PCR-based analytics of gene therapies using adeno-associated virus vectors: Considerations for cGMP method development.

The field of gene therapy has evolved and improved so that today the treatment of thousands of genetic diseases is now possible. An integral aspect of the drug development process is generating analytical methods to be used throughout clinical and commercial manufacturing. Enumeration and identification assays using genetic testing are critical to ensure the safety, efficacy, and stability of many active pharmaceutical ingredients. While nucleic acid-based methods are already reliable and rapid, there are unique biological, technological, and regulatory aspects in gene therapies that must be considered. This review surveys aspects of method development and validation using nucleic acid-based testing of gene therapies by focusing on adeno-associated virus (AAV) vectors and their co-transfection factors. Key differences between quantitative PCR and droplet digital technologies are discussed to show how improvements can be made while still adhering to regulatory guidance. Example validation parameters for AAV genome titers are described to demonstrate the scope of analytical development. Finally, several areas for improving analytical testing are presented to inspire future innovation, including next-generation sequencing and artificial intelligence. Reviewing the broad characteristics of gene therapy assessment serves as an introduction for new researchers, while clarifying processes for professionals already involved in pharmaceutical manufacturing.

CRISPR Interference To Inducibly Repress Gene Expression in Chlamydia trachomatis.

The ability to inducibly repress gene expression is critical to the study of organisms, like Chlamydia, with reduced genomes in which the majority of genes are likely to be essential. We recently described the feasibility of a CRISPR interference (CRISPRi) system to inducibly repress gene expression in Chlamydia trachomatis. However, the initial system suffered from some drawbacks, primarily leaky expression of the anhydrotetracycline (aTc)-inducible dCas9 ortholog and plasmid instability, which prevented population-wide studies (e.g., transcript analyses) of the effects of knockdown. Here, we describe various modifications to the original system that have allowed us to measure gene expression changes within a transformed population of C. trachomatis serovar L2. These modifications include (i) a change in the vector backbone, (ii) the introduction of a weaker ribosome binding site driving dCas9 translation, and (iii) the addition of a degradation tag to dCas9 itself. With these changes, we demonstrate the ability to inducibly repress a target gene sequence, as measured by the absence of protein by immunofluorescence analysis and by decreased transcript levels. Importantly, the expression of dCas9 alone (i.e., without a guide RNA [gRNA]) had minimal impact on chlamydial growth or development. We also describe complementation of the knockdown effect by introducing a transcriptional fusion of the target gene 3' to dCas9. Finally, we demonstrate the functionality of a second CRISPRi system based on a dCas12 system that expands the number of potential chromosomal targets. These tools should provide the ability to study essential gene function in Chlamydia.

Insights into the mode of action of 1,2,6,7-tetraoxaspiro [7.11] nonadecane (N-89) against adult Schistosoma mansoni worms.

Control of morbidity associated with schistosomiasis via chemotherapy largely relies on the drug praziquantel. Repeated therapy with praziquantel has created concerns about the possible selection of resistant worms and necessitated the search for novel drugs to treat schistosomiasis. Here, a murine model was infected with Schistosoma mansoni and treated with oral 1,2,6,7-tetraoxaspiro [7.11] nonadecane (N-89), which caused a significant reduction in fecundity and egg burden and reduced morbidity when administered at 5-weeks post-infection. The analysis showed that the mode of action occurred through the ingestion of activated N-89 by the worms, and that there was no direct external effect on the S. mansoni worms. Ultrastructural analysis of the treated worms showed disruptions in the gut lumen and the presence of large volumes of material, suggestive of undigested blood meals or red blood cells. In addition, there were reduced vitelline cells in female worms and damage to sub-tegmental musculature in male worms. Eggs recovered from the treated mice showed both damage to the eggs and the production of immature eggs. Expression of mRNA responsible for gut and digestive function and egg production was also significantly affected by N-89 treatment, whereas control genes for musculature showed no significant changes. Thus, N-89 drastically affected the total digestive function and egg production of S. mansoni worms. Physiological processes requiring heme uptake such as egg production and eggshell formation were subsequently affected, suggesting that the compound could be a possible therapeutic drug candidate for schistosomiasis control.

Novel synthetic compounds with endoperoxide structure damage juvenile stage of Schistosoma mansoni by targeting lysosome-like organelles.

The new synthetic compound 1,2,6,7-tetraoxaspiro[7.11]nonadecan (N-89), a novel anti-malaria drug candidate, is also a promising drug candidate against schistosomiasis with killing effects against juvenile stage of S. mansoni. In order to investigate how N-89 kills schistosomes, we used a derivative of N-89, 6-(1,2,6,7-tetraoxaspiro[7.11] nonadec-4-yl)hexan-1-ol (N-251), which enables us to conjugate with fluorescent reagents. Firstly, N-251 showed strong killing effects to larvae of S. mansoni in vitro. Ultrastructural analysis showed the disruptions of the lysosome-like organelles or the acetabular glands, followed by cytoplasmic lysis inside the worm body in N-251-treated group under electron microscopy. For rhodamine-conjugated N-251 and organelle markers, we observed that N-251 accumulated in acidic organelle. In addition, LysoTracker signals in these acidic organelles disappeared in N-251-treated group over time. Finally, we observed that the activity of cathepsin B, a lysosome-specific enzyme, was also decreased together with alternation of acidic organelle marker signal by N-251-treated group. These results suggested that our synthesized compounds induced the dysfunction or the disruption of acidic lysosome-like organelles and finally led to worm death.

Toxoplasma gondii infections among pregnant women, children and HIV-seropositive persons in Accra, Ghana.

BACKGROUND: Toxoplasma gondii infection can lead to severe disease outcomes in immune-compromised people. This study sought to determine the seroprevalence of anti-T. gondii antibodies among pregnant women, hospitalized children (<5 years old) and HIV-seropositive persons in Accra. METHODS: A cross-sectional study was conducted in two hospitals in Accra, and a total of 450 voluntary participants were recruited for the study consisting of 125 pregnant women, 200 children and 125 HIV-seropositive persons. Serum was obtained from venous blood safely drawn from each participant and tested for specific anti-Toxoplasma antibodies IgG and IgM by ELISA. A serological criterion for seropositivity was a positive test result for any of the two anti-Toxoplasma antibodies or a combination of both. Questionnaire interviews were conducted to obtain personal information and Toxoplasma infection risk-related data. RESULTS: Those who tested seropositive for anti-T. gondii antibodies were 51.2 % (64/125) pregnant women, 58.0 % (116/200) children and 57.6 % (72/125) HIV patients. The major risk factors associated with anti-T. gondii seropositivity were identified as age (in children), handling raw meat and gravida status (in pregnant women). The results of this study confirmed that the seroprevalence of T. gondii infection is high among pregnant women, hospitalized children <5 years old and HIV patients. CONCLUSIONS: A further study to investigate pre-pregnancy infections with T. gondii among women of childbearing age, seroconversion rate in pregnant women, rate of mother-to-child transmission and reactivated infections among HIV-seropositive persons is recommended.

Clonal types of Toxoplasma gondii among immune compromised and immune competent individuals in Accra, Ghana.

There are three major clonal lineages, types I, II, and III, of Toxoplasma gondii known to cause human toxoplasmosis worldwide. Toxoplasma gondii infections have, however, not been genotyped in Ghana. This study detected the clonal types infecting immune compromised and immune competent individuals in Accra, Ghana. Blood samples were obtained from 148 HIV seropositive pre-antiretroviral therapy individuals (0 ≤ CD4(+) T-cell count/µl blood ≤ 200) at the Fevers Unit and 149 HIV seronegative apparently healthy blood donors at the blood bank, all of the Korle-Bu Teaching Hospital. Genomic DNA was extracted and multilocus genotyping conducted by nested PCR-RFLP analysis using GRA6, SAG3, and BTUB gene markers. Among the HIV seropositive participants, 54.7% (81/148) were T. gondii DNA positive for any of the markers. Out of the 81, 42.0% (34) were positive for SAG3 only, 30.9% (25) for GRA6 only, 24.7% (20) for both SAG3 and GRA6, and 2.5% (2) for SAG3, GRA6, and BTUB. Overall, 93.8% of the positives were of clonal type II, 1.2% type I, while 4.9% (4) were atypical or mixed types (I and II). In the healthy blood donors, prevalence of T. gondii DNA positivity was 3.4% (5/149) by SAG3 and/or GRA6; among them, 60.0% (3/5) were type I, and the remaining 40.0%, type II. This study showed a relatively high prevalence of active T. gondii infections in immune compromised patients and low prevalence in immune competent individuals in Accra. Type II was highly prevalent. Detection of T. gondii in blood donors raises public health concerns and screening for T. gondii should be considered.

Congenital toxoplasmosis and pregnancy malaria detection post-partum: Effective diagnosis and its implication for efficient management of congenital infection.

Congenital toxoplasmosis (CT) and pregnancy malaria (PM) have been individually reported to cause severe negative outcomes in pregnancies but the diagnostic method is still debatable. This study sought to estimate the prevalence of PM and CT single and co-infections in pregnant women by using various specimens including plasma and placental tissues. Genomic DNA extracted from the placenta, cord blood or blood of mothers was tested by PCR. Conventional method of immunodiagnosis was done for CT. We tested 79 pregnant women aged 18-42 years (mean: 28±1.06). Prevalence of Plasmodium falciparum infection determined by PCR on mother's peripheral blood specimen was 6.3% whiles 57.3% was recorded for placental tissues (p<0.01). PCR testing for placental tissues showed 29.2% positive for Toxoplasma gondii, whiles 76.0% of mothers had serum IgG against T. gondii. It should be noted that 6.3% of the placental tissues showed PCR positive for SAG 3, a marker of active infection in T. gondii. Although there were no enhanced foetal disorders at birth in our study, there is a possibility of active transmission of T. gondii from mothers to foetuses even in immune mothers. Our study suggests that foetuses were exposed to P. falciparum and T. gondii in utero, and placenta is a better specimen for PCR in detecting such episodes. In cases of PCR-positive samples, clinical follow-up after birth may be important.