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4.2 Blood Transfusion Science > Transfusion Transmitted Infections - Viruses > Flashcards

Transfusion Transmitted Infections - Viruses Flashcards

1
Q

What is the main issue with transfusion related infections

A

It can be hard to prove whether an infection is from a transfusion or is a previous infection

There will always be unknown infections that were not currently screening for or new-re-emerging strains etc e.g. Arbo virus or dengi fever etc

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2
Q

Talk about the history of syphilus transfusion related infections

A

Syphilius used to be the most common transmissible infection but penicillin almost wiped it out entirely -> there had been no positives in 20 years
However there is now 4 to 5 infection in the IBTS a year -> recurrence seen
However syphilus can only survive 4-5 days in a cold blood pack

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3
Q

How has our screening progressed?

A

We used to use fresh whole blood which wasnt screened

It was thought that albumin or fractionated products were thought to be clean

We didnt know about HepC -> only knew about HepA and HepB -> C wasnt named until the 1990s

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4
Q

What are the four properties of a transfusion transmitted infectious agent?

A

Gives rise to asymptomatic infection ‘healthy donor’

Is presentt in the blood stream, in wbcs, plasma etc

Is transmissiblle parenterally

Is able to survive storage of blood and components

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5
Q

What has been a major help in preventing TTIs

A

Volunteer donors introduced in the 1970s

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6
Q

What current micobiology testing do we have in place

A

Bacterial culture of platelets
Syphilus
Malaria since 2021
HIV
Hepatitis B, C and E
West nile virus
Anti-CM

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7
Q

What microbiology testing will we have in the future

A

prions
protozoa such as chagas, toxoplasmosis or leishmaniasis
testing for any emerging strains or re-emerging etc

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8
Q

Talk about our recent HepB transfusion related infection

A

In 2017 we had a case of TR hepatitis B
This was our first case in 20 years
It slipped through due to a statatastic error
i.e. there was so little viral particles in the sample that it depended on where you stuck the pippette into the same

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9
Q

How does Hepatitis B compare to HIV

A

Hep B is a very durable double stranded DNA virus
It can be left on needles for weeks while HIV wont survive longer than a day
HepB used to be the mosmt common healthcare infection due to needle stick injury

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10
Q

We currently hav nucleic acid esting in place for what?

A

HCV
HBV
WNV
Hiv

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11
Q

What is the current situation of positive results in Ireland

A

HIV 1 and 2 last positive in 2011
HBV 2-4 positives per year
HCV 2-4 positives per year
HTLV1/2 -> 1 in 10 years?
Syphilis -> 4-5 positives per year
Anti-CMV in 22% of donors
HEV 1 in 5000 donors but clusters
Chagas not tested for but 1:2000 US donors -> hence deferral

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12
Q

Talk a little on HIV and its name

A

HIV used to be called HTLV3
HIV and HTLV are very similar rna viruses
They insert themselves into while cells and can regrow into rna and sprout out of cells etc

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13
Q

Talk about HTLV

A

Causes tropical spastic paralysis
Its seen in the US but not really over here
Hence we only test first time donors to reduce cost -> its only an Ab test
Weve only had a single positive in 20 years so we moved to first time donors only

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14
Q

How does Ireland CMV levels compare to the rest of the world

A

We have low levels compared to over 90% in some countries, its about 40% in most countries

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15
Q

Talk about HEV in Ireland

A

Clusters seen arround abattoirs or farms
Pigs and pork meat
Associated with easter and christmas - cocktail sausages etc

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16
Q

Talk about chagas disease

A

Seen in bolivia hence we dont test for this we only defer

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17
Q

Whst id the residual risk of transmission of HBV, HIV and HCV

A

1:2 million for HBV
1:15 million for HIV
1:15 million for HCV

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18
Q

Why have certain viruses been increasing in frequency

A

International travel and migration has increased e.g. WNV incidence

Only certain mosquitos carry malaria but these have migrated north due to global warming thus were getting more positives

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19
Q

Talk about bacterial infection related to transfusion

A

Occassional contamination with microorganisms such as psudomonas, serratia, yersinia, staphs and E, Coli

can result in devastating endotoxic shock

Dependent on quality of blood taking, processing and storage protocols etc

Most likely a problem with patelets as theyre stored at 22 degrees

Highest infectious risk even though still rare

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20
Q

What measures are in place to reduce bacterial contamination

A

BacT alert for all platelets
Cleaning of site of donation thoroughly
Diverting first few mls of pack

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21
Q

Why is bacterial contamination still an issue even with SD treament

A

this is because inactivation methods such as intercept cannot guaranttee to kill bacteria as these have a cell wall
This is why BacT still recommended for platelets

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22
Q

What is the main benefit of NAT over Ab detection

A

NAT greatly shortens the winodw period of detection e.g.

HIV from 21 days to 5.6 with NAT
HCV from 58.3 days down to 4.9 with NAT+serology
HB from 38.3 to 15.6 with NAT + HBsAg

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23
Q

What is the main benefit of NAT over Ab detection

A

NAT greatly shortens the winodw period of detection e.g.

HIV from 21 days to 5.6 with NAT
HCV from 58.3 days down to 4.9 with NAT+serology
HB from 38.3 to 15.6 with NAT + HBsAg

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24
Q

Why is hepatitis B our main issue?

A

This is because even with NAT the window period remainas at 15.6 days
i.e. its undetectable for 2 weeks by either method

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25
Q

Talk about hepaitis A

A

Hepatitis A is known as yellow jaundice
It spreads through schools
There are no longterm affects
Its a childhood virus
Its gone in two weeks

We have no test for it

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26
Q

What do we do NAT testing for?

A

Hepatitis B
Hepatitis C
HIV
HEV
WNV

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27
Q

We have NAT testing for Hepatitis B but what do we also test for?

A

We also test for HBsAg as a marker of ‘carrier’ state in donors as well as an anti-HBc

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28
Q

We have NAT testing for hepatitis C but what do we also test for?

A

We also test for anti-HCV in donors

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29
Q

We have NAT testing for HIV but what do we also test for?

A

we also test for the antibody as an indicator of infection

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30
Q

What serology testing do we do?

A

Anti-Human T lymphotrophic virus (HTLV 1 and 2)
Cytomegalovirus

These are seroloy based only, other serology used in combination with NAT for HBV, HCV, HIV

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31
Q

How is serology testing done in the IBTS

A

Serology is done on the Abbott Alinity s

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32
Q

What seven serological assays are ran on the abbott alinity s

A

HIV antigen and antibody
anti-HCV
HbsAg
anti-HBc
Syphilis total
ant-HTLV
anti-CMV IgG

NB - malaria antigen now carried out

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33
Q

How is NAT testing done in the IBTS

A

NAT is done on the Nucleic Acid Testing (plasma) Panther System (Grifols) instrument, Ultrio-elite (UE) assay

Screening for HBV/HCV/HIV is done simultaneously in the one tube (triplex NAT)

HEV and WNV are done separately

ID-NAT done on every donation

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34
Q

Do we detect the DNA or RNA of HIV, HCV and HBV

A

HIV-RNA
HCV - RNA
HBV - DNA

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35
Q

List some other infections that we try to rule out through the questionnaire to minimise risk of

A

Malaria
Syphilis
Trypanosomiasis - sleping sickness
EBV
Parvoviruse B19

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36
Q

Why can it be difficult to prove infection is associated with transfusion?

A

Onset of symptoms may occur weeks to years after date of transfusion e.g. HepC diagnosed in 2022 was actually from a case in the 60s

Bacterial or parasitic infections are usually acute and come to clinical attention and association with transfusion -> however sepsis is quite common after surgery so dfficult to prove -> sequencing of strains may need to be done -> might have to go back to donor samples kept in IBTS

Viruses are quite different though and the proof of association is complication with time, death records, sampling etc

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37
Q

What are three ways of confirmig a post transfusion infection?

A

Evidence of infection following transfusion, with no evidence prior to transfusion

A donor, who had evidence of the same infection, donated at least one component received by the infected recipient

At least one component received by the infected was shown to have been contaminated with the same infectious agent

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38
Q

What are you most at risk of getting from a transfusion

A

Since the mid 90s bacteria was greatest risk but now all are minute
Bacterial risk is way higher than viruses
But there has been practically none sinc 2010 as weve gotten very good at preventing this
There has been no bacterial infections since 2010

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39
Q

Talk about the 2022 figures on reports of possible TTIs reported to the NHSBT/UKSA Epidemiology unit

A

There was 124 initial reports but none if these ended up being true TTIs:
- 115 queryy bacterial - 62 were post transfusion reactions with no evidence of inection
- 1 query parasite - negative
- 8 query viral - 1 was confir,ed TTI HBV but this was historic traceback from years ago - 2 peope received blood from this donor

40
Q

Currently at 1.9 million donations per year, we ill miss a potentially infectious window period every how many years for HBV, HCV, HIV

A

Every 1 year with HBV
Every 35 years with HCV
Every 18 years with HIV

NB: in practice far fewer TTIs were observed in practice than these estimated risks

41
Q

What are our strategies to reduce risk of transfusion transmitted infections?

A

Donor selection
Processing, quality control
Screening tests
Storage, pathogen inactivation
Better blood transfusion
Tracin surveillance -> any positives reported to HSE-department of health then IBTS is contacted to see if unit was transfused and who to

42
Q

What are the two important structural components of viruses?

A

Capsids
Envelopes

43
Q

Talk about the capsid of viruses

A

The protein shell that encloses the nucleic acid
With the enclosed nucleic acid it is called the nucleocapsid
This shell is composed of protein organised in subunits known as capsomers

44
Q

Talk about the viral envelope

A

Many types of viruses have a glycoprotein envelope surrounding the nucleocapsid
The envelope is composed of two liquid layers interspersed with protein molecules (lipoprotein bilayer) and may contain material from the membrane of a host cell us wall as well as that of viral origin

Envelopes pick up some parts of cell its from
Some viruses need an envelope other dont e.g. HepB doesnt need its envelope and can infect without it

45
Q

List some enveloped viruses

A

HepB
HepC
HIV I and II

46
Q

List some nonenveloped viruses

A

HepA
ParvoB19

47
Q

What are the top risks associated with transfusion?

A

1= febrile/allergic/hypotensive reactions (1 in 1,000)
2 = risk of pulmonary complications

3 = transfusion-related deaths (by component issued) (1 in 1 million)
4 = death from TACO (2018)
5 = transfusion-related death due to error
6 =HBV

7 = HIV (1 in 10 million)

8 = HCV (1 in 100 million)

48
Q

What are the five main sources of risk in transfusion

A

Infectious, but seronegative window period
Variants of known agents
Laboratory error
New agents for which no test is available
Unknown agents -> dont know its happening at all as with HepC or covid

49
Q

Talk about hepatitis A transmission

A

Spread through faecal oral route

HAV transmission very unlikely with no chronic/carrier state -> IgG anti-HAV

A donor would have to donate during the viraemic period which is unlikely to happen

age limits are assigned to donors to reduce risk (hepatitis in young)

50
Q

What kind of virus is hepatitis A

A

Picornavirus
A 27nm non enveloped RNA virus

51
Q

Talk about HAV TTI

A

Rare cause of post transfusion hepatitis

There are a few documented cases (1992) were noted in haemophiliacs who recieved concentrates which werent virally inactivated

52
Q

What has been our most successful way of getting rid of HAV risk?

A

Donor questionnaire:
- askinf if youve ever had childhood hepatitis i.e. hepatitis before th age of 13 -> if aftet this age then we wont risk taking blood from you

Testing
- we still test for it even with questionnaire

53
Q

What is hepatitis B virus, comment on its structure

A

First identified in 1963 by Blumberg
Its part of the hepadnavirus family
Its a 42nm dsDNA virus composed of an outer shell and a core also known altogether as the dane particle

Inner coat = HBcAg
Outer coat = HBsAg (shed)
Main polypeptide is core p19

54
Q

Comment on the prevalence of hepatitis B

A

A major pathogen with 5% of population being carriers
4 million new cases each year with 1 million dieing per year
350 million people are chronic carriers

55
Q

Comment on the prevalence of HBV in Ireland over the years

A

In the 1970s 0.1% of first time donors were positive

Between 1975 and 1990 there were 91 positives from health care staff -> years ago if anyone cut themselves in the lab they nearly always got HBV

56
Q

Comment on the morbidity of HBV

A

1-3% die
5-10% get chronic hepatitis

57
Q

What is the HBV australia antigen

A

This is the HBV surface antigen

The virus produces huge amounts of this as a decoy -> this allows the virus to live in the host for longer before an antibody is produced directly against the virus -> this stops chronnic infection developing -> will eventually clear the virus

58
Q

What is the HBV australia antigen

A

This is the HBV surface antigen

The virus produces huge amounts of this as a decoy -> this allows the virus to live in the host for longer before an antibody is produced directly against the virus -> this stops chronnic infection developing -> will eventually clear the virus

59
Q

What is th HbcAg of HBV

A

The inner coat of the virus

60
Q

What is the HBsAg of HBV

A

The outer coat of HBV

61
Q

The production of what antibody means you wont be a carrier?

A

If you develop anti-surface antigen you cannot be a carrier

62
Q

Talk about the HBsAg

A

The outer coat material, referred to as HBsAg
It can be detected free in serum or as part of the intact virus

It is highly immunogenic and constituted the source of early vaccines

HBsAg is readily detected in serum, in hepatocytes and forms the basis for screening blood donors

63
Q

We used to use HBsAg based vaccines, what do we use now?

A

We now use recombinant yeast derived products

64
Q

Talk about HBcAg

A

HBcAg = core

The core contains dsDNA, DDNA polymerase actvity and core particles HBcAg as well as a cleavage antigen of HBc called HBeAG

HBcAG is not readily detected free in serum and does not constitute as a marker but antibody against it does

Anti-HBc is a measure of past or current viral replication, IgM then IgG

65
Q

What is HBeAG

A

Its a cleavage antigen of HBc known as HBeAG (ie a smaller version of HBc)

HBeAg is only found in active infection

Appearance of HBeAg free in serum reflects viral replication and a state of high infectivity

66
Q

Talk about HDV

A

Delta virus

Its only found in the presence of HBV and co-infection

It can lead to more serious and progressive liver disease

67
Q

Talk about the progression of HBV

A

HBs Ag appears 2-6 weeks after exposure
Possibly early HBeAg and anti-HBc (IgM)
Period of viraemia and raised LFTs
acute infection wanes after 6 weeks
Enzymes return to normal
2nd window period follows, variable
Recovery is signalled by anti-HBsAg, which also confers immunity

68
Q

What happens after month 7 of HBV infection

A

After month 7 surface antigen is gone
No longer an infection as antibody produced but you can still hav enough hepatitis to be transmissible but you wont have enough surface antigen or antibody to detect this

But you will still have anti-HBe antibody still present hence why we use this antigen to detect past infections

69
Q

What antigens persist in chronic HBV

A

HBsAg and HBeAg persist beyong 6 months (9-10% of individuals)

Anti-HBc (IgG) and anti-HBe can be markers of the chronic/carrier state

70
Q

talk about HepB infections as a result of transfusion

A

Lots of women got it in the past from anti-D products
women didnt know they had this but have low grade liver issues
However lots of these women went on to develop liver cancer

71
Q

Why are we particularly concerned with HepB infections in patients

A

There is further risk of progression to cirrhosis and hepatocellular carcinoma, particularly in the immunocompromised

HepB and HepC cause chronic inflammation - those that develop cirrhosis can also develop into hepatocellular carcinoma

HepB patients tend to relapse badly and often end up back in hospita etc

72
Q

What is the hallmark for chronic state of HBV infection

A

You will always be able to detect the anti-HBc antigen

73
Q

What is Hepatitis C

A

An enveloped lipid coated flavivirus
Its a single stranded RNA virus
It used to be called nonA nonB hepatitis as in the past there was only Hep A, B and D in the 80s
years after it was shown to be transmissible in blood

74
Q

Talk about the morbidity of hepatitis C

A

Of every 100 people infected, 75-85 will develop chronic hep C if left untreated:

60-70 will develop chronic liver disease
5-20 will develop cirrhosis over a 20-30 year period
1-5 will die from cirrhosis or liver cancer

75
Q

How did we used to treat HCV and how do we do it now

A

Used to treat with interferons
Now we have a 12 week treatment to clear the infection

76
Q

What % of HCV become chronic and what are cleared

A

60-70% become chronic active or chronic persistent
20% develop cirrhosis but this can take up to 50yrs to occur
1-5% Ca of liver
This is exacerbated by alcohol

20% of adults and 45% of children will completely clear it

77
Q

Why was HCV treatment with interferons not successful?

A

Treatment varies based on genotype e.g. HCV type II low response to alpha interferon therapy

78
Q

Talk about our new method of treating HCV

A

Harvoni

Its a combination of sovaldi a nucleotide analog NSSB polymerase inhibitor and ledipasvir a NSSA inhibitor

90% of patients with hep C type 1 are cleared in 12 weeks

It is very expensive at 25,000 per patient

There is still no vaccine

79
Q

What are the two components of Harvoni for HCV

A

Sovaldi
Ledipasvir

80
Q

Who is HCV most common in?

A

Drug addicts

81
Q

How has testing for HepC improved

A

In 1970s it was just non A non B Hepatitis
In 1988 we had successful cloning of HCV and subsequent development of core protein and antigen testing (C-22-3 and c33c)
We now have recombinant immunoblot assay and NAT to confirm HCV in a narrow window period

82
Q

How did we successfully clone HCV

A

The use of infected chimpanzee plasma, nucleic acid extraction, manufacture of cDNA

83
Q

We use a RIBA assay to detect HBV, what does RIBA stand for?

A

Recombinant Immunoblot Assay

84
Q

What was the controversy surrounding Hepatitis C

A

At first we were only using RIBA to detect HCV and not NAT
This resulted in HepC transmissed through blood
Tribunal questioned wether or not there was a delay in the introduction of NAT for HepC -> we lackd funding for education at this point in time

85
Q

What is the incubation period of HCV

A

3 weeks to 3 months

Early appearance of HCV RNA and a further 1-4 weeks for anti-HCV

86
Q

What is the rate of chronic infection in HCV and why is this significant?

A

Chronic carrier state is high with 60% plus of sufferers having persistant HCV RNA in serum and liver for decades

This has implications for infected persons by historic transfusions

87
Q

What are the HCV markers during early infection

A

HCV RNA detectable from day 12
HCV antibody detectable from day 70

88
Q

How does acute vs chronic hepaitis compare

A

No anti HCV antibody produced in chronic diseas - neither IgM or IgG
While HCV-RNa will fall in acute its levels can rise agains in chronic infection

89
Q

Talk about HIV

A

A retrovirus
RNa virus
HIV 1 and 2

Self exclusion by donors
NAT testing
Residual risk of 1 in 2 million in USA

90
Q

Talk about the history of HIHV in transfusion

A

Early indications of HIV association with transfusion noted in 1982 with 3 cases in haemophiliacs

within a few years studies showed well in excess of 50% of haemophiliacs who received clotting concentrates in the ealryl 80s developed HIV-1

Similarly an alarming number of other transfusion recipients were shown to be infected

It was estimated that 1 in 100 in san francisco were infected at one point

The worldwide number of TRI of AIDS is not known

91
Q

Talk about the haemophiliacs that were infected with HIV via transfusion

A

They often died within 4 years
Survival was either as litle as 2 or as long as 4
The worse your immune system the longer yoou survived and vice versa

92
Q

How does HIV infect its host

A

Its a retrovirus that preferentially infects CD-4 T Helper cells
It utilises hosts to replicate

93
Q

How does HIV infection develop

A

Most infected individuals recover from the initial infection within 2-3 weeks, seroconvert and become asymptomatic

Thus antibody development does not imply an inability to transmit the virus

mean incubation time between transfusion and AIDS is estimated at 4.5 years but is within a range of 2 to 14 years

94
Q

How do markers of HIV develop over couse of infection

A

HIV RNa detectable from day 11
HIV p24 antigen detectable from day 16
HIV antibody detectable from day 22

95
Q

How do we test for HIV 1 and 2

A

Most anti-HIV tests incorporate antigens common to 1 and 2
Many screens combine antibody and antigen assays
NAT testing can be done on pools or individual donations

96
Q

What is the one debated issue with HIV testing

A

The cost effectiveness of testing for both HIV RNA and HIV antibody:
- cases of positive RNA where the screen was negative is rare so why bother doing the NAT at all as antibody should catch all

97
Q

Talk about th serotypes of HIV

A

A number of groups of HIV1 have been identified - M and O

With a lot of subtypes of M (A-K), B being most common in EU and US

The ability to detect HIV-1 subtype O is considered critical

There are still HIV vaiants that we wont be able to detect

4.2 Blood Transfusion Science (18 decks)

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