Efficacy of Hexetidine, Thymol and Hydrogen Peroxide-Containing Oral Antiseptics in Reducing Sars-Cov-2 Virus in the Oral Cavity: A Pilot Study

BACKGROUND

Studies have demonstrated the role of sputum as a site of severe acute respiratory syndrome-coronavirus-2 (SARSCoV-2) transmission. However, there is limited literature on the virucidal efficacy of oral antiseptics against SARS-CoV-2 virus. This study investigated the virucidal efficacy of three oral-antiseptics compared to a placebo-control in the sputum of SARS-CoV-2 infected individuals.

METHODOLOGY

A pilot study of adults with SARS-CoV-2 positive results, as determined by reverse transcription-polymerase chain reaction (RT-PCR) of <7 days. The oral antiseptics investigated were: Hexetidine (0.1% w/v); Thymol (0.063% w/v) and H2O2(1.5%) compared to de-mineralized sterile water (Placebo-control). The primary outcome measure was the proportion of negative RT-PCR results at 15-mins, 30-mins, 1-hour, 2-hours and 4-hours After Oral antiseptics Interventions (AOI) compared to the placebo-control. Statistical analysis was done using STATA 15.0 software with p-values of <0.05 considered statistically significant.

RESULTS

Data from a total of 66 participants that were RT-PCR SARS-CoV-2 positive at baseline (0-min) was analysed. At 15-mins AOI, the highest proportion of negativation from sputum samples was observed in the Hexedine group, with 69.2% of the baseline PCR positive cases converting to negative compared to 46.7% in the placebo-control group. In addition, H2O2 demonstrated efficacy at 2-hours AOI compared to placebo-control (62.5% vs 37.5% respectively) and other oral-antiseptics. Across all time-points, the oral-antiseptic groups compared to the placebo-control group, there was no statistically significant difference in the proportion of sputum samples which converted to a negative status (p>0.05).

CONCLUSION

The findings in this study suggest there was no significant difference in the proportion of participants who converted to a negative sputum status across the treatment groups at various time points. Future studies could compare the cycle threshold (ct) viral titre values of sputum samples to determine quantitative differences.

Seizure severity and health-related quality of life of adult Nigerian patients with epilepsy

OBJECTIVES

There is paucity of information about the association of seizure severity and quality of life in people with epilepsy (PWE) in sub-Saharan Africa. We evaluated the relationship of seizure severity to health-related quality of life of patients with epilepsy being followed up in an outpatient neurology clinic in southwestern Nigeria.

MATERIALS AND METHODS

Eighty-eight consecutive patients with epilepsy who met the recruitment criteria completed the study questionnaire in company of an eyewitness. The study questionnaire comprised of the National Hospital Seizure Severity Scale (NHS3), the Quality of Life Inventory in Epilepsy (QOLIE-31), and the Beck's Depression Inventory-II (BDI-II).

RESULTS

We found a minute association between seizure severity and QOLIE-31 total score (r = -0.262, P = 0.014). Increased seizure severity predicted a worse QOLIE-31 seizure worry (R(2) = 0.311, β = -0.289; P = 0.003). Of the seven seizure severity items, generalization of seizures and presence of falls were items that predicted a worse QOLIE-31 seizure worry score and time to recover predicted a worse QOLIE-31 total score.

CONCLUSIONS

Reducing seizure severity may be an alternate endpoint in epilepsy care in Nigeria (particularly difficult to control seizures) because of its practical clinical relevance in view of the fact that state-of-the-art epilepsy care is still farfetched.

Selenium and aspirin in people living with HIV and AIDS in Nigeria

OBJECTIVES

Aspirin and selenium have been shown in vitro and in vivo to inhibit HIV production through inhibition of the transcription factor, the nuclear factor kappa binding (NF-eB). The aim of this study was to examine the efficacy or otherwise of these drugs in people living with HIV and AIDS (PLWAS) in resource limited countries.

PATIENTS AND METHODS

Consenting HAART-naive PLWAS with mean CD4 count of 256.8 +/- 67.6 cells/ul were recruited into the study. Pretherapy blood count, serum biochemistry, chest x-ray, urinary glucose and protein and microscopy and culture of both urine and stool were checked in all cases. Each patient was treated for six months and CD4 counts were repeated at the end of the study. Thirty two patients (23 (72%) females and nine (28%) males), aged 22-52 (median = 36) years were recruited. Twenty-three (72%) were randomised into selenium and aspirin (SAM) and nine (28%) into selenium (SM); multivitamin was added to each arm.

RESULTS

Eighteen (56.2%) patients completed the study. Sixteen (88.9%) patients are already on HAART since the termination of the study; one absconded and one died of disease progression. Fourteen (43.8%) of the initial 32 patients dropped out (11 (78.6%) were lost to follow-up, two (14.3%) died and one (7.1%) opted for HAART before completing the study). The post-treatment CD4 count was 293.0 +/-102.2 cells/ml, compared to the pre-therapy mean of 256.8 +/- 67.6 cells/ul, an average rise of 36.2 cells/ul, the difference was not statistically significant (p = 0.059). The post-therapy mean weight was significantly higher than the pretherapy weight, 61.6+/-15.2 kg versus 60.0+/-14.3 kg (p = 0.015).

CONCLUSION

The SAM/SM combination regimen improved the quality of life of PLWAS, however, a greater number of patients and a longer period of follow up, are necessary to arrive at a more meaningful conclusion.

Surgical complications from local herbal practitioners: report of five cases

Over a 12-month period, five patients (out of a total of 72) with serious complications resulting from use of herbs by traditional healers were seen at the surgical unit of Olabisi Onabanjo University Teaching Hospital, Sagamu, Nigeria. The age range was one and a half to five years with a mean age of 23.4 +/- SD years and a male to female ratio of 3:2. All the cases were misdiagnosed and mismanaged and ended up with various complications. Such as penile amputations, digital necrosis, upper and lower limb gangrene as well a severe sepsis among others. Ignorance, cultural beliefs and attitudes, delusion, poverty and inaccessibility to orthodox medical practice were some of the factors responsible for the patronage of traditional healers.

Stroke in south west Nigeria: a 10-year review

BACKGROUND AND PURPOSE

Stroke is a significant economic, social, and medical problem worldwide. This retrospective follow-up study aimed to review the pattern, types, and case fatality of stroke in Nigeria.

METHODS

Records of all stroke patients admitted into Ogun State University Teaching Hospital (OSUTH), Sagamu, from December 1993 to November 2003 were reviewed. Patients were classified into hemorrhage or infarct using the World Health Organization criteria. Information was obtained as to the time of death in those who died and case fatality at 24 hours, 7 days, 30 days, and 6 months recorded. Autopsy records were also reviewed.

RESULTS

A total of 708 stroke patients were reviewed and this constituted 2.4% of all emergency admissions. On clinical grounds, 49% of the patients had cerebral infarction (CI) and 45% had intracerebral hemorrhage (ICH), whereas 6% had subarachnoid hemorrhage. Stroke constituted 1.8% of all deaths at the emergency unit and the case fatality was 9% at 24 hours, 28% at 7 days, 40% at 30 days, and 46% at 6 months.

CONCLUSIONS

Stroke constitutes a significant cause of mortality and the need for prompt institution of intensive treatment is emphasized. A changing pattern with an increasing frequency of hemorrhagic stroke in our population is suspected. However, because this was a retrospective study based on clinical examination in a highly selected stroke population, neuroimaging confirmation would be needed for any future prospective hospital or population-based studies.

Anterior spinal artery syndrome complicating aortic dissecting aneurysm: case report

Spinal Cord ischaemia is rare in the absence of trauma. We report a case of a 45 year old known hypertensive for six years, who presented with features of anterior spinal artery syndrome (ASAS) complicating acute dissection of the descending aorta. He developed sudden onset non-traumatic paraparesis, sphincteric dysfunction and dissociated anaesthesia with a sensory level at T6. This was preceded by a two weeks' history of severe, sharp, lancinating, tearing left parasternal chest pain radiating to the back. He was managed conservatively on pentazocine lactate (fortwin), calcium- and beta-blockers, steroids, anti-platelet and free-radical scavengers. On the 8th day of hospitalisation, he had a sudden abdominal distension, bled from the nose and mouth, went into hypovolaemic shock and died within a time frame of two minutes. He was presumed to have had a progression of the aortic dissection with subsequent rupture. Dissecting aortic aneurysm could run a benign asymptomatic or a lethal course and a high index of suspicion is necessary. The lack of exhaustive diagnostic investigative tools as well as surgical intervention in the management of this patient in a developing country was highlighted as was possible that the patient could have been mismanaged.

Clinical manifestations of myasthenia gravis - review of cases seen at the Lagos University Teaching Hospital

OBJECTIVE

to review cases of myasthenia gravis at the Lagos University Teaching Hospital.

METHODS

features of 27 cases of myasthenia gravis seen at the Neurology outpatient clinic of the Lagos University Teaching Hospital between January 1995 and December 2000 were reviewed using a uniform protocol.

RESULTS

peak age incidence was in the third decade, and the male to female ratio 1.7 to 1. The commonest presentation was ptosis (85.1% ), followed by diplopia (37% ) and limb weakness (37% ). Other features such as dysphonia, dysphagia and dysarthria, were relatively uncommon. Ocular myasthenia gravis was diagnosed in half of the patients and generalised myasthenia in the other half. All the patients except four responded satisfactorily to prednisolone and/or anti-cholinesterase. Azathioprine was added to the treatment of those that did not respond well, and replaced prednisolone in a patient who developed steroid-induced diabetes mellitus. One patient developed myasthenic crisis and required artificial ventilator support. One patient had thymectomy.

CONCLUSION

cases of myasthenia gravis present infrequently at the neurology clinic of the Lagos University Teaching Hospital. Clinical presentation and response to treatment are similar to those described elsewhere.

Spectrum and outcome of clinical diseases in adults living with AIDS at the Ogun State University Teaching Hospital

OBJECTIVES

To evaluate the changing frequency of HIV/AIDS amongst medical admissions as well as the spectrum and outcome of clinical diseases among these patients.

DESIGN

Retrospective study.

SETTING

Tertiary hospital in Nigeria.

PARTICIPANTS

Two hundred and six People Living With AIDS (PLWA) admitted at the medical wards during the period 1992 to 2002.

INTERVENTION

Treatment was symptomatic in all patients and where appropriate, specific treatment was administered for indicator diseases. Highly Active Anti-retroviral Therapy (HAART) was not used.

MAIN OUTCOME MEASURES

Mortality within six months of diagnosis.

RESULTS

PLWA constituted 4.2% of all medical admissions. The frequency increased from 0% in 1992 to 7.6% in 2001, and dropped to 5% by the year 2002. Seventy patients (34%) died within six months of diagnosis.

RESULTS

This study has demonstrated an increasing frequency of HIV/AIDS amongst our medical in-patients from none in 1992 to 7.6% in 2001, and thereafter, a decline in 2002. We suspect that this decline could be a reflection of the health education on HIV, its increasing awareness and the widespread utilisation of effective control measures. Furthermore, the administration of highly active anti retroviral therapy (HAART) to a segment of PLWA in Sagamu by the community medicine department could be contributory.

CONCLUSION

A community based study would be needed to assess the efficacy or otherwise of these current control measures. The advent of saliva and urine tests for HIV detection would ease specimen collection and increase compliance and participation at the community level.

Disulfide bonds in merozoite surface protein 1 of the malaria parasite impede efficient antigen processing and affect the in vivo antibody response

Vol. 34(3) 2004, DOI 10.1002/eji.200324514 Due to a technical error, the wrong affiliations were given for C. Moss and V. Lindo. These are correct as given above. See original article http://dx.doi.org/10.1002/eji.200324514.

Comparison of Siriraj Stroke Score and the WHO criteria in the clinical classification of stroke subtypes

Clinical distinction between cerebral haemorrhage (CH) and cerebral infarction (CI) is important in the management of stroke patients in areas where CT scan facility is lacking or access limited by cost and distance. This distinction is necessary in our environment where an increasing proportion of patients are suspected to have haemorrhagic stroke. This study compares Siriraj stroke score (SSS) and the WHO criteria for the acute stroke syndrome as simple tools for this purpose. The computerised tomography (CT) brain scans of all patients referred with clinical diagnosis of stroke at the University College Hospital (UCH), Ibadan, and RADMED diagnostic centre. Lagos were retrieved and reviewed as well as the case notes of these patients at the referral hospitals. Relevant clinical data were extracted from the case records. The patients were classified into either CI or CH using the WHO criteria for acute stroke syndrome and the SSS. This classification was compared with the CT scan diagnosis using the latter as the gold standard. Data analysis was performed with Epi-info software, and Kappa statistics (k value) for comparability test with 95% confidence interval was used to compare the two clinical criteria with the gold standard. Ninety-six patients had complete clinical records and CT scan features consistent with the diagnosis of stroke, of which 52 were diagnosed as CI and 44 as CH. SSS had sensitivity of 50% for haemorrhage and 58% for infarction with an overall accuracy of 54.2%. The WHO criteria for the acute stroke syndrome had sensitivity of 73% for haemorrhage and 69% for infarction with an overall accuracy of 71%. The kappa coefficient was 0.18 for the SSS and 0.41 for the WHO criteria. The diagnostic accuracy of the WHO criteria for the acute stroke syndrome is higher than that of the Siriraj stroke score. The WHO criteria showed moderate agreement (k=0.41) with the CT scan, while the SSS showed no agreement (k=0.18). When CT scan is not affordable or its use is limited by distance, the WHO criteria for acute stroke syndrome could be more useful. A prospective study with a larger sample size is suggested for definitive conclusion.

Sequence diversity and antigenic polymorphism in the Plasmodium yoelii p235 high molecular mass rhoptry proteins and their genes

A gene family in Plasmodium yoelii YM encodes p235, a group of high molecular mass erythrocyte-binding rhoptry proteins. Sequence analysis of 6 cDNA clones from the 3' end of expressed p235 genes divided them into two groups corresponding to genes on chromosomes 1, and 5 and 6, respectively. Twelve partial p235 protein sequences, derived from cDNA sequences from the region with greatest protein sequence similarity to Plasmodium vivax RBP2, fell into three groups, together with one chimeric sequence. A comparison of these cDNA sequences with genomic DNA sequences from the same region suggested that only a subset of the gene repertoire is expressed. Three genomic DNA clones, derived from the 5' end of p235 genes designated E1, E2, and E5 and located on chromosome 5/6, were also obtained and aligned with sequences from the known E8 and E3 genes. In the region of overlap there was only approximately 27% protein sequence identity, indicating that the sequences in this p235 N-terminal region are more diverse than at the C-terminal end. This sequence variation in the expressed genes did not result in antigenically different rhoptry proteins as detected with a panel of p235-specific mAbs. Only one schizont out of 500 examined with mAb 25.86 appeared to be an antigenic variant, with all of the developing merozoites in this schizont being mAb 25.86 negative. No other antigenic variants were detected with the other antibodies, and therefore it is likely that these antibodies recognise conserved epitopes.

The merozoite surface protein 6 gene codes for a 36 kDa protein associated with the Plasmodium falciparum merozoite surface protein-1 complex

A complex of non-covalently bound polypeptides is located on the surface of the merozoite form of the human malaria parasite Plasmodium falciparum. Four of these polypeptides are derived by proteolytic processing of the merozoite surface protein 1 (MSP-1) precursor. Two components, a 22 and a 36 kDa polypeptide are not derived from MSP-1. The N-terminal sequence of the 36 kDa polypeptide has been determined, the corresponding gene cloned, and the protein characterised. The 36 kDa protein consists of 211 amino acids and is derived from a larger precursor of 371 amino acids. The precursor merozoite surface protein 6 (MSP-6) has been designated, and the 36 kDa protein, MSP-6(36). Mass spectrometric analysis of peptides released from the polypeptide by tryptic digestion confirmed that the gene identified codes for MSP-6(36). Antibodies were produced to a recombinant protein containing the C-terminal 45 amino acid residues of MSP-6(36). In immunofluorescence studies these antibodies bound to antigen at the parasite surface or in the parasitophorous vacuole within schizonts, with a pattern indistinguishable from that of antibodies to MSP-1. MSP-6(36) was present in the MSP-1 complex immunoprecipitated from the supernatant of in vitro parasite cultures, but was also immunoprecipitated from this supernatant in a form not bound to MSP-1. Examination of the MSP-6 gene in three parasite lines detected no sequence variation. The sequence of MSP-6(36) is related to that of the previously described merozoite surface protein 3 (MSP-3). The MSP-6(36) amino acid sequence has 50% identity and 85% similarity with the C-terminal region of MSP-3. The proteins share a specific sequence pattern (ILGWEFGGG-[AV]-P) and a glutamic acid-rich region. The remainder of MSP-6 and MSP-3 are unrelated, except at the N-terminus. Both MSP-6(36) and MSP-3 are partially associated with the parasite surface and partially released as soluble proteins on merozoite release. MSP-6(36) is a hydrophilic negatively charged polypeptide, but there are two clusters of hydrophobic amino acids at the C-terminus, located in two amphipathic helical structures identified from secondary structure predictions. It was suggested that this 35 residue C-terminal region may be involved in MSP-6(36) binding to MSP-1 or other molecules; alternatively, based on the secondary structure and coil formation predictions, the region may form an intramolecular anti-parallel coiled-coil structure.

Effectiveness of high dose dexamethasone in the treatment of acute stroke

A prospective double-blind placebo-controlled, randomised clinical trial was carried out to determine the effectiveness of short-course of high dose dexamethasone therapy on mortality and neurological recovery in stroke patients. During a sixteen month period of study, 230 patients with clinical diagnosis of stroke were seen. Of these, 40 were eligible for the study (27 were presumed to have had haemorrhagic stroke; and 13 were presumed to have had cerebral infarction). The commonest cause of exclusion was presentation after 24 hours of the ictus. Patients were sequentially paired and randomised into high dose dexamethasone and placebo groups in a double-blind fashion. There were twenty patients in either group. Of the 27 patients with haemorrhagic stroke, 15 were in the dexamethasone group and 12 in the placebo group. Of the 13 patients with cerebral infarction, 5 were in the dexamethasone group and 8 in the placebo group. Each patient received 100 mg of dexamethasone stat, and 16 mg every 6 hours for a period of 48 hours or equivalent volumes of placebo. Assessment of each patient was done using a neurological score. Sequential analysis by Armitage was employed, using survival at 1 month as the primary criterion of effectiveness. Survivors were followed-up for 6 months. At the end of one month, 16 patients (80%) had died in the dexamethasone group and 17 (85%) in the placebo group. The average day of death was six days in the dexamethasone group and 15 days in the placebo group, but this was not statistically significant. Of the seven survivors at one month, four were in the dexamethasone group and 3 in the placebo group. Five of them had cerebral infarction and two had haemorrhagic stroke. The two in the haemorrhagic subgroup who survived the first month died at the 2nd and 4th month respectively. At the end of six months, only the five patients with cerebral infarction were alive. Of these, 2 in the dexamethasone group were back at work while the third was chair-bound. The 2 survivors in the placebo group were chair and bed bound respectively. In conclusion, this study failed to demonstrate any benefit of a short-course of high dose steroid in improving the mortality of stroke patients and its use should be discouraged. However, possible benefit in the morbidity of survivors in the patients with cerebral infarction requires further studies.

Pattern and outcome of medical admissions at the Ogun State University Teaching Hospital, Sagamu--a three year review

This is a three-year retrospective study of the pattern and outcome of acute medical admissions at the Ogun State University Teaching Hospital, Sagamu. Our findings showed that there were 1,938 admissions over the study period of which 1,044 (54%) were females and 894 (46%) were males. The ages of the patients ranged between 12 to 86 years with a mean of 49 +/- 1.7 years. The age range was 14 to 80 years for males with a mean of 47 +/- 6.1 years and 12 to 86 years for females with a mean of 49 +/- 4.5 years. The length of stay was between 5 to 25 days with a mean of 15 +/- 0.5 days. There were 16 patients per bed per year with a turn around of 8 days and bed occupancy of 65% 194 (10%) patients discharged themselves against medical advice and there were 488 (25%) deaths. The interval between admission and death ranged between 4 to 7 days with a mean of 5.5 +/- 0.07 days. Indications for admissions were infectious diseases (38%), neurological disorders (19.6%) gastro-intestinal disorders (11%), genito-urinary tract disorders (10.2%) endocrine disorder (10%), cardiovascular disorders (9.9%), respiratory disorders (6.4%) and haematological disorders (4.9%). Tuberculosis accounted for 10% of total medical admissions and was the commonest disease entity responsible for medical admissions. Acquired immuno deficiency syndrome (AIDS) constituted 1.8% of medical admissions. Mortality was highest for infections accounting for 32% of deaths while malaria accounted for the lowest. The reasons for the relative frequency and mortality are adduced. The study recommends improvement of preventive strategies towards communicable diseases in the community and encourages better admission policy, provision of appropriate facilities and manpower to improve the hospital services.

Plasmodium yoelii: effects of red blood cell modification and antibodies on the binding characteristics of the 235-kDa rhoptry protein

The 235-kDa rhoptry protein of the rodent malaria parasite Plasmodium yoelii yoelii was shown to bind to the surface of mouse red blood cells in a calcium-independent process, using a erythrocyte-binding assay. This binding is affected by modification of the surface of the red blood cells by enzymatic treatment. Chymotrypsin and trypsin but not neuraminidase treatment of the erythrocytes significantly reduced the binding of the 235-kDa proteins. The binding of an unrelated 135-kDa protein was abolished by treatment with chymotrypsin. Although the 235-kDa proteins bind to both reticulocytes and mature red blood cells, the binding to mature cells was more pronounced. In the presence of hyperimmune infection serum or specific polyclonal antibodies to the 235-kDa protein its binding to erythrocytes was reduced, further demonstrating the specificity of this ligand-receptor interaction.

Immunization with parasite-derived apical membrane antigen 1 or passive immunization with a specific monoclonal antibody protects BALB/c mice against lethal Plasmodium yoelii yoelii YM blood-stage infection

We have purified apical merozoite antigen 1 (AMA-1) from extracts of red blood cells infected with the rodent malaria parasite Plasmodium yoelii yoelii YM. When used to immunize mice, the protein induced a strong protective response against a challenge with the parasite. Monoclonal antibodies specific for P. yoelii yoelii AMA-1 were prepared, and one was very effective against the parasite on passive immunization. A second protein that appears to be located in the apical rhoptry organelles and associated with AMA-1 was identified.

Misdiagnosis of stroke--a computerised tomography scan study

Misdiagnosis of stroke has significant implication for definitive therapy. This study assessed the frequency of misdiagnosis of stroke using computerised tomography (CT) scan of the brain. One hundred and fifty-six patients admitted over a five year period (1991-1996) with clinical features suggestive of stroke had their CT brain scan reviewed. Only 89 (57%) had neuroradiological features consistent with stroke, of which 59 (66%) had cerebral infarction while 30 (34%) had cerebral haemorrhage. In 67 (43%) of the cases, there were no features of cerebro-vascular accident (CVA) on the CT scan. In this group, cerebral atrophy was the commonest radiological abnormality (21/67), followed by brain tumor (10/67) and subdural haematoma (9/67). The CT scan was normal in 25 patients. The misdiagnosis of surgically treatable conditions in as many as 21 (13.5%) of the 156 patients calls for better neurological evaluation of patients admitted for stroke in tertiary and non-tertiary hospitals. Where available, patients with clinical diagnosis of stroke should have CT scan evaluation to ensure that patients who can be helped surgically are identified early and appropriately treated.

Antigenic and sequence diversity at the C-terminus of the merozoite surface protein-1 from rodent malaria isolates, and the binding of protective monoclonal antibodies

Merozoite surface protein-1 (MSP-1) is a major candidate in the development of a vaccine against malaria. Immunisation with a recombinant fusion protein containing the two Plasmodium yoelii MSP-1 C-terminal epidermal growth factor-like domains (MSP-1(19)) can protect mice against homologous but not heterologous challenge, and therefore, antigenic differences resulting from sequence diversity in MSP-1(19) may be crucial in determining the potential of this protein as a vaccine. Representative sequence variants from a number of distinct P. yoelii isolates were expressed in Escherichia coli and the resulting recombinant proteins were screened for binding to a panel of monoclonal antibodies (Mabs) capable of suppressing a P. yoelii YM challenge infection in passive immunisation experiments. The sequence polymorphisms affected the binding of the antibodies to the recombinant proteins. None of the Mabs recognised MSP-1(19) of P. yoelii yoelii 2CL or 33X or P. yoelii nigeriensis N67. The epitopes recognised by the Mabs were further distinguished by their reactivity with the other fusion proteins. The extent of sequence variation in MSP-1(19) among the isolates was extensive, with differences detected at 35 out of the 96 positions compared. Using the 3-dimensional structure of the Plasmodium falciparum MSP-1(19) as a model, the locations of the amino acid substitutions that may affect Mab binding were identified. The DNA sequence of MSP-1(19) from two Plasmodium vinckei isolates was also cloned and the deduced amino acid sequence compared with that in other species.

Chromosomal organisation of a gene family encoding rhoptry proteins in Plasmodium yoelii

The genomic organisation of the genes coding for a group of high molecular mass rhoptry proteins of the rodent malaria parasite Plasmodium yoelii YM was investigated using blotting, two dimensional gel electrophoresis and restriction fragment length analysis. The genes were found on chromosomes 1, 5, 6 and 10, with the possibility that related genes were also present on chromosomes 3 and 4. On chromosome 1 the genes were located close to one end, whereas they were present at both ends of chromosome 5, 6 and 10. Two genes, e3 and e8, that had been partially characterised previously were present on chromosomes 5 and 1, respectively. Based on an analysis of the 3' end of the genes, three subfamilies present on chromosomes 1, 5 and 6, and 10, respectively, were identified.

Passive immunization with antibodies against three distinct epitopes on Plasmodium yoelii merozoite surface protein 1 suppresses parasitemia

We have produced monoclonal antibodies against Plasmodium yoelii merozoite surface protein 1 (MSP-1) and have assessed their ability to suppress blood stage parasitemia by passive immunization. Six immunoglobulin G antibodies were characterized in detail: three (B6, D3, and F5) were effective in suppressing a lethal blood stage challenge infection, two (B10 and G3) were partially effective, and one (B4) was ineffective. MSP-1 is the precursor to a complex of polypeptides on the merozoite surface; all of the antibodies bound to this precursor and to an approximately 42-kDa fragment (MSP-142) that is derived from the C terminus of MSP-1. MSP-142 is further cleaved to an N-terminal approximately 33-kDa polypeptide (MSP-133) and a C-terminal approximately 19-kDa polypeptide (MSP-119) comprised of two epidermal growth factor (EGF)-like modules. D3 reacted with MSP-142 but not with either of the constituents MSP-133 and MSP-119, B4 recognized an epitope within the N terminus of MSP-133, and B6, B10, F5, and G3 bound to MSP-119. B10 and G3 bound to epitopes that required both C-terminal EGF-like modules for their formation, whereas B6 and F5 bound to epitopes in the first EGF-like module. These results indicate that at least three distinct epitopes on P. yoelii MSP-1 are recognized by antibodies that suppress parasitemia in vivo.

Glycosylphosphatidylinositols of Plasmodium chabaudi chabaudi: a basis for the study of malarial glycolipid toxins in a rodent model

Free and protein-bound glycosylphosphatidylinositols (GPIs) of the blood stages of the rodent malarial parasite Plasmodium chabaudi chabaudi AS were identified and characterized. TLC analysis of material extracted by organic solvents from metabolically labelled parasites revealed a distinct set of glycolipids. These glycolipids were identified as GPIs by specific chemical and enzymic treatments and by structural analysis of their glycan and hydrophobic parts. These analyses revealed that P.c.chabaudi AS synthesizes a set of GPI-biosynthesis intermediates and two potential GPI-anchor precursors exhibiting the following structures: ethanolamine-phosphate [(alpha1-2)mannose]mannose (alpha 1-2) mannose (alpha 1-6) mannose (alpha 1-4) glucosamine - (acyl) inositol-phosphate-diacylglycerol (P.ch. alpha) and ethanolamine-phosphate - mannose (alpha 1-2) mannose (alpha 1-6) mannose (alpha 1-4) glucosamine-(acyl)inositol-phosphate-diacylglycerol (P.ch. beta). One of these GPI-anchor precursors (P.ch. alpha) possesses the same carbohydrate structure as the GPI membrane anchor of merozoite surface protein-1 from P.c.chabaudi AS.

Immunization against the murine malaria parasite Plasmodium yoelii using a recombinant protein with adjuvants developed for clinical use

Mice vaccinated with a recombinant protein containing the two EGF-like modules of Plasmodium yoelii merozoite surface protein-1 in liposomes or combined with the formulations SBAS2.1 and SBAS2, were protected against a lethal malaria infection. The protection achieved with these adjuvants developed for clinical use was as good as or better than that achieved with Freund's adjuvant. A parasite-specific response was needed for protection. Analysis of the immunoglobulin sub-class response showed that MSP-1-specific IgG1, and to a lesser extent IgG2a and IgG2b, were induced, suggesting that these antibodies were important for protection. Mice passively immunized with serum or purified IgG from vaccinated mice had delayed onset of parasitemia and were able to control the infection.

Cytokines and antibody subclass associated with protective immunity against blood-stage malaria in mice vaccinated with the C terminus of merozoite surface protein 1 plus a novel adjuvant

A blood-stage malaria antigen comprising the C terminus of merozoite surface protein 1 fused to glutathione S-transferase, combined with an adjuvant formulation containing squalane, Tween 80, and pluronic L121 (AF), administered subcutaneously protected mice against death from a lethal Plasmodium yoelii infection. The protection induced by this antigen-adjuvant combination was compared with that induced by the antigen plus saponin in terms of survival from the lethal infection and clearance of parasitemia. The levels of gamma interferon and interleukin-4 in spleens were measured as indicators of Th1 and Th2 cell activation, and antibody classes and subclasses were determined by immunofluorescence. With a 10-micrograms dose of antigen and AF as adjuvant, all mice recovered, but with saponin as the adjuvant, there were only a few survivors. With 30 micrograms of antigen plus AF, the peak parasitemias were 10-fold lower than those with 10 micrograms; with saponin, survival was slightly improved. The levels of both gamma interferon and interleukin-4 rose more rapidly and to higher levels with AF as the adjuvant than with saponin, and the same was true for immunoglobulin G1 (IgG1), IgG2a, and IgG2b subclasses. Thus, in terms of both cytokine production and antibody levels, AF is a more potent adjuvant for a malaria vaccine than is saponin.

The combined epidermal growth factor-like modules of Plasmodium yoelii Merozoite Surface Protein-1 are required for a protective immune response to the parasite

We have reported previously that immunization with a bacterial recombinant protein containing the two epidermal growth factor (EGF)-like modules of Plasmodium yoelii Merozoite Surface Protein-1 (MSP-1) protected mice against challenge with this malaria parasite. Bacterial plasmids containing sequences coding for the individual modules fused to glutathione S-transferase (GST) have now been made. The fusion protein containing the combined EGF-like modules was recognized by anti-parasite antibodies and was immunogenic, producing high titre anti-parasite and anti-GST antibodies. In contrast, fusion proteins containing the two individual EGF-like modules reacted poorly with the natural antibodies and their proteins, as well as a simple mixture of them, induced low levels of anti-parasite antibodies despite producing high levels of anti-GST antibody. Antibodies raised to the recombinant proteins recognized the 230 kDa MSP-1. Groups of mice immunized with the different recombinant proteins were challenged with parasites: protection was observed in the group which had received the recombinant protein containing both modules but not in those groups immunized with the individual modules, either alone or as a mixture. These results suggest that there are important structural determinants formed by the two modules together, which are not present in either of the individual domains alone, and which are responsible for the immunogenicity of the protein or are the target of protective antibodies.

Plasmodium yoelii: brefeldin A-sensitive processing of proteins targeted to the rhoptries

We have shown that a family of high-molecular-mass proteins can be detected in lysates of parasitized erythrocytes using antibodies specific for a Plasmodium yoelii rhoptry protein. When these polypeptides are biosynthetically labeled in the presence of brefeldin A or at 15 degrees C, their electrophoretic mobility on polyacrylamide gels is decreased. Removal of the drug restores the size of the polypeptides to that in the absence of the drug. These results indicate that the proteins undergo a processing event, most probably a proteolytic cleavage, which is inhibited by brefeldin A and low temperature. The data suggest that the proteins are moved by secretory transport from the endoplasmic reticulum through a functional Golgi to the rhoptry organelles.

Immunization against malaria with a recombinant protein

We have expressed in bacteria the C-terminal part of Plasmodium yoelii merozoite surface protein-1 (MSP1) containing the two epidermal growth factor-like domains. The protein, either alone or fused to glutathione S-transferase, was highly effective as a vaccine and protected mice against challenge infection. Reduction and alkylation abolished the protection obtained with the protein. This shows for the first time the absolute requirement of the disulphide-bonded conformation for immunogenicity. In a short term experiment, mice were protected against a massive challenge. The immunity was effective at the time of merozoite release/reinvasion. Recombinant protein based on this part of MSP1 may be suitable as a vaccine against malaria.

In vivo selection of populations of Plasmodium chabaudi chabaudi AS resistant to a monoclonal antibody that reacts with the precursor to the major merozoite surface antigen

Mice bearing a hybridoma secreting a monoclonal antibody (MAb), MAb-3, which significantly delays the onset of a Plasmodium chabaudi chabaudi AS, but not P. chabaudi chabaudi CB, challenge parasitemia in a passive transfer assay and which is specific for the precursor to the major merozoite surface antigen (PMMSA) of P. chabaudi chabaudi AS, were challenged intravenously with 10(3) P. chabaudi chabaudi AS-parasitized erythrocytes. The resultant parasitemia was very similar to that in normal mice except that initially the parasitemia was sometimes slightly delayed. Parasites derived from cryopreserved stabilates isolated from MAb-3 hybridoma mice with an unmodified parasitemia, or with a delayed parasitemia, were found to have lost their susceptibility to MAb-3 in the passive transfer assay. A number of anti-PMMSA MAb were used to immunoprecipitate lysates of parasite populations isolated directly from hybridoma-bearing mice. In some instances and with certain of the MAb, immunoprecipitation patterns were modified, but other isolates were not detectably different when compared with unselected P. chabaudi chabaudi AS parasites. Using a panel of MAb reacting with the PMMSA of P. chabaudi chabaudi AS, immunoprecipitation patterns of parasites derived from cryopreserved stabilates isolated from hybridoma-bearing mice were determined at 2-h intervals through the appropriate part of the parasite maturation cycle. In these derived populations, resistance to MAb-3 was not associated with a change in the immunoprecipitation reaction with the MAb used. These results are discussed in the context of current knowledge of genotypic and phenotypic antigenic diversity of malaria parasites and other protozoa.