Repositioning of a Diaminothiazole Series Confirmed to Target the Cyclin-Dependent Kinase CRK12 for Use in the Treatment of African Animal Trypanosomiasis

African animal trypanosomiasis or nagana, caused principally by infection of the protozoan parasites Trypanosoma congolense and Trypanosoma vivax, is a major problem in cattle and other livestocks in sub-Saharan Africa. Current treatments are threatened by the emergence of drug resistance and there is an urgent need for new, effective drugs. Here, we report the repositioning of a compound series initially developed for the treatment of human African trypanosomiasis. A medicinal chemistry program, focused on deriving more soluble analogues, led to development of a lead compound capable of curing cattle infected with both T. congolense and T. vivax via intravenous dosing. Further optimization has the potential to yield a single-dose intramuscular treatment for this disease. Comprehensive mode of action studies revealed that the molecular target of this promising compound and related analogues is the cyclin-dependent kinase CRK12.

Development and evaluation of an ITS1 "Touchdown" PCR for assessment of drug efficacy against animal African trypanosomosis

Animal African trypanosomoses (AAT) are caused by flagellated protozoa of the Trypanosoma genus and contribute to considerable losses in animal production in Africa, Latin America and South East Asia. Trypanosoma congolense is considered the economically most important species. Drug resistant T. congolense strains present a threat to the control of AAT and have triggered research into discovery of novel trypanocides. In vivo assessment of trypanocidal efficacy relies on monitoring of treated animals with microscopic parasite detection methods. Since these methods have poor sensitivity, follow-up for up to 100 days after treatment is recommended to increase the chance of detecting recurrent parasitaemia waves. Molecular techniques are more amendable to high throughput processing and are generally more sensitive than microscopic detection, thus bearing the potential of shortening the 100-day follow up period. The study presents a "Touchdown" PCR targeting the internal transcribed spacer 1 of the ribosomal DNA (ITS1 TD PCR) that enables detection and discrimination of different Trypanosoma taxa in a single run due to variations in PCR product sizes. The assay achieves analytical sensitivity of 10 parasites per ml of blood for detection of T. congolense savannah type and T. brucei, and 100 parasites per ml of blood for detection of T. vivax in infected mouse blood. The ITS1 TD PCR was evaluated on cattle experimentally infected with T. congolense during an investigational new veterinary trypanocide drug efficacy study. ITS1 TD PCR demonstrated comparable performance to microscopy in verifying trypanocide treatment success, in which parasite DNA became undetectable in cured animals within two days post-treatment. ITS1 TD PCR detected parasite recrudescence three days earlier than microscopy and had a higher positivity rate than microscopy (84.85% versus 57.58%) in 66 specimens of relapsing animals collected after treatments. Therefore, ITS1 TD PCR provides a useful tool in assessment of drug efficacy against T. congolense infection in cattle. As the assay bears the potential for detection of mixed infections, it may be applicable for drug efficacy studies and diagnostic discrimination of T. vivax and T. congolense against other pathogenic trypanosomes, including T. brucei, T. evansi and T. equiperdum.

Community- and farmer-based management of animal African trypanosomosis in cattle

Tsetse eradication is impossible in many parts of Africa given environmental, political, and economic circumstances. Animal African trypanosomosis (AAT) control then relies on implementation of local, integrated control strategies by communities or farmers that must take into account the eco-epidemiological context and the cattle rearing system to be sustainable.

HIV/AIDS prevalence testing--merits, methodology and outcomes of a survey conducted at a large mining organisation in South Africa

OBJECTIVES

To determine the HIV prevalence rate at Anglo Platinum, a large, multinational organisation operating in South Africa (Gauteng, Limpopo and North-West), and to assess the merits, methodology and outcomes of the survey.

METHODS

A sample of 11,339 individuals, representing 18.4% of the organisation's employees, were tested for HIV. HIV prevalence was determined using the Wellcozyme HIV 1+2 GACELISA test (oral fluid assay), and variables such as age, site, grade and gender were analysed.

RESULTS

The overall prevalence rate was 24.6% (95% confidence interval (CI): 20.4-28.8), translating into approximately 15,167 HIV-infected individuals. Interestingly, there was considerable variation in prevalence between sites within the same geographical regions, highlighting the limitations of using data obtained from antenatal HIV surveillance surveys. As an example, the prevalence at sites in Limpopo province ranged from 9.8% to 19%, with the same basic demographic data in terms of race, age and gender.

CONCLUSION

The survey data enabled the organisation to plan resource allocation appropriately for each business unit following their commitment to the treatment of infected employees with antiretroviral therapy. These baseline prevalence data also provide an opportunity for monitoring of proposed interventions using cross-sectional surveys at designated intervals in the future.

A community-based study to examine the effect of a youth HIV prevention intervention on young people aged 15-24 in South Africa: results of the baseline survey

OBJECTIVES

To determine whether South African youths living in communities that had either of two youth human immunodeficiency virus (HIV) prevention interventions [(a) loveLife Youth Centre or (b) loveLife National Adolescent Friendly Clinic Initiative] would have a lower prevalence of HIV, sexually transmitted infections (STIs), and high risk sexual behaviours than communities without either of these interventions.

METHODS

In 2002 the baseline survey of a quasi-experimental, community-based study was conducted in South Africa. In total 33 communities were included in three study arms (11 communities per study arm). The final sample included 8735 youths aged 15-24 years. All participants took part in a behavioural interview and were tested for HIV, gonorrhoea (Neisseria gonorrhoeae) and Chlamydia (Chlamydia trachomatis).

RESULTS

HIV prevalence was 20.0% among females and 7.5% among males (OR 3.93 95% CI 2.51-6.15). There were no significant differences between study arms for HIV, NG or CT prevalence at baseline. In multiple regression analyses, HIV was significantly associated with NG infection (OR 1.96 95% CI 1.24-3.12) but not with CT infection. Youths who reported >1 lifetime partner were also significantly more likely to be infected with HIV (OR 1.98 95% CI 1.55-2.52), as were those who reported ever having engaged in transactional sex (OR 1.86 P = 0.02) or having had genital ulcers in the past 12 months (OR 1.71 P < or = 0.001).

CONCLUSIONS

HIV prevention programmes must ensure that gender inequities that place young women at greater risk for HIV infection are urgently addressed and they must continue to emphasize the importance of reducing the number of sexual partners and STI treatment.

Cloning, sequencing and expression of the gene that encodes the major neutralisation-specific antigen of African horsesickness virus serotype 9

A marked improvement in the efficiency of cloning the large double stranded RNA (dsRNA) genome segments of African horsesickness virus (AHSV) was achieved when the dsRNA polyadenylation step was carried out with undenatured rather than strand-separated dsRNA. It is a prerequisite to use dsRNA of very high purity because in the presence of even trace amounts of single stranded RNA, the dsRNA appears to be poorly polyadenylated as judged by its effectiveness as a template for oligo-dT-primed cDNA synthesis. The full-length VP2 gene of AHSV-9, cloned by this approach, was sequenced and it was found to show the highest percentage identity (60%) to VP2 of AHSV-6, providing an explanation of why these two serotypes show some cross protection. The VP2 protein was also expressed in Spodoptera frugiperda (Sf9) cells by means of a baculovirus recombinant. The yield of the expressed VP2 was high, but the protein was found to be largely insoluble. Nine smaller, truncated VP2 peptides were subsequently expressed in insect cells, but no significant improvement in solubility of the peptides, as compared to that of the full-sized protein, was observed. A western immunoblot analysis of the overlapping peptides indicated the presence of a strong linear epitope located within a large hydrophilic domain between amino acids 369 and 403.