Evaluation of Antibodies against a Rubella Virus Neutralizing Domain for Determination of Immune Status

Abstract

The protective immune responses against rubella virus (RV) are related to its neutralizing epitopes, an issue that is important to consider when assessing the immune status of patients with remote infection. In the present paper, we compare the antibodies detected by a synthetic-peptide-based enzyme immunoassay (EIA) with antibodies detected by the traditional technique of hemagglutination inhibition (HIA) in patients with remote RV infection. The synthetic peptide used as an antigen (SP15) represents a neutralizing epitope that corresponds to amino acids 208 to 239 of the E1 glycoprotein. The SP15-EIA was developed, all variables that affected the assay were standardized, and the test was validated using reference sera. Serum samples (n ‫؍‬ 129) from patients with remote RV infection were tested by HIA and SP15-EIA. Discrepant sera were assayed by MEIA (IMX/Abbot). The comparison between HIA and SP15-EIA, taking HIA as the standard methodology for determining immune status, showed that SP15-EIA is very specific and sensitive for detecting protecting antibodies (specificity, 100%; sensitivity, 98.20%). This study demonstrates that antibodies against the neutralizing domain represented by SP15 would be important in the memory response after natural infection and may be a good tool in the determination of the true immune status of patients with remote infection with regard to RV. Rubella virus (RV) is the etiologic agent of German measlesand is the sole member of the genus Rubivirus in the Togaviridae family. During the first trimester of pregnancy, the infection may induce congenital malformations and viral persistence in the human fetus (26).The RV virion contains an RNA genome enclosed in an icosahedral capsid composed of protein C (33 kDa). Surrounding this nucleocapsid is a lipid bilayer, in which viral glycoproteins E1 (58 kDa) and E2 (42 to 47 kDa) are embedded (18). The humoral immune response to RV is predominantly to the E1 glycoprotein and persists indefinitely after infection (13,17).The E1 glycoprotein has been suggested to be the immunodominant antigen, since most virus-neutralizing antibodies are directed against this subunit. Monoclonal antibodies (MAbs) were used to define the neutralizing domains on the E1 glycoprotein whose amino acid sequences were determined by overlapping synthetic peptides (9,11,12,14,21,22,24). One of these domains was defined by three independent MAbs that recognized the same sequence, represented by the synthetic peptide SP15 (E1 amino acids 208 to 239) (4, 25). Moreover, SP15 was shown to induce polyvalent antibodies with neutralizing and hemagglutination inhibition activity in mice and rabbits. The sequence of SP15 is present in several strains of RV, such as Therien, Judith, M33, HPV77, RA27/3, Gilchrist, wildtype Cordoba, and Kara 95 (5, 25).Other authors using a similar synthetic peptide, BCH-178C (E1 amino acids 213 to 239), showed the existence of human antibodies that recognize this domain (15,16,27). These authors indicate that BCH-178C can favorably replace curr...

Rubella

“…13, 14 The measurement of antibodies against the neutralizing domain of E1 can be used as a correlate of protection against rubella virus. 15–19 The E2 protein is membrane bound and forms connections between rows of E1 proteins.…”

Characterization of rubella-specific humoral immunity following two doses of MMR vaccine using proteome microarray technology

“…In contrast to the immunodominant E1 glycoprotein, antibodies to E2 have limited neutralizing activity and E2 lacks the ability to elicit antibodies that inhibit hemagglutination. [ 7 , 8 , 9 , 10 , 11 , 12 ] While antibodies to E1 are functional in virus neutralization by hampering virus attachment/cell entry and E1 conformational changes/trimerization during cell entry, the neutralization mechanism of anti-E2 antibodies remains largely unknown. [ 48 ] Glycoprotein E2 function warrants additional studies, but this protein is likely involved in conformational changes during virus entry and maturation, E1 activation, E1 trafficking, and virus membrane budding.…”

“…[ 6 ] The E1 protein, in particular, is considered to be the immunodominant and hemagglutation-eliciting antigen that predominantly contributes to protective immunity. [ 7 , 8 , 9 , 10 , 11 , 12 ] Assays such as whole- rubella virus, recombinant protein and synthetic peptide-based enzyme immunoassays (including immunoblot), hemagglutination inhibition assays, and neutralization assays (including a high-throughput immunocolorimetric-based neutralization assay) have been used in large studies for surveillance of rubella vaccine-induced immunity. [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] Recent papers and expert reviews from the literature point to the lack of standardization of the international rubella antibody standard and the currently used commercial anti-rubella IgG antibody (Ab) assays (leading to misinterpretation of results), and recommend improved and/or alternative approaches in rubella serology testing (including qualitative testing and/or testing without the use of the existing RUBI-1-94 international rubella Ab standard for calibration of assays).…”

T Lymphocytes as Measurable Targets of Protection and Vaccination Against Viral Disorders

“…The E1 and E2 rubella protein spikes are anchored to the external layer of the membrane, with membrane-bound E2 proteins bridging rows of E1 proteins, considered as the main immunodominant antigens responsible for controlling receptor-mediated endocytosis (Petruzziello et al, 1996;Katow and Sugiura, 1985). Antibody levels against the neutralizing domain of E1 correlate with protection against rubella virus (Mitchell et al, 1996;Cordoba et al, 2000;Wilson et al, 2006). Rubella virus is spread from person-to-person via the respiratory route and is the causative agent of rubella disease, commonly known as German measles (Lambert et al, 2015).…”