Infections and Vaccines Chapter 1

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29 Questions

What characteristic of small RNA viruses helps them evade the immune response?

Their tendency to mutate, leading to changes in antigenic proteins

How do some DNA viruses evade the adaptive immune response?

By downregulating MHC expression

What is the function of the polysaccharide capsule produced by Pneumococcus and Haemophilus sp.?

To evade the innate response

What is the function of the waxy coat of Mycobacteria, such as M.tuberculosis?

To inhibit the effects of phagocyte enzymes

What is the function of listeriolysin, produced by Listeria?

To punch holes in phagolysosome walls

Why are natural killer (NK) cells required for the control of herpes virus?

Because herpes virus downregulates MHC expression

What is the main advantage of ISCOMs over conventional vaccines?

They can penetrate cell membranes and deliver antigens to antigen-presenting pathways

What is the primary reason for giving rubella vaccine after puberty?

To prevent intrauterine infection and birth deformities

Why is the measles vaccine given as early as possible in the developing world?

Because measles is a major cause of death in infants

What is the limitation of polysaccharide-based conjugate vaccines in newborn babies?

They do not elicit antibodies in newborn babies

What is the role of ISCOMs in inducing immunity?

They stimulate T cells, including CTL

What is the significance of vaccine schedules in different parts of the world?

They vary depending on the local disease burden

What is the primary goal of injecting whole tumor cells into a person?

To generate an immune response against the antigens on the tumor cells

What is the main difference between an autologous whole cell vaccine and an allogenic whole cell vaccine?

The source of the tumor cells used to make the vaccine

What are antigen vaccines typically made of?

One or more substances contained by the tumor cells

What is a characteristic of antigens found in tumors?

Some are common to all cancers of a particular type, and some are unique to an individual

What is one way to deliver antigens as a vaccine, according to the text?

By giving proteins or pieces of protein from the tumor cells

What is a potential advantage of using genetic material coding for proteins as a vaccine?

It is a way to deliver antigens as a vaccine

What type of vaccine tends to elicit a stronger immune response compared to killed vaccines?

Live attenuated vaccines

What is a potential risk associated with live attenuated vaccines in immunodeficiency patients?

They may cause serious infections

What is a characteristic of toxoids?

They are components of pathogens that induce predominantly antibody responses

What is a concern with the use of attenuated polio vaccine?

It may mutate back to the virulent form

Why has the USA started to use killed polio vaccine again?

Due to the risk of mutation of the attenuated vaccine to the virulent form

What is a characteristic of killed organism vaccines?

They do not replicate in hosts and cannot enter intracellular antigen presenting pathways

What is the primary function of viral vectors in vaccine development?

To deliver antigens and stimulate an immune response

What is the limitation of viral vectors in vaccine development?

They can only infect a small number of human cells

How can viral vectors be engineered to enhance the immune response?

By displaying proteins on their surface that help activate immune cells

What is the challenge in developing cancer vaccines in humans?

Tumors have learned to escape the immune system

What is the difference in the response to cancer vaccines between laboratory animals and humans?

Cancer vaccines can cause tumors to withdraw in laboratory animals but not in humans

Study Notes

Organisms Evading the Immune Response

  • Small RNA viruses (e.g., influenza and HIV) have small genomes, but their RNA genome tends to mutate, changing antigenic proteins continually, evading immunologic memory
  • DNA viruses (e.g., herpes virus family) can evade the adaptive immune response by downregulating MHC expression, requiring the innate response (NK cells) for control

Bacterial Pathogens Evading the Immune Response

  • Extracellular bacteria (e.g., Pneumococcus and Haemophilus sp.) evade the innate response (opsonization by complement and phagocytosis) by producing a polysaccharide capsule, becoming successful pathogens of the respiratory tract
  • Intracellular bacteria (e.g., Mycobacteria, such as M. tuberculosis) evade the immune response with waxy coats that block phagocyte enzymes and secreting catalase, inhibiting the effects of the respiratory burst
  • Listeria causes meningitis, particularly in pregnant women, by secreting listeriolysin, which punches holes in phagolysosome walls

Vaccine Strategies

  • Immunostimulatory complexes (ISCOMs) promote CTL responses, delivering antigen to antigen-presenting pathways, and stimulating T cells, including CTL
  • ISCOMs can be used for mucosal vaccines (e.g., through the nose), inducing widespread mucosal immunity in the gut and respiratory tract

Vaccine Schedules

  • Vaccine schedules consider the clinical implications of each type of infection (e.g., rubella vaccine is given after puberty to prevent intrauterine infection)
  • Schedules vary globally, with measles vaccine given early in developing countries due to high infant mortality rates

Types of Vaccines

  • Cancer vaccines can be made from whole tumor cells or substances (antigens) contained by the tumor
  • Whole cell cancer vaccines can be autologous (made with one's own tumor cells) or allogenic (made with someone else's tumor cells)
  • Antigen vaccines contain one or more substances (antigens) from the tumor cells
  • Antigen delivery mechanisms include direct protein administration, genetic material coding for proteins, and live vaccines

Vaccine Delivery Mechanisms

  • Killed organisms (viruses or bacteria) are generally not as effective as live vaccines but are theoretically safer
  • Subunit vaccines (toxoids, recombinant, polysaccharides, and DNA) induce antibody responses and can be prepared using recombinant technology
  • Viral vectors can be engineered to deliver antigens and help activate immune cells

This quiz covers how organisms evade the immune response, including viruses such as influenza and HIV. Learn about the mechanisms that allow them to mutate and evade immunologic memory.

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