INTRODUCTION

Cervical cancer is a serious threat to the majority of women’s health. In developing countries, its incidence is second only to breast cancer, ranking second in female malignant tumors, and is the most common female reproductive system tumor ¹. According to the cancer report released by the International Agency for Research on Cancer under the World Health Organization, in 2020, about 604,000 women around the world were diagnosed with cervical cancer, and about 342,000 women died from the disease, among which the number of cervical cancer cases in China was about 110,000, and the number of deaths was 60,000 ². Etiological studies have found that persistent infection by human papillomavirus (HPV) is a significant factor in cervical cancer ³. HPV is a kind of virus which can be classified into low-risk human papillomavirus (LR-HPV) and high-risk human papillomavirus (HR-HPV) according to the strength of the pathogenicity or carcinogenic risk of HPV ⁴. HPV is highly host-specific and easily infects human epidermal and mucous squamous epithelium, mainly through sexual transmission⁵. HPV infection is the leading cause of most cervical cancer, anal and oropharyngeal invasive cancers and preinvasive lesions, and is also the cause of genital warts (condyloma acuminatum) and recurrent respiratory papillomatosis ⁶. Therefore, the prevention of HPV infection and intervention in the disease process after HPV infection are the key to reducing the incidence and mortality of cervical cancer.

There is evidence that maintaining the balance of vaginal microecology plays an important role in preventing female reproductive system infection, and when the vaginal microecology is destroyed, it may lead to cervical lesions ⁷. Under normal circumstances, the vaginal microecology is in a state of dynamic balance. When the loss of this dynamic balance, the immune system of the vaginal mucosa, is damaged, and foreign microorganisms are more likely to invade the reproductive tract and cause inflammation ⁸. Studies have shown that changes in the vaginal microenvironment, such as vaginal douching, bacterial vaginosis (BV), as well as sexually transmitted infections, are thought to be co-factors in the persistence of HPV infection ⁹. Studies have also found that reconstructing vaginal microecological homeostasis can reduce the risk of HPV infection ¹⁰.

Antiviral drugs are commonly used in clinical treatment for patients with HPV infection, such as recombinant human interferon α-2b gel, which can inhibit the replication of the virus and increase the immune regulation of lymphocytes to specific cytotoxicity after medication, thus playing a particular therapeutic effect ¹¹. However, with the single use of antiviral drugs, the drug interacts with the vaginal environment and affects the overall effect. Lactobacillus vaginal capsules is a kind of microecological preparation whose main ingredient is living intestinal streptococcus; it is a common drug to treat bacterial disorder vaginosis and can play a role in the decomposition of lactic acid produced by sugar and regulate the pH of the vagina ¹².

In our study, we intended to explore the correlation between HPV infection and the vaginal microecological environment and the effect of Lactobacillus vaginal capsules combined with recombinant human interferon α-2b gel on HPV infection.

PATIENTS AND METHODS

RESULTS

Inflammation between the two groups

Before therapy, there were no differences in levels of inflammatory markers between the two groups (p>0.05). After therapy, TNF-α and IL -6 levels were declined in the two groups (p<0.01). Importantly, relative to the CG, the OG presented lower levels of the above inflammatory markers after therapy (p<0.01, Fig. 1).

Fig. 1 Comparison of inflammation between the two groups. **p<0.01. 

Immune function between two groups

Prior to therapy, there were no differences in levels of immune function indexes between the two groups (p>0.05). After therapy, CD4⁺ and CD4⁺/CD8⁺ levels were elevated, while CD8⁺ levels declined in the two groups (p<0.01). Importantly, relative to the CG, the OG presented better improvements in the above immune function indexes after therapy (p<0.01, Fig. 2).

Fig. 2 Immune function between the two groups. **p<0.01. 

DISCUSSION

About 10% to 30% of adults are infected with HPV, and sexually active people are even higher, reaching 50% to 80%, and the most susceptible age is 20 to 29 years old ¹³. After HPV infection, some patients continue to be infected with high-risk HPV, cervical intraepithelial tumour-like lesions, after 10 to 15 years, the development of early cervical cancer, and then advanced cervical cancer ¹⁴. HR-HPV is the leading cause of cervical cancer, with 99% of cervical cancer HPV positive, of which HPV16 and HPV18 accounted for about 70%. HPV infection is necessary to cause cervical cancer, but the number of copies of HPV-DNA is not directly related to disease progression, and only persistent high- risk HPV infection increases the risk of cervical cancer ¹⁵. At present, HPV monitoring is the primary screening method for cervical cancer, the tracking method of cervical lesions after treatment and the indicator of the risk of cervical intraepithelial neoplasia ¹⁶.

The vaginal microecosystem is a relatively complex system among the four major human ecosystems, which plays an important role in preventing microbial invasion ¹⁷. In our study, the results showed that compared to the HPV-negative group, the HPV- positive group presented a higher abnormal rate of Lactobacillus, catalase, cleanliness, neuraminidase, and proline aminopeptidase, consistent with previous reports ^18,19. The typical vaginal microecological environment of women is Lactobacillus as the dominant bacteria ²⁰. Lactobacillus can maintain a stable pH value (pH ≤4.5) in the vagina by producing lactic acid, lactobacillin, H₂O₂, and bioactive substances so that the vaginal flora can maintain a balanced state, and through its adsorption on the vaginal mucosa, the formation of a biological barrier against pathogenic microorganisms ²¹. Hydrogen peroxide can inhibit or kill bacteria, and the function of catalase is to promote the decomposition of hydrogen peroxide, and reduce the effect of hydrogen peroxide on killing pathogens, resulting in the survival and proliferation of pathogens in the vagina, increasing HPV susceptibility ²². Reproductive system infections can also lead to changes in cleanliness, abnormal levels of neuraminidase and proline aminopeptidase, aggravate vaginal microecological environment disorders, form a vicious cycle, and increase the risk of HPV infection ²³. In addition, HPV infection may also cause oxidative stress, damage the antioxidant oxidase system in the patient, reduce the level of antioxidants, and damage cellular DNA. In the process of cellular DNA replication, HPV DNA can be transferred to the DNA of host cells, aggravating the degree of mucosal damage, further aggravating the abnormality of the vaginal microecological environment, and forming a vicious cycle ²⁴. Therefore, the vaginal flora is the first line of defense against pathogenic microorganisms.

Our study also revealed that relative to the HPV-negative group, the HPV-positive group presented a higher positive rate of BV. The reason is as follows: (1) The decrease or disappearance of vaginal Lactobacillus in BV patients provides opportunities for the growth and reproduction of other bacteria such as Gardner-bacteria and anaerobic bacteria, causing the imbalance of vaginal microecological environment, the reduction of the protective function of Lactobacillus on the vagina, and the decreased ability of vaginal virus clearance, thus susceptible to HPV infection ²⁵; (2) BV can affect the expression of vaginal local immune factors, thereby destroying the immune response and making it more susceptible to HPV infection ²⁶; (3) BV can cause the destruction of cytoskeleton protein of vaginal mucosal epithelium, accelerate the damage of vaginal mucosal epithelial cells, and increase susceptibility to HPV²⁷; (4) The sialoglycoidase produced by BV leads to the degradation of vaginal mucosal epithelial protective factors, which enables bacteria to adhere and form biofilms, further leading to the difficulty of HPV removal and the formation of persistent infection ²⁸. For these reasons, BV not only increases the susceptibility to HPV but also delays the body’s clearance of HPV.

Antiviral therapy is the preferred treatment for HPV infection, with commonly used drugs such as recombinant human interferon α-2b gel, an important glycoprotein produced by white blood cells that play a key role in fighting viral infection and has antibacterial activity against a variety of pathogens ²⁹. Interferon α-2b can inhibit cell proliferation, inhibit angiogenesis, and have cytotoxic effects on tumor cells in various ways ³⁰. On the one hand, it can bind to specific receptors on the cell surface, thereby inhibiting the growth of virus-infected cells and prolonging the cell cycle of malignant cells ³¹. On the other hand, biosynthase plays an important role in promoting cell proliferation in viral cells, and the inhibition of interferon α-2b can play a good role in inhibiting viral replication ³². In treating HPV infection, transvaginal medication can directly act on cervical epithelial cells and has a specific effect. However, the vagina has a complex microenvironment, which can produce metabolites that compete with drug receptors under the action of the microbiome, resulting in limited effects of single drugs ³³.

In this study, the observation group was given Lactobacillus vaginal capsules based on interferon α-2b, and the results manifested that relative to the CG, the OG presented a higher total effective rate. The reason may be that Lactobacillus vaginal capsule is a kind of microbial preparation, with living intestinal streptococcus as the main component ³⁴, which can increase the production of acidic substances through the decomposition of internal glycogen, thus reducing the pH value of the vaginal environment, effectively promoting the proliferation of Lactobacillus in the host body, adjusting the microecological environment, strengthening the self-purification function of the mucosal immune system, and thus enabling the mucosal immune system to rebuild more effectively ³⁵. In addition, Lactobacillus vaginal capsules play a particular role in regulating the immune system, stimulating the release of antibodies in the body and inhibiting the reproduction of bacteria ³⁶. By rebuilding a good vaginal environment and establishing a protective barrier, the effect of interferon α-2b can be reduced, and the clinical efficacy can be improved.

IL-6 and TNF-α are inflammatory factors that correlate specifically with HPV infection³⁷. When the body is infected with HPV, the levels of IL-6 and TNF-α as pro-inflammatory factors will increase abnormally ³⁸. Therefore, the body’s inflammation can be judged by observing the changes of IL-6 and TNF-α levels in the body. The results of our study manifested that relative to the CG, the OG presented lower levels of the above inflammatory markers after therapy, suggesting that Lactobacillus vaginal capsules combined with recombinant human interferon α-2b gel could suppress inflammation of the body. Similarly, Dobrohotova et al. suggested that the additional use of Lactobacillus vaginal capsules in the complex therapy of lower urinary tract infections reduced inflammation ³⁹.

Under normal circumstances, the body’s own immune system can resist the invasion of pathogenic microorganisms, but the immune system has obstacles; the resistance to viruses will decline, easy to cause viral infections, such as HPV infection ⁴⁰. The immune function of the body mainly depends on T lymphocytes. CD4⁺ can coordinate B cells, promote their differentiation and produce antibodies; CD8⁺ are viral T lymphocytes. When the body’s CD4⁺, CD8⁺, and CD4⁺/ CD8⁺ decline, the body’s immune function is disturbed and vulnerable to HPV invasion ⁴¹. Our study demonstrated that relative to the CG, the OG presented better improvements of CD4⁺, CD8⁺ and CD4⁺/CD8⁺ levels after therapy, suggesting that Lactobacillus vaginal capsule combined with recombinant human interferon α-2b gel could enhance the immune function of the body, which was following a study proposed by Ang et al. ⁴².

In addition, our study pointed out that relative to the CG, the OG presented a higher proportion of grade II-III vaginal flora density and grade II-III vaginal flora diversity. The reason is that recombinant human interferon α-2b can regulate immune responses by activating intracellular signalling pathways ⁴³. The drug acts on immune cells, such as macrophages and dendritic cells, thereby enhancing their phagocytosis ⁴⁴. Recombinant human interferon α-2b induces a series of cell signalling events by binding to specific receptors, ultimately activating and enhancing immune cells ⁴⁵. Besides, HPV infection is directly related to the dysregulation of the vaginal microenvironment and the lack of Lactobacillus, which leads to a vicious cycle of the disease ⁴⁶. After the application of recombinant human interferon α-2b, the proliferation of antiviral protein in the body was promoted, and the antiviral ability was improved ⁴⁷. At the same time, the lactobacillus vaginal capsule is vaginally administered, which takes live lactic acid bacteria as the main component and has a certain antibacterial effect, and inhibits the reproduction of harmful bacteria by producing organic acids and other antibacterial substances ⁴⁸. In addition, Lactobacillus vaginal capsules contain a large number of active lactic acid bacteria cells. After vaginal medication, it can increase the number of beneficial bacteria, inhibit the excessive reproduction of harmful bacteria, promote the balance of vaginal flora and maintain a healthy microecological environment ⁴⁹.

Moreover, the results of this study showed that there was no statistical difference in the total incidence of adverse reactions between the two groups, which reflected that the adverse reactions produced by Lactobacillus vaginal capsule combined with recombinant human interferon α-2b gel were within the acceptable range and the safety was reasonable.

In conclusion, our study indicates that HPV is significantly correlated with vaginal microecological environment, and catalase, proline aminopeptidase and BV were closely related to HPV infection. In addition, the Lactobacillus vaginal capsule combined with recombinant human interferon α-2b gel has practical clinical efficacy, which can reduce inflammation, promote immune function, improve vaginal microecological environment, and is safe in the treatment of patients with HPV infection.