Borrelia antigens

The antigens of Borrelia burgdorferi can be separated according to their molecular weight by means of SDS-Page (laboratory method for the separation of proteins) and determined by a size marker. About 853 genes (!) are responsible for the immunogenicity of the Borrelia burgdorferi and for the complex immune response of the host.

Immunity and pathogenicity of Borrelia burgdorferi: Borrelia burgdorferi has the ability of adhesion, invasion, persistence and immune evasion. These abilities serve to establish, multiply and spread the pathogen in the infected organism. During the infection Borrelia burgdorferi migrate into different tissues of the host organism to reach so-called "immune privileged niches" where they are protected from the attack of the immune system. These "hiding places" include joints, eyes and the CNS. These locations contain extracellular fluids (synovial and cerebrospinal) that do not circulate in the lymphatic lymphatic flow. Furthermore, Borrelia bacteria prefer to adhere to different lymphatic fluids. Furthermore, Borrelia preferentially adhere to various cells, such as thrombocytes, lymphocytes, fibroblasts, epithelia and endothelia. The BmpA protein (Borrelia membran protein A) seems to play an important role in the adherence of Borrelia bacteria (Verma et al., 2009). Another mechanism of immune evasion is the ability of B. burgdorferi to bind host-specific complement regulators (Reconectin/FHL-1 and Factor H) to the cell surface.

Immune response: IgM antibodies are detectable in humans approximately 2-4 weeks after the initial infection. They reach their maximum about 6-8 weeks after infection. After that they gradually drop again. IgG class antibodies (IgG) appear after 6-8 weeks. IgM antibodies are often detectable over a longer period of time, which makes it difficult to draw conclusions about the approximate time of infection. The IgG concentration, on the other hand, can slowly increase over months/years as the disease progresses until a plateau value is reached and then remain relatively constant.

Note: A distinction between a clinically manifest and a survived Borrelia infection is not possible due to a positive IgG detection. However, the detection of IgM-AK alone largely reliably excludes chronic Lyme disease (Fingerle 2008).

Nomenclature of antigens: The name of antigens is composed of the letter "p" (for protein) and their corresponding molecular weight in kDa (e.g. p39). Some antigens still have proper names due to their function or localisation, e.g. BmpA = Borrelia membrane protein A; OsP = "outer surface proteins". Osp are surface antigens of B. burgdorferi which form a fraction of heterogeneous lipoproteins which are divided into the groups OspA to OspG according to their molecular weight; see below).

Serological screening: The patterns of anti-Borrelia antibodies, in infected people, show a high degree of variability, which makes their assessment difficult. Because of this complex immune response, it is necessary to use an antigen mixture as screening. This panel should contain proteins such as Osp C, BmpA (Borrelia membrane antigen = p39 antigen), p41 antigen and p100 antigen. A number of immunodominant Borrelia proteins could be assigned to the clinical stages of the disease.

Cross reactivities/specificities: A number of conserved Borrelia proteins, such as heat shock proteins and parts of flagellin have epitopes that are also found on other bacteria. This cross-reactivity naturally leads to false positive results. Especially within the human pathogenic genospecies (B. burgdorferi s. s., B. afzelii, B. garinii and B. valaisiana) a pronounced heterogeneity was found for OspA and OspC. For OspA 7 different serotypes were defined. OspA serotype 1 corresponds to the species B. burgdorferi s.s., OspA serotype 2 to the species B. afzelii, OspA serotypes 3-7 to the species B. garinii. Another serotype (serotype 8) has been defined for B. garinii. These differences are of great importance for diagnostics, as the different OspA serotypes are associated with different clinical manifestations in humans. Lyme arthritis, for example, occurs mainly in infections with B. burgdorferi s. s. Like B. garinii, B. burgdorferi is a trigger of neuroborreliosis. Skin manifestations such as acrodermatitis atrophicans, on the other hand, are mainly attributed to infections with B. afzelii.

Important antigens:

• OspC: 22 serotypes have been identified for OsPC (outer surface protein). While OspA (this lipoprotein serves the adhesion of the Borrelia). OSPA is expressed in the gut of fasting ticks, the lipoprotein OspC is formed during the blood meal (Pal et al. 2004). The concentration of OspC increases when the spirochetes leave the tick's midgut and invade the tick's salivary glands.
• OspC apparently plays an important role in the transfer process from the vector to the host (Pal et al. 2004). Like OsPA and OspB, the antigen is considered a very early marker for a Borrelia infection.
• VlsE: VlsE (variable major protein) is another surface lipoprotein important for the infection process, whose synthesis is also regulated by the sucking act and whose activation takes place during the transfer to the host is the plasmid encoded VlsE. It can occur in the early phase as well as in the late phase of the infection. Due to the combinatorial antigen variation as an "immune escape" mechanism, VlsE seems to contribute significantly to the persistence of B. burgdorferi s.l. in the infected mammalian organism.
• BmpA (Borrelia membrane protein = p39): Besides the proteins, OspA, OspC and p83/p100, the 39 kD antigen (BmpA) is also diagnostically relevant (Simpson WJ et al. 1990). This membrane-associated and immunodominant protein may be of great importance in the development of Lyme arthritis (Pal et al. 2008).
• FlaB Flagellin (P41): The flagella-associated p41 antigen induces a very early immune response, which occurs no later than five weeks after infection. P41 plays an important role in the diagnosis of early infection.
• Osp17 (syn. lipoprotein p17, decorin binding protein A, DbpA, p18): Osp17 is another immunodominant Borrelia antigen. The antigen, a lipoprotein, is located on the surface of the outer membrane of the Borrelia and is therefore also called Osp17. Osp17 usually appears at a late stage and is a marker for a chronic course of infection (Jauris-Heipke et al. 1999).
• P58: P58 is another "outer surface protein" which is a late marker of infection. The protein occurs in the three human pathogenic genospecies B. burgdorferi s.s., B. afzelii and B. garinii (Hauser et al. 1997).
• In contrast, p83/p100: p83/p100 has structural properties similar to those of eukaryotic cells, so that an imitation effect is produced which also contributes to immune evasion (Rössler et al., 1995). It is a late-onset marker of infection.

Borrelia burgdorferi antigens (molecular weight in kDa in brackets) and their diagnostic relevance in the course of Lyme disease (varies according to Müllegger B 2018).

Early stage of infection:

• FlaB Flagellin (P41)
• OspE (19.3) early/late
• OspC (22-24) very early
• VlsE p66 (66): fusion protein representing the immunodominant VlsE epitopes of different genospecies early/late
• p39 (39 ) BmpA
• p41 (41) Flagellin

Late stage of infection

• Osp 17 (marker for chronic course of infection)
• p30 (30)
• OspA (31-33) Surface protein B. afzelii
• OspB (34-36)
• p43 (43 )
• p45 (45)
• p58 (58)
• p83/100

The test result of the immunoblot reported by the laboratory should include an indication of the bands detected. For the evaluation of the borrelia serology, the level of AK in the EIA, the number of specific bands, the type of bands (early/late bands) and existing previous findings should be taken into account. The assessment should be carried out with knowledge of the clinical symptoms, the duration of the disease and therapies already carried out.

Diagnosis of neuroborreliosis: In acute neuroborreliosis, in contrast to most other infectious diseases, antibodies can initially only be detected in the CSF. For this reason, even if negative results are suspected in serum, the CSF must always be tested as well. The determination of antibodies in the CSF is only meaningful if a serum from the same day of collection is tested at the same time. Absolute antibody concentrations in the CSF are usually meaningless, since (especially if the CSF barrier function is disturbed) considerable quantities of antibodies can pass from the serum into the CSF. Autochthonously formed antibodies can be detectable for years even after neuroborreliosis has healed. In the case of neuroborreliosis, further pathological findings are usually found in the cerebrospinal fluid: monocytic cerebrospinal fluid pleocytosis; disturbance of the blood-cerebrospinal fluid barrier function (increase of the albumin quotient).

1. Pal U et aal. (2004) OspC facilitates Borrelia burgdorferi invasion of Ixodes scapularis salivary glands. J Clin Invest 113: 220-230.
2. Pal U et al (2008) Borrelia burgdorferi basic membrane proteins A and B participate in the genesis of Lyme arthritis. SOMEONE 205:133-141.
3. Simpson WJ et al (1990) Reactivity of human Lyme borreliosis sera with a 39-kilodalton antigen specific to Borrelia burgdorferi. J Clin microbiol 28: 1329-1337.
4. Liang FT et al (1999) An Immunodominant Conserved Region within the Variable Domain of VlsE, the Variable Surface Antigen of Borrelia burgdorferi. J Immunol 163_ 5566-5573.
5. Müllegger B (2018) infections,: Lyme borreliosis, leptospirosis and relapsing fever. In: Braun-Falco`s Dermatology, Venerology Allergology G. Plewig et al (Hrsg) Springer Verlag S 223
6. Rössler D et al (1995) Molecular and immunological characterization of the p83/100 protein of various Borrelia burgdorferi sensu lato strains. Med Microbiol Immunol 184: 23-32.
7. Verma A et al (2009) Borrelia burgdorferi BmpA is a lamininbinding protein. Infect. Immune. 77: 4940-4946.