What is the relationship between Parvovirus (Parvovirus B19) and granulocytes (white blood cells)?

From the Guidelines

Parvovirus B19 infection can cause severe anemia and hydrops fetalis in fetuses due to its direct effect on erythroid progenitor cells in the bone marrow, and treatment typically involves fetal intrauterine transfusion. When parvovirus infects the bone marrow, it targets erythroid progenitor cells, leading to inhibition of erythropoiesis and subsequent anemia 1. The risk of a poor outcome for the fetus is greatest when the congenital infection occurs in the early second trimester (<20 weeks of gestation) 1. The relationship between parvovirus and granulocytes is also important, as parvovirus can affect granulocyte production, leading to decreased neutrophil counts 1. Some key points to consider in the management of parvovirus infection include:

• Fetal intrauterine transfusion is recommended for nonimmune hydrops fetalis (NIHF) due to parvovirus infection, unless the pregnancy is at an advanced gestational age and risks associated with delivery are considered to be less than those associated with the procedure 1.
• The diagnosis of parvovirus infection can be made by detection of the virus in fetal blood or amniotic fluid using polymerase chain reaction (PCR) 1.
• The risk of fetal death has been reported to be 15% at 13-20 weeks of gestation, and 6% after 20 weeks 1.
• In cases of severe infection with neutropenic fever, empiric broad-spectrum antibiotics should be initiated promptly while awaiting culture results 1.
• Granulocyte colony-stimulating factor (G-CSF) at 5-10 μg/kg/day subcutaneously may be considered in severe cases to stimulate neutrophil production, though its efficacy specifically for parvovirus-induced neutropenia is less established than IVIG 1.

From the Research

Parvovirus Infection and Granulocytes

• Parvovirus B19 infection can cause pure red-cell aplasia, resulting in chronic or recurrent anemia with reticulocytopenia 2
• The infection can be treated with intravenous immunoglobulin (IVIG), which can help restore erythropoiesis and make the patient transfusion independent 3
• Recombinant canine granulocyte-colony stimulating factor (rcG-CSF) has been shown to be effective in stimulating neutrophil recovery and shortening the duration of hospitalization in dogs with parvovirus infection 4
• Parvovirus B19 is highly tropic to human bone marrow and replicates only in erythroid progenitor cells, causing pure red cell aplasia and chronic anemia in immunocompromised patients 5
• IVIG therapy has been shown to be effective in treating pure red cell aplasia related to human parvovirus B19 infection, with a response rate of 93% in immunocompromised patients 6

Treatment Options

• IVIG therapy is a common treatment option for parvovirus B19 infection, especially in immunocompromised patients 2, 3, 6
• Red-cell transfusion and adjustment in medications to restore or improve the patient's immune system are also treatment options 2
• Recombinant granulocyte-colony stimulating factor (G-CSF) may be used to stimulate neutrophil recovery in patients with parvovirus infection 4

Diagnosis and Prognosis

• Diagnosis of parvovirus B19 infection is established by detection of B19 DNA in serum in the absence of IgG antibody to B19 2
• Bone-marrow examination may show giant pronormoblasts or absence of red-cell precursors 2
• Prognosis is generally good with treatment, but patients with underlying hemolytic disorders or immunocompromised status may have a poorer prognosis 2, 5