solco continued to develop the formulation, during the course of which the new species lactobacillus vaginalis was identified in 1989. in the same year, the hamburg-based pharmaceutical company strathmann gmbh & co. kg. overtook production of the vaccines solcourovac (now named strovac) and solcotrichovac (now named gynatren). 2012-today in 2012 gynevac was withdrawn from the market, not due to any unexpected adverse effects, but rather due to vakcina kft. failing to obtain regulatory compliance upon the eu-accession of hungary. today gynatren is the only lactobacillus vaccine marketed for the treatment of non-specific bacterial vaginitis and trichomoniasis, and it is mostly only prescribed by a select few gynaecologists in the dach countries and hungary. in germany the vaccine may be covered by health insurance upon individual deliberation of the attending gynaecologist. research research interest in lactobacillus vaccines peaked in the 1980s. the technical and theoretical advances in the fields of microbiology, immunology and vaccinology of the past few decades could help shed new light on the still not fully clarified mode of action of these clinically promising vaccines. more research is warranted to elucidate the distinct properties of "aberrant" strains of lactobacilli, the exact mechanism by which they contribute to or accompany pathologies, the determinants of colonization in different groups of individuals. a further point of interest is the specificity of the immune stimulation – whether vaccination induces cross-reacting antibodies with any other microorganism. a comparative study on lactobacillus heterovaccines like gynatren and gynaecological autovaccines such as gynvaccine has yet to be performed. characteristics it has not been clarified by what mechanism the lactobacilli used in the vaccines ("aberrant" lactobacilli) fail to confer protection against vaginal pathogens. at the time of invention, available knowledge of the various health-promoting mechanisms of lactobacilli was very limited. for example, eschenbach's seminal work on h2o2-producing lactobacilli has not been published until 1989; at this point scientific efforts to clarify the vaccine's mechanism of action have already subsided. the nutrient medium, carbohydrate fermentation profile, and microscopic appearance of the strains used in solcotrichovac have been described. growth on an iron-enriched medium of 0.12 mᴍ concentration of feso4·7h2o is rather unusual for a lactobacillus species, and resembles the nutrient needs of l. iners, a vaginal lactobacillus associated with bacterial vaginosis and preterm birth, known for its ambiguous morphology, including coccobacillar cells (not used in the vaccine). påhlson and larsson hypothesized, that the defining characteristic of the lactobacilli used in solcotrichovac is a missing h2o2-production, which has not been confirmed. moreover, the correlation they found between bacterial cell morphology and health benefits, pointed towards an association between long uniform lactobacilli and decreased protection against vaginal infections, whereas polymorphic/shortened lactobacilli were described as innocuous inhabitants of the vaginal econiche. it seems, that the authors equated the strains used in solcotrichovac to those responsible for cytolytic vaginosis, which is generally considered a different condition, characterized by a lactobacillus overgrowth, rather than the depletion seen in patients colonized by the strains used in the vaccine. various other properties that could potentially play a role in the (lack of) protective effect, like the ratio of l-lactic acid to d-lactic acid production (correlated to mmp-8 concentrations of the vaginal fluid), adhesion competition, self- and co-aggregation ability, production of bacteriocins, organic acids or biosurfactants, immunomodulatory properties, or toxin production such as seen in l. iners remain obscure for the time. risk factors of colonization the inventor of lactobacillus vaccines, újhelyi described the strains used in gynevac as pathobionts to trichomonas vaginalis. he considered colonization with "aberrant", unprotective strains of lactobacilli, and their persistence even after protozoan infection has been cleared, a chronic post-infectious complication, and introduced the term "lactobacillus syndrome" for the condition (not to be confused with the distinct pathologies of cytolytic vaginosis and vaginal lactobacillosis). scattered reports suggest that some minority of lactobacillus strains found in humans indeed enhance rather than inhibit parasite adhesion to the vaginal epithelium. in vitro preincubation of vaginal epithelial cells (vecs) with physiological concentrations (1×107–1×108 cfu/ml) of lactobacillus cbi3 (a human isolate of l. plantarum or l. pentosus) increased the number of t. vaginalis cells able to adhere to the vec monolayer up to eightfold. mcgrory and garber reported a significant prolongation of t. vaginalis infection in estrogenized balb/c mice intravaginally preinoculated with 1×109 cells of l. acidophilus atcc 4356 (originating from the human pharynx) in comparison to animals that had not been pretreated. although initial infectivity in the two groups was comparable, at day 24 post-infection 69% of l. acidophilus-inoculated mice still showed positive t. vaginalis cultures, compared with only 11% of mice not harboring lactobacilli. other hypothesized risk factors of colonization by lactobacilli of low protective value in general include prior antimicrobial treatment and congenital factors. association with t. vaginalis soszka and kuczyńska described the appearance of morphological variations of lactobacilli, when grown in the presence of a high concentration of trichomonas vaginalis. the authors interpreted the observed atypical (coccoid) cell morphology as an involution (senescent, dying) form. goisis et al. have shown, that shortened and coccoidal lactobacilli are not only present in the primary secretion samples of trichomoniasis patients, but also in the cultures started from these samples, free from competitive microorganisms and under optimal culture conditions, suggesting that the coccoid bacteria may represent a distinct viable phenotype. contrastingly, the isolates from vaccinated patients tended to assume bacilliform also in culture. the general consensus remains, that at least some of the morphology variants seen under trichomoniasis versus health are to be interpreted as representations of "true commensal" versus more pathogenic strains (genotypes), although a possible relationship between morphotype and distinct environment-driven proteome profiles has not been excluded. immunological cross-reaction with t. vaginalis the antigenic material responsible for the effect of lactobacillus vaccines is most likely surface antigens of the aberrant lactobacilli. the anti-trichomonal effect of solcotrichovac has led multiple researchers to investigate the possibility of shared surface antigens between the specific strains used in the vaccine and t. vaginalis. the theory of antigenic cross-reactivity was put to the test by stojković. indirect immunofluorescence was performed on trichomonads treated with rabbit antisera against aberrant lactobacilli and against t. vaginalis. specific immunofluorescence was observed on those protozoa which had been treated with anti-lactobacillus serum and anti-trichomonas serum, but not on those treated with serum from non-vaccinated animals. bonilla-musoles performed an electron microscopic study on trichomonads treated with serum from women who were previously vaccinated with solcotrichovac. after three days the trichomonads exposed to antibody-containing serum showed marked signs of destruction, similar to those observed under the influence of metronidazole. the electron micrographs revealed cytoplasmic swelling, dilation of the reticuloendothelial lamellae and formation of vacuoles as well as evaginations and invaginations of cellular membranes. alderete, gombošová and others however described contrary findings, and attributed any anti-trichomonal activity of lactobacillus vaccines to non-specific immune mechanisms. the question of immunological relationship between aberrant lactobacilli and t. vaginalis has not been answered conclusively. phylogenetic relationships to t. vaginalis an intriguing hypothesis was advanced by alain de weck that suggests horizontal gene transfer between specific aberrant strains of lactobacilli used in solcotrichovac and t. vaginalis, which leads to their (possible) cross-immunogenicity. phylogenetic relationships between t. vaginalis and aberrant lactobacilli have not been studied. nevertheless, multiple examples of gene transfer between the parasite and bacteria have been documented. audrey de koning argues that lateral transfer of the n-acetylneuraminate lyase gene from pasteurellaceae to t. vaginalis may have been a key factor in the adaptation of trichomonas to parasitism. in an analogous manner, buret et al. suggest gene exchanges between enteropathogens and normal microbiota during acute enteric infection as one of the possible causative factors behind post-infectious intestinal inflammatory disorders. alternative theory of the mechanism of action goisis and his colleagues proposed an alternative hypothesis on the mechanism of action of solcotrichovac, suggesting that anti-lactobacillus antibodies may stimulate proliferation of lactobacilli rather than their (strain-specific) damage or inhibition. among the circumstances they cited to support this theory, is their opinion that antibodies specific to one strain of lactobacillus would most likely cross-react with several antigens present on various other strains (yet, both the concentration of anti-lactobacillus siga antibodies and lactobacillus counts have been demonstrated to increase in vaccinated women). further they referred to the inconspicuous metabolic profile and the lack of a verified pathomechanism of the strains used in solcotrichovac, suggesting that they may represent mere morphotypes rather than pathogenic/unprotective biotypes. the proposed theory relies on analogies with other known examples of non-classical, stimulatory/homeostatic antibody-antigen interactions. notably, the majority of intestinal bacterial cells in healthy individuals is bound by siga. the siga-coating of commensal enteric bacteria is believed to promote intestinal microbial homeostasis by a number of mechanisms. secreted iga anchors commensal bacteria to the mucus and facilitates biofilm formation, thereby limiting their translocation from the lumen into mucosal tissues. this minimizes activation of the innate immune system, a process termed "immune exclusion". furthermore, the selective uptake of siga-microbe immune complexes by dendritic cells (dcs) in lymphoid follicles has been shown to induce semimaturation of the dcs. the resulting, so-called tolerogenic dcs downregulate the expression of t cell costimulatory molecules and proinflammatory cytokines. the altered immune signaling favours local processing of antigens and a rapid induction of low-affinitiy, broad-specificity iga, leaving the systemic immune compartment ignorant about these organisms. in contrast, direct translocation of non-siga-coated microbes or microbial products across the epithelium preferentially results in proinflammatory signalling and a systemic response against the invading agent, involving affinity-matured serum antibodies of the classes iga, ige and igg. lastly, binding by siga can downregulate the expression of virulence factors e.g. involved in adhesion or nutrient acquisition by commensal bacteria. if the homeostasis breaks down, innate immune responses directed against commensal enteric bacteria lead to a shift in the species composition (dysbiosis). invasive species are better equipped to resist or take advantage of host inflammatory mechanisms and in the perturbed niche successfully compete with the resident microbiota. hypersensitivity responses to commensal enteric microbiota and a perturbation of microbial ecology is observed in many patients with chronic enterocolitis. this alternative theory coincides with the observation that women without a history of urinary tract or vaginal infections harbor higher antibody levels against vaginal lactobacilli than women with a history of these infections. alvarez-olmos and her coworkers reported an approximately fourfold elevation of total igg and a threefold elevation of total iga concentration in the cervicovaginal secretions of adolescent women colonized with h2o2-producing lactobacilli (associated with vaginal health) in comparison to those colonized with non-h2o2-producing lactobacilli. goisis et al. described lactobacillus vaccination as a means to systemically boost a diminished pool of lactobacillus-specific vaginal antibodies, likely increasing the potential for immune exclusion and tolerogenic responses to the microorganisms. they added to this a further hypothetical notion: loss of lactobacillus-specific siga may be characteristic to patients co-colonized by bacteria capable to gradually desialylate and finally proteolytically degrade siga, a known impairment of the vaginal defense system, established in the context of gardnerella vaginalis-specific antibodies. this contrasts with other proposed mechanism of siga deficiency, such as the loss of immunomodulatory strains or host immunodeficiency. although goisis et al. announced ongoing experiments and preliminary results to prove this theory, as well as the possible cross-reactivity of "normal", ecologically beneficial lactobacilli with antibodies directed against the strains used in solcotrichovac, a conclusive report has not been publicized to date.