Persistence of vaccine-derived poliovirus following a mass vaccination campaign in Cuba: implications for stopping polio vaccination after global eradication.

BACKGROUND: With substantial progress made toward polio eradication, developing the appropriate strategy for discontinuing global oral poliovirus vaccine (OPV) after global eradication becomes increasingly important. At issue is the theoretical risk of independent circulation of potentially virulent OPV-derived strains. Because Cuba uses OPV only in mass campaigns, it represents an ideal site to assess vaccine-derived poliovirus persistence. METHODS: Infants born after the 1997 biannual mass campaigns were evaluated for past (neutralizing antibody) or current (virus excretion) evidence of vaccine-derived poliovirus exposure. We obtained sera and/or stool specimens from 861 infants; a second serum from 218 infants. RESULTS: All stool specimens were poliovirus negative. Of 762 infants, 113 (14.8%) had initially detectable poliovirus type 1 antibody, 193 (25.3%) type 2, and 94 (12.3%) type 3. A precipitous antibody decline occurred in initially positive sera. CONCLUSIONS: Our results suggest that in a country with high population immunity, vaccine-derived virus is unlikely to establish ongoing circulation.

Acyclovir resistant genital herpes virus infection in a patient with AIDS.

Three acyclovir resistant strains of HSV-2 were isolated from mucoulcerative lesions in a patient suffering from AIDS in whom the oral and intravenous acyclovir treatment was unsuccessful. All the isolates were classified by monoclonal antibodies and showed no differences in DNA restriction patterns.

[Genetic changes in strains of poliovirus type 2 isolated from patients with vaccine-associated paralytic poliomyelitis]. / Cambios geneticos en cepas de poliovirus tipo 2 aisladas de pacientes con poliomielitis paralitica asociada a la vacuna.

INTRODUCTION: Poliomyelitis is currently a rare disease in developed countries, where only vaccinal strains seem to be in circulation, which replace wild poliovirus. Nevertheless, it is still a serious disease for children in underdeveloped countries of Asia and Africa. PATIENTS AND METHODS: We analysed nine strains of poliovirus type 2 isolated from the faecal matter of patients with vaccine associated paralytic poliomyelitis (VAPP), from the beginning of anti polio vaccination campaigns in our country. These strains were submitted to sequencing of a fragment of 114 base pairs from the 5 NTR (non traductional region), where one of the main determinants of attenuation/reversion to the neurovirulence of poliovirus lies in the position of nucleotide 481. RESULTS: In this position it was observed how guanine had been replaced by adenine in all the strains that were sequenced, so that it coincided with the homologous sequence of the wild strain, as well as with that of strains obtained from healthy children immunised with the live vaccine. This presupposes that other changes must occur or that other factors must be involved for VAPP to occur or not, and we therefore suggest the sequencing of other regions of the genome in search of other possible differential changes in nucleotides.

Eradication of poliomyelitis in Cuba: a historical perspective.

The eradication of poliomyelitis in Cuba, for which effective vaccines had to be acquired, is reviewed in this article. The strategy for eradication was based on mass immunization campaigns for the annual delivery of two doses of trivalent Sabin oral poliovirus vaccine (OPV). Except during the first campaign in 1962, the ages of the children for immunization were determined through national serological surveys of the entire country, including rural and urban areas. The interruption of wild virus transmission had been suspected since 1967 in Cuba, and since 1970 no studies have detected any wild virus. The important role of political and social organizations in the success of the programme and in the execution of the mass immunization campaigns is underscored. Countries that have successfully interrupted poliovirus circulation should maintain high immunization coverage for as long as there are other countries in the world where poliovirus still exists.

[Epidemic neuropathy. An etiopathogenetic hypothesis]. / Neuropatía epidémica. Hipótesis etiopatogénica.

An etiopathogenic hypothesis is explained taking into consideration the most significant results of the research performed on neuropathy as well as the latest knowledge about the infections produced by Enterovirus. The hypothesis allows to make a logical interpretation of these results; however, the new aspects included make it controversial in the light of the present knowledge to pathogeny by Enterovirus. Further research is needed to confirm this hypothesis.

[Outbreak of Coxsackievirus B5 meningoencephalitis in Cuba, 1995]. / Brote de meningoencefalitis por coxsackievirus B5 en Cuba, 1995.

An increase in the reported cases of viral meningoencephalitis (VME) was detected in October and November, 1995, compared with the same period of 1994. 43 stock specimens from children with this diagnosis were received at the Laboratory of Enterovirus from the "Pedro Kourí" Institute of Tropical Medicine. 23 isolations (53.4%) were obtained and identified as Coxsackievirus B5. Besides, in 43 matched sera investigated by the neutralization test against some Enteroviruses, 21 proved to be positive (48.8%) to the isolated agent. This allowed us to affirm, supported by the clinical picture and by epidemiology, that we are in the presence of an VME outbreak produced by Coxsackievirus B5.

[Comparison of latex agglutination technics and polyacrylamide gel electrophoresis for the rotavirus diagnosis. Habana City, 1986]. / Comparación de las técnicas de aglutinación por latex y la electroforesis en gel de poliacrilamida para el diagnóstico de rotavirus. Ciudad de la Habana, 1986.

Two methods for the diagnosis of rotavirus are compared with 120 stool samples from children under two years of age who had been hospitalized in Centro Habana Children's Hospital with a clinical diagnosis of acute diarrheal disease and 30 samples of healthy children of the same age group who served as controls. The methods used were latex agglutination (Rotalex, commercially-available kit from ORION DIAGNOSTIC ESPOO, Finland) and polyacrylamide gel electrophoresis. Electronic microscopy was used to define those cases whose results did not coincide with the previous techniques. Comparison was made based on the sensitivity and specificity, cost and easiness of performance. Rotalex was less specific but more sensitive than electrophoresis in polyacrylamide gel. The latter is less expensive, since reactants are available at a lower price in dollars and have no expiration date, is very useful in epidemiologic and outbreak studies, since it detects subgroups of circulating rotavirus and it is a painstaking technique (1-20 samples in 10 hours). Rotalex is simple, rapid (1-20 samples in 30 minutes) and allows individual determinations; therefore, we consider its application in hospitals is feasible.

[Standardization of an inhibition ELISA technique for the serologic diagnosis of coxsackie virus group B infections]. / Normalización de un ELISA de inhibición para el diagnóstico serológico de las infecciones por virus coxsackie del grupo B.

An inhibition ELISA technic to detect antibodies aimed at Coxsackie B viruses was standardized. The method was type-specific since it could detect antibodies to 4 Coxsackie B serotypes (it wasn't tried on serotypes B2 and B4 because the strains were not available). The comparison with the neutralization technic showed 85% coincidence, 91% sensitivity and 82% specificity. All the reactives used in the assay were produced in our laboratory.

[Cuban epidemic neuropathy. II. The antigenic characteristics of the viral isolates]. / Neuropatía epidémica cubana. Parte II. Algunas características antigénicas de los aislamientos virales.

With the aim of characterizing antigenically isolations producing mild cytopathogenic effect obtained from the cerebrospinal fluid of patients presenting with epidemic neuropathy, neutralization tests and western blot analysis were performed using hyperimmune sera of patients and hyperimmune sera of rabbits. It was confirmed that isolations with mild cutopathogenic effect studied have the same antigenic characteristics and that they are related to Coxsackie A9 and B4 viruses. Structural proteins were not detected in the strains with mild cytopathogenic effects, only antigens having a high molecular weight which were considered as precursor proteins for viral replication were confirmed.

[Factors associated with the incurability of epidemic neuropathy in Cuba]. / Factores asociados a la no curabilidad de la neuropatía epidémica en Cuba.

56 patients were surveyed and reexamined at the Center for Medical and Surgical Research (CMSR) a year after the onset of the neuropathy epidemic. The possible factors associated with the occurrence were investigated to be studied together with the disease persistence, including the antibody titre of 33 of them, who had a previous serology against the biological agent (strain 47/IPK) isolated from the cerebrospinal fluid of a sick patient. A fourth of the patients (15 cases) were still ill. The loss of weight and the smoking habit were stressed as the factors most associated with the persistence of the clinical manifestations of epidemic neuropathy. In spite of the fact that the small number of patients who underwent the checkup limited the study, this is a basic document about the existent situation a year after the problem happened.

[Detection of immunoglobulin A in serum and saliva of patients with hepatitis A]. / Detección de inmunoglobulina A en suero y saliva de pacientes con hepatitis A.

Specific secretory serum IgA antibodies to the hepatitis A virus from samples from patients with clinical symptoms compatible to hepatitis A, their contacts, and healthy subjects were analyzed using an ELISA technique; results were compared with those of specific serum IgM antibodies to the hepatitis A virus. The following results were attained in 175 blood samples: coincidence by 98.8%; sensitivity by 96.8%; and specificity by 100%. Two cases were negative to IGA and positive to IGM. On comparing the presence of IGA in saliva with the presence of IGM in blood, coincidence was of 88.1%; sensitivity, of 40.9% and specificity, of 100%. Of the 22 cases with positive IGM in blood, only 9 showed specific IGA antibodies in the saliva. The 111 cases who had negative IGM in blood were also negative to IGA. The obtained data suggest that specific serum IGA antibodies to the hepatitis A virus are an indicator of a recent or occurrent infection due to this virus and thus it may be considered and alternative for the diagnosis of this disease.

[Outbreaks of hepatitis A in the City of Havana in the year 1991]. / Estudio de brotes de hepatitis A ocurridos en Ciudad de La Habana en el año 1991.

Fifty-six outbreaks of hepatitis A infection were studied in City of Havana between January and September, 1991. In 34 of these, the presence of the hepatitis A virus (HAV) was confirmed, either by the detection of specific serum IGM antibodies to the HAV or by the detection of the antigen in the feces of the subjects under study. Diagnosis was not made in some of the outbreaks due to the insufficient number of samples sent to the laboratory. Of the 453 blood serum samples under study, 126 were positive for IGM antibodies to HAV (27.8%): a there was a good correlation between the presence of this immunoglobulin and the levels attained by the alanyl aminotransferase enzyme (ALT). Only in 19 feces samples, of the 263 under study, was the HAV antigen detected, which accounted to 7.2%; it was demonstrated that this marker is not useful for the diagnosis of an outbreak of hepatitis A infection.

[Purification and proteic characterization of a Cuban strain of the hepatitis A virus]. / Purificación y caracterización proteica de una cepa cubana del virus de la hepatitis A.

The purification and protein characterization of one of the Cuban isolated strains of hepatitis A virus was carried out. For this, it was necessary to separate the virus from the infected cell by extraction steps with detergents, concentration by ultrafiltration and finally, ultracentrifugation in saccharosoglycerol discontinuous gradient. Protein concentration, as well as the antigenic activity in the different fractions of the gradient were determined. For the protein characterization of the microorganism, those fractions with the greatest specific activity were analyzed by polyacrylamide gel electrophoresis and by Western blotting. It was shown that the viral material was purified and concentrated in the last fractions of the gradient. Bands corresponding to the structural proteins of hepatitis A were observed through electrophoresis and Western blotting.

[Serologic marker as indicator of no circulation of poliovirus in Cuba]. / Marcador serológico como indicador de no circulación de poliovirus en Cuba.

The surveillance of the circulation of the wild poliovirus is an essential element for the eradication of poliomyelitis. The Pan-American Health Organization emphasises on the etiological study of acute flaccid paralysis in order to achieve this aim. The characteristics of our program against this entity allowed to use the presence of antibodies in a sample obtained in February from the infant population born on July during the previous year as criteria to know the circulation of wild poliovirus. In 727 infants studies in the country (5% of the total number of births during July), 99.1% showed no antibodies with a titre equal or greater than 1:10. Low titres found in 7 infants were considered as a remnant from maternal transmission. Results obtained represent a strong evidence of the fact that there is no environmental circulation of poliovirus during the period which had the greatest incidence of the disease.

[Virologic diagnosis of an outbreak of epidemic hemorrhagic conjunctivitis by an indirect immunofluorescence technique. Cuba.1989]. / Diagnóstico virológico de un brote de conjuntivitis hemorrágica epidémica mediante la técnica de inmunofluorescencia indirecta. Cuba, 1989.

The causative agent of an hemorrhagic conjunctivitis outbreak was assessed through the study of 18 conjunctival exudates using the indirect immunofluorescence technique and isolation in cell culture of human embryo fibroblasts. In addition, 395 paired serum samples were studied and Enterovirus 70 was found to be responsible for the outbreak.

[Cuban epidemic neuropathy. I. Viral isolation]. / Neuropatía epidémica cubana. Parte I. Aislamiento viral.

From the end of 1991 to June, 1993, an epidemic neuropathy affecting 50,963 persons occurred in Cuba. Two clinical forms of the disease were observed: the optic form (with or without peripheral manifestations, 52% of the cases) and the peripheral form (48%). The epidemiological studies revealed nutritional disorders, mainly a vitamin B complex deficiency due to economic difficulties faced by the country in the "special period". Smoking habit and alcohol consumption were identified as risk factors, particularly for the most severe forms of the disease. In the virological studies of the cerebrospinal fluid (CSF) a Coxsackie 9 virus was isolated in Vero cells in 4% of the cases, as well as another agent with mild cytopathogenic effect in 80% of the samples. Sixty seven percent of the CSF samples inoculated to lactating mice caused the disease or the death of the animals. The viral persistence was confirmed in the cerebrospinal fluid during al least 21 days in a group of patients, and for a year in another group.

[Cuban epidemic neuropathy. III. Neutralizing antibodies to the strains isolated and to other enteroviruses in patients and healthy subjects]. / Neuropatía epidémica cubana. Parte III. Anticuerpos neutralizantes a cepas aisladas y otros Enterovirus en pacientes y personas sanas.

Determinations of neutralizing antibodies to the strain 47/93 IPK (CA9) and to the strain 590 were performed in serum samples from patients presenting with epidemic neuropathy and from a group of seemingly healthy subjects. Determinations were also done in the reference strains CA9 and CB1-6 by the microneutralization technique. Patients and their contacts showed significantly higher percentages of neutralizing antibodies to the strain 47/93 than the control group and residents of municipalities with a low rate of the disease. This difference was also confirmed regarding the geometric mean titres with the use of the reference strains CA9 and CB2-4. An increased circulation of the strain 47/93 within the infantile population from 1981 to 1993 was evidenced. Patients exhibited significantly lower percentages and geometric mean titres of neutralizing antibodies to the strain 590 than the control group, despite the fact that in 25/28 certain agents having a mild cytopathogenic effect had been isolated. The possibility of two mechanism of neutralization is stated and an hypothesis on the mechanism by which these viruses may be involved in the pathophysiology of the disease is formulated.

[Cuban epidemic neuropathy. IV. The antigenic relationship of the viral isolates to the structures of the central nervous system. A possible etiopathogenic mechanism?]. / Neuropatía epidémica cubana. Parte IV. Relación antigénica de los aislamientos virales con estructuras del sistema nervioso central. Posible mecanismo etiopatogénico?

Results which allow to state the existence of antigenic relationships between viruses isolated from the cerebrospinal fluid of patients presenting with epidemic neuropathy and structures of the human central nervous system are reported. These evidences were obtained by 2 different and independent ways: 1) by the double diffusion method in agarose, immunoblot analysis, and immunohistochemical analysis it was confirmed that antibodies induced by isolated viruses react with antigens of the central and peripheral nervous system, 2) serum obtained by the immunization of a rabbit with human brain extract neutralizes the same viruses as those neutralized by hyperimmune sera obtained by isolations. The possible role of viruses as mediators of an autoimmune process in the pathogenesis of the disease is discussed.