Extensive Serological Cross-reactivity Research Articles

Cross‐allergic Reactions to Legumes in Lupin and Fenugreek‐Sensitized Mice

Several legumes may induce allergy, and there is extensive serological cross-reactivity among legumes. This cross-reactivity has traditionally been regarded to have limited clinical relevance. However, the introduction of novel legumes to Western countries may have changed this pattern, and in some studies cross-allergy to lupin has been reported in more than 60% of peanut-allergic patients. We wanted to explore cross-reactions among legumes using two newly established mouse models of food allergy. Mice were immunized perorally with fenugreek or lupin with cholera toxin as adjuvant. The mice were challenged with high doses of fenugreek, lupin, peanut or soy, and signs of anaphylactic reactions were observed. Cross-allergic mechanisms were investigated using serum mouse mast cell protease-1 (MMCP-1), antibody responses, immunoblotting and ex vivo production of cytokines by spleen cells. Signs of cross-allergy were observed for all the tested legumes in both models. The cross-allergic symptoms were milder and affected fewer mice than the primary allergic responses. The cross-allergy was reflected to a certain extent in the antibody and T-cell responses, but not in serum MMCP-1 levels. Cross-allergy to peanut, soy, fenugreek and lupin was observed in lupin-sensitized and fenugreek-sensitized mice. Differences in serological responses between primary allergy and cross-allergy might be due to mediation through different immune mechanisms or reflect different epitope affinity to IgE. These differences need to be further investigated.

A Diagnostic Algorithm to Serologically Differentiate West Nile Virus from Japanese Encephalitis Virus Infections and Its Validation in Field Surveillance of Poultry and Horses

The detection of West Nile virus (WNV) in areas endemic for Japanese encephalitis virus (JEV) is complicated by the extensive serological cross-reactivity between the two viruses. A testing algorithm was developed and employed for the detection of anti-WNV antibody in areas endemic for JEV. Using this differentiation algorithm, a serological survey of poultry (2004 through 2009) and horses (2007 through 2009) was performed. Among 2681 poultry sera, 125 samples were interpreted as being positive for antibodies against JEV, and 14 were suspected to be positive for antibodies against undetermined flaviviruses other than WNV and JEV. Of the 2601 horse sera tested, a total of 1914 (73.6%) were positive to the initial screening test. Of these positive sera, 132 sera (5.1%) had been collected from horses that had been imported from the United States, where WNV is endemic. These horses had WNV vaccination records, and no significant pattern of increasing titer was observed in paired sera tests. Of the remaining 1782 positive sera 1468 sera (56.4%) were also found to contain anti-JEV antibodies, and were interpreted to be JEV-specific antibodies by the differentiation algorithm developed in this study. The remaining 314 horses (12.1%) for which a fourfold difference in neutralizing antibody titer could not be demonstrated, were determined to contain an antibody against an unknown (unidentified or undetermined) flavivirus. No evidence of WNV infections were found during the period of this study.

Genetic diversity and antigenic polymorphism in Plasmodium falciparum: extensive serological cross-reactivity between allelic variants of merozoite surface protein 2.

Diversity in the surface antigens of malaria parasites is generally assumed to be a mechanism for immune evasion, but there is little direct evidence that this leads to evasion of protective immunity. Here we show that alleles of the highly polymorphic merozoite surface protein 2 (MSP-2) can be grouped (within the known dimorphic families) into distinct serogroups; variants within a serogroup show extensive serological cross-reactivity. Cross-reactive epitopes are immunodominant, and responses to them may be boosted at the expense of responses to novel epitopes (original antigenic sin). The data imply that immune selection explains only some of the diversity in the msp-2 gene and that MSP-2 vaccines may need to include only a subset of the known variants in order to induce pan-reactive antibodies.

Hypervariable region 1 of hepatitis C virus: immunological decoy or biologically relevant domain?

The hypervariable region 1 (HVR1) of the E2 protein of hepatitis C virus (HCV) is highly heterogeneous and is responsible for significant inter- and intra-individual variation of the infecting virus, which may represent an important pathogenetic mechanism leading to escape and persistent infection. Moreover, a binding site for neutralizing antibodies (Ab) has been allegedly identified in this region. Prospective studies of serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection showed extensive serological cross-reactivity for unrelated HVR1 peptides in the majority of the patients. A significant correlation was found between HVR1 sequence variation, and intensity, and cross-reactivity of humoral immune responses providing strong evidence in support of the contention that HCV variant selection is driven by the host immune pressure. Monoclonal Ab (mAb) generated following immunization of mice with peptides derived from natural HVR1 sequences also showed cross-reactivity for several HVR1 sequences attesting to the existence of conserved amino acid motifs among different variants. These findings suggest that it is possible to induce a broadly cross-reactive immune response to HVR1 and that this mechanism can be used to generate protective immunity for a large repertoire of HCV variants.

Infecção e enfermidade neurológica pelo herpesvírus bovino tipo 5 (BHV-5): coelhos como modelo experimental

Coelhos são susceptíveis à infecção pelo herpes-vírus bovino tipo 5 (BHV-5) e freqüentemente desenvolvem enfermidade neurológica aguda fatal após inoculação intranasal. A cinética da invasão do sistema nervoso central (SNC) de coelhos pelo BHV-5 foi estudada através de pesquisa de vírus em secções do SNC a diferentes intervalos pós-inoculação. Após inoculação intranasal, o vírus foi inicialmente detectado no bulbo olfatório às 48h, seguido do córtex olfatório às 48/72h. Às 72/96h o vírus foi detectado também no gânglio trigêmeo, ponte e córtex cerebral. Dois experimentos foram realizados para avaliar a importância do sistema olfatório na invasão do SNC de coelhos pelo BHV-5. No primeiro experimento, coelhos foram inoculados com duas amostras do BHV-5 no saco conjuntival. Coelhos inoculados por essa via também desenvolveram a enfermidade neurológica, porém com menor freqüência com curso clínico tardio. No segundo experimento, doze coelhos foram submetidos à ablação cirúrgica do bulbo olfatório e posteriormente inoculados com o BHV-5 pela via intranasal. Onze de 12 coelhos controle (91,6%), não submetidos à cirurgia, desenvolveram a doença neurológica, contra quatro de 12 (33,3%) dos animals submetidos à remoção cirúrgica do bulbo olfatório. Esses resultados demonstram que o sistema olfatório constitui-se na principal via de acesso do BHV-5 ao encéfalo de coelhos após inoculação intranasal. No entanto, o desenvolvimento de infecção neurológica em coelhos inoculados pela via conjuntival e em coelhos sem o bulbo olfatório indica que o BHV-5 pode utilizar outras vias para invadir o SNC, provavelmente as fibras sensoriais e autonômicas que compõe o nervo trigêmeo. Os efeitos da imunização com vírus homólogo (BHV-5) e heterólogo (BHV-1) na proteção à infecção neurológica foram investigados. Cinco entre 10 coelhos (50%) imunizados com o BHV-5 apresentaram sinais neurológicos discretos e transitórios e um morreu após o desafio com o BHV-5. Curiosamente, o grau de proteção foi superior nos coelhos imunizados com o BHV-1: apenas dois animais apresentaram sinais clínicos passageiros e recuperaram-se. Portanto, proteção da enfermidade neurológica pelo BHV-5 em coelhos pode ser obtida por imunização com o BHV-5 ou BHV-1, provavelmente devido à extensa reatividade sorológica cruzada entre esses vírus. Estudos adicionais em coelhos podem auxiliar no esclarecimento da patogênese e resposta imunológica a infecção pelo BHV-5.

Antibody responses to hepatitis C virus hypervariable region 1: evidence for cross-reactivity and immune-mediated sequence variation.

Sequence heterogeneity of hepatitis C virus (HCV) is unevenly distributed along the genome, and maximal variation is confined to a short sequence of the HCV second envelope glycoprotein (E2), designated hypervariable region 1 (HVR1), whose biological function is still undefined. We prospectively studied serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection obtained at baseline and after a defined follow-up period. Extensive serological cross-reactivity for unrelated HVR1 peptides was observed in the majority of the patients. Antibody response was restricted to the IgG1 isotype and was focused on the carboxyterminal end of the HVR1 region. Cross-reactive antibodies could be readily elicited following immunization of mice with multiple antigenic peptides carrying HVR1 sequences derived from our patients. The vigor and heterogeneity of cross-reactive antibody responses were significantly higher in patients with chronic hepatitis compared with those with acute hepatitis and in patients infected with HCV type 2 compared with patients infected with other viral genotypes (predominantly type 1), which suggest that higher time-related HVR1 sequence diversification previously described for type 2 may result from immune selection. The finding of a statistically significant correlation between HVR1 sequence variation, and intensity, and cross-reactivity of humoral immune responses provided stronger evidence in support of the contention that HCV variant selection is driven by the host's immune pressure.

The reliability of serological tests for the diagnosis of genital herpes: a critique

The reliability and limitations of the currently used routine tests for herpes simplex virus type 2 (HSV-2) antibody in Australia are reviewed. Six case reports illustrate the clinical dangers of overinterpretation of the currently available kits and the need for a readily available specific HSV-2 antibody test. In Sydney, HSV-2 causes approximately 85% of primary genital herpes and > 95% of recurrent genital herpes. Due to the extensive serological cross-reactivity between HSV-1 and HSV-2, currently available "type specific" commercial assays cannot reliably distinguish between the 2. Isolation of herpes simplex virus (HSV) or detection of HSV antigen in vesicle fluid is the preferred diagnostic test but may be overlooked or patients may have no visible lesions. The only accurate techniques for detecting HSV-2 specific antibody are the Western blot assay and an enzymatic immunoassay using glycoprotein G (gG-2), a component of the HSV-2 envelope. These tests, which still are restricted to research laboratories can be used to accurately identify people with previous exposure to HSV-2 (IgG) or to diagnose primary infection where virus isolation has not been performed or is impossible. Current commercially available antibody tests may have extensive cross-reactivity.

Synthetic peptides of envelope proteins of two different strains of simian aids retrovirus (SRV-1 and SRV-2) represent unique antigenic determinants for serum neutralizing antibodies

There are at least three distinct serotypes of simian type D retrovirus (SRV) which exhibit extensive serological cross-reactivity, but no cross-reactivity exists at the level of serum neutralizing antibodies. Amino acid sequence analysis and hydrophobicity plots of SRV-1 and SRV-2 envelope proteins were compared in order to identify unique potential antigenic determinants to which respective neutralizing antibodies may be directed. Peptides representing residues 147–162 of SRV-1 and 96–102 of SRV-2 were synthesized and assessed for their immunoreactivity. Free peptide inhibition of strain-specific serum (rhesus) neutralizing antibodies to SRV-1 and SRV-2 was demonstrated using the SRV-1 147–162 peptide and the SRV-2 peptide, 96–102, respectively. Inhibition of serum neutralizing activity by these peptides was also strain-specific, showing no cross-inhibition. SRV-1 147–162 conjugated to a protein carrier and cross-linked to Sepharose beads specifically adsorbed neutralizing antibodies from SRV-1 immune rhesus sera. The antibodies eluted from the immunoadsorbent possessed SRV-1 neutralizing activity, but showed no effect on the infectivity of SRV-2. Peptide SRV-1 147–162 also exhibited the capacity to bind specifically with a mouse monoclonal antibody which neutralizes the infectivity of SRV-1. Mice immunized with a recombinant SRV-1 envelope protein or with whole, inactivated SRV-1 produced antibodies which bound the SRV-1 147–162 conjugate, but not the protein carrier itself. Mouse antibodies to the SRV-1 147–162 conjugate exhibited specific binding with both natlve SRV-1 and with recombinant SRV-1 envelope protein. These findings provide strong evidence that SRV-1 147–162 and SRV-2 96–102 constitute at least two unique antigenic determinants, or parts thereof, which participate in the strain-specific neutralizing antibody response. Moreover, the findings indicate that the SRV-1 neutralizing antibodies produced by monkeys and at least a certain population of neutralizing antibodies produced by mice recognize the same epitope of SRV-1.

Mouse monoclonal antibodies reactive with J5 lipopolysaccharide exhibit extensive serological cross-reactivity with a variety of gram-negative bacteria.

We describe two mouse monoclonal antibodies reactive with lipopolysaccharide derived from the J5 mutant of Escherichia coli O111:B4. These antibodies react with purified lipopolysaccharide derived from rough mutants of E. coli and Salmonella typhimurium and also with lipopolysaccharide associated with both smooth- and rough-phenotype, gram-negative bacteria. Both antibodies appear to bind determinants present in the lipopolysaccharide core region, and this reactivity is inhibited in the presence of polymyxin B. Although their patterns of reactivity differ, both antibodies exhibit extensive serological cross-reactivity with a variety of gram-negative bacteria. Reagents of this type should prove useful in animal models to delineate the requisite affinity, epitope specificity, immunoglobulin class, etc., needed for the prevention and treatment of gram-negative bacteremia.