Wednesday, November 7, 2007

19th Week of SIP - Medical Microbiology

Hi All!

I am sharing about a very scary virus infection. It causes hepatitis and has mortality rate of 30 percent. Quite scary huh!

We all heard about hepatitis B. But the motality rate of hepatitis B is not that high (0.5 - 1%). However this particular virus is somehow related to hepatitis B virus and it depends on the hepatitis B virus to infect the host.


Hepatitis D Virus

This interesting virus is the Hepatitis D Virus (HDV). HDV is a single-stranded RNA virus and it has HDAg as a enveloped protein (enclosing the RNA) and HBsAg (derived from hepatitis B virus) as its surface antigens. Without the HBsAg coating, HDV cannot infect, replicate or express on its own. The famility of HDV has not been identified.

Route of transmission and symptoms are similar to those of HBV. But it is more severe. It was reported that 70-80% of chronic HBV carriers with HDV superinfection develope chronic liver disease wuth cirrhosis.

As I mentioned HDV need HBV, thus the disease occur when HDV either superinfects the chronic HBV carriers or coinfect the person together with HBV. Symptoms are more severe in superinfection cases.

There is no vaccine for HDV and the best way to prevent it is to avoid risk behaviors. Immunization to HBV can avoid coinfection.

Okay...so much about the background and now I am sharing the laboratory diagnosis of HDV.

HDV is diagnosed serologically by detecting total antibodies to HDAg (delta antigen) by Competitive ELISA. The principle of the essay is as below. Enjoy....



Anti-HD present in the sample and labelled anti-HD antibodies compete for a fixed number of HDAg on the surface (sold-phase). The enzyme-labelled anti-HD gives colour after adding substrate, and the concentration of enzyme-labelled anti-HD can be worked out in relation to the O.D. reading. The amount of labelled anti-HD measured is inversly propotional to the concentration of anti-HD present in the samples.


OK. That's all for my posting. I hope you all enjoy it.
All the best for your SIP & MP yeah!
Cheers
~Ye Tun
TG01

9 comments:

Distinction in Disaster! said...

hi ye tun!

wah... sound interesting but yet still scary...

you say that HDV will only infect when the person has HBV. can you elaborate more? what special relationship that HDV has with HBV?

Lizzie

Distinction in Disaster! said...

Hi

HDV needs HBsAg for assembling of its viral particle. To say simply is that HDV uses HBsAg as its envelope protein.

Although it is not clearly known, HBsAg may involve in entering of HDV into the hepatocyte (WHO).

HDV is an RNA virus and HBV is a DNA virus, so their replication mechanisms are not related.

As an RNA virus, HDV can transribe its RNA and translate it into HDAg, the protein necessary for its replication mechanism.

To wrap up, without HBsAg, HDV can neither enter the cell nor release its viral particles from the cell.

In co-infection cases, HBsAg only exists for the acute infection period (2 weeks to 3 months)or untill it is seroconverted. Thus, the motality rate for co-infection cases is 2-20%.

In superinfection cases, HBsAg exists in Hep B carriers for life. Therefore HBsAg is always available for HDV. Thus, motality rate is up to 30%.

Therfore having Hep B vaccincation is the best way to prevent from HDV infection.

Hope this will help...

Cheers

Ye Tun

VASTYJ said...

Hi there!

Any =/- control is used?
Is there any reference range for the level of anti-HD present?

Cheers! End of SIP!

Chaur Lee

Distinction in Disaster! said...

Hi Chaur Lee

Ya..SIP has ended.

Yup...the test kit includes positive & negative controls and calibrators, which are included in every run of the test. Since HDV is very rare in Singapore...it's quite hard to get in-house controls though.

As this is considered as a qualitative assay, the O.D. ratio of >1 is considered positive.

Cheers

Ye Tun

royal physicians said...

Hi,

Just wondering is the transmission route of the HDV similar to other types of hepatitis?

Tanx!

Nisha
TG02

MedBankers said...

hey ye tun,

congr! sip finally over

may i ask what is the limitation of the test? is hep D as easy detectable as hep B?

elaine

Kent said...

Hey dude,

U mentioned that the "There is no vaccine for HDV and the best way to prevent it is to avoid risk behaviors." What are some examples of risk behaviors?

Hope this one aint too tough! =P
Kent
TG01

Distinction in Disaster! said...

Hi

To Nisha question:

Yes, the route of transmission of HDV is similar to HBV. It is transmitted percutaneously,i.e. via contaminated drug use equipment or tansfusion of blood products which contains HDV, and permucosally , i.e. sexually transmitted.

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To Elaine

Ya, diagnosis of HDV is not as easy as HBV. Automation is available for HBV, but not for HDV. HDV is detected by the ELISA I mentioned in my post and it is a manual work, taking about 3 hours to get the result. And HDV infection is very serious so it puts additional risk to the lab personnel.

--------------------------------
To Kent:

Haha..ok..risk behaviours are:

injecting drug use and occupational exposure

Hemodialysis

Tansplant or tansfusion of unscreened blood products

sexual intercourse

--------------------------------

Cheers

Ye Tun

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