AFRO-NETS> Insensitive syphilis tests: Implications for HIV/AIDS?

[Colman Jones <mail@colman.net>]

Insensitive syphilis tests: Implications for HIV/AIDS?
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Dear colleagues,

In light of recent debates over mass STD treatment as an HIV inter-
vention in Africa, and in view of our ongoing concerns about unde-
tected syphilis as a co-factor for HIV activation and AIDS progres-
sion, we enclose below an abstract of a poster presented at the 2000 
General Meeting of the American Society for Microbiology, held May 
21-25, 2000, in Los Angeles, California.

We have always believed that the role of syphilis as co-factor in 
HIV/AIDS has been hard to measure, because of questions over what 
tests to use and the real rate of treponematoses in the populations 
at risk for AIDS. As shown below, the use of treponemal antigen-based 
screening for syphilis (and in particular a recombinant antigen-based 
system) found almost a 5% syphilis rate in randomly selected speci-
mens from a downtown Toronto STD clinic - specimens, which were all 
negative in the standard screening tests.

Looking at the Rakai and Mwanza populations, it may be that latent 
(i.e. hidden) syphilis is impacting their susceptibility to HIV, and 
yet is going undetected by standard non-treponemal screen tests. If 
higher rates of latent syphilis, detected by a redesigned screening 
system, were found to correlate with a greater rate of new HIV cases, 
then it might suggest both an ulcerative and immunologic role for un-
diagnosed/untreated syphilis in all its stages. Further comments fol-
low after the abstract.

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Treponemal Based Screening for Syphilis-Detecting Latent Cases

N. denHollander, R. Berry, M. Fearon 
Ontario Public Health Laboratory, Toronto, ON Canada 
Presentation Number: C-367

ABSTRACT

Background: With the advent of national plans to eliminate syphilis 
from the United States and Canada it becomes vital that all cases 
(new and old) be identified and where necessary treated. Most labora-
tories in North America use non-treponemal based screening tests for 
syphilis. We asked how many cases of "unknown" syphilis infection 
were being missed using this, the oldest of all syphilis assays.

Methods: We selected 557 "high risk" (from STD Clinics) specimens 
from our routine syphilis submissions, which were non-reactive in our 
standard non-treponemal test [Rapid Plasma Reagin (RPR)] and re-
tested them using a new automatable EIA. The EIA (Trep-Chek (T) - 
Phoenix Bio-Tech Corp) utilizes recombinant antigens from Treponema 
pallidum. All specimens were also tested using a microhemagglutina-
tion assay for T. pallidum (MHA-Tp) and EIA positives were confirmed 
using a T. pallidum specific Western blot (WB). Sensitivity of the 
new assay was checked against 15 patients with proven early primary 
syphilis (direct fluorescence confirmed, dark-field positive smears 
from primary lesions) and a panel of 16 treated, confirmed syphilis 
patients. A panel of 119 "biological false positive" specimens (RPR 
reactive but MHA-Tp non-reactive) was also tested.

Results: The panel of 16 treated, confirmed patients were all posi-
tive by EIA. Of the 15 early primary syphilis cases 14 were positive 
by EIA. Of the 119 BFP specimens 108 were negative by EIA but 10 of 
the remaining 11 were either positive or equivocal in the WB (thus 
not true BFP's). Thus the initial sensitivity and specificity for the 
new EIA was 97% and 99% respectively. In the "high risk" population 
there were 16 positive and 11 indeterminate EIA cases (4.85% of those 
tested). Of these only 9 were MHA-Tp reactive. However fully 24 of 
these 27 EIA positives were either positive or equivocal in the WB 
(our Gold Standard assay). Most importantly 20 of these 24 "con-
firmed" positive syphilis patients were not previously identified in 
our 20 yr database thus potentially new cases.

Conclusions: Standard non-treponemal based assays are clearly under-
sensitive (as apparently are some treponemal assays like the MHA-Tp) 
potentially allowing some syphilis cases to go undetected and un-
treated.

Full poster and comments available at:
http://www.radio.cbc.ca/programs/ideas/Aids/asm2000.html

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A few comments:

This kind of silent syphilis - detectable only by treponemal tests - 
was first discovered and treated by the University of Vienna Medical 
School and Professor Luger from that city, during the 1970s in the 
clinics serving gay men. The tests used in this latest study, cur-
rently awaiting approval by regulatory authorities in Canada and the 
U.S., were designed by Bob Notenboom, our former Ontario chief se-
rologist and now a consultant at Phoenix Bio-Tech Corp in Missis-
sauga, Ontario, Canada.

This work continues the fine tradition of our Ontario Public Health 
Laboratory in providing thorough syphilis screening and ongoing 
evaluation of newer tests. Between 1989 and 1993, the lab, working 
with John Scythes, published (at international STD meetings) three 
reviews of syphilis screening sensitivity in HIV patients, and we are 
excited by this latest effort at trying to increase interest in 
syphilis diagnosis.

One of our biggest concerns is that clinicians are not aware that 
this kind of improved and affordable testing is available, and so 
they are unable to evaluate their syphilis patients further in terms 
of HIV status and viral load, investigating the lymphocyte subsets in 
latent syphilis as well as in HIV, and indeed in the co-infected pa-
tients. 20 of 24 "confirmed" positive syphilis patients were not pre-
viously documented by our Ontario provincial officials as having re-
ceived adequate treatment and follow-up/contact-tracing. Individuals 
who have HIV infection must be regularly tested for syphilis with a 
treponemal antigen-based system, because we have established the se-
lective loss or falling titre of antibody - even IgM antibody - to T. 
pallidum during latent syphilis. This phenomenon, observed by us and 
several other centers back in the late 1980s/early 1990s, apparently 
occurs only in association with HIV infection, despite polyclonal B-
cell activation.

In addition, the immunoblots performed by denHollander and his co-
workers are particularly revealing, and suggest that many of these 
patients have a defective immune response to T. pallidum, rather than 
a response that is waning after adequate treatment. This kind of IgG 
and IgM immunoblotting by SDS Page was first performed in the HIV 
context ten years ago by Daniel Musher and his co-workers in Houston 
(Musher D.M., Hamill RJ, Baughn RE. Annals of Internal Medicine, vol. 
113 (1990), p. 872-881), and these irregularities seem to be a con-
sistent finding - that is, when labs take the time to analyze the im-
mune response to syphilis in high-risk and multiply exposed patients.

The problem for clinicians may well be trying to come up with a re-
vised working definition for latent (i.e. still not adequately 
treated) syphilis. The definitions in the medical literature for la-
tency are somewhat contradictory: one group of authors defines latent 
syphilis that may need (prophylactic) treatment as a positive VDRL 
(and confirmatory tests) in the absence of signs and symptoms, often 
basing their assessment on the VDRL titre alone, whereas another 
school of thought considers a reactive IgG or IgM treponemal test by 
itself, with or without a positive VDRL, as evidence of latent syphi-
lis requiring further testing and possible treatment (depending on 
the patient history). It could be that non-treponemal tests should be 
abandoned altogether for syphilis screening in high risk settings, 
such as Sub-Saharan Africa, and instead only be used to assess the 
stage and treatment response (assuming they're reactive in the first 
place).

This latest ASM 2000 paper also raises the question as to whether we 
should routinely quantify treponemal tests (perhaps titred MHA-Tp), 
as per our earlier work here in Toronto. Syphilis investigators Har-
old J. Magnuson and Thomas B. Turner both found that treponemal tests 
were often anamnestic (i.e., showing an upward change in titre upon 
re-infection) in the experimental systems - in the absence of a VDRL 
screen test change or G&C Type IV skin reaction - but these confirma-
tory tests were never routinely used to identify re-exposed human 
subjects in the real world of infectious big-city syphilis. The last 
major textbook on syphilis (Schell, R.F. & Musher, D.M., eds. Patho-
genesis and Immunology of Treponemal Infection. New York: Marcel Dek-
ker, 1983) raises many of these points about immunity to syphilis and 
response to antigen challenge, whether it be more syphilis or a het-
erologous antigen.

Routine quantified testing - i.e. a titred treponemal test every 3 
months - might also establish whether the previously documented sero-
reversion of treponemal tests is still going on today. How does this 
loss of antibody correlate to the CD4 and CD8 levels? Here in To-
ronto, we found that all of those who had lost treponemal antibody 
were severely immune suppressed (i.e. an average of 78 CD4/mm3), com-
pared to the HIV clinic average CD4 count of 400/mm3. Our window pe-
riod was about 18 months, and the patients kept dying off. So how do 
we assess the real role of latent syphilis in AIDS?

Interestingly, treponemal tests have been found by some authors to 
respond quantitatively after aggressive therapy in patients with 
negative or serofast non-treponemal tests. Such a response could give 
us some sort of marker for treatment efficacy and evaluation, in ad-
dition to the anti-treponemal IgM (SPHA IgM) or immunoblots. Latent 
syphilis requires a prolonged treatment compared to the syndromic in-
terventions currently being discussed. What might timely accelerated 
syphilis therapy do to HIV viral load and CD4/CD8 ratios? Some of our 
HIV cases became treponemal antibody positive after supra-maximal 
therapy, but their AIDS did not resolve.

Recently, we tried to engage the South African government's AIDS ad-
visory panel in a discussion about the dangers of untreated or inade-
quately treated syphilis, and a *referenced* summary of our views, 
and the context in which they were made, can be found at 
http://www.aidsmyth.com/news/000516syphilis.htm
with some subsequent discussion at 
http://www.aidsmyth.com/news/000529syphilisdebate.htm. 

Further material can be found on the World Wide Web, at 
http://www.radio.cbc.ca/programs/ideas/Aids/index.html
a comprehensive site created to accompany the award-winning 1996 CBC 
Radio documentary on syphilis and AIDS, entitled "Deja Vu: AIDS in 
Historical Perspective." The program, most of which is available 
online for listening in Real Audio, features prominent European 
syphilis specialists voicing many of the concerns expressed above. An 
electronic mailing list, AIDSsyphilis, has also been set up to dis-
cuss these issues - to subscribe, go to:
http://www.egroups.com/subscribe/AIDSsyphilis

Scythes will be travelling to the XIII International AIDS Conference 
in Durban, staying at the South Beach Garden Court Holiday Inn, and 
would be happy to meet in person with anyone interested in pursuing 
this line of thinking further.

Kindest regards,

John Scythes 
mailto:scythes@colman.net

Colman Jones 
mailto:mail@colman.net

Community Initiative for AIDS Research
32 Beaty Avenue
Toronto, Ontario M6K 3B4 
Canada 

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