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HHV-6
The disease and Panbio product training
Overview
• First isolated in 1986 from patients with AIDS
• The main clinical syndrome associated with the virus,
roseola infantum, was first reported in 1913
• It wasn’t until 1988 that the link between HHV-6 and
roseola infantum was established.[1]
• Ubiquitous virus which causes disease in both normal
and immunocompromised individuals
• HHV-6 is a viable candidate as a possible etiological
agent in multiple sclerosis.
Infectious Agent
• Belongs to the Betaherpesvirus subfamily and
genetically similar to HHV-7 and CMV
– cross reactivity between HHV-6 and CMV is quite
common[2].
• Two distinct variants - HHV-6A and HHV-6B
– Can be differentiated using monoclonal antibodies and PCR
• Incubation period about 10 days
Epidemiology
• Approximately 90% of normal children are infected
during infancy, with the peak age of 6-9 months.[1]
• In Western populations most children are infected by
the age 3 years, and the majority of these with HHV6B.[2]
• Transmission via saliva from infected individuals, blood
transfusion and organ transplantation.[4]
• Incidence is greatest in Spring
Pathogenesis
• CD4+ T-lymphocytes are the preferential cell for HHV6 to infect, with the surface marker CD46 acting as
part of a co-receptor for infection.[5] This in turn results
in a number of significant effects on the immune
system.
• HHV-6 infection persists for an extended period, with
the virus able to establish latency in a number of
different cells and organs.
Clinical Notes
Infection in childhood
• Exanthema subitum (Roseola infantum or sixth
disease)
– Occurs in infants
– High fever that lasts 3-5 days
– Maculopapular rash (Physicians can mistake these signs for
allergic reactions to antibiotics.[1] )
– Associated with febrile convulsions in 12-15 month old
children.
– Febrile form usually self-limiting and does not require
specific therapeutic intervention
Clinical infection
Immunocompromised patients
• Reactivation of HHV-6 infection may result in fever,
skin rash, pneumonitis, encephalitis and even bone
marrow suppression.
• Reactivation in bone marrow transplant patients has a
particularly high incidence of 48%.[1]
• High frequency of HIV-infected patients that suffer from
HHV-6 reactivation resulting in pneumonitis and
encephalitis.
• HHV-6 has been increasingly associated with
conditions such as MS and malignancies such as
Hodgkin’s disease, non-Hodgkin’s lymphoma, acute
lymphoblastic leukaemia, oral carcinoma and cervical
carcinoma.
Antibody Response
• Although many newborns maternally acquire HHV-6
antibodies they become seronegative by 6 months.
• Antibody levels may be elevated in patients with
infectious mononucleosis (IM), chronic fatigue,
Hodgkin's disease & oral and cervical carcinoma.
• Primary infection
– IgM detectable 5-7 days after febrile phase of Roseola
– IgG appears 7-10 days after the febrile phase of Roseola
and usually persists for life.
Diagnosis
• Clinically may be confused with measles and rubella
because of similar rash.
• Laboratory confirmation essential to ensure
effectiveness of measles and rubella surveillance
programs.
• Diagnostic tests
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IFA
Viral isolation
PCR
ELISA
Why Test for HHV-6?
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Ubiquitous virus that causes a wide range of disease.
Because it is common, immunocompromised patients are
more likely to come into contact with individuals who are
suffering from primary HHV-6 infection.
Transplant patients who are being medicated against graft
rejection are particularly susceptible.
HIV-infected individuals are also susceptible.
Whilst HHV-6 usually causes a benign, self-limiting disease
in children, there are a number of cases that progress to
serious life-threatening states of the disease.
As IgM to HHV-6 can cross react with a number of other
viral antigens such as CMV and EBV, testing of both HHV-6
IgG and IgM affords the physician with a clearer picture as
to whether an individual preparing to undergo
transplantation is at risk of reactivation or primary infection.
Diagnostic Tests
• Virus isolation
– has been successful in primary infections, usually when
rash is present.
– time-consuming
• PCR
– useful for variant discrimination
– useful in viremic part of disease - usually first 3-4 days after
illness only
• IFA
– useful for confirmation and small scale testing
• ELISA
– for IgG and IgM antibodies
– use in conjunction with IFA for confirmation
Diagnostic Tests
Virus Isolation
PCR
IgM
ELISA or IFA
IgG
ELISA or IFA
Panbio HHV-6 IFA Products
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HHV-6 IgG IFA kit
HHV-6 IgG IFA kit
HHV-6 IgM IFA kit
HHV-6 IgM IFA kit
HHV-6 IFA Slides
120T
40T
120T
40T
10x10well
Cat# I-HV601G
Cat# I-HV603G
Cat# I-HV601M
Cat# I-HV603M
Cat# I-HV601X
Panbio HHV-6 IgG and IgM IFA
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Bright green fluorescent staining = positive
Fluorescent staining pattern of HHV-6 infected cells is
variable.
– Depending on the cell’s stage of infection, the fluorescent pattern
can vary from a small portion of the infected cell fluorescing to the
whole cell fluorescing.
– Fluorescence can also range from granular to homogeneous.
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To provide an internal control, each well contains both HHV6 infected and uninfected cells. Preparation of the slide in
this manner is intentional.
– Uninfected cells, stained red by the counterstain, provide a
contrasting background.
– Infectivity of the cells ranges from 20% - 60%.
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Absence of specific fluorescent staining of the infected cells
denotes a negative reaction.
HHV-6 IgG IFA performance
• Dr. Theo Sloots, Clinical Virology Research Unit, Sir
Albert Sakzewski Virus Research Centre (SASVRC),
Royal Children’s Hospital, Qld, Australia.
• Sample population
1. Blood donors (n=23)
2. Acute sera from children with proven HHV-6 infection
(n=22)
3. Convalescent sera from children with proven HHV-6
infection (n=35)
• Agreement of 95% (76/80)
Panbio HHV-6 IgM ELISA
• HHV-6 IgM ELISA Cat # E-HV601M
• For the presumptive qualitative detection of IgM to
HHV-6 in serum as an aid in the clinical laboratory
diagnosis of primary of reactivated HHV-6 infection in
patients presenting clinical symptoms consistent with
HHV-6 infection.
Panbio HHV-6 IgM ELISA
Performance
• Package insert
• Study 1
– 149 serum samples (98 Aust blood donors and 40 positives
characterised by in-house IFA)
– Serological sensitivity = 52.5%
– Clinical specificity = 87.8%
– Relative agreement = 77.5%
• Cross reactivity
– Cross reactivity observed with CMV and EBV primarily
Panbio HHV-6 IgG ELISA
• HHV-6 IgG ELISA Cat # E-HV601G
• For the qualitative detection of IgG to HHV-6 in serum
as an aid in diagnosis of recent or past exposure to
HHV-6
• Paired sera required to determine recent infection if
using IgG alone
Panbio HHV-6 IgG ELISA
Performance
• Sloots et al., 1996, J. Clin. Micro
– Sensitivity 99.8%, Specificity 98.8%
• Package insert
– 212 serum samples characterised by public hospital
lab’s in-house IFA
– Clinical sensitivity = 97.4%
– Serological specificity = 86.0%
– Serological agreement = 94.3%
Comments from Dr Sloots
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The kit was easy to use and reagents were adequate
Good cell numbers were present per well
Strong apple-green fluorescence was present at 4+
The fluorescence of positive reactions (4+ to 1+) was
easily discriminated from the negative reaction
• The percentage of infected cells per field was high
(70%)
Further performance data is found in the HHV-6 IgG
IFA package insert
Promotional Resources
• Clinical notes sheet
• Colour brochure – in process of being updated
• Publications
– General
– Panbio HHV-6 IgG ELISA
References
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Abdel-Haq, N.M., Asmar Basim, I. (2004). Human herpesvirus 6 (HHV6) infection.
The Indian Journal of Pediatrics. 71(1):89-96.
Irving, W.L., et al. (1990). Dual antibody rises to cytomegalovirus and human
herpesvirus type 6: frequency of occurrence in CMV infections and evidence for
genuine reactivity to both viruses. Journal of Infectious Diseases. 161(5): 910-916.
Caserta, M.T., Mock, D.J., Dewhurst, S. (2001). Human herpesvirus 6. Clinical
Infectious Diseases. 33(6): 829-833.
Okuno, T., et al. (1989). Seroepidemiology of human herpesvirus 6 infection in
normal children and adults. Journal of Clinical Microbiology. 27(4): 651-653.
Lau, Y.L., et al. (1998). Primary human herpes virus 6 infection transmitted from
donor to recipient through bone marrow infusion. Bone Marrow Transplant. 21(10):
1063-1066.
Santoro, F., et al. (1999). CD46 is a cellular receptor for human herpesvirus 6.
Cell. 99(7): 817-827.
Steeper, T.A., et al. (1990). The spectrum of clinical and laboratory findings
resulting from human herpesvirus-6 (HHV-6) in patients with mononucleosis-like
illnesses not resulting from Epstein-Barr virus or cytomegalovirus. American
Journal of Clinical Pathology. 93(6): 776-783.
Dockrell, D.H., Paya, C.V. (2001) Human herpesvirus-6 and –7 in transplantation.
Reviews in Medical Virology. 11(1): 23-36.