Viral STI Flashcards
Influenza H antigen and N antigen
Hemagglutinin antigen is responsible for getting the virus in the host cell
Neuraminidase allows the repacked virus to exit the hose cell
N and H AG can be changed with replication making different antigens = H1N1 - bird flu
H1N1 subtype = swine flu
Specimen collection for virus
- viruses shed early in infection , high numbers within 3 days , decreasing its sensitivity 3 days after onset of symptoms
-sample should be taken from where the virus causes the infection
-secretions are best, use swabs with dacron or rayon swabs - plastic or wire shafts
-Ca alginate and wood are toxic to SOME virus
-must be correct temperature when testing
-Media will be UTM
-only respiratory and swabs, and tissue can do in UTM
-dont put Blood, bone marrow or CSF/fluids in UTM (empty container)
- collect in sterile screw top container which is unbreakable if frozen and thawed
-pcr has its own media
how to process virus samples
virus recovery affected mostly by time and temperature
- do immediately
-if delay store at 4C
-if delay over 72 hours - freeze at 70C
-dont freeze at -20 because ice crystals form which can harm the sample
-dont freeze/thaw/freeze = affects stability
4 main ways to diagnose a sample
direct detection of virus in sample
-isolation of virus in cell culture (not all can be grown)
-serological assays to detect ABs to virus
-molecular testing like PCR
What are serology tests for virus detection
AG/AB testing in vitro
-to see if person has AB to viral AG in serum, plasma or other fluid
-retrospective tests (look back and get more information AFTER infection not during)
-AB can determine the disease stage (IgG or IgM (acute or chronic, new or old)
Agglutination, ELISA, Immunofluorescence assay, Compliment fixation, chemiluminescence Western blot
new vs past
IgM without IgG or with low levels IgG = new infection
IgG without IgM = past infection
IgG at much higher levels in serum than IgM = past infection
What is Retroviridae (family) - Lentivirus how is it transmitted
-causes HIV
HIV 1= worldwide
HIV -2 in Africa and India
Tranismitted from fluid/blood from person with HIV with detectable load of virus
-sexual activity
-blood - IV use
-Mother to infant - utero or breast milk
HIV Pathogenisis
ACUTE- stage 1
-CD4 positive T helper lymphs targeted by HIV virus using gp120/gp41 spike proteins
-once the virus is inside the cell itll start replicating in and lysing CD4 lymphs into blood stream = infectious person
-can be aysmp or mild flu like with infectious mono (days or weeks)
INFECTIOUS
Chronic Phase of HIV
Stage 2
- period of latency - 10-15 years
-Asymp but the virus still replicates in lymphoid tissue
-viral load tests need to be done
-no virus detected = person is not infectious
-if virus in low levels = infectious - can transmit
stage 3 of HIV pathogenesis
AIDS
-caused due to weak immune system and cytokines which reactivate the virus leading to increased replication resulting in loss of CD4 cells (less than 200) that help fight the immune system if they are not treated
Symptoms of AIDS
Persistent chronic infections -Pneumocystis jiroveci (considered diagnostic for HIV becoming AIDs)
-diarrhea
- weight loss
-decreased immunity = persistent infections
Major Ag of HIV -1 that appear in in Acute infection
1.Viral RNA
2.p24 antigen
3. anti-HIV antibody
how to diagnose HIV in the lab
use body fluid, blood (serum /plasma), or saliva
What is the window for testing = until HIV can be detected
3rd generation tests - only test for ABS - not done anymore because of long window of testing (takes 10-12 weeks for a person to make these Abs = only time to be tested)
4th generation test -
detects AB and AG at the same time detect HIV-1 (gp160 & gp41) Abs and HIV-2 (gp36) Ab & p24 Ag by enzyme linked floursence immunoassay
-detects P24 Ag so decreases the window for testing
very sensitive - no false negatives
-if test is neg - stop but you can get false pos because youre testing for alot of things
follow up a positive with HIV-1, and HIV-2 AB differentiation immunoassay test
What is the algorithm for HIV testing
Check slide for flow chart
NAAT for HIV 1 RNA
- 2ndary confirmatory test when the AB differentiation test is indeterminate or negative for HIV 1 or HIV 2 AND positive SCREEN TEST
if screen test was positive and NAAT is positive = acute HIV 1 infection
NAAT can detect HIV pos in 7-14 days after exposure but its too expensive
-used as a pooled screening in patient strategy
not done for HIV-2 - very rare
if differentiation test is indetermined and naat is is negative
-treatment failure
OTHER LAB TESTS FOR HIV POSITIVE
CD4 /T CELL COUNT
-# of CD4 cells are counted
-normal is 500-1000 cells/uL and the amount decreases as disease progresses
-cd4 <200 cells/uL = diagnosis for AIDS
-measures immunosuppression and risk of opportunistic infections
-when under 350 cells/uL start the antiretroviral treatment
-count can also be used to determin if treatment is working
OTHER LAB TESTS FOR HIV POSITIVE
VIRAL LOAD
-measures infectivity and treatment process = how much HIV is present in 1 mL of blood = real time PCR = detection of HIV RNA
high viral load > 100000 copies = virus is replicating, disease is progressing = highly infectious person
HIV viral load <10000 copies = virus not replicating, slower damage to immune system = infectious person
HIV <20 copies
-GOAL OF HIV TREATMENT
-not cured but can live near normal live
-very little risk of infecting others , but still use condoms
OTHER - test for opportunistic infections
Herpesviridae Cytomegalovirus (CMV)
Herpesviridae - CMV is human herpes virus number 5
-transmitted p/p , sexually , transfusion
-Establishes latency in cells like WBC, endothelial cells, BM cells - can be reactivated by impaired immune system
-Healthy person can be asymp or show mono like disease in ppl that are immunocompromised
-causes serious congenital infection if primary CMV infection happens while mom is pregnant
-baby can be deaf , retarded, death
-TORCH screening organism- tested for pregnant women **
DIAGNOSIS OF CMV
specimen
serology
immunohistochemistry tissue stains
cell culture
specimen- blood , sterile body fluid, urine or resp specimen , tissues
serology - detects CMV ABs in serum,
IgM = new infection
IgG - past infection
immunohistochemistry tissue stains
-direct stain on tissue biopsy
- monoclonal or polyclonal fluorescent labeled antibodies against early CMV antigens – or enzyme labeled antibodies
cell culture
-pt sample inoculated onto human fibroblast cells and incubated
-observed for 2-21 days looking for cells that show cytopathic effect = foci of flat, swollen cells
DIAGNOSIS OF CMV
Antigenemia assay
Molecular testing like PCR or qPCR:
Antigenemia assay
-rapid test for detection of pp65 AG in CMV = marker of active virus replication , found in infected peripheral WBC nuclei of host
-uses monoclonal Ab to pp65 antigen bound to a fluorescent dye in early phase
-immunofluorescence stain
Molecular testing like PCR or qPCR:
-gene amplification
-DNA extracted from whole blood, white cells, plasma, CSF, urine
Herpesviridae
Herpes Simplex Virus (HSV) 1 & 2
HHV-1 also called HSV-1 (oral herpes, face and mouth, may spread to genitals), HHV-2 also called HSV-2 (genital herpes)
how is oral herpes transmitted
HSV-1
-transmitted through direct contact with secretions from lesions
-occurs without sores or symptoms
how is genital herpes transmitted
HSV-2 through sexual activity or skin to skin
-transmission can occur with or without sores or symps
-HSV-1 can be transmitted to genitals through oral-genital contact (25 % of genital herpes can involve HSV-1)
-HSV-1 & 2 can be transmitted mother to infant during delivery but uncommon
Pathogenisis of Oral Herpes HSV-1
Primary infection = asymp or seen as oral mucosal blisters (cold sores on the mouth)
-recurrent infections- virus is latent in sensory nerve of lips
-reactivation of virus can occur with stress, spicy food , wind, sun , fever -recurring blisters and ulcers
