Exam 3 Chapter 17a STDs and AIDS

Sites of HIV infection

-HIV can infect any cell that has a CD4 receptor -the most important of these cells is the helper T cell, which turns on the entire immune response -HIV can also infect the brain killing nervous cells -dimension

AIDS

-acquired immune deficiency symdrome -has left its mark on medicine, science, law, economic and education -name of the condition is apt, because the symptoms are those associated with a damaged immune system -unlike many other immune deficiencies, however, AIDS is not inherited but acquired

Early Immune Failure

-as T cell numbers continue their gradual decline, the body becomes increasingly vulnerable to infection -early signs of immune failure include thrush (a fungal infection in the mouth) and shingles (a painful rash caused by the same virus that causes chicken pox)

Replication of HIV

-binds to an uninfected cell when the spherical region at the end of a protein spike fits into a receptor on the host cell surface like a key in a lock -host cell receptor is a surface protein called CD4 -helper t cells are the predominant cell types with these CD4 receptors and are therefore the most common targets of HIV -once within the host cell, the RNA of HIV undergoes a process called reverse transcription -the viral RNA is rewritten as double-stranded DNA -going from RNA to DNA is the reverse of the usual genetic information transfer -viruses that work this way are known as retroviruses -backward copying of genetic information from RNA to DNA is performed by an enzyme called reverse transcriptase, which is inserted into the host cell along with viral RNA

Genital Herpes

-caused by herpes simplex viruses (HSVs)

Variety of other approaches to combating an HIV infection are under active investigation

-clearly the best way to fight HIV is to prevent it from establishing the initial infection -currently the best way to do this is to avoid high-risk behaviors -developing a vaccine similar to those for other viral infections such as smallpox and measles

Treatments

-death in a person with AIDS is usually caused by one of the opportunistic infections -treating opportunistic infections or preventing their onset can improve the quality of life and extend the length of life for people with AIDS -treatment for HIV infection is also aimed at slowing the progress of the infection both before and after the diagnosis of AIDS -current strategy is to slow the rate at which HIV can make new copies of itself -5 classes of drugs that slow viral replication: reverse transcriptase inhibitors, protease inhibitors, fusion inhibitors, HIV entry inhibitors, and inhibitors of HIV DNA integration into the host cell chromosome -original class of antiviral drugs used to slow the progression of an HIV infection consisted of drugs that act on reverse transcriptase -the reverse transciptase is the enzyme necessary for converting the RNA of HIV to DNA that can then be inserted into the DNA of the host cell chromosome

highly active antiretroviral therapy

-drug cocktail, consists of combinations of drugs from at least two classes of antiretrovial drugs -combination of drugs will minimize the development of drug resistance -HAART can reduce the viral load to undetectable levels, but the treatment is not a cure -if treatment is stopped, HIV can leave the latent state and begin actively replicating again

Transmission of HIV

-found in bodily fluids- blood, semen, vaginal secretions, breast milk, saliva, tears, urine, cerebrospinal fluid, and amniotic fluid -not easily transmitted -can't be transmitted by casual contact major modes of transmission: unprotected sexual activity, intravenous drug use, infected mother to offspring before, during, and after birth

Newer classes of antiviral drugs

-fusion inhibitors block the proteins on the surface of HIV that bind to the CD4 receptor on host cells thereby blocking HIV from entering the host cell -integrase inhibitors prevent HIV DNA from inserting itself into the host chromosome

Vaccines

-gardasil and cervarix, they are effective against several types of HPV, including two strains that are responsible for most cases of cervical cancer

Genital Warts

-may be caused by any of several human papillomaviruses (HPVs), they are not the same viruses that cause warts on the hands and feet -HPV is the most common of the viral STDs

Stages of HIV infection

-the initial infection, an asymptomatic stage, initial disease symptoms, early immune failure, and AIDS -usually monitored by following both the decline in the number of helper t cells and the increase in viral load (the number of HIV free in the blood)

characteristics of HIV that have thwarted efforts to develop a vaccine

-the mutation rate in HIV is very high, especially for the proteins in its outer coat, which are the proteins that an antibody would have to recognize -there are 2 types of HIV and many strains of each type. antibodies would have to recognize the exact strain entering the body -the HIV infection is latent when its genetic material has become incorporated into the host DNA. antibodies cannot attak the virus while it is hidden within the host cell -HIV can pass directly from the interior of an interior of an infected cell to the interior of an adjacent uninfected cell. antibodies can attack viruses outside the cell only, they cannot prevent the virus from spreading by this means of transmission

most common symptoms of chlamydia or gonorrhea are....

-those of urinary tract infection -inflammation of the urethra causes a burning sensation during urination, itching or burning around the opening of the urethra, and a discharge from the urethra

AIDS: final step

-time from HIV to AIDS can be 10 years or more depending on the number of other infections the person is exposed to and the health of the immune system before infection with HIV -diagnosis of AIDS is made when an HIV-positive person develops one of the following conditions 1) a helper t cell count 200 cells per mm^3 of blood 2) one of 26 opportunistic infections, the most common of which are Pneumocytis jiroveci pneumonia and kaposi's sarcoma, a cancer of connective tissue that primarily affects the skin 3) a greater than 10% loss of body weight 4) dementia

Global Pandemic

-toward the end of 2010 an estimated 34 million people globally were living with an HIV infection

Initial Infection

-virus actively replicates and the circulating level of HIV rises -the body's immune system produces antibodies against the virus in an attempt to eliminate it -many people have no symptoms when they first become infected, others experience some mild disease symptoms during the initial infection -particularly dangerous stage because even though many people are unaware they are infected at this point, they are particularly contagious

Three stages of syphilis

1) painless bump, called a chancre, that forms at the site of contact, usually the genitals. normally appears within 2 to 8 weeks of the initial contact as a hard, reddish brown bump with raised edges that make it resemble a crater. not always noticed, lasts for one to a few weeks. it ulcerates, becomes crusty, and disappears. during this PRIMARY stage, syphilis is diagnosed by identifying the bacterium in the discharge from a chancre 2) reddish brown rash covering the entire body, including the palms of the hands and soles of the feet. usually appears within a few weeks to a few months after the disappearance of the chancre. doesn't hurt or itch, each bump eventually breaks open and oozes/becomes crusty. ooze contains bacteria. in this stage, diagnosed by a blood test to detect antibodies for treponema bacteria. can be cured with antibiotics such as penicillin, but it becomes difficult to treat as it progresses 3) lesions called gummas appear on the skin or certain internal organs. they often form on the aorta, so the artery wall is weakened and may burst causing the person to bleed to death internally. bacteria can also infect the nervous system damaging the brain and spinal cord. in this stage it is difficult to treat and requires massive amounts of antibiotics over a prolonged period. damage already done can't be prepared ***look at table on page 365 that summarizes all of them

Genital Herpes Type 1

HSV-1 -most commonly found above the waist, where it causes fever blisters or cold sores -as a result of oral-genital sex with an infected person, however, HSV-1 can cause sores on the genitals and HSV-2 can cause cold sores

Genital herpes is most contagious when

active sores are present

Several changes in HIV drug treatment...

are prolonging lives -treatment regimens may be as simple as one pill a day nad newer antiretroviral drugs have fewer side effects, which increase the likelihood that a person will adhere to the treatment regimen -treatment can be started earlier to reduce initial damage to the immune system

First hints of genital herpes

begin about 2 to 20 days after the initial contact -soon blisters appear, accompanied by local swelling, itching, and possibly burning, especially if the blisters get wet during urination

STDs Caused by Viruses

can't be cured with antibiotics, one can treat the symptoms but one can never be certain that the virus has been eliminated

Other strains of HPV

cause high-risk genital infections, which can persist for long periods of time and are closely linked to both cervical cancer in women and penile cancer in men -HPV is thought to be responsible for one-third of all cases of penile cancers in the US and it can be isolated in 90% of women with cervical cancer

Chlamydia trachomatis

caused by a very small bacterium, which cannot grow outside a human cell

females

chlamydia and gonorrhea are more likely to affect the pelvic organs than the urethra, because the vagina and cervix are a woman's primary sites of contact during sexual intimacy

Most people with herpes apparently never

develop symptoms

Initial disease symptoms

eventually, the immune system begins to falter as the virus gains the upper hadn -initial disease symptoms fall into three classes 1) wasting syndrome- otherwise unexplained loss in body weight of more than 10% often accompanied by diarrhea- weight loss similar to cnacer 2) swollen lymph nodes- occur in the neck, armpits, and groin, they may remain swollen until later stages of HIV infection 3) neurological symptoms- may appear, either because HIV has spread to the brain or because other organisms have caused a brain infection. among the neurological symptoms are dementia, weakness, and paralysis caused by spinal cord damage. pain, burning, tingling

Pelvic inflammatory disease

general term for an infection of the pelvic organ -symptoms of PID- abdominal pain or tenderness, lower-back pain, pain during intercourse, abnormal vaginal bleeding or discharge, fever, or chills -caused by a number of organisms, but the most common culprits are the sexually transmitted bacteria that cause chlamydia and gonorrhea -bacteria ascend from the vagina through the cervix to the uterus -infection can be curbed by treatment with antibiotics, which kill the bacteria

Form of HIV

genetic material in HIV is RNA, the RNA along with several virus-specific enzyme is encased in a protein coat -RNA and protein coat constitute the core of the virus -surrounding the protein coat is an outer covering, or envelope, consisting of spikes of protein embedded in a lipid membrane -lipid membrane is actually a piece of plasma membrane stolen from the previous host cell and altered for use by the virus -protein spikes of the viral envelope are responsible for binding the virus to the host cell

Strains of HPV

genital infections with some strains of HPV are low-risk infections-->genital warts, warts can be flat or raised and can occur singly or in groups. without treatment they grow in size -genital warts are diagnosed on the basis of their appearance

The HIV genes can reside in a...

helper T cell chromosome for years, until the cell is activated to respond to some foreign antigen, such as another kind of virus, or fungus, or a parasite -at this point the virus begins making copies of itself instead of allowing the cell to fight the invader -viral genome is activated and turns the cell into a virus factory, some of the newly produced HIV RNA will become genetic material for new viruses and some will be used to produce virus-specified proteins

HIV

human immunodeficiency virus, causes AIDS -AIDS is actually the final stage in an HIV infection during which the immune system is slowly weakened -primary target of HIV is helper T cells which serve as the main switch for the entire immune response -HIV enters a helper T cell and the T cell stops functioning well, although this cessation of function is not immediately apparent -HIV will eventually kill the infected helper T cell

Treatments for genital warts

intended to kill the cells that contain the virus 1) freezing 2) burning 3) laser 4) surgery 5) podophyllin (chemical painted onto the warts and washed off

The newly formed viral DNA......

is then spliced into the host DNA -once HIV's DNA is integrated into the host cell chromosome the DNA is called the HIV provirus -after they have been incorporated into the host cell DNA the host cell treats the HIV genes as it would its own -each time the cell reproduces the viral DNA is copies along with the cell's DNA

Genital Herpes Type 2

more likely to be found below the waist where it causes genital herpes on the genitals, buttocks, or thighs

males

most common site of chlamydial infection is the urethra, because this is the mucous membrane most likely to be exposed to the bacteria during sexual intimacy

Chlamydia

most frequently reported infectious disease in the US

genital HPV

most people are not aware of the infection because they don't have symptoms -newly released virusses can cause genital HPV on uninfected areas of the same person or on another person if genital contact is made

Pregnancy and herpes

most woman have successful pregnancies and normal deliveries but in rare cases the infection spreads to the fetus as it is growing in the uterus and can cause miscarriage or stillbirth -can be transmitted to baby during delivery

cure for herpes

none, there are three drugs: zovirax, famvir, and valtrex, that help ease symptoms

man is more likely to experience...

noticeable symptoms of chlamydia and gonorrhea, men are more likely to seek diagnosis and treatment before the infections have caused lasting damage -undiagnosed chlamydia and gonorrhea can have long-term reproductive consequences for both men and woman so it is important that a man who is diagnosed with chlamydia or gonorrhea inform everyone he has been sexually intimate with

Gonorrhea

one of the oldest known sexually transmitted diseases, caused by the bacterium Neisseria gonorrheae

why are STDs so rampant

people are often unaware that they have been infected -the symptoms of some STDs, such as syphilis, disappear without treatment, leading the person to believe- mistakenly- that he or she is cured

Chlamydia and gonorrhea are of special concern to...

pregnant women -newborns can be infected with either chlamydia or gonorrhea as they pass through an infected cervix or vagina at birth -place the fetus at risk -chlamydia can cause the protective membranes around the fetus to rupture early which can kill the fetus

Second class of antiviral drugs

protease inhibitors -after the HIV genetic information has been inserted into the DNA of the host cell, it can begin producing proteins needed to form new copies of HIV -proteins initially produced are too big to be used and must be cut to the proper size by an enzyme called a protease -protease inhibitors block the action of this enzyme, preventing a necessary step in the preparation of proteins for the assembly of new viruses

Chlamydia and gonorrhea can now be diagnosed in a physician's office with...

quick, accurate tests -urine tests detect the DNA of chlamydia or the gonococcal bacterium -can also be diagnosed by observing the bacterium in a smear of cells taken from the infected area or grown in a laboratory -some strains of the bacteria are now antibiotic resistant however so you have to keep retesting

Herpes simplex viruses

quite contagious and can be spread by direct contact with viruses that are being shed from an infected surface or that are in the fluid on the blisters -mucous membranes are most susceptible. skin is a good barrier unless there is a cut, abrasian, burn, acne, eczema, or other break

Chlamydial infections

rapidly becoming epidemic because they are highly contagious and because they do not necessarily cause noticeable symptoms that would prompt the infected person to seek treatment -people who have chlamydia do not have symptoms, and many people learn that they have it only because a responsible partner diagnosed with the infection informs them

Syphilis

rates decreased steadily during the 1990s, reaching their lowest point in 2000 -caused by a corkscrew-shaped bacterium called treponema pallidum -these bacterium are extremely delicate and cannot survive drying or even minor temperature changes -can contract syphilis only by direct contact with an infectious partner, bacteria can invade any mucuous membrane or enter through a break in the skin -bacteria can also cross the placenta and infect the growing fetus

If left untreated, gonorrhea can cause...

scar tissue to form in the tubes through which gametes travel. if the vas deferens or oviducts are completely blocked by scar tissue, the man or woman becomes sterile -women are more likely to become sterile than men because women are less likely to have symptoms that prompt treatment

secually transmitted infection

symptoms of some STDs, such as syphilis, disappear without treatment leading the person to believe that he or she is cured, so authorities now favor the term STI

Sexually transmitted diseases

take a serious toll on humanity, both in their direct effects on the infected individuals and in their cost to society in general -most common among adolescents and young adults because they're the most sexually active

What do chlamydia and gonorrhea primarily infect?

the mucous membranes of the genital or urinary tract, throat, or anus -bacteria that cause these STDs cannot survive long if exposed to air, so they are generally transferred by direct contact between an infection mucous membrane and an uninfected one during sexual intimacy -mucous membranes of the urethra or reproductive structures -can spread to the lining of the anus during anal intercourse or to the throat during oral sex -can infect the eyes if an eye is touched by a finger that has just touched an infected area

During dormant periods...

the virus retreats to ganglia near the spinal cord. at times of stress the virus may be reactivated and blisters will appear

Asymptomatic stage

weeks to months after the initial sage of infection, the person usually feels well again, often for several years -during this stage, the immune system mounts a defense strong enough to control, but not conquer, the infection -rate of the helper t cell production increases -during the asymptomatic stage HIV is far from idle -spaces between cells in the lymph nodes become packed with virus particles -most helper t cells reside in the lymph nodes and many of them have the DNA form of HIV genes incorporated into their own chromosomes -helper t cells frequently circulate through the lymph nodes, this is an opportune place for HIV to encounter healthy T cells