Infections and Vaccines Chapter 1

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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 Signup and view all the answers

What is the function of listeriolysin, produced by Listeria?

To punch holes in phagolysosome walls Signup and view all the answers

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

Because herpes virus downregulates MHC expression Signup and view all the answers

What is the main advantage of ISCOMs over conventional vaccines?

They can penetrate cell membranes and deliver antigens to antigen-presenting pathways Signup and view all the answers

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

To prevent intrauterine infection and birth deformities Signup and view all the answers

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

Because measles is a major cause of death in infants Signup and view all the answers

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

They do not elicit antibodies in newborn babies Signup and view all the answers

What is the role of ISCOMs in inducing immunity?

They stimulate T cells, including CTL Signup and view all the answers

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

They vary depending on the local disease burden Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What are antigen vaccines typically made of?

One or more substances contained by the tumor cells Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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

Live attenuated vaccines Signup and view all the answers

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

They may cause serious infections Signup and view all the answers

What is a characteristic of toxoids?

They are components of pathogens that induce predominantly antibody responses Signup and view all the answers

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

It may mutate back to the virulent form Signup and view all the answers

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 Signup and view all the answers

What is a characteristic of killed organism vaccines?

They do not replicate in hosts and cannot enter intracellular antigen presenting pathways Signup and view all the answers

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

To deliver antigens and stimulate an immune response Signup and view all the answers

What is the limitation of viral vectors in vaccine development?

They can only infect a small number of human cells Signup and view all the answers

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

By displaying proteins on their surface that help activate immune cells Signup and view all the answers

What is the challenge in developing cancer vaccines in humans?

Tumors have learned to escape the immune system Signup and view all the answers

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 Signup and view all the answers

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

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