New approaches to vaccines for endemic and pandemic diseases of Africa with particular focus on building local competencies in Cameroon

Vaccines have been recognized as major and effective tools for the control and eventual elimination of infectious diseases and cancer. This brief review examines vaccine classification and development pipeline as well as recent innovations driving the vaccine development process. Using COVID-19 as an example recent innovation in vaccine development are highlighted. The review ends with a call for intensified efforts to build vaccine production capacity in Cameroon and other other African  countries. Les vaccins ont été reconnus comme des outils majeurs et efficaces pour le contrôle et l’élimination éventuelle des maladies infectieuses et du cancer. Cette brève revue examine la classification et le pipeline de développement de vaccins ainsi que les innovations récentes à l’origine du processus de développement de vaccins. En utilisant COVID-19 comme exemple, les innovations récentes dans le développement de vaccins sont mises en évidence. La revue se termine par un appel à intensifier les efforts pour renforcer les capacités de production de vaccins au Cameroun et dans d’autres pays africains

A rational approach for predicting the minimum composition of anti-parasite sub-unit vaccines: a multiple target vaccine hypothesis

The present article introduces a new concept, termed a multiple vaccine target hypothesis (MVTH) for determining the minimum number of vaccine targets (epitopes/antigens) necessary to construct a highly efficacious (greater than 90%) anti-parasite vaccine. Drawing inspiration from the Metabolic Control Analysis (MCA) and immunological reasoning it is proposed that for a multi-stage parasite an effective anti-parasite vaccine will necessarily act on more than one stage of the parasite in the definitive host. It is argued that the minimum number of sub-unit targets for a highly efficacious anti-parasite vaccine will vary from one parasite to the other and will be equal to twice the number of major parasite stages occurring in the human host. Quantitatively stated, Cv=2n where Cv the number of required targets is, and n represents the number of major parasite stages in the definitive host. Conditions when the value of Cv may deviate from what is predicted by the formula given above are discussed. Extensive literature search on malaria, onchocerciasis and schistosomiasis sub-unit vaccine development suggests that subunit vaccines constructed from single components and directed to just one parasite stage are less efficacious that multivariate sub-unit vaccines, and obviously whole parasite vaccines. MVTH therefore provides a rational framework for constituting a sub-unit anti-parasite vaccine.Keywords: Vaccine, malaria, Onchocerca volvulus, schistosomiasis, parasite, equatio

THE ANTIMALARIAL POTENTIAL OF MEDICINAL PLANTS USED FOR THE TREATMENT OF MALARIA IN CAMEROONIAN FOLK MEDICINE

Malaria remains one of the leading public health problems in Cameroon as in other parts of Sub-Saharan Africa. In the past decades, this situation has been aggravated by the increasing spread of drug-resistant Plasmodium falciparum strains. New antimalarial drug leads are therefore urgently needed. Traditional healers have long used plants to prevent or cure infections. This article reviews the current status of botanical screening efforts in Cameroon as well as experimental studies done on antimalarial plants. Data collected from 54 references from various research groups in the literature up to June 2007 shows that 217 different species have been cited for their use as antimalarials in folk medicine in Cameroon. About a hundred phytochemicals have been isolated from 26 species some among which are potential leads for development of new antiamalarials. Crude extracts and or essential oils prepared from 54 other species showed a wide range of activity on Plasmodium spp. Moreover, some 137 plants from 48 families that are employed by traditional healers remain uninvestigated for their presumed antimalarial properties. The present study shows that Cameroonian flora represents a high potential for new antimalarial compounds. Further ethnobotanical surveys and laboratory investigations are needed to fully exploit the potential of the identified species in the control of malaria

The Cameroon Academy of Sciences model of evidence-based science advice

The evidence-based science advice (ESA) effort of the Cameroon Academy of Sciences (CAS) since 23 years has been reviewed. The objective throughout has been to enable science influence policy/decision making at all levels – national, regional and global. The key partners of CAS included the United States National Academy of Sciences (USNAS), the German Academy of Sciences (Leopoldina), the Royal Society of United Kingdom, as well as the Network of African Science Academies (NASAC), the InterAcademy Partnership (Science, Health, Research), the Commonwealth Science Academies and the International Science Council. The mechanisms used included consensus studies, workshops, public lectures, participation in sectoral committees, summaries of key scientific publications and joint statements. Priorities handled through convening activities were triggered by policy/decision making sector requests or Academy foresights. The response/impact of the effort varied from media coverage through policy/programme change/orientation. The major challenges faced included insufficient financial/human resources, inadequate office space, and weak links with government. These challenges must be addressed to enable effective evidence-based science advice which is increasingly unavoidable for sustainable development.Keywords: Evidence-based science, advice, policy, decision-make

Evidence for the exacerbation of lymphedema of geochemical origin, podoconiosis, by onchocerciasis

SummaryThe study was conducted to investigate a variation in the distribution of endemic elephantiasis previously determined to be of geochemical origin in three neighbouring and essentially homogenous villages, Bambili, Bambui and Finge of the Bambui Health District of NW Cameroon. A total of 301 subjects were examined for onchocerciasis and lymphatic filariasis in the area using standard procedures. The onchocercal microfilarial prevalence varied from 6.5% in Bambili through 20.4% in Bambui to 60.4% in Finge. The onchocercal serological prevalence based on IgG4 detection followed a similar trend. By contrast, blood microfilariae were absent in the area as verified by use of sensitive techniques. The community prevalence of elephantiasis varied from 1.1% in Bambili to 4.4% in Bambui and 10.4% in Finge. The correlation between the parasitological prevalence of onchocerciasis and the prevalence of lymphedema in the three villages was strong (r=0.99, p<0.05). We confirm that the elephantiasis in the area is of geochemical origin and the results suggest that it is being exacerbated by onchocercal lymphadenitis

Molecular cloning and differential IgG responses to a histidine-rich antigen (OvL3.C1) of Onchocerca volvulus by selected residents of onchocerciasis endemic regions in Cameroon and Ecuador

In order to further investigate host-parasite interactions in onchocerciasis, a major Onchocerca volvulus histidine rich antigen termed OvL3.C1 was isolated from an O. volvulus cDNA library using antibodies from putatively immune subjects living in onchocerciasis endemic communities in Cameroon. Analysis of its sequences predicted the protein to be helix-rich with a single transmembrane region. Recombinant OvL3.C1 antigen induced from pBAD-TOPO/Thio vector in Escherichia coli was purified as inclusion bodies and further by a combination of Ni2+ chelate chromatography and electroelution. Anti-OvL3.C1 immunoglobulin G (IgG) subclass levels were assessed by ELISA in 15 pairs and 18 pairs of selected and cross-matched infected and putatively immune subjects from Cameroon and Ecuador, respectively. IgG3 and IgG4 levels were shown to be significantly higher in putatively immune (immune protected) subjects. A higher IgG3 level in endemic normal subjects is implicated in parasite killing and the development of the putative immune status while IgG4 has been shown to block onchocercal pathology. OvL3.C1 is a dominant antigen in onchocerciasis which elicits strong responses in subjects expose to both African and South American forms of onchocerciasis. It is therefore an important player in mechanisms of resistance or allergy attenuation in onchocerciasis.Keywords: Onchocerciasis, immunoglobulin G, putative immunit

Environmental Factors Affecting Malaria Parasite Prevalence in Rural Bolifamba, South- West Cameroon

The impact of some environmental factors on malaria parasite prevalence was investigated in rural Bolifamba, Cameroon. The study population comprised 1454 subjects aged 0 \u2013 65 years. Malaria parasite prevalence was higher in the rainy (50.1%) than in the dry season (44.2%) with a significant difference (P=0.001) in mean parasite density between seasons. Individuals &lt;15 years old, had significantly higher malaria parasite prevalence (55.5%) than those &gt;15 years (37.4%). Malaria parasite prevalence (P=0.001) and parasite density (P=0.03) were higher in the individuals of wooden plank houses than those of cement brick houses. Inhabitants of houses surrounded by bushes or garbage heaps and swamps or stagnant water showed higher malaria parasite prevalence and densities compared with those from cleaner surroundings. Anopheles gambiae (63.8%) and A. funestus (32.8%) were associated with perennial transmission of malaria. Our data indicates that poor environmental sanitation and housing conditions may be significant risk factors for malaria parasite burden in Bolifamba

Integrated strategies for control of devastating transmissible diseases in Cameroonian urban areas: The case of malaria, tuberculosis and waterborne diseases.

The recent, fast and poorly handled rural to urban migrations of people has led to unplanned settlement patterns, overcrowding and insufficient sanitation facilities, shortages of potable water, and general an unhealthy environment. The emerging cities have thus become areas where the most devastating scourges (malaria, tuberculosis and water borne diseases) continue undermine the socio-economic development of the urban areas. Herein, we discuss the current health challenges in major Cameroonian cities and argue that only a multidisciplinary approach including diagnosis and treatment, environmental care, and health education, is likely to address the health challenges in the emerging urban settings. From a recent publication by Titanji (2014) on lessons learned from the recent Ebola crisis in West African countries, some key elements of an integrated strategy for addressing health challenges in major Cameroonian cities are discussed.Key words: Malaria, Tuberculosis, waterborne diseases, Cameroon cities, integrated approac

The Antimalarial Potential Of Medicinal Plants Used For The Treatment Of Malaria In Cameroonian Folk Medicine

Malaria remains one of the leading public health problems in Cameroon as in other parts of Sub-Saharan Africa. In the past decades, this situation has been aggravated by the increasing spread of drug-resistant Plasmodium falciparum strains. New antimalarial drug leads are therefore urgently needed. Traditional healers have long used plants to prevent or cure infections. This article reviews the current status of botanical screening efforts in Cameroon as well as experimental studies done on antimalarial plants. Data collected from 54 references from various research groups in the literature up to June 2007 shows that 217 different species have been cited for their use as antimalarials in folk medicine in Cameroon. About a hundred phytochemicals have been isolated from 26 species some among which are potential leads for development of new antiamalarials. Crude extracts and or essential oils prepared from 54 other species showed a wide range of activity on Plasmodium spp. Moreover, some 137 plants from 48 families that are employed by traditional healers remain uninvestigated for their presumed antimalarial properties. The present study shows that Cameroonian flora represents a high potential for new antimalarial compounds. Further ethnobotanical surveys and laboratory investigations are needed to fully exploit the potential of the identified species in the control of malaria