Association of dengue virus infection susceptibility with polymorphisms of 2'-5'-oligoadenylate synthetase genes: a case-control study

Oligoadenylate synthetases play an important role in the immune response against dengue virus. Single nucleotide polymorphisms in the oligoadenylate synthetases genes are known to affect oligoadenylate synthetases activity and are associated with outcome of viral infections. Polymorphisms in the OAS1 SNPs (rs1131454), OAS2 SNPs (rs1293762, rs15895 and rs1732778) and OAS3 SNPs (rs2285932 and rs2072136) genes were studied using PCR followed by restriction fragment length polymorphism methods in 30 patients for dengue infection and 40 control group who have no documented evidence of symptomatic dengue. An increase in the frequency of OAS2 gene rs1293762 SNP G/T heterozygotes (p=0.012), decrease in the frequency of SNP G/G homozygotes (p=0.005) and decrease in the frequency of OAS2 gene rs1732778 SNP G/G homozygotes (p=0.000017) and A/A homozygotes (p=0.0000012) were observed among the dengue patients compared with control group. Our results suggest that OAS2 haplotypes are associated with differential susceptibility to clinical outcomes of dengue virus infection.

Impact of MDA and the prospects of elimination of the lone focus of diurnally sub periodic lymphatic filariasis in Nicobar Islands, India

Mass Drug Administration is being carried out in Andaman and Nicobar Islands, India since 2004. Cross sectional microfilaria (Mf) survey was conducted in Nancowry group of islands, the lone foci of diurnally sub periodic form of bancroftian filariasis in Nicobar district, to examine its eligibility for Transmission Assessment Survey (TAS). A total of 2561 individuals (coverage: 23.9%) were screened from five islands. The overall Mf prevalence was 3.28%. Except one island, all other islands recorded Mf prevalence >1%, ranging from 2.5% to 5.3%, indicating persistence of infection despite six annual rounds of MDA. Mf prevalence was age dependent and was higher among males, but not significantly different between genders. Age and gender specific analysis showed a significant reduction in all the age classes among females vis a vis pre-MDA prevalence while the reduction was significant only in 21-30 and 41-50 age classes in males. Exposure to day biting and forest dwelling Downsiomyia nivea can be attributed for the persistent infection besides non-compliance for MDA. Based on fits of modified negative binomial distribution, true prevalence of Mf carriers in the community was estimated to be 4.74%, which is markedly higher (about 24%) than the observed prevalence of 3.28%. Follow up of cohorts showed evidence of continued persistence of infection and acquisition of new infections post six rounds of MDA. As the Mf prevalence was above >1% in four of the five islands, this area is not eligible for TAS, warranting continuation of MDA. Mass DEC fortified salt is suggested as an adjunct to hasten elimination of infection.

Lymphatic filariasis elimination programme in Andaman and Nicobar Islands, India: drug coverage and compliance post eight rounds of MDA

Lymphatic filariasis (LF) is endemic in the Andaman and Nicobar islands, including the lone foci for a diurnally sub-periodic form of Wuchereria bancrofti in the Nancowry group of islands. A programme to eliminate LF was launched in 2004 by the Directorate of Health Services, Andaman and Nicobar Administration which involved a single annual mass drug administration (MDA) using diethylcarbamazine (DEC) with albendazole. So far, eight rounds of MDA have been implemented through the Public Health Care network. The pattern of antifilarial drug distribution and compliance achieved in the on-going LF elimination programme in these islands has been assessed. This is the first systematic effort undertaken in these remote islands to assess the coverage and compliance with the LF elimination programme. This study covered 900 households in each of the 3 districts. There were a largest number of side effects in the Nicobar district (6.4%). Non-consumption of drugs ranged from 18.6% (Nicobar) to 42% (North and Middle Andaman). A survey revealed that almost 95.3% of the respondents had heard about MDA from the drug distributors. Therefore, the distributors should be involved in programmes designed to educate the community at risk of acquiring filarial infection and the possible side effects of the drugs.

Detection of LipL32-specific IgM by ELISA in sera of patients with a clinical diagnosis of leptospirosis

Successful treatment of leptospirosis is heavily dependent on early diagnosis and prompt initiation of antibiotic therapy. An ELISA test to detect specific IgM antibodies against LipL32 for early diagnosis of leptospirosis is described and evaluated here. One thousand one hundred and eighty sera from clinically suspected leptospirosis cases were enrolled together with 109 healthy volunteers selected from an endemic area between October 2007 and January 2010. Patients were categorized based on their clinical signs and symptoms. Sera were screened for leptospiral antibodies by the microscopic agglutination test (MAT) using a panel of locally circulating serovars followed by enzyme-linked immunosorbent assay (ELISA) based on recombinant LipL32 from Leptospira interrogans serovar Autumnalis strain N2. The sensitivity and specificity of the ELISA test were determined to establish its diagnostic efficiency. The cut-off value was determined to be 0·205. Overall sensitivity and specificity compared to the MAT were found to be 96·4 and 90·4%, respectively. The LipL32-specific IgM ELISA had good sensitivity and acceptable specificity and may be a candidate for the early serodiagnosis of human leptospirosis.

HLA class II allele polymorphism in an outbreak of chikungunya fever in Middle Andaman, India

A sudden upsurge of fever cases with joint pain was observed in the outpatient department, Community Health Centre, Rangat during July-August 2010 in Rangat Middle Andaman, India. The aetiological agent responsible for the outbreak was identified as chikungunya virus (CHIKV), by using RT-PCR and IgM ELISA. The study investigated the association of polymorphisms in the human leucocyte antigen class II genes with susceptibility or protection against CHIKV. One hundred and one patients with clinical features suggestive of CHIKV infection and 104 healthy subjects were included in the study. DNA was extracted and typed for HLA-DRB1 and DQB1 alleles. Based on the amino acid sequences of HLA-DQB1 retrieved from the IMGT/HLA database, critical amino acid differences in the specific peptide-binding pockets of HLA-DQB1 molecules were investigated. The frequencies of HLA-DRB1 alleles were not significantly different, whereas lower frequency of HLA-DQB1*03:03 was observed in CHIKV patients compared with the control population [P = 0·001, corrected P = 0·024; odds ratio (OR)  = 0, 95% confidence interval (95% CI) 0·0-0·331; Peto's OR = 0·1317, 95% CI 0·0428-0·405). Significantly lower frequency of glutamic acid at position 86 of peptide-binding pocket 1 coding HLA-DQB1 genotypes was observed in CHIKV patients compared with healthy controls (P = 0·004, OR = 0·307, 95% CI 0·125-0·707). Computational binding predictions of CD4 epitopes of CHIKV by NetMHCII revealed that HLA-DQ molecules are known to bind more CHIKV peptides than HLA-DRB1 molecules. The results suggest that HLA-DQB1 alleles and critical amino acid differences in the peptide-binding pockets of HLA-DQB1 alleles might have role in influencing infection and pathogenesis of CHIKV.

Nonstructural protein 2 (nsP2) of Chikungunya virus (CHIKV) enhances protective immunity mediated by a CHIKV envelope protein expressing DNA Vaccine

Chikungunya virus (CHIKV) is an important emerging mosquito-borne alphavirus, indigenous to tropical Africa and Asia. It can cause epidemic fever and acute illness characterized by fever and arthralgias. The epidemic cycle of this infection is similar to dengue and urban yellow fever viral infections. The generation of an efficient vaccine against CHIKV is necessary to prevent and/or control the disease manifestations of the infection. In this report, we studied immune response against a CHIKV-envelope DNA vaccine (pEnv) and the role of the CHIKV nonstructural gene 2 (nsP2) as an adjuvant for the induction of protective immune responses in a relevant mouse challenge model. When injected with the CHIKV pEnv alone, 70% of the immunized mice survived CHIKV challenge, whereas when co-injected with pEnv+pnsP2, 90% of the mice survived viral challenge. Mice also exhibited a delayed onset signs of illness, and a marked decrease in morbidity, suggesting a nsP2 mediated adjuvant effect. Co-injection of the pnsP2 adjuvant with pEnv also qualitatively and quantitatively increased antigen specific neutralizing antibody responses compared to vaccination with pEnv alone. In sum, these novel data imply that the addition of nsP2 to the pEnv vaccine enhances anti-CHIKV-Env immune responses and maybe useful to include in future CHIKV clinical vaccination strategies.

Emergence of an unusual genotype of rotavirus in andaman and nicobar islands, India

Rotavirus is the most common cause of severe diarrhoea worldwide, affecting over 125 million young children every year in developing countries. The present study is a part of ongoing childhood diarrhoeal surveillance to determine the strain diversity of rotaviruses prevalent in Andaman and Nicobar Islands. From October 2010 to February 2012, 296 stool samples from children (age group 6-60 months) with gastroenteritis were obtained from different referral hospitals/primary health centres and community health centres in Andaman and Nicobar Islands. A total of 47 samples were found positive for GARV. Among these, 21 (44.7%) samples belong to G2P[4], 12 (25.5%) samples were G1P[8], 10 (21.2%) samples belong to G9P[4], 2 (4.3%) samples belong to G1P[4] and 2 (4.3%) samples had a mixed genotype. Rotavirus G2 genotype remains the most common genotype in these islands. The prevalence of G9 rotavirus reported in the present study is higher than that reported from mainland India. The results emphasize the role of the unusual serotype G9 as an epidemiologically important genotype and the need to include G9 specificity in a rotavirus vaccine.

Role of proinflammatory cytokines and chemokines in chronic arthropathy in CHIKV infection

Chikungunya virus (CHIKV) has caused large outbreaks worldwide in recent years. Acute-phase CHIKV infection has been reported to cause mild to severe febrile illness, and in some patients, this may be followed by long-lasting polyarthritis. The mainstay of treatment includes nonsteroidal anti-inflammatory drugs and other disease-modifying agents, the use of which is based on the assumption of an immunological interference mechanism in the pathogenesis. The present study has been designed to generate preliminary evidence to test this hypothesis. The levels of 30 cytokines were estimated in serum samples of acute CHIKV-infected patients, fully-recovered patients, patients with chronic CHIKV arthritis, and controls, using a quantitative multiplex bead ELISA. The levels of the proinflammatory cytokines IL-1 and IL-6 were elevated in acute patients, but IFN-γ/β and TNF-α levels remained stable. IL-10, which might have an anti-inflammatory effect, was also elevated, indicating a predominantly anti-inflammatory response in the acute phase of infection. Elevation of MCP-1, IL-6, IL-8, MIP-1α, and MIP-1β was most prominent in the chronic phase. These cytokines and chemokines have been shown to play important roles in other arthritides, including epidemic polyarthritis (EPA) caused by Ross River virus (RRV) and rheumatoid arthritis (RA).The immunopathogenesis of chronic CHIKV arthritis might have similarities to these arthritides. The novel intervention strategies being developed for EPA and RA, such as IL-6 and IL-8 signaling blockade, may also be considered for chronic CHIKV arthritis.

Isolation and molecular characterization of Chikungunya virus from the Andaman and Nicobar archipelago, India: evidence of an East, Central, and South African genotype

Chikungunya virus (CHIKV) is an Alphavirus belonging to the family Togaviridae. In 2006, CHIKV infection struck the Andaman and Nicobar archipelago, with an attack rate of 60%. There were more than 10 cases with acute flaccid paralysis simulating the Guillian Barre Syndrome. The majority of the patients presented severe joint pain. The cause for such an explosive nature of the outbreak with increased morbidity was not known. The isolation of CHIKV was attempted and succeeded from nine subjects presenting clinical symptoms of Chikungunya fever. The cDNA of all the isolates was sequenced for partial E1 and nsP1 genes. Sequences were aligned based on the double locus sequence typing concept. The phylogenetic analysis shows that sequences of Andaman isolates grouped with the East, Central, and South African genotype of virus isolates from India, Sri Lanka, and Réunion. The genetic distance between Andaman isolates and the Réunion isolates was very small. The phylogenetic analysis confirmed the origin of the isolates responsible for the first ever confirmed CHIKV outbreak in these islands to be the East, Central, and South African genotype. In this manuscript, we discuss the involvement of the East, Central, and South African strain with the Chikungunya fever outbreak in this archipelago and double locus sequence typing as a first time approach.

A DNA vaccine against chikungunya virus is protective in mice and induces neutralizing antibodies in mice and nonhuman primates

Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus indigenous to tropical Africa and Asia. Acute illness is characterized by fever, arthralgias, conjunctivitis, rash, and sometimes arthritis. Relatively little is known about the antigenic targets for immunity, and no licensed vaccines or therapeutics are currently available for the pathogen. While the Aedes aegypti mosquito is its primary vector, recent evidence suggests that other carriers can transmit CHIKV thus raising concerns about its spread outside of natural endemic areas to new countries including the U.S. and Europe. Considering the potential for pandemic spread, understanding the development of immunity is paramount to the development of effective counter measures against CHIKV. In this study, we isolated a new CHIKV virus from an acutely infected human patient and developed a defined viral challenge stock in mice that allowed us to study viral pathogenesis and develop a viral neutralization assay. We then constructed a synthetic DNA vaccine delivered by in vivo electroporation (EP) that expresses a component of the CHIKV envelope glycoprotein and used this model to evaluate its efficacy. Vaccination induced robust antigen-specific cellular and humoral immune responses, which individually were capable of providing protection against CHIKV challenge in mice. Furthermore, vaccine studies in rhesus macaques demonstrated induction of nAb responses, which mimicked those induced in convalescent human patient sera. These data suggest a protective role for nAb against CHIKV disease and support further study of envelope-based CHIKV DNA vaccines.

Chikungunya fever epidemics are sustained by a cycle of human-mosquito-human transmission, with the epidemic cycle being similar to those of dengue and urban yellow fever. While the threat of a pandemic continues to engage the public's attention, the peculiar problems associated with the more immediate and very real seasonal epidemics are also worthy of consideration. Specifically, there are limited viral strains that have been characterized and available for laboratory study as well as limited knowledge of immune responses induced to the virus. In this study, we isolated CHIKV virus from an acutely infected human patient and used this new virus to develop a neutralization assay and a challenge stock, which is effective in a mouse model. Furthermore, we analyzed the ability of an envelope-based synthetic DNA-based vaccine to impact viral disease in the mouse model and to generate protective levels of immune responses in nonhuman primates. We observed that this novel vaccine approach generated protective levels of immune responses in both mouse and non-human primate models. We believe that these studies advance the field of Chikungunya vaccine research as well as the study of immune protection to CHIKV.

Tsunami, post-tsunami malaria situation in Nancowry group of islands, Nicobar district, Andaman and Nicobar Islands

BACKGROUND & OBJECTIVES

Due to tsunami in 2004 a large proportion of population in Nicobar group of Islands become homeless, and in 2006 large scale labour migration took place to construct the houses. In 2008, a significant increase in malaria incidence was observed in this area. Therefore, in March 2008, the situation of malaria was assessed in Nancowry Islands in Nicobar District to study the reasons for the observed upsurge in the number of cases, and to suggest public health measures to control the infection.

METHODS

The methods included a retrospective analysis of long term trend in the behaviour of malaria over the years from 2001 to 2008, analysis of the acute malaria situation, and rapid fever and malaria parasitemia survey along with environmental component. Mass radical therapy (MRT) and post-intervention parasitemia survey were carried out. The malaria situation in the aftermath of MRT was analysed.

RESULTS

During the post tsunami year (2005) there was a large increase in the incidence of malaria and this trend continued till 2008. The percentage of Plasmodium falciparum increased from 23 to 53 per cent from 2006 to 2007 that coincides with the labour influx from mainland. The study showed that Nancowry was highly endemic, with high transmission setting, and high risk area for malaria. Though, more number of migrant labourers suffered fever (75 vs 20%) and sought malaria treatment over past month but parasitemia survey showed higher point prevalence of malaria among native tribes (7.4 vs 6.5%). Post-MRT, there was a decline in the occurrence of malaria, though it did not last long.

INTERPRETATION & CONCLUSIONS

The study findings suggest that the migrant workers hailing from non-endemic or moderately endemic settings became victims of malaria in epidemic proportion in high endemic and high transmission setting. To find out the reasons for deterioration of malaria situation at Nancowry in the aftermath of tsunami requires further research.

Outbreak of chikungunya fever, Dakshina Kannada District, South India, 2008

The outbreak of chikungunya fever that surfaced in India during late 2005 has affected more than 1.56 million people, spread to more than 17 states/union territories, and is still ongoing. Many of these areas are dengue- and leptospirosis-endemic settings. We carried out a cross-sectional survey in one such chikungunya-affected location in Dakshina Kannada District of Karnataka State to estimate the magnitude of the epidemic and the proportion of chikungunya virus (CHIKV) infections that remained clinically inapparent. The seropositivity for CHIKV infection was 62.2%, and the attack rate of confirmed CHIK fever was 58.3%. The proportion of inapparent CHIKV infection was 6.3%. The increasing trend in the seropositivity and attack rate of CHIKV infection with age group was statistically significant. The present study is an indicator of the magnitude of the ongoing outbreak of CHIKV infection in India that started during 2005-2006.

FlaB PCR-based identification of pathogenic leptospiral isolates

BACKGROUND/PURPOSE

The genus Leptospira comprises pathogenic and saprophytic strains. Conventional methods for the identification of pathogenic leptospiral isolates are cumbersome and laborious. In view of these limitations, the search for alternative methods have been focused on DNA based techniques. In this study, we have developed an effective method for the rapid identification of pathogenic and saprophytic leptospiral isolates based on DNA-based techniques.

METHODS

A polymerase chain reaction(PCR)-based approach was developed using specific primer sets (flaB, G1-G2, B64I-II, and A-B) to differentiate pathogenic and saprophytic leptospiral strains. Fifty-five leptospiral isolates were used for this study. The pathogenic status of the isolates was compared with the results obtained using conventional techniques, which included growth in the presence of 8-azaguanine and growth at 13 degrees C.

RESULTS

In this analysis, 46 leptospiral isolates were confirmed as pathogenic and nine were confirmed as saprophytic. PCR with the A-B primer set yielded an amplified product of 331 bp in all of the pathogenic and saprophytic isolates. The other primer sets, G1-G2, B64I-II and flaB, yielded products of 258 bp, 568 bp, and 793 bp, respectively, exclusively for the pathogenic leptospiral strains. None of the saprophytic strains yielded products with these primer sets.

CONCLUSION

The flaB-specific primers consistently yielded an amplification product for all of the pathogenic leptospiral isolates, indicating the presence of the flaB gene only among pathogenic leptospires, and making this a useful tool for distinguishing between pathogenic and saprophytic leptospires. The efficiency of PCR-based identification corroborates the implementation of these techniques for the identification of pathogenic and saprophytic leptospiral strains.

Evolutionary implication of outer membrane lipoprotein-encoding genes ompL1, UpL32 and lipL41 of pathogenic Leptospira species

Leptospirosis is recognized as the most widespread zoonosis with a global distribution. In this study, the antigenic variation in Leptospira interrogans and Leptospira borgpetersenii isolated from human urine and field rat kidney was preliminarily confirmed by microscopic agglutination test using monoclonal antibodies, and was further subjected to amplification and identification of outer membrane lipoproteins with structural gene variation. Sequence similarity analysis revealed that these protein sequences, namely OmpL1, LipL32 and LipL41, showed no more homologies to outer membrane lipoproteins of non-pathogenic Leptospira and other closely related Spirochetes, but showed a strong identity within L. interrogans, suggesting intra-specific phylogenetic lineages that might be originated from a common pathogenic leptospiral origin. Moreover, the ompL1 gene showed more antigenic variation than UpL32 and lipL41 due to less conservation in secondary structural evolution within closely related species. Phylogenetically, ompLl and lipL41 of these strains gave a considerable proximity to L. weilii and L. santaro-sai. The ompLl gene of L. interrogans clustered distinctly from other pathogenic and non-pathogenic leptospiral species. The diversity of ompL genes has been analyzed and it envisaged that sequence-specific variations at antigenic determinant sites would result in slow evolutionary changes along with new serovar origination within closely related species. Thus, a crucial work on effective recombinant vaccine development and engineered antibodies will hopefully meet to solve the therapeutic challenges.

Characterization of leptospira borgpetersenii isolates from field rats (rattus norvegicus) by 16s rrna and lipl32 gene sequencing

The main goal of this study was to evaluate the prevalence of leptospirosis among field rodents of Tiruchirappalli district, Tamil Nadu, India. In total 35 field rats were trapped and tested for seroprevalence by the microscopic agglutination test (MAT). Isolation of leptospires was performed from blood and kidney tissues and characterized to serovar level. Genomospecies identification was carried out using 16S rRNA and lipL32 gene sequencing. The molecular phylogeny was constructed to find out species segregation. Seroprevalence was about 51.4 %, and the predominant serovars were Autumnalis, Javanica, Icterohaemorrhagiae and Pomona. Two isolates from the kidneys were identified as serovar Javanica of Serogroup Javanica, and sequence based molecular phylogeny indicated these two isolates were Leptospira borgpetersenii.

Risk factors associated with leptospirosis during an outbreak in Middle Andaman, India

BACKGROUND & OBJECTIVE

Leptospirosis outbreaks occur frequently in North and South Andaman Islands but not in Middle Andaman. In 2002, an outbreak appeared in Middle Andaman for the first time. Although a study on risk factors was conducted in North Andaman, it used seropositivity to define leptospirosis. Since seropositivity might not indicate current leptospiral infection and as no study on risk factors was conducted in Middle Andaman, we carried out this study to identify the risk factors during the outbreak.

METHODS

A suspected outbreak of leptospirosis occurred in Rangat of Middle Andaman during October - November 2002. Suspected cases were screened for leptospirosis using microscopic agglutination test (MAT). Fifty two patients confirmed to have leptospirosis based on rising titres in MAT on paired sera, and 104 age, sex and neighbourhood seronegative matched controls, were included in the study. A conditional multiple regression by backward elimination process was carried out with acute leptospirosis as the dependent factor and various environmental, occupational and behavioural factors as independent factors. A stratified analysis was also carried out.

RESULTS

The presence of cattle in the house, drinking stream water, contact with garbage, walking barefoot and standing in water while working were identified as significant factors associated with leptospirosis. Stratified analysis showed a dose response relationship between number of cattle in the house and the risk of leptospiral infection suugesting that cattle could be a source of infection.

INTERPRETATION & CONCLUSION

Identification of the potential risk factors would help understand the transmission dynamics of the disease and formulate public health interventions.

Community-centred approach for the control of Aedes spp. in a peri-urban zone in the Andaman and Nicobar Islands using temephos

BACKGROUND

Chikungunya fever struck the Andaman and Nicobar Islands in July 2006. From the entomological point of view, dengue and chikungunya are hard to control due to the high prevalence of Aedes aegypti in both urban and rural areas. Mobilizing communities for the control of Aedes aegypti has not been attempted in India.

METHODS

We did a prospective observational feasibility study in one peri-urban locality (Brookshabad) to assess the Aedes spp. infestation and subsequently test the efficacy of a community-based approach to control Aedes aegypti. An Aedes infestation larval survey was done with the assistance of community volunteers using the single larval survey (SLS) technique. House index, container index and Breteau index reflecting the relative prevalence and infestation levels were estimated. Various information, education and communication (IEC) campaign tools were developed to disseminate information about the prevalent situation. Several talks were organized to sensitize and motivate the people to realize the problem and participate in solving it. A two-pronged strategy, viz. environmental management through source reduction and anti-larval campaign using temephos was adopted to combat Aedes infestation through community involvement.

RESULTS

A total of 533 water-holding containers were searched for Aedes larvae, both indoors (188/533, 35.3%) and outdoors (345/533, 64.7%) from 104 (104/235, 44.3%) premises. Of these, 109 containers (95% CI 17.19%-24.03%) were found to support Aedes spp. larval breeding (20.45%). The Breteau index was 104.8%. Aedes aegypti predominated followed by Aedes albopictus. The most abundant water-holding containers supporting Aedes breeding were plastic, metal drums and cement tanks. These water-holding containers were targeted for temephos application by the community volunteers. Forty rounds of temephos applications were carried out during the study period. The number of containers supporting Aedes aegypti breeding reduced significantly within 1 month post-intervention by community volunteers. As a result the Breteau and house indices dropped from 104.8% to 2.7% and 44.23% to 2.6%, respectively. Thereafter, the indices remained at zero level till completion of the study.

CONCLUSION

Larval indices indicate that Aedes aegypti is well established in peri-urban Brookshabad. Predominance of this mosquito species indicates infiltration into the peri-urban locality and beginning of displacement of Aedes albopictus. Epidemiologically, 3 categories of water-holding containers, viz. plastic, metal drums and cement tanks facilitate breeding of Aedes aegypti. Consequently, targeted source reduction as one way of selectively attacking the most important types of containers with temephos is feasible. Community involvement and networking with the residents allowed for a community-centred approach to combat Aedes aegypti infestation. As an outcome of this approach, the larval indices reduced significantly and remained low. We suggest that a control strategy emphasizing the use of temephos through a community-centred approach should be considered for these islands. However, close monitoring of this approach is warranted for long term sustainability.

Immunogenicity of novel consensus-based DNA vaccines against Chikungunya virus

Chikungunya virus (CHIKV) is an emerging arbovirus and is an important human pathogen. Infection of humans by CHIKV can cause a syndrome characterized by fever, headache, rash, nausea, vomiting, myalgia, arthralgia and occasionally neurological manifestations such as acute limb weakness. It is also associated with a fatal haemorrhagic condition. CHIKV is geographically distributed from Africa through Southeast Asia and South America, and its transmission to humans is mainly through the Aedes aegypti species mosquitoes. The frequency of recent epidemics in the Indian Ocean and La Reunion islands suggests that a new vector perhaps is carrying the virus, as A. aegypti are not found there. In fact, a relative the Asian tiger mosquito, Aedes albopictus, may be the culprit which has raised concerns in the world health community regarding the potential for a CHIK virus pandemic. Accordingly steps should be taken to develop methods for the control of CHIKV. Unfortunately, currently there is no specific treatment for Chikungunya virus and there is no vaccine currently available. Here we present data of a novel consensus-based approach to vaccine design for CHIKV, employing a DNA vaccine strategy. The vaccine cassette was designed based on CHIKV capsid- and envelope-specific consensus sequences with several modifications, including codon optimization, RNA optimization, the addition of a Kozak sequence, and a substituted immunoglobulin E leader sequence. The expression of capsid, envelope E1 and E1 was evaluated using T7-coupled transcription/translation and immunoblot analysis. A recently developed, adaptive constant-current electroporation technique was used to immunize C57BL/6 mice with an intramuscular injection of plasmid coding for the CHIK-Capsid, E1 and E2. Analysis of cellular immune responses, including epitope mapping, demonstrates that electroporation of these constructs induces both potent and broad cellular immunity. In addition, antibody ELISAs demonstrate that these synthetic immunogens are capable of inducing high titer antibodies capable of recognizing native antigen. Taken together, these data support further study of the use of consensus CHIK antigens in a potential vaccine cocktail.

Leptospirosis in the Andaman Islands, India

Leptospirosis is an emerging zoonosis. In the Andaman Islands during the early twentieth century, it occurred in the penal settlements of the British India Administration, mostly as Weil's disease, an acute febrile illness with hepato-renal complications. It was caused by leptospires belonging to groups Akiamy A and Andamans A. After the 1930s nothing further is known regarding the disease until the late 1980s, when Andaman haemorrhagic fever (AHF), a mysterious illness with the majority of cases presenting pulmonary involvement, appeared. AHF was later identified as leptospirosis and severe pulmonary haemorrhage was shown for the first time as a complication of leptospirosis from India. Leptospirosis continues to occur in the Islands annually. It generally presents as two separate clinical syndromes: the hepato-renal form, and the pulmonary form, which is associated with high case fatality rates ranging from 10 to 15%. Infections are due to a variety of serovars, Valbuzzi being the commonest. Leptospira interrogans sensu stricto has been the predominant infecting species. Doxycycline has been shown to confer a beneficial effect in reducing the clinical illness and mortality during outbreaks. The history of leptospirosis in the Islands, its epidemiology, clinical spectrum, characteristics of the isolates and control are reviewed and discussed in this article.

Multilocus sequence typing method for identification and genotypic classification of pathogenic Leptospira species

Background

Leptospira are the parasitic bacterial organisms associated with a broad range of mammalian hosts and are responsible for severe cases of human Leptospirosis. The epidemiology of leptospirosis is complex and dynamic. Multiple serovars have been identified, each adapted to one or more animal hosts. Adaptation is a dynamic process that changes the spatial and temporal distribution of serovars and clinical manifestations in different hosts. Serotyping based on repertoire of surface antigens is an ambiguous and artificial system of classification of leptospiral agents. Molecular typing methods for the identification of pathogenic leptospires up to individual genome species level have been highly sought after since the decipherment of whole genome sequences. Only a few resources exist for microbial genotypic data based on individual techniques such as Multiple Locus Sequence Typing (MLST), but unfortunately no such databases are existent for leptospires.

Results

We for the first time report development of a robust MLST method for genotyping of Leptospira. Genotyping based on DNA sequence identity of 4 housekeeping genes and 2 candidate genes was analyzed in a set of 120 strains including 41 reference strains representing different geographical areas and from different sources. Of the six selected genes, adk, icdA and secY were significantly more variable whereas the LipL32 and LipL41 coding genes and the rrs2 gene were moderately variable. The phylogenetic tree clustered the isolates according to the genome-based species.

Conclusion

The main advantages of MLST over other typing methods for leptospires include reproducibility, robustness, consistency and portability. The genetic relatedness of the leptospires can be better studied by the MLST approach and can be used for molecular epidemiological and evolutionary studies and population genetics.

Seroprevalence of leptospirosis among high-risk population of Andaman Islands, India

Leptospirosis is a severe spirochetal zoonosis in the world. It is considered an occupational disease of persons engaged in agriculture, sewage works, forestry, and animal slaughtering. A study was conducted with an objective of assessing the seroprevalence of leptospirosis among the high-risk groups of Andaman Islands. A total of 611 sera samples from different high-risk populations were collected and tested by microscopic agglutination test (MAT). Genetic characterization of the isolate was done by randomly amplified polymorphic DNA (RAPD) fingerprinting, and serological characterization was done using monoclonal antibody technique. Antibodies to leptospires were detected in 322 samples giving an overall seroprevalence of 52.7%. The seroprevalence was highest among agriculture workers (62.5%) followed by sewage workers (39.4%), animal handlers (37.5%), forest workers (27.3%), and butchers (30.0%). Seroprevalence among control population was 14.7%, which was comparatively less than that of the high-risk population groups. Subject sera were most commonly reacted with organisms of the serogroup Grippotyphosa followed by Australis, and the pattern was similar in control group. Four leptospires were isolated from agriculture workers who were admitted to the public health center (PHC) with complaints of fever and body ache. Human isolates were compared with two rodent (Rattus norvegicus) isolates from the same area of agriculture workers to get initial information about the transmission cycle of leptospirosis in the study community. Randomly amplified polymorphic DNA fingerprinting pattern of the strains recovered from the rodents and human patients were identified as belonged to genomo-species Leptospira interrogans. The antigenic characterization of the strains recovered from them belonged to serovar Valbuzzi of serogroup Grippotyphosa. The study showed that people engaged in high-risk activities such as agriculture, sewage cleaning, animal handling, animal slaughtering, and forestry are frequently exposed to leptospirosis, and hence control strategies targeting these populations could be more effective.

Seroprevalence of leptospirosis among high-risk population of Andaman Islands, India

Leptospirosis is a severe spirochetal zoonosis in the world. It is considered an occupational disease of persons engaged in agriculture, sewage works, forestry, and animal slaughtering. A study was conducted with an objective of assessing the seroprevalence of leptospirosis among the high-risk groups of Andaman Islands. A total of 611 sera samples from different high-risk populations were collected and tested by microscopic agglutination test (MAT). Genetic characterization of the isolate was done by randomly amplified polymorphic DNA (RAPD) fingerprinting, and serological characterization was done using monoclonal antibody technique. Antibodies to leptospires were detected in 322 samples giving an overall seroprevalence of 52.7%. The seroprevalence was highest among agriculture workers (62.5%) followed by sewage workers (39.4%), animal handlers (37.5%), forest workers (27.3%), and butchers (30.0%). Seroprevalence among control population was 14.7%, which was comparatively less than that of the high-risk population groups. Subject sera were most commonly reacted with organisms of the serogroup Grippotyphosa followed by Australis, and the pattern was similar in control group. Four leptospires were isolated from agriculture workers who were admitted to the public health center (PHC) with complaints of fever and body ache. Human isolates were compared with two rodent (Rattus norvegicus) isolates from the same area of agriculture workers to get initial information about the transmission cycle of leptospirosis in the study community. Randomly amplified polymorphic DNA fingerprinting pattern of the strains recovered from the rodents and human patients were identified as belonged to genomo-species Leptospira interrogans. The antigenic characterization of the strains recovered from them belonged to serovar Valbuzzi of serogroup Grippotyphosa. The study showed that people engaged in high-risk activities such as agriculture, sewage cleaning, animal handling, animal slaughtering, and forestry are frequently exposed to leptospirosis, and hence control strategies targeting these populations could be more effective.

A clone of Leptospira interrogans sensu stricto is the major cause of leptospirosis in the archipelago of Andaman and Nicobar Islands, India

AIMS

Andaman and Nicobar Islands in India has a century long history of human leptospirosis. Several isolates have been recovered over the years from different locations. The present study was undertaken to understand the clonal relationship between all these pathogenic leptospires recovered from these islands.

METHODS AND RESULTS

Arbitrarily primed polymerase chain reaction (AP-PCR) was employed to genetically characterize 40 isolates recovered during 1995--2001 and their fingerprints were compared with those of 26 reference strains of known genetic and serological affinities. Sequences of PCR-amplified products from representative isolates were compared with those of different strains belonging to seven genospecies. AP-PCR fingerprints revealed that 32 of the 40 isolates were clonal in nature and fingerprints of all the isolates matched with known reference strains of pathogenic Leptospira interrogans sensu stricto. Comparison of sequence data of PCR amplified products of reference strains and isolates also corroborated these findings.

CONCLUSIONS

The study revealed that 80% of the isolates recovered from these islands were clonal in nature and all the isolates taken in the study belonged to Leptospira interrogans sensu stricto.

SIGNIFICANCE AND IMPACT OF THE STUDY

An extension of the study in animal population would help in understanding the transmission dynamics of this commonly circulating clone in these islands, which in turn might help in effective control of this public health problem.

Phenotypic & genotypic conservation of ompL1 & lipL41 among leptospiral isolates of Andaman Islands

BACKGROUND & OBJECTIVES

The leptospiral antigens that are conserved among the diverse pathogenic leptospires have potential importance in the development of new serodiagnostic and immunoprotective strategies. The present study was therefore carried out to find out the phenotypic conservation of the leptospiral proteins OmpL1 and LipL41, and the genetic conservation of ompL1 and lipL41 genes among the leptospiral isolates of Andaman Islands and among the reference strains.

METHODS

In one dimensional SDS-PAGE the leptospiral samples prepared from strains of various leptospiral serovars were run and transferred on to nitrocellulose paper and probed with pooled convalescent phase human sera to find out the phenotypic conservation of the protein fragments at 31 and 41 kDa. Further, the proteins were indirectly confirmed as OmpL1 and LipL41 by using specific rabbit hyperimmune sera. Specific primers were utilized to amplify the fragments to study the genetic conservation of ompL1 and lipL41. Further, these two fragments were sequenced and BLAST analysis was done with the whole genome of Leptospira interrogans serovar Lai for comparison.

RESULTS

Analysis of individual immunoblots using patient sera showed that the OmpL1 and LipL41 were conserved among all the isolates used in the study. Further, these two proteins were probed with specific rabbit hyperimmune sera of OmpL1 and LipL41 for confirming the fragments and it was found to be conserved among all the isolates. The PCR based amplification further showed that the genes ompL1 and lipL41 were conserved among the leptospiral isolates studied. Sequencing followed by BLAST analysis of these showed 97 per cent similarity with the whole genome sequence and low score values in comparison with other bacterial species.

INTERPRETATION & CONCLUSION

The antigenic and genetic conservation of the two proteins, OmpL1 and LipL41, indicated that these could be potential candidates for development of diagnostic test systems for leptospirosis.

Comparison of immunoreactive proteins of commonly circulating serogroups of Leptospira in Andaman Islands, India

BACKGROUND & OBJECTIVE

Early diagnosis is the key to the treatment of leptospirosis. For development of rapid diagnostic kits, a thorough knowledge about the nature of the proteins expressed by the pathogen during infection is necessary. The present study was undertaken to understand the nature of immunoreactive proteins from commonly circulating serogroups of Leptospira in the endemic Andaman and Nicobar Islands, India.

METHODS

Proteins were extracted from six strains of Leptospira representing five different serogroups following four different preparation methods, viz., whole cell lysis by sonication, detergent solubilization, outer and inner membrane isolations, and were subsequently characterized on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblots were made from the sonicated proteins using hyperimmune rabbit antisera, homologous and heterologous patient sera separately.

RESULTS

The 67, 65, 45, 43, 35, 32 and 18 kDa major proteins in the whole cell lysate were common among all the five serogroups of Leptospira. The 67, 41, 35, 32, 28 and 22 kDa were the major outer membrane proteins, while 94, 32, 25 and 18 kDa protein were in inner membrane. Immunoblots with hyperimmune rabbit antisera detected 67, 65, 60, 45, 43, 41 and 32 kDa common proteins from the whole cell lysates of all strains while homologous and heterologous patient sera detected 32 kDa as the major immunoreactive protein in all pathogenic serogroups. This protein reacted against specific LipL32 antisera indicating that this protein was LipL32.

INTERPRETATION & CONCLUSION

The circulating serogroups of Leptospira have common nature of expression of proteins during human infection. Among several immunoreactive proteins, three (67, 45 and 32 kDa) were recognized as major antigens by both rabbit hyperimmune sera and patients sera while the 32 kDa protein was recognized as the major immunoreactive protein by homologous and heterologous patient sera. These conserved immunoreactive proteins could be utilized in developing indigenous diagnostic tests for leptospirosis.

Phylogenetic relatedness among leptospiral strains belonging to same serovar recovered from patients with different clinical syndromes

Leptospirosis is an emerging zoonotic disease with widespread distribution. The disease, caused by a large number of pathogenic serovars of leptospires, varies in severity from mild flu like illness to severe and fatal forms. It has often been observed that the strains of the same serovar are associated with different clinical syndromes. In this study the isolates recovered from patients with mild and severe form of leptospirosis and those isolated from rodents trapped in the same areas were analyzed by using random amplified polymorphic DNA (RAPD) fingerprinting method using the primers PB1, M16, B11 and B12. RAPD fingerprinting patterns of these strains consistently showed five different genetic clusters. Strains belonging to serovar Ratnapura that caused hepato-renal involvement in patients in South India were genetically dissimilar to strains of the same serovar isolated from patients in Andamans who had pulmonary complications. Strains of other serovars causing mild and sever illness could also be discriminated. However, isolates obtained from human patients and rodents in the same geographical areas showed identical fingerprint patterns indicating that strains circulating in different geographical regions, though belonging to same serovar, are unique to each region.

Leptospirosis among schoolchildren of the Andaman & Nicobar Islands, India: low levels of morbidity and mortality among pre-exposed children during an epidemic

Leptospirosis is an important public health problem in the Andaman Islands. The disease is being increasingly reported among children and adolescents in recent times. An attempt was made to find out the level of exposure to leptospires, to estimate the incidence of infection and to identity the risk factors for acquiring infection among children. A sample of 1544 schoolchildren was selected. Presence of anti-leptospiral antibodies was tested using the microscopic agglutination test (MAT). Students were interviewed for behavioural factors. In total, 341 (221 seronegative and 120 seropositive) students were followed up clinically and serologically during a subsequent outbreak. An overall seropositivity rate of 23.6% (95% CI 21.54-25.81) was observed. Infection rate was 33.5% among seronegatives whereas re-infection rate was 16.7% among seropositives during the outbreak that occurred 1 month after the first sample collection. Morbidity and mortality were found to be higher among seronegative individuals than seropositives. More than 90% of leptospiral infections were found to be subclinical or unnoticed. The high level of exposure among the children results in high infection rates and because they have less previous exposure than adults, they do not have sufficient protection to resist clinical illness during outbreaks.

Percutaneous exposure resulting in laboratory-acquired leptospirosis -- a case report

A screw-capped glass tube containing a Leptospira culture accidentally broke and the laboratory worker who was handling the tube sustained a cut on his hand. The wound was flooded with the culture. The culture was that of strain MG 347 belonging to serovar Australis recovered from a patient, and it had undergone 52 passages in Ellinghausen McCullough Johnson Harris medium. The laboratory worker developed a headache 21 days after the accident and became febrile the next day. He was hospitalized for 5 days and was treated initially with doxycycline and later with ciprofloxacin. A blood sample collected on the second day of illness, after starting doxycycline therapy, yielded leptospires and the isolate, HZ 651, was identified as serovar Australis. Monoclonal antibody patterns and randomly amplified polymorphic DNA fingerprinting patterns of the isolate and strain MG 347 were identical, thus indicating that HZ 651 and MG 347 were clonal.

A 22-mer primer enhances discriminatory power of AP-PCR fingerprinting technique in characterization of leptospires

OBJECTIVES

To evaluate the discriminatory power and usefulness of arbitrarily primed-polymerase chain reaction (AP-PCR) characterization of leptospires with M16 primer.

METHODS

AP-PCR fingerprints of 20 reference strains of Leptospira representing 20 different serovars belonging to seven genospecies (Leptospira interrogans, 11; L. noguchii, 2; L. borgpetersenii, 1; L. santarosai, 2; L. biflexa, 2; L. kirschneri, 1; L. weilii, 1) were generated by employing M16 primer. Fingerprints generated with this primer were compared with those generated with two other commonly used primers PB1, and L10. An attempt was also made to type 20 leptospiral isolates with the M16 primer.

RESULTS AND CONCLUSION

Fingerprints with M16 primer could not only differentiate between strains of different genospecies, but also between strains of the same genospecies belonging to different serovars. While two commonly used primers (PB1 and L10) failed to discriminate between some of the different serovars belonging to the same genospecies, this primer was able to generate discriminatory fingerprints for all strains tested. All 20 Leptospira isolates, recovered from patients in Andaman Islands, could also be typed by fingerprints generated with the M16 primer. The discriminatory power of M16 primer adds more specificity to the rapidity of this system of characterization and can be used as an excellent tool in epidemiological studies on Leptospira.

Leptospiral proteins expressed during acute & convalescent phases of human leptospirosis

BACKGROUND & OBJECTIVES

The available serological techniques for the diagnosis of leptospirosis have less sensitivity during the early stage of the disease. Understanding of leptospiral proteins expressed during acute and convalescent phases of leptospirosis, would be help the develop of new serodiagnostic strategies. Therefore, the present study was carried out to identify (i) an antigen that is conserved among the various pathogenic leptospira; (ii) best protein antigen to which immune response can be identified in the acute phase; and (iii) best protein antigen which is present in convalescent sera which can be used for seroepidemiological studies.

METHODS

Quantitative immunoblot analysis was performed using acute and convalescent phase human sera along with sera from normal healthy individuals and from patients with typhoid, malaria and hepatitis as the controls. All the samples were analyzed for the leptospiral protein recognition by using IgM and IgG immunoblots. Leptospiral cell fractionation was performed using triton X-114 and lysozyme and further the conservation of leptospiral proteins was also performed.

RESULTS

In confirmed cases of leptospirosis, the IgG recognition in acute phase sera was 30.2, 39.5, 27.9, 55.8 and 27.9 per cent for the leptospiral proteins p32, p41/42, p58, p62 and p82 respectively. The IgG has considerably increased to 65.1, 55.8, 46.5, 67.4 and 48.8 per cent against the same proteins during convalescent phase. The IgM recognition was 32.6 , 32.6, 30.2 and 37.2 per cent for acute phase sera and 32.6, 37.2, 44.2 and 41.9 per cent for convalescent phase sera for the leptospiral proteins p14, p25, p32 and p41/42, respectively. Leptospiral proteins like p62 and p82 were recognized among all the control groups with 3.3-15.3 per cent for IgG recognition.

INTERPRETATION & CONCLUSION

Leptospiral protein p32 was found to be highly sensitive and specific and could be useful for the development of newer techniques for diagnosis and seroepidemiological studies. Combination of p32 and p41/42 for IgG and p14, p25, p32, p41/42 for IgM would increase the sensitivity of these techniques further.

Use of fluorescent amplified fragment length polymorphism for molecular epidemiology of leptospirosis in India

Nineteen isolates of leptospires recovered from patients during three epidemics that occurred at different places and different times in the Andaman Islands and eight isolates from sporadic cases were characterized using serological and molecular genetic techniques. Group sera and monoclonal antibodies were used for antigenic characterization, whereas fluorescent amplified fragment length polymorphism (FAFLP) was used for genotyping. Of the 27 isolates, 19 were identified as belonging to serogroup Grippotyphosa, 3 belonged to serogroup Australis, 2 belonged to serogroup Icterohaemorrhagiae, and 1 each belonged to serogroups Hebdomadis, Canicola, and Sejroe. Analysis of FAFLP data grouped these 27 isolates into two main clusters of genotypes. One of the clusters, populated by 19 isolates, included 16 outbreak isolates. Seven of these 19 isolates belonged to serovar Ratnapura, 10 belonged to serovar Valbuzzi, and 1 each belonged to serovar Grippotyphosa and serovar Saxkoebing. Of the 27 patients from whom isolates were obtained, 9 had severe illness, and 6 of these 9 patients had pulmonary involvement, 1 had pulmonary and hepatorenal involvement, and the remaining 2 had hepatorenal involvement alone. Two patients out of the nine severe cases died subsequently. The isolates from sporadic cases showed great genetic diversity and were also diverse antigenically. Perhaps the strains belonging to a dominant genotype (the outbreak-associated cluster) possessed epidemic potential and higher virulence with a greater predilection to cause pulmonary complications than strains belonging to other genetic backgrounds.

Leptospiral carrier state and seroprevalence among animal population--a cross-sectional sample survey in Andaman and Nicobar Islands

A study was conducted with the objective of assessing the leptospiral carrier state and seroprevalence among animal population of Andaman and Nicobar Islands. A total of 494 sera samples from different domestic animals and 85 samples from rats (Rattus rattus) were tested by microscopic agglutination test using nine serogroups prevalent in these islands. Antibodies to leptospires were detected in 164 samples giving an overall seroprevalence of (33.11%). The seroprevalence was highest among cows (40.32%). Of 85 rat (Rattus rattus) samples tested for antileptospiral antibodies six (7.1%) were positive. Leptospires were isolated from kidney of two rats and urine of one cow. Isolate from urine of cow was heavily contaminated and was subsequently lost during further subculture. The two isolates were found to be pathogenic, belonging to serogroup Grippotyphosa. The isolates were further characterized by using a set of monoclonal antibodies. The agglutination patterns of isolates were similar to that of ratnapura and valbuzzi, however these did not completely match.