Blood Donor Plasma Screened for Viral Antibodies

An enzyme immunoassay kit revealed that a proportion of blood donors in France have been exposed to the Toscana virus (TOSV).

The presence of immunoglobulin G (IgG) and IgM against TOSV in the plasma of the donors suggests a potential risk for transmitting the virus through blood transfusion or organ transplantation.

Scientists at the University of the Mediterranean, (Marseille, France), tested the plasma collected from 729 blood donors in seven French territorial divisions during the summer of 2007 for the presence of TOSV antibodies. A commercial enzyme immunoassay (EIA) kit was developed by using the recombinant nucleocapsid (N) protein of TOSV. This serologic test had been validated in a previous study that revealed high specificity and sensitivity.

The results showed that 84/729 (11.5%) plasma samples were positive for IgG against TOSV N protein. Twenty-four (3.3%) plasma samples were positive for IgM and five (0.7%) were positive for both IgG and IgM. To confirm the results, the IgG-positive samples were further subjected to Western blot (WB) analysis by using the TOSV isolate H/IMTSSA infected cell lysate. In 233 (32%) of the samples, protein of molecular mass compatible with that of the N protein was detected.

To detect TOSV ribonucleic acid (RNA), the investigators processed IgM-positive plasma samples by reverse transcription–polymerase chain reaction (RT-PCR). The finding of IgM is an indication of a recent exposure to the virus and hence its possible presence in blood. The RT-PCR did not detect any viral RNA in the samples. These negative results could indicate either cleared viremia or a low viral load, below the sensitivity limit of the test. TOSV prevalence in Corsica, an island in the Mediterranean Sea, was unexpectedly high. In this region, 10 of the 115 donors, (8.7%), of the population sampled showed an IgG- or IgM-positive response. In the other districts, the IgM seroprevalence did not exceed 4.4%.

The commercial enzyme immunoassay kit used is known as the EIA Enzywell Toscana virus IgG and IgM, and produced by DIESSE Diagnostica Senese S.p.A.; Siena, Italy).

Toscana virus is an arthropod-borne RNA virus (family Bunyaviridae and genus Phlebovirus) transmitted by phlebotomine sand flies in Mediterranean countries. TOSV causes acute meningitis and meningoencephalitis in patients. The study was published in May 2011, in the journal Emerging Infectious Diseases.

Related Links:
University of the Mediterranean
DIESSE Diagnostica Senese S.p.A