Browsing by Author "Liswaniso F"

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Comparative analysis of cholera serum vibriocidal antibodies from Convalescent and vaccinated adults in Zambia.
(2024-Aug-13) Ng'ombe H; Bosomprah S; Phiri B; Muchimba M; Liswaniso F; Chibuye M; Luchen CC; Chibesa K; Musukuma-Chifulo K; Mwape K; Tigere S; Silwamba S; Sinkala A; Simuyandi M; Mbewe N; Kapaya F; Cunningham AF; Chilengi R; Sack D; Chisenga CC
Cholera is responsible for 1.3 to 4.0 million cholera cases globally and poses a significant threat, with Zambia reporting 17,169 cases as of 4th February 2024. Recognizing the crucial link between natural cholera infections and vaccine protection, this study aimed to assess immune responses post cholera infection and vaccination. This was a comparative study consisting of 50 participants enrolled during a cholera outbreak in Zambia's Eastern Province and an additional 56 participants who received oral cholera vaccinations in Zambia's Central Province. Vibriocidal antibodies were plotted as geometric mean titres in the naturally infected and vaccinated individuals. A significant difference (p < 0.047) emerged when comparing naturally infected to fully vaccinated individuals (2 doses) on day 28 against V. cholerae Ogawa. Those who received two doses of the oral cholera vaccine had higher antibody titres than those who were naturally infected. Notably, the lowest titres occurred between 0-9 days post onset, contrasting with peak responses at 10-19 days. This study addresses a critical knowledge gap in understanding cholera immunity dynamics, emphasizing the potential superiority of vaccination-induced immune responses. We recommend post infection vaccination after 40 days for sustained immunity and prolonged protection, especially in cholera hotspots.
Diagnostic accuracy of saliva-based testing as a Vibrio cholerae surveillance tool among naturally infected patients.
(2025-Jan-21) Chisenga CC; Phiri B; Ng'ombe H; Muchimba M; Liswaniso F; Bernshtein B; Cunningham AF; Sack D; Bosomprah S
Saliva, as a diagnostic medium, offers a promising alternative to blood by virtue of its non-invasive collection, which enhances patient compliance, especially in paediatric and geriatric populations. In this study, we assessed the utility of saliva as a non-invasive medium for measuring Vibrio cholerae-specific serum antibodies in naturally infected individuals. We tested paired serum and saliva samples obtained from a total of 63 patients with cholera enrolled in a cohort study. Vibriocidal antibodies assay (IgM/IgG) as markers for accurate determination was used to determine cholera-specific antibody levels. Using receiver operating characteristics (ROC) curve, we found that the best cut-off that maximizes (sensitivity + specificity) is 10 titres. At this saliva titre, the sensitivity is 76.9% (95%CI: 60.9%, 87.7%) and specificity is 80.0% (95%CI: 56.6%, 92.5%). Using Spearman's correlation coefficient, we also found evidence of a positive correlation between V. cholerae saliva and serum antibodies (rho = 0.66, P < 0.001). In conclusion, saliva-based diagnostic cholera tests have high diagnostic accuracy and would be advantageous, cheaper, and quicker for early diagnosis of severe cholera outcomes.
Field evaluation of a novel, rapid diagnostic assay, and molecular epidemiology of enterotoxigenic E. coli among Zambian children presenting with diarrhea.
(2022-Aug) Silwamba S; Chilyabanyama ON; Liswaniso F; Chisenga CC; Chilengi R; Dougan G; Kwenda G; Chakraborty S; Simuyandi M
BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) is one of the top aetiologic agents of diarrhea in children under the age of 5 in low-middle income countries (LMICs). The lack of point of care diagnostic tools for routine ETEC diagnosis results in limited data regarding the actual burden and epidemiology in the endemic areas. We evaluated performance of the novel Rapid LAMP based Diagnostic Test (RLDT) for detection of ETEC in stool as a point of care diagnostic assay in a resource-limited setting. METHODS: We conducted a cross-sectional study of 324 randomly selected stool samples from children under 5 presenting with moderate to severe diarrhea (MSD). The samples were collected between November 2012 to September 2013 at selected health facilities in Zambia. The RLDT was evaluated by targeting three ETEC toxin genes [heat labile toxin (LT) and heat stable toxins (STh and STp)]. Quantitative PCR was used as the "gold standard" to evaluate the diagnostic sensitivity and specificity of RLDT for detection of ETEC. We additionally described the prevalence and seasonality of ETEC. RESULTS: The study included 324 participants, 50.6% of which were female. The overall prevalence of ETEC was 19.8% by qPCR and 19.4% by RLDT. The children between 12 to 59 months had the highest prevalence of 22%. The study determined ETEC toxin distribution was LT 28/321(9%), ST 18/321(6%) and LT/ST 16/321(5%). The sensitivity and specificity of the RLDT compared to qPCR using a Ct 35 as the cut-off, were 90.7% and 97.5% for LT, 85.2% and 99.3% for STh and 100% and 99.7% for STp, respectively. CONCLUSION: The results of this study suggest that RLDT is sufficiently sensitive and specific and easy to implement in the endemic countries. Being rapid and simple, the RLDT also presents as an attractive tool for point-of-care testing at the health facilities and laboratories in the resource-limited settings.
Prevalence of Diarrhoeagenic
(2023-Nov-17) Mwape K; Bosomprah S; Chibesa K; Silwamba S; Luchen CC; Sukwa N; Mubanga C; Phiri B; Chibuye M; Liswaniso F; Somwe P; Chilyabanyama O; Chisenga CC; Muyoyeta M; Simuyandi M; Barnard TG; Chilengi R
Diarrhoea is a major contributor to childhood morbidity and mortality in developing countries, with diarrhoeagenic
Seroconversion and Kinetics of Vibriocidal Antibodies during the First 90 Days of Re-Vaccination with Oral Cholera Vaccine in an Endemic Population.
(2024-Apr-08) Chisenga CC; Phiri B; Ng'ombe H; Muchimba M; Musukuma-Chifulo K; Silwamba S; Laban NM; Luchen C; Liswaniso F; Chibesa K; Mubanga C; Mwape K; Simuyandi M; Cunningham AF; Sack D; Bosomprah S
Despite the successful introduction of oral cholera vaccines, Zambia continues to experience multiple, sporadic, and protracted cholera outbreaks in various parts of the country. While vaccines have been useful in staying the cholera outbreaks, the ideal window for re-vaccinating individuals resident in cholera hotspot areas remains unclear. Using a prospective cohort study design, 225 individuals were enrolled and re-vaccinated with two doses of Shanchol™, regardless of previous vaccination, and followed-up for 90 days. Bloods were collected at baseline before re-vaccination, at day 14 prior to second dosing, and subsequently on days 28, 60, and 90. Vibriocidal assay was performed on samples collected at all five time points. Our results showed that anti-LPS and vibriocidal antibody titers increased at day 14 after re-vaccination and decreased gradually at 28, 60, and 90 days across all the groups. Seroconversion rates were generally comparable in all treatment arms. We therefore conclude that vibriocidal antibody titers generated in response to re-vaccination still wane quickly, irrespective of previous vaccination status. However, despite the observed decline, the levels of vibriocidal antibodies remained elevated over baseline values across all groups, an important aspect for Zambia where there is no empirical evidence as to the ideal time for re-vaccination.
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(2025) Luchen CC; Ngo'mbe H; Liswaniso F; Bosomprah S; Zhiteneva JA; Harris J; Charles RC; Ryan ET; Sack D; Bernshtein B; Chisenga CC
BACKGROUND: Cholera is a public health threat in resource-limited settings and is responsible for causing over 3 million cases globally. Mucosal immune responses play an important role in protecting against METHODS: We conducted a cross-sectional antibody profiling study to analyse cholera-specific antibodies in saliva and plasma samples from 74 participants upon presenting to the cholera treatment centres. These were collected from four treatment centres in Lusaka during Zambia's most severe cholera outbreak in 2024 caused by RESULTS: Saliva and plasma antibody profiles were comparable, with elevated IgA1 and IgA2 responses to cholera toxin-B (CtxB), sialidase, HlyA, and TcpA in saliva. Broader systemic responses were seen in plasma, including high CtxB-specific IgM, IgA1, and total IgG levels. Notably, biomarkers such as HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase exhibited significant positive correlations between plasma and saliva. Elevated biomarker levels of HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase in people living with HIV/AIDS (PLWHA) suggested immunological differences that warrant further exploration. CONCLUSION: We demonstrate that saliva is a viable, non-invasive alternative for cholera antibody-based profiling, offering practical advantages in resource-constrained settings. Given its strong correlation with systemic antibody profiles, saliva may be a practical sample for sero-surveillance in resource-limited settings. Future studies should investigate the duration of these salivary responses to further substantiate their use in estimating disease burden and immunity.