The Vaginal Microbiome and Host Health: Implications for Cervical Cancer Progression

The vaginal microbiome plays a crucial role in maintaining host health by preserving a balanced microenvironment. Nevertheless, the definition of a "normal" vaginal microbiome remains controversial, as its composition varies depending on factors such as ethnicity and geographical origin. In most cases, members of the genus <i>Lactobacillus</i> predominate in healthy vaginal microbiomes, protecting against potential pathogens through specific mechanisms such as the secretion of lactic acid and bacteriocins, among others. A reduction in <i>Lactobacillus</i> abundance, accompanied by an increase in anaerobic organisms, predisposes the host to the development of various pathologies. Among these pathologies is infection with human papillomavirus (HPV) and the subsequent development of cervical cancer. A progressive decline in <i>Lactobacillus</i> has been observed as the lesion advances in different populations worldwide. In the case of the Mexican population, several <i>Lactobacillus</i> have been reported in healthy microbiomes: <i>L. gasseri</i>, <i>L. fermentum</i>, <i>L. rhamnosus</i>, <i>L. jensenii</i>, <i>L. crispatus</i>, <i>L. delbrueckii</i>, <i>L. acidophilus</i>, and <i>L. brevis.</i> In contrast, genera reported in dysbiosis include <i>Sneathia</i>, while <i>Brevibacterium aureum</i> and <i>Brachybacterium conglomeratum</i> have been associated with HPV16 infection and/or SIL. The mere presence of some bacteria is not sufficient to modulate the cellular activity of host cells; therefore, the expression, production and activity of different proteins could be affected by the vaginal microbiome. The impact of the microbiome on host cell function is the result of different metabolites produced by the bacteria, which suppress or activate different signaling and metabolic pathways. The molecular interactions between the host and microbiome, as well as their role in cervical carcinogenesis, are still unknown. In this review, we focus on the vaginal microbiome, HPV, and the impact that the interaction of the microbiome with HPV has in cervical cancer development.