The LiaSR Two-Component System Regulates Resistance to Chlorhexidine in Streptococcus mutans.

Chlorhexidine (CHX) is widely considered to be the gold standard for preventing dental caries. However, it is possible to induce resistance to CHX. The LiaSR two-component system has been identified that contributed to CHX resistance in Streptococcus mutans, which is one of the major pathogens in dental caries. However, the underlying mechanisms remain unclear. In this study, an MIC assay and a viability assessment demonstrated that after deleting the liaS and liaR genes, the sensitivity of mutants could increase. The Nile Red efflux assay exhibited that the efflux rates of mutants were significantly decreased. The RT-qPCR results indicated that the LiaSR two-component system-mediating influence on the expression of lmrB in S. mutans contributed to the efflux rate. The hydrophobicity assay and membrane potential assay showed that the mutants had higher levels of hydrophobicity and depolarization, suggesting that their membranes were more easily disturbed. The TEM graphs revealed that the border of the cell membrane was unclear in mutants compared with the wild-type strain, indicating that the cell envelope's stress response may have been inhibited. While the surface charge of mutants showed no significant difference in the wild-type strain according to the result of cytochrome c-based charged determination. This study provides valuable novel insights into the mechanisms of the LiaSR two-component system in the CHX resistance of S. mutans.

Current and prospective therapeutic strategies: tackling Candida albicans and Streptococcus mutans cross-kingdom biofilm.

Candida albicans (C. albicans) is the most frequent strain associated with cross-kingdom infections in the oral cavity. Clinical evidence shows the co-existence of Streptococcus mutans (S. mutans) and C. albicans in the carious lesions especially in children with early childhood caries (ECC) and demonstrates the close interaction between them. During the interaction, both S. mutans and C. albicans have evolved a complex network of regulatory mechanisms to boost cariogenic virulence and modulate tolerance upon stress changes in the external environment. The intricate relationship and unpredictable consequences pose great therapeutic challenges in clinics, which indicate the demand for de novo emergence of potential antimicrobial therapy with multi-targets or combinatorial therapies. In this article, we present an overview of the clinical significance, and cooperative network of the cross-kingdom interaction between S. mutans and C. albicans. Furthermore, we also summarize the current strategies for targeting cross-kingdom biofilm.

Dlt operon regulates physiological function and cariogenic virulence in Streptococcus mutans.

Streptococcus mutans is one of the major cariogenic pathogens in the oral cavity. The dlt operon is responsible for the process of D-alanylation of lipoteichoic acid and is related to the virulence of S. mutans. The dlt operon contributes to the adhesion, biofilm formation, stress response, interspecies competitiveness and autolysis of S. mutans. In addition, we have summarized the possible regulatory networks of the dlt operon. This review highlights the significant role of the dlt operon in S. mutans and provides new ideas for ecological caries prevention.

What is this summary about? Dental caries is a common oral disease that destroys teeth. Streptococcus mutans is the major pathogen of dental caries and its cariogenic virulence factors depend on the ability of biofilm formation, acid production and tolerance, stress response, and interspecific competitiveness. The dlt operon is responsible for the process of D-alanylation of lipoteichoic acid and is related to the virulence of Gram-positive bacteria. To understand the role of the dlt operon in S. mutans, this review summarized this based on previous studies. What were the results? The dlt operon can regulate the D-alanylation of lipoteichoic acid to affect the cell surface charge of S. mutans. The change in characteristics of the cell wall will affect the physiological functions of S. mutans, such as adhesion, biofilm formation, stress response, autolysis and interspecies competitiveness. However, the regulatory mechanism of the dlt operon is still unclear and needs further study. What do the results of the study mean? This review highlights the significant role of the dlt operon in S. mutans, which will increase the understanding of the cariogenic mechanism of S. mutans and provide new ideas for ecological caries prevention, such as the development of antibacterial agents targeting the dlt operon.

Antimicrobial Photodynamic Effect of Cross-Kingdom Microorganisms with Toluidine Blue O and Potassium Iodide.

Streptococcus mutans (S. mutans) and Candida albicans (C. albicans) are prominent microbes associated with rapid and aggressive caries. In the present study, we investigated the antimicrobial efficacy, cytotoxicity, and mechanism of toluidine blue O (TBO)-mediated antimicrobial photodynamic therapy (aPDT) and potassium iodide (KI). The dependence of KI concentration, TBO concentration and light dose on the antimicrobial effect of aPDT plus KI was determined. The cytotoxicity of TBO-mediated aPDT plus KI was analyzed by cell counting kit-8 (CCK-8) assay. A singlet oxygen (1O2) probe test, time-resolved 1O2 detection, and a 1O2 quencher experiment were performed to evaluate the role of 1O2 during aPDT plus KI. The generation of iodine and hydrogen peroxide (H2O2) were analyzed by an iodine starch test and Amplex red assay. The anti-biofilm effect of TBO-mediated aPDT plus KI was also evaluated by counting forming unit (CFU) assay. KI could potentiate TBO-mediated aPDT against S. mutans and C. albicans in planktonic and biofilm states, which was safe for human dental pulp cells. 1O2 measurement showed that KI could quench 1O2 signals, implicating that 1O2 may act as a principal mediator to oxidize excess iodide ions to form iodine and H2O2. KI could highly potentiate TBO-mediated aPDT in eradicating S. mutans and C. albicans due to the synergistic effect of molecular iodine and H2O2.

D-alanylation of lipoteichoic acid contributes to biofilm formation and acidogenesis capacity of Streptococcusmutans.

BACKGROUND: D-alanylation of Lipoteichoic acid (LTA) is considered to be essential for virulence factors expression in Gram-positive microorganism. The effects of the D-alanylation of LTA on biofilm formation and acidogenesis of Streptococcus mutans (S. mutans) are still not clearly understood. AIM: This study was designed to investigate the impact of D-alanylation of LTA on biofilm formation and acidogenesis of S. mutans and explore the related mechanisms. METHODS AND MATERIAL: We compared the biofilm formation process by fluorescence microscope observation of LTA D-alanylation blocking strain with that of the wildtype strain. Auto-aggregation, cell surface charge, and polysaccharide production assays were performed to investigate the related mechanisms. pH drop assay and glycolysis pH drop-down analysis were carried out to evaluate the acidogenesis capacity of S. mutans after LTA D-alanylation blocking. To identify the biofilm formation and adhesive-related genes expressions of S. mutans mutant, qRT-PCR was performed. RESULTS: After blocking off the D-alanylation of LTA, S. mutans could not form the three-dimensional structural biofilm, in which cells were scattered on the substratum as small clusters. The auto-aggregation was prompted due to the mutant strain cell morphology change (*p < 0.05). Furthermore, more negative charges were found on the mutant strain cells surfaces and fewer water-insoluble glucans were produced in mutant biofilm (*p < 0.05). The adhesion capacity of the S. mutans biofilm was impaired after LTA D-alanylation blocking (*p < 0.05). Biofilm formation and adhesive-related genes expressions decreased (*p < 0.05), especially at the early stages of biofilm formation. S. mutans mutant strains exhibited suppressed acidogenesis because its glycolytic activity was impaired. CONCLUSION: The results of this study suggest that blocking of LTA D-alanylation disrupts normal biofilm formation in S. mutans predominantly if not entirely by altering intercellular auto-aggregation, cell adhesion, and extracellular matrix formation. Moreover, our study results suggest that the LTA D-alanylation plays an important role in S. mutans acidogenesis by altering glycolytic activity. These findings add to the knowledge about mechanisms underlying biofilm formation and acid tolerance in S. mutans.

[Effect of Lipoteichoic Acid Synthesis-Related Gene dltD on Acid Tolerance of Highly Cariogenic Strains of Streptococcus mutans].

Objective: To study the role and possible mechanism of dltD in the acid tolerance of Streptococcus mutans 593 (SM593), and to provide a theoretical basis for the ecological prevention and control of dental caries by constructing the dltD gene deletion strain of SM593 (SM593-ΔdltD). Methods: 1) SM593-Δ dltD was constructed by homologous recombination. 2) The growth curve of SM593 dltD and SM593-Δ dltD under different pH culture conditions was drawn by the automatic growth curve analyzer to compare their acid tolerance. Colony forming unit (CFU) at different time points was used to calculate the survival rate and to compare the acid tolerance response (ATR) of SM593 and SM593-Δ dltD. 3) Under different pH conditions, glycolysis experiments, proton permeability test and H +-ATPase activity test were conducted to make preliminary exploration into the mechanisms of how dltD gene deletion may affect acid tolerance. Results: 1) PCR and sequencing results showed that the SM593-Δ dltD was constructed successfully. 2) With decreasing pH value of the culture medium, the growth of SM593-Δ dltD slowed down. When the pH value of the culture medium was 5.0, SM593-Δ dltD was not allowed to grow, and its acid tolerance was lower than that of SM593. Compared with SM593, the ATR capability of SM593-Δ dltD was decreased. 3) SM593 dltD and SM593-Δ dltD did not show obvious difference in their glycolysis ability under different pH conditions. Compared with SM593 dltD, the proton permeability of SM593-Δ dltD under different pH conditions was increased significantly (P<0.05), and H +-ATPase activity decreased significantly (P<0.05). Conclusion: Compared with SM593 dltD, SM593-Δ dltD showed obvious decrease in acid tolerance, which may be caused by the significant increase in proton permeability and significant decrease in the H +-ATPase activity induced by the deletion of the dltD gene, hence reducing its ability to maintain intracellular pH homeostasis.

The dlt operon contributes to the resistance to chlorhexidine in Streptococcus mutans.

Chlorhexidine (CHX) is considered to be the gold standard for dental caries prevention and is widely applied in dental practice. However, the long-term application of CHX may result in CHX-resistance in oral pathogens. The aim of this study was to investigate whether long-term use of CHX causes resistance in Streptococcus mutans and to explore the possible associated mechanisms. Four different S. mutans strains were chosen for this study to exclude the specificity of strains. The four strains displayed an increase in minimum inhibitory concentration (MIC) after exposure to CHX for 10 passages. The features and cariogenicity of S. mutans CHX-resistant strains (SM-Cs) that were exposed to CHX for 10 passages with increased MIC did not differ significantly to the parental strains. The SM-Cs were more hydrophobic than the parental strains. The dltC and dltD genes were upregulated in SM-Cs. Relative expression of the BceA, BceR, and SMU.862 genes in SM-Cs was similar to or lower than that of the parental strains. The MIC value was significantly lower in dltC knockout mutants. These findings confirmed that continuous exposure to CHX could induce CHX-resistance in S. mutans. The increased cell surface hydrophobicity and upregulated expression of dlt operon were possible underlying mechanisms of CHX-resistance in S. mutans.

Hydrogen peroxide potentiates antimicrobial photodynamic therapy in eliminating Candida albicans and Streptococcus mutans dual-species biofilm from denture base.

BACKGROUND: Candida albicans (C.albicans) is the primary pathogen of denture biofilm. Moreover, it could establish a cross-kingdom relationship with bacteria to enhance its virulence and resistance to antifungal drugs. This study aimed to investigate the efficacy of antimicrobial photodynamic therapy (aPDT) in combination with hydrogen peroxide (H2O2) against C.albicans and Streptococcus mutans (S.mutans) dual-species biofilm formed on polymethyl methacrylate (PMMA) disk, and explore its involved mechanisms. METHODS: C.albicans and S.mutans were grown on PMMA disk for 48 h to form biofilm and received different treatments. The treatments included:1) phosphate-buffered saline (PBS) group,2) 100 mM H2O2 group,3) aPDT group,4) aPDT+ H2O2 and 5) H2O2+aPDT group. Colony forming units (CFU), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and scanning electron microscope (SEM) were used to evaluate the antimicrobial effects. Extracellular polysaccharide substance (EPS) production and observation, cell permeability of biofilm, and uptake of toluidine blue O (TBO) by biofilm were assessed to investigate the involved mechanism. RESULTS: There was no significant difference between PBS group and H2O2 group in viable microorganisms and metabolic activity of biofilm. The treatment protocols containing aPDT group reduced microorganism numbers and metabolic activity when compared to PBS group or H2O2 group (P<0.05). H2O2+aPDT treatment showed the highest antimicrobial efficacy in comparison with other treatments (P<0.05). Pretreatment with H2O2 could decrease EPS production and enhance cell permeability, leading to increased TBO uptake in biofilm. CONCLUSION: Pretreatment with H2O2 improved aPDT efficiency in eliminating dual-species biofilm from PMMA disk by reducing EPS amount, enhancing cell permeability, and increasing TBO uptake.

Role of D-alanylation of Streptococcus mutans lipoteichoic acid in interspecies competitiveness.

BACKGROUND: The D-alanylation of lipoteichoic acid (LTA) is essential for the physiological metabolism of Streptococcus mutans (S. mutans). This study was designed to investigate the influence of D-alanylation of LTA on interspecies competitiveness of S. mutans. METHODS: The process of D-alanylation was blocked by the inactivation of dltC. Agar competition assays, conditioned medium assays, and qRT-PCR were used to evaluate the production of antimicrobial compounds in S. mutans mutant. Dual-species biofilm was formed to investigate the competitiveness of S. mutans mutant cocultured with S. sanguinis or S. gordonii. RESULTS: S. mutans mutant could not produce antimicrobial compounds efficiently when cocultured with commensal bacteria (*p < 0.05). The mutant showed compromised competitiveness in dual-species biofilms. The ratio of the mutant in dual-species biofilms decreased, and the terminal pH of the culture medium in mutant groups (mutant+S. sanguinis/S. gordonii) was higher than that in wild-type groups (*p < 0.05). Scanning electron microscope (SEM) showed weaker demineralization of enamel treated with dual-species biofilms consisting of mutant and commensal bacteria. CONCLUSION: D-Alanylation is involved in interspecies competitiveness of S. mutans within oral biofilm by regulating mutacins and lactic acid production, which may modulate the profiles of dental biofilms. Results provide new insights into dental caries prevention and treatment.

Verrucous Carcinoma of the Vulva: A Case Report and Literature Review.

BACKGROUND Verrucous carcinoma (VC) of the vulva is a variation of squamous carcinoma (SCC). Etiology and treatment of VC are still unclear. CASE REPORT A 50-year-old female visited our clinic with a giant vulvar tumor (8 cm of diameter maximum). Biopsy revealed a suspicious well differentiation squamous cancer. PET/CT (positron emission tomography/computed tomography) scan found suspicious lymph node in bilateral iliac vessel region and bilateral inguinal region. She underwent radical vulvectomy and bilateral inguinal lymph node dissection, and bilateral pelvic lymph node dissection. Pathology turns out to be VC and no lymph nodes involvement. Due to the large defection, vulvar reconstruction was performed 5 weeks later using skin grafts and pudendal thigh flap. This patient was disease free after 12 months follow-up. CONCLUSIONS In patients with VC, a satisfactory biopsy is important and systemic inguinal lymphadenectomy might be omitted. For patients with large defection, flap-based reconstruction is recommended.

Downregulation of ERBB3 decreases the proliferation, migration and invasion of cervical cancer cells though the interaction with MTK-1.

Cervical cancer is a common malignancy in females. Diagnosis and treatment of cervical cancer remains a challenge due to difficulties in the presence of tumor metastasis. Increased expression level of Erb-b2 receptor tyrosine kinase 3 (ERBB3) has previously been demonstrated to be associated with the occurrence of cervical cancer; however, the functionality of ERBB3 in the development of cervical cancer remains incompletely understood. In the present study, the expression level of ERBB3 in patients with cervical squamous cell carcinoma and cervical adenocarcinoma was detected by reverse transcription quantitative polymerase chain reaction. The effects of ERBB3 small interfering RNA silencing on cell proliferation, migration and invasion were explored, and the interaction between ERBB3 and mitogen-activated protein kinase kinase kinase 4 (MTK-1) was also investigated. It was identified that the downregulation of ERBB3 significantly decreased the proliferative, migratory and invasive abilities of cervical cancer cells. In addition, the expression level of MTK-1 was also significantly decreased following MTK-1 siRNA silencing. Therefore, we hypothesize that the downregulation of ERBB3 may decrease the proliferative, migratory and invasive abilities of cervical cancer cells by inhibiting the expression of MTK-1.

Prevalence of High-Risk Human Papillomavirus (HR-HPV) Genotypes and Multiple Infections in Cervical Abnormalities from Northern Xinjiang, China.

Multiple human papillomavirus (HPV) genotypes often coexist within the cervical epithelia and are frequently detected together in various grades of the cervical neoplasia. To date, only a few reports exist on multiple HPV infections of HPV in Xinjiang Uygur Autonomous Region (XUAR). In the present study, we investigated the prevalence of High-Risk HPV (HR-HPV) genotypes and multiple infections. Cervical cytology samples were collected from 428 women who presented cervical abnormalities. Genotyping of HPV was performed by polymerase chain reaction-sequencing based typing (PCR-SBT) using consensus primers and specific primers. Of them, 166 samples were positive for HPV according to PCR results using the consensus primers. These samples contained cervical abnormalities enriched with inflammation (n = 107), cervical intraepithelial neoplasia (CIN) I (n = 19), CINII-III (n = 9) and cervical cancer (n = 31). Of the 166 HPV positive samples as determined by PCR analysis, 151 were further typed by PCR-SBT using 19 pairs of genotype-specific primers. Using this method, 17 different HR-HPV genotypes were identified. The most frequently observed HPV genotypes were HPV16 (44.0%, 73/166), 53 (28.9%, 48/166), 52 (25.3%, 42/166), 58 (22.3%, 37/166) and 35 (17.5%, 29/166). The proportions of single and multiple infections in the HPV-positive specimens were 34.9% and 65.1%, respectively. Multiple HPV types were most prevalent in the inflammatory state (63.0%), followed by cervical cancer (24.1%), CINI (11.1%), and CINII-III (1.9%). The results of our data analyses suggested that i) multiple HPV infection is not necessarily correlated with the severity of cervical abnormalities; and ii) among the multiple HPV infections, double infections combined with HPV16 is the most common. In addition, L1 full-length sequences of the top five high-risk HPV genotypes were amplified and sequenced. According to the L1 sequence of the epidemic genotypes that were amplified, we found that these genotypes contained the sequence point mutation, and that some of these genotypes further showed amino acid modifications. These results provide a basis for the construction of a polyvalent vaccine that is suitable for use in the XUAR, even in economically challenged communities located in China.

A broad-range survey of ticks from livestock in Northern Xinjiang: changes in tick distribution and the isolation of Borrelia burgdorferi sensu stricto.

BACKGROUND: Borreliosis is highly prevalent in Xinjiang Uygur Autonomous Region, China. However, little is known about the presence of Borrelia pathogens in tick species in this region, in addition Borrelia pathogens have not been isolated from domestic animals. METHODS: We collected adult ticks from domestic animals at 19 sampling sites in 14 counties in northern Xinjiang from 2012 to 2014. Ticks were identified to species by morphology and were molecularly analysed by sequences of mitochondrial 16S rDNA gene; 4-8 ticks of each species at every sampling site were sequenced. 112 live adult ticks were selected for each species in every county, and were used to culture Borrelia pathogens; the genotypes were then determined by sequences of the 5S-23S rRNA intergenic spacer and the outer surface protein A (ospA) gene. RESULTS: A total of 5257 adult ticks, belonging to four genera and seven species, were collected. Compared with three decades ago, the abundance of the five common tick species during the peak ixodid tick season has changed. Certain tick species, such as Rhipicephalus turanicus (Rh. turanicus), was found at Jimusaer, Yining, Fukang, and Chabuchaer Counties for the first time. Additionally, the sequence analyses showed that the Hyalomma asiaticum (Hy. asiaticum), Haemaphysalis punctata (Ha. punctata), and Dermacentor marginatus (D. marginatus) that were collected from different sampling sites (≥3 sites) shared identical 16S rDNA sequences respectively. For the tick species that were collected from the same county, such as Hy. asiaticum from Shihezi County and Rh. turanicus from Yining County, their 16S rDNA sequences showed genetic diversity. In addition, sixteen Borrelia isolates were found in Hy. asiaticum, Ha. punctata, D. marginatus and Rh. turanicus, which infested cattle, sheep, horse and camel in Yining, Chabuchaer, Shihezi and Shawan Counties. All of the isolates were genetically identified as B. Burgdorferi sensu stricto. CONCLUSIONS: Warmer and wetter climate may have contributed to the altered distribution and abundance of the five most common ticks in northern Xinjiang. The genetic analyses showed that certain tick species, such as Hy. asiaticum or Rh. turanicus, exhibit genetic commonness or diversity. Additionally, this study is the first to isolate B. burgdorferi sensu stricto in Hy. asiaticum asiaticum, H. punctata, D. nuttalli and D. marginatus ticks from domestic animals. These ticks may transmit borreliosis among livestock.

[Isolation of Borrelia burgdorferi in ixodes from four counties, in North Xinjiang].

OBJECTIVE: To identify ticks and determine the Borrelia (B.) burgdorferi genotype from four counties of northern Xinjiang. METHODS: Sheep ticks were collected from 6 surveillance sites in four counties including Shihezi, Shawan,Yining and Chabuchaer. All ticks were initially screened out based on morphological methods and 16S rRNA sequence analysis. B. burgdorferi was detected and cultivated with BSK-H medium. Combined with nested PCR, silver nitrate staining was employed to detect B. burgdorferi. Genotype of isolated B. burgdorferi was determined by Sequencing and phylogenic analysis based on 11 conference sequences. RESULTS: Hyalomma asiaticum asiaticum, Haemaphysalis punctata, Dermacentor marginatus and Rhipicephalus turanicus were identified from more than 900 ticks. Out of 24 tubes from 102 representative tick specimens, 16 tube were positive for B. burgdorfer. Sequencing of 5S-23S rRNA intergenic spacer showed 98.6%-99.5% identities to B. burgdorferi Sensu Stricto(B31). Results from the analysis of OspC genotype showed consistent with that of 5S-23S rRNA intergenic spacer. CONCLUSIONS: 16 strains of B. burgdorferi Sensu Stricto were isolated in four counties, from northern Xinjiang. Additionally, B. burgdorferi Sensu Stricto was isolated from Rhipicephalus turanicus first time in China.

Changes of mitochondrial ultrastructures and function in central nervous tissue of hens treated with tri-ortho-cresyl phosphate (TOCP).

Tri-ortho-cresyl phosphate (TOCP), an organophosphorus ester, is capable of producing organophosphorus ester-induced delayed neurotoxicity (OPIDN) in humans and sensitive animals. The mechanism of OPIDN has not been fully understood. The present study has been designed to evaluate the role of mitochondrial dysfunctions in the development of OPIDN. Adult hens were treated with 750 mg/kg·bw TOCP by gavage and control hens were given an equivalent volume of corn oil. On day 1, 5, 15, 21 post-dosing, respectively, hens were anesthetized by intraperitoneal injection of sodium pentobarbital and perfused with 4% paraformaldehyde. The cerebral cortex cinerea and the ventral horn of lumbar spinal cord were dissected for electron microscopy. Another batch of hens were randomly divided into three experimental groups and control group. Hens in experimental groups were, respectively, given 185, 375, 750 mg/kg·bw TOCP orally and control group received solvent. After 1, 5, 15, 21 days of administration, they were sacrificed and the cerebrum and spinal cord dissected for the determination of the mitochondrial permeability transition (MPT), membrane potential (Δψ(m)) and the activity of succinate dehydrogenase. Structural changes of mitochondria were observed in hens' nervous tissues, including vacuolation and fission, which increased with time post-dosing. MPT was increased in both the cerebrum and spinal cord, with the most noticeable increase in the spinal cord. Δψ(m) was decreased in both the cerebrum and spinal cord, although there was no significant difference in the three treated groups and control group. The activity of mitochondrial succinate dehydrogenase assayed by methyl thiazolyl tetrazolium (MTT) reduction also confirmed mitochondrial dysfunctions following development of OPIDN. The results suggested mitochondrial dysfunction might partly account for the development of OPIDN induced by TOCP.

[Cellular ultrastructural changes of bone marrow of patients with hemorrhagic fever with renal syndrome].

BACKGROUND: To observe cytopathogenic effect of Hantaan virus (HV) on cultured human bone marrow cells. METHODS: Light and transmission electron microscopy and direct immunofluorescent technique were applied to study cellular structure especially ultrastructural changes of bone marrow cells from patients with Hantaan virus infection. Bone marrow cells of one healthy volunteer were also studied as control. RESULTS: The antigen of HV was found in bone marrow cells of 20 of 27 HFRS patients by the aid of direct immunofluorescent technique. It was found that the granulocytes had the highest percentage of HV antigen positive cells (76%), followed by monocytes (65%), lymphocytes (40%), megakaryocytes (20%) and the lowest was found in erythrocytes (3.7%). The injury of cell membrane after infection with HV was significantly more severe than that in the control group under the light and electron microscopy. CONCLUSION: This study demonstrated that HV could attack human bone marrow cells and cause cytopathogenic effect on them.