A Longitudinal Case Study of Concurrent Infection with Syphilis and Human Immunodeficiency Virus During the Early Phase

Abstract

Due to the low incidence of concurrent human immunodeficiency virus (HIV) and syphilis infection identified during the early phase, such as window period (WP), little is known about the clinical manifestations, diagnosis, and treatment efficacy at very early stages. One longitudinal study was conducted in a 42-year-old blood donor who was concurrently infected with syphilis and HIV. This blood donor was treated with a penicillin-based regimen and early antiretroviral therapy (ART). Sequential serological and nucleic acid tests were performed and the results were comparatively analyzed. A regular male donor who had two occasions of high-risk sexual behaviors 41 and 35 days before donation donated whole blood at the Shenzhen Blood Center. ART was initiated at the 28th day after donation (DAD), and syphilis treatment was received at the 49th DAD. Microbiological analysis using a fourth-generation anti-HIV enzyme-linked immunosorbent assay (ELISA) (4th GAHE) and electro-chemiluminesent immunoassay indicated a positive signal at the 6th DAD, while a third-generation anti-HIV ELISA (3rd GAHE) showed positive at the 26th DAD. All nucleic acid testing (NAT) for HIV RNA were reactive except the minipool NAT of 6 pooled samples at 117th DAD. The HIV viral load declined more than 4-log in copies per milliliter over 3 months, until reaching nondetectable levels at 246th DAD. Nevertheless, HIV-1 DNA was still detectable at 403rd DAD. Among all methods utilized, anti-treponema pallidum ELISA detected syphilis infection at the earliest time. A successful serological response to syphilis treatment was reached around the 80th DAD. Concurrent infection with syphilis and HIV during early phases did not significantly change the sensitivity of reagents in detection nor alter the therapeutic efficacy for the treatment of both pathogens, but might result in delayed HIV serological WP.

Introduction

For the last few decades, the overall incidence of syphilis has increased worldwide.¹ Syphilis often occurs with human immunodeficiency virus (HIV) infection, because these two pathogens affect the same risk groups (especially in men who have sex with men).² Concurrent infection with syphilis and HIV may change the course of virological and immunological response from a single pathogen infection. In addition, many questions, such as clinical presentation, diagnosis, and treatment for concurrent infection remain to be defined. In theory, infection by one pathogen may facilitate the infection or worsen the progression of the other pathogen. For example, syphilis may facilitate HIV transmission by producing genital ulcer to increase viral load in both semen and vaginal secretions or by leading to increased viral loads and decreased CD4⁺ cell counts.^3,4 Fortunately, syphilis can be successfully treated, however, HIV can be clinically cured only in extremely rare cases.^5,6 However, antiretroviral therapy (ART) during acute HIV infection (AHI) may compromise HIV detction because HIV-specific antibodies, antigens, and DNA/RNA are usually altered following ART.^7,8

To the best of our knowledge, concurrent window period (WP) infection by syphilis and HIV has been rarely reported due to the difficulty in tracking those infections. In this longitudinal study of a single case HIV/Syphilis coinfection, we performed a comprehensive analysis of early diagnostic results by different reagents and immune activation, inflammation, serologic, virological responses, and pathogen clearance.

Materials and Methods

Blood donor information

On April 6, 2018, a 43-year-old man donated whole blood at the Shenzhen Blood Center as his 19th visit for blood donation. Both donor questionnaire and medical interview before donation did not identify any infection risk (in particular, the donor denied any HIV risk). Moreover, regular physical examination did not reveal any abnormality. Laboratory test for donated blood revealed HIV RNA reactivity using the individual donation (ID) nucleic acid testing (NAT), while the third-generation anti-HIV ELISA (3rd GAHE) and fourth-generation anti-HIV ELISA (4th GAHE) were both negative. Although the anti-treponema pallidum (anti-TP) reagent 1 enzyme-linked immunosorbent assay (ELISA) presented the earliest positive signal for syphilis infection, other serologic screening assays were negative. During the follow-up period, the donor admitted having unprotected insertive anal intercourse twice with other men 41 and 35 days before donation (DBD). Ulceration of the external genitalia was noticed at the 28th DBD.

We followed this donor 11 times over 1 year and written informed consent was obtained each time. Whole blood was collected in EDTA 2K tubes. Plasma and peripheral blood mononuclear cells (PBMCs) were separated within 6 h after collection and stored at −80°C freezer until future use. Various tests were performed (HIV serological tests, nucleic acid tests, CD4 lymphocyte count and CD4/CD8 ratio) and the results were analyzed retrospectively.

Blood screening algorithm

Plasma samples were initially screened by two ELISA reagents and one NAT, as per the policy of batch release in China. Donor samples were individually screened for HIV-1, HCV, and HBV on the TIGRIS System using Procleix Ultrio Plus Assay (Grifols Diagnostic Solutions, Inc., Emeryville, CA). The following screening assays were used: HBsAg (Murex, DiaSorin S.p.A UK Branch, Dartford, United Kingdom), HBsAg (Beijing Wantai Biological Pharmacy Enterprise Co., Ltd., Beijing, China), anti-HCV (Ortho-Clinical Diagnostics, Raritan, NJ), anti-HCV (Lizhu Pharmaceutical Trading Co., Ltd., Zhuhai, China), 4th GAHE Genscreen ULTRA HIV Ag-Ab assay (Bio-Rad, Marnes-la-Coquette, France), 3rd GAHE (Beijing Wantai Biological Pharmacy Enterprise Co., Ltd.), anti-TP reagent 1 (DiaSorin S.p.A UK Branch), and anti-TP reagent 2 (Lizhu Pharmaceutical Trading Co., Ltd.). Samples tested by the ELISA and electro-chemiluminesent immunoassay (ECLIA) with a signal/cutoff (S/CO) ratio of ≥1.0 were reactive, and those with a S/CO ratio of <1.0 were negative. Reactive samples were retested in duplicate by the corresponding method. Samples were considered seronegative if both retests were nonreactive; those with one of two reactive retests were considered repeat reactive.

Supplementary serological tests

The first plasma donation and follow-up samples were further tested by western blot (WB, version 2.2; MP-Biomedical, Singapore), Elecsys HIV combi ECLIA (Roche Diagnostics GmbH, Penzberg, Germany), Colloidal Gold Immunochromatographic Assay (Kehua Bio-Engineering Co., Ltd., Shanghai, China), Alere Determine™ HIV1/2 (Alere Medical Co. Ltd., Matsudo-shi, Chiba-ken, Japan), Tolulized red unheated serum test (TRUST; Shanghai Rongsheng Biopharmaceutical Co., Ltd., China), and Treponema pallidum antibody serum test (Fuji Co., Ltd., Japan) following routine procedures.

Treatment

ART and benzathine penicillin G (BPG)-based syphilis treatment was initiated at the 28th and 49th days after donation (DAD), respectively. A single complete course includes BPG 2.4 million units intramuscularly per week for three consecutive weeks. The serological response to BPG was defined as either a negative TRUST result or a ≥4-fold decrease in titer 12 months after the treatment.

Supplementary NATs

Minipool-NAT

The COBAS TaqScreen MPX Test, version 2.0 (MPX 2.0; Roche Molecular Systems) was used with the simulated pooling of samples in our study. The HIV WP blood donor plasma, and follow-up blood plasma samples without dilution and 1:6 dilutions with negative plasma, were tested individually using Roche TaqScreen assays.

ID-NAT

HIV WP blood donor plasma, and follow-up blood plasma samples, were tested with both the Ultrio Plus Assay and the Procleix Ultrio Elite assay kit (Grifols Diagnostic Solutions, Inc.), as per the manufacturers' instructions. HIV-1 M RNA 95% limit of detection (LOD) is 18.0 (15.0–23.5) IU/mL of the Ultrio Elite ID-NAT assay assays, is 21.2 (18.2–25.7) IU/mL of Ultrio Plus.

HIV RNA quantitative assay

Viral loads were determined using the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 Test, version 2.0 (Roche). The minimum detection limit of HIV-1 RNA is 20 copies/mL.

HIV DNA quantitative assay

The HIV-1 Virus DNA Detection Kit (Genetic Biotek, Tianjin, China) detects HIV-1 virus DNA, which is integrated into the human genome of white cells. This kit uses pyrophosphorolysis activated polymerization technology to specifically amplify highly conserved regions within the HIV-1 virus DNA genome.⁹

CD4⁺ T cell counting

The CD4⁺ T cell count from whole blood samples was determined by standard flow cytometry procedures, using a Trucount tube on a FACSCalibur instrument (BD Biosciences, San Jose, CA).

Plasma chemistry

Alanine aminotransferase (ALT) was measured in plasma using Beckman Coulter reagents (Unicel DxC 800; Beckman and Coulter, Krefeld, Germany). The upper limit of the normal reference for ALT ranged between 5- and 50 U/liter. This study was approved by the Ethics Committee of Shenzhen Blood Center. Informed consent was obtained.

Results

Serological data

According to a 4th GAHE and ECLIA, blood specimen was HIV positive at the 6th DAD. Positiveness was also detected at the 26th DAD after using a 3rd GAHE and HIV Rapid Test. After early ART treatment, the test signal value obtained with the 4th GAHE and ECLIA showed a slight decline (Table 1). However, both 3rd GAHE and HIV Rapid Test did not show an apparent reduction of this same detection value (Table 1). HIV WB was positive starting at the 42nd DAD. Among all methods presently used, the anti-TP R1 ELISA showed highest efficiency for the detection of early syphilis infection. The S/CO value of anti-TP R1 and R2 first decreased and then increased after therapy. The time for a successful serological response after syphilis treatment was reached around the 80th DAD. The results of the serological tests after early treatment of concurrent Syphilis/HIV, during the WP infection are summarized in Table 1. ALT levels were significantly increased at F7 and F8.

Table 1.

Serological Test and Nucleic Acid Test Results Before and After Early Treatment of Human Immunodeficiency Virus/Syphilis Coinfected Blood Donor

Number of follow-up	DAD	ELISA anti-HIV		ELISA anti-TP		HIV WB	TPPA	TRUST	HIV rapid test		ECLIA anti-HIV	ECLIA anti-TP	ALT	Grifols		Roche MPX v2.0		HIV RNA (copies/mL ^a )	HIV DNA (copies/10⁶ cells)
Number of follow-up	DAD	4th GAHE	3rd GAHE	Anti-TP R1	Anti-TP R2	HIV WB	TPPA	TRUST	Colloidal gold immunochromatographic assay		ECLIA anti-HIV	ECLIA anti-TP	ALT	Ultrio plus	Panther	ID-NAT	MP6-NAT	HIV RNA (copies/mL ^a )	HIV DNA (copies/10⁶ cells)
F0	0	0.31	0.03	1.76	0.35	−	<1:80	−	−	−	0.24	0.75	14.8	+	+	+	+	5.02E+03	ND
F1	6	6.83	0.01	1.6	0.73	p24	<1:80	−	−	−	9.34	2.16	16.4	+	+	+	+	1.10E+06	592.5
F2	10	7.92	0.02	2.19	1.23	p24	<1:80	−	−	−	39.37	4.98	14.3	+	+	+	+	3.28E+05	769.3
F3	26	10.34	24.59	3.62	1.82	p24,gp160	+	−	+	+	55.82	7.42	13.1	+	+	+	+	7.17E+05	5800.9
HIV ART at 28 DAD
F4	31	10.87	23.62	8.77	4.76	p24,gp160	+	+	+	+	82.03	23.42	13.9	+	+	+	+	3.37E+03	1065.2
F5	42	8.78	24.59	11.24	12.45	p24,gp120,gp160	+	+	++	++	95.59	57.75	15.7	+	+	+	+	1.17E+02	1405.7
Syphilis treatment at 49 DAD
F6	51	10.55	24	11.03	10.41	p17,p24,gp120,gp160	+	+	++	++	103.7	46.59	18.1	+	+	+	+	8.18E+01	274.3
F7	80	10.6	23.81	6.93	6.97	p17,p24,gp120,gp160	+	−	++	++	218.5	40.99	142.5	+	+	+	+	<2.00E+01	494.3
F8	117	11.45	25	9.71	12.74	p17,p24,gp120,gp160	+	−	++	++	293.2	44.97	119.2	+	+	+	-	4.18E+01	168.8
F9	246	10.97	25	7.33	15.58	p17,p24,gp120,gp160	1:80	−	++	++	179	20.77	32.8	−	−	−	−	NDR^b	108.3
F10	345	10.83	25	6.96	15.17	p17,p24,gp41,gp120,gp160	1:80	−	++	++	201.3	21.77	26.2	−	−	−	−	NDR	114.9
F11	403	10.83	25	7	15.24	p17,p24,gp41,gp120,gp160	1:80	−	++	++	195.2	17.53	36.1	−	−	−	−	NDR	56.6

One copy of HIV-1 RNA is equivalent to 1.7 + 0.1 IU.

When the test result is “no HIV-1 RNA detected,” it is interpreted as: HIV-1 RNA is lower than 20 copies/mL and cannot be detected, or there is no HIV-1 RNA in the sample.

When the test result is <2.00E+01, it is interpreted as: HIV-1 RNA was detected, but below the detection limit (20 copies/mL).

3rd GAHE, third-generation anti-HIV ELISA; 4th GAHE, fourth-generation anti-HIV ELISA; F, follow-up sample; F0, donation sample; ND, not determined (insufficient sample volume, unable to contact, or other reasons); R1, reagent 1; R2, reagent 2.

ALT, alanine aminotransferase; ART, antiretroviral therapy; DAD, days after donation; ECLIA, electro-chemiluminesent immunoassay; ELISA, enzyme-linked immunosorbent assay; HIV, human immunodeficiency virus; ID, individual donation; IU, international unit; MP, minipool; NAT, nucleic acid testing; TP, treponema pallidum; TPPA, treponema pallidum antibody serum test; TRUST, tolulized red unheated serum test; WB, western blot.

HIV-related nucleic acid test

Transcription-mediated amplification and polymerase chain reaction methods have been routinely chosen for blood screening at our center. At the first blood donation made by the donor, all NAT methods for HIV-RNA detection were reactive. However, minipool (MP)-NAT of six samples were nonreactive at the 117th DAD. After early ART, HIV viral loads declined more than 4-log in copies per milliliter over 3 months, until reaching undetectable levels of HIV RNA NAT or HIV RNA viral load at the 246th DAD. Nevertheless, HIV-1 DNA was still detectable at the 403rd DAD even after an apparent decline. Results of the nucleic acid tests before and after early treatment of this donor are listed in Table 1.

CD4 lymphocyte count and CD4/CD8 ratio

As shown in Table 2, both CD4 count and CD4/CD8 ratio decreased significantly during acute infection. Treatment with ART and penicillin rescued the fall of both the CD4 count and CD4/CD8 ratio, despite a fluctuation at the 345th DAD was observed (Table 2).

Table 2.

Trend of CD4/CD8 Ratio After Early Treatment of Human Immunodeficiency Virus/Syphilis Coinfected Blood Donor

Number of follow-up	DAD	CD8 T cell (cells/mm)	CD4 T cell (cells/mm)	Ratio
F0	0	ND	ND	ND
F1	6	ND	ND	ND
F2	10	123	236	1.91
F3	26	716	358	0.50
HIV ART at 28 DAD
F4	31	693	384	0.55
F5	42	ND	ND	ND
Syphilis treatment at 49 DAD
F6	51	418	445	0.94
F7	80	377	450	1.19
F8	117	396	594	1.50
F9	246	254	525	2.07
F10	345	199	370	1.86
F11	403	296	522	1.76

Discussion

Here we present a comprehensive longitudinal study, including the observation of clinical manifestation, diagnosis, and treatment, based on a concurrent HIV/Syphilis infection identified during the early phase. The main purpose of this longitudinal study is to evaluate whether the diagnostic power (efficiency) of different test methods (both serological and nucleic-acid tests) is compromised in HIV/Syphilis coinfected donors before and after clinical treatment.

Syphilis disease progression may be altered in coinfected or post-treatment individuals. Previous research has shown that, in addition to functional defects of macrophages, HIV–induced breakdown of cell-mediated and humoral immunity alters the course of syphilis progression. The progression of syphilis is usually faster in HIV patients than in those not infected by this virus.¹⁰ In addition, ART usually modulates host immunity, by a series of mechanisms that are not fully understood. Although the median length of time from the initial infection to a positive syphilis serological test is 10 days (4–60 days), this median time can increase up to 32 days in individuals where an initial ELISA test is negative.¹¹

Different syphilis tests vary in sensitivity. In this case report, the length of time between the ulceration of the external genitalia (identified at the 28th DBD) to a positive serological test was 0, 6, and 10 DAD using anti-TP reagent 1, anti-TP ECLIA, and anti-TP reagent 2 tests, respectively. These data values were within the ranges observed in mono-infected syphilis patients.¹¹ These results indicated that HIV/Syphilis coinfection does not compromise the diagnostic power (efficiency) of different test methods for the detection of syphilis. However, syphilis treatment usually has a lower response rate in HIV-infected individuals as shown by slower decrease in nontreponemal titers.¹² In our case, we observed that both IgG and IgM levels decreased after syphilis treatment and a successful serological response was obtained at the 80th DAD. These data demonstrate that HIV/Syphilis coinfected individuals respond well to syphilis treatment although we are not quite sure whether HIV infection weakens the response rate or not.

A positive response to syphilis treatment requires monitoring of nontreponemal antibody titers, with more than fourfold decline and/or seroreversion to nonreactive titers. As reported, 15%–25% of patients treated during the primary stage revert to serologically nonreactive after 2–3 years.¹³ The majority of HIV-negative patients with early syphilis failed to have seroreversion at 12 months.¹⁴ Seroreversion at 6 months after treatment appears to be similar among all primary syphilis patients.¹⁵ In our study, a successful serological response to syphilis treatment was reached at ∼80th DAD. Our data is in agreement with previous findings that timely treatment of syphilis is highly effective, even in coinfection patients.¹⁶ Some previous studies have also evaluated the association of HIV status with serologic outcomes, after syphilis treatment, by comparing patients with and without HIV infection.^17,18 Unfortunately, the results of these particular studies are inconsistent, so it remains unclear whether HIV-infected individuals are less likely to achieve serologic clearance of syphilis. At least in part, these contrasting results might be related to (i) the variability in the stages of syphilis and HIV infection status, and (ii) an inconsistent definition of serological nonresponse.

Identification of the HIV WP infections is difficult. As recommended by the U.K. national guidelines, the 4th GAHE for HIV p24 detection is more applicable for shorter WP when compared to rapid tests and third generation ELISA, which typically reduces WP to 1.56 and 5.32 days, respectively.^19,20 According to BASHH/EAGA Position Statement on HIV WP (November 2014), a negative result of the fourth generation testing obtained 4 weeks after exposure is highly likely to exclude HIV infection. However, based on our current study, the WP of HIV serological testing appears to be longer in HIV/Syphilis coinfected individual.

In this case study, the 4th GAHE and ECLIA platform provided a positive signal at the 6th DAD. It had been nearly 6 weeks since the last high-risk exposure of the 41st and 35th DBD. We speculate that one possible reason for this longer WP of HIV serological testing might be that syphilis infection affects the progression of humoral response to HIV. Several studies have identified that syphilis infection decreases immune activation and the secretion of inflammatory cytokines in AHI.²¹ Li et al. have found that syphilis corrected the imbalance of Vδ1 and Vδ2 T cells in patients with AHI, by decreasing the proportion of Vδ1 T cells and increasing that of Vδ2 T cells.²¹ Both Vδ1 and Vδ2 cells can express FcgRIIIA (CD16),²² making them potential mediators of antibody-dependent cellular cytotoxicity in the context of latency reactivation and broadly neutralizing antibodies therapy. γδT cells also exhibit similar recognition mechanisms as NK cells. They can express NKG2D and KIRs, and recognize target cells expressing stress-induced ligands.²³ Binding of ligands to activating receptors on γδT cells triggers cytotoxicity by releasing cytotoxic granules and induces immune regulatory functions by producing cytokines.²⁴ However, further research is needed to improve our understanding of how gamma delta T cells could affect serotesting of concurrent infection with syphilis and HIV during early phases. Moreover, the behavior of an insertive anal intercourse could lead to a lower concentration of receptive virus, affecting the HIV dynamics and immune response. Previous research showed that insertive anal sex is less risky for HIV contamination than receptive or versatile anal sex.²⁵ This case is a typical insertive anal sex example.

In 2015, the ART guidelines from the World Health Organization recommended treatment only after HIV infection was detected.^26,27 In addition, the early initiation of ART following infection may limit the viral burden in the presence of HIV.²⁸ Qualitative HIV DNA tests are preferred for confirmation at a later stage. As shown in Table 1, we observed that, after early ART treatment, the test signal from the HIV 4th GAHE and ECLIA showed slight decline although no apparent reduction was detected by both 3rd GAHE and HIV Rapid Test. These data demonstrate that, although the HIV 4th GAHE was the most sensitive test to detect AHI before ART, the 3rd GAHE approach was the most sensitive during treatment over a limited period of time.⁸ Furthermore, this coinfected donor responds well to ART as shown by the declined HIV viral loads until reaching undetectable levels at the 246th DAD although HIV-1 DNA was detectable by the 403rd DAD (Table 1). Therefore, in accordance with previous work, our data illustrate the critical role of early stage treatment for HIV.²⁹ These data also indicate that HIV DNA can still be detected, as virus reservoir, after coinfection.

According to the background information, this blood donor presented one genital ulcer (chancre) at the 28th DBD. Previous research has shown that chancres typically appear 10–90 days after exposure.³⁰ The WP whereby the humoral response to syphilis develops is between 1 and 4 weeks after the chancre forms in primary syphilis.³¹ Apparently, coinfection appears to have limited effect toward this length of time. Anti-TP reagent 1 and anti-TP reagent 2 can detect both specific IgM and IgG antibodies. The reason S/CO values declined after treatment may partially be the fallen IgM levels and pathogen clearance.

Although this is a comprehensive longitudial follow-up study, our report also faces some limitations. First, the patient had two high-risk behaviors but, due to the lack of follow-up data, the specific infection time could not be determined. Second, this study is mainly focused on testing and treatment, the molecular mechanism(s) related to the effect of coinfection toward the immune system remains in-depth investigation. Nevertheless, based on this rare case study, we strongly believe that our current data will serve as an useful background information for future research.

Footnotes

Authors' Contributions

L.W. wrote the article with the participation of C.S.; L.W., C.S., L.L., J.L., L.W., and J.Z. designed research and analyzed data; Z.Y. contributed HIV WB testing; F.Z. provided early treatment for the blood donor; L.W., H.L., and X.Z. performed research.

Acknowledgments

The authors wish to thank Shenzhen Center for Disease Control and Prevention for providing HIV WB for this study and Shenzhen Third People's Hospital for providing early treatment for the blood donor. The authors gratefully acknowledge the blood donors who volunteered to participate in this study. We are indebted to Professor Limin Chen from the Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College for his critical review of this article.

Availability of Data and Materials

The datasets used and/or analyzed during this study are available from the corresponding author on reasonable request.

Ethics Approval and Consent to Participate

This study was approved by the Ethics Committee of Shenzhen Blood Center.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This study was supported by grants from the Medical Scientific Research Foundation of Guangdong Province (Grant No. A2020259), Shenzhen Key Medical Discipline Construction Fund (Grant No. SZXK070), and the Sanming Project of Medicine in Shenzhen (Grant No. SZSM201811092).

References

Hook EW 3rd: Syphilis. Lancet, 2017; 389:1550–1557.

Traeger

, Cornelisse

, Asselin

, et al.: Association of HIV preexposure prophylaxis with incidence of sexually transmitted infections among individuals at high risk of HIV infection. JAMA, 2019; 321:1380–1390.

Buchacz

, Patel

, Taylor

, et al.: Syphilis increases HIV viral load and decreases CD4 cell counts in HIV-infected patients with new syphilis infections. AIDS, 2004; 18:2075–2079.

Kofoed

, Gerstoft

, Mathiesen

, Benfield

: Syphilis and human immunodeficiency virus (HIV)-1 coinfection: Influence on CD4 T-cell count, HIV-1 viral load, and treatment response. Sex Transm Dis, 2006; 33:143–148.

French

, Gomberg

, Janier

, et al.: IUSTI: 2008 European Guidelines on the Management of Syphilis. Int J STD AIDS, 2009; 20:300–309.

Zou

, Glynn

, Kuritzkes

, et al.: Hematopoietic cell transplantation and HIV cure: Where we are and what next. Blood, 2013; 122:3111–3115.

Cohen

, Chen

, McCauley

, et al.: Antiretroviral therapy for the prevention of HIV-1 transmission. N Engl J Med, 2016; 375:830–839.

de Souza

, Pinyakorn

, Akapirat

, et al.: Initiation of antiretroviral therapy during acute HIV-1 infection leads to a high rate of nonreactive HIV serology. Clin Infect Dis, 2016; 63:555–561.

Liu

, Sommer

: PAP: Detection of ultra rare mutations depends on P* oligonucleotides: “sleeping beauties” awakened by the kiss of pyrophosphorolysis. Hum Mutat, 2004; 23:426–436.

10.

Johns

, Tierney

, Felsenstein

: Alteration in the natural history of neurosyphilis by concurrent infection with the human immunodeficiency virus. N Engl J Med, 1987; 316:1569–1572.

11.

Wheeler

, Agarwal

, Goh

: Dark ground microscopy and treponemal serological tests in the diagnosis of early syphilis. Sex Transm Infect, 2004; 80:411–414.

12.

Ghanem

, Erbelding

, Wiener

, Rompalo

: Serological response to syphilis treatment in HIV-positive and HIV-negative patients attending sexually transmitted diseases clinics. Sex Transm Infect, 2007; 83:97–101.

13.

Romanowski

, Sutherland

, Fick

, Mooney

, Love

: Serologic response to treatment of infectious syphilis. Ann Intern Med, 1991; 114:1005–1009.

14.

Seña

, Wolff

, Behets

, et al.: Rate of decline in nontreponemal antibody titers and seroreversion after treatment of early syphilis. Sex Transm Dis, 2017; 44:6–10.

15.

Kim

, Park

, Choi

, Lee

, Kim

: Serologic response to treatment in human immunodeficiency virus-negative syphilis patients using automated serological tests: Proposals for new guidelines. Ann Dermatol, 2017; 29:768–775.

16.

Blencowe

, Cousens

, Kamb

, Berman

, Lawn

: Lives Saved Tool supplement detection and treatment of syphilis in pregnancy to reduce syphilis related stillbirths and neonatal mortality. BMC Public Health, 2011; 11(Suppl 3):S9.

17.

Jinno

, Anker

, Kaur

, Bristow

, Klausner

: Predictors of serological failure after treatment in HIV-infected patients with early syphilis in the emerging era of universal antiretroviral therapy use. BMC Infect Dis, 2013; 13:605.

18.

Kenyon

, Osbak

, Apers

: Repeat syphilis is more likely to be asymptomatic in HIV-infected individuals: A retrospective cohort analysis with important implications for screening. Open Forum Infect Dis, 2018; 5:ofy096.

19.

Weber

, Fall

, Berger

, Doerr

: Reduction of diagnostic window by new fourth-generation human immunodeficiency virus screening assays. J Clin Microbiol, 1998; 36:2235–2239.

20.

Weber

, Orazi

, Raineri

, et al.: Multicenter evaluation of a new 4th generation HIV screening assay Elecsys HIV combi. Clin Lab, 2006; 52:463–473.

21.

, Lu

, Hu

, et al.: Syphilis infection differentially regulates the phenotype and function of γδ T cells in HIV-1-infected patients depends on the HIV-1 disease stage. Front Immunol, 2017; 8:991.

22.

, Liang

, Hong

, et al.: The potential role of CD16+ Vγ2Vδ2 T cell-mediated antibody-dependent cell-mediated cytotoxicity in control of HIV type 1 disease. AIDS Res Hum Retroviruses, 2013; 29:1562–1570.

23.

Born

, Kemal Aydintug

, O'Brien

: Diversity of γδ T-cell antigens. Cell Mol Immunol, 2013; 10:13–20.

24.

Bonneville

, O'Brien

, Born

: Gammadelta T cell effector functions: A blend of innate programming and acquired plasticity. Nat Rev Immunol, 2010; 10:467–478.

25.

Meng

, Zou

, Fan

, et al.: Relative risk for HIV infection among men who have sex with men engaging in different roles in anal sex: A systematic review and meta-analysis on global data. AIDS Behav, 2015; 19:882–889.

26.

INSIGHT START Study Group; Lundgren

, Babiker

, et al.: Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med, 2015; 373:795–807.

27.

Lifson

, Grund

, Gardner

, et al.: Improved quality of life with immediate versus deferred initiation of antiretroviral therapy in early asymptomatic HIV infection. AIDS, 2017; 31:953–963.

28.

Siliciano

, Kajdas

, Finzi

, et al.: Long-term follow-up studies confirm the stability of the latent reservoir for HIV-1 in resting CD4+ T cells. Nat Med, 2003; 9:727–728.

29.

Saag

, Gandhi

, Hoy

, et al.: Antiretroviral drugs for treatment and prevention of HIV infection in adults: 2020 Recommendations of the International Antiviral Society-USA Panel. JAMA, 2020; 324:1651–1669.

30.

Singh

, Romanowski

: Syphilis: Review with emphasis on clinical, epidemiologic, and some biologic features. Clin Microbiol Rev, 1999; 12:187–209.

31.