Mapping of epitopes and structural analysis of antigenic sites in the nucleoprotein of rabies virus

Rabies virus in slaughtered dogs for meat consumption in Ghana: A potential risk for rabies transmission

Dog-mediated rabies is responsible for approximately 60,000 human deaths annually worldwide. Although dog slaughter for human consumption and its potential risk for rabies transmission has been reported, mainly in some parts of Western Africa and South-East Asia, more information on this and factors that influence dog meat consumption is required for a better understanding from places like Ghana where the practice is common. We tested 144 brain tissues from apparently healthy dogs slaughtered for human consumption for the presence of rabies viruses using a Lyssavirus-specific real-Time RT-PCR. Positive samples were confirmed by virus genome sequencing. We also administered questionnaires to 541 dog owners from three regions in Ghana and evaluated factors that could influence dog meat consumption. We interacted with butchers and observed slaughtering and meat preparation procedures. Three out of 144 (2.1%) brain tissues from apparently healthy dogs tested positive for rabies virus RNA. Two of the viruses with complete genomes were distinct from one another, but both belonged to the Africa 2 lineage. The third virus with a partial genome fragment had high sequence identity to the other two and also belonged to the Africa 2 lineage. Almost half of the study participants practiced dog consumption [49% (265/541)]. Males were almost twice (cOR = 1.72, 95% CI (1.17-2.52), p-value = .006) as likely to consume dog meat compared to females. Likewise, the Frafra tribe from northern Ghana [cOR = 825.1, 95% CI (185.3-3672.9), p-value < .0001] and those with non-specific tribes [cOR = 47.05, 95% CI (10.18-217.41), p-value < .0001] presented with higher odds of dog consumption compared to Ewes. The butchers used bare hands in meat preparation. This study demonstrates the presence of rabies virus RNA in apparently healthy dogs slaughtered for human consumption in Ghana and suggests a potential risk for rabies transmission. Veterinary departments and local assemblies are recommended to monitor and regulate this practice.

Development of Monoclonal Antibodies for Detection of Conserved and Variable Epitopes of Large Protein of Rabies Virus

Rabies virus (RABV) causes fatal neurological encephalitis and results in approximately 6000 human death cases worldwide every year. The large (L) protein of RABV, possessing conserved domains, is considered as the target for detection. In this study, three monoclonal antibodies (mAbs), designated as 3F3, 3A6 and L-C, against L protein were generated by using the recombinant truncated L protein (aa 1431-1754) and the epitopes were also identified using a series of overlapping truncated polypeptides for testing the reactivity of mAbs with different RABV strains. The ¹⁴⁷⁹EIFSIP¹⁴⁸⁴, ¹⁶⁵⁹RALSK¹⁶⁶³ and ¹⁷²⁴VFNSL¹⁷²⁸ were identified as the minimal linear epitopes recognized by mAbs 3F3, 3A6 and L-C, respectively. Amino acid alignment showed epitope ¹⁷²⁴VFNSL¹⁷²⁸ recognized by mAb L-C is completely conserved among RABV strains, indicating that mAb L-C could be used to detect all of the RABV strains. Epitope ¹⁴⁷⁹EIFSIP¹⁴⁸⁴ is highly conserved among RABV strains except for a P1484S substitution in a China I sub-lineage strain of Asian lineage, which eliminated the reactivity of the epitope with mAb 3F3. However, the epitope ¹⁶⁵⁹RALSK¹⁶⁶³ was only completely conserved in the Africa-2 and Indian lineages, and a single A1660T substitution, mainly appeared in strains of the China I belonging to Asian lineage and a Cosmopolitan lineage strain, still retained the reactivity of the epitope with mAb 3A6. While both A1660T and K1663R substitutions in a China I lineage strain, single K1663R/Q substitution in some China II strains of Asian lineage and some Arctic-like lineage strains and R1659Q mutation in a strain of Africa-3 lineage eliminated the reactivity of the epitope with mAb 3A6, suggesting mAb 3A6 could be used for differentiation of variable epitopes of some strains in different lineages. Thus, variability and conservation of the three epitopes of L protein showed the reactive difference of mAbs among RABV strains of different lineages. These results may facilitate future studies in development of detection methods for RABV infection, the structure and function of RABV L protein.

Antigenic site of nucleoprotein gene from Indonesian rabies virus isolates

BACKGROUND AND AIM

Several molecular studies on rabies virus (RABV) have been conducted in Indonesia, but it does not give clear information about molecular characteristics of previous RABV isolate in Indonesia. This study was conducted to know the characteristic of circulating RABV to determine a suitable method to control the spreading of RABV in Indonesia.

MATERIALS AND METHODS

Samples of infected RABV from dog brain were collected from Sumatera, Kalimantan, Sulawesi, and Bali Islands. All samples were examined based on nucleoprotein encoding gene to determine the molecular characteristics based on homology and phylogenetic tree compared to Pasteur Virus and RABV that came from another country within Asia (Indonesia, China, Thailand, India, and Korea). The collected samples were processed by one-step reverse transcriptase-polymerase chain reaction using nucleoprotein encoding gene followed by sequencing. The amino acid of its antigenic site of isolated RABV was also analyzed.

RESULTS

The results showed that isolated RABV has 84-85% similarity compared to Pasteur. According to phylogenetic construction, isolated samples do not share the same lineage toward Pasteur. The homology scores of isolated samples compared to RABV within Asia such as Indonesia, China, Thailand, India, and Korea were 98-99%, 92-93%, 88-89%, 86-88%, and 85-88%, respectively. According to antigenic site analysis compared to Pasteur, it was found that there were amino acid mutations within antigenic Site IV of nucleoprotein. Amino acid mutation from isoleucine to valine occurred in amino acid number 240 of 6 Kalimantan, 7 Kalimantan, and 8 Kalimantan. Amino acid mutation from alanine to aspartate and asparagine to threonine occurred within the same antigenic site in amino acid number 246 and 273 of C4 isolate from Sulawesi.

CONCLUSION

According to homology and phylogenetic tree analyses, isolated RABV remained different compared to RABV within Asia and Pasteur. The amino acid mutation occurred in antigenic site of nucleoprotein encoding gene.

Incidence of human rabies and characterization of rabies virus nucleoprotein gene in dogs in Fujian Province, Southeast China, 2002-2012

Background

Rabies is a global fatal infectious viral disease that is characterized by a high mortality after onset of clinical symptoms. Recently, there has been an increase in the incidence of rabies in China. The aim of this study was to investigate the incidence of human rabies and characterize the rabies virus nucleoprotein gene in dogs sampled from Fujian Province, Southeast China from 2002 to 2012.

Methods

Data pertaining to human rabies cases in Fujian Province during the period from 2002 through 2012 were collected, and the epidemiological profiles were described. The saliva and brain specimens were collected from dogs in Quanzhou, Longyan and Sanming cities of the province, and the rabies virus antigen was determined in the canine saliva specimens using an ELISA assay. Rabies virus RNA was extracted from canine brain specimens, and rabies virus nucleoprotein gene was amplified using a nested RT-PCR assay, followed by sequencing and genotyping.

Results

A total of 226 human rabies cases were reported in Fujian Province from 2002 to 2012, in which 197 cases were detected in three cities of Quanzhou, Longyan and Sanming. ELISA assay revealed positive rabies virus antigen in six of eight rabid dogs and 165 of 3492 seemingly healthy dogs. The full-length gene fragment of the rabies virus nucleoprotein gene was amplified from the brain specimens of seven rabid dogs and 12 seemingly healthy dogs. Sequence alignment and phylogenetic analysis revealed that these 19 rabies virus nucleoprotein genes all belonged to genotype I, and were classified into three genetic groups. Sequencing analysis showed a 99.7% to 100% intra-group and an 86.4% to 89.3% inter-group homology.

Conclusions

This study is the first description pertaining to the epidemiological characteristics of human rabies cases and characterization of the rabies virus nucleoprotein gene in dogs in Fujian Province, Southeast China. Our findings may provide valuable knowledge for the development of strategies targeting the prevention and control of rabies.

Molecular characterization of atypical antigenic variants of canine rabies virus reveals its reintroduction by wildlife vectors in southeastern Mexico

Rabies is an infectious viral disease that is practically always fatal following the onset of clinical signs. In Mexico, the last case of human rabies transmitted by dogs was reported in 2006 and canine rabies has declined significantly due to vaccination campaigns implemented in the country. Here we report on the molecular characterization of six rabies virus strains found in Yucatan and Chiapas, remarkably, four of them showed an atypical reaction pattern when antigenic characterization with a reduced panel of eight monoclonal antibodies was performed. Phylogenetic analyses on the RNA sequences unveiled that the three atypical strains from Yucatan are associated with skunks. Analysis using the virus entire genome showed that they belong to a different lineage distinct from the variants described for this animal species in Mexico. The Chiapas atypical strain was grouped in a lineage that was considered extinct, while the others are clustered within classic dog variants.

Cell culture extraction and purification of rabies virus nucleoprotein

BACKGROUND

Rabies is a major zoonotic viral disease and is detected using the World Health Organization standard diagnostic techniques. Rabies detection is preferably done using the fluorescent antibody technique (FAT) that provides reliable diagnosis with almost 100% accuracy for all variant strains, if a proper conjugate is used. Rabies virus nucleoprotein (NP) is the most important protein used in production of a specific diagnostic conjugate.

OBJECTIVES

The aim of this study was to extract the cell-associated rabies virus NP from infected Baby Hamster Kidney cell clone (BSR) with rabies virus (Pasteur vaccine strain/PV) and purify for a future project to produce an anti-NP conjugate.

MATERIALS AND METHODS

Pasteur vaccine strain (PV) as the standard rabies vaccine strain with a focus-forming dose (FFD) of 105 was inoculated in to the BSR cell culture at a concentration of 10(6) cells per milliliter. Infected cells were harvested 72 hours after infection and the rabies NP was extracted from these cells by low-speed centrifugation and purification by ultracentrifugation in cesium chloride (CsCl) gradient. For analysis, the purified NP was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

The volume of the lysate was 15 mL and it became 2.5 mL after purification, with a concentration of 3.25 mg/mL. The corresponding band to the cell lysate protein on the SDS-PAGE had a molecular weight of 50 KDa, similar to the molecular weight of NP in rabies virus.

CONCLUSIONS

The rabies virus NP could be extracted and purified in an appropriate amount from infected cell culture. The results of SDS-PAGE analysis showed that the intact rabies virus NP had been purified properly and thus could be used for further steps to produce the specific diagnostic rabies conjugate.

Characterization of a wild rabies virus isolate of porcine origin in China

Rabies virus (RABV) that circulates worldwide in a variety of mammals can cause fatal encephalomyelitis. GD-SH-01, a street rabies virus, was isolated from a rabid pig in China. We investigated the pathogenicity of GD-SH-01 in suckling and adult mice, and compared the susceptibility of NA and BHK-21 cells in the culture to infection by GD-SH-01 and CVS-24. The complete GD-SH-01 genome sequence was determined and compared with known RABV wild strains to understand the mutations and genetic diversity that allow RABV to spread and adapt in new hosts, such as pigs. Our results suggest that GD-SH-01 possesses the characteristics of a virulent strain in Southern China and shows higher pathogenicity index than that of CVS-24 regardless of its lower level of replication in mouse brain. Up to 47 unique nucleotide substitutions were found in the genome, including five missense mutations. These data provide useful information for further understanding the transmission mechanism and the genetic variation of RABV in dissimilar hosts.

Identification of rabies virus mimotopes screened from a phage display peptide library with purified dog anti-rabies virus serum IgG

The rabies virus glycoprotein (G) is a key protein for both virus infectivity and eliciting protective immunity as an antigen. What is more, the nucleoprotein (N) is also a significant rabies virus antigen. In this study, purified anti-rabies virus IgG from dogs immunized with the standard CVS-11 strain was used to screen the Ph.D.-12™ Phage Display Peptide Library for peptides that correspond to or mimic native G and N epitopes. In contrast to previous reports that use monoclonal antibodies or human anti-rabies virus serum, this study describes the first use of dog serum to screen for epitopes. After three rounds of biopanning, selected phage clones were identified by plaque screening, western blotting (WB), and ELISA. Positive phage clones were sequenced, and their amino acid sequences were deduced. Alignment of the peptide sequences to G and N indicated that the epitope peptides matched well with G amino acids at positions 34-42, 198-200, 226-264, 296-371, and 330-343, as well as to N amino acids at positions 22-168 (N-terminal) and 262-450 (C-terminal), confirming that the sequences were indeed mimicking epitopes. Thirty percent of the selected clones matched reported antigenic regions located at sites II and III of the glycoprotein. Two sequences, LEPKGRYDDPWT and ATRYDDIWASTA, that have no homology to the known antigenic sites of either the G or N exhibited a common RYDD-W-T motif that is highly homologous to the amino acid residues at positions 126-141 of the G. This finding indicates that this motif may be a new potential RABV G B cell epitope. Amino acids 126-141 containing the RYDD-W-T motif may become a novel key epitope region and allow the development of a rabies vaccine or diagnostic reagents for the treatment of rabies.

Molecular characterization of KGH, the first human isolate of rabies virus in Korea

The complete genome sequence of the KGH strain of the first human rabies virus, which was isolated from a skin biopsy of a patient with rabies, whose symptoms developed due to bites from a raccoon dog in 2001. The size of the KGH strain genome was determined to be 11,928 nucleotides (nt) with a leader sequence of 58 nt, nucleoprotein gene of 1,353 nt, phosphoprotein gene of 894 nt, matrix protein gene of 609 nt, glycoprotein gene of 1,575 nt, RNA-dependent RNA polymerase gene of 6,384 nt, and trailer region of 69 nt. Sequence similarity was compared with 39 fully sequenced rabies virus genomes currently available, and the result showed 70.6-91.6 % at the nucleotide level, and 82.8-97.9 % at the amino acid level. The deduced amino acids in the viral protein were compared with those of other rabies viruses, and various functional regions were investigated. As a result, we found that the KGH strain only had a unique amino acid substitution that was identified to be associated either with host immune response and pathogenicity in the N protein, or with a related region regulating STAT1 in the P protein, and related to pathogenicity in G protein. Based on phylogenetic analyses using the complete genome of 39 rabies viruses, the KGH strain was determined to be closely related with the NNV-RAB-H strain and transplant rabies virus serotype 1, which are Indian isolates, and was confirmed to belong to the Arctic-like 2 clade. The KGH strain was most closely related to the SKRRD0204HC and SKRRD0205HC strain when compared with Korean animal isolates, which was separated around the same time and place, and belonged to the Gangwon III subgroup.

Molecular characterization of the complete genome of a street rabies virus WH11 isolated from donkey in China

The complete genomic sequence of a rabies virus isolate WH11, isolated from brain tissue of a rabid donkey in China, was determined and compared with other rabies viruses. This is the first Chinese street strain which was isolated from donkey and the entire length and organization of the virus was similar to that of other rabies viruses. Multiple alignments of amino acid sequences of the nucleoprotein, phosphoprotein, matrix protein, glycoprotein, and large protein of WH11 with those of other rabies viruses were undertaken to examine the conservative degree of functional regions. Phylogenetic analysis using the complete genomic sequence of WH11 determined that this isolate is most closely related with rabies viruses previously isolated in China and the attenuated Chinese vaccine strain CTN181.

Confirmation of a new conserved linear epitope of Lyssavirus nucleoprotein

Bioinformatics analysis was used to predict potential epitopes of Lyssavirus nucleoprotein and highlighted some distinct differences in the quantity and localization of the epitopes disclosed by epitope analysis of monoclonal antibodies against Lyssavirus nucleoprotein. Bioinformatics analysis showed that the domain containing residues 152-164 of Lyssavirus nucleoprotein was a conserved linear epitope that had not been reported previously. Immunization of two rabbits with the corresponding synthetic peptide conjugated to the Keyhole Limpe hemocyanin (KLH) macromolecule resulted in a titer of anti-peptide antibody above 1:200,000 in rabbit sera as detected by indirect enzyme-linked immunosorbent assay (ELISA). Western blot analysis demonstrated that the anti-peptide antibody recognized denatured Lyssavirus nucleoprotein in sodium dodecylsulfonate-polyacrylate gel electrophoresis (SDS-PAGE). Affinity chromatography purification and FITC-labeling of the anti-peptide antibody in rabbit sera was performed. FITC-labeled anti-peptide antibody could recognize Lyssavirus nucleoprotein in BSR cells and canine brain tissues even at a 1:200 dilution. Residues 152-164 of Lyssavirus nucleoprotein were verified as a conserved linear epitope in Lyssavirus.

Whole-genome analysis of a human rabies virus from Sri Lanka

The complete genome sequence of a human rabies virus, strain H-08-1320, from Sri Lanka was determined and compared with other rabies viruses. The size of the genome was 11,926 nt, and it was composed of a 58-nucleotide 3' leader, five protein genes--N (1353 nt), P (894 nt), M (609 nt), G (1575 nt), and L (6387 nt)--and a 70-nt 5' trailer. The intergenic region G-L contained 515 nt. The sizes of the nucleoprotein, phosphoprotein, matrix-protein, glycoprotein and large-protein was 450, 296, 202, 524 and 2,128 residues, respectively. The phosphoprotein and large protein were one amino acid shorter and longer, respectively, than those of most rabies viruses. The glycoprotein of H-08-1320 had a unique amino acid substitution at antigenic site I. Whole-genome phylogenetic analysis showed that strain H-08-1320 formed an independent lineage and did not cluster with rabies viruses from other countries.

Determination and molecular analysis of the complete genome sequence of two wild-type rabies viruses isolated from a haematophagous bat and a frugivorous bat in Brazil

The complete genome sequences of two Brazilian wild-type rabies viruses (RABV), a BR-DR1 isolate from a haematophagous bat (Desmodus rotundus) and a BR-AL1 isolate from a frugivorous bat (Artibeus lituratus), were determined. The genomes of the BR-DR1 and BR-AL1 had 11,923 and 11,922 nt, respectively, and both encoded the five standard genes of rhabdoviruses. The complete nucleotide sequence identity between the BR-DR1 and BR-AL1 isolates was 97%. The BR-DR1 and BR-AL1 isolates had some conserved functional sites revealed by the fixed isolates, whereas both isolates had unique amino acid substitutions in the antigenic region IV of the nucleocapsid gene. Therefore, it is speculated that both isolates were nearly identical in virologic character. According to our phylogenetic analysis based on the complete genomes, both isolates belonged to genotype 1, and to the previously defined "vampire bat-related RABV lineage" which consisted of mainly D. rotundus- and A. lituratus-isolates; however, a branch pattern with high bootstrap values suggested that BR-DR1 was more closely related to the 9001FRA isolate, which was collected from a dog bitten by a bat in French Guiana, than to BR-AL1. This result suggests that the vampire bat-related RABV lineage includes Brazilian vampire bat and Brazilian frugivorous bat RABV and is further divided into Brazilian vampire bat and Brazilian frugivorous bat RABV sub-lineages. The phylogenetic analysis based on the complete genomes was valuable in discriminating among very closely related isolates.

Molecular characterization of the complete genome of a street rabies virus isolated in China

In this study, the complete genomic sequence of a rabies virus isolate HN10, recovered from brain tissue of a rabid patient in China, was determined. This is the first Chinese street isolate that has been fully characterized. The overall organization of this virus is typical of that observed for all other rabies viruses. Alignments of amino acid sequences of the phosphoprotein, glycoprotein and large protein of HN10 with those of other rabies viruses were used to examine the extent of conservation of known functional regions. Phylogenetic analysis using either the complete or partial genomic sequence of HN10 determined that this isolate is most closely associated with viruses previously shown to circulate in Guangxi and Hunan provinces. In addition, of all vaccine strains used for comparison, the attenuated Chinese vaccine strain CTN181 is most closely related to HN10.

Genetic characterisation of attenuated SAD rabies virus strains used for oral vaccination of wildlife

The elimination of rabies from the red fox (Vulpes vulpes) in Western Europe has been achieved by the oral rabies vaccination (ORV) of wildlife with a range of attenuated rabies virus strains. With the exception of the vaccinia rabies glycoprotein recombinant vaccine (VRG), all strains were originally derived from a common ancestor; the Street Alabama Dufferin (SAD) field strain. However, after more than 30 years of ORV it is still not possible to distinguish these vaccine strains and there is little information on the genetic basis for their attenuation. We therefore sequenced and compared the full-length genome of five commercially available SAD vaccine viruses (SAD B19, SAD P5/88, SAG2, SAD VA1 and SAD Bern) and four other SAD strains (the original SAD Bern, SAD VA1, ERA and SAD 1-3670 Wistar). Nucleotide sequencing allowed identifying each vaccine strain unambiguously. Phylogenetic analysis revealed that the majority of the currently used commercial attenuated rabies virus vaccines appear to be derived from SAD B19 rather than from SAD Bern. One commercially available vaccine virus did not contain the SAD strain mentioned in the product information of the producer. Two SAD vaccine strains appeared to consist of mixed genomic sequences. Furthermore, in-del events targeting A-rich sequences (in positive strand) within the 3' non-coding regions of M and G genes were observed in SAD-derivates developed in Europe. Our data also supports the idea of a possible recombination that had occurred during the derivation of the European branch of SAD viruses. If confirmed, this recombination event would be the first one reported among RABV vaccine strains.

Epitope mapping of series of monoclonal antibodies against the hepatocellular carcinoma-associated antigen HAb18G/CD147

The hepatocellular carcinoma-associated antigen HAb18G/CD147, a member of CD147 family, could promote tumour invasion and metastasis via inducing the secretion of matrix metalloproteinases (MMP). Anti-CD147 monoclonal antibodies (MoAb) have exhibited obvious inhibitory effect on MMP induction. However, none of the epitopes of these MoAb has been reported. We previously prepared five MoAb against HAb18G/CD147, named HAb18, 3B3, 1B3, 5A5 and 4D2. To map the epitopes of these MoAb, a series of truncated fragments of extracellular region of HAb18G/CD147 was expressed in Escherichia coli and the MoAb-binding affinity to these fragments was examined with an enzyme-linked immunosorbent assay and Western blot. The residues (39)LTCSLNDSATEV(50), (36)KILLTCS(42) and (22)AAGTVFTTVEDL(33) were determined to be the epitopes of HAb18, 3B3 and 1B3, respectively, which were further proved by a dot-blot analysis with synthesized peptides and bioinformatics epitope prediction. The binding regions of MoAb 5A5 and 4D2 were located at residues E(120)-R(203). Then we constructed and expressed full-length HAb18G/CD147 and truncated HAb18G/CD147 without residues A(22)-V(50) in COS-7 cells. Gelatin zymography and Boyden chamber assay showed that the COS-7 cells expressing truncated HAb18G/CD147 failed to induce MMP production and enhance the cells' invasive potential, compared with the cells expressing full-length HAb18G/CD147. Taken together with the obviously inhibitory effects of HAb18 on the function of full-length HAb18G/CD147, these findings suggest that residues (22)AAGTVFTTVEDLGSKILLTCSLNDSATEV(50) may play a critical role in the functions of HAb18G/CD147 on MMP secretion and tumour invasion. These key residues can be used as potential drug target in cancer therapy.

Expression of the nucleoprotein gene of rabies virus for use as a diagnostic reagent

The nucleoprotein (N) gene of rabies virus CTN strain, was cloned, sequenced and expressed in Escherichia coli as a fusion with maltose binding protein (MBP). The antigenicity of this recombinant MBP-N fusion protein was examined by Western blotting and enzyme linked immunosorbent assay (ELISA). Subsequently, an indirect ELISA was developed to detect rabies specific antibody levels. Using sera from naive and vaccinated animals the ELISA results were compared with virus neutralizing antibodies detected by a rapid fluorescent focus inhibition test (RFFIT). Neutralizing titres by RFFIT were found to correlate well with the OD values in the ELISA (r=0.9436) and the sensitivity and specificity of the ELISA were shown to be 93.4 and 100%, respectively. The data indicate that the recombinant MBP-N fusion protein can be expressed and isolated straightforwardly and may be useful as a safe and abundant source of antigen to monitor seropositivity in vaccinated canines.

Structural difference recognized by a monoclonal antibody #404-11 between the rabies virus nucleocapsid (NC) produced in virus infected cells and the NC-like structures produced in the nucleoprotein (N) cDNA-transfected cells

We investigated structural changes in the rabies virus (HEP-Flury strain) nucleocapsid (NC) during the virus replication, for which we used two anti-nucleoprotein (N) monoclonal antibodies (mAbs), #404-11 (specific for a conformation-dependently exposed linear epitope) and #1-7-11 (specific for a conformational epitope which is exposed after the nucleocapsid formation). Both mAbs recognized the N protein of the viral NC, but not of the RNA-free N-P complex. The 1-7-11 and 404-11 epitopes could be mapped to the N-terminal and the C-terminal regions of N protein, respectively. Immunoprecipitation studies demonstrated that treatment of the NC either with the alkaline phosphatase or sodium deoxycholate (DOC) resulted in dissociation of most P proteins from the NC and in the reduced reactivity to mAb #404-11, but not to mAb #1-7-11. NC-like structures produced in the N cDNA-transfected cells displayed strong reactivity to mAb #1-7-11; however, reactivity to mAb #404-11 was very weak. And, coexpression with viral phosphoprotein (P) resulted in little increase in reactivity to mAb #404-11 of the NC-like structures, while the reactivity was significantly increased by cotransfection with P and the viral minigenome whose 3'- and 5'-end structures were derived from the viral genome. From these results, we assume that, although the 404-11 epitope is a linear one, the epitope-containing region is exposed only when N proteins encapsidate properly the viral RNA in collaboration with the P protein. Further, exposure of the 404-11 epitope region might be function-related, and be regulated by association and dissociation of the P protein.

Could the homologous sequence of anti-inflammatory pentapeptide (MLIF) produced by Entamoeba histolytica in the N protein of rabies virus affect the inflammatory process?

Amebiasis and rabies are public health problems, and they have in common a poor inflammatory effect in the target organs that they affect. In the GenBank, it was found that the anti-inflammatory peptide monocyte locomotion inhibitory factor (MLIF) produced by Entamoeba histolytica homologates 80%, with a fragment of the N protein of the rabies virus. We speculated if the N protein could contribute to the scant inflammatory reaction produced by rabies virus in central nervous system. The N protein was obtained and studied in vitro and in vivo. The N protein, as MLIF, inhibited the respiratory burst in human mononuclear phagocytes (43%, p<0.05), but in contrast to MLIF, it increased chemotaxis and it did not significantly inhibit delayed hypersensitivity skin reaction to 1-chloro-2-4-dinitrobenzene in guinea pigs. Therefore, the full peptide sequence has to be present or it has to be cleaved-free from the large recombinant N protein molecule (55 kDa) to become active.

The molecular epidemiology of rabies associated with chiropteran hosts in Mexico

While large-scale dog vaccination campaigns have significantly reduced urban rabies throughout Mexico, reports of sylvatic rabies, including cases of spill-over of bat strains into livestock and humans, are increasing. To improve knowledge of these epidemiological trends, 64 Mexican rabies virus isolates from various host species, have been characterized. Phylogenetic analysis at the viral P locus identified distinct viral strains associated with terrestrial reservoirs (dog, skunk and fox/bobcat) and a variant associated with the insectivorous bat, T. brasiliensis, consistent with prior reports. Of the two distinct clades of viruses associated with the vampire bat reservoir, one comprised just four specimens and formed an outlying group to all other vampire bat rabies isolates including those from South America and the Caribbean, a finding consistent with the early emergence of the vampire bat reservoir in Mexico. Antigenic variation of the vampire bat specimens did not correlate with the main genetic groupings; moreover complete N gene sequence analysis of selected specimens indicated limited variation within the encoded nucleoprotein that could form the basis of antigenic variation. A single isolate recovered from a cat represents a new viral variant not previously identified in North America that probably circulates in a species of insectivorous bat.

Epitope mapping and functional analysis of sigma A and sigma NS proteins of avian reovirus

We have previously shown that avian reovirus (ARV) sigmaA and sigmaNS proteins possess dsRNA and ssRNA binding activity and suggested that there are two epitopes on sigmaA (I and II) and three epitopes (A, B, and C) on sigmaNS. To further define the location of epitopes on sigmaA and sigmaNS proteins and to further elucidate the biological functions of these epitopes by using monoclonal antibodies (MAbs) 62, 1F9, H1E1, and 4A123 against the ARV S1133 strain, the full-length and deletion fragments of S2 and S4 genes of ARV generated by polymerase chain reaction (PCR) were cloned into pET32 expression vectors and the fusion proteins were overexpressed in Escherichia coli BL21 strain. Epitope mapping using MAbs and E. coli-expressed deletion fragments of sigmaA and sigmaNS of the ARV S1133 strain, synthetic peptides, and the cross reactivity of MAbs to heterologous ARV strains demonstrated that epitope II on sigmaA was located at amino acid residues 340QWVMAGLVSAA350 and epitope B on sigmaNS at amino acid residues 180MLDMVDGRP188. The MAbs (62, 1F9, and H1E1) directed against epitopes II and B did not require the native conformation of sigmaA and sigmaNS, suggesting that their binding activities were conformation-independent. On the other hand, MAb 4A123 only reacted with complete sigmaNS but not with truncated sigmaNS fusion proteins in Western blot, suggesting that the binding activity of MAb to epitope A on sigmaNS was conformation-dependent. Amino acid sequence analysis and the binding assays of MAb 62 to heterologous ARV strains suggested that epitope II on sigmaA was highly conserved among ARV strains and that this epitope is suitable as a serological marker for the detection of ARV antibodies following natural infection in chickens. On the contrary, an amino acid substitution at position 183 (M to V) in epitope B of ARV could hinder the reactivity of the sigmaNS with MAb 1F9. The sigmaNS of ARV with ssRNA-binding activity could be blocked by monoclonal antibody 1F9. The epitope B on sigmaNS is required for ssRNA binding because its deletion fully abolished the ssRNA binding activity of sigmaNS.

Cross-reactive antigenicity of nucleoproteins of lyssaviruses recognized by a monospecific antirabies virus nucleoprotein antiserum on paraffin sections of formalin-fixed tissues

Diagnosis of rabies is routinely confirmed by detection of rabies virus antigens in acetone-fixed frozen brain tissues or imprint smears using an immunofluorescence method with commercial antirabies virus antibodies. Since recent molecular analyses disclosed wide heterogeneity in the genome sequences of rabies virus strains and related lyssaviruses, it is necessary to confirm the presence of common epitopes in these lyssaviruses. In this study we confirmed the presence of cross-reactive antigens of various lyssaviruses in paraffin sections of formalin-fixed tissue using a monospecific rabbit antiserum prepared by immunization with a recombinant nucleoprotein of rabies virus. By immunohistochemical application, the antigen was detected predominantly in the cytoplasm of neurons in the brains of mice infected with rabies virus, Duvenhage virus, Mokola virus and European bat lyssavirus-1, while no cross-reaction was observed in uninfected humans and animals including dogs, bats, and raccoons. In addition, we examined one autopsy case that was infected in a rabies-endemic nation and developed the clinical manifestation of rabies after returning to Japan in 1970, and found that the antigen was well preserved in paraffin sections of formalin-fixed tissues. Thus, this suggests that the lyssavirus-specific antigen is recognized by the monospecific antibody against rabies virus nucleoprotein, and that this cross-reactive antigen is detectable on formalin-fixed paraffin-embedded tissues by immunohistochemical analysis.

Characterization of monoclonal antibodies raised against recombinant respiratory syncytial virus nucleocapsid (N) protein: identification of a region in the carboxy terminus of N involved in the interaction with P protein

To investigate structure and biological properties of the nucleocapsid (N) protein of respiratory syncytial virus (RSV), we have generated a panel of 16 monoclonal antibodies, raised against recombinant N protein, and epitope mapped seven of these to three antigenic sites (Site I aa 16-30; Site II aa 341-350; Site III aa 351-365). Characterization by immunofluorescence and by immunoprecipitation assay demonstrated that a monoclonal antibody to antigenic site I can detect N protein complexed with phospho (P) protein. Antibodies to antigenic sites II and III, which are adjacent to each other near the carboxyl terminus of the N protein, have distinct properties. A site III monoclonal antibody detected N protein in cytoplasmic inclusion bodies and in the cytosol, but not when N was complexed to P protein, while the site II antibody reacted with N protein in the nucleocapsid fraction but did not detect cytosolic N protein. Further investigation into the reactivities of the antibodies after binding of P to N in vitro demonstrated that antigenic sites II and III were blocked by the interaction, indicating an involvement for the carboxy domain of N in the N-P interaction. This was confirmed by the ability of peptides from the carboxy terminus of N to inhibit the N-P interaction in vitro.