Murine neutralizing antibody response and toxicity to synthetic peptides derived from E1 and E2 proteins of hepatitis C virus

INTRODUCTION

The highest estimated prevalence of HCV infection has been reported in Egypt, nearly 12% mostly type 4. Currently, a commercial vaccine to protect this high risk population as well as global HCV infected patients is not available.

OBJECTIVES

In the present study, we aim at: (1) examining the viral binding capacities of purified monospecific polyclonal murine antibodies raised against genetically conserved viral protein sequences, i.e. synthetic peptides derived from those sequences located within envelope proteins and (2) assessment of immunogenic properties and safety parameters of those peptides individually and in a vaccine format in mice.

METHODS

Purified IgG Abs from immunized mice were used in immunocapture RT-PCR experiments to test viral neutralization by Abs raised against each of 4 peptides termed p35 (E1), p36 (E2), p37 (E2) and p38 (E2). Swiss mice were immunized with each of the 3 peptides (p35, p37 and p38) which generated neutralizing antibodies in immunocapture experiments. Antibody responses to corresponding peptides were determined using different routes of administration, different adjuvants, different doses and at different time points post-injection. To explore the dose range for future pharmacological studies, three doses namely 50 ng, 10 μg and 50 μg/25 gm mouse body weight were tested for biochemical and histopathological changes in several organs.

RESULTS

Murine Abs against p35, p37 and p38 but not p36 showed HCV neutralization in immunocapture experiments. Subcutaneous injection of peptides elicited higher responses than i.m. and i.p. Immunization with Multiple Antigenic Peptide (MAP) form or coupled to Al PO4 elicited the highest Ab responses. Peptide doses of 50 ng/25 gm body weight or less were effective and safe, however dose assessment still requires further study. Histopathological changes were observed in animals that received doses ∼1000 times higher than the potential therapeutic dose.

CONCLUSION

Exploration of humoral immunogenicity, neutralization capacity and safety suggested that the peptides presented herein are candidate vaccine components for further preclinical assessment.

Murine neutralizing antibody response and toxicity to synthetic peptides derived from E1 and E2 proteins of hepatitis C virus

INTRODUCTION

The highest estimated prevalence of HCV infection has been reported in Egypt, nearly 12% mostly type 4. Currently, a commercial vaccine to protect this high risk population as well as global HCV infected patients is not available.

OBJECTIVES

In the present study, we aim at: (1) examining the viral binding capacities of purified monospecific polyclonal murine antibodies raised against genetically conserved viral protein sequences, i.e. synthetic peptides derived from those sequences located within envelope proteins and (2) assessment of immunogenic properties and safety parameters of those peptides individually and in a vaccine format in mice.

METHODS

Purified IgG Abs from immunized mice were used in immunocapture RT-PCR experiments to test viral neutralization by Abs raised against each of 4 peptides termed p35 (E1), p36 (E2), p37 (E2) and p38 (E2). Swiss mice were immunized with each of the 3 peptides (p35, p37 and p38) which generated neutralizing antibodies in immunocapture experiments. Antibody responses to corresponding peptides were determined using different routes of administration, different adjuvants, different doses and at different time points post-injection. To explore the dose range for future pharmacological studies, three doses namely 50 ng, 10 μg and 50 μg/25 gm mouse body weight were tested for biochemical and histopathological changes in several organs.

RESULTS

Murine Abs against p35, p37 and p38 but not p36 showed HCV neutralization in immunocapture experiments. Subcutaneous injection of peptides elicited higher responses than i.m. and i.p. Immunization with Multiple Antigenic Peptide (MAP) form or coupled to Al PO4 elicited the highest Ab responses. Peptide doses of 50 ng/25 gm body weight or less were effective and safe, however dose assessment still requires further study. Histopathological changes were observed in animals that received doses ∼1000 times higher than the potential therapeutic dose.

CONCLUSION

Exploration of humoral immunogenicity, neutralization capacity and safety suggested that the peptides presented herein are candidate vaccine components for further preclinical assessment.

Conserved peptides within the E2 region of Hepatitis C virus induce humoral and cellular responses in goats

The reason(s) why human antibodies raised against hepatitis C virus (HCV) E2 epitopes do not offer protection against multiple viral infections may be related to either genetic variations among viral strains particularly within the hypervariable region-1 (HVR-1), low titers of anti E2 antibodies or interference of non neutralizing antibodies with the function of neutralizing antibodies. This study was designed to assess the immunogenic properties of genetically conserved peptides derived from the C-terminal region of HVR-1 as potential therapeutic and/or prophylactic vaccines against HCV infection. Goats immunized with E2-conserved synthetic peptides termed p36 (a.a 430-446), p37(a.a 517-531) and p38 (a.a 412-419) generated high titers of anti-p36, anti-p37 and anti-P38 antibody responses of which only anti- p37 and anti- p38 were neutralizing to HCV particles in sera from patients infected predominantly with genotype 4a. On the other hand anti-p36 exhibited weak viral neutralization capacity on the same samples. Animals super-immunized with single epitopes generated 2 to 4.5 fold higher titers than similar antibodies produced in chronic HCV patients. Also the studied peptides elicited approximately 3 fold increase in cell proliferation of specific antibody-secreting peripheral blood mononuclear cells (PBMC) from immunized goats. These results indicate that, besides E1 derived peptide p35 (a.a 315-323) described previously by this laboratory, E2 conserved peptides p37 and p38 represent essential components of a candidate peptide vaccine against HCV infection.

Conserved peptides within the E2 region of Hepatitis C virus induce humoral and cellular responses in goats

The reason(s) why human antibodies raised against hepatitis C virus (HCV) E2 epitopes do not offer protection against multiple viral infections may be related to either genetic variations among viral strains particularly within the hypervariable region-1 (HVR-1), low titers of anti E2 antibodies or interference of non neutralizing antibodies with the function of neutralizing antibodies. This study was designed to assess the immunogenic properties of genetically conserved peptides derived from the C-terminal region of HVR-1 as potential therapeutic and/or prophylactic vaccines against HCV infection. Goats immunized with E2-conserved synthetic peptides termed p36 (a.a 430-446), p37(a.a 517-531) and p38 (a.a 412-419) generated high titers of anti-p36, anti-p37 and anti-P38 antibody responses of which only anti- p37 and anti- p38 were neutralizing to HCV particles in sera from patients infected predominantly with genotype 4a. On the other hand anti-p36 exhibited weak viral neutralization capacity on the same samples. Animals super-immunized with single epitopes generated 2 to 4.5 fold higher titers than similar antibodies produced in chronic HCV patients. Also the studied peptides elicited approximately 3 fold increase in cell proliferation of specific antibody-secreting peripheral blood mononuclear cells (PBMC) from immunized goats. These results indicate that, besides E1 derived peptide p35 (a.a 315-323) described previously by this laboratory, E2 conserved peptides p37 and p38 represent essential components of a candidate peptide vaccine against HCV infection.

Kala-azar in a high transmission focus: an ethnic and geographic dimension

In 1994-1996, we studied a group of 58 game wardens stationed in an area known to be highly endemic for visceral leishmaniasis (kala-azar) for evidence of infection with Leishmania donovani. Leishmania DNA was detected by the polymerase chain reaction in the peripheral blood of cases of active kala-azar, former patients with visceral leishmaniasis, patients, and asymptomatic subjects. Using the cloned antigen rk39, antibodies were detected in 44.2% of the game wardens while leishmanin skin test result was positive in 77% of our sample. It was shown that certain tribes from northern Sudan were more likely to develop subclinical infections, while those of the Baria tribe from southern Sudan and those of the Nuba tribe from western Sudan were more likely to develop visceral leishmaniasis. Whether this is due to genetic factors or previous exposure to Leishmania parasites remains to be elucidated.

Kimura's disease

Kimura's disease is a rare condition of unknown aetiology. It usually presents as a mass in the head and neck region. The diagnosis is confirmed by biopsy and usually treated by excision even though recurrence is common. This condition can be mistaken for a malignant tumour. In this case report Kimura's disease presented as a non-specific lymphadenitis in an Arab patient.

Partially reversible nerve deafness due to vincristine

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Peri-operative supraventricular arrhythmias in coronary bypass surgery

One hundred consecutive admissions for coronary bypass surgery were studied to establish the incidence of peri-operative supraventricular arrhythmias, to monitor their evolution, and to identify their possible aetiological factors. No important arrhythmias were detected before the operation. Post-operatively, 24 patients (24%) developed supraventricular arrhythmias. Nineteen of them had atrial fibrillation or flutter (19%), 2 had supraventricular tachycardia (2%), and 3 had inappropriate sinus bradycardia (less than 45 min) (3%). Almost two-thirds of the arrhythmias occurred within the critical early post-operative period (63%). Haemodynamic compromise ushered the onset of arrhythmias in more than one-third of the patients in whom antiarrhythmic measures ensured prompt improvement (37.5%). Three-quarters of those with atrial fibrillation or flutter were back in sinus rhythm at the time of discharge from hospital (74%). The incidence of supraventricular arrhythmia was significantly higher in patients with demonstrable myocardial ischaemia prior to surgery, in patients who underwent adjunctive coronary endarterectomy, or in those in whom topical cardiac cooling was applied (50%, 45%, and 58%, respectively). Supraventricular arrhythmias are frequently encountered during the critical early post-operative period when serious but reversible haemodynamic compromise might be precipitated. Although the nature of the underlying myocardial insult remains obscure, supraventricular arrhythmia may be related more to defective myocardial preservation than to any specific underlying myocardial lesion.

The diagnostic significance of reciprocal ST segment depression in acute myocardial infarction

The relationship between reciprocal ST-segment depression, the result of an early submaximal exercise ECG, and the anatomy of coronary artery disease was explored in 142 patients with acute myocardial infarction. Reciprocal ST-segment depression was observed in 65 per cent of 79 patients with inferior infarction and 57 per cent of 63 with anterior infarction. Thirty-three of the 52 patients with reciprocal ST-segment depression had a significant stenosis of the coronary artery supplying the reciprocal ST-segment territory (63 per cent), and 31 of the 46 patients with a positive exercise test had a significant stenosis of the coronary artery supplying the ischaemic territory (67 per cent). Forty-one of the patients with reciprocal ST-segment depression (79 per cent) and 35 of the patients with positive exercise tests (76 per cent) were found to have multivessel coronary artery disease. The study showed that reciprocal ST-segment depression was associated with stenosis of the coronary artery supplying the territory opposite the infarct in nearly two-thirds of the patients and with multivessel coronary artery disease in almost four-fifths of them. Reciprocal ST-segment depression after infarction was as accurate as a positive submaximal exercise test at predicting the presence of multivessel coronary artery disease.

Preoperative myocardial ischaemia: its relation to perioperative infarction

One hundred consecutive patients undergoing coronary artery bypass surgery were randomly allocated to a preoperative (24 h) intravenous infusion of isosorbide dinitrate (1.5-15 mg/hr) (50 patients) or to placebo (50 patients). The characteristics of the two groups were similar. Evidence of acute myocardial ischaemia was sought by continuous electrocardiographic Holter recordings and acute myocardial infarction by the appearance of new Q waves and increased activity of the creatine kinase MB isoenzyme. Episodes of acute myocardial ischaemia were found in 18% of patients in the control group and in none of those who received isosorbide dinitrate. None the less, the frequency of perioperative myocardial infarction was similar (22% and 18% respectively) in the two groups. Perioperative infarction was significantly more common in women, in patients with unstable angina or poor left ventricular function, in those who had coronary endarterectomy, and in those in whom the aortic clamping time was greater than 50 minutes. These factors may have obscured any effect that prevention of preoperative ischaemia had on perioperative infarction. Preoperative infusion of isosorbide dinitrate eliminated preoperative ischaemia but did not influence the occurrence of perioperative infarction. The probable benefits of prevention of preoperative ischaemia on postoperative left ventricular function, which is a determinant of long term survival, remain to be established.