1.What is HHV-6?

Human Herpes Virus 6 (HHV-6) is a β-herpes virus which was first isolated in 1986 from the peripheral blood of 6 patients with a variety of lymphoproliferative disorders, some of whom had AIDS.

The virus has worldwide distribution with infection generally occuring within the first two years of life. It is the cause of childhood illnesses known as “6th Disease” or “Roseola Infantum”. The symptoms of this primary infection may begin with the child experiencing a sudden high fever (39 - 40oC). This sudden rise in temperature can in some cases lead to febrile convulsions.  After a few days, the fever subsides and a red rash appears on the child’s body. The rash disappears within twenty four hours.

It is estimated that HHV-6 is the single most common cause (10 – 40%) of children presenting to hospitals with a rash.

After the primary infection, the virus establishes a dormant latent infection in the individual for life. Re-activation of the virus can occur if the individual becomes immuno-compromised. Re-activation has been reported to be relatively common after solid organ and stem-cell transplantation.

These re-activations can cause skin rashes, hepatitis, bone marrow suppression, interstitial pneumonitis and encephalopathy. In some cases, the virus has been shown to cause allograft dysfunction.

HHV-6 is also thought to play a role in a number of diseases, including, the progression from HIV to AIDS, Multiple Sclerosis, Chronic Fatigue Syndrome and other neurologically-related disorders. Further study is required in these areas.

Two genetically distinct variants of human herpesvirus 6 have been discovered: Human Herpesvirus 6A (HHV-6A) and Human Herpesvirus 6B (HHV-6B).

HHV-6A has not been shown to cause any diseases; HHV-6B, unlike HHV-6A, has been associated with a variety of viral illnesses, including, exanthem subitum (roseola infantum), mononucleosis syndromes, focal encephalitis, and pneumonitis.

2. How prevalent is HHV-6?

HHV-6 is highly seroprevalent and studies have shown that the virus is present in almost 100% of the general population. Primary infection generally occurs within the first 2 years of life. HHV-6 has a worldwide distribution.

3. What groups are most at risk to this virus?

Almost all individuals become infected with HHV-6 before they reach 2 years of age. As a result, primary HHV-6 infections in adults is rare. After the initial infection during childhood, the virus establishes a lifelong infection whereby it enters into a latent stage. HHV-6 may reactivate if the individual becomes immuno-compromised.

These re-activations can cause skin rashes, hepatitis, bone marrow suppression, interstitial penumonitis and encephalopathy. In some cases, the virus has caused early and late solid organ rejection.

4. Who should be tested for HHV-6?

• Young children with a rash or who have suffered from a febrile convulsion
  
  
• Transplantation donors & recipients
  
  
• Research groups working on the association between HHV-6 and MS, CFS, Carcinoma, HIV and a range of other illnesses.

Biotrin are always interested to hear from research groups working in these areas. Please contact us at info@biotrin.ie with details of your work on HHV-6.

5. What is 6th disease, Exanthum Subitum and Roseola Infantum?

Exanthum Subitum (meaning sudden rash), is also referred to as roseola infantum (or rose rash of infants) and sixth disease. It is a childhood disease that affects most children by 2 years of age.

HHV-6 and HHV 7 are known to be the causative agents of this childhood disease.

Typically, Roseola affects a child between the ages of six months and three years of age. It begins with a sudden high fever of 102-104 degrees Fahrenheit (39-40 degrees Celsius). This can cause, in some cases, febrile convulsions due to the sudden rise in body temperature, but in many cases the child appears and acts normal. After a few days the fever subsides, and just as the child appears to be recovering, a red rash appears. This usually begins on the trunk, spreading to the limbs but usually not affecting the face. It disappears again after a few hours to a day.

In contrast, a child suffering from measles would usually appear more infirm, with symptoms of conjunctivitis, a cough, and their rash would affect the face and last for several days.

6. How is HHV-6 transmitted?

Transmission occurs via saliva from infected individuals, blood transfusion and organ transplantation.

7. How are HHV-6 infections treated?

There is no specific vaccine or treatment for HHV-6 infections. Most children with the disease are not seriously ill but steps should be taken to alleviate their symptoms e.g. reducing the high temperature through maintaining hydration and removing clothing.

8. What kits do Biotrin have to detect this virus?

Biotrin have three serology-based kits for the diagnosis of HHV-6:

• HHV-6 IgG Immunofluorescent Assay (Cat. No. V3HHV6)
  
  
• HHV-6 IgM Immunofluorescent Assay (Cat. No. V17HHV6)
  
  
• HHV-6 IgG Enzyme immunoassay (Cat. No. V15HHV6)

IgG Antibodies appear 7-10 days after the febrile phase of Roseola and they    usually   persist at low levels for life. Detection of IgG antibodies is useful for determining immune status and active infection

IgM Antibodies are detectable 5 – 7 days after the febrile phase of Roseola. IgM antibodies are the first antibodies to appear in response to an initial exposure to the HHV-6 antigens. Detection of high IgM antibodies in a patient sample indicates a recent infection.

9. How do I store and transport the Biotrin kits?

All Biotrin HHV-6 kits are transported and stored at 2 – 8oC.

10. How sensitive and specific are the Biotrin kits?

• HHV-6 IgM Immunofluorescent Assay (Cat. No. V3HHV6)
  
  Sensitivity = 100%
  
  Specificity = 99%
  
  
• HHV-6 IgG Immunofluorescent Assay (Cat. No. V17HHV6)
  
  Sensitivity = 100%
  
  Specificity = 94%
  
  
• HHV-6 IgG Enzyme immunoassay (Cat. No. V15HHV6)
  
  Sensitivity = 97.4%
  
  Specificity = 86%

Additional information on how these values have been calculated is located in the Performance Characteristics section of the Instructions for use documents. Alternatively, the information is available on request.

11. What sample types can I use with the Biotrin HHV-6 kits?

Human Serum or Plasma can be used with the Biotrin HHV-6 IFA 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).

Only Human Serum has been validated for use with the Biotrin HHV-6 IgG EIA kit.

Please follow the specimen preparation section in the IFU when collecting and preparing patient specimens.

12. How many samples can I test on the Biotrin kits?

• HHV-6 IgG Immunofluorescent Assay (Cat. No. V3HHV6)
  The kit contains 6 x 10 well slides and this allows you to complete 60 tests.
  
  
• HHV-6 IgM Immunofluorescent Assay (Cat. No. V17HHV6)
  The kit contains 6 x 10 well slides and this allows you to complete 60 tests.
  
  
• HHV-6 IgG Enzyme immunoassay (Cat. No. V15HHV6)
  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.

Testing samples in duplicate is recommended.

13. Why should I use a serology test instead of PCR?

As almost 100% of the population are sero positive for HHV-6, it is important to distinguish latent HHV-6 infections from active infections. PCR will detect HHV-6 viral DNA but it is unable to diagnose active or latent infections. As the virus is so prevalent, serology assays remain the assays of choice to accurately diagnose active  infections with a high level of sensitivity.

Chromosomal integration of HHV-6 has also been shown in immuno-compromised patients, where high levels of HHV-6 viral DNA were reported in blood samples.   These high levels may be misinterpreted by PCR as active infections. 

14. Why do I get slightly different results on 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 may also pick up low level antibody titres that may be not picked up on the EIA. 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.

Please contact us  if you have any further questions on the Biotrin HHV-6 range