blood clot and invade the host. Staphylococcus aureus makes both coagulase and staphylokinase. They can produce either, depending on the nutrient supply surrounding the bacteria. Antigenic variation can protect a pathogen. The pathogen can alter its extracellular proteins so that the cell is no longer recognized by the immune system. This is what happens with the agents that cause both gonorrhea and Lyme disease. Viruses also have certain virulence factors. There are adhesins also in viruses but they exist on the viral protein coat. These adhesins will facilitate viral adhesion to the host cell. In addition, enveloped viruses will have a great degree of antigenic variation that will prevent an immune response. Influenza virus has a spike protein that will bind to host intestinal and respiratory membrane cells. HIV has a viral adhesin that binds to CD4 helper cells in the immune system. Herpes simplex has certain glycoproteins that bind to genital or oral mucus membranes. There are two types of antigenic variation in viruses. Antigenic drift involves small point mutations that slightly change the spike proteins. Antigenic shift involves a major change in the spike proteins. This is from gene reassortment. Antigenic variation is a major way that viruses change in order to be infective to the host cell. It is the reason why the influenza vaccine is given every year to fight the disease.
VIRULENCE FACTORS FOR EUKARYOTIC PATHOGENS Eukaryotes can also exhibit certain virulence factors. Fungi have some similar virulence factors when compared to bacteria. Candida albicans produces surface glycoproteins that are adhesins, assisting in attachment. There are also exoenzymes like proteases and phospholipases made by the organism. Cryptococcus makes a large capsule that makes it resistant to phagocytosis. Other fungi will make mycotoxin, such as the organisms that make ergot toxin found in certain grain products contaminated with fungi. The toxin will cause gangrene, mania, and sometimes hallucinations. Aspergillus makes aflatoxin as a virulence factor. Aflatoxin
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