Lecture 12 Outline
Eradicating small pox and polio (vaccines)
Space-filling diagram of an Antibody
A polio victim in an iron lung
The Lock and Key Model of Cellular recognition
Lymphocytes
the displayed antigens on the macrophage surface are detected by T-cells, or helper cells
these T-cells are lymphocytes that help to spread the word of the invasion
the T-cells release signals that alert other lymphocytes, the B cells
the T-cells also help the B cells learn the identity of the invader by showing them the antigen
the B lymphocytes become activated and can take one of three paths
some lymphocytes will become killer cells
the killer cells are like the infantry in the battle; they swarm and phagocytize the invaders or kill them using chemical means
some lymphocytes will become antibody (Ab) producing cells
these cells are like the artillery units, producing antibodies that help destroy the invaders
some lymphocytes will become memory cells
these cells will remember what the antigen looked like for a long period of time, sometimes decades
thus, when the body is attacked by the same type of invader (gets exposed to measles again) lymphocytes can be instantly activated and the body's defenses came attack before the invader has chance to establish a foothold
Vaccines
vaccines work by exposing the body to specific antigens without causing disease
thus a killed virus is injected into the animal and this killed virus still contains the viral antigens
the process of phagocytosis by macrophages, display of the antigen, and activation of B lymphocytes occurs
Ab titers (the concentration and amount of Ab) increases
more importantly, memory cells are created that remember the antigen and provide the vaccinated individual with future immunity to the virus
There are several classes of vaccines:
attenuated whole vaccines - these contain living (viable) virus particles that have been weakened by mutation or chemicals so that they no longer cause disease
killed whole vaccines - these vaccines contain killed virus or bacterial particles
toxoid vaccines - some pathogenic organisms produce toxins which are the harmful component. toxoids are modified toxins that no longer cause disease
subunit vaccines - these contain only a portion of the virus or bacterium. often this is only the antigenic protein. often these are produced through genetic engineering
Common vaccines
MMR - mumps, measles, rubella. attenuated whole vaccines.
measles is still a major killer in the developing world, nearly a million deaths a year
DTP - diphtheria, tetanus, pertusis (whooping cough) - the DT are toxoids, pertusis is generally a subunit vaccine
HBV - hepatitis B - a subunit vaccine. relatively new. given to newborns to protect against possible infection by exposure to mother's blood during childbirth.
Polio - two forms: OPV (oral polio vaccine) an attenuated live virus created by Sabin and IPV (injected polio vaccine) an killed virus vaccine created by Jonas Salk.
polio was a major threat in the US until the 1950's. In less than 1% of cases it causes paralysis.
Chicken Pox - a new vaccine only approved a few years ago
Hib - Hemophilus influenza B, a dangerous form of the flu
Eradication of smallpox and polio
smallpox was a deadly childhood (and adult) disease that was fatal in 50% of cases
the smallpox vaccine was invented by Jenner about 200 years ago
Jenner found that by injecting pus from cowpox pustules immunity could be conferred for smallpox
today's vaccine is made from another pox called vaccinia, but the idea is the same
expose a person to something very similar to smallpox, but that doesn't cause disease
the antigens in cowpox are similar enough to those in smallpox that the individual exposed to cowpox is immune to smallpox
worldwide vaccination programs have eliminated smallpox in the human population
since no animal reservoir exists, eliminating smallpox from humans, eradicates it from the world
the last case of wild smallpox was a man (Ali Maow Maalin) from Somalia who contracted the disease in 1977 and lived
in 1980, the disease was considered eradicated and vaccination was discontinued
small stocks of smallpox still exist in Center for Disease Control's vaults and in Russia
smallpox may also be found in unearthed frozen human remains or in mummies
since the population is no longer vaccinated, it is at risk should the smallpox virus reach the general population
polio is also nearly eradicated
again a concerted vaccination program is limiting the disease
again since no animal reservoir exists, once the disease is eliminated in the human population, the disease is eradicated from the face of the earth
good riddance!
