 |
|
Acinetobacter Immune Responses in Multiple Sclerosis
Etiopathogenetic Role and Its Possible Use as a Diagnostic Marker
Alan Ebringer, MD;
Lucy Hughes, PhD;
Taha Rashid, MBChB;
Clyde Wilson, PhD
Arch Neurol. 2005;62:33-36.
ABSTRACT
Multiple sclerosis (MS) is the most common cause of neurologic disability among young people. The etiology of MS is controversial, but immune responses are considered to somehow be involved. The diagnosis of MS depends on a combination of various clinical and laboratory features, but apart from some myelin-neuronal autoantibody profiles or oligoclonal bands in the cerebrospinal fluid no other serologic diagnostic test or marker has yet been discovered. However, the presence of antibodies to Acinetobacter species in MS patients opens the possibility of developing a composite laboratory diagnostic marker, the myelin-Acinetobacter-neurofilament index. Whether Acinetobacter is the triggering agent of MS remains to be determined, but the measurement of anti-Acinetobacter antibodies could be used as a marker of disease activity. To evaluate this, prospective randomized controlled studies should be performed with MS patients, especially in the early stages of the disease.
INTRODUCTION
Multiple sclerosis (MS) is a common demyelinating disease of the central nervous system, usually affecting young people and characterized pathologically by scattered areas of inflammation with or without axonal damage, involving particularly the white matter. Multiple sclerosis has a worldwide distribution, and as many as 1 million people are affected by the disease. The prevalence of MS shows a latitudinal effect in that it is higher in Scandinavian countries than in the tropics.1 The reverse is observed in the Southern hemisphere, where MS is 7 times more common in Tasmania and Southern New Zealand than in tropical Queensland2 in populations coming predominantly from Anglo-Celtic stock. This latitudinal effect could be linked to greater prevalence of respiratory infections during autumn and winter.
ETIOPATHOGENESIS
Evidence of Genetic Factors
In a recent review,3 none of the 3 large screening studies performed in outbred populations of Northern European origin was successful in identifying genetic markers that show statistically significant linkage with the disease. It has been suggested that many different chromosomal regions are likely to be involved in MS.4
Evidence of Environmental Factors
Various studies have supported the role of environmental or microbial factors in the pathogenesis of MS: (1) a relatively low concordance rate for monozygotic twins (approximately 25%), dizygotic twins (approximately 5%), and siblings (approximately 3%) of patients with MS5 ; (2) reports of an outbreak of MS in the Faroe Islands, which occurred after the start of World War II6 ; (3) increase in the probability of developing MS with migration rate from low- to high-risk areas, especially among those in younger age groups7 ; and (4) the occurrence of remissions and exacerbations in MS as a common hallmark of the disease and a possible result of fluctuations in the exposure to certain triggering environmental factors.
Microorganisms Possibly Involved in the Etiopathogenesis of MS
Various microbial agents have been implicated in the etiopathogenesis of MS. The role of viruses8 has been extensively studied, but no clear consensus has emerged from these investigations. Viruses such as Epstein-Barr virus and human herpesvirus 6, which have been implicated in MS, are ubiquitous in the environment, but others have failed to confirm a link between human herpesvirus 6 and MS.9 Some researchers have found a link between the gram-negative Chlamydia pneumoniae bacteria and MS,10 but others have failed to confirm these associations.11 The role of other bacteria, such as Acinetobacter species and Pseudomonas aeruginosa, has only been studied recently but with some encouraging results.
Acinetobacter and MS
Myelin sequences known to produce experimental allergic encephalomyelitis in guinea pigs, an animal model of MS,12 were examined using the GenBank (NCBI, Bethesda, Md) and SwissProt (TrEMBL, Geneva, Switzerland) databases for molecular mimicry between brain tissues and microbes. The ubiquitous saprophytic microbe, Acinetobacter, was found to possess such a sequence.13
Antibody levels against 5 strains of Acinetobacter sp, P aeruginosa, and Escherichia coli were investigated in 26 English patients with MS and compared with 20 patients with cerebrovascular accidents and 25 healthy control. There were significant elevations in the levels of antibodies of IgM, IgG, and IgA classes against all bacterial agents except E coli in patients with MS when compared with those with cerebrovascular accidents and healthy controls.14 The elevations in these antibodies were found to be more prominent against Acinetobacter calcoaceticus, Acinetobacter 11171, and Acinetobacter lwoffii strains, and in some cases their levels were reaching titers of up to 1:6400.
In a more recent study15 performed on serum samples taken from the same group of patients and controls included in the previous study, antibody levels against mimicking peptide from Acinetobacter (P<.001), Pseudomonas (P<.001), myelin basic protein (MBP) (P<.001), and myelin oligodendrocyte glycoprotein (MOG) (P<.001) were found to be elevated in patients with MS when compared with those with cerebrovascular accidents or healthy controls. Antiserum raised in mice against Acinetobacter-mimicking peptides were found to be significantly inhibited by peptides from the MBP or Pseudomonas microbe. Furthermore, MOG peptides were found to inhibit antibodies against the mimicking sequences present in Acinetobacter, but no inhibition was observed when human papillomavirus peptides were used as controls.
In another study,16 serum samples from Austrian patients with MS or other neurologic diseases and healthy controls were screened against 3 strains of Acinetobacter spp. There were significant elevations of total antibodies against A calcoaceticus, A lwoffii, and A 11171 bacterial strains in patients with MS and those with some other neurologic diseases, such as sporadic Creutzfeldt-Jakob disease, but not in patients with Alzheimer disease and dementia, when compared with controls.
UPPER RESPIRATORY TRACT AND PARANASAL SINUSES AS THE SOURCE OF INFECTIONS IN MS
The most likely source for the entry of any triggering microbial factor in MS is through the upper respiratory tract (URT). Several lines of evidence support this possibility. First, sinusitis is present in many MS patients, and the rate of MS exacerbations during the sinusitis attacks was found to be doubled.17 Furthermore, using magnetic resonance imaging of the nasal sinuses, 53% of MS patients had evidence of sinusitis.18 Second, in one study,19 the main causative agents involved in sinusitis were found to be Acinetobacter, Pseudomonas, and Staphylococcus aureus. In a subsequent study involving antral tap and endoscopically directed tissue culture performed on acute sinusitis patients, 37% and 33% of the isolates from the antral tap and the endoscopically directed tissue culture, respectively, were Acinetobacter bacteria.20 Third, in another retrospective study,21 more than 50% of MS patients had a history of repeated respiratory tract infections during their childhood. Fourth, clinically manifest infections predominantly of the URT were observed to be followed by more attacks of exacerbations in patients with MS.22
These results suggest that MS could be triggered and perpetuated following repeated attacks of subclinical or overt infections in the URT or paranasal sinuses. Furthermore, viral infections of the URT and paranasal sinuses, which occur more frequently in autumn and winter, could provide a suitable biological milieu for the secondary growth of a saprophytic microbe such as Acinetobacter.
MOLECULAR MIMICRY AND MS
Molecular mimicry or cross-reactivity has been proposed as the main pathogenetic mechanism for development of autoimmune diseases, such as rheumatic fever, Sydenham chorea, rheumatoid arthritis, and ankylosing spondylitis.23 The molecular mimicry hypothesis is based on the demonstration of autoimmunity, involving molecular and/or immunologic cross-reactivity between the putatively causative microbes and autoantigens, increased antibodies against these microbial and autoantigenic molecules, and the binding of these microbial cross-reactive antibodies to the targeted tissues with resultant immune-mediated cytotoxic tissue damage.24
Evidence of Autoimmunity in MS
Autoantibodies to many myelin-neuronal antigens have been found in patients with MS. For example, the levels of antibodies to MBP,25 MOG,26 and neurofilament14, 27 were found to be elevated in patients with MS when compared with control groups. Some of these antibodies were even found to be predictive of the development of clinically definite MS after a first demyelinating event.28 Furthermore, levels of anti-MBP or anti-MOG antibodies were reported to be elevated in the cerebrospinal fluid and/or isolated from the plaque lesions in the central nervous system of MS patients.29 In studies30 that involved animal models of MS, such as experimental allergic encephalomyelitis, MS-like lesions were detected and characterized by local infiltrations of immune-mediated cells and products, when these animals were inoculated with the myelin-neuronal antigens. Patients with MS have reportedly responded to the currently used immunomodulatory and anti-inflammatory therapeutic agents, especially interferon beta 1 products31 and corticosteroids.
Evidence of Molecular Similarities Between Acinetobacter and Pseudomonas Bacteria and Brain Antigens
Acinetobacter and Pseudomonas enzymes show molecular similarities to certain brain antigens (Figure 1). The enzyme 4-carboxy-muconolactone decarboxylase possesses an amino acid sequence that is similar to MBP,13 and protocatechuate 3,4-dioxygenase has a sequence homologous to neurofilament.32 The 3-oxoadipate coenzyme A transferase enzyme of the same bacteria possesses amino acid sequences that are similar to those present in the MOG brain tissue antigens.15 In this latter study, it was also shown that the enzyme  -carboxy-muconolactone decarboxylase of the Pseudomonas microbes possesses amino acid residues that are homologous to those present in the MBP molecules.
|
|
|
|
Figure 1. Schematic molecular similarities between Acinetobacter and Pseudomonas bacterial enzymes and brain antigens. 4-CMLD indicates 4-carboxy-muconolactone decarboxylase; 3-OACT, 3-oxoadipate coenzyme A transferase; and -CMLD, -carboxy-muconolactone decarboxylase. Amino acids and their locations are also shown: Leu indicates leucine; Tyr, tyrosine; Arg, arginine; Ala, alanine; Gly, glycine; Lys, lysine; Asp, asparagine; Ser, serine; Phe, phenylalanine; Try, tryptophan; Thr, threonine; and His, histidine.
|
|
|
Possible Pathogenetic Pathway in MS Involving Acinetobacter Species
It is proposed that antibodies against Acinetobacter and possibly Pseudomonas microorganisms are produced as the result of URT or paranasal sinus infections by these microbes (Figure 2). In view of the existing molecular similarities between microbes and brain antigens, these cross-reactive antibodies, which are mostly of the IgG isotype, could cross the blood-brain barrier. The binding of these antibodies to the myelin-neuronal antigens, such as MBP, MOG, and neurofilaments, when present in high titers would activate complement and other inflammatory cascades, thereby producing demyelination through the process of antibody-dependent, cell-mediated cytotoxicity in the same way that has been shown in patients with Sydenham (rheumatic) chorea.33 These events could eventually result in multiple sites of demyelinations with or without axonal degenerations.
|
|
|
|
Figure 2. Proposed sequential pathogenetic events in the development of multiple sclerosis. MBP indicates myelin basic protein; MOG, myelin oligodendrocyte glycoprotein.
|
|
|
PROPOSAL FOR A NEW LABORATORY DIAGNOSTIC MARKER IN MS
Apart from the criteria for the diagnosis of MS by Poser et al,34 other diagnostic criteria, which have been recommended by neurologists from the United States and Europe, are all based on a combination of clinical and paraclinical features.35 The main clinical evidence is based on the objective findings of dissemination in time (relapses) and space (different locality) of the clinical presentations typical of MS, whereas the nonclinical criteria are mainly based on the following: (1) magnetic resonance imaging evidence of multiple neurologic lesions of different sizes and locations; (2) identification of IgG oligoclonal bands in the cerebrospinal fluid; and (3) delayed but well-preserved visual evoked potentials.
These paraclinical criteria are helpful in aiding the diagnosis of clinically probable cases of MS, but they require expensive facilities. Furthermore, these diagnostic criteria cannot identify all cases of MS because of the clinical variability of the disease. Hence, the search for the development of a less invasive and reproducible test is of crucial importance.
We propose that a combination of elevated titers of antibodies against Acinetobacter, MBP, and neurofilament could be used for such a diagnostic test. The myelin-Acinetobacter-neurofilament (MAN) index, which has been described previously,14 was calculated using the optical density (OD) readings from the IgG antibody determined by enzyme-linked immunosorbent assay. The formula used was as follows: MAN Index = (MBP OD x 10) (Acinetobacter OD x 10) (Neurofilament OD x 10).
The MAN index is calibrated by determining scores in MS patients and healthy controls. For an active MS patient, the MAN index is expected to be above the 95% confidence intervals of the healthy controls. Further research is needed to elaborate and modify this particular diagnostic marker. For example, instead of using whole bacteria, Acinetobacter peptides, which carry the cross-reactive brain antigens, may give a clearer separation when compared with controls.15
MONITORING TREATMENT IN MS
The current therapeutic strategy in the management of MS involves the use of immunomodulatory and immunosuppressive drugs. These modalities have been found to be effective mainly in cases of relapsing-remitting forms but less so in the progressive forms of MS.36 The evidence of the bacterial (Acinetobacter and Pseudomonas) involvements in the etiopathogenesis of MS suggests the possibility of using antimicrobial therapy, and its use should be evaluated in prospective, longitudinal randomized controlled studies.
In conclusion, the demonstration of the cross-reactivity between Acinetobacter and Pseudomonas bacteria and brain antigens has raised the possibility of developing a disease marker, the MAN index, which could predict the occurrence of relapses in patients with MS and/or monitor response to therapy. However, further studies need to be performed on greater numbers of MS patients to establish the sensitivity and specificity profiles and the degree of the reproducibility of the MAN index.
AUTHOR INFORMATION
Correspondence: Alan Ebringer, MD, Division of Life Sciences, Infection and Immunity Group, King’s College London, 150 Stamford St, London SE1, England (alan.ebringer{at}kcl.ac.uk).
Accepted for Publication: January 28, 2004.
Author Contributions: Acquisition of data: Ebringer, Hughes, Rashid, and Wilson. Analysis and interpretation of data: Ebringer, Hughes, Rashid, and Wilson. Critical revision of the manuscript for important intellectual content: Ebringer, Hughes, Rashid, and Wilson. Statistical analysis: Ebringer, Hughes, Rashid, and Wilson.
Funding/Support: This work was supported by the American Friends of King’s College, London, England.
Author Affiliations: Division of Life Sciences, Infection and Immunity Group, Waterloo Campus, King’s College, London, England.
REFERENCES
1. Kurtzke JF. Multiple sclerosis: changing times. Neuroepidemiology. 1991;10:1-8.
WEB OF SCIENCE
| PUBMED
2. Miller DH, Hammond SR, McLeod JG, Purdie G, Skegg DC. Multiple sclerosis in Australia and New Zealand. J Neurol Neurosurg Psychiatry. 1990;53:903-905.
FREE FULL TEXT
3. Hensiek AE, Sawcer SJ, Compston DA. Searching for needles in haystacks. Brain Res Bull. 2003;61:229-234.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
4. Kenealy SJ, Pericak-Vance MA, Haines JL. The genetic epidemiology of multiple sclerosis. J Neuroimmunol. 2003;143:7-12.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
5. Willer CJ, Dyment DA, Risch NJ, Sadovnick AD, Ebers GC. Twin concordance and sibling recurrence rates in multiple sclerosis. Proc Natl Acad Sci U S A. 2003;100:12877-12882.
FREE FULL TEXT
6. Kurtzke JF, Hyllested K. Multiple sclerosis in the Faroe Islands, III: an alternative assessment of the three epidemics. Acta Neurol Scand. 1987;76:317-339.
WEB OF SCIENCE
| PUBMED
7. Dean G, Elian M. Age at immigration to England of Asian and Caribbean immigrants and the risk of developing multiple sclerosis. J Neurol Neurosurg Psychiatry. 1997;63:565-568.
FREE FULL TEXT
8. Gilden DH. Viruses and multiple sclerosis. JAMA. 2001;286:3127-3129.
FREE FULL TEXT
9. Enbom M, Wang FZ, Fredrikson S, Martin C, Dahl H, Linde A. Similar humoral and cellular immunological reactivities to human herpesvirus 6 in patients with multiple sclerosis and controls. Clin Diagn Lab Immunol. 1999;6:545-549.
FREE FULL TEXT
10. Layh-Schmitt G, Bendl C, Hildt U, et al. Evidence for infection with Chlamydia pneumoniae in a subgroup of patients with multiple sclerosis. Ann Neurol. 2000;47:652-655.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
11. Chatzipanagiotou S, Tsakanikas C, Anagnostouli M, Rentzos M, Ioannidis A, Nicolaou C. Detection of Chlamydia pneumoniae in the cerebrospinal fluid of patients with multiple sclerosis by combination of cell culture and PCR: no evidence for possible association. Mol Diagn. 2003;7:41-43.
FULL TEXT
| PUBMED
12. Eylar EH, Caccam J, Jackson JJ, Westall FC, Robinson AB. Experimental allergic encephalomyelitis. Science. 1970;168:1220-1223.
FREE FULL TEXT
13. Ebringer A, Pirt SJ, Wilson C, Cunningham P, Thorpe C, Ettelaie C. Bovine spongiform encephalopathy. Environ Health Perspect. 1997;105:1172-1174.
WEB OF SCIENCE
| PUBMED
14. Hughes LE, Bonell S, Natt RS, et al. Antibody responses to Acinetobacter spp. and Pseudomonas aeruginosa in multiple sclerosis. Clin Diagn Lab Immunol. 2001;8:1181-1188.
FREE FULL TEXT
15. Hughes L, Smith PA, Bonell S, et al. Cross-reactivity between related sequences found in Acinetobacter spp., Pseudomonas aeruginosa, myelin basic protein and myelin oligodendrocyte glycoprotein in multiple sclerosis. J Neuroimmunol. 2003;144:105-115.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
16. Allerberger F, Berger T, Reindl M, et al. Anti-Acinetobacter and anti-neuronal antibodies in Austrian patients with multiple sclerosis and other neurological diseases. Ann Neurol. In press.
17. Gay D, Dick G, Upton G. Multiple sclerosis associated with sinusitis: case-controlled study in general practice. Lancet. 1986;1:815-819.
WEB OF SCIENCE
| PUBMED
18. Jones RL, Crowe P, Chavda SV, Pahor AL. The incidence of sinusitis in patients with multiple sclerosis. Rhinology. 1997;35:118-119.
PUBMED
19. Bert F, Lambert-Zechovsky N. Sinusitis in mechanically ventilated patients and its role in the pathogenesis of nosocomial pneumonia. Eur J Clin Microbiol Infect Dis. 1996;15:533-544.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
20. Casiano RR, Cohn S, Villasuso E, et al. Comparison of antral tap with endoscopically directed nasal culture. Laryngoscope. 2001;111:1333-1337.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
21. Lamoureux G, Lapierre Y, Ducharme G. Past infectious events and disease evolution in multiple sclerosis. J Neurol. 1983;230:81-90.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
22. Buljevac D, Flach HZ, Hop WCJ, et al. Prospective study on the relationship between infections and multiple sclerosis exacerbations. Brain. 2002;125:952-960.
FREE FULL TEXT
23. Ebringer A, Wilson C. HLA molecules, bacteria and autoimmunity. J Med Microbiol. 2000;49:305-311.
FREE FULL TEXT
24. Wilson C, Rashid T, Tiwana H, et al. Cytotoxicity responses to peptide antigens in rheumatoid arthritis and ankylosing spondylitis. J Rheumatol. 2003;30:972-978.
FREE FULL TEXT
25. Warren KG, Catz I. A correlation between cerebrospinal fluid myelin basic protein and anti-myelin basic protein in multiple sclerosis. Ann Neurol. 1987;21:183-189.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
26. Reindl M, Linington C, Brehm U, et al. Antibodies against the myelin oligodendrocyte glycoprotein and the myelin basic protein in multiple sclerosis and other neurological diseases: a comparative study. Brain. 1999;122:2047-2056.
FREE FULL TEXT
27. Silber E, Semra YK, Gregson NA, Sharief MK. Patients with progressive multiple sclerosis have elevated antibodies to neurofilament subunit. Neurology. 2002;58:1372-1381.
FREE FULL TEXT
28. Berger T, Rubner P, Schautzer F, et al. Antimyelin antibodies as a predictor of clinically definite multiple sclerosis after a first demyelinating event. N Engl J Med. 2003;349:139-145.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
29. Cross AH, Trotter JL, Lyons J. B cells and antibodies in CNS demyelinating disease. J Neuroimmunol. 2001;112:1-14.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
30. Bernard CCA, Mandel T, Mackay IR. Experimental models of human autoimmune disease: overview and prototypes. In: Rose NR, Mackay IR, eds. The Autoimmune Diseases. San Diego, Calif: Academic Press; 1992:47-106.
31. Revel M. Interferon- in the treatment of relapsing-remitting multiple sclerosis. Pharmacol Ther. 2003;100:49-62.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
32. Tiwana H, Wilson C, Pirt J, Cartmell W, Ebringer A. Autoantibodies to brain components and antibodies to Acinetobacter calcoaceticus are present in bovine spongiform encephalopathy. Infect Immun. 1999;67:6591-6595.
FREE FULL TEXT
33. Kirvan CA, Swedo SE, Heuser JS, Cunningham MW. Mimicry and autoantibody-mediated neuronal cell signalling in Sydenham chorea. Nat Med. 2003;9:914-920.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
34. Poser CM, Paty DW, Scheinberg L, et al. New diagnostic criteria for multiple sclerosis: guidelines for research protocols. Ann Neurol. 1983;13:227-231.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
35. McDonald WI, Compston A, Edan G, et al. Recommended diagnostic criteria for multiple sclerosis: guidelines from the International Panel on the diagnosis of multiple sclerosis. Ann Neurol. 2001;50:121-127.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
36. Noseworthy JH. Management of multiple sclerosis: current trials and future options. Curr Opin Neurol. 2003;16:289-297.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
SECTION EDITOR: DAVID E. PLEASURE, MD
 CiteULike  Connotea  Delicious  Digg  Facebook  Reddit  Technorati  Twitter
What's this?
|
