Genetic Diversity and Protective Efficacy of the RTS,S/AS01 Malaria Vaccine.

BACKGROUND: The RTS,S/AS01 vaccine targets the circumsporozoite protein of Plasmodium falciparum and has partial protective efficacy against clinical and severe malaria disease in infants and children. We investigated whether the vaccine efficacy was specific to certain parasite genotypes at the circumsporozoite protein locus. METHODS: We used polymerase chain reaction-based next-generation sequencing of DNA extracted from samples from 4985 participants to survey circumsporozoite protein polymorphisms. We evaluated the effect that polymorphic positions and haplotypic regions within the circumsporozoite protein had on vaccine efficacy against first episodes of clinical malaria within 1 year after vaccination. RESULTS: In the per-protocol group of 4577 RTS,S/AS01-vaccinated participants and 2335 control-vaccinated participants who were 5 to 17 months of age, the 1-year cumulative vaccine efficacy was 50.3% (95% confidence interval [CI], 34.6 to 62.3) against clinical malaria in which parasites matched the vaccine in the entire circumsporozoite protein C-terminal (139 infections), as compared with 33.4% (95% CI, 29.3 to 37.2) against mismatched malaria (1951 infections) (P=0.04 for differential vaccine efficacy). The vaccine efficacy based on the hazard ratio was 62.7% (95% CI, 51.6 to 71.3) against matched infections versus 54.2% (95% CI, 49.9 to 58.1) against mismatched infections (P=0.06). In the group of infants 6 to 12 weeks of age, there was no evidence of differential allele-specific vaccine efficacy. CONCLUSIONS: These results suggest that among children 5 to 17 months of age, the RTS,S vaccine has greater activity against malaria parasites with the matched circumsporozoite protein allele than against mismatched malaria. The overall vaccine efficacy in this age category will depend on the proportion of matched alleles in the local parasite population; in this trial, less than 10% of parasites had matched alleles. (Funded by the National Institutes of Health and others.).

The effects of a tsetse DNA virus infection on the functions of the male accessory reproductive gland in the host fly Glossina morsitans centralis (Diptera; Glossinidae).

Freshly deposited third instar Glossina morsitans centralis larvae were infected with the tsetse DNA virus by microinjection, and at emergence adult males were separated from the females and fed on rabbit blood every second day for 8 days. A control group treated with sterile saline were handled similarly. They were dissected, and comparative observations made on the appearance and size of the accessory reproductive glands (ARG) in infected and control males. Regularly fed 8-day-old males from infected and control groups were mated to 2-day-old normal females obtained from the insectay. After separation from copula, the females were dissected and the uteri examined for the presence and quality of the spermatophore. The spermathecae were also examined for insemination. ARG tissues from the control and virus infected regularly fed 8-day-old male flies were fixed and processed for electron microscopic studies. The ARGs from control flies were found to be milky in appearance, whereas those from virus-infected flies were transparent in most parts. The ARGs from virus-infected males were significantly smaller in diameters (F = 42.26, p < 0.0001) and shorter (F = 200.4, p < 0. 0001) than those of the controls. Most of the virus-infected males failed to form a complete spermatophore, whereas almost all the controls formed complete spermatophore as observed in the uteri of the female mates (Chi2 = 111.661, p < 0.0001). The infected males that formed partial spermatophores and those that did not form any at all failed to inseminate their female mates. Histological studies of the ARGs revealed some lesions in the epithelial cells characterized by degeneration of cytoplasmic organelles and detachment of the muscle layer from the basal plasma membrane. However, no virus particles were observed in the affected cells.

Some effects of the rising case load of adult HIV-related disease on a hospital in Nairobi.

Increasing numbers of HIV-infected adults in Africa need hospital care. It remains unclear what impact this has on health care services or on how hospitals respond. The aim of this study was to describe the effects of a rising case load of adult HIV-related disease by comparing results from a prospective cross-sectional study of acute adult medical admissions to a government hospital in Nairobi conducted in 1992 with results from a previous study done in 1988 and 1989 in the same hospital, using the same study design and protocol. Data on age, gender, number admitted, length of stay, HIV status, clinical AIDS, final diagnosis, case mix, and outcome were compared. In 1992, 374 consecutive patients were admitted in 15 24-hour periods (24.9 patients/period) compared with the 1988 to 1989 study, which enrolled 506 patients in 22 24-hour periods (23.0 patients/period). Patients' age, gender, and length of hospital stay were similar in both studies. In 1992, 39% of patients were HIV-positive compared with 19% in 1988 to 1989 (p < 10(-6)); whereas seropositive admissions rose 123% between the two periods (p < .0001), HIV-negative admissions declined 18% (p < .05). Clinical surveillance for AIDS consistently identified <40% of HIV-positive patients. Irrespective of HIV status, tuberculosis and pneumococcal pneumonia were the leading diagnoses in both surveys. No change was found in the diagnoses recorded for HIV-positive patients, but in HIV-negative patients, reductions were significant in the case mix (p < .00001) and range of diagnoses (p < .001) seen in 1992. Outcome remained unchanged for HIV-positive patients with approximately 35% mortality in both surveys. Outcome significantly worsened, in relative and absolute terms, for HIV-negative patients: in 1992, mortality was 23%, compared with 13.9% in 1988 to 1989 (p < .005), with 3.5 deaths per 24-hour period in 1992 compared with 2.6 deaths per 24-hour period in 1988 to 1989 (p < .05, one-tailed). These data suggest that increasing selection for admission is taking place as demand for care increases because of HIV/AIDS. This process appears to favor HIV-positive patients at the expense of HIV-negative patients who seem to be crowded out and, once admitted, experience higher mortality rates. The true social costs of the HIV epidemic are underestimated by not including the effects on HIV-negative people.

PIP: The impact of the escalating demand for HIV/AIDS-related care on hospital services in Nairobi, Kenya, was investigated in two prospective cross-sectional studies conducted at Kenyatta National Hospital. Data on age, gender, number of admissions, length of stay, HIV status, clinical AIDS, final diagnosis, case mix, and outcome were compared in a 1988-89 study that enrolled 506 consecutive patients in a total of 22 24-hour periods and in a 1992 study of 374 patients admitted in 15 24-hour periods. 18.7% of hospital patients in 1988-89 were HIV-positive compared with 38.5% in 1992, with a concomitant decline of 18% in the number of HIV-negative admissions. Clinical surveillance for AIDS consistently identified less than 40% of HIV-positive patients. Tuberculosis and pneumococcal pneumonia were the leading diagnoses in both surveys among HIV-positive and HIV-negative patients. Diagnoses recorded for HIV-positive patients did not change over time; however, among HIV-negative patients, there was a significant narrowing in the range of diagnoses seen. Mortality among HIV-positive patients remained constant at 35% in both surveys. Among HIV-negative patients, mortality increased from 13.9% in 1988-89 to 23% in 1992 (2.6 and 3.5 deaths per 24-hour period, respectively). These findings suggest that increasing demand for hospital care by HIV-positive patients has been accompanied by deteriorating conditions for HIV-negative patients, especially an admissions selection process that favors HIV/AIDS patients. Recommended to address the worsening crisis in health care delivery are general guidelines on admission criteria that neither crowd out HIV-negative patients nor discriminate against those with HIV/AIDS.

Urinary tract stone disease in Nairobi.

At the Kenyatta National Hospital (KNH) and other private hospitals in Nairobi urinary stone disease is not being correctly diagnosed. Over a 15 year period (1980-1995) only 56 patients have been confirmed to have urinary tract stones out of the expected number of 220 patients. The age range was 10-60 years. The peak age was 30-40 years. Pain and haematuria were the commonest presenting symptoms. Ultrasonography and plane abdominal radiology were the commonest methods of diagnosis. Open surgery and endoscopic stone removal were the commonest modes of management. Extracorporeal shortwave lithotripsy (ESWL) has recently been introduced into the Nairobi Hospital, but was not functional at the time of this study. Percutaneous nephrolithotomy (PCNL) is possible but has not been adequately used due to lack of correct equipment. Septicaemia and haemorrhage were the commonest complications of the open surgery.

The effects of a DNA virus infection on the reproductive potential of female tsetse flies, Glossina morsitans centralis and Glossina morsitans morsitans (Diptera: Glossinidae).

Reproductive anomalies associated with the tsetse DNA virus infection in the female tsetse hosts, Glossina morsitans centralis Machado and Glossina morsitans morsitans Westwood, inoculated with the virus during the 3rd instar larval stage were studied and the data compared to those obtained from the control females injected with sterile physiological saline. Virus infected flies had significantly longer first and second pregnancy cycles (P < 0.0001) and produced pupae that were of significantly less weight in milligrams (P < 0.0001) compared to controls. Transmission of the virus to progeny was not absolute and only 21% of G. m. centralis and 48% of G. m. morsitans first progeny flies from infected females developed salivary gland hypertrophy as a result of transmission from mother to progeny. The virus infected females produced significantly fewere pupae compared to the controls during the experimental period (P < 0.00001).

No increased prevalence of adrenocortical insufficiency in human immunodeficiency virus-associated tuberculosis.

SETTING: Acute medical wards, Kenyatta National Hospital, Nairobi, Kenya. OBJECTIVE: To determine the prevalence of adrenocortical insufficiency in human immunodeficiency virus (HIV)-1 infected and non-infected patients with tuberculosis. DESIGN: One hundred and seventy-four patients with proven tuberculosis (90 HIV-1 positive and 84 HIV-1 negative) were assessed for adrenocortical insufficiency with a 30 min synacthen stimulation test. RESULTS: Fifty-one percent of those with pulmonary tuberculosis and 56% of those with extra-pulmonary tuberculosis had a subnormal cortisol response. However there was no statistically significant difference between the HIV-1 infected and non-infected patients in either group. CONCLUSION: While an impaired cortisol response is common in tuberculosis, it is no more prevalent in HIV-1 infected patients than non-infected patients with tuberculosis.

Asymptomatic bacteriuria among diabetics attending Kenyatta National Hospital.

Significant asymptomatic bacteriuria is an important cause of pyelonephritis and gram negative septicaemia among certain predisposed individuals, such as diabetics. We investigated the incidence of asymptomatic urinary tract infections (UTIs) among our diabetic patients and the type and antibacterial sensitivity patterns of the organisms causing these UTIs. One hundred and thirty five patients submitted midstream urine specimens for culture. Fifteen patients had positive cultures showing the incidence of asymptomatic UTI to be 11.1%. There were ten female and five male patients with UTI. The commonest organism isolated was Escherichia coli at 40%. Gram negative bacilli made up 66.7% of the isolates. Isolates were poorly sensitive to the regularly available antibiotics-ampicillin (33% sensitive, cotrimoxazole (33% sensitive). Nitrofurantoin inhibited growth in 93% of the isolates. Other antimicrobials with over 80% sensitivity level included: gentamicin, ceftazidime, augmentin, cefuroxime and norfloxacin. They are expensive or require parenteral administration. The incidence of asymptomatic UTI is high among diabetics and although the organisms isolated are those usually isolated in UTIs, they are not that sensitive to the commonly available and antibacterial agents.

Relationships between host blood factors and proteases in Glossina morsitans subspecies infected with Trypanosoma congolense.

Host blood effects on Trypanosoma congolense establishment in Glossina morsitans morsitans and Glossina morsitans centralis were investigated using goat, rabbit, cow and rhinoceros blood. Meals containing goat erythrocytes facilitated infection in G.m.morsitans, whereas meals containing goat plasma facilitated infection in G.m.centralis. Goat blood effects were not observed in the presence of complementary rabbit blood components. N-acetyl-glucosamine (a midgut-lectin inhibitor) increased infection rates in some, but not all, blood manipulations. Cholesterol increased infection rates in G.m.centralis only. Both compounds together added to cow blood produced superinfection in G.m.centralis, but not in G.m.morsitans. Midgut protease levels did not differ 6 days post-infection in flies maintaining infections versus flies clearing infections. Protease levels were weakly correlated with patterns of infection, but only in G.m.morsitans. These results suggest that physiological mechanisms responsible for variation in infection rates are only superficially similar in these closely-related tsetse.

Detection of trypanosome infections in the saliva of tsetse flies and buffy-coat samples from antigenaemic but aparasitaemic cattle.

Relatively simple protocols employing non-radioactive DNA probes have been used for the detection of African trypanosomes in the blood of mammalian hosts and the saliva of live tsetse flies. In combination with the polymerase chain reaction (PCR), the protocols revealed trypanosomes in buffy-coat samples from antigenaemic but aparasitaemic cattle and in the saliva of live, infected tsetse flies. Furthermore, the protocols were used to demonstrate concurrent natural infections of single tsetse flies with different species of African trypanosomes.

Dynamics of host blood effects in Glossina morsitans sspp. infected with Trypanosoma congolense and T. brucei.

The pattern of infection in Glossina morsitans morsitans and G. m. centralis membrane-fed on eland, buffalo or goat blood mixed with Trypanosoma congolense or T. brucei was studied from day 1 to day 10. Tsetse were initially permissive vectors, with most flies harbouring infections of 10(4)-10(5) parasites on day 3. However, after a second blood meal on day 3, flies cleared many infections, with G. m. morsitans clearing more infections than G.m. centralis. Infective feeds of goat blood consistently increased final infection rates by limiting the number of infections lost between days 3 and 6. In further experiments with G. m. morsitans only, this effect was replicated by feeding flies on erythrocytes but not on serum. These results suggest that compounds from some mammalian erythrocytes match the target specificity of G. m. morsitans midgut lectins and, hence, have a protective effect on trypanosome establishment in the fly.

Surgical aspects of live donor kidney transplants in Kenya.

Review of twenty cases of live-donor kidney transplants in Kenya for a period of 5 years (1985-1989) and the follow up study results revealed that there were both high graft losses, high morbidity and mortality due to various complications pertaining to surgery and immunosuppression. The most serious complications were intercurrent infections, acute or chronic rejection, pulmonary embolism, steroid induced diabetes, pneumonia, and myocardial infarction. At the end of the first year follow up, there were only twelve graft patients alive. Magnetic Resonance Imaging (MRI) was not available for assessing the anatomical and functional behaviour of the transplanted kidneys. This would have assisted in early diagnosis of the degree and onset of rejection for appropriate treatment before the death of the allografts. It would also assist in differentiating perfusional problems from rejection.

The spectrum of echocardiographic findings in chronic renal failure.

In a six month period at the Kenyatta National Hospital, 46 patients (30 males) with chronic renal failure (CRF) and 22 healthy subjects have had a clinical and echocardiographic study of their cardiovascular systems. The patients with CRF were further classified as stable or in end stage renal disease (ESRD), the latter group requiring dialysis. Hypertension and circulatory congestion were the commonest clinical cardiovascular findings in patients with CRF. The patients with ESRD had significantly higher blood urea nitrogen and serum creatinine than the ones with stable CRF. Echocardiographically right ventricular size, left atrial size, aortic root diameter, left ventricular internal diameters, left ventricular end diastolic and systolic volumes, stroke volume, cardiac output, left ventricular posterior wall and interventricular septal thickness, ejection time and mitral and aortic peak flow rates were significantly higher in patients with CRF than in controls. In contrast, the circumferential fibre shortening and the ejection fraction were reduced in patients with CRF. Global left ventricular dysfunction was found in 47.8% of the patients. Using doppler flow studies, valvular incompetence was detected in a number of patients, mitral regurgitation being found in 84%.76% of the patients with CRF had varying degrees of pericardial effusion. The echocardiographic abnormalities and the pericardial effusions responded six weeks of haemodialysis in a variable manner.

Bacteriuria in patients with glomerular diseases.

In a comparative study of significant bacteriuria in an African population, 1.7% of 697 healthy subjects (10 females and 2 males) were found to have positive urine cultures. Of these, 5 subjects grew E. coli, 4 Klebsiella strains, 2 Staphylococcus aureus and 1 Serratia marcescens. Among 116 patients with glomerular disease, 15.5% (7 males and 11 females) yielded positive cultures. E. coli, Staph. aureus and Proteus species were commonly isolated organisms. There was a nine fold increase in prevalence of bacteriuria in patients with glomerular disease and in females, this correlated with the amount of protein lost per 24 hours. It is postulated that the presence of protein in urine per se favours bacterial growth and because of the high prevalence of bacteriuria in patients with glomerular disease, it is recommended that all such patients should be screened and treated appropriately.

Influence of D(+)-glucosamine on infection rates and parasite loads in tsetse flies (Glossina spp.) infected with Trypanosoma brucei.

Teneral Glossina morsitans centralis, G. m. morsitans and G. pallidipes were infected with three different clones of Trypanosoma brucei in blood containing D(+)-glucosamine, an inhibitor of tsetse midgut lectin. On average, 5 days of D(+)-glucosamine treatment tripled infection rates, without affecting the proportion of infections that matured. Total infection rates were equal in males and females, but twice as many infections matured in males. Counts of parasites in the guts and salivary glands of 277 flies revealed order of magnitude differences among flies, with females consistently having 2-3-times as many parasites as males. Parasite numbers varied in a sex-specific manner among tsetse-clone combinations, but these differences were not correlated with similar large differences in infection rates. D(+)-glucosamine treatment had no significant effect on parasite loads.

Thyroid hormone profiles in patients with chronic renal failure on conservative management and regular haemodialysis.

Patients with chronic non-thyroid illness (NTI) generally show biochemical features of hypothyroidism despite their being clinically euthyroid. Using assays that employ the antibody coated tubes technique, we measured thyroid hormone levels in 52 patients with chronic renal failure. 30 of the patients were on conservative management while 22 were on regular haemodialysis (HD) for a mean period of 14.2 +/- 9.9 months. The findings were compared to those of 14 healthy controls. All patients were clinically euthyroid. Only 3 patients on HD had goitres. The mean value of total thyroxine (TT4) total triiodo thyronine (TT3), free thyroxine (FT4) and the free triiodothyronine (FT3) were low in patients compared with controls (P less than 0.01). The mean basal thyroid stimulating hormone (TSH) levels were significantly higher in patients than in controls (P less than 0.001). There were no significant differences in all parameters between the patients on conservative management and those on haemodialysis (P greater than 0.05). Although all patients were clinically euthyroid, the biochemical features suggest hypothyroidism.

Pregnancy in a patient on continuous ambulatory peritoneal dialysis (CAPD): a case report.

We present what we believe is the first case of pregnancy occurring in a patient on CAPD, and indeed end stage renal disease (ESRD), in Kenya. Pregnancy progressed very well until the thirtieth week when foetal movements and heart sounds were noted to be absent and this was confirmed by sonography. A macerated still birth was delivered per vagina following induction of labour. We review the literature on this rare occurrence and discuss the possible causes of the unpleasant outcome in our patient.

Acute renal failure as seen at Kenyatta National Hospital.

Forty seven patients with acute renal failure were studied prospectively over a two-year period at the Kenyatta National Hospital. There were 20 males and 27 females. The mortality rate was 40.4%. Most patients had medically oriented problems. Complications that were associated with a high mortality were infections and the presence of neuropsychiatric manifestations.