Lecture 20

Question 1

Question: What causes tinea or ringworm, and what tissues are affected?

Answer 1

Answer: Tinea (or ringworm) is caused by dermatophytes, a group of fungi that infect keratinized tissues such as skin, hair, and nails.

Question 2

Question: Name the different types of tinea and the areas they infect.
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Answer 2

Answer:
Tinea corporis: Body.
Tinea capitis: Scalp and hair.
Tinea pedis: Feet (athlete’s foot).
Tinea cruris: Groin (jock itch).
Tinea unguium: Nails.

Question 3

Question: What are the three main genera of dermatophytes that cause skin infections?

Answer 3

Answer: Trichophyton, Microsporum, and Epidermophyton.

Question 4

Question: What are some of the virulence factors of Trichophyton rubrum?

Answer 4

Answer: Virulence factors include proteases that degrade host proteins, secondary metabolites that suppress the immune system, and LysM proteins that help with fungal adhesion and immune evasion.

Question 5

Question: How are dermatophytes transmitted?

Answer 5

Answer: Dermatophytes are transmitted through direct contact with infected individuals, animals, or contaminated objects like towels and clothing.

Question 6

Question: What are the main treatments for tinea infections?

Answer 6

Answer: Treatment includes topical antifungals like clotrimazole for superficial infections and oral antifungals like terbinafine for more severe or nail infections.

Question 7

Question: How do azole antifungals work?

Answer 7

Answer: Azole antifungals inhibit ergosterol synthesis, disrupting the fungal cell membrane and leading to fungal cell death.
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Question 8

Question: What are some factors that increase susceptibility to dermatophyte infections?

Answer 8

Answer: Factors include high humidity, excessive sweating, diabetes, and obesity.

Question 9

Question: What is the difference between anthropophilic and zoophilic dermatophytes?

Answer 9

Answer: Anthropophilic dermatophytes are adapted to infect humans, causing mild and often chronic infections, while zoophilic dermatophytes are transmitted from animals to humans, causing more acute infections.

Question 10

Question: How does imiquimod work in treating HPV infections?

Answer 10

Answer: Imiquimod activates Toll-like receptor 7 (TLR-7) on immune cells, which boosts the innate immune response, promoting the release of cytokines and recruitment of immune cells to clear HPV-infected cells.

Question 11

Question: Which antibody response is important for HPV immunity?

Answer 11

Answer: The most useful antibody response is IgG, particularly neutralizing antibodies against the L1 protein of HPV, which can prevent the virus from binding to and infecting epithelial cells.
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Question 12

Question: HPV virions are highly stable in the environment—why is this important for the virus?

Answer 12

Answer: The stability of HPV virions allows the virus to persist on surfaces and objects, increasing the likelihood of transmission through skin contact. This stability helps the virus survive outside the host for longer periods, facilitating its spread.

Question 13

Question: If tinea is the most common human infection in the world, why do we know so little about it?

Answer 13

Answer: Tinea infections are often not life-threatening and can be treated effectively with antifungal medications. As a result, research has focused less on understanding the underlying biology of dermatophytes compared to more dangerous pathogens.

Question 14

Question: Why is the L1 protein significant in HPV?

Answer 14

Answer: The L1 protein is the major capsid protein that determines the HPV genotype and is a key target for neutralizing antibodies in HPV vaccines

Question 15

Question: What are the primary ways HPV spreads?

Answer 15

Answer: HPV is transmitted through direct skin contact, sexual intercourse, and contact with contaminated surfaces, such as towels or clothing. Asymptomatic individuals can also shed the virus.

Question 16

Question: What strategies does HPV use to avoid immune detection?

Answer 16

Answer: HPV suppresses interferon (IFN) responses and downregulates MHC class I and II expression in keratinocytes, allowing it to evade immune detection and persist within the epithelium.

Question 17

Question: Why are HeLa cells important in medical research?

Answer 17

Answer: HeLa cells, derived from a patient with cervical cancer caused by HPV18, were the first immortalized human cell line. They have been crucial in cancer research, virology, and vaccine development, including the polio vaccine.

Question 18

Question: What are the different types of warts caused by HPV?

Answer 18

Answer: HPV causes various warts, including common warts, plantar warts, flat warts, and genital warts. Some strains of HPV also lead to precancerous lesions.

Question 19

Question: What are the main treatment options for HPV infections?

Answer 19

Answer: Common treatments include vaccination (e.g., Gardasil), imiquimod, condom use to prevent transmission, surgical removal of warts, and Pap smears for early detection of cervical abnormalities.