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Virology Lectures > Sexual transmission of HIV > Flashcards

Sexual transmission of HIV Flashcards

1
Q

Routes of HIV transmission

A
  • heterosexual intercourse
  • MSM
  • vertical
  • injection drug use
  • needle-stick injury
  • blood transfusions
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2
Q

Population most at risk of HIV acquisition

A
  • women aged 25-29
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3
Q

When does peak of HIV infection in men occur?

A

30-34 years

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4
Q

4 regions of the FGT

A
  • keratinised stratified squamous epitheliam (opening)
  • vaginal mucosa
  • external region of the cervix (ectocervix)
  • endocervix
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5
Q

Components of the transformation zone

A
  • ectocervix (stratified squamous epithelium)

- endocervix (single layer of columnar epithelial cells)

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6
Q

Structure of lymphoid aggregates in the endometrium

A
  • B cell core
  • surrounded by memory CD8 T cells
  • encapsulated by macrophages
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7
Q

HIV target cells

A
  • CD4+ T cells
  • DCs
  • macrophages
  • Langerhans cells
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8
Q

HIV binding sequence

A
  • CD4 attachment
  • Co-receptor binding
  • virus-cell fusion
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9
Q

Role of Langerhans cells as HIV target cells

A
  • internalize R5 strains
  • transfer virus to CD4 T cells
  • also bind C-type lectin receptor (Langerin)
  • may result in virus endocytosis and degradation
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10
Q

Role of DCs as HIV target cells

A
  • express C-type lectin receptors (DC-SIGN) which may capture HIV
  • HIV endocytoised or transferred to CD4 and CCR5 receptors on DCs
  • viral-cell membrane fusion and infection
  • endocytosed HIV degraded/transferred to CD4 T cells or macs
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11
Q

Immune barriers in the FGT

A
  • epithelial layer
  • antimicrobial peptides
  • immune cells
  • lactobacillus
  • mucus
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12
Q

How could the epithelial barrier be protective?

A

Multiple layers of squamous cells and continuous sloughing off of the superficial layer

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13
Q

Characteristics of mucus

A

Negatively charged high-molecular weight glycoproteins = mucins

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14
Q

Antimicrobial proteins released by epithelial cells in the FGT

A
  • defensins
  • interferons
  • SLPI
  • lactorferrin
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15
Q

How do lactobacilli protect the vagina?

A
  • directly inhibit HIV
  • compete for receptor sites
  • inhibit pathogens
  • capture the virus through lectin molecules
  • regulate immune response during health and disease
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16
Q

How does HIV cross the epithelial barrier?

A
  • disruption of the mucosae
  • columnar epithelial cells endocytose cell-free and cell-associated virus + transcytose to LP
  • DCs extend processes between epi cells + capture virus
17
Q

Factors that increase susceptibility to HIV

A
  • BV/STIs/parasites
  • menstrual cycle phase
  • injectable hormone contraceptive use
  • douching
  • sexual activity
  • ectopy
18
Q

Role of inflammatory cytokines in HIV

A
  • recruit/activate/differentiate HIV target cells
  • induce NF-kB (binds to HIV long terminal repeat and directly promotes transcription)
  • disrupts epi cell tight junctions
19
Q

What phase of the menstrual cycle is the “window of vulnerability”?

A
  • secretory/luteal phase
20
Q

Why are women more susceptible to HIV in the luteal phase?

A
  • cell-cell adhesion proteins and antiproteases are reduced
  • leukocyte recruitment elevated
  • extravasation proteins elevated
21
Q

Possible mechanisms for increased HIV risk with progestin-based injectable use

A
  • increased or decreased cytokines
  • thinning of epithelial barrier
  • increased or decreased HIV target cells
  • altered immune cell activation
  • changes in mucus
  • decreased lactobacilli
  • increased HIV uptake and transcytosis
22
Q

Epithelium of urethra of males

A

pseudostratified columnar epithelium

23
Q

Immune defense mechanisms in the MGT

A
  • PRRs
  • antimicrobial proteins
  • mucus
  • plasma cells in urethra
  • NK cells in mucosa of urethra
  • T cells abundant
24
Q

How may seminal plasma suppress mucosal transmission of HIV?

A
  • contains cationic polypeptides and ROS (antiviral)
  • blocks HIV attachment to DC-SIGN
  • decreases cell surface expression of CD4 and CXCR4
  • increasing FGT epithelial monolayer integrity
25
Q

How may seminal plasma enhance HIV transmission?

A
  • increases vaginal pH
  • heparan sulphate binds HIV and transmits virus to DCs
  • complement activation augments HIV infection
  • induces secretion of pro-inflam cytokines and chemokines

Virology Lectures (13 decks)

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