Bb spirochete resistance to complement-mediated killing

[Guest guest]

OK, yes, I'm posting quite a bit. Brain now and then feels as if

waking up from extended coma. Sorry if it annoys someone, but it is

a sign of progress in my own treatment, as well as nostalgia for the

days when looking together at research findings helped the members

of this list to stay on a level, no one assuming any more authority

than anyone else.

I associate that with an ancient and honorable democratic instinct

built into the scientific endeavor. It also makes for a cordial

atmosphere and keeps us all from getting too big for our britches

(figuratively speaking - unfortunately, my waistline is unaffected -

if I ever get back to my normal girth, I'll build a denim gazebo out

of these size 38 levis).

Anyhoo...

Has this full text article by son et al from 2002 been

discussed here?

I am excerpting the 'discussion' section because it seems clear and

quite interesting.

I was especially struck by this passage:

" a larva is not infected upon hatching but must acquire B.

burgdorferi through feeding on an infected host. Such a tick feeds

only two more times in its life, once after each molt, during which

B. burgdorferi can be transmitted to a new host. Therefore, to be

biologically successful, a B. burgdorferi bacterium must be

transmitted from a nymph or adult tick, successfully infect the host

upon which that tick feeds, and persist in that host until a larval

tick feeds on the host.

" Since Ixodes sp. ticks may feed on a variety of vertebrate hosts, a

B. burgdorferi bacterium cannot be guaranteed of its next host's

species. Thus, the hypothesized need for multiple different Erp

proteins must be present on a single bacterium, providing the

bacterium with an ability to bind complement-inhibiting factors of a

wide variety of potential hosts and ensuring survival of the

bacterium and its progeny. "

This is what I would call THINKING, as it applies to the specific

features and challenges presented by this pathogen.

http://www.pubmedcentral.gov/articlerender.fcgi?

tool=pubmed & pubmedid=11796574

Ever since their discovery, why B. burgdorferi contain multiple

different erp genes has been puzzling. However, the observation that

all Lyme disease borreliae carry numerous erp genes led to the

hypothesis that Erp proteins are likely to perform essential

functions in these bacteria (14, 73). The data presented in this

report, together with the data of Hellwage et al. (29), suggest that

these proteins provide resistance to complement-mediated killing

through their interactions with host factor H. Erp proteins are

exposed on the bacterial outer surface (22, 45) and so are

positioned to bind factor H. Expression of all erp genes carried by

an individual bacterium appears to be regulated through a single

pathway, as all of the proteins are expressed in response to the

same environmental stimuli (6, 28, 68, 71) and can be simultaneously

coexpressed by individual bacteria (28; El-Hage and son,

unpublished results). The entire repertoire of Erp proteins encoded

by the genes of a bacterium is synthesized during the initial stages

of mammalian infection, a stage in the B. burgdorferi infection

cycle when the bacteria encounter host serum and complement (28,

68). The bacteria also encounter complement while they are in the

tick vector, both when the tick acquires an infection and when the

bacteria are being transmitted to a new host. Consistent with this,

analysis of B. burgdorferi gene expression during various stages of

tick infection has demonstrated that erp genes are transcribed at

all times at which the bacteria are exposed to host blood (27).

While many pathogenic organisms make themselves insensitive to

complement-mediated killing by coating their surfaces with host

factor H (34), the amino acid sequences and glycosylation patterns

of factor H differ from animal to animal (2, 30, 42). Because of the

variations, the host range of a pathogen can be severely restricted

by which factor H proteins its receptors are able to bind. Our study

indicated that Erp proteins bind factor H but they do so with

different specificities for the complement inhibitor factors of

various animals. An examination of the natural history of B.

burgdorferi indicates why such an ability is important to this

bacterium (Fig. 4) (35, 67). There are three postembryonic stages in

the development of the vector Ixodes sp. ticks: larva, nymph, and

adult. There is negligible transovarial transmission of B.

burgdorferi (50, 63), so a larva is not infected upon hatching but

must acquire B. burgdorferi through feeding on an infected host.

Such a tick feeds only two more times in its life, once after each

molt, during which B. burgdorferi can be transmitted to a new host.

Therefore, to be biologically successful, a B. burgdorferi bacterium

must be transmitted from a nymph or adult tick, successfully infect

the host upon which that tick feeds, and persist in that host until

a larval tick feeds on the host. Since Ixodes sp. ticks may feed on

a variety of vertebrate hosts, a B. burgdorferi bacterium cannot be

guaranteed of its next host's species. Thus, the hypothesized need

for multiple different Erp proteins must be present on a single

bacterium, providing the bacterium with an ability to bind

complement-inhibiting factors of a wide variety of potential hosts

and ensuring survival of the bacterium and its progeny.

Although virulent isolates of B. burgdorferi are generally resistant

to complement-mediated killing (3, 10, 36, 41, 61, 76), they may be

susceptible to the alternative pathways of some vertebrates (10, 43,

44). This observation led to the hypothesis that the host range of a

particular B. burgdorferi bacterium is restricted by its ability to

defeat the alternative pathway of complement-mediated killing in

susceptible hosts (43, 44, 46). Our data refine this hypothesis to

include the ability of a bacterium's Erp proteins to bind factor H

as an important element in determining whether the bacterium can

infect a particular host. There is often considerable variation in

the Erp protein sequences of different B. burgdorferi isolates, and

we predict that the differences can have significant effects on the

host ranges of the isolates. Additional analyses of B. burgdorferi

host ranges, sensitivity to complement, and Erp protein

characteristics should continue to test and refine the hypotheses

described above.

The location of erp genes on extrachromosomal elements, rather than

on the bacterial chromosome, is consistent with the theory that

genes which confer specific local advantages are often plasmid-

borne, since they are more readily transferred between bacteria

(19). Furthermore, there is strong evidence that the members of the

cp32 family of plasmids which carry the erp genes are prophages (20,

21), which could allow very efficient shuffling of desirable erp

genes among a population via bacteriophage transduction (54).

Indeed, it is evident that exchange of erp genes does occur in

nature (1, 69, 74). However, different B. burgdorferi strains

isolated in the same geographic region may contain similar erp gene

sequences (52, 73; unpublished results), suggesting that there is

genetic stability in bacteria that share a host reservoir pool.

Recent studies found that human factor H bound to at least two

different proteins in whole-cell lysates of B. burgdorferi (3, 40).

Our data strongly suggest that these unidentified proteins are

members of the Erp protein family. However, the previous studies

were performed with bacteria other than strain B31, and since the

erp gene sequences of different bacterial strains are often

considerably different, it is unlikely that any of these factor H-

binding proteins are identical to any of the factor H-binding

proteins encoded by strain B31.

We noted that the recombinant ErpK protein examined in this study

did not detectably bind a factor H protein and that some other Erp

proteins exhibited relatively weak factor H binding. This may have

been a consequence of the SDS-PAGE-based immunoaffinity analysis

technique used; perhaps the recombinant proteins were not folded so

that they were able to bind factor H, while the native proteins may

have been able to bind factor H. There is also the strong

possibility that ErpK and some of the other Erp proteins

preferentially bind the factor H proteins of animals not examined in

this study. B. burgdorferi is capable of infecting a wide variety of

animals (11, 32, 47, 58), and ErpK may play a role in inactivating

the alternative pathways of some of these hosts.

It has been noted that while some strains of B. burgdorferi are

resistant to complement-mediated killing, mutants of the same

strains may be sensitive to killing (39, 61). Since B. burgdorferi

regulates synthesis of Erp proteins (73), it is possible that such

mutants lack the ability to produce Erp proteins under the

conditions tested. Indeed, many such mutants are defective in gene

regulation and exhibit protein profiles different from those of

their parent strains (39, 61). Additionally, B. burgdorferi is known

to lose plasmids during cultivation, including the plasmids that

encode Erp proteins (14), so it is also possible that the mutants

lost plasmids encoding the Erp proteins that bind factor H for the

type of serum being tested. Further analysis of such mutants should

provide additional insight into the mechanisms by which B.

burgdorferi resists killing via the alternative pathway.

Based on comparisons of the amino acid sequences, it was recently

proposed that B. burgdorferi Erp proteins can be subdivided into

three groups (1). Furthermore, it was also suggested that the groups

should be given the following different names, suggesting that the

groups have different functions: OspE for the proteins most like the

strain N40 OspE protein; OspF for the proteins most like the strain

N40 OspF protein; and Elp for the proteins less similar to either

strain N40 protein (1). The results of our study indicate that

members of all three groups can bind factor H. ErpA/I/N, ErpC, and

ErpP are in the OspE group; ErpG, ErpL, and ErpY are in the OspF

group; and ErpX is in the Elp group (1). Our data suggest that most,

if not all, Erp proteins perform similar functions for the bacteria

and that sequence variations are probably necessary consequences of

the affinities of the proteins for different factor H proteins.

Thus, we conclude that a name change is not necessary for the Erp

proteins.

In addition to members of the erp multigene family, individual B.

burgdorferi strains may contain members of several other families of

paralogous genes; strain B31 contains members of at least 161 such

families (13, 25). For example, it is known that B. burgdorferi

expresses Mlp proteins during mammalian infection (62, 77), yet

strain B31 contains genes for at least nine different paralogs of

these proteins (13, 62). We wonder whether each Mlp paralog might

permit advantageous interactions with a different potential host.

In conclusion, our studies demonstrated that B. burgdorferi Erp

proteins bind the factor H proteins of several diverse mammalian

species. Additionally, the relative affinities of each Erp protein

for factor H proteins differed depending on the animal serum tested,

with ErpA/I/N having the greatest relative affinity for rat factor H

but ErpX having the greatest relative affinity for the cat homolog.

These data suggest that Erp proteins contribute to the expansive

host range of B. burgdorferi by making the bacteria insensitive to

the alternative pathways of many different types of animals.

Additional studies of the bacteriophage-encoded Erp proteins will

undoubtedly reveal important information concerning these apparent

virulence factors and their role in the pathogenesis of Lyme disease.

[Guest guest]

I suppose I'd better try to understand what they're saying but my

mind glazes over today.

So how do you summarize what they're saying?

One of the studies posted a while back was interesting because

essentially it looks like only some strains of bb are pathogenic. I

think it had to do with the OspC's.

I can't think more today. My brain is gluggy.

> OK, yes, I'm posting quite a bit. Brain now and then feels as if

> waking up from extended coma. Sorry if it annoys someone, but it is

> a sign of progress in my own treatment, as well as nostalgia for

the

> days when looking together at research findings helped the members

> of this list to stay on a level, no one assuming any more authority

> than anyone else.

>

> I associate that with an ancient and honorable democratic instinct

> built into the scientific endeavor. It also makes for a cordial

> atmosphere and keeps us all from getting too big for our britches

> (figuratively speaking - unfortunately, my waistline is unaffected -

> if I ever get back to my normal girth, I'll build a denim gazebo

out

> of these size 38 levis).

>

> Anyhoo...

>

> Has this full text article by son et al from 2002 been

> discussed here?

>

> I am excerpting the 'discussion' section because it seems clear and

> quite interesting.

>

> I was especially struck by this passage:

>

> " a larva is not infected upon hatching but must acquire B.

> burgdorferi through feeding on an infected host. Such a tick feeds

> only two more times in its life, once after each molt, during which

> B. burgdorferi can be transmitted to a new host. Therefore, to be

> biologically successful, a B. burgdorferi bacterium must be

> transmitted from a nymph or adult tick, successfully infect the

host

> upon which that tick feeds, and persist in that host until a larval

> tick feeds on the host.

>

> " Since Ixodes sp. ticks may feed on a variety of vertebrate hosts,

a

> B. burgdorferi bacterium cannot be guaranteed of its next host's

> species. Thus, the hypothesized need for multiple different Erp

> proteins must be present on a single bacterium, providing the

> bacterium with an ability to bind complement-inhibiting factors of

a

> wide variety of potential hosts and ensuring survival of the

> bacterium and its progeny. "

>

> This is what I would call THINKING, as it applies to the specific

> features and challenges presented by this pathogen.

>

>

>

>

>

> http://www.pubmedcentral.gov/articlerender.fcgi?

> tool=pubmed & pubmedid=11796574

>

> Ever since their discovery, why B. burgdorferi contain multiple

> different erp genes has been puzzling. However, the observation

that

> all Lyme disease borreliae carry numerous erp genes led to the

> hypothesis that Erp proteins are likely to perform essential

> functions in these bacteria (14, 73). The data presented in this

> report, together with the data of Hellwage et al. (29), suggest

that

> these proteins provide resistance to complement-mediated killing

> through their interactions with host factor H. Erp proteins are

> exposed on the bacterial outer surface (22, 45) and so are

> positioned to bind factor H. Expression of all erp genes carried by

> an individual bacterium appears to be regulated through a single

> pathway, as all of the proteins are expressed in response to the

> same environmental stimuli (6, 28, 68, 71) and can be

simultaneously

> coexpressed by individual bacteria (28; El-Hage and son,

> unpublished results). The entire repertoire of Erp proteins encoded

> by the genes of a bacterium is synthesized during the initial

stages

> of mammalian infection, a stage in the B. burgdorferi infection

> cycle when the bacteria encounter host serum and complement (28,

> 68). The bacteria also encounter complement while they are in the

> tick vector, both when the tick acquires an infection and when the

> bacteria are being transmitted to a new host. Consistent with this,

> analysis of B. burgdorferi gene expression during various stages of

> tick infection has demonstrated that erp genes are transcribed at

> all times at which the bacteria are exposed to host blood (27).

>

> While many pathogenic organisms make themselves insensitive to

> complement-mediated killing by coating their surfaces with host

> factor H (34), the amino acid sequences and glycosylation patterns

> of factor H differ from animal to animal (2, 30, 42). Because of

the

> variations, the host range of a pathogen can be severely restricted

> by which factor H proteins its receptors are able to bind. Our

study

> indicated that Erp proteins bind factor H but they do so with

> different specificities for the complement inhibitor factors of

> various animals. An examination of the natural history of B.

> burgdorferi indicates why such an ability is important to this

> bacterium (Fig. 4) (35, 67). There are three postembryonic stages

in

> the development of the vector Ixodes sp. ticks: larva, nymph, and

> adult. There is negligible transovarial transmission of B.

> burgdorferi (50, 63), so a larva is not infected upon hatching but

> must acquire B. burgdorferi through feeding on an infected host.

> Such a tick feeds only two more times in its life, once after each

> molt, during which B. burgdorferi can be transmitted to a new host.

> Therefore, to be biologically successful, a B. burgdorferi

bacterium

> must be transmitted from a nymph or adult tick, successfully infect

> the host upon which that tick feeds, and persist in that host until

> a larval tick feeds on the host. Since Ixodes sp. ticks may feed on

> a variety of vertebrate hosts, a B. burgdorferi bacterium cannot be

> guaranteed of its next host's species. Thus, the hypothesized need

> for multiple different Erp proteins must be present on a single

> bacterium, providing the bacterium with an ability to bind

> complement-inhibiting factors of a wide variety of potential hosts

> and ensuring survival of the bacterium and its progeny.

>

> Although virulent isolates of B. burgdorferi are generally

resistant

> to complement-mediated killing (3, 10, 36, 41, 61, 76), they may be

> susceptible to the alternative pathways of some vertebrates (10,

43,

> 44). This observation led to the hypothesis that the host range of

a

> particular B. burgdorferi bacterium is restricted by its ability to

> defeat the alternative pathway of complement-mediated killing in

> susceptible hosts (43, 44, 46). Our data refine this hypothesis to

> include the ability of a bacterium's Erp proteins to bind factor H

> as an important element in determining whether the bacterium can

> infect a particular host. There is often considerable variation in

> the Erp protein sequences of different B. burgdorferi isolates, and

> we predict that the differences can have significant effects on the

> host ranges of the isolates. Additional analyses of B. burgdorferi

> host ranges, sensitivity to complement, and Erp protein

> characteristics should continue to test and refine the hypotheses

> described above.

>

> The location of erp genes on extrachromosomal elements, rather than

> on the bacterial chromosome, is consistent with the theory that

> genes which confer specific local advantages are often plasmid-

> borne, since they are more readily transferred between bacteria

> (19). Furthermore, there is strong evidence that the members of the

> cp32 family of plasmids which carry the erp genes are prophages

(20,

> 21), which could allow very efficient shuffling of desirable erp

> genes among a population via bacteriophage transduction (54).

> Indeed, it is evident that exchange of erp genes does occur in

> nature (1, 69, 74). However, different B. burgdorferi strains

> isolated in the same geographic region may contain similar erp gene

> sequences (52, 73; unpublished results), suggesting that there is

> genetic stability in bacteria that share a host reservoir pool.

>

> Recent studies found that human factor H bound to at least two

> different proteins in whole-cell lysates of B. burgdorferi (3, 40).

> Our data strongly suggest that these unidentified proteins are

> members of the Erp protein family. However, the previous studies

> were performed with bacteria other than strain B31, and since the

> erp gene sequences of different bacterial strains are often

> considerably different, it is unlikely that any of these factor H-

> binding proteins are identical to any of the factor H-binding

> proteins encoded by strain B31.

>

> We noted that the recombinant ErpK protein examined in this study

> did not detectably bind a factor H protein and that some other Erp

> proteins exhibited relatively weak factor H binding. This may have

> been a consequence of the SDS-PAGE-based immunoaffinity analysis

> technique used; perhaps the recombinant proteins were not folded so

> that they were able to bind factor H, while the native proteins may

> have been able to bind factor H. There is also the strong

> possibility that ErpK and some of the other Erp proteins

> preferentially bind the factor H proteins of animals not examined

in

> this study. B. burgdorferi is capable of infecting a wide variety

of

> animals (11, 32, 47, 58), and ErpK may play a role in inactivating

> the alternative pathways of some of these hosts.

>

> It has been noted that while some strains of B. burgdorferi are

> resistant to complement-mediated killing, mutants of the same

> strains may be sensitive to killing (39, 61). Since B. burgdorferi

> regulates synthesis of Erp proteins (73), it is possible that such

> mutants lack the ability to produce Erp proteins under the

> conditions tested. Indeed, many such mutants are defective in gene

> regulation and exhibit protein profiles different from those of

> their parent strains (39, 61). Additionally, B. burgdorferi is

known

> to lose plasmids during cultivation, including the plasmids that

> encode Erp proteins (14), so it is also possible that the mutants

> lost plasmids encoding the Erp proteins that bind factor H for the

> type of serum being tested. Further analysis of such mutants should

> provide additional insight into the mechanisms by which B.

> burgdorferi resists killing via the alternative pathway.

>

> Based on comparisons of the amino acid sequences, it was recently

> proposed that B. burgdorferi Erp proteins can be subdivided into

> three groups (1). Furthermore, it was also suggested that the

groups

> should be given the following different names, suggesting that the

> groups have different functions: OspE for the proteins most like

the

> strain N40 OspE protein; OspF for the proteins most like the strain

> N40 OspF protein; and Elp for the proteins less similar to either

> strain N40 protein (1). The results of our study indicate that

> members of all three groups can bind factor H. ErpA/I/N, ErpC, and

> ErpP are in the OspE group; ErpG, ErpL, and ErpY are in the OspF

> group; and ErpX is in the Elp group (1). Our data suggest that

most,

> if not all, Erp proteins perform similar functions for the bacteria

> and that sequence variations are probably necessary consequences of

> the affinities of the proteins for different factor H proteins.

> Thus, we conclude that a name change is not necessary for the Erp

> proteins.

>

> In addition to members of the erp multigene family, individual B.

> burgdorferi strains may contain members of several other families

of

> paralogous genes; strain B31 contains members of at least 161 such

> families (13, 25). For example, it is known that B. burgdorferi

> expresses Mlp proteins during mammalian infection (62, 77), yet

> strain B31 contains genes for at least nine different paralogs of

> these proteins (13, 62). We wonder whether each Mlp paralog might

> permit advantageous interactions with a different potential host.

>

> In conclusion, our studies demonstrated that B. burgdorferi Erp

> proteins bind the factor H proteins of several diverse mammalian

> species. Additionally, the relative affinities of each Erp protein

> for factor H proteins differed depending on the animal serum

tested,

> with ErpA/I/N having the greatest relative affinity for rat factor

H

> but ErpX having the greatest relative affinity for the cat homolog.

> These data suggest that Erp proteins contribute to the expansive

> host range of B. burgdorferi by making the bacteria insensitive to

> the alternative pathways of many different types of animals.

> Additional studies of the bacteriophage-encoded Erp proteins will

> undoubtedly reveal important information concerning these apparent

> virulence factors and their role in the pathogenesis of Lyme

disease.