IgG_{4} Pf NPNA-1 a human anti-Plasmodium falciparum sporozoite monoclonal antibody cloned from a protected individual inhibits parasite invasion of hepatocytes

Malaria is one of the world's most devastating diseases, and Plasmodium falciparum (Pf) causes significant mortalities particularly in Sub-Saharan Africa. The rise and spread of multi-drug resistant strains of the parasite has coincided with an era of increased travel to malaria endemic regions. In the absence of an effective vaccine against malaria it may be possible to utilize human monoclonal antibodies against the stage transmitted by mosquito bites (sporozoites) as a prophylactic to prevent infection. We report the characterization of an engineered human IgG_{4} monoclonal antibody against Pf sporozoite cloned from a protected individual recognized the sporozoite surface and inhibited sporozoite invasion of human hepatocytes in vitro. The fully human monoclonal antibody PfNPNA-1 IgG_{4} against (NPNA)_{3} specifically labels Plasmodium falciparum in an IFA. This antibody also inhibits Plasmodium falciparum sporozoite invasion of human hepatocytes HepG2-A16 in a dose dependent manner in an in vitro assay. PfNPNA-1 IgG_{4} is a promising candidate for evaluation for the prevention of malaria

Molecular dissection of the human antibody response to the structural repeat epitope of Plasmodium falciparum sporozoite from a protected donor

BACKGROUND: The circumsporozoite surface protein is the primary target of human antibodies against Plasmodium falciparum sporozoites, these antibodies are predominantly directed to the major repetitive epitope (Asn-Pro-Asn-Ala)(n), (NPNA)(n). In individuals immunized by the bites of irradiated Anopheles mosquitoes carrying P. falciparum sporozoites in their salivary glands, the anti-repeat response dominates and is thought by many to play a role in protective immunity. METHODS: The antibody repertoire from a protected individual immunized by the bites of irradiated P. falciparum infected Anopheles stephensi was recapitulated in a phage display library. Following affinity based selection against (NPNA)(3 )antibody fragments that recognized the PfCSP repeat epitope were rescued. RESULTS: Analysis of selected antibody fragments implied the response was restricted to a single antibody fragment consisting of V(H)3 and V(κ)I families for heavy and light chain respectively with moderate affinity for the ligand. CONCLUSION: The dissection of the protective antibody response against the repeat epitope revealed that the response was apparently restricted to a single V(H)/V(L )pairing (PfNPNA-1). The affinity for the ligand was in the μM range. If anti-repeat antibodies are involved in the protective immunity elicited by exposure to radiation attenuated P. falciparum sporozoites, then high circulating levels of antibodies against the repeat region may be more important than intrinsic high affinity for protection. The ability to attain and sustain high levels of anti-(NPNA)(n )will be one of the key determinants of efficacy for a vaccine that relies upon anti-PfCSP repeat antibodies as the primary mechanism of protective immunity against P. falciparum

Origin and pressure dependence of ferromagnetism in A2Mn2O7 pyrochlores (A=Y, In, Lu, and Tl)

Non-conventional mechanisms have been recently invoked in order to explain the ferromagnetic ground state of A2Mn2O7 pyrochlores (A=Y, In, Lu and Tl) and the puzzling decrease of their Curie temperatures with applied pressure. Here we show, using a perturbation expansion in the Mn-O hopping term, that both features can be understood within the superexhange model, provided that the intra-atomic oxygen interactions are properly taken into account. An additional coupling between the Mn ions mediated by the In(5s)/Tl(6s) bands yields the higher Tc's of these two compounds, this mechamism enhancing their ferromagnetism for higher pressures.Comment: 7 pages and 2 figures submitted to Phys. Rev. B, missing text adde

Modulation of antibody display on M13 filamentous phage

Here we describe a phage vector for the display of single chain antibodies and polypeptides on the surface of filamentous M13 phage which permits facile manipulation of the valency of display. The gene encoding the polypeptide is fused to a synthetic copy of the major coat protein VIII gene (gpVIII) which permits incorporation into the phage during assembly of the filament. Here we examine the growth parameters of phage propagation on the subsequent selection of an anti-progesterone antibody fragment from a mixture of display phage. Our results suggest that the density of the polypeptides displayed on phage may be modulated by altering growth conditions. This ability to influence polypeptide display density on filamentous phage may provide a versatile approach for accessing complex libraries and the capture of weaker ligand receptor interactions by avidity, whilst the potential to access and discriminate between higher affinity interactions is not negated

Validação interlaboratorial do teste de polarização fluorescente para o diagnóstico sorológico da brucelose bovina

Esta investigação teve por objetivo validar o teste de polarização fluorescente (TPF) para o diagnóstico sorológico da brucelose bovina, determinando a sensibilidade (SE) e a especificidade relativas (SP) e verificando a reprodutibilidade do teste em quatro laboratórios no Brasil. Foram selecionadas 1.389 amostras de soro sanguíneo, as quais foram inicialmente submetidas aos testes do antígeno acidificado tamponado (AAT) e mercaptoetanol (2-ME). As mesmas amostras foram submetidas à reação de fixação de complemento (RFC) e ao TPF. Para a avaliação do TPF, foi adotada a combinação dos resultados do AAT, da RFC e do 2-ME, utilizados como população de referência (padrão-ouro). Para a determinação do ponto de corte do TPF que proporciona a melhor combinação de sensibilidade e especificidade, foi usada a análise TG-ROC. A concordância entre os resultados dos quatro laboratórios foi determinada com base no indicador kappa e no coeficiente de correlação de Pearson. Os pontos de corte do TPF situaram-se entre 85,2 e 93,6 mP, conforme o laboratório. A sensibilidade variou de 91,7 a 97,3%, e a especificidade situou-se na faixa de 82,6 a 98,3%. Na comparação entre os resultados do TPF dos quatro laboratórios, o indicador kappa ficou entre 0,69 e 0,95, o que indica, na maioria das situações, reprodutibilidade excelente, e o coeficiente de correlação variou entre 0,76 e 0,99. Os resultados indicaram que o TPF apresentou bom desempenho, na maioria das situações, com sensibilidade e especificidade elevadas. Em comparação com os testes convencionais, o TPF apresenta as vantagens de ser de execução mais rápida e mais fácil e não estar sujeito à ocorrência de prozona, como a RFC e o 2-ME, nem de atividade anticomplementar, como a RFC.The purpose of this research was the interlaboratorial validation of the polarization fluorescence assay (PFA) for the serodiagnosis of bovine brucellosis, verifying the relative sensitivity, the relative specificity and the reproducibility of the test in four Brazilian laboratories. Serum samples from 1,389 bovines were selected and submitted to the rose Bengal (RBT) and 2-mercaptoethanol tests in one of the laboratories. The same samples were tested by the complement fixation (CFT) test and by the PFA in the four laboratories participating of the research. The reference population (golden standard) used to evaluate the PFA was the combination of the results of RBT, CFT and 2-ME. TGROC analysis was used to obtain the cut-off that provided the best combination of sensitivity and specificity. The agreement between laboratories was obtained by the kappa statistic and Pearson correlation coefficient (r). The PFA cut-off values were from 85.2 to 93.6. The sensitivity of the PFA assay varied from 91.7% to 97.3%, and the specificity values varied from 82.6% to 98.3%. When comparing PFA results from the four laboratories, the kappa values was between 0.69 and 0.95, which indicates, in most situations, excellent reproducibility, and the correlation coefficient varied from 0.76 to 0.99. The results showed that the PFA had a good performance, with high sensitivity and specificity. Compared to the conventional tests, the PFA has the advantages of being easy and quick to perform, and it is not prone to the occurrence of prozone, as the CFT or the 2-ME, nor to the occurrence of anticomplementary effect, as the CFT