Is there a relationship between of viral load and co-infections of respiratory viruses with disease severity in patients with acute respiratory tract infection?

Abstract

No: 1527 Presentation at ESCV 2015: Poster 1 Serological diagnosis of mumps -The benefit from IgA antibody screening and IgG antibody avidity testing in the population of the Czech Republic with a high vaccination coverageBackround: Although the Czech Republic is among the countries with a high vaccination coverage, mumps cases have recently been on the rise, even in the vaccinated population. The present study addresses the question of whether the increase in postvaccination mumps cases is the result of primary or secondary vaccine failure -by comparing IgG antibody avidity and IgM and IgA antibody levels in acute sera in vaccinated versus naturally immunized patients.Methods: Sixty-four patients with laboratory confirmed mumps (by direct detection of the virus and/or significant increase in anti-mumps antibodies) were included in the study. Of this cohort, 38 were vaccinated (36 acute sera were analyzed) and 26 were non-vaccinated (23 acute sera were analyzed). Altogether 26 convalescent sera were available from vaccinated and nonvaccinated subjects. The control groups were 30 healthy, naturally immunized adults and 22 vaccinated, healthy children aged 2-4 years. To measure the avidity index, the Siemens Enzygnost Anti-Mumps/IgG kit with 6 M urea was used. IgM, IgG, and IgA antibodies were detected using the Siemens Enzygnost Anti-Mumps/IgM and/IgG and Mast Diagnostica Mastazyme Mumps IgA kits.Results: High avidity antibodies were only detected in convalescent sera from vaccinated subjects or in those who became naturally immunized as a result of recent infection. In contrast, none of the controls had high avidity antibodies. Based on the screening of acute sera, the infection was laboratory confirmed by the detection of IgA antibodies in 56% (20/36) of cases and by the detection of IgM antibodies in 36% (13/36) of cases only. Of 23 non-vaccinated patients, 87% (20/23) showed IgA positivity and 74% (17/23) IgM positivity.Conclusion: High incidence of post-vaccination mumps cases is very probably the result of secondary vaccine failure. Testing both convalescent and acute sera for IgG antibody avidity is of diagnostic benefit. Nevertheless, the acute sample of blood should be collected not earlier than on day six of the onset of symptoms when significant increase in antibody avidity is observed in both vaccinated and naturally immunized subjects. The highest detection rate of mumps virus infection was achieved by testing IgA antibodies. The addition of this serological method to the standard detection of IgM antibodies improved the mumps diagnosis rate, particularly in vaccinated patients.