28/2022
John Jeamel Igpuara, SPh
TAXONOMY OF VIRUSES
Family names ends in –viridae
Genus names ends in –virus
Viral species:
o a group of viruses sharing the same genetic
information and ecological niche (host)
o common names are used for species
o subspecies are designated by a number
Example:
Family Herpesviridae
Retroviridae
Genus Herpesvirus
Lentivirus
Human
Human herpesvirus
Species
immunodeficiency virus
HHV-1, HHV-2, HHV-3
HIV-1, HIV-2
d. Helical virus; like long rods, either rigid or flexible
e.g. Ebola virus
e. Complex viruses; polyhedral + helical
e.g Bacteriophage, Orthopoxvirus
II. VIRAL MULTIPLICATION
a. Lytic Cycle
- Bacteriophage causes lysis and death of host cell
- Bacterial cells infected are called lytic cells.
STEPS:
1. Attachment: phage attaches by tail fibers to the host cell
2. Penetration: phage lysozyme opens the cell wall; tail
sheath contracts to force tail core and DNA into the cell
3. Biosynthesis: production of phage DNA and proteins
4. Maturation: assembly of phage particles
5. Release: phage lysozyme breaks the cell wall
Viral
one-step
growth
curve:
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
THE LYTIC CYCLE
10/28/2022
John Jeamel Igpuara, SPh
THE MOVEMENT OF VIRUSES (ENTRY/EXIT)
a. Endocytosis; “engulfing” - Togavirus
b. Fusion; “merging with host” - Herpesvirus
b. Lysogenic Cycle
- These bacteriophages establish a stable, long-term
relationship with their host called lysogeny.
- Bacterial cells infected are called lysogenic cells.
c. Budding; “formation of buds” - Lentivirus
LIFE CYCLE OF VIRUS OTHER THAN PHAGES
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
III. LATENT AND PERSISTENT VIRAL INFECTIONS
a. Latent viral infection
o Virus remains in the asymptomatic host cell for long
periods, sudden manifestation
e.g. Cold sores, shingles (kulebra) caused by varicellazoster virus (also causes chicken pox)
10/28/2022
John Jeamel Igpuara, SPh
3. Papovaviridae
- DSDNA, non-enveloped virus
i. Papillomavirus – Human wart virus
ii. Polyomavirus – causes tumors; some cancer
b. Persistent viral infection
o Disease process occurs over a long period; generally
is fatal
e.g. Subacute sclerosing panencephalitis (measles virus)
IV. VIRUSES AND INFECTIOUS DISEASE
DNA CONTAINING VIRUSES
Non-enveloped
1. Parvoviridae
- SSDNA, non-enveloped virus
i. Fifth disease (Parvovirus B-19) more in kids
Enveloped
4. Poxviridae
- DSDNA, enveloped virus
- Causes puss-filled skin lesions
i. Orthopoxvirus (vaccinia and smallpox viruses)
ii. Molluscipoxvirus
iii. Smallpox
iv. Molluscum contagiosum
v. Cowpox
ii. Anemia in immunocompromised patients
2. Adenoviridae
- DSDNA, non-enveloped virus
i. Respiratory infections in humans
ii. Tumors in animals
iii. Mastadenovirus
Figure 1 Smallpox
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
5. Herpesviridae
- DSDNA, enveloped virus
- Some can remain latent in host cells
i. Simplexvirus (HHV-1, HHV-2); causes cold sores
1. Encephalitis (HHV-1);
2. STD/genital herpes/carcinoma (HHV-2)
10/28/2022
John Jeamel Igpuara, SPh
2. Caliciviridae
- SSRNA, + strand, non-enveloped
i. Hepatitis E virus
o obtained via consumption of eating or
drinking contaminated food or water, handmouth, close contact
ii. Norovirus; causes gastroenteritis
3. Togaviridae
- SSRNA, + strand, enveloped
i. Alphavirus
o Transmitted by arthropods (arbovirus);
o EEE (Eastern Equine Encephalitis) and;
o WEE (Western Equine Encephalitis)
ii.
iii.
iv.
v.
vi.
vii.
Varicellovirus (HHV-3); causes chickenpox (VZV)
Lymphocryptovirus (HHV-4)
Cytomegalovirus (HHV-5); infants
Roseolovirus (HHV-6, HHV-7)
Rhadinovirus (HHV-8); causes Kaposi’s sarcoma
Epstein-Barr virus (EBV); causes mononucleosis
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ii. Rubivirus (rubella virus); causes German measles
6. Hepadnaviridae
- DSDNA, enveloped virus
- Uses reverse transcriptase
i. Hepatitis B virus (HBV)
-common form, obtained via hypodermic
needles, blood transfusion, sex, contaminated
needles/syringes
RNA CONTAINING VIRUSES
Positive (+) sense strand
1. Picornaviridae
- SSRNA, + strand, non-enveloped
i. Enterovirus (Poliovirus and coxsackievirus)
ii. Rhinovirus (major cause of common colds)
iii. Hepatitis A virus (jaundice)
- obtained via fecal-oral route – G.I. (street foods)
4. Flaviviridae
- SSRNA, + strand, enveloped
i. Arboviruses - can replicate in arthropods
o “Arthropod-borne virus” = Arbovirus
o Yellow fever; monkey
o Dengue a.k.a. breakbone fever; Aedes aegypti
o SLE (St. Louis Encephalitis); wild birds/mosquito
o West Nile viruses
ii. Hepatitis C virus
5. Coronaviridae
- SSRNA, + strand, enveloped
- Upper Respiratory Infection (URI/URTI)
i. Coronavirus
ii. SARS, MERS
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
Negative (-) antisense strand
6. Rhabdoviridae
- SSRNA, - strand, one RNA strand
- Cause numerous animal diseases
i. Vesiculovirus
ii. Lyssavirus (rabies virus); dogs
7. Filoviridae
- SSRNA, - strand, one RNA strand
- Enveloped helical viruses; elongated
i. Filovirus
ii. Ebola a.k.a. African Hemmorhagic Fever
iii. Marburg
8. Paramyxoviridae
- SSRNA, - strand, one RNA strand
i. Paramyxovirus
ii. Morbillivirus
iii. Parainflueza
iv. Mumps; Parotitis enlargement of parotid glands
v. Newcastle disease (chickens)
10/28/2022
John Jeamel Igpuara, SPh
10. Orthomyxoviridae
- SSRNA, - strand, multiple RNA strands
- Envelope spikes can agglutinate RBCs
i. Influenzavirus (Influenza viruses A and B)
ii. Influenza C virus
11. Bunyaviridae
- SSRNA, - strand, multiple RNA strands
i. Bunyavirus (California Encephalitis virus)
o 4 types of disease syndrome
a. Fever
b. Encephalitis
c. Hemorrhagic fever
d. Acute Respiratory Illness
ii. Hantavirus
12. Arenaviridae
- SSRNA, - strand, multiple RNA strands
- Helical capsids contain RNA-containing
granules
i. Lymphocytic choriomeningitis
ii. VEE (Venezuelan Equine Encephalitis)
iii. Lassa fever
OTHER RNA VIRUSES
13. Retroviridae
- SSRNA, two RNA strands, produce DNA
- Uses reverse transcriptase to produce
DNA from viral genome
i. Lentivirus (HIV); Kaposi’s sarcoma
ii. Oncogenic viruses
o Includes all RNA tumor viruses
14. Reoviridae
- DSRNA, non-enveloped
i. Reovirus (respiratory enteric orphan)
ii. Rotavirus (mild respiratory
infections and gastroenteritis)
iii. Colorado tick fever
9. Deltaviridae
- SSRNA, - strand, one RNA strand
- Depends on coinfection with
hepadnavirus
i. Hepatitis D virus – can only occur when
with HBV
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PHARMACEUTICAL MICROBIOLOGY AND PARASITOLOGY
Virology
Ms. Pauline Lyzell Francisco, RPh, MSHSA
10/28/2022
John Jeamel Igpuara, SPh
V. VIRUS AND CANCER
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MOLECULAR BIOLOGICAL RESEARCH
Shows that mechanisms of diseases are similar even
when the virus does not cause cancer
PLANT VIRUSES AND VIROIDS
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CANCER
Activated oncogenes transform normal cells into
cancerous cells; indirectly causing cancer
Viruses capable of inducing tumors in animals are
called oncogenic viruses, or oncoviruses
The genetic material of oncogenic viruses becomes
integrated into the host cell’s DNA
ONCOGENIC VIRUSES
Oncogenic DNA viruses
i.
Adenoviridae
ii.
Papovaviridae
iii.
Poxviridae
iv.
Herpesviridae
v.
Hepadnaviridae
Oncogenic RNA viruses
i.
Retroviridae
- Viral RNA is transcribed to DNA which can
integrate into host DNA
ii.
HTLV-1
iii.
HTLV-2
More common oncogenic viruses:
o Human Papillomavirus
o Epstein-Barr virus
o Herpes simplex virus 2
PRIONS
Proteinacious infectious particle
Inherited and transmissible by ingestion, transplant,
and surgical instruments
i. Spongiform encephalitis: sheep scrapie
ii.
iii.
iv.
v.
Creutzfeldt-Jakob disease
Gerstmann-Straussler syndrome
Fatal-familial insomnia
Mad cow disease
 PrPC
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Normal cellular prion protein
On cell surface
(HPV)
(EBV)
(HSV-2)
VI. VIROIDS AND PRIONS
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PLANT VIRUSES AND VIROIDS
Viroids infect:
i. Potatoes; potato spindle tuber disease
 PrPSc
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Scrapie prion protein
Accumulates in brain cells,
forming plaques
ii. Chrysanthemum; stunting their growth
iii. Cucumber; cucumber pale fruit disease
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