Review

Potential Therapy for NeisseriaGonorrhoeae Infections WithHuman Chorionic Gonadotropin

C.V. Rao, PhD1

AbstractThe scientific evidence suggests that Neisseria gonorrhoeae (NG) infects human fallopian tubes by molecular mimicry in whichpathogens act like a ligand to bind to epithelial cell surface human chorionic gonadotrophin (hCG)/luteinizing hormone (LH)receptors. The hCG-like molecule has been identified as ribosomal protein L12 in NG coat surface. Human fallopian tube epi-thelial cells have been shown to contain functional hCG/LH receptors. As previously shown in human fallopian tube organ and cellculture studies, cellular invasion and infection can be prevented by exposing the cells to excess hCG, which would outnumber andoutcompete NG for receptor binding. Based on these data, we suggest testing hCG in clinical trials on infected women.

Keywordshuman chorionic gonadotropin, Neisseria gonorrhoeae, fallopian tubes, hCG/LH receptors

Introduction

Neisseria gonorrhoeae (NG) is 1 among the 7 other pathogens

that cause sexually transmitted diseases (STDs), also popularly

known as venereal diseases. These infections are contagious

and can be treated with antibiotics. The prevalence of NG

infections is higher among women than in men, high among

sexually active adolescents, and closely associated with an

onset of menses.1,2 According to the US Center for Disease

Control and Prevention estimates, 334 826 cases of NG infec-

tions were reported in 2012, and the infection rate has increased

by 4.1% since 2011. These numbers will be much higher world-

wide, and all the numbers are likely to be underestimates.

These infections have a high economic and human cost, in

terms of medical treatments, productivity loss in the work

place, pain, suffering, and social stigma. Left untreated, these

infections can progress into salpingitis, pelvic inflammatory

disease, increased risk of infertility, ectopic pregnancy, and

so forth. Hematogenous disseminated infection can lead to sev-

eral systemic illnesses and even death in some cases.

Fallopian tubes are commonly involved in the infections by

molecular mimicry, in which NG acts like a ligand to bind to

epithelial cell surface receptors.3 Supporting this possibility,

NG has been found to express human chorionic gonadotrophin

(hCG)-like molecule in their coat surface and human fallopian

tube epithelial cells have been shown to contain functional

hCG/luteinizing hormone (LH) receptors.4,5 The hCG-like

molecules have been identified as ribosomal protein L12

(RPL12) in NG.6,7 It is not an ortholog of hCG. It is simply a

prokaryotic single polypeptide chain of 123 amino acids with

a molecular mass of about 13 kDa. It is not glycosylated. It

is constitutively expressed, membrane associated, surface

exposed, and immunologically similar to hCG and its binding

can be blocked by hCG.6,7 It serves as a receptor sensor.6 The

RPL12 is present in both noninvasive and invasive NG pheno-

types, which suggests that RPL12 may only facilitate NG bind-

ing to hCG/LH receptors, regardless of their virulence. It is the

first structurally unrelated protein, to the author’s knowledge,

which seems to bind hCG/LH receptors in a reversible manner.

It should be interesting to determine how exactly RPL12 can

bind to hCG/LH receptors, its binding characteristics, and

whether it can activate signaling systems and cellular responses

as hCG and LH.

Binding of NG may induce other molecules such as adhesin

that seem to be required for invasion of NG into the cells.

Adhesin is not present in NG grown in culture media alone,

thus exposure to receptor-positive cells is required.6 In addition

1 Departments of Cellular Biology and Pharmacology, Molecular and Human

Genetics and Obstetrics and Gynecology, Reproduction and Development

Program, Herbert Wertheim College of Medicine, Florida International

University, Miami, FL, USA

Corresponding Author:

C.V. Rao, Departments of Cellular Biology and Pharmacology, Molecular and

Human Genetics and Obstetrics and Gynecology, Reproduction and Devel-

opment Program, Herbert Wertheim College of Medicine, Florida Interna-

tional University, 11200 SW 8th Street, GL 495 C, Miami, FL 33199, USA.

Email: crao@fiu.edu

Reproductive Sciences2015, Vol. 22(12) 1484-1487ª The Author(s) 2015Reprints and permission:sagepub.com/journalsPermissions.navDOI: 10.1177/1933719115580998rs.sagepub.com

at FLORIDA INTERNATIONAL UNIV on November 13, 2015rsx.sagepub.comDownloaded from

to adhesin, there maybe other molecules that determine the

route of some of the internalized NG.

Fallopian Tube hCG/LH Receptors

Human fallopian tubes contain hCG/LH receptors in epithelial

and muscle cell layers as well as in blood vessels.5 However,

epithelial cells contain more than smooth muscle and blood

vessels, with no difference between ciliated and nonciliated

cells.5 The receptor levels are higher in ampulla than in isthmus

and higher in secretory phase than in the proliferative phase or

in postpartum tubes.5 The tubes from postmenopausal women

contain the least amount of receptors.5

The activation of fallopian tube receptors affects the

contractility as well as increases 5-lipoxygenase, cyclooxy-

genases (COXs) -1 and -2, and the products of their catalytic

activity, that is, 5-hydroxyeicosatetraenoic acid and prosta-

glandin E2 (PGE2).5,8-10 The increased PGE2 comes from

COX-2 rather than COX-1.5,10 Treatment with hCG upregu-

lates expression of COX-2 gene by increasing the stability of

its transcripts rather than by increasing the transcription rate

of the gene.10

Fallopian tubes play a central role in the events of gamete

transport, their maturation and fertilization, early embryonic

growth and development, and its timely transport for implanta-

tion in the uterus. These events are regulated by contractions,

ciliary beat, epithelial cell secretions, and blood flow changes

that are widely attributed to eicosanoids.11-16 Through increas-

ing their formation, hCG may regulate all the these tubal events

that are important for early pregnancy.

Oviductal glycoprotein (OGP), which also plays an impor-

tant role in gamete maturation, fertilization and early embryo-

nic growth, and development, is regulated by hCG/LH.17 As

expected, the hCG-induced increase in OGP synthesis

requires the presence of its receptors and cyclic adenosine

monophosphate/protein kinase A signaling.17 Treatment of

tubal epithelial cells with hCG increases OGP gene expres-

sion by increasing the stability of its transcripts rather than

by increasing the transcription rate of the gene.17 Cocultures

of early embryos with tubal epithelial cells increase their

growth and development, more than culturing in media

alone.18-20 The hCG treatment further enhances the benefit

of coculturing, and blocking the OGP synthesis reverses the

benefit.20 These findings may explain how embryos trans-

ferred from cocultures with autologous endometrial epithelial

cells can improve pregnancy chances in women who repeat-

edly fail after the transfer of embryos cultured in media alone,

in in vitro fertilization embryo transfer procedures.21-23 The

data also suggest that hCG treatment of cocultures may fur-

ther increase the chances of pregnancy.

Endogenous LH and hCG present during the periovulatory

period and early pregnancy, respectively, or exogenous hCG

administered for ovulation induction or for any therapeutic

reasons, may act on fallopian tubes to promote the early preg-

nancy events. It now appears that certain pathogens such

as NG and others, by virtue of the expression of hCG or

LH-like molecules in their coat surfaces, can hijack these

receptors to get themselves into the cells.4,24-31

Molecular Mimicry

The receptor binding per se, which eventually enables NG to

enter human fallopian tube epithelial cells, is not adequate for

infection. This is exemplified by the observations that animal

tubes, which also contain the receptors, are not prone to NG

infection.3,4,27 In addition, other parts of human reproductive

tract are not infected to the same extent as fallopian tubes,

although they also contain these receptors.32,33 This suggests

that the susceptibility of human fallopian tubes to infection,

compared with animal tubes, could be due to molecules that

human tubes can only produce upon coming in contact with

NG. These molecules remain to be discovered. The greater

involvement of fallopian tubes than the lower reproductive

tract could be partly anatomical and the rest could be due to

molecules that only fallopian tubes epithelial cells can pro-

duce at least in abundance as compared with the other repro-

ductive tract epithelial cells. These molecules are also yet to

be identified.

The following infection scenario can be drawn from the

published studies on the NG infections and hormone cell sur-

face receptor interactions.27,34,35 However, many knowledge

gaps remain. Initially NG comes in contact with fallopian tube

epithelial cell hCG/LH receptors to bind with a low affinity.27

RPL12 in NG surface may facilitate this low affinity bind-

ing.6,7 This binding induces the synthesis of a unique adhesin

molecules that increase the binding affinity.7 Once the bind-

ing affinity is increased, NG becomes invasive and the NG–

receptor complexes undergo receptor-mediated endocytosis,

just as it happens with hCG/LH. The difference is that while

internalized hormones are destroyed in lysosomes, NG avoid

this fate by dissociating from the receptors in the endocytosis

vesicles. There could be mechanisms inside the vesicles for

the selective release of NG from the receptors. The released

NG enters cytoplasm and induces the synthesis of tumor

necrosis factor (TNF) and expresses its own genes.36 The

increased TNF causes cell damage, as blocking its synthesis

diminishes it.36 The products of NG gene expression may

ensure the survival of intracellular NG.36

Some endocytosis vesicles may take the route of transcyto-

sis, in which case vesicles get across the cell to reach basolat-

eral plasma membrane to release NG into subepithelial

spaces. What directs these vesicles is not known. It is likely

that another set of induced proteins may facilitate this route.

This goes along with the notion that all endocytosis vesicles

do not have the same destination. The NG delivered into sub-

epithelial spaces may provoke proinflammatory changes. As a

result more cells in the vicinity will get infected and vascular

permeability increases. The latter may facilitate widespread

NG dissemination, which can lead to septic arthritis, tenosy-

novitis, bursitis, periostitis, meningitis, endo-, myo-, and peri-

carditis.37 These serious complications can not only reduce

the quality of life but also lead to death in some cases.

Rao 1485

at FLORIDA INTERNATIONAL UNIV on November 13, 2015rsx.sagepub.comDownloaded from

The STDs are also caused by Chlamydia trachomatis,

hepatitis B virus, herpes simplex virus type 2, HIV, human

papilloma virus, syphilis, and trachomonas. Neither a molecular

mimicry mechanism nor any single common mechanism is

likely to explain the infections by all these diverse organisms.

Blocking the Infection

Since the initial receptor binding of NG appears to be a prere-

quisite for infection, the vicious cycle of NG binding and cel-

lular entry into human fallopian tube epithelial cells can be

prevented by exposing the tubes to excess hCG.4,24,27 Since

the binding is reversible, excess hCG molecules will simply

outnumber and outcompete the pathogen for binding of recep-

tors. The studies on human fallopian tube organ and cell cul-

tures demonstrated that indeed hCG treatment prevents

endocytosis and transcytosis of NG and decreases the infec-

tion scores.4,24,27 The NG that remains outside the cells is

probably destroyed by immunoglobulins and immune cells

present in the tubal fluids.38

Therapeutic Implications

If hCG works in organ and cell cultures, it might also work in

infected women or even in high-risk patient populations as

a preventive measure. In light of the available scientific

evidence, the above-mentioned expectations are not too

farfetched. Obviously, hCG is a physiological hormone. It is

inexpensive and nontoxic. The commonly described side

effects of hCG administration by intramuscular route are pain

at the injection site, mild bloating, stomach or pelvic pain,

nausea, vomiting, and so on, which often do not require med-

ical attention. The hCG is likely better tolerated than antibio-

tics. There are many antibiotics-associated adverse events and

they vary with the person and the type of antibiotic used.39

Allergic reactions are the most common adverse events that

require visits to hospital emergency departments.39 The hCG

is already used for other clinical indications. It may be possi-

ble to combine hCG with lower antibiotic doses to reduce the

expense and to decrease the antibiotic-associated adverse

reactions. In addition, lower antibiotic doses may reduce the

chances of developing pathogens resistance.40 Because hCG

and antibiotics work by different mechanisms, one could

anticipate that combination treatment maybe even more effec-

tive than either treatment alone.

Questions will arise about the dose, frequency, and route of

administration. The answers can only be empirical from the

experience of using hCG for other clinical indications. A good

place to start is lower doses of hCG than the commonly used

ones for infertility treatments. For example, 500 to 1000 IU

hCG was administered into tubal lumen by laproscopy and

repeation, if a single treatment does not resolve the infection.

Intratubal hCG administration may not have any adverse

effects, as has been shown for intrauterine hCG administration

to increase implantation and clinical pregnancy rates, both of

which increased.41 So what is lost by testing hCG in a clinical

trials on infected women? After all, the use of antibiotics must

be curtailed, whenever possible, to avoid developing antibiotic-

resistant pathogenic strains.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to

the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, author-

ship, and/or publication of this article.

References

1. Satterwhite CL, Torrone E, Meites E, et al. Sexually transmitted

infections among US women and men: prevalence and incidence

estimates, 2008. Sex Transm Dis. 2013;40(3):187-193.

2. Risser WL, Risser JMH, Cromwell PF. Pelvic inflammatory

disease in adolescents: a review. Texas Med. 2002;98(2):36-40.

3. Jerse AE, Rest RF. Adhesion and invasion by the pathogenic

Neisseria. Trends Microbiol. 1997;5(6):217-221.

4. Robinson Jr EN, McGee ZA. Detection of human hormone like

molecules elaborated in vitro by Neisseria gonorrhoeae. J Cell

Biochem. 1988;12B (Suppl): 30.

5. Lei ZM, Toth P, Rao ChV, Pridham D. Novel co-expression of

human chorionic gonadotropin (hCG)/human luteinizing hor-

mone receptors and their ligand, hCG, in human fallopian tubes.

J Clin Endocrinol Metab. 1993;77(3):863-872.

6. Spence JM, Clark VL. Role of ribosomal protein L12 in gono-

coccal invasion of HEc1B cells. Infect Immun. 2000;68(9):

5002-5010.

7. Spence JM, Tyler RE, Domaoal RA, Clark VL. L12 enhances

gonococcal transcytosis of polarized Hec1B cells via the lutropin

receptor. Microb Pathog. 2002;32(3):117-125.

8. Gawronska B, Paukku T, Huhtaniemi I, Wasowicz G, Ziecik AJ.

Oestrogen-dependent expression of LH/hCG receptors in pig fal-

lopian tube and their role in relaxation of the oviduct. J Reprod

Fertil. 1999;115(2):293-301.

9. Wijayagunawardane MP, Miyamoto A, Taquahashi Y, et al. In

vitro regulation of local secretion and contraction of the bovine

oviduct: stimulation by luteinizing hormone, endothelin-1 and

prostaglandins, and inhibition by oxytocin. J Endocrinol. 2001;

168(1):117-130.

10. Han SW, Lei ZM, Rao CV. Up-regulation of cyclooxygenase-2

gene expression by chorionic gonadotropin in mucosal cells from

human fallopian tubes. Endocrinology. 1996;137(7):2929-2937.

11. Ogra SS, Kirton KT, Tomasi TB, Lippes J. Prostaglandins in the

human fallopian tube. Fertil Steril. 1974;25(3):250-255.

12. Coutinho EM, Maia H. The contractile response of the human

uterus, fallipian tubes and ovary to prostaglandins in vivo. Fertil

Steril. 1971;22(9):539-543.

13. Spilman CH, Harper MJK. Effects of prostaglandins on oviductal

motility and egg transport. Gynecol Invest. 1975;6(3-4):186-205.

14. Lindblom B, Hamberger L, Wigvist N. Differential contractile

effects of prostaglandins E and F on the isolated circular and long-

itudinal smooth muscle of the human oviduct. Fertil Steril. 1978;

30(5):553-559.

1486 Reproductive Sciences 22(12)

at FLORIDA INTERNATIONAL UNIV on November 13, 2015rsx.sagepub.comDownloaded from

15. Verdugo P, Rumery R, Tam PY. Hormonal control of oviductal

ciliary activity: effect of prostaglandins. Fertil Steril. 1980;

33(2):193-196.

16. Lindblom B, Anderson A. Influence of cyclooxygenase inhibitors

and arachidonic acid on contractile activity of the human fallopian

tube. Biol Reprod. 1985;32(3):475-479.

17. Sun T, Lei ZM, Rao ChV. A novel regulation of the oviductal gly-

coprotein gene expression by luteinizing hormone in bovine tubal

epithelial cells. Mol Cell Endocrinol. 1997;131(1):97-108.

18. Bongso A, Ng SC, Sathananthan H, Ng PL, Rauff M, Ratnam SS.

Improved quality of human embryos when co-cultured with

human ampullary cells. Hum Reprod. 1989;4(6):706-713.

19. Yeung WSB, HO PC, Lay EYL, Chan STH. Improved develop-

ment of human embryos in vitro by a human oviductal cell co-

culture system. Hum Reprod. 1992;7(8):1144-1149.

20. Mishra S, Lei ZM, Rao ChV. A novel role of luteinizing hormone

in the embryo development in cocultures. Biol Reprod. 2003;

68(4):1455-1462.

21. Bongso A, Marshall B, Ng SC, et al. Improved pregnancy rate

after transfer of embryos grown in human fallopian tubal cell

co-culture. Fertil Steril. 1992;58(3):569-574.

22. Jayot S, Parneix Y, Verdaguer S, Discamps G, Audebert A,

Emperraire JC. Coculture of embryos on homologuous endome-

trial cells in patients with repeated failures of implantation. Fertil

Steril. 1995;63(1):109-114.

23. Simon C, Mercader A, Garcia-Velasco J, et al. Coculture of

human embryos with autologous human endometrial epithelial

cells in patients with implantation failure. J Clin Endocrinol

Metab. 1999;84(8):2638-2646.

24. Gorby GL, Clemsen CM, Barley LR, McGee ZA. Effect of human

chorinoc gonadotropin (hCG) on Neisseria gonorrheoeae invasion

of and IgA secretion by human fallopian tube mucosa. Microb

Pathog. 1991;10(5):373-384.

25. Maruo T, Cohen H, Segal SJ, Koide SS. Production of

choriogonadotropin-like facor by a microorganism. Proc Natl Aca

Sci U S A. 1979;76(12):6622-6626.

26. Hussa RO. Biosynthesis of human chorionic gonadotropin.

Endocr Rev. 1980;1(3):268-294.

27. Spence JM, Chen JC, Clark VL. A proposed role for the lutropin

receptor in contact-indicuble gonoccal invasion of Hec1b cells.

Infect Immun. 1997;65(9):3736-3742.

28. Acevedo HF, Pardo M, Campbell-Acevedo E, Domingue GJ.

Human choriogonadotropin-like material in bacteria of different

species: electron microscopy and immunocytochemical studies

with monoclonal and plyclonal antibodies. J Gen Microbiol.

1987;133(3):783-791.

29. Falkow S. Bacterial entry into eukaryotic cells. Cell. 1991;65(7):

1099-1102.

30. Bliska JB, Galan JE, Falkow S. Signal transduction in the mam-

malian cell during bacterial attachment and entry. Cell. 1993;

73(5):903-920.

31. Castellanos Sanchez VO, Gomez-Conde E, Rocha-Garcia RD, et

al. Chorionic gonadotropin hormone receptors on Taenia solium

and Taenia crassiceps cysticerci in culture. J Parasitol. 2009;

95(6):1287-1294.

32. Rao ChV. An overview of the past, present and future of nongo-

nadal LH/hCG actions in reproductive biology and medicine. Sem

Reprod Med. 2001;19(1):7-17.

33. Lei ZM, Rao CV. The past, present and future of nongonadal LH/

hCG actions in reproductive biology and medicine. Mol Cell

Endocrinol. 2007;269(1-2):2-8.

34. Shaw JH, Falkow S. Model for invasion of human tissue culture

cells by Neisseria gonorrheoeae. Infect Immun. 1988;56(6):

1625-1632.

35. Chen JC-R, Bavoli P, Clark VL. Enhancement of the invasive

ability of Neisseria gonorrhoeae by contact with Hec1B, an ade-

nocarcinoma endometrial cell line. Mol Microbiol. 1991;5(6):

1531-1538.

36. McGee ZA, Clemens CM, Jensen RL, Klein JJ, Barley LR, Gorby

GL. Local induction of tumor necrosis factor as a molecular

mechanism of mucosal damage of gonococci. Microb Pathog.

1992;12(5):333-341.

37. Chue PWY. Gonorrhea-its natural history, oral manifestations,

diagnosis, treatment, and prevention. J Am Dent Assoc. 1975;

90(6):1297-1301.

38. Moghissi KS. Human fallopian tube fluid. I. Protein composition.

Fertil Steril. 1970;21(12):821-829.

39. Shehab N, Patel PR, Srinivasan A, Budnitz DS. Emergency

department visits for antibiotic-associated adverse events. Clin

Infect Dis. 2008;47(6):735-743.

40. Meredith HR, Srimani JK, Lee AJ, Lopatkin AJ, You L. Collec-

tive antibiotic tolerance: mechanisms, dynamics and intervention.

Nat Chem Biol. 2015;11(3):182-188.

41. Santibanez A, Garcia J, Pashkova O, et al. Effect of intrauter-

ine injection of human chorionic gonadotropin before embryo

transfer on clinical pregnancy rates in vitro fertilization

cycles: a prospective study. Reprod Biol Endocrinol. 2014;

12(9):1-5.

Rao 1487

at FLORIDA INTERNATIONAL UNIV on November 13, 2015rsx.sagepub.comDownloaded from