|
Biotrin Human Herpes Virus 8 Products
Frequently Asked Questions 1. What is HHV 8? Human Herpes Virus 8 (HHV 8) is also known as Kaposi’s sarcoma associated herpes virus or KSHV. It is the causative agent of Kaposi’s Sarcoma (KS), a tumour. It was first identified in 1994 when HHV 8 DNA was isolated from KS lesions. The Virus has also been associated with other lymphoproliferative disorders such as Burkitt’s lymphoma, Castleman’s disease (form of lymph node enlargement), body cavity lymphoma, non-hodgkin’s lymphoma and multiple myeloma. Infection with this virus is thought to be life-long, but a healthy immune system will keep the virus in check. KS occurs when someone who has been infected with KSHV becomes immunocompromised due to AIDS, old age or medical treatment. 2. How prevalent is HHV 8? KSHV is an uncommon infection in industrialised countries such as North America/North Europe, where less than 2% of the general population is infected with the virus.
The virus is more frequent is some Mediterranean countries such as Italy and Greece (4-35%), while it is widespread in Africa (30-60%). The burden of KS is high in Africa, where KS accounts for almost half of all reported cancers in certain countries including Uganda.
3. What groups are most at risk to this virus?
African populations are at risk to this virus due to the high prevalence of the virus. It is thought that infection in Africa is spread through non-sexual routes that remain poorly understood. Gay and bisexual men are at high risk for infection with up to 60% of gay men found to be infected in some studies. Among gay men, the incidence increases with the number of sex partners. The exact reasons why gay men are at high risk for infection compared to heterosexuals remains unknown, although it has been suggested that men in general may be more susceptible to the virus and therefore more likely to transmit it to male sex partners. HHV 8 infection is also of particular concern to individuals receiving organ transplants. Not only is there a risk of transmitting the virus from the donated organ, but recipients are immunosuppressed to avoid organ rejection and are at high risk for developing KS if they are infected. Some studies found that up to 50% of transplant recipients who are infected with HHV-6 develop KS. This can cause loss of the donated organ and be life-threatening.
4. Who should be tested for HHV 8? 5. What is Kaposi’s sarcoma (KS)? It is a tumour caused by the Human Herpes Virus 8 (HHV8) in which cancerous cells, as well as abnormally growing blood vessels, form solid KS lesions in connective tissue. KS lesions are nodules or blotches that may be red, purple, brown, or black, usually painless but sometimes painful and swollen. They most often appear under the surface of the skin or on mucous membranes, where they are only dangerous if they cause enough swelling to obstruct circulation, breathing, or eating. They may also be found in internal organs, particularly the respiratory system or gastrointestinal system; internal lesions are most commonly seen in epidemic KS, and can cause fatal bleeding. Kaposi's sarcoma occurs when someone who has been infected with KSHV becomes immunocompromised due to AIDS, old age or medical treatment.
6. How is HHV 8 transmitted?
In African countries, infection is commonly spread through non-sexual routes that remain poorly understood. Young children can be infected (although direct transmission from mothers to their children during pregnancy is uncommon), and rates of infection can continue to increase throughout adulthood. A form of Kaposi's sarcoma occurring in young African children due to this infection is almost uniformly and rapidly fatal. Infections with HHV 8 are generally asymptomatic. People infected with KSHV will asymptomatically shed the virus and caution should be used by sex partners in having unprotected sex and activities where saliva might be shared such as deep-kissing. Unlike HIV, it is not clear whether the virus is transmitted through unprotected anal intercourse. Instead, it is likely that it is transmitted between sex partners by oral secretions (e.g. saliva).
7. How are HHV 8 infections treated?
Infection with this virus is thought to be a life-long infection, however a healthy immune system will keep the virus in check. KS or other disorders occur when someone who has been infected with HHV 8 becomes immunocompromised. The most effective treatment is treatment is of the underlying immunodeficiency. Antiviral drugs, such as ganciclovir, that target the replication of herpesviruses such as KSHV have been used to successfully prevent development of KS, although once the tumor develops these drugs are of little use. For patients with AIDS-KS, the most effective therapy is highly active antiretroviral therapy to reduce HIV infection. AIDS patients receiving adequate anti-HIV treatment may have up to a 90% reduction in Kaposi's sarcoma occurrence. There is no vaccination available for this virus.
8. What is Sirolimus and what effect does it have on HHV 8 and KS?
Sirolimus, also called Rapamycin is an immunosuppressant drug that is used to prevent rejection in organ transplantation, and is especially useful in kidney transplants. Sirolimus inhibits its molecular target (the mammalian target of sirolimus is mTOR), which links mitogen-induced stimulation of protein synthesis and cell-cyle progression by activating p70S6 kinase, a key enzyme in regulating gene translation. Inhibition of mTOR prevents acute graft rejection by inhibiting the interleukin-2-induced proliferation of T cells. Studies have shown that Sirolimus inhibits the evolution of KS when given at the usual immunosupression doses following organ transplantation without compromising graft function. It is of yet unclear if sirolimus modifies HHV 8 levels in KS patients, and long term studies on the efficacy of sirolimus in KS patients is unavailable.
9. What kits do Biotrin have to detect this virus?
Biotrin have two serology-based kits for the diagnosis of HHV-8: Both kits qualitatively and semi-quantitatively detect Human Herpesvirus-8 IgG Lytic antibodies in human serum or plasma.
10. How do I store and transport the Biotrin kits?
The kit and components should be stored and transported at 2-8oC
The kit and components should be stored and transported at 2-8oC
11. How sensitive and specific are the Biotrin kits? Sensitivity: 100%
Specificity: 94%.
Sensitivity: 90.4%
Specificity: 93%.
Additional information on how these values have been calculated is located in the Performance Characteristics section of the IFU documents. Alternatively, the information is available on request.
12. What sample types can I use on the Biotrin HHV 8 kits?
Human Serum or Plasma can be used on the Biotrin kits. To optimise sensitivity, fresh samples are the preferred sample type. However samples may be frozen at -20oC if extended storage or shipment is required (samples are stable at -20oC for at least 1 year). Please follow the specimen preparation section in the Instructions for use when collecting and preparing patient specimens.
13. What sample size do I need to run the Biotrin kits?
Qualitative Test: Dilute the sample 1:64 in Wash Buffer. Prepare all dilutions in a minimum volume of 100 uL Wash Buffer. This requires a minimum sample size of 1.6 uL.
Quantitative Test: The sample ‘titre’ can be determined by preparing two-fold serial dilutions of the sample in Wash Buffer, starting with a 1:64 dilution, and adding equal volumes of diluted sample and Wash Buffer for each consecutive dilution, until a ‘+1’ grade of fluorescence is achieved.
A minimum of 10 uL of serum or plasma sample is required to run each assay.
14. How many samples can I test on the Biotrin kits? The kit contains 6 x 10 well slides and this allows you to complete 60 tests.
The kit contains a 96 well plate, which allows you to test 46 samples in duplicate or 92 samples in singleton. A positive and negative control is included in this kit
15. Why should I use serology/immunological tests instead of PCR?
HHV-8 DNA can be detected in peripheral blood cells from only about half of infected persons with the use of standard PCR assays Since PCR detection systems appear to exhibit low sensitivity when DNA from peripheral blood cells is used as a template, serological assays have been proven more useful for epidemiology studies and diagnosis of HHV-8 infection, particularly for detecting previous exposure to the virus. The difference in the serology/PCR detection rate of this virus is displayed in the table below Patient Group Serology detection rate PCR detection rate
HIV positive patients with KS 80-97% 40-50%,
HIV positive patients who developed KS within 5 years of specimen collection 54-100% 30%
Patients who did not develop KS. 16-56% 5 -10%
It is clear from these results that PCR detection is less sensitive than serology testing for HHV 8 detection.
16. Should I measure lytic or latent antibodies?
The HHV 8 virus like all Herpes viruses has the ability to enter into a latent dormant stage in an individual after the primary infection. Infection with HHV 8 is lifelong and the virus can remain in the latent stage for many years. The virus can become reactivated in an individual as a result of an immune response, another infection and a chemical or physical agent e.g.: UV light. During this active phase, thousands of virus particles can be made from a single cell, which usually results in cell death. The active replication phase of the virus lifecycle is called the lytic phase. HHV 8 can cause a range of complications for an individual during its lytic phase. It is important that HHV 8 IgG lytic antibodies are measured as this will let the clinician know that the viral infection is active and allow them to treat the patient appropriately. Both Biotrin HHV 8 kits detect HHV 8 Lytic antibodies. 17. Why do I get different results from an EIA to an IFA kit?
Typically an IFA is a more subjective assay. The interpretation of results will depend on the technique and skill of the laboratory technician who is viewing the sample slides under the microscope.
IFA assays, being a test using cellular methods may also pick up low level antibody titres that may be not picked up on the EIA, as the assay is based on peptides only. This can lead to slightly more sensitive results being obtained with an IFA assay compared to an EIA assay.
EIA technology offers other benefits to the customer including: increased suitability for larger volumes, objective sample reading, generally a reduced cost per test. Finally, the technician completing the test does not need as much skill to interprete the results compared to the interpretation of IFA slides. |
