VZV (Varicella Zoster Virus) IgG antibodies

What causes Chickenpox and shingles?

Both chickenpox and shingles result from an infection with the varicella-zoster virus (VZV), which belongs to the herpes virus family. Tests for varicella zoster virus aim to identify either antibodies generated by the immune system as a response to a VZV infection or the presence of the virus itself.

What do tests show for chickenpox and shingles?

Testing for chickenpox and shingles serves several purposes:

1. To identify and diagnose current or past VZV infections.
2. Typically, active infections can be diagnosed based on clinical signs and symptoms, but in cases with unusual skin lesions, diagnostic tests can provide confirmation.
3. For specific populations like organ transplant recipients and pregnant women, these tests may be used to diagnose current infections or assess immunity resulting from prior infection or vaccination.

Do chickenpox and shingles cause severe symptoms?

Chickenpox and shingles typically resolve without complications. However, in individuals with weakened immune systems, such as those with HIV/AIDS or organ transplants, the diseases can become more severe and long-lasting. In some cases, they may not go dormant and could spread to the central nervous system.

In pregnant women, the impact of VZV exposure on a developing fetus or newborn varies depending on the timing and the mother's previous exposure to the virus. If a primary VZV infection occurs during the first 20 to 30 weeks of pregnancy, it may, although rarely, lead to congenital abnormalities in the unborn baby. If the infection occurs one to three weeks before delivery, the newborn may develop chickenpox after birth, but they could have some protection from maternal antibodies. However, if a newborn is exposed to VZV at birth without maternal antibody protection, the infection can be life-threatening.

How can the Varicella zoster virus reactivate?

After the primary infection has cleared, the virus enters a dormant phase, residing within sensory nerve cells. During the initial infection, the individual typically develops antibodies that protect against future chickenpox infections. Nevertheless, in later stages of life and among individuals with compromised immune systems, the virus may reactivate. It travels along nerve cells to reach the skin, resulting in the development of shingles, also known as herpes zoster.

What are the symptoms of shingles?

Shingles often manifests with symptoms such as a mild to severe burning or itching sensation along a specific band of skin, typically around the waist, face, or another localized area. While it usually occurs on one side of the body, it can sometimes affect multiple regions. Several days after the onset of pain, itching, or tingling, a rash develops in the same area, sometimes accompanied by fluid-filled blisters (vesicles). The rash and pain improve for most individuals within a few weeks, and the virus returns to a dormant state. However, some people may experience lingering pain for several months.

How can tests detect and measure the level of VZV antibodies in the blood?

Upon exposure to VZV, the individual's immune system initiates a response by generating antibodies against the virus. Laboratory tests are capable of identifying and quantifying two types of VZV antibodies present in the blood: IgM and IgG.

**IgM antibodies** are the first to appear in response to a VZV infection, typically emerging in most individuals within a week or two following initial exposure. IgM antibody production surges for a brief duration and then diminishes. Eventually, the level (titer) of VZV IgM antibodies usually falls below detectable thresholds. In cases of VZV reactivation from latency, additional IgM antibodies may be produced.

In contrast, **IgG antibodies** are generated by the body several weeks after the initial VZV infection and confer long-lasting immunity. IgG levels increase during the active infection, stabilize as the VZV infection resolves, and the virus enters a dormant state.

Following exposure to VZV, an individual will retain a detectable level of VZV IgG antibodies in their bloodstream throughout their lifetime. VZV IgG antibody testing, in conjunction with IgM testing, can be employed to identify a recent or prior VZV infection.

What does the test result mean?

When both VZV IgG and IgM antibodies are detectable in an individual with symptoms, it is probable that the person has either recently encountered VZV for the first time, resulting in chickenpox, or that a previous VZV infection has reactivated, leading to shingles.

If only IgM antibodies are present, the infection may have occurred very recently. In the case of a newborn with IgM antibodies, it indicates a congenital VZV infection. However, if a symptomatic individual has low or undetectable levels of IgG and/or IgM antibodies, it could signify either a condition unrelated to VZV or an abnormal immune response where VZV antibodies are not being produced at a detectable level.