A survey for neutralizing antibodies to the three types of poliovirus among children in Maiduguri, Nigeria

The milestone in polio eradication program is to protect effectively children aged 0–5 years against the three serotypes of poliovirus. It became necessary to measure the level of neutralizing antibodies to the three poliovirus types in an endemic State in Nigeria. Neutralizing antibodies to the poliovirus types among children aged 0–5 years was estimated using micro neutralization assay. Of 129 children, 99 (76.8%), 95 (73.6%), and 95 (73.6%) had neutralizing antibodies with the geometric mean titer of 42.7, 31.3, and 33.2 for the poliovirus type 1, 2, and 3, respectively. Fifty‐three percent of the children were protected against the three types of poliovirus. Combination of poliovirus types 1 and 2, 1 and 3, and 2 and 3 were neutralized by 62.8, 58.9, and 61.2% of the children studied, respectively. Only poliovirus type 1 induced antibody titres ≥1:1,024. The number of children with neutralizing antibodies after receiving three doses was significantly higher than those who received one or two doses of oral polio vaccine (P ≤ 0.05). However, those who received more than three doses of oral polio vaccine showed no significant difference in their antibody response. The existence of immunity gap poses a risk of re‐emergence of the paralytic poliovirus. The existence of unimmunized and unprotected children along with high birth rate could impede the success of polio vaccination in Nigeria. Elimination of non‐compliance to polio vaccine, promotion of health education and documented evidence of vaccination of each child with the parents may facilitate the success of polio eradication program in Nigeria. J. Med. Virol. 84:691–696, 2012. © 2011 Wiley Periodicals, Inc.     

Poliovirus serotype 2 and coxsackievirus A promote the natural recombination of poliovirus

Poliovirus (PV) is a member of the species Enterovirus C (EV-C), which may cause irreversible paralysis and death. So, for the purpose of analyzing the evolution of PV2 to help in eradicating PVs globally, a recombination analysis was performed to verify all viral genomes of EV-C, and we found 13 putative recombination events that produced PV1, 14 recombination events that can give rise to PV2, and 9 events that can lead to PV3. By analyzing our findings, we found that PV2 was involved in 25 of 36 PV recombination events, whereas coxsackievirus A (CVA) strains were involved in 12 of 36 PV recombination events, indicating that PV2 and CVAs play major roles in the natural recombination of PV. In addition, we found 11 of 36 breakpoint positions located in 2A region, which is the most active region of the recombination events.     

三种呼吸道病毒实验室检测方法比较

目的在3种呼吸道多病原检测方法中筛选出敏感的实验室检测方法。方法以73份上呼道感染病例咽拭子标本作为检测对象,利用3种呼吸道多病原病毒检测方法,对17种呼吸道病毒检测指标进行平行检测,根据不同呼吸道病毒检测指标检出率,评价3种试剂检测效果。结果自建RT-PCR及PCR检测方法共检出56个阳性指标,市售多重RT-PCR检测试剂盒共检出41个阳性指标,市售多重实时荧光RT-PCR检测试剂盒共检出87个阳性指标。结论多重实时荧光RT-PCR检测试剂盒具有更高的检出率,可用于呼吸道多病原病毒的实验室检测。     

A seroprevalence study of poliovirus antibody in the population of northern Greece

This study assessed immunity to poliomyelitis in a representative sample of 1064 persons living in northern Greece. Antibody prevalences in the individuals tested were 91.1% (95% confidence interval (CI): 89.4-92.8), 92.1% (95% CI: 90.5-93.7) and 83.1% (95% CI: 80.8-85.4) for poliovirus types 1, 2 and 3, respectively. For poliovirus type 3, a gap in immunity was found in individuals aged 10-29 years. Re-vaccination of adolescents living in northern Greece is suggested to ensure herd immunity and to minimise the risk of importation of wild poliovirus from endemic countries.     

A simple quantitative protein A micro-immunoprecipitation method; assay of antibodies to the N and H antigens of poliovirus

Staphylococcus aureus (Cowan strain I) was used to absorb immune complexes from antiserum to poliovirus to which labeled N or H poliovirus antigens had been added, and the radioactivity in the pelleted organisms and in the supernatant was measured. Excellent agreement was obtained between values calculated separately from the pellet and supernatant readings, validating the use of supernatant measurements from a microtitration plate method.     

Comparative study of molecular and antigenic characterization for intratypic differentiation (ITD) of poliovirus strains

This study was designed to compare the sensitivity of a Sabin vaccine strain‐specific PCR assay and an enzyme‐linked immunosorbent assay with polyclonal cross‐absorbed antisera (PAb‐E) for intratypic differentiation (ITD) of polioviruses (PVs). These were used for the definitive characterization of the strains. Poliovirus strains isolated in L20B and RD cell lines were subjected to both PCR and ELISA. Both PCR and ELISA identified 3 (13.6%) out of 22 isolates, respectively as poliovirus Sabin 1. PCR identified 4 (18.2%) out of 22 isolates as poliovirus Sabin 2 and ELISA identified 2 (9.1%) out of 22 isolates as poliovirus Sabin 2. None of the two assay identified poliovirus Sabin 3. Both PCR and ELISA identified 12 (54.5%) out of 22 isolates, respectively as wild poliovirus (WPV) 1. None of the assays identified any of the isolates as WPV 2 and 3. Only PCR assay was able to identify the mixture of two poliovirus Sabin serotypes (a mixture of Sabin 1 and 2) and two mixtures of poliovirus Sabin 2 and 3. In this study, only ELISA was able to identified two invalid results. Invalid results observed in this study are of important practical implication to the emergence of vaccine‐derived poliovirus. This may have epidemic potential. Hence, the two ITD assays are of paramount importance for identification of PVs. It is therefore recommended in line with WHO guideline that at least two methods be used for the ITD of poliovirus isolates, and each method should be based on a different principle (i.e., antigenic and genetic properties). J. Med. Virol. 84:1975–1979, 2012. © 2012 Wiley Periodicals, Inc.     

A群链球菌疫苗的研究进展

A群链球菌(GAS),是革兰氏染色阳性致病菌,是引起人类感染最常见的致病菌之一,导致全球每年约50万的死亡人数,用于治疗的费用也成了不小的经济负担.目前,GAS感染治疗策略依旧是使用合适的抗生素如青霉素,但在一些地区,抗生素针对某些血清型的作用效果十分有限,已不能很好地控制疾病.因而,研发出安全、有效的商品化GAS疫苗从而达到预防和控制感染的目的是近些年来GAS研究的重点.目前,已经有一些GAS的候选疫苗进入了临床评估阶段,因而对疫苗作用机制进行研究具有重要意义.     

Reprodueibility of the color test for titration of poliovirus

Summary The dose-response relationship for poliovirus, when determined by the color test, using various cell lines and first sub-culture monkey kidney cells, follows the prediction for one-particle infection. The inter-assay standard deviation for mean log tolerances is 0.079 log units when based on the use of 0.3-log dilution intervals and 16 tubes per dilution; that based on 0.5 log intervals is 0.113; and that based on 1.0-log intervals is 0.155. The standard deviation for numbers of cytopathogenic units per ml., based on single dilutions with 128 tubes per dilution, is 0.079 log units. Close correspondence between these standard deviations and those observed elsewhere with other viruses and other test systems suggests general applicability of the findings.     

Comparative study of poliovirus excretion after vaccination of infants with two oral polio vaccines prepared on vero cells or on primary monkey kidney cells

A comparative study was designed to assess the bioequivalence of 2 oral poliovaccines (OPV) produced on 2 different cell systems: primary monkey kidney (PMK) cells and the Vero cell line. The Vero cell line has been used to overcome the problem of obtaining a regular supply of high quality monkeys that are devoid of latent viruses. For this study, 9 children were vaccinated with PMK-OPV and 12 children with Vero-OPV. The comparison covered poliovirus excretion, reversion of polioviruses in the 5′-noncoding region, and immunogenicity. Major molecular markers in the 5′-noncoding region related to neurovirulence already had been identified at position 480 for type 1, position 481 for type 2, and position 472 for type 3 poliovirus. Two nucleic-acid based methods were designed for studying these positions: a RT-PCR followed by sequencing, which required preliminary culture and cloning; and a type-specific nested PCR followed by sequencing, which enabled direct detection and genotyping of polioviruses. Twenty-eight stool specimens were analyzed by this second method with no PCR inhibition problem. The use of Vero cell line did not modify the global pattern of poliovirus excretion, reversion frequency, or seroconversion. These results provide additional support for the use of the well-characterized Vero cell line in OPV manufacturing. J. Med. Virol. 52:50–60, 1997. © 1997 Wiley-Liss, Inc.     

Comparison of culture,single and multiplex real‐time PCR for detection of Sabin poliovirus shedding in recently vaccinated Indian children

Although, culture is considered the gold standard for poliovirus detection from stool samples, real‐time PCR has emerged as a faster and more sensitive alternative. Detection of poliovirus from the stool of recently vaccinated children by culture, single and multiplex real‐time PCR was compared. Of the 80 samples tested, 55 (68.75%) were positive by culture compared to 61 (76.25%) and 60 (75%) samples by the single and one step multiplex real‐time PCR assays respectively. Real‐time PCR (singleplex and multiplex) is more sensitive than culture for poliovirus detection in stool, although the difference was not statistically significant.

     

A comparison of three methods for detecting antibodies to turkey rhinotracheitis virus

Sera from a flock of naturally infected commercial turkeys were tested for antibodies against turkey rhinotracheitis virus using an indirect immunofluorescence test with infected turkey embryo tracheal organ cultures, a serum neutralisation test using chick embryo fibro-blasts or liver cells and an ELISA. Antibodies were detected by all tests within 5 days of the appearance of clinical respiratory disease. Serum neutralising antibodies detected in chick embryo fibroblasts rapidly achieved their peak titres and were decreasing by day 13. ELISA antibodies peaked on day 13. On days 13 and 34 significant correlations were obtained for immunofluorescence and ELISA and for ELISA and microneutralisation in fibroblasts. For both the latter tests there was a good correlation between the results obtained for individual birds within the flock on days 13 and 34. ELISA and serum neutralisation in chick embryo fibroblast monolayers would appear to be sensitive and reliable tests for detecting circulating antibodies against turkey rhinotracheitis virus in commercial flocks.     

Isolation and characterisation of poliovirus mutants resistant to heating at 50 degrees Celsius for 30 min

Poliovirus is heat-labile; on heating at 50 degrees Celsius for 30 min its infectivity decreases drastically and its antigenicity reverts from N to H. However, mutants resistant to heating at 50 degrees Celsius for 30 min from the Sabin 1 and 2 viruses were isolated by repeating the process of incubation of the virus stock at 50 degrees Celsius for 30 min and multiplication of the remaining virus in a cell culture. The isolated mutants were stable genetically, and maintained the rct and d markers of the parent virus. On electron microscopical examination, the mutants were observed to retain the intact morphology after being heated at 50 degrees Celsius for 30 min, while the parent virus was converted to empty particles devoid of RNA under the same conditions. On determination of the nucleotide sequence of the P1 region, a single nucleotide sequence substitution was detected at nucleotide no. 2741, resulting in an amino acid change from valine to alanine at the 87th position of VP1. This amino acid might be associated with the heat-resistance of the mutants. Furthermore, it was found that the thermostable mutants obtained in this study, which are resistant to "high" temperature (50 degrees Celsius) for a short time (30 min), were not stable against heating at the ambient temperature (37 degrees Celsius) for a long time (5 or 7 days). This suggests that the inactivation at high temperature for a short time and that at ambient temperature for a long time involve different mechanisms.     

A rapid method for infectivity titration of Andes hantavirus using flow cytometry

The focus assay is currently the most commonly used technique for hantavirus titer determination. This method requires an incubation time of between 5 and 11 days to allow the appearance of foci after several rounds of viral infection. The following work presents a rapid Andes virus (ANDV) titration assay, based on viral nucleocapsid protein (N) detection in infected cells by flow cytometry. To this end, an anti-N monoclonal antibody was used that was developed and characterized previously. ANDV N could be detected as early as 6 h post-infection, while viral release was not observed until 24–48 h post-infection. Given that ANDV detection was performed during its first round of infection, a time reduction for titer determination was possible and provided results in only two days. The viral titer was calculated from the percentage of N positive cells and agreed with focus assay titers. Furthermore, the assay was applied to quantify the inhibition of ANDV cell entry by patient sera and by preventing endosome acidification. This novel hantavirus titration assay is a highly quantitative and sensitive tool that facilitates infectivity titration of virus stocks, rapid screening for antiviral drugs, and may be further used to detect and quantify infectious virus in human samples.     

Whole parasite vaccines for the asexual blood stages of Plasmodium

After many decades of research, an effective vaccine for malaria is still not available. Most research efforts have focused on identifying a key target antigen and then using powerful adjuvants to generate specific antibodies that can block parasites from entering host cells (hepatocytes, red blood cells). However, the inability to generate sufficiently potent antibody responses has led to significant disappointment with current vaccine programs. An additional challenge for sub-unit vaccines is that key vaccine antigens are highly polymorphic. These challenges have spurred radically different approaches to malaria vaccine development. Many of these involve the use of “whole parasites”—either extracted from mosquitoes or cultured. With these, every parasite molecule for that particular strain is included in the vaccine. This strategy is showing great promise following several clinical trials with irradiated sporozoites. However, a whole-parasite approach to a blood stage vaccine has not advanced as quickly. This article outlines the history, the different approaches that are being taken and the challenges associated with whole parasite blood stage vaccines and discusses recent exciting developments as these vaccines now move into the clinic.     

A comparison of three methods of diagnosis of infectious laryngotracheitis

Three methods of isolation of ILT virus are compared. Examination of tracheas from sick birds by means of direct immunofluorescence detects about 60% of the cases detected by viral isolation in chick kidney cells or in embryonating eggs. The coupling of direct immunofluorescence on tracheal sections with viral isolation and immunofluorescence in CK cells is a good practical method to detect an ILT infection in sick birds.     

A comparison of three methods for detecting the acrosome reaction in human spermatozoa

This study was designed to compare three different fluorescentprobes to assay the acrosome reaction in human spermatozoa:chlortetracycline (CTC), mannosylated bovine serum albumin (BSA)labelled with fluorescein (MAF), and quinacrine (QN)- Normalhuman sperm ejaculates were washed and allowed to swim up for30–60 min. Samples were examined under epifluorescencefor the percentage of the acrosome reacted spermatozoa, as detectedby the three probes. There was no significant difference betweensamples of fresh, uncapadtated spermatozoa evaluated with CTC,MAF or QN; all gave <10% reacted. Following capacitationfor 3 h, the percentage of spontaneously reacted spermatozoawas higher than in fresh spermatozoa; CTC and MAF gave the samepercentage (12%), while QN indicated a higher percentage (18%)of reacted spermatozoa (P < 0.001). Following exposure toionophore A23187 at 1 h, the percentage of acrosome reactionsincreased to a mean of 31% as detected with CTC or MAF; themean percentage (45%) was significantly higher with QN (P <0.0001). Further incubation up to 2 h with A23187 did not changethese percentages. These results suggest that the QN probe detectsthe onset stage of the acrosome reaction, whereas the CTC andMAF probes detect the later stages in which the acrosomal capis lost. Use of the two types of probe provides a means forfiner resolution of the time course of the acrosome reactionin the human spermatozoa.