Dynamics of Human Papillomavirus Infection between Biopsy and Excision of Cervical Intraepithelial Neoplasia: Results from the ZYC101a Protocol

Aerobic vaginitis is associated with carbonic anhydrase IX in cervical intraepithelial neoplasia

The aim of this study was to analyze the association between vaginal microbiota, carbonic anhydrase IX (CAIX) and histological findings of cervical intraepithelial neoplasia (CIN). The study included 132 females, among them 66 were diagnosed with high-grade intraepithelial lesion (CIN2, CIN3, and cancer), 14 with low-grade disease, and 52 assigned to the control group. An interview focused on the behavior risk factors, together with vaginal fluid pH measurement, wet mount microscopy, detection of Chlamydia trachomatis, and Trichomonas vaginalis were performed. After colposcopy, high-grade abnormalities were detected via direct biopsies and treated with conization procedure. Conuses were immuno-stained with CAIX antibody. The histological findings were CIN1 (n = 14), and CIN2+ (included CIN2 (n = 10), CIN3 (n = 49), and cancer (n = 7; squamous cell carcinomas)). Prevalence of bacterial vaginosis (BV) was similar between the groups. Moderate or severe aerobic vaginitis (msAV) was diagnosed more often among CIN2+ (53.0%) than CIN1 (21.4%). Moderate or strong immunostaining of CAIX (msCAIX) was not detected among CIN1 cases. Thus, msAV was prevalent in CAIX non-stained group (p = 0.049) among CIN2 patients. Co-location of msAV and msCAIX was found in CIN3. Regression model revealed that msAV associated with high-grade cervical intraepithelial neoplasia independently from smoking and the number of partners.

Proposed Terminology for Anal Squamous Lesions: Its Application and Interobserver Agreement Among Pathologists in Academic and Community Hospitals

OBJECTIVES

To analyze interobserver reproducibility and compare practice patterns between academic and community settings of Lower Anogenital Squamous Terminology (LAST).

METHODS

In total, 132 anal biopsy slides were revised as well as p16 immunostains.

RESULTS

LAST was used in 49% of cases (academic center, 68%; satellite hospitals [community practice setting], 32%). After pathology review and consensus interpretation, 23 (17%) case diagnoses were reclassified: eight (34.8%) cases (benign or low-grade squamous intraepithelial lesion [LSIL]) were upgraded to high-grade squamous intraepithelial lesion (HSIL) (p16 confirmed ordered during review); four (17.4%) cases originally classified as HSIL were downgraded to LSIL (p16 originally ordered in one case). There was no significant difference in discrepancies between original and consensus diagnosis in the community vs academic setting or by subspecialty (gynecological vs gastrointestinal). Overall interobserver agreement among reviewers was substantial (κ = 0.63) and improved with the use of p16 immunostain in challenging cases (κ = 0.71; P < .001).

CONCLUSIONS

This new terminology is not yet uniformly used by pathologists in anal/perianal biopsy specimens; this two-tier system has a good interobserver agreement and is further improved with p16 use in appropriate cases.

Interplay between the temporal dynamics of the vaginal microbiota and human papillomavirus detection

BACKGROUND

We sought to describe the temporal relationship between vaginal microbiota and human papillomavirus (HPV) detection.

METHODS

Thirty-two reproductive-age women self-collected midvaginal swabs twice weekly for 16 weeks (937 samples). Vaginal bacterial communities were characterized by pyrosequencing of barcoded 16S rRNA genes and clustered into 6 community state types (CSTs). Each swab was tested for 37 HPV types. The effects of CSTs on the rate of transition between HPV-negative and HPV-positive states were assessed using continuous-time Markov models.

RESULTS

Participants had an average of 29 samples, with HPV point prevalence between 58%-77%. CST was associated with changes in HPV status (P<.001). Lactobacillus gasseri-dominated CSTs had the fastest HPV remission rate, and a low Lactobacillus community with high proportions of the genera Atopobium (CST IV-B) had the slowest rate compared to L. crispatus-dominated CSTs (adjusted transition rate ratio [aTRR], 4.43, 95% confidence interval [CI], 1.11-17.7; aTRR, 0.33, 95% CI, .12-1.19, respectively). The rate ratio of incident HPV for low Lactobacillus CST IV-A was 1.86 (95% CI, .52-6.74).

CONCLUSIONS

Vaginal microbiota dominated by L. gasseri was associated with increased clearance of detectable HPV. Frequent longitudinal sampling is necessary for evaluation of the association between HPV detection and dynamic microbiota.

Impact of p16(INK4a) immunohistochemistry staining on interobserver agreement on the diagnosis of cervical intraepithelial neoplasia

OBJECTIVES

This study aimed to compare the interobserver Cohen κ on H&E staining and on H&E plus p16(INK4a) staining of all cervical biopsy specimens in a population-based screening program.

METHODS

All the colposcopy-guided biopsies generated by the routine screening of 23,258 women aged 25 to 64 years were stained with H&E and H&E plus p16. Biopsy specimens were reviewed by six external experts.

RESULTS

The four diagnoses were available in 441 cases. The interobserver κ values were 0.52 (95% confidence interval [CI], 0.45-0.58) and 0.48 (95% CI, 0.42-0.56) with H&E and H&E + p16, respectively, when using a five-group classification (normal, CIN 1, CIN 2, CIN 3, and cancer); adopting a two-group classification (≤CIN 1 and ≥CIN 2), the values were 0.75 (95% CI, 0.66-0.82) and 0.70 (95% CI, 0.61-0.79), respectively.

CONCLUSIONS

The use of p16 on all cervical biopsy specimens in a screening program showed virtually no effect on reproducibility of the histologic diagnosis.

Characterizing the temporal dynamics of human papillomavirus DNA detectability using short-interval sampling

BACKGROUND

Variable detection of human papillomavirus (HPV) DNA can result in misclassification of infection status, but the extent of misclassification has not been quantitatively evaluated.

METHODS

In 2005-2007, 33 women of ages 22 to 53 years self-collected vaginal swabs twice per week for 16 consecutive weeks. Each of the 955 swabs collected was tested for 37 HPV types/subtypes. Assuming that a woman's underlying infection status did not change over the short study period, biases in prevalence estimates obtained from single versus multiple swabs were calculated. Using event history analysis methods, time to recurrent gain and loss of at least one HPV type was determined, separately. Baseline any-type and high risk-type HPV prevalence was 60.6% and 24.2%, respectively. Cumulative any-HPV and high-risk HPV prevalence over the 16-week period was 84.8% and 60.6%, separately.

RESULTS

Overall, there were 319 events of detection and 313 events of loss of detection. Median times to a recurrent detection and loss of detection were 11 and seven days, respectively. Neither vaginal sex nor condom use during follow-up was associated with recurrent viral detection or loss of detection. Assuming the cumulative 16-week prevalence reflects the true prevalence of infection, the baseline any-HPV prevalence underestimated infection status by 24.2%, with a bootstrapped mean of 20.2% [95% confidence interval (CI), 8.9%-29.6%].

CONCLUSIONS

These findings suggest that a substantial proportion of HPV-infected women are misclassified as being uninfected when using a single-time DNA measurement.

IMPACT

Short-term variation in detectable HPV DNA needs to be considered while interpreting the natural history of infections using single samples collected at long intervals.

Laboratory management of cervical intraepithelial neoplasia: proposing a new paradigm

Since the discovery of human papillomavirus (HPV) type 16 in early 80s, the link between HPV and cervical cancer has been established with certainty, a function of the discovery and cloning of a range of HPV types associated with both cancer precursors (cervical intraepithelial neoplasia or CIN) and carcinomas and extensive epidemiologic, clinical, pathologic, and experimental data. These accumulated results have culminated in new paradigms of cancer prevention through screening and triage. Despite this, the management of women with CIN is still suboptimal and the overtreatment of these conditions still occurs, largely due to the lack of clarity regarding which precancerous lesions are most likely to progress in grade. Recently, a discrete population of cuboidal cells was discovered at the cervical squamocolumnar junction, the anatomic site where the large majority of HPV-related (pre)neoplastic lesions develop. These cells seem to be embryonic in nature and participate both in benign metaplasias and the initial phase of precancer development. This review summarizes the historical evolution of precursor management, assesses the potential role of this and other discoveries in segregating lower from higher-risk precursors, and examines their potential impact on the management of women with real or potential cervical cancer precursors.

Immunization with a poly (lactide co-glycolide) encapsulated plasmid DNA expressing antigenic regions of HPV 16 and 18 results in an increase in the precursor frequency of T cells that respond to epitopes from HPV 16, 18, 6 and 11

A phase II trial was conducted in subjects with human papillomavirus (HPV) associated high-grade cervical dysplasia testing the safety and efficacy of a microparticle encapsulated pDNA vaccine. Amolimogene expresses T cell epitopes from E6 and E7 proteins of HPV types 16 and 18. An analysis was performed on a subset of HLA-A2+ subjects to test whether CD8+ T cells specific to HPV 16, 18, 6 and 11 were increased in response to amolimogene immunization. Of the 21 subjects receiving amolimogene, 11 had elevated CD8+ T cell responses to HPV 16 and/or 18 peptides and seven of these also had increases to corresponding HPV 6 and/or 11 peptides. In addition, T cells primed and expanded in vitro with an HPV 18 peptide demonstrated cross-reactivity to the corresponding HPV 11 peptide. These data demonstrate that treatment with amolimogene elicits T cell responses to HPV 16, 18, 6 and 11.

Viral load in the natural history of human papillomavirus type 16 infection: a nested case-control study

BACKGROUND

Viral load may influence the course of human papillomavirus type 16 (HPV-16) infection.

METHODS

This case-control study was nested within the 2-year Atypical Squamous Cells of Undetermined Significance and Low-Grade Squamous Intraepithelial Lesion Triage Study, in which women were followed semiannually for HPV and cervical intraepithelial neoplasia (CIN). Case patients (n = 62) were women diagnosed with CIN3 following HPV-16-positive detection at a follow-up visit. HPV-16-positive controls (n = 152) without CIN2 or CIN3 were matched to cases based on the follow-up visit in which viral load was measured. Real-time polymerase chain reaction was used for HPV-16 DNA quantification.

RESULTS

The risk of CIN3 increased with increasing HPV-16 DNA load at the follow-up visit (odds ratio, 1.63; 95% confidence interval, 1.33-1.99 per 1 log(10) unit increase); the association was not affected by whether HPV-16 was present at enrollment. When HPV-16 was present at both enrollment and follow-up, viral load remained high among cases (P = .77) but decreased substantially among controls (P = .004). Among women with HPV-16 found initially during follow-up, viral load in the first HPV-16-positive sample was associated with short-term persistence; load was higher in those with infection, compared with those without infection, 1 visit after the initial positivity (P = .001).

CONCLUSIONS

Viral load of newly detected infections and changes in viral load predict persistence and progression of HPV-16 infections.

A weakly positive human papillomavirus Hybrid Capture II result correlates with a significantly lower risk of cervical intraepithelial neoplasia 2,3 after atypical squamous cells of undetermined significance cytology

OBJECTIVE

The Hybrid Capture II assay (hc2; QIAGEN, Inc) for high-risk human papillomavirus (hrHPV) is an in vitro nucleic acid hybridization assay using chemiluminescence for the qualitative detection of hrHPV DNA in cervical samples. Results are reported as a ratio of relative light units (RLUs) to a cutoff value based on a positive control. Specimens with RLU ratios of 1.0 or higher are scored positive for hrHPV. We tested the hypothesis that hrHPV positives with low-positive RLU ratios (1-10) had a lower prevalence of cervical intraepithelial neoplasia 2,3 (CIN 2,3) on histologic follow-up.

MATERIALS AND METHODS

Relative light unit ratios for 388 consecutive hrHPV-positive cervical cytologic specimens interpreted as atypical squamous cells of undetermined significance (ASCUS) were reviewed. Individual RLU ratios were compared with outcome histologic diagnosis in cases with colposcopic follow-up and tissue sampling (biopsy and/or endocervical curettage; n = 236).

RESULTS

Of 236 cases with histologic follow-up, 63 had RLU ratios in the range of 1 to 10; of these, 53 (84.1%) were negative for CIN, 7 (11.1%) had CIN 1, 1 (1.6%) had CIN of uncertain grade, and 2 (3.2%) had CIN 2,3. The difference in CIN 2,3 outcome between RLU ratios of 1 to 10 (3.2%) versus over 10 (17.3%) was significant (p =.0047). The difference in prevalence of CIN 1 was not significant (p =.67).

CONCLUSIONS

An RLU ratio of 10 or less was associated with a significantly lower prevalence of CIN 2,3 on biopsy outcome after a Pap test result of ASCUS. The much lower prevalence of underlying CIN 2,3 in patients who are weakly HPV-positive may justify modification of the management algorithm for this subset of women with ASCUS.

Histological 'progression' from low (LSIL) to high (HSIL) squamous intraepithelial lesion is an uncommon event and an indication for quality assurance review

An accurate assessment of 'progression' from a low (LSIL) to high (HSIL) grade squamous intraepithelial lesion (cervical intraepithelial neoplasia (CIN)2 or CIN3) of the cervix is critical to ascertaining HSIL outcome risk, the value of predictive biomarkers, and the need for excisional therapy. We obtained biopsy outcome data on a series of initially diagnosed LSIL to assess this risk. Consecutive biopsy diagnoses of LSIL were obtained from the archives, and the frequency of HSIL biopsy outcomes were ascertained by record and histological review. Then, a 'numerical severity score' was recorded for each diagnosis: LSIL (1-2), CIN2 (3-4) and CIN3 (5-6) with lower and higher values corresponding to the degree (low vs high) of histological severity within each category, respectively. Of 264 initial LSILs, 29 (11%) were reported with an HSIL outcome. However, histological review of 21 of these HSILs confirmed only 8 (38%) HSIL diagnoses by review with the numerical severity score: three cases scored as 5, three cases scored as 4, and two cases scored as 3; the remaining 13 cases were assigned a numerical severity score of 1 or 2. P16 immunostains of corresponding previous and subsequent biopsies were discordant in 4 of 12 cases (33%). In a blind review of a randomly selected series of HSILs from the same practice, HSIL was significantly more likely to be confirmed on re-review (10 of 13 (77%), P=0.024). These findings show that confirmed HSIL outcomes (on review) following an LSIL biopsy are infrequent ( approximately 3%). A diagnosis of HSIL following an LSIL should always be reviewed, as this diagnostic pairing may more likely be associated with a diagnostic error.

Identification of vaccine human papillomavirus genotypes in squamous intraepithelial lesions (CIN2-3)

OBJECTIVE

To identify the prevalence of human papillomavirus vaccine genotypes and non-vaccine genotypes implicated in the appearance of cervical intraepithelial neoplasia (CIN2-3).

METHODS

Prospective study of 519 women with abnormal cytology. All the women underwent a second Papanicolaou test, cervicovaginal sampling for type-specific HPV detection and colposcopy, and women with abnormal colposcopy results were referred to biopsy. Pearson's chi-square test was used for statistical analysis.

RESULTS

HPV was detected in 340 patients (65.5%), and in 125 (24%) more than one HPV genotype was present. We selected 206 patients with CIN2 or CIN3 confirmed by biopsy. In 88 (42.7%) of these patients, HPV types 16 and 18 were detected, but only 58 (28.2%) without co-infection by other high-risk or probable high-risk HPV types. In 115 (55.8%) women diagnosed with CIN2 or CIN3 high-risk or probable high-risk HPV types other than 16 or 18 were found. High-risk and/or probable high-risk HPV genotypes not included in the vaccine were isolated in this study more frequently than 16 or 18, and this difference was statistically significant (p=0.047). Of the 206 women diagnosed with CIN2 or CIN3, 19 tested negative for HPV and 14 tested positive for low-risk HPV types.

CONCLUSION

Only 28.2% of women with CIN2 or CIN3 confirmed by biopsy were infected exclusively by HPV type 16 or 18, a finding that places in doubt the degree of protection afforded by HPV vaccination.

HPV vaccines: the beginning of the end for cervical cancer

Vaccines prophylactic against infection with human papillomavirus (HPV) are based on alum adjuvanted virus-like particles. Two such vaccines have recently been shown to prevent persistent HPV infection and associated cervical cancer precursor lesions. The genotype-specific neutralising antibody directed at conformational epitopes of the L1 major capsid protein is likely to mediate protection. Vaccines therapeutic for persisting HPV infection can eliminate transplantable tumors in animal models, but are of limited efficacy in mice grafted with skin that expresses HPV antigens or in humans. This paradox has been partially resolved by data clarifying the immunoregulatory role of skin cytokines (e.g. transforming growth factor-beta and interleukin-10) and the consequences of antigen presentation by subsets of skin-associated antigen-presenting cells.

The natural history of cervical HPV infection: unresolved issues

The identification of high-risk human papillomavirus (HPV) types as a necessary cause of cervical cancer offers the prospect of effective primary prevention and the possibility of improving the efficiency of cervical screening programmes. However, for these opportunities to be realized, a more complete understanding of the natural history of HPV infection, and its relationship to the development of epithelial abnormalities of the cervix, is required. We discuss areas of uncertainty, and their possible effect on disease prevention strategies.

Polymers for gene delivery across length scales

A number of human diseases stem from defective genes. One approach to treating such diseases is to replace, or override, the defective genes with normal genes, an approach called 'gene therapy'. However, the introduction of correctly functioning DNA into cells is a non-trivial matter, and cells must be coaxed to internalize, and then use, the DNA in the desired manner. A number of polymer-based synthetic systems, or 'vectors', have been developed to entice cells to use exogenous DNA. These systems work across the nano, micro and macro length scales, and have been under continuous development for two decades, with varying degrees of success. The design criteria for the construction of more-effective delivery vectors at each length scale are continually evolving. This review focuses on the most recent developments in polymer-based vector design at each length scale.

Dynamics of HPV16 DNA load reflect the natural history of cervical HPV-associated lesions

BACKGROUND

High burden of high risk human papillomavirus (HR HPV) has been shown to be predictive for the development of high grade cervical lesions and invasive cancers. However, low viral load cannot inevitably exclude progression towards cervical diseases. Moreover, few studies addressed whether viral load could predict infection clearance.

OBJECTIVES

We carried out a retrospective study to analyze the variations of HPV16 load over time as a predictive marker of clinical outcome.

STUDY DESIGN

The population consisted of 38 women who were found HR HPV positive by HCII test at study entry. Among them, 13 had developed a CIN2/3 (cases) and 25 had a negative HCII test and a normal cytology (controls) at study exit. The HPV16 DNA loads were quantified in 132 longitudinal cervical samples using quantitative real-time PCR.

RESULTS

At study entry, the median of HPV16 load was not statistically different between controls and cases. However, when using a cut-off value of 200 copies/10(3) cells, the rate of cumulative incidence of CIN2/3 at 18 months increased from 14% in women with a load<or=200 copies/10(3) cells to 48% in women with a load>200 copies/10(3) cells. The longitudinal analysis performed on follow-up samples showed that in cases the progression to CIN2/3 was linked to HPV16 burden increasing over time, whereas in controls a decrease of at least 1 log HPV16 DNA load was observed over>or=2 time points.

CONCLUSIONS

These results show that kinetics of HPV load, rather than a single HPV detection, might be more reliable to estimate whether a HPV infection will progress or be cleared.

Type-Specific HPV Testing as a Predictor of High-Grade Squamous Intraepithelial Lesion Outcome after Cytologic Abnormalities

OBJECTIVE

Human papillomavirus (HPV) risk assignment influences management after a cytologic diagnosis of atypical squamous cells of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesion (LSIL). This study addressed whether type-specific HPV testing predicts risk of biopsy outcome of high-grade cervical intraepithelial neoplasia (CIN 2,3).

MATERIALS AND METHODS

A total of 162 ASCUS or LSIL diagnoses with colposcopic follow-up were evaluated and placed in 3 groups: Analysis 1: (high-risk HPVs including types 53 and 66; Analysis 2 (high-risk HPVs excluding types 53 and 66); and Analysis 3 (high-risk HPVs including type 53 and excluding type 66).

RESULTS

CIN 2,3 biopsy results followed low-risk HPVs in 0%, 3%, and 0% of scenarios 1, 2, and 3, respectively; 21%, 40%, and 27% of smears were classified as low risk, respectively. Of HPV 53 infections, 13.6% had CIN 2,3 biopsy outcomes.

CONCLUSIONS

Type-specific HPV testing accurately classifies a group of HPV-positive LSIL/ASCUS cases at low risk for CIN 2,3 at the first follow-up visit. Classifying HPV 53 as low-risk increases slightly the proportion of HSIL outcomes in the low-risk group, but may not increase cancer risk. HPV 53 merits designation as a high-risk HPV based only [corrected] on the proportion of CIN 2,3 in follow-up biopsy.

p16iNK4a as a complementary marker of high-grade intraepithelial lesions of the uterine cervix. I: Experience with squamous lesions in 189 consecutive cervical biopsies

AIM

To test the usefulness of p16(INK4a) immunostaining for improving the diagnostic accuracy of cervical punch biopsies referred to a routine laboratory setting during the investigation of women with abnormal Papanicolaou smears.

METHODS

A total of 188 consecutive and unselected colposcopically directed cervical biopsies and a single contemporaneous cervical polyp were accessioned prospectively over a 3-month period, step-serially sectioned and examined by H&E and immunostained for p16(INK4a). The clinical context, results of concurrent Papanicolaou smears/ThinPrep slides and Digene hybrid capture tests for high-risk human papillomavirus (HPV) subtypes, as well as follow-up cervical smears/ThinPrep, biopsies and loop excisions of transformation zones or cone biopsies were all correlated with the morphological and immunohistochemical findings.

RESULTS

Seventy-seven biopsies (40.7%) displayed a high-grade squamous intraepithelial lesion (HGSIL; cervical intraepithelial neoplasia [CIN] 2-3), 27 (14.3%) showed a low grade squamous intraepithelial lesion (HPV +/- CIN1) and 85 (45%) showed a range of non-dysplastic (inflammatory or reactive) changes. Diffuse strong parabasal immunostaining for p16(INK4a), suggestive of integrated high-risk HPV DNA into the host genome, was observed in 81 biopsies (42.9%, including the cervical polyp) and correlated (>90%) with HGSIL in the H&E sections. Only one case revealed irreconcilable discordance between the histological features and this strong parabasal immunostaining pattern. Focal and weaker midzonal or superficial p16(INK4a) immunostaining, suggestive of episomal HPV infection, was noted in 19 biopsies (10%) and these biopsies exhibited a range of histological changes but predominantly low grade squamous intraepithelial lesion (LGSIL). No staining of the squamous epithelium was seen in 89 biopsies (47.1%). Again, only one case revealed irreconcilable discordance between the histological features and this negative immunostaining pattern. On review of all cases where discordant results were noted between the H&E appearances and expected p16(INK4a) immunostaining, we found 26 cases (13.7%) in which this discordance prompted justifiable modification of the original diagnosis.

CONCLUSIONS

Thus, within a routine diagnostic laboratory, p16(INK4a) immunostaining appears to be a very useful adjunctive test in the examination of colposcopically directed cervical biopsies, in the diagnostic cascade of women investigated for abnormal Papanicolaou smears. It is possible, as further data accumulate concerning the importance of integration of high-risk HPV DNA into the host cell genome and the reliability with which this can be identified by p16(INK4a) immunostaining, that this will become the diagnostic 'lesion of interest', replacing the subjective histological grading of cervical dysplasia, in the management of such patients; i.e., the discriminatory watershed between continued surveillance and active intervention.

Progress towards a vaccine for cervical cancer

PURPOSE OF REVIEW

The aim of this review is to present for gynaecologists new information on human papillomavirus infections, their spontaneous evolution, and their consequences on the transformation of target tissues. It emphasizes the need for vaccination, both as a preventive tool and therapeutic agent, and reports the progress made so far.

RECENT FINDINGS

Human papillomavirus infection is often transient and spontaneously reversible. High-risk human papillomavirus persistence is the major cause of cancerous transformation in several tissues. Preventive vaccination has already demonstrated remarkable efficacy against the development of some human papillomavirus type related anogenital lesions. Therapeutic vaccination has now also been developed to cure pre-existing lesions. Some new screening protocols can be derived from these experiments.

SUMMARY

Both preventive and therapeutic human papillomavirus vaccinations will probably change our approach to the screening and therapy of human papillomavirus-related diseases in the next few years. The mass vaccination of adolescent patients should lower the frequency of these very frequently lethal infections.

Plasmid vaccines and therapeutics: from design to applications

In the late 1980s, Vical and collaborators discovered that the injection into tissues of unformulated plasmid encoding various proteins resulted in the uptake of the plasmid by cells and expression of the encoded proteins. After this discovery, a period of technological improvements in plasmid delivery and expression and in pharmaceutical and manufacturing development was quickly followed by a plethora of human clinical trials testing the ability of injected plasmid to provide therapeutic benefits. In this chapter, we summarize in detail the technologies used in the most recent company-sponsored clinical trials and discuss the potential for future improvements in plasmid design, manufacturing, delivery, formulation and administration. A generic path for the clinical development of plasmid-based products is outlined and then exemplified using a case study on the development of a plasmid vaccine from concept to clinical trial.