Some Viral Adhesins and Their Host Attachment Sites
Pathogen
Disease
Adhesin
Attachment Site
Influenzavirus
Influenza
Hemagglutinin
Sialic acid of respiratory and intestinal cells
Herpes simplex virus I or II
Oral herpes, genital herpes
Glycoproteins gB, gC, gD
Heparan sulfate on mucosal surfaces of the mouth and genitals
Human immunodeficiency virus
HIV/AIDS
Glycoprotein gp120
CD4 and CCR5 or CXCR4 of immune system cells
Antigenic variation in viruses
Antigenic variation also occurs in certain types of enveloped viruses, including influenza viruses, which exhibit two forms of antigenic variation:
antigenic drift and
antigenic shift (
[link] ). Antigenic drift is the result of point mutations causing slight changes in the spike proteins
hemagglutinin (H) and
neuraminidase (N). On the other hand, antigenic shift is a major change in spike proteins due to gene reassortment. This reassortment for antigenic shift occurs typically when two different influenza viruses infect the same host.
The rate of antigenic variation in influenza viruses is very high, making it difficult for the immune system to recognize the many different strains of Influenzavirus. Although the body may develop immunity to one strain through natural exposure or vaccination, antigenic variation results in the continual emergence of new strains that the immune system will not recognize. This is the main reason that vaccines against Influenzavirus must be given annually. Each year’s
influenza vaccine provides protection against the most prevalent strains for that year, but new or different strains may be more prevalent the following year.
Antigenic drift and antigenic shift in influenza viruses. (a) In antigenic drift, mutations in the genes for the surface proteins neuraminidase and/or hemagglutinin result in small antigenic changes over time. (b) In antigenic shift, simultaneous infection of a cell with two different influenza viruses results in mixing of the genes. The resultant virus possesses a mixture of the proteins of the original viruses. Influenza pandemics can often be traced to antigenic shifts.
Explain the difference between antigenic drift and antigenic shift.
Key concepts and summary
Virulence factors contribute to a pathogen’s ability to cause disease.
Exoenzymes and
toxins allow pathogens to invade host tissue and cause tissue damage. Exoenzymes are classified according to the macromolecule they target and exotoxins are classified based on their mechanism of action.
Bacterial toxins include
endotoxin and
exotoxins . Endotoxin is the lipid A component of the LPS of the gram-negative cell envelope. Exotoxins are proteins secreted mainly by gram-positive bacteria, but also are secreted by gram-negative bacteria.
Bacterial pathogens may evade the host immune response by producing
capsules to avoid phagocytosis, surviving the intracellular environment of phagocytes, degrading antibodies, or through
antigenic variation .
Viral pathogens use adhesins for initiating infections and antigenic variation to avoid immune defenses.
Influenza viruses use both
antigenic drift and
antigenic shift to avoid being recognized by the immune system.
Fill in the blank
The glycoprotein adhesion gp120 on HIV must interact with __________ on some immune cells as the first step in the process of infecting the cell.
Antigenic __________ is the result of reassortment of genes responsible for the production of influenza virus spike proteins between different virus particles while in the same host, whereas antigenic __________ is the result of point mutations in the spike proteins.
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include:
1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Anatomy is the study of the structure of the body, while physiology is the study of the function of the body. Anatomy looks at the body's organs and systems, while physiology looks at how those organs and systems work together to keep the body functioning.
Enzymes are proteins that help speed up chemical reactions in our bodies. Enzymes are essential for digestion, liver function and much more. Too much or too little of a certain enzyme can cause health problems
Kamara
yes
Prince
how does the stomach protect itself from the damaging effects of HCl
the normal temperature is 37°c or 98.6 °Fahrenheit is important for maintaining the homeostasis in the body
the body regular this temperature through the process called thermoregulation which involves brain skin muscle and other organ working together to maintain stable internal temperature
