MICROBIO 160 1st Edition Lecture 22 Outline of Last Lecture I What are Viruses II Characteristics of HIV III Types of HIV IV V Major Viral Components HIV binding to CD4 T cell VI Replication of DNA VII HIV Integrase VIII HIV Protease IX HIV Pathogenesis X How does HIV destroy CD4 cells XI Syncytia Outline of Current Lecture I When should you have an HIV test II Where can testing be found III Types of HIV tests IV Types of Screening Tests V How the HIV ELISA test works VI Rapid HIV test VII HIV Proteins VIII Western Blot IX Progression of HIV infection Current Lecture Specific guidelines on when to have an HIV test Having 3 sexual partners in the last 12 months These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Have received a blood transfusion prior to 1985 or have a sexual partner who received a transfusion and later tested positive for HIV If you re not sure about one s sexual partner s risky behaviors If you are a male who has had sex with another male MSM men who have sex with men Using street drugs by injection sharing needles you don t know if it is sterile Having a sexually transmitted disease Being a healthcare worker with direct exposure to blood on the job Where can I be tested Globally HIV testing is provided at a number of locations including hospitals health clinics doctors or surgeries specialist HIV AIDS voluntary counseling and testing sites Other places that you can potentially be tested in include in the home industrialized nations schools workplaces religious facilities through mail order or online mobile and outreach testing in the community Types of HIV Tests 1 Screening tests highly sensitive in a small percentage of cases the test result will be positive even if the person is not infected 2 Confirmatory test Western Blot looks for proteins 3 Tests of HIV progression a HIV viral blood How much virus you have in your system b CD4 cell count How many CD4 cells you have in your blood system HIV tests What do they test for What is the window period How long for the results Reliability Commonly used in Antibody tests HIV antibodies 3 months Between a few days and a few weeks High Europe Antigen p24 test P24 viral proteins 11 days to one month A few days to a week High for primary infection increasingly unreliable afterwards UK standard screening assay Fourth generation HIV antibodies 11 days to 2 14 days High UK recommende tests and p24 viral proteins one month d at first line assay US PCR NAT test Genetic material belonging to HIV 12 days Up to a week High Rapid test HIV antibodies 3 months Within 20 minutes Satisfactory Resourcefor poor settings uncomplicated HIV infection Most developed countries How the HIV ELISA test works Testing of blood for HIV antibodies Well is coated with HIV antigen Patient s serum is added o The ELISA TEST a color change in the final step indicates that the patient has HIV antibodies in their bloodstream o Anti human antibodies will bind any human antibody in the well Washing between steps removes unbound antibodies Anti human antibody with attached enzyme is added o Anti human antibodies will bind any human antibody in the well Washing between steps removes unbound antibodies Substrate to enzyme is added o If enzyme is present substrate activates it color change False Negatives happen if a patient has HIV but there is no color change Rare This is because there is not enough antibody in the sample Old test kit bad HIV antigen False Positives happen if a patient does not have HIV but there is a color change This is because there is not enough washing Rapid HIV Test 1 HIV antibodies from oral fluid are collected through the swab 2 Once the device is inserted in to the test tube the oral fluid mixes with the liquid and travels up the test stick 3 If C Line turns dark it confirms the test is working properly If nom C Line appears the test is not working a If only C Line appears the test is negative 4 HIV antibodies collecting at the T Line indicate the test is positive HIV Proteins the confirmatory test The Western Blot looks for specific HIV proteins in a patient s blood Envelope proteins the enV gene codes for polyprotein that is cut into gp120 and gp41 Pol proteins the POL gene codes for a polyprotein that is cut into p64 53 and p34 together these make the reverse transcriptase Gag and vpr proteins help HIV infect a host cell Western Blot and Specific HIV Proteins run out the proteins in a gel so that they get separated by the size of the protein smallest size moves the fastest so it will be at the bottom No bands present negative Bands at either p31 OR p24 AND bands present at either gp160 OR gp120 Positive Bands present but pattern does not meet criteria for positivity indeterminate Gp160 Viral envelope precursor env Gp120 Viral envelope protein Env binds to CD4 P24 Viral core protein gag P31 Reverse transcriptase pol Progression of HIV infection The column marked PC is an HIV positive test result and the column marked NC is an HIV negative test result Column 3 10 are tests performed on a single person beginning with the day when the person was first exposed to HIV Column 3 Day 0 to when the person had a fully detected HIV infection Column 10 Day 30 o The number and quantity of expressed HIV proteins is increasing over time Effect of Viral load on HIV Detection a person with HIV can have a viral load from less than 50 copies to over 1 000 000 copies of the virus per millimeter of blood copies mL the HIV virus is undetectable when the HIV concentration in the blood is less than 400 to less than 50 copies of the virus mL on test sensitivity undetectable value varies High for example greater than or equal to 100 000 copies mL Low for example fewer than 10 000 30 000 copies mL Undetectable for example either less than 400 or less than 50 copies mL depending on the test used If you get HIV it will eventually kill you no matter what medication you are taking HIV Resistance and Mutations resistance is the decreased ability of drugs to control HIV Resistance affects treatment options limits Genotype test check for mutation in HIV that cause drug resistance looking at genes and making a prediction Phenotype test challenges virus with all HIV drugs in a test tube actually checking Virtual phenotype test genotype test that uses phenotype information to predict which drugs will be effective against HIV and its mutations How does HIV develop
View Full Document
Unlocking...