|Herpes Simplex Virus 1 - IgG/IgM Westernblot|
Immunoblot for the detection of IgG- or IgM-antibodies against Herpes Simplex Virus Type 1 in serum
SUMMARY AND EXPLANATION OF THE TEST
The herpes viridae comprise a large group of DNA viruses found in many species. 6 of them have been isolated in humans. 2 of these, herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2), are very similar to each other. They have 50 % homology in the genom, and the virions have many similar antigenic determinants. Both viruses can cause ano-genital as well as oral, facial and pharyngeal infections, although HSV-1 is isolated more often from the latter three locations, and HSV-2 is isolated more often from ano-genital region.
HSV-1 is usually acquired in the first 10 years of life. The larger majority of the infections follow an asymptomatic course. About 10 % of the infections are accompanied by clinical manifestations.
The primary infection may cause gingivostomatitis and/or pharyngitis, and the facial skin may also be affected. The prodromal symptoms are typical and consist of itching and tingling sensations about five days prior to the appearance of the characteristic group of vesicles on the erythematous skin. After a few days, the vesicles change into erosions and heal after 5 – 10 days forming a crust. The primary infection may be accompanied by malaise and fever. A rare but severe complication is the herpes encephalitis with a very high mortality. After the primary infection, the virus retreats to the trigeminal ganglion, where it remains latent. After reactivation, under the influence of among other things sunlight, menses, fever, emotional stress, or over-fatigue, the infection recurs and is mostly located on the lips or in the perioral region. A recurrence of herpes labialis is mostly local and has a less severe course than the first episode. However, in immunocompromised patients, reactivation may lead to a persisting progressive ulcer, accompanied by necrosis, bleeding and severe pain. Further more, after a reactivation the infection may disseminate, causing pneumonia, hepatitis, pancreatitis and encephalitis due to viraemia.
Although most genital herpes simplex virus infections are caused by HSV-2, nearly 20 % are caused by HSV-1. The severity and duration of primary genital HSV-1 or HSV-2 infections do not differ. However, the recurrence rate of HSV-1 genital herpes is much lower compared to the recurrence rate of HSV-2 genital herpes. Furthermore, the symptoms of reactivated HSV-1 genital herpes are beyond the clinical horizon in most cases. So a treatment of a HSV-1 genital herpes with Acyclovir or Zovirax, for example, seems not to be reasonable, but for HSV-2 genital herpes it is, of course. Therefore, a differentiation of both viruses, serologically or by typing in an antigen detection system, seems to be useful.
HSV-1 IgG/IgM Westernblot
Analysis of band pattern and interpretation of the results
Cut off - Standard setting: IgM - 10 %, IgG - 20 %
The following antigens can be identified by this immunoblot:
This protein is highly specific for HSV-1. Nevertheless, cross reactivity HSV-2 were rarely observed, but not to other herpes viruses. Antibody response rise 7 – 14 days after onset of the infection. The results are positive if the highly specific band 130 kD (gpC 1) is marked.
Marker for HSV infection, relatively specific. Can be observed parallel to gpC1 antibodies in many cases.
Antibodies against these proteins are early markers of a HSV infection. IgM antibodies against 40 kD and 65 kD are produced approximately between the 3rd and 7th day of the infection, and IgG antibodies after about the 7th - 10th day. They are not specific to HSV-1, but cross react to HSV-2. Therefore these antibodies can confirm a positive IgM result but not differentiate between a HSV 1 and a HSV 2 infection. These antibodies are only proof of an infection with Herpes.
The IgM response to HSV-1 is much weaker, and the weaker bands here must also be taken into consideration.
The antibodies against the highly molecular glycoproteins - 130 kD (gpC 1) - are only produced after the 7th – 14th day, and only then is it possible to differentiate between the two Herpes types. Antibodies against the high molecular weight proteins are produced after 7 - 14 days. If these antibodies are missing in the first sample, a second should be drawn some days later for a differentiation.
A positive HVS-1 result can be reported if the specific gpG1 (130 kD) band is labeled. IgM-antibodies against the 40 kD and 65 kDa are the earliest response after the onset of infection. They can be observed after 3 - 7 days. The corresponding IgGs antibodies rise after 7 – 10 days. Unfortunately, those antibodies allow no differentiation between both Herpes simplex viruses.
LIMITATIONS OF USE
A correlation between band pattern and intensity and the severity of disease is not possible. A negative result does not preclude the possibility of a recent infection. If clinical signs can be found, an IgM test is recommended. If both tests are negative an additional sample should be taken after 6 to 8 days from this patient to exclude a delayed antibody response.