Characterizing and applying immunoglobulins in snakebite diagnostics: A simple and rapid venom detection assay for four medically important snake species in Southeast Asia

Snakebite envenoming is a medical emergency requiring urgent and specific treatment. Unfortunately, snakebite diagnostics are scarce, time-consuming and lacking specificity. Hence, this study aimed to develop a simple, quick and specific snakebite diagnostic assay using animal antibodies. Anti-venom horse immunoglobulin G (IgG) and chicken immunoglobulin Y (IgY) were produced against the venoms of four major medically important snake species in Southeast Asia, i.e., the Monocled Cobra (Naja kaouthia), Malayan Krait (Bungarus candidus), Malayan Pit Viper (Calloselasma rhodostoma), and White-lipped Green Pit Viper (Trimeresurus albolabris). Different capture:detection configurations of double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) were constructed using both immunoglobulins, and the horse IgG:IgG-HRP configuration was found to be most selective and sensitive in detecting the corresponding venoms. The method was further streamlined to develop a rapid immunodetection assay, which is able to produce a visual color change within 30 min for discrimination between different snake species. The study shows it is feasible to develop a simple, quick and specific immunodiagnostic assay using horse IgG, which can be derived directly from antisera prepared for antivenom production. The proof-of-concept indicates it is a sustainable and affordable approach in keeping with on-going antivenom manufacturing activities for specific species in the region.

Geographical variations in king cobra (Ophiophagus hannah) venom from Thailand, Malaysia, Indonesia and China: On venom lethality, antivenom immunoreactivity and in vivo neutralization

The wide distribution of king cobra (Ophiophagus hannah), a medically important venomous snake in Asia could be associated with geographical variation in the toxicity and antigenicity of the venom. This study investigated the lethality of king cobra venoms (KCV) from four geographical locales (Malaysia, Thailand, Indonesia, China), and the immunological binding as well as in vivo neutralization activities of three antivenom products (Thai Ophiophagus hannah monovalent antivenom, OHMAV; Indonesian Serum Anti Bisa Ular, SABU; Chinese Naja atra monovalent antivenom, NAMAV) toward the venoms. The Indonesian and Chinese KCV were more lethal (median lethal dose, LD₅₀ ~0.5 μg/g) than those from Malaysia and Thailand (LD₅₀ ~1.0 μg/g). The antivenoms, composed of F(ab)'₂, were variably immunoreactive toward the KCV from all locales, with OHMAV exhibited the highest immunological binding activity. In mice, OHMAV neutralized the neurotoxic lethality of Thai KCV most effectively (normalized potency = 118 mg venom neutralized per g antivenom) followed by Malaysian, Indonesian and Chinese KCV. In comparison, the hetero-specific SABU was remarkably less potent by at least 6 to10 folds, whereas NAMAV appeared to be non-effective. The finding supports that a specific king cobra antivenom is needed for the effective treatment of king cobra envenomation in each region.

Evaluating the physicochemical properties and efficacy of recently expired and aged antivenom products from Thailand and Taiwan

Gel filtration chromatography and gel electrophoresis revealed minimal protein degradation in lyophilized antivenoms which were 2-year expired (Hemato Polyvalent, Neuro Polyvalent; Thailand) and 18-year expired (Hemato Bivalent, Neuro Bivalent; Taiwan). All expired antivenoms retained immunological binding activity, and were able to neutralize the hemotoxic or neurotoxic as well as lethal effects of the homologous snake venoms. The findings show that antivenoms under proper storage conditions may remain relatively stable beyond the indicated shelf life.

Immunogenicity and safety of WHO-approved TRC-ID regimen with a chromatographically purified Vero cell rabies vaccine with or without rabies immunoglobulin in children

INTRODUCTION

Children are at risk of rabies exposure in many Asian countries. The safety and immunogenicity profile of the WHO-approved two-site intradermal Thai Red Cross regimen (modified TRC-ID regimen; 2-2-2-0-2) with a new chromatographically purified Vero-cell rabies vaccine (CPRV) is lacking. Area covered: We studied the safety and immunogenicity of the TRC-ID regimen with a new CPRV in non-immunized Thai children with possible or proven rabies exposure. Thirty-nine seronegative patients (age range 2-14 years) with rabies exposure (WHO categories II or III) received two 0.1-mL intradermal doses of CPRV at both deltoid regions on days 0, 3, 7, and 28. Twenty-five patients (64.1%) received rabies immunoglobulin due to having rabies exposure, according to WHO category III. All serum samples were tested for rabies neutralizing antibody (Nab) by the rapid fluorescent focus inhibition test (RFFIT) before vaccination, and on days 14 and 90 after vaccination. All patients had an adequate immune response (Nab titers ≥ 0.5 IU/mL) on days 14 and 90. No patients died of rabies infection. No serious adverse reactions were observed. Expert commentary: CPRV is economic, safe, and immunogenic if given as the modified TRC-ID regimen in children.

Cyanide poisoning in Thailand before and after establishment of the National Antidote Project

CONTEXT

Antidote shortage is a global problem. In Thailand, the National Antidote Project (NAP) has operated since November 2010 to manage the national antidote stockpile, educate the healthcare providers on appropriate antidote use, and evaluate antidote usage.

OBJECTIVE

To evaluate the effect of NAP implementation on mortality rate and antidote use in cyanide poisoning cases arising from ingestion of cyanide or cyanogenic glycoside.

METHODS

This is a retrospective cohort of poisoning cases involving cyanide or cyanogenic glycoside ingestion reported to Ramathibodi Poison Center from 1 January 2007 to 31 December 2015. Mortality rate, antidote use, and appropriateness of antidote use (defined as correct indication, proper dosing regimen, and administration within 90 min) before and after NAP implementation were compared. Association between parameters and fatal outcomes was analyzed.

RESULTS

A total of 343 cases involving cyanide or cyanogenic glycoside ingestion were reported to Ramathibodi Poison Center. There were 213 cases (62.1%) during NAP (Project group) and 130 cases (37.9%) pre-NAP implementation (Before group). Implementation of NAP led to increased antidote use (39.9% in Project group versus 24.6% in Before group) and a higher rate of appropriate antidote use (74.1% in Project group versus 50.0% in Before group). All 30 deaths were presented with initial severe symptoms. Cyanide chemical source and self-harm intent were associated with death (OR: 12.919, 95% CI: 4.863-39.761 and OR: 10.747, 95% CI: 3.884-28.514, respectively). No difference in overall mortality rate (13 [10.0%] deaths before versus 17 [8.0%] deaths after NAP) was found. In subgroup analysis of 80 cases with initial severe symptoms, NAP and appropriate antidote use reduced mortality (OR: 0.327, 95% CI: 0.106-0.997 and OR: 0.024, 95% CI: 0.004-0.122, respectively). In the multivariate analysis of the cases with initial severe symptoms, presence of the NAP and appropriate antidote use independently reduced the risk of death (OR: 0.122, 95% CI: 0.023-0.633 and OR: 0.034, 95% CI: 0.007-0.167, respectively), adjusted for intent of exposure, cyanide source, age, and sex.

CONCLUSIONS

After NAP implementation, both antidote use and appropriate antidote use increased. In cases presenting with severe symptoms, presence of the NAP and appropriate antidote use independently reduced the risk of mortality.

Quality vaccines for all people: Report on the 16th annual general meeting of the Developing Countries Vaccine Manufacturers' Network, 05-07th October 2015, Bangkok, Thailand

The Developing Countries Vaccine Manufacturers Network (DCVMN) assembled high-profile leaders from global health organisations and vaccine manufactures for its 16th Annual General Meeting to work towards a common goal: providing quality vaccines for all people. Vaccines contribute to a healthy community and robust health system; the Ebola outbreak has raised awareness of the threat and damage one single infectious disease can make, and it is clear that the world was not prepared. However, more research to better understand emerging infectious agents might lead to suitable vaccines which help prevent future outbreaks. DCVMN members presented their progress in developing novel vaccines against Dengue, HPV, Chikungunya, Cholera, cell-based influenza and other vaccines, demonstrating the commitment towards eliminating and eradicating preventable diseases worldwide through global collaboration and technology transfer. The successful introduction of novel Sabin-IPV and Oral Cholera vaccine in China and Korea respectively in 2015 was highlighted. In order to achieve global immunisation, local authorities and community leaders play an important role in the decision-making in vaccine introduction and uptake, based on the ability of vaccines to protect vaccinated people and protect non-vaccinated in the community through herd immunity. Reducing the risk of vaccine shortages can also be achieved by increasing regulatory convergence at regional and international levels. Combatting preventable diseases remains challenging, and collective efforts for improving multi-centre clinical trials, creating regional vaccine security strategies, fostering developing vaccine markets and procurement, and building trust in vaccines were discussed.

Morbidity and mortality of the Hartmann procedure for diverticular disease over 18 years in a single institution

AIM

Hartmann's procedure for perforated diverticulitis is associated with substantial morbidity and mortality. This study analyses factors associated with morbidity/mortality and possible changes over time.

METHOD

Patients treated by urgent Hartmann's procedure for perforated diverticulitis between 1992 and 2010 were studied, and information was collected on age, sex, perioperative details, 30-day morbidity and mortality recorded in an institutional review board approved database supplemented by chart review. Patients were divided into four groups based on the year of surgery. Univariate and multivariate logistic regression analysis was performed to identify risk factors associated with morbidity and mortality.

RESULTS

In all, 199 patients (51% female, mean age 65 years, mean body mass index 28 kg/m(2)) were identified. The American Society of Anesthesiologists (ASA) score was 4 in 30% of patients and Hinchey Stage IV in 16%. The mean length of stay was 12.5 ± 10 days. Mortality was 15% and did not change significantly over time. Overall morbidity was 52% and significantly increased over time on univariate analysis (P = 0.007) but not on multivariate analysis (P = 0.11). Independent predictors of morbidity on multivariate analysis were Hinchey IV (P < 0.001) and hypoproteinaemia (P = 0.001). Independent predictors for mortality were ASA > 3 (P = 0.01), abnormal creatinine (P = 0.007), steroid use (P = 0.007), Hinchey IV (P = 0.032), low albumin (P < 0.001) and low body mass index (P = 0.001).

CONCLUSION

Mortality after Hartmann's procedure for perforated diverticulitis has not decreased during the last 18 years. Morbidity has actually increased over time although this is related to increased disease severity and comorbidity. Future efforts should focus on the identification of patient subgroups benefiting from earlier elective surgery and alternative surgical approaches when perforated diverticulitis does occur.

New method to produce equine antirabies immunoglobulin F(ab')₂ fragments from crude plasma in high quality and yield

Rabies is still a major cause of human deaths in several developing countries. According to the World Health Organization, administration of antirabies serum or antirabies immunoglobulin is recommended for patients who have experienced a category-III exposure to rabies. Improvement of antirabies immunoglobulin production is required to enhance safety and efficacy of the products. In this paper, a new method to produce equine antirabies immunoglobulin F(ab')(2) fragments from crude plasma is proposed. First, protein G affinity chromatography was used to purify IgG from equine plasma. Moreover, purification of IgG was shown to facilitate its digestion by pepsin. Compared to the direct digestion of crude plasma, a lower amount of pepsin and a shorter digestion time were required to completely digest the purified IgG to F(ab')(2). Complete digestion of purified IgG to F(ab')(2) was achieved at a pepsin/IgG (w/w) ratio of 5:45 with preservation of structure and potency. Finally, purification of F(ab')(2) was accomplished by a combination of protein A affinity chromatography and ultrafiltration with a 50-kDa nominal molecular weight cut-off membrane. The new process resulted in 68.9±0.6 (%) total recovery of F(ab')(2) and a F(ab')(2) product of high potency.

Cross neutralization of Hypnale hypnale (hump-nosed pit viper) venom by polyvalent and monovalent Malayan pit viper antivenoms in vitro and in a rodent model

Hypnale hypnale (hump-nosed pit viper) is a medically important venomous snake in Sri Lanka and Southwestern India. Bite of this snake may result in hemostatic dysfunction, acute kidney injury and death. Clinical studies indicated that the locally available polyvalent antivenoms produced in India are not effective against hump-nosed pit viper envenoming. Hence, there is an urgent need to search for effective antivenom. In this paper, we examined the ability of Calloselasma rhodostoma (Malayan pit viper) monovalent antivenom and the Hemato polyvalent antivenom (both produced by Thai Red Cross Society, TRCS) to neutralize the lethality and toxic effects of H. hypnale venom, as C. rhodostoma is considered a sister taxon of H. hypnale. In vitro neutralization studies showed that the Hemato polyvalent antivenom effectively neutralized the lethality of H. hypnale venom (1.52mgvenom/mL antivenom) as well as the hemorrhagic, procoagulant and necrotic activities of the venom. The monovalent C. rhodostoma antivenom could also neutralize the lethality and toxic activities of the venom, but the potency was lower. The Hemato polyvalent antivenom also effectively protected mice from the lethal and local effects of H. hypnale venom in an in vivo rodent model of envenoming. Furthermore, the polyvalent antivenom could also effectively neutralize the venom of Daboia russelii (2.50mgvenom/mL antivenom), another common cause of snake bites in Sri Lanka and South India. These findings suggested that the Hemato polyvalent antivenom may be beneficial in the antivenom treatment of H. hypnale envenoming.