ABSTRACT
Tick-borne encephalitis virus (TBEV) is an emerging human pathogen that causes potentially fatal disease with no specific treatment. Mouse monoclonal antibodies are protective against TBEV, but little is known about the human antibody response to infection. Here, we report on the human neutralizing antibody response to TBEV in a cohort of infected and vaccinated individuals. Expanded clones of memory B cells expressed closely related anti-envelope domain III (EDIII) antibodies in both groups of volunteers. However, the most potent neutralizing antibodies, with IC50s below 1 ng/ml, were found only in individuals who recovered from natural infection. These antibodies also neutralized other tick-borne flaviviruses, including Langat, louping ill, Omsk hemorrhagic fever, Kyasanur forest disease, and Powassan viruses. Structural analysis revealed a conserved epitope near the lateral ridge of EDIII adjoining the EDI-EDIII hinge region. Prophylactic or early therapeutic antibody administration was effective at low doses in mice that were lethally infected with TBEV.
Subject(s)
Antibodies, Monoclonal/immunology , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Encephalitis Viruses, Tick-Borne/immunology , Encephalitis, Tick-Borne/immunology , Immunoglobulin G/immunology , Amino Acid Sequence , Animals , Antibodies, Monoclonal/administration & dosage , Antibodies, Monoclonal/genetics , Antibodies, Neutralizing/administration & dosage , Antibodies, Neutralizing/genetics , Antibodies, Viral/administration & dosage , Antibodies, Viral/genetics , Cells, Cultured , Cohort Studies , Cross Reactions/immunology , Encephalitis Viruses, Tick-Borne/drug effects , Encephalitis Viruses, Tick-Borne/physiology , Encephalitis, Tick-Borne/prevention & control , Encephalitis, Tick-Borne/virology , Epitopes/immunology , Female , Humans , Immunoglobulin G/administration & dosage , Mice, Inbred BALB C , Sequence Homology, Amino Acid , Survival Analysis , Viral Envelope Proteins/genetics , Viral Envelope Proteins/immunologyABSTRACT
Vaccination against tick-borne encephalitis (TBE) is based on the use of formalin-inactivated, culture-derived whole-virus vaccines. Immune response following vaccination is primarily directed to the viral envelope (E) protein, the major viral surface antigen. In Europe, two TBE vaccines are available in adult and pediatric formulations, namely FSME-IMMUN® (Pfizer) and Encepur® (GlaxoSmithKline). Herein, we analyzed the content of these vaccines using mass spectrometry (MS). The MS analysis revealed that the Encepur vaccine contains not only proteins of the whole virus particle, but also viral non-structural protein 1 (NS1). MS analysis of the FSME-IMMUN vaccine failed due to the high content of human serum albumin used as a stabilizer in the vaccine. However, the presence of NS1 in FSME-IMMUN was confirmed by immunization of mice with six doses of this vaccine, which led to a robust anti-NS1 antibody response. NS1-specific Western blot analysis also detected anti-NS1 antibodies in sera of humans who received multiple doses of either of these two vaccines; however, most vaccinees who received ≤3 doses were negative for NS1-specific antibodies. The contribution of NS1-specific antibodies to protection against TBE was demonstrated by immunization of mice with purified NS1 antigen, which led to a significant (p < 0.01) prolongation of the mean survival time after lethal virus challenge. This indicates that stimulation of anti-NS1 immunity by the TBE vaccines may increase their protective effect.
ABSTRACT
UNLABELLED: The Western blot (WB) method was verified for serological diagnosis of chlamydial infections. MATERIAL AND METHODS: For testing, sera previously examined by the microimmunofluorescence (MIF) test with either ambiguous results or those suggesting persistent infection were used. RESULTS: Whereas the investigation confirmed adequate sensitivity and specificity of the MIF test for diagnosing Chlamydophila pneumoniae infection, it was less sensitive in case of Chlamydia trachomatis. Long-term persistence of IgA antibodies, detected by the MIF test, was often not confirmed by WB. CONCLUSIONS: The results support the view that detecting antibodies alone, without appropriate clinical symptoms, is not sufficient for antibiotic treatment of any infection.
