Damian Nota Anong

Induction of Strain-Transcending Antibodies Against Group A PfEMP1 Surface Antigens from Virulent Malaria Parasites

Sequence diversity in pathogen antigens is an obstacle to the development of interventions against many infectious diseases. In malaria caused by Plasmodium falciparum, the PfEMP1 family of variant surface antigens encoded by var genes are adhesion molecules that play a pivotal role in malaria pathogenesis and clinical disease. PfEMP1 is a major target of protective immunity, however, development of drugs or vaccines based on PfEMP1 is problematic due to extensive sequence diversity within the PfEMP1 family. Here we identified the PfEMP1 variants transcribed by P. falciparum strains selected for a virulence-associated adhesion phenotype (IgM-positive rosetting). The parasites transcribed a subset of Group A PfEMP1 variants characterised by an unusual PfEMP1 architecture and a distinct N-terminal domain (either DBLα1.5 or DBLα1.8 type). Antibodies raised in rabbits against the N-terminal domains showed functional activity (surface reactivity with live infected erythrocytes (IEs), rosette inhibition and induction of phagocytosis of IEs) down to low concentrations (<10 µg/ml of total IgG) against homologous parasites. Furthermore, the antibodies showed broad cross-reactivity against heterologous parasite strains with the same rosetting phenotype, including clinical isolates from four sub-Saharan African countries that showed surface reactivity with either DBLα1.5 antibodies (variant HB3var6) or DBLα1.8 antibodies (variant TM284var1). These data show that parasites with a virulence-associated adhesion phenotype share IE surface epitopes that can be targeted by strain-transcending antibodies to PfEMP1. The existence of shared surface epitopes amongst functionally similar disease-associated P. falciparum parasite isolates suggests that development of therapeutic interventions to prevent severe malaria is a realistic goal.

Drug Resistance Profiles of Mycobacterium tuberculosis Complex and Factors Associated with Drug Resistance in the Northwest and Southwest Regions of Cameroon

Background Anti-tuberculosis drug resistance continues to be a major obstacle to tuberculosis (TB) control programmes with HIV being a major risk factor in developing TB. We investigated anti-TB drug resistance profiles and the impact of socioeconomic as well as behavioural factors on the prevalence of TB and drug resistance in two regions of Cameroon with such data paucity. Methods This was a hospital-based study in which 1706 participants, comprising 1133 females and 573 males consecutively enrolled from selected TB and HIV treatment centres of the Northwest and Southwest regions. Demographic, clinical and self-reported risk behaviours and socioeconomic data were obtained with the consent of participants using questionnaires. Culture and drug resistance testing were performed according to standard procedures. Results The prevalence of resistance to at least one anti-TB drug was 27.7% and multi-drug resistance was 5.9%. Smoking, concurrent alcohol consumption and smoking, being on antiretroviral therapy for ≤ 12 months and previous household contact with TB patient were independently associated with tuberculosis prevalence, while only previous tuberculosis infection was associated with drug resistance in a univariate analysis. Conclusion The study showed a high prevalence of drug resistance TB in the study population with only previous TB infection associated with drug resistance in a univariate analysis. It also provides evidence in our context, of the role of alcohol and smoking in increasing the risk of developing TB, which is more likely in people living with HIV/AIDS. Therefore, it is important for public health authorities to integrate and intensify alcohol/smoking abstention interventions in TB and HIV control programs in Cameroon.

Isolation and expression of UB05, a Plasmodium falciparum antigen recognised by antibodies from semi-immune adults in a high transmission endemic area of the Cameroonian rainforest

Abstract Background: Antibodies in adults living in malaria endemic areas that target specific parasite antigens are implicated in protective immunity to infection and disease. This study aimed to identify, isolate and characterise targets of protective immunity in malaria. A Plasmodium falciparum antigen termed UB05 (Genbank Accession Number DQ235690: PlasmoDB PF10_ 0372) that had been isolated by immunoscreening with semi-immune sera was studied. Methods: Polymerase chain reaction, sequencing and bioinformatics were used to analyse the UB05 gene. A specific mouse anti-UB05 antibody was used in parasite reinvasion growth/inhibition assays and in immunoflourescence to localise the antigen. In a cross-sectional study, enzyme linked immunosorbent assay was used to study immunoglobulin G (IgG) responses to the antigen. Results: The gene revealed significant homologies with gene sequences from Plasmodia and other apicomplexan parasites and had two alleles in the wild P. falciparum isolates. The antigen is expressed by schizonts and segmented merozoites. Mouse antibodies against it marginally inhibit in vitro invasion of erythrocytes by P. falciparum. The IgG responses to UB05 were found to be significantly lower (p<0.05) in the sera of children (2–5 years) compared with adults (>18 years), with or without parasitaemia. However, parasitaemia correlated inversely (r=0.7– 0.75) with serum anti-UB05 IgG concentrations. Furthermore, anti-UB05 IgG concentrations were lower in the sera of febrile patients (body temperature >37.5°C) than their non-febrile counterparts regardless of parasitaemia status. Conclusions: These results are compatible with a role for UB05 in the development of immunity and as a marker of protective immunity to malaria. Clin Chem Lab Med 2009;47:1147–58.

Genetic and antigenic characterization of influenza A(H3N2) in Cameroon during the 2014-2016 influenza seasons

The first outbreak of influenza A(H3N2) occurred in 1968 and caused the third flu pandemic of the 20th century. It has affected multiple countries over time. The best strategy to reduce the burden of influenza is through vaccination whose efficacy varies with respect to the circulating strains. This study was performed to better understand the molecular evolution of influenza A(H3N2) and assess vaccine efficacy in Cameroon. Complete sequences of three gene segments were obtained from 2014 to 2016 influenza seasons in Cameroon. Hemagglutinin (HA), Neuraminidase (NA) and matrix (M) genes of 35 A(H3N2) virus strains were amplified and sequenced. Predicted vaccine efficacy was measured using the Pepitope model. Phylogenetic analysis of the HA gene showed that all Cameroonian strains had evolved away from the 3C.1-A/Texas/50/2012-like clade. Globally, 2014 virus strains clustered with the 2015–2016 vaccine strain, 3C.3a-A/Switzerland/9715293/2013, whereas 2015 and 2016 virus strains clustered with the 2016–2017 vaccine strain, 3C.2a-A/HongKong/4801/2014. In order to determine the genotypic drug susceptibility to neuraminidase inhibitors and amantadine, the NA and M2 protein coding sequences were analyzed. There was no strain with characteristic mutation for resistance to neuraminidase inhibitors, per contra; all strains possessed the substitution S31N, peculiar of resistance to adamantanes. There was drift in influenza A(H3N2) dominant epitopes B (2014 and 2015) to epitopes A (2016) with a theoretical efficiency in vaccine ranging from low to moderate. The presence of several antigenic site mutations among H3N2 virus strains between 2014–2016 influenza seasons in Cameroon confirms the progressing evolution of circulating H3N2 strains.

Prescribing patterns and associated factors of antibiotic prescription in primary health care facilities of Kumbo East and Kumbo West Health Districts, North West Cameroon

Background Inappropriate use of antibiotics is a global public health challenge and has been associated with antibiotic resistance. WHO reports show that efforts to promote rational antibiotic use in developing countries are poor. With the growing number of infections with antibiotic resistant bacteria, rational drug use becomes imperative and studies that promote rational drug use are highly necessary. Considering this, we investigated prescribing patterns and predictors of antibiotic prescription in primary health care facilities in Kumbo East (KE) and Kumbo West (KW) health districts in North West Cameroon, to contribute data which could influence policy on antibiotic use. Methods and findings A cross sectional retrospective study was conducted from April 2014 to April 2015 in 26 randomly selected primary care facilities. Questionnaires were administered to 59 antibiotic prescribers to determine factors that predict antibiotic prescribing. Data on antibiotic prescription were collected by review of consultation registers. Prescription rates and demographics, prescriber and institution factors were analyzed using ANOVA. The best predictor of prescription was determined using multiple linear regression analysis. Results A total of 30,096 prescriptions were reviewed. Overall antibiotic prescription rate was 36.71%, with a mean of 1.14 antibiotics prescribed per patient. Amoxicillin was the most prescribed (29.9%). The most prevalent indications for prescribing were respiratory tract infections (21.27%). All antibiotics prescribed were broad-spectrum. Antibiotics were prescribed for patients with malaria and also in situations where diagnosis was uncertain. Prescribing by generic name was 98.36% while 99.87% was from Essential Drug List. Use of laboratory results, patient turnout and Performance Based Financing (PBF) were significantly associated with antibiotic prescribing rates (p < 0.05). PBF moderated prescribing. Conclusion There was misuse of antibiotics in primary care facilities in study area. We recommend all primary care health facilities in study area to be included in the PBF scheme and that prescribing should only be done by physicians as the have adequate training.

Vaccine uptake and immune responses to HBV infection amongst vaccinated and non-vaccinated healthcare workers, household and sexual contacts to chronically infected HBV individuals in the South West Region of Cameroon

Background HBV infection affects about 257 million people globally and Sub-Saharan Africa has the highest burden. The disease still constitutes a major public health problem despite the advent of preventive measures like the HBV vaccine. This study was aimed at identifying factors that influence vaccine uptake and the efficacy of administered vaccines among people at high risk of HBV infection. Methods This was a cross-sectional study conducted between January 2016 and December 2017. A pretested semi-structured questionnaire was used to capture information on sociodemographic and vaccination status from healthcare workers, household and sexual contacts to HBV infected people. HBV serological panel as well as quantitative anti-HBs ELISA test was done for all participants. Additional information was obtained from the institutions that administered the vaccines. Results A total of 265 participants with a mean age of 32.1±8.7 were enrolled. Eighty (30.2%) of them had received at least 1 dose of the HBV vaccine while 185 (69.8%) were unvaccinated. Healthcare workers were the most vaccinated (37%). Ignorance, negligence, fear of injection and the cost of the vaccine all contributed to poor vaccine uptake in the study population. Natural immunity was seen in 9 (3.4%) of the participants. Only 64.9% of the vaccinated participants attained the desirable level of anti-HBs (≥10mIU/ml) 1–2 months after ≥ 3 doses of the vaccine. Age, gender, obesity, alcohol and smoking were not significantly associated with poor immune responses. No standardized protocol was followed by the institutions administering the vaccine. Conclusion This study revealed very poor vaccine uptake and poor immune responses to the HBV vaccine in the study population and this should urge the health sector in Cameroon to intensify their sensitization on HBV vaccine, standardize the protocol for storing and administering the vaccine, subsidize the cost of the vaccine especially amongst healthcare workers and encourage anti-HBs post vaccination testing.

Genetic characterization of influenza B virus in Cameroon and high frequency of reassortant strains: MONAMELE et al.

Influenza B is broadly divided into B/Victoria and B/Yamagata lineages based on its genetic and antigenic properties. We describe in this study the first report on genome characterization of type B influenza virus in the Cameroon National Influenza Center (NIC) between 2014 and 2017. Respiratory samples were collected as part of the influenza surveillance activity in the NIC. RNA products were tested for the presence of influenza using the CDC Influenza A/B typing panel. Thirty‐five samples positive for influenza B were selected for sequencing three gene segments (HA, NA, and M) and phylogenetic trees were generated by MEGA version 6.0. Nucleotide phylogenetic analysis of the HA gene revealed the presence of three major clades among Cameroonian strains. All Victoria lineages grouped into B/Victoria clade 1A, while, Yamagata lineages grouped into Yamagata clade 2 (2014 strains) and Yamagata clade 3 (2015‐2017). We observed a high frequency of reassortant viruses with Yamagata‐like HA gene and Victoria‐like NA gene (27.4%; 23/84). The results from this study confirm variations in the genome composition of type B influenza virus and emphasize on the relevance of molecular surveillance for spotting peculiar genetic variants of public health and clinical significance.

Drug Resistant Non-acid Fast Bacteria Pathogens, Isolated from Tuberculosis (TB) Patients with Known HIV Status from the North West Region of Cameroon

Aims: To investigate the prevalence of Non-Mycobacterium tuberculosis (MTB) bacterial pathogens from TB patients with known HIV status as well as their resistant patterns to commonly used antibiotics. Study Design: This was a cross sectional laboratory based study. Original Research Article

Prevalence and Risk of Active Tuberculosis among Symptomatic Household Contacts of Bacteriologically Confirmed Pulmonary Tuberculosis Subjects Treated at the Buea Regional Hospital of the Southwest Region of Cameroon

Background: Tuberculosis (TB) remains a serious public health concern worldwide. The predominant global strategy for identifying people with TB is ‘passive case detection’ which has a low case detection rate therefore is an obstacle to the long-term success of TB control programs, giving the possibility of undiagnosed patients posing great risk of transmitting the infection to others. Methods: A hospital/community-based cross-sectional study was conducted on 921 clinically suspected consented TB patients and those confirmed by microscopy of Ziehl Neelsen stain for Acid fast bacilli (AFB) were contacted at their residence so as to identify any household contacts (HHC) with symptoms of TB. AFB Smear negative cases were further investigated using sodium hypochlorite (NaOCl) centrifuge-concentrated smears technique. Data was collected from participants and the results were summarized using descriptive statistics, bivariate and multivariate logistic regression analyses. Results: The prevalence of pulmonary TB was 20.6% (190/921) and 7.04% (5/71) among TB suspected cases and symptomatic HHC respectively. In a univariate analysis, age group (p = 0.011), marital status (p = 0.019), employment status (p = 0.041), previous TB contact (p 5 persons, previous contact with TB patients, marital and HIV status were associated with TB prevalence. Concentration technique is more effective with a higher rate of detection compared to direct smear.