Edibriol Malaria research in Colombia: has a useful malaria vaccine arrived? The Third Annual Malaria Meeting of the British Society for Parasitology was held in Edinburgh on 14 and 15 February 1991, and its organisers managed something of a coup by attracting Dr M.E. Patarroyo from the Institute of Immunology in Bogota to address the session on Vaccine Trials and Field Studies. Dr Patarroyo is the architect and prime mover in the use of the Colombian Malaria Vaccine, and his presentation at this meeting was important for several reasons. First, this vaccine has been given to very large numbers of people in South America;secondly, he speaks rarely and has so far published very few resultsl'2'3; thirdly, this audience was well placed to make an expert judgement of a full disclosure of his results. This editorial is to spread knowledge of these trials informally to a wider audience. Patarroyo began by making it clear that he saw this work as a paradigm for developing countries tackling their own problems. This was a single-minded Colombian effort, and although he acknowledges his own training in the USA, he tends to disclaim any significant use of 'first world' results in the design of the vaccine. His work at the Institute of Immunology has been well, indeed enviably, funded. Colombia, too, has the natural advantage of indigenous douroucouli monkeys (Aotus). These are incomparably the best experimental animals in which to obtain valid results for human malaria parasites. A substantial colony of douroucoulis was available, and 1168 have been used in trials. Elsewhere, their acquisition is difficult and rarely can more than a dozen or so be used in an experiment in the US or UK. The approach to malaria vaccination in Bogota has been based o n humoral immunity to blood-stage asexual merozoites. This is perfectly rational as far as it goes, for the pathology of malaria is generated by the blood-stages: intraerythrocytic trophozoites and schizonts. These and their progeny, the red cellinvading merozoites (which are briefly 0264-410X/91/040219-02 © 1991 Butterworth-HeinemannLtd
extracellular and on which multiplication depends) are rich in antigens which are known to provoke protective antibody responses. Naturally, this route to malaria vaccination has long been promulgated elsewhere 4. The flaw is that a solely asexual stage vaccine probably can not preclude the earliest parasitaemia (which derives from intrahepatic parasites, resulting from the sporozoites inoculated by mosquito bite), and even slight parasitaemia may cause disease and will allow transmission. However, these considerations weigh less against a vaccine for public health use where malaria is endemic than against a 'tourist' vaccine s. Patarroyo's group, parallelling others, dissected the surface antigens of Plasmodium falciparum merozoites immunologically, using natural immune sera as antibody sources. Then, using individual purified extracted antigen preparatons in Aotus, they concluded that immunogens of 83 kDa and 35 kDa induced sterilizing immunity to subsequent challenge and that species of 155 kDa and 55kDa were partially protective. (These molecules have been quite widely investigated elsewhere: see, for instance, Refs 6, 7). Gene cloning and sequencing work was begun for these molecules in Bogota, but when a gene sequence was published elsewhere which the group identified as representing one of their candidates, they narrowed the focus of their own efforts. The group proceeded to synthesise hundreds of peptides represented by these coding sequences, and tested this enormous panel as immunogens in Aotus, after glutaraldehyde coupling to bovine serum albumin. Patarroyo's summing up of this work is that they found no "magic bullets' amongst these synthetic peptides. Fortunately a number of peptide mixtures proved promising: with one, half of the vaccinated monkeys were protected from all disease when Freund's complete adjuvant was used, although 15% had unmodified malaria. This mixture led to the design of the
copolymer SPf(66),, containing three of the peptides with intervening alanine- asparagine-alanine-proline sequences I'3. This motif is the B-cell immunodominant epitope of the P. falciparum sporozoite coat molecule, the CS protein, and has been used as the basis for two malaria vaccines elsewhere 89. Patarroyo states that it is used in SPf(66) monomers to provide hair-pin bends in the synthetic sequence, rather than for its antigenicity. Monomer units are synthesized with both C and N terminal cysteines and polymerize to give products of 25 35 kDa. Patarroyo openly discussed an attempt at the US Center for Disease Control which failed to replicate his results in monkeys with vaccine synthesized there, following his methods 1°. However, in the first Colombian volunteer trial of SPf(66),, which was conducted in military personnel, five out of six vaccinees showed protection 2. In that and in twelve subsequent trials, the Tumaco series, three patterns of response were identified by high, medium and low antibody titre, which were predictive of parasitological outcome. No significant adverse effects of vaccination were described, and AI(OH)3 adjuvant was optimal, with 1 mg doses of polymer given s.c. on days 0, 30 and 180. Field studies are concluded or underway in Colombia, Venezuela, and Brazil. Almost 27000 individuals, now including large numbers of children, have received vaccine. A field trial in The Gambia, based at the MRC Laboratories, Fajara, is under active consideration. There, transmission is potentially more intense than in the South American locations, and background malaria epidemiological information will be further than elsewhere. It was widely felt that the field studies which Patarroyo briefly described had not been strongly designed and could be improved upon. Broadly they suggested efficacy of 50 60%, favourably influenced by prior exposure. A tantalizing finding of protection from P. tfivax as well as P. falciparum emerged from the Las Majadas trial in Venezuela. What then can the non-speciesspecific protective mechanism be?
Vaccine, Vol. 9, April 1991 219
Editorial
Patarroyo presented a clue linked both to this and to the cause of the low responsiveness seen m about 15% of recipients. Two of the antigen's three constituent peptides will directly bind red cells and painstaking work with short peptides has narrowed this to a motif with tyrosine and neighbouring lysineglutamic acid-lysine (single letter code: Y . . . K E K ) . The red cell ligand which they bind was not disclosed to the meeting, but speculation favours Band 3. This may be exploited by the invasion mechanism of both these parasites, and antibody to the Y . . . KEK epitope may be protective for both by preventing their necessary Band 3 interactions (see Ref. 11 for a discussion of invasion). Extraordinarily, an examination of T-cell receptor V fi gene coding sequences in poor responders suggested they shared Y ... KEK motifs (which were absent from better responders), so causing this crucial epitope to pass unrecognized. Patarroyo and Colombia are to be congratulated on this work ; a malaria vaccine has arrived. It is imperfect, but may well deserve the public acclaim it receives in South America. Let us hope for success in Africa.
G.H. Mitchell Department o1 hnmuno/og.t', Medical School, Guy's Hospilal, Lomhm, UK References 1
2
3
4
5
6
7
220
Patarroyo, M.E., Romero, P., Torres, M.L., Clavijo, P., Moreno, A., Martinez, A. eta/. Induction of protective immunity against experimental infection with malaria using synthetic peptides. Nature 1987, 328, 629-632 Patarroyo, M.E., Amador, R., Clavijo, P., Moreno, A., Guzman, F., Romero, P. et al. A synthetic vaccine protects human against challenge with asexual blood stages of Plasrnodium falciparum malaria. Nature 1988, 332, 158 161 Rodriguez, R., Moreno, A., Guzman. F., Calvo, M. and Patarroyo, M.E. Studies in owl monkeys leading to the development of a synthetic vaccine against the asexual blood stages of Plasmodium falciparum. Am. J. Trop. Med. Hyg. 1990, 43, 90 113 Mitchell, G.H. Vaccination against malaria: its plausibility and the present state of research. Vaccine 1984, 2, 11,%124 Mitchell, G.H. An update on candidate malaria vaccines. In: Vaccines and Vaccination Strategies. Symposium of the British Society for Parasitology (Ed. D.J. McLaren) Parasitology 1989, 98, S29~$47 Holder, A.A. The precursor to major merozoite surface antigens: structure and role in immunity. Prog. Allergy 1988, 41, 72 97 Collins, W.E., Pappaioanou, M., Anders, R.F., Campbell, G.H., Brown, G.V., Kemp,
V a c c i n e , Vol. 9, A p r i l 1991
D.J. etal. Immunisation trials with the ring infected erythrocyte surface antigen of Plasmodium talciparum in owl monkeys (Aotus vociferans). Am. J. Trop. Med. Hyg. 1988, 38, 26~282 Herrington, D.A., Clyde, D.F., Losonsky, G., Cortesia, M., Murphy, J.R., Davis, J. et al. Safety and immunogenicity in man of a synthetic peptide malaria vaccine against Plasmodium falciparum sporozoites. Nature 1987, 328, 257 259 Ballou, W.R., Hoffman, S.L., Sherwood, J.A., Hollingdale, M.R.. Neva, F.A., Hockmeyer, W.T. et al. Safety and efficacy of a
10
11
recombinant DNA Plasmodium falciparum sporozoite vaccine. Lancet 1987, i. 1277 1281 Ruebush. T.K., Campbell, G.H., Moreno. A. Patarroyo, M.E. and Collins, W E Immunization of owl monkeys with a combination of Plasmodium falciparum asexual blood-stage synthetic peptide antigens. Am. J. Trop. Med. Hyg. 1990, 43, 90 114 Mitchell. G H and Bannister, L.H. Malaria parasite invasion: interactions with the red cell membrane. Crit. Rev. Oncol. Haematol. 1988, 8, 255 310
CHANGE OF US REGIONAL EDITOR Stanley Plotkin, retiring editor The true test of the strength and value of a state, institution or journal is its ability to thrive whilst experiencing changes in its key people. V A C C I N E is now subject to such a challenge in the retirement of one of its founding editors, Stanley Plotkin. As a party to the inception of the journal, Stanley brought his many talents to bear on the organization of the US editorial office and his high and respected international profile in the world of w~ccines added strength to his efforts. Through his focus on the virus vaccines (he made major contributions to ttle vaccines in current use in the prophylaxis of rubella, cytomegalovirus disease, polio, varicella, rabies and rotavirus infections), he was able to appreciate the contribution of others to the goal of bringing to service new and improved immunoprophylactics. He was able to fulfil one of the essential functions of an editor in supporting and enhancing the quality of many of the contributions submitted for publication. In parallel with the editorial work, his participation in the activities involved in the operation of V A C C I N E was impressive, and his wisdom and dedicated commitment to our full and frank discussions will have a lasting influence. We are pleased that he was able to introduce Jim Cherry to the journal. We wish Stanley every success in his new situation and proffer our sincere thanks for all he has done for VACCINE.
R.E. Spier James Cherry, new editor i decided to resign as US regional editor for V A C C I N E when I took a new position in France. A successor was needed who combined know-
ledge of vaccines with organizational ability and the willingness to add a supernumerary task to their burden. We are fortunate to have Jim Cherry, a friend and colleague. Dr Cherry is Professor of Pediatrics at the University of California, Los Angeles. Jim was born in New Jersey, went to Medical school in Vermont, and had paediatric training in Boston and Brooklyn. In 1953, he went to the University of Wisconsin Departtncnt of Pediatrics, from which he transferred to St Louis University in 1967. In 1973, he went to Los Angeles, where he has since remained. Jim is well known in the field of w~ccines and infectious diseases. He is pre-eminent in the clinical virology of the picornaviruses, having described many of the peculiar syndromes attributable to them. Dr Cherry started studying measles vaccine 20 years ago, raising issues which have become all too familiar during the current resurgence of that disease. The field in which he has probably gained most renown (and most controversy) is that of pertussis vaccine, in which he has undertaken some of the most important studies, and in which he holds strong opinions. To his credit, Jim has not shied away from controversy but has tried vigourously to bring scientific thinking into an emotional area. In addition to his activities on the Redbook Committee of the American Academy of Pediatrics and his current membership of the Advisory Council for Immunization Practices of the US Public Health Service, Dr Cherry is co-editor of the definitive textbook Pediatrics bTfectious
Disease,~'. In handing over the American Editorship to Jim, I am confident he will raise V A C C I N E to new heights of credibility and utility.
Stanley A. Piotkin
extracellular and on which multiplication depends) are rich in antigens which are known to provoke protective antibody responses. Naturally, this route to malaria vaccination has long been promulgated elsewhere 4. The flaw is that a solely asexual stage vaccine probably can not preclude the earliest parasitaemia (which derives from intrahepatic parasites, resulting from the sporozoites inoculated by mosquito bite), and even slight parasitaemia may cause disease and will allow transmission. However, these considerations weigh less against a vaccine for public health use where malaria is endemic than against a 'tourist' vaccine s. Patarroyo's group, parallelling others, dissected the surface antigens of Plasmodium falciparum merozoites immunologically, using natural immune sera as antibody sources. Then, using individual purified extracted antigen preparatons in Aotus, they concluded that immunogens of 83 kDa and 35 kDa induced sterilizing immunity to subsequent challenge and that species of 155 kDa and 55kDa were partially protective. (These molecules have been quite widely investigated elsewhere: see, for instance, Refs 6, 7). Gene cloning and sequencing work was begun for these molecules in Bogota, but when a gene sequence was published elsewhere which the group identified as representing one of their candidates, they narrowed the focus of their own efforts. The group proceeded to synthesise hundreds of peptides represented by these coding sequences, and tested this enormous panel as immunogens in Aotus, after glutaraldehyde coupling to bovine serum albumin. Patarroyo's summing up of this work is that they found no "magic bullets' amongst these synthetic peptides. Fortunately a number of peptide mixtures proved promising: with one, half of the vaccinated monkeys were protected from all disease when Freund's complete adjuvant was used, although 15% had unmodified malaria. This mixture led to the design of the
copolymer SPf(66),, containing three of the peptides with intervening alanine- asparagine-alanine-proline sequences I'3. This motif is the B-cell immunodominant epitope of the P. falciparum sporozoite coat molecule, the CS protein, and has been used as the basis for two malaria vaccines elsewhere 89. Patarroyo states that it is used in SPf(66) monomers to provide hair-pin bends in the synthetic sequence, rather than for its antigenicity. Monomer units are synthesized with both C and N terminal cysteines and polymerize to give products of 25 35 kDa. Patarroyo openly discussed an attempt at the US Center for Disease Control which failed to replicate his results in monkeys with vaccine synthesized there, following his methods 1°. However, in the first Colombian volunteer trial of SPf(66),, which was conducted in military personnel, five out of six vaccinees showed protection 2. In that and in twelve subsequent trials, the Tumaco series, three patterns of response were identified by high, medium and low antibody titre, which were predictive of parasitological outcome. No significant adverse effects of vaccination were described, and AI(OH)3 adjuvant was optimal, with 1 mg doses of polymer given s.c. on days 0, 30 and 180. Field studies are concluded or underway in Colombia, Venezuela, and Brazil. Almost 27000 individuals, now including large numbers of children, have received vaccine. A field trial in The Gambia, based at the MRC Laboratories, Fajara, is under active consideration. There, transmission is potentially more intense than in the South American locations, and background malaria epidemiological information will be further than elsewhere. It was widely felt that the field studies which Patarroyo briefly described had not been strongly designed and could be improved upon. Broadly they suggested efficacy of 50 60%, favourably influenced by prior exposure. A tantalizing finding of protection from P. tfivax as well as P. falciparum emerged from the Las Majadas trial in Venezuela. What then can the non-speciesspecific protective mechanism be?
Vaccine, Vol. 9, April 1991 219
Editorial
Patarroyo presented a clue linked both to this and to the cause of the low responsiveness seen m about 15% of recipients. Two of the antigen's three constituent peptides will directly bind red cells and painstaking work with short peptides has narrowed this to a motif with tyrosine and neighbouring lysineglutamic acid-lysine (single letter code: Y . . . K E K ) . The red cell ligand which they bind was not disclosed to the meeting, but speculation favours Band 3. This may be exploited by the invasion mechanism of both these parasites, and antibody to the Y . . . KEK epitope may be protective for both by preventing their necessary Band 3 interactions (see Ref. 11 for a discussion of invasion). Extraordinarily, an examination of T-cell receptor V fi gene coding sequences in poor responders suggested they shared Y ... KEK motifs (which were absent from better responders), so causing this crucial epitope to pass unrecognized. Patarroyo and Colombia are to be congratulated on this work ; a malaria vaccine has arrived. It is imperfect, but may well deserve the public acclaim it receives in South America. Let us hope for success in Africa.
G.H. Mitchell Department o1 hnmuno/og.t', Medical School, Guy's Hospilal, Lomhm, UK References 1
2
3
4
5
6
7
220
Patarroyo, M.E., Romero, P., Torres, M.L., Clavijo, P., Moreno, A., Martinez, A. eta/. Induction of protective immunity against experimental infection with malaria using synthetic peptides. Nature 1987, 328, 629-632 Patarroyo, M.E., Amador, R., Clavijo, P., Moreno, A., Guzman, F., Romero, P. et al. A synthetic vaccine protects human against challenge with asexual blood stages of Plasrnodium falciparum malaria. Nature 1988, 332, 158 161 Rodriguez, R., Moreno, A., Guzman. F., Calvo, M. and Patarroyo, M.E. Studies in owl monkeys leading to the development of a synthetic vaccine against the asexual blood stages of Plasmodium falciparum. Am. J. Trop. Med. Hyg. 1990, 43, 90 113 Mitchell, G.H. Vaccination against malaria: its plausibility and the present state of research. Vaccine 1984, 2, 11,%124 Mitchell, G.H. An update on candidate malaria vaccines. In: Vaccines and Vaccination Strategies. Symposium of the British Society for Parasitology (Ed. D.J. McLaren) Parasitology 1989, 98, S29~$47 Holder, A.A. The precursor to major merozoite surface antigens: structure and role in immunity. Prog. Allergy 1988, 41, 72 97 Collins, W.E., Pappaioanou, M., Anders, R.F., Campbell, G.H., Brown, G.V., Kemp,
V a c c i n e , Vol. 9, A p r i l 1991
D.J. etal. Immunisation trials with the ring infected erythrocyte surface antigen of Plasmodium talciparum in owl monkeys (Aotus vociferans). Am. J. Trop. Med. Hyg. 1988, 38, 26~282 Herrington, D.A., Clyde, D.F., Losonsky, G., Cortesia, M., Murphy, J.R., Davis, J. et al. Safety and immunogenicity in man of a synthetic peptide malaria vaccine against Plasmodium falciparum sporozoites. Nature 1987, 328, 257 259 Ballou, W.R., Hoffman, S.L., Sherwood, J.A., Hollingdale, M.R.. Neva, F.A., Hockmeyer, W.T. et al. Safety and efficacy of a
10
11
recombinant DNA Plasmodium falciparum sporozoite vaccine. Lancet 1987, i. 1277 1281 Ruebush. T.K., Campbell, G.H., Moreno. A. Patarroyo, M.E. and Collins, W E Immunization of owl monkeys with a combination of Plasmodium falciparum asexual blood-stage synthetic peptide antigens. Am. J. Trop. Med. Hyg. 1990, 43, 90 114 Mitchell. G H and Bannister, L.H. Malaria parasite invasion: interactions with the red cell membrane. Crit. Rev. Oncol. Haematol. 1988, 8, 255 310
CHANGE OF US REGIONAL EDITOR Stanley Plotkin, retiring editor The true test of the strength and value of a state, institution or journal is its ability to thrive whilst experiencing changes in its key people. V A C C I N E is now subject to such a challenge in the retirement of one of its founding editors, Stanley Plotkin. As a party to the inception of the journal, Stanley brought his many talents to bear on the organization of the US editorial office and his high and respected international profile in the world of w~ccines added strength to his efforts. Through his focus on the virus vaccines (he made major contributions to ttle vaccines in current use in the prophylaxis of rubella, cytomegalovirus disease, polio, varicella, rabies and rotavirus infections), he was able to appreciate the contribution of others to the goal of bringing to service new and improved immunoprophylactics. He was able to fulfil one of the essential functions of an editor in supporting and enhancing the quality of many of the contributions submitted for publication. In parallel with the editorial work, his participation in the activities involved in the operation of V A C C I N E was impressive, and his wisdom and dedicated commitment to our full and frank discussions will have a lasting influence. We are pleased that he was able to introduce Jim Cherry to the journal. We wish Stanley every success in his new situation and proffer our sincere thanks for all he has done for VACCINE.
R.E. Spier James Cherry, new editor i decided to resign as US regional editor for V A C C I N E when I took a new position in France. A successor was needed who combined know-
ledge of vaccines with organizational ability and the willingness to add a supernumerary task to their burden. We are fortunate to have Jim Cherry, a friend and colleague. Dr Cherry is Professor of Pediatrics at the University of California, Los Angeles. Jim was born in New Jersey, went to Medical school in Vermont, and had paediatric training in Boston and Brooklyn. In 1953, he went to the University of Wisconsin Departtncnt of Pediatrics, from which he transferred to St Louis University in 1967. In 1973, he went to Los Angeles, where he has since remained. Jim is well known in the field of w~ccines and infectious diseases. He is pre-eminent in the clinical virology of the picornaviruses, having described many of the peculiar syndromes attributable to them. Dr Cherry started studying measles vaccine 20 years ago, raising issues which have become all too familiar during the current resurgence of that disease. The field in which he has probably gained most renown (and most controversy) is that of pertussis vaccine, in which he has undertaken some of the most important studies, and in which he holds strong opinions. To his credit, Jim has not shied away from controversy but has tried vigourously to bring scientific thinking into an emotional area. In addition to his activities on the Redbook Committee of the American Academy of Pediatrics and his current membership of the Advisory Council for Immunization Practices of the US Public Health Service, Dr Cherry is co-editor of the definitive textbook Pediatrics bTfectious
Disease,~'. In handing over the American Editorship to Jim, I am confident he will raise V A C C I N E to new heights of credibility and utility.
Stanley A. Piotkin
