Serologic Response to Treatment in Syphilis

Serologic monitoring is the way to determine adequate treatment response, which is typically defined as a fourfold decline in Rapid Plasma Reagin (RPR) or Veneral Disease Research Laboratory (VDRL) titer within 6 months of treatment for patients with primary or secondary syphilis and within 12 months of treatment for patients with early latent syphilis. Studies documented close to 100% rate seroreversion 1 -2 years after penicillin treatment, depending on the stage of syphilis and duration of symptoms. HIV co-infection has several effects on the presentation, diagnosis, disease progression, and therapy of syphilis. Unusual syphilis serologic titers have been reported in HIV-infected patients, with either unexpected high or low titer, as well as delayed serologic response at the time of diagnosis. There are several studies concerned to syphilis serological treatment response comparing HIV-infected and HIV-negative patients. Some studies reported a slower serological response in HIV infected patients. A recent study showed that the use of high active antiretroviral therapy (HAART) and the routine use of macrolides for the prevention of opportunistic infections may reduce syphilis serologic failure rates among HIV-infected patients who have syphilis. Penicillin G, administered parenterally, is the preferred drug for treating all stages of syphilis (French et al., 2009; Workowski & Berman, 2010). Treatment failure can occur with any regimen. Assessing response to treatment frequently is difficult, and definitive criteria for cure or failure have not been established. According to the CDC guidelines recommendations, clinical and serologic evaluation should be performed 6 months and 12 months after treatment of patients with primary or secondary syphilis; more frequent evaluation might be prudent if follow-up is uncertain. Patients who have signs or symptoms that persists or recurs or who have sustained fourfold increase in nontreponemal test titer probably failed treatment or were reinfected. The latent syphilis is not transmitted sexually; the objective of treating patients with this stage of disease is to prevent complication. Quantitative nontreponemal serologic tests should be repeated at 6, 12, and 24 months for followup. Limited information is available concerning clinical and serological follow-up of patients who have tertiary syphilis. HIV-infected persons should be evaluated clinically and serologically for treatment failure at 3, 6, 9, 12, and 24 months after therapy (Workowski & Berman, 2010). Usually, treatment failure cannot be distinguished from reinfection with T. pallidum; in these cases a CSF analysis is recommended.


Introduction
Serologic monitoring is the way to determine adequate treatment response, which is typically defined as a fourfold decline in Rapid Plasma Reagin (RPR) or Veneral Disease Research Laboratory (VDRL) titer within 6 months of treatment for patients with primary or secondary syphilis and within 12 months of treatment for patients with early latent syphilis. Studies documented close to 100% rate seroreversion 1 -2 years after penicillin treatment, depending on the stage of syphilis and duration of symptoms. HIV co-infection has several effects on the presentation, diagnosis, disease progression, and therapy of syphilis. Unusual syphilis serologic titers have been reported in HIV-infected patients, with either unexpected high or low titer, as well as delayed serologic response at the time of diagnosis. There are several studies concerned to syphilis serological treatment response comparing HIV-infected and HIV-negative patients. Some studies reported a slower serological response in HIV infected patients. A recent study showed that the use of high active antiretroviral therapy (HAART) and the routine use of macrolides for the prevention of opportunistic infections may reduce syphilis serologic failure rates among HIV-infected patients who have syphilis. Penicillin G, administered parenterally, is the preferred drug for treating all stages of syphilis (French et al., 2009;Workowski & Berman, 2010). Treatment failure can occur with any regimen. Assessing response to treatment frequently is difficult, and definitive criteria for cure or failure have not been established. According to the CDC guidelines recommendations, clinical and serologic evaluation should be performed 6 months and 12 months after treatment of patients with primary or secondary syphilis; more frequent evaluation might be prudent if follow-up is uncertain. Patients who have signs or symptoms that persists or recurs or who have sustained fourfold increase in nontreponemal test titer probably failed treatment or were reinfected. The latent syphilis is not transmitted sexually; the objective of treating patients with this stage of disease is to prevent complication. Quantitative nontreponemal serologic tests should be repeated at 6, 12, and 24 months for follow-up. Limited information is available concerning clinical and serological follow-up of patients who have tertiary syphilis. HIV-infected persons should be evaluated clinically and serologically for treatment failure at 3, 6, 9, 12, and 24 months after therapy (Workowski & Berman, 2010). Usually, treatment failure cannot be distinguished from reinfection with T. pallidum; in these cases a CSF analysis is recommended.

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Anti-treponemal antibodies
Treponemal test antibody titers should not be used to assess treatment response. Most patients who have reactive treponemal tests will have reactive tests for the reminder of their lives, regardless of treatment or disease activity. However, the disappearance of reactivity in the treponemal tests after treatment of immunocompetent patients and over time has been reported. Schoeter et al. reported that 14% of patients with early syphilis lost their reactivity in the FTA-abs test within 2 years after treatment (Schroeter et al., 1972). Another study demonstrated that in patients with first episode syphilis, 24% of had a non-reactive FTA-abs and 13% had a nonreactive MHA-Tp in 3 years (Romanowski et al., 1991). A prospective, cohort treatment study of 261 patients with early syphilis that had 1 year serologic follow-up with FTA-abs or MHA-TP found seroreversion in 9% and 5% of cases, respectively. No association between HIV-seropositivity and treponemal specific test seroreversion was demonstrated (Augenbraun et al., 1998). Castro et al. performed a study of serologic follow-up of small number of patients with early syphilis. Of the 54 patients evaluated 6 months after therapy, 70% had at least twofold titer decrease when using the specific passive agglutination test (TP.PA); only 22 patients returned for 12 months evaluation, and 19 (86%) had decreased antibody titer. Seroreversion for antitreponemal antibodies were not found in this study (Castro et al., 2001). Other studies were performed by Western Blot technique, which provides analyses of reactivity against each specific antigenic fraction. Kim et al. observed a significant loss of anti-Tp47 after treatment of primary syphilis, with complete seroreversion in 11 months (Kim et al., 1989). George group studied 124 persons with clinically diagnosed syphilis by using densitometric quantization and spreadsheet normalization to refine the parameters defining treponemal WB for syphilis. The reactivity against Tp47 was 100% before treatment, while 28% had lost anti-Tp47 over 12 months after treatment (Fraser et al., 1998). More studies are necessary to state if a specific treponemal protein can be used as a potential marker for monitoring treatment.

Specific IgM
For long time, the utility of IgM in the diagnosis of syphilis has been discussed. Although there have been multiple studies addressing the use of IgM, the results have conflicted www.intechopen.com Please use Adobe Acrobat Reader to read this book chapter for free.
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somewhat. In the past, a study for quantitative evaluation of the FTA-abs-IgM and VDRL in treated and untreated syphilis revealed sera remained reactive with increased titers for more than one year after treatment in 19.5% patients with primary and 15% patients with secondary syphilis. In follow-up of nine patients with secondary syphilis, FTA-abs-IgM and VDRL titers showed only partial agreement during the course of observation. The FTA-abs-IgM titer usually reverted to non-reactivity later than de VDRL dilutions, indicating that VDRL was better for monitoring treatment (Luger et al., 1977). Actually, the results of specific IgM tests, either by Western Blot or ELISA for capture of IgM, are essential in the diagnosis of congenital syphilis as well as in the recognition of reinfection; they indicate the need for treatment and are useful in the assessment of the effectiveness of therapy (Schmidt et al., 1994).
McMillan & Young analyzed reactivity in VDRL test and Mercia IgM-Elisa (IgM-EIA) after treatment of 229 patients with early syphilis. The seroreversion observed for IgM-EIA and VDRL were respectively 62% and 41%, at 3 months follow-up, and 1 year after treatment the IgM-EIA were negative in 92% patients while VDRL were negative in 70% cases. A fourfold or greater decrease in VDRL titer occurred in 99% of patient at 3 and 12 months. It was concluded that the Mercia IgM EIA is as sensitive as VDRL in monitoring treatment of primary syphilis, but not as sensitive as the finding of a fourfold or eightfold decrease in VDRL titer in patients treated for secondary or early latent infection (McMillan & Young, 2008). A study to evaluate Treponema pallidum-specific IgM as marker of infectious syphilis in human immunodeficiency virus (HIV)-infected patients was performed with 20 samples from HIV-infected patients with untreated syphilis and follow-up at 3, 6 or 12 months after treatment. The IgM detection detection by Mercia-EIA appears to be a reliable marker for untreated syphilis in HIV-infected patients with primary or secondary syphilis. After treatment, IgM was no longer detected after three months in the majority of patients (87%) and was either negative or equivocal in all patients after six and 12 months (Rotty et al., 2010). It has also been suggested that detection of syphilis specific IgM may correlate with active disease and assist in differentiating active from past and successfully treated syphilis.

Syphilis in HIV-infected patients
For most HIV-infected persons, serologic tests are accurate and reliable for the diagnosis of syphilis and for following a patient's response to treatment. However, atypical syphilis serologic tests results can occur in HIV-infected persons. Most reports have involved serologic titers that were higher than expected, but false-negative and delayed appearance of seroreactivity or fluctuating titers also have been reported (Palmer et al., 2003). When serologic test do not correspond with clinical findings suggestive of early syphilis, use of others tests should be considered, such as biopsy, darkfield microscopy or polymerase chain reaction. Besides studies of syphilis serologic response rate, several authors have evaluated the time to serologic response according to HIV status, with conflicting results. Some studies found a slower serologic response in HIV infected patients, but other did not. Also, a higher risk of serological failure was associated with HIV infection (Ghanem et al., 2007;Gonzalez-Lopez et al., 2009;Kofoed et al., 2006;Malone et al., 1995;Telzak et al., 1991;Walter et al., 2006;Yinnon et al., 1996).

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Neurosyphilis should be considered in the differential diagnosis of neurological disease in HIV-infected person. For patients whose nontreponemal test titers do not decrease fourfold within 6-12 months therapy, CSF examination and retreatment also should be strongly considered (Workowski & Berman, 2010).

Pre-HAART
According to CDC guidelines, HIV infected person should be evaluated clinically and serologically for treatment failure at 3, 6, 9, 12 and 24 months. If after therapy, nontreponemal titers do not decline fourfold during 12-24 months or titers rise fourfold, at any time, it might be indicative of treatment failure. A higher risk of serological failure was associated with HIV infection. Telzak et al. performed a retrospective review of response to standard therapy in HIVinfected patients with primary or secondary syphilis. They reported that in patients with primary syphilis, HIV infected patients were less likely to have a fourfold or greater RPR decrease or seroreversion within 6 months of treatment compared with HIV negative patients (P = 0.03). Patients with secondary syphilis had similar serological response after treatment, regardless of HIV status (Telzak et al., 1991). Malone et al reported a relapse or failure rate of 18% in 56 HIV positive patients with follow-up for a mean of 28 months. Relapse occurred more than 12 months after initial therapy in 6 of 10 patients (60%) who experienced relapse; 5 patients experienced multiple relapses. Treatment failure was not related with CD4 count or to a specific antimicrobial regimen. However, the results suggest that patients with clinical evidence of secondary syphilis or with reactive cerebrospinal fluid VDRL test titers were at highest risk of subsequent relapse or treatment failure when monitored for an average of 2 years (Malone et al., 1995). Rolfs et al. performed a study of randomized trial of enhanced therapy for early syphilis in 541 patients including 101 patients who had HIV infection. Patients were treated with 2.4 mU benzathine penicillin G with or without enhanced therapy consisting of 2 g of amoxicillin and 500 mg of probenecid 3 times daily for 10 days. After 1 year follow-up, 14% of patients were serologically defined as treatment failures; the serologic failure rate was higher in HIV infected patients. Enhanced treatment with amoxicillin and probenecid did not improve the outcomes, and the authors concluded that CDC recommendations for treating early syphilis are adequate for most patients, whether or not they have HIV infection (Augenbraun et al., 1998). Ghanem and collaborators performed a comparative study of serological response to syphilis treatment in 129 HIV positive and 168 HIV negative patients attending sexually transmitted diseases clinics between 1992 and 2000. Serologic failure was defined as lack of a fourfold drop in RPR titer by 400 days after treatment or a fourfold increase titer between 30 and 400 days. They found 22 serologic failure (17%) in HIV positive groups and 5 in HIV negative group (p < 0.001). The median times to successful serological responses were 278 and 126 days, respectively for HIV positive and HIV negative groups (p < 0.001). The difference in serologic failure rates was significant in the subgroup of early syphilis, while the difference in median times to successful serologic response was also significant in the subgroup of late latent syphilis. A higher risk of serologic failure was associated with HIV infection (Ghanem et al., 2007).

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A study of 41 cases of syphilis diagnosed in HIV-1 infected patients revealed treatment failure in 10% (4 patients) in 7 months follow-up. Also, syphilis was associated with decrease in CD4 cell count and an increase in HIV-RNA levels, and both improved after syphilis treatment (Kofoed et al., 2006). The evaluation of 64 HIV seropositive patients and matched controls retrieved a slower serologic response in HIV infected patients. The HIVpositive patients with initial RPR less than 1:32 experienced a significantly slower decrease in RPR at 12 months than did the controls (P < .001) (Yinnon et al., 1996). Another study by Agmon-Levin et al. analyzed response to recommended treatments of 81 patients which completed 12 months follow-up. Treatment success was documented in 26%, a high rate of serofast (41%) and treatment failure (33%) were found. The immune response correlated with immune status of the patients, the mean CD4 counts were higher and HIV viral load were lower in patients with successful treatments (Agmon-Levin et al., 2010). The increased prevalence of serofast reaction has been reported in co-infected patients previously. This might be attributed to HIV associated hyperglobulinaemia or a longer period of time (2-5 years) required for VDRL levels to decline in HIV infected patients, especially those with prolonged infection or low VDRL levels, lower than 1:8 (Manavi & McMillan, 2007). González-López et al. performed a longitudinal, retrospective study in a cohort of HIV positive and HIV negative patients with syphilis. Serologic failure was observed in 29.6% (37/125) of HIV positive patients and 11.2% (7/62) HIV negative patients (odds ratio, 3.3; p < 0.05). A slower serologic response to treatment was demonstrated in men HIV infected patients with late stage syphilis. HIV negative patients responded more frequently to treatment, but after 2 years follow-up, both groups shared similar response rates (Gonzalez-Lopez et al., 2009). Another study found that HIV infected patients had greater rate of incident syphilis compared with HIV uninfected. Also, HIV infected patients had a greater likelihood to decline in RPR test titer and serologic failure (Horberg et al., 2010). Others reported no association between serologic failure for syphilis treatment and patient's HIV status. Manavi et al. performed a study to compare outcome of syphilis treatment in HIV infected and uninfected patients. Patients with diagnosis of syphilis who had 24 months follow-up syphilis serology included 161 HIV negative and 129 HIV positive patients. The lack fourfold decrease of VDRL test titer within 12 months in absence of history of re-infection was considered as treatment failure. After 12 months, 63% of HIV negative and 70% of HIV positive patients were treated (p = 0.04). HIV serologic status were not associated with success of treatment, and treatment failure in a proportion of HIV positive patients was due to slower decline in VDRL titer rather than lack of response to treatment (Manavi & McMillan, 2007). Seroreversion of reactive antibodies in patients previously treated for syphilis have been reported in patients with AIDS (Haas et al., 1990;Johnson et al., 1991). Haas analyzed sera from 90 HIV positive and 19 HIV negative men observed for a mean follow-up of 4 years. None of the HIV seronegative individuals lost reactivity to a treponemal test, whereas 7% of the seropositive asymptomatic individuals and 38% of those with symptomatic HIV infection had loss of reactivity. Symptomatic HIV infection was associated with loss of reactivity, as a CD4 count less than 200 cells/uL, a CD4/CD8 ratio less than 0.6, a single prior episode of syphilis, and a low VDRL titer at the time of the last documented episode of syphilis (Haas et al., 1990). Johnson found that 10% (3/29) patients with AIDS had loss of reactivity for both the hemagglutination (TPHA) and FTA-abs over a period of 3 years;

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whereas no seroreversion was observed in the 29 controls (Johnson et al., 1991). Janier et al evaluated the long-term outcome of syphilis treponemal tests in a cohort of HIV positive male homosexuals with a history of treated syphilis (69 patients) as compared with HIV negative controls (49 patients). The decrease in VDRL titers was not different between 2 groups (p = 0.053). Time to seroreversion was shorter in HIV positive patients for TPHA (p = 0.009) and FTA-abs test (p = 0.001). The seroreversion of the FTA-abs test was related to a low baseline CD4 cell count (p = 0. 003), while the seroreversion of TPHA and VDRL were not related. After adjustment for the CD4 cell count, only TPHA titer had significant decrease and seroreversion in HIV positive patients (French et al., 2009). However, another study found no association between HIV seropositivity and seroreversion of treponemal antibodies, in patients treated for early syphilis (Augenbraun et al., 1998). Also, seroreversion of treponemal antibodies had been reported in immunocompetent patients treated for early syphilis (Schroeter et al., 1972) or first episode of syphilis (Romanowski et al., 1991).

Post-HAART
Antiretroviral therapy significantly reduced the time to achieve response to syphilis treatment in HIV-positive patients (Gonzalez-Lopez et al., 2009). Farhi et al. evaluated the effect of HIV on clinical and serologic features of syphilis at baseline and during follow-up in the pos-HAART era, in a retrospective cohort study of patients with syphilis treated according to the European guidelines. Serologic failure was defined as either a fourfold rise in VDRL titers 30-400 days after treatment or a lack of fourfold drop in VDRL titers at 270-400 days post treatment. Among 144 informative syphilis cases, a lower rate of serologic response was observed in HIV infected patients, however this difference was not significant (91.8% vs. 98.3%, p = 0.14). Also, a median delay to serologic response was similar in both group of patients (p = 0.44), HIV positive (117 days) and in HIV negative (123 days). Serologic failure was significantly associated with a history of previous syphilis (p < 0.05). The authors concluded that effect of HIV on serologic response to syphilis treatment is minimal or absent for patients under HAART treatment (Farhi et al., 2009;Farhi & Dupin, 2010). Another study evaluated whether the use of HAART impact syphilis serologic responses. Serologic failure was defined as the lack of fourfold decrease in RPR titers 9 -12 months after therapy or a fourfold increase in titers a month or later after therapy. A total of 71 cases among 180 patients with syphilis presented serologic failure, and the median follow-up time was 5.3 years. CD4 cells count of < 200 cells/mL at the time of syphilis diagnosis was associated with an increased risk of serologic failure. The use of HAART was associated with 60% reduction in the rate of serologic failure, independent of concomitant CD4 cell response (Ghanem et al., 2008).

Neurosyphilis
Central neural system (CNS) involvements can occur during any stage of syphilis. CSF laboratory abnormalities are common in persons with early syphilis, even in the absence of clinical neurological findings. A CSF examination should be performed when clinical evidence of neurologic involvement is observed, including ocular manifestations frequently associated with neurosyphilis. There is no gold standard test to diagnose neurosyphilis. According to the diagnostic criteria, neurosyphilis can be defined in two categories,

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confirmed and presumptive, both can occur at any stage of syphilis. Confirmed neurosyphilis presents reactive CSF VDRL, while presumptive neurosyphilis is defined when patients present clinical signs or symptoms consistent with syphilis without an alternate diagnosis to account for these, non reactive CSF VDRL and CSF pleocytosis or elevated protein (Ghanem, 2010). A positive VDRL results establishes a diagnosis of neurosyphilis, but negative VDRL does not exclude it. The use of CSF RPR is not currently recommended, because RPR is less specific in CSF. The CSF FTA-abs test is less specific than the VDRL for diagnosis of neurosyphilis, but it is highly sensitive. A negative CSF FTA-abs test excludes the diagnosis of neurosyphilis (Workowski & Berman, 2010). An alternative CSF tests to diagnose neurosyphilis in HIV infected patients had been proposed when the CSF VDRL is nonreactive. The combination of the CSF FTA-abs and assessment of CSF B cells can be used to identify syphilis patients with and without neurosyphilis when the CSF VDRL is non reactive (Marra et al., 2004c). According to the European guidelines, a patient should be treated as for neurosyphilis in the following conditions: reactive CSF VDRL and treponemal antibody tests (TP hemagglutination assay or FTA-abs), WBC-CSF exceeds 10/mm 3 and IgG index is 0.70 or higher or the IgM index is 0.10 or higher in CSF (Goh & van Voorst Vader, 2001). A study by Marra et al demonstrated that a serum RPR titer ≥ 1:32 is predictive of neurosyphilis in all patients with syphilis and that a peripheral blood CD4 cell count ≤ 350 cell/uL is an additional risk factor for neurosyphilis in HIV infected patients. Also, the risk associated with these parameters is independent of previous syphilis therapy and stage of syphilis (Marra et al., 2004a). If CSF pleocytosis was present initially, a CSF examination should be repeated every 6 months until the cell count turn to normal (Workowski & Berman, 2010). The success of therapy in patients with symptomatic neurosyphilis is assessed by resolution of symptoms and signs, and normalization of CSF abnormalities, including pleocytosis, elevated protein concentration or a reactive CSF VDRL test. If neurosyphilis is asymptomatic, normalization of CSF measures is the only means of assessing treatment success (Workowski & Berman, 2010). After therapy, the changes in CSF VDRL or CSF protein occur more slowly than cell counts, and persistent abnormalities might be less important. The leukocyte count is a sensitive measure of the effectiveness of therapy (Marra et al., 2000;Marra et al., 2004b). Resolution of all serum and CSF abnormalities were resolved by 30 weeks in most patients not infected with HIV (Marra et al., 1996). Another study by the same group found that in most instances, normalization of serum RPR titer correctly predicts normalization of CSF and clinical measures after neurosyphilis treatment and follow-up lumbar puncture can be avoided. However, using the serum RPR criteria, 12-37% of individuals can be misclassified as experiencing treatment success, and among HIV infected patients, misclassification is most common in those not receiving anti-retroviral therapy (Marra et al., 2008). A study found that resolution of CSF abnormalities was slower in patients infected with HIV after treatment of neurosyphilis (Marra et al., 1996), particularly if the peripheral blood CD4 cells count is lower than 200 cell/uL (Marra et al., 2004c). A study of neurosyphilis in a clinical cohort of HIV-1 infected patients found that HAART therapy to reverse immunosupression may help mitigate neurological complication of syphilis. In this cohort, the degree of immunosuppression, as measured by CD4 cell count,

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was an independent risk factor for developing neurosyphilis, and the use of HAART reduced the odds of neurosyphilis by 65%. Among patients diagnosed and treated for neurosyphilis, there was a trend for decreased risk of serological failure in patients who received six or more months of HAART therapy during a median follow-up of 4.3 years (Ghanem et al., 2008).

Syphilis during pregnancy and congenital syphilis
All women should be screened serologically for syphilis early in pregnancy. Serologic testing should be performed at 28-32 weeks' gestation and repeated at delivery. Also, any woman who delivers a stillborn infant after 20 weeks' gestation should be tested for syphilis. Serologic titers can be checked monthly in women at high risk for reinfection or in geographic areas in which the prevalence of syphilis is high. If serological screening was performed by treponemal antibody testing, pregnant with reactive results for treponemal antibodies should have confirmatory testing with nontreponemal tests with titers (Workowski & Berman, 2010). Transplacental infection can occur at any stage pregnancy (Wicher & Wicher, 2001). Most cases of congenital syphilis occur as a result of a failure to detect and treat syphilis in pregnant women. The failure of treatment and congenital syphilis has been reported (Lasfargue et al., 2009;Marangoni et al., 2008). Regardless of the regimen used to treat syphilis during pregnancy, clinicians should recognize the possibility of occasional treatment failures and the importance of adequate follow-up of infants at risk for congenital syphilis (Conover et al., 1998). Factors that contribute to treatment failure include maternal stage of syphilis (early stage syphilis), advancing gestational age at treatment, higher VDRL titers at treatment and delivery, and a short interval from treatment to delivery, defined as ≤30 days, and these factors can be used to target neonates at high risk for congenital syphilis (Sheffield et al., 2002). The diagnosis of congenital syphilis is based both, on a clinical evaluation and on laboratory investigations. Diagnosis is complicated because more than half of all infants are asymptomatic at birth, and sign in symptomatic infants may be subtle and nonspecific. All infant born to women who have reactive serologic test for syphilis should be examined thoroughly for evidence for congenital syphilis, darkfield microscopy examination of suspicious lesions or body fluids also should be performed. Pathologic examination of the placenta or umbilical cord using specific fluorescent anti-treponemal antibody staining is suggested. Also, infants born to mothers who have reactive nontreponemal and treponemal test results should be evaluated with quantitative nontreponemal serological test (VDRL or RPR) performed on infant serum. It is not necessary to conduct a treponemal test on a newborn's serum, however a test to detect immunoglobulin IgM can be recommended (Workowski & Berman, 2010). The detection of specific IgM is currently the most sensitive serological method, and the presence of specific IgM should be considered as evidence of a congenital T. pallidum infection (Herremans et al., 2010). In the past, a retrospective analysis of the serologic response to treatment of syphilis during pregnancy was performed. Treatment response was evaluated by comparing each posttreatment titer of a patient to her pre-treatment titer, and it was classified as a positive response ( ≥ fourfold titer decline) or a negative response (< fourfold titer decline). A

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Potential markers
A specific anti-treponemal IgM-EIA may be helpful in monitoring the serological response to treatment in RPR/VDRL negative primary syphilis (French et al., 2009). Recently, a study examined the relationship between neurosyphilis and CSF concentration of CXCL13 in HIV infected patients with syphilis. CXCL13 is a B cell chemoattractant chemokine (C-X-C motif) ligant 13. They found that, compared to patients with uncomplicated syphilis, CSF CXCL13 concentration is significantly higher in patients with both asymptomatic and symptomatic neurosyphilis, and CSF CXCL13 concentration declines after neurosyphilis treatment (Marra et al., 2010). This may be particularly useful marker for diagnosis and treatment response evaluation of neurosyphilis in HIV infected patients (Marra et al., 2010).

Conclusion
There is no direct microbiologic test of cure of syphilis disease. Treatment response in current practice can be defined clinically and/or serologically by regular follow-up of quantitative serologic test for nontreponemal antibody (VDRL or RPR). Also, it is difficult to distinguish relapse from reinfection. The specific IgM antibodies may be helpful in this issue. The most relevant markers of treatment response are essential to improve the followup accuracy. Current research should focus on stronger efficacy assessment tool than the actual nontreponemal serology in use. The search for direct T. pallidum identification methods such as exploring molecular marker by T.pallidum specific polymerase chain reaction may be a promising approach.

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