ASVAC2022 : 8th Asian Vaccine Conference

Aiming to further the Immunization Partners in Asia Pacific (IPAP)'s vision of a world where no one suffers from a vaccine preventable disease, the 8^th Asian Vaccine Conference (ASVAC 2022) was held in Colombo, Sri Lanka and virtually from 15 to 18, September 2022 (www.asianvaccine.com). This conference followed those held in Siem Reap, Cambodia (2009), Manila, Philippines (2010), Jakarta, Indonesia (2011), Cebu, Philippines (2013), Hanoi, Vietnam (2015), Singapore (2017) and Naypyidaw and Yangon, Myanmar (2019). The ASVAC2022 themed "Immunization: in Era of Pandemics," commenced with the EPI Managers' Workshop, followed by pre-conference workshops and Vaccinology Masterclass, followed by the main conference featuring 5 plenary lectures, 6 partner-led symposia, free paper and poster presentations, and industry-supported lunch and evening sessions. There were over 1830 registered participants, with 112 attending in person and 998 virtually from 63 countries. The conference was organized by IPAP and hosted by the Vaccine and Infectious Disease Forum of Sri Lanka, Sri Lanka College of Pediatricians, Sri Lanka College of Microbiologists and College of General Practitioners of Sri Lanka, with the support of the Ministry of Health, Sri Lanka. The 9^th ASVAC is scheduled to be held in Davao City, Philippines in late 2023.

Inborn Errors of Immunity-the Sri Lankan Experience 2010-2022

PURPOSE

Inborn errors of immunity (IEI) are typically monogenic. Data from the Indian subcontinent are relatively scarce. This paper evaluates IEI diagnosed in Sri Lanka.

METHODS

Data of patients diagnosed with IEI from 2010 to 2022 at the Department of Immunology, Medical Research Institute, Colombo, Sri Lanka, were retrospectively analyzed.

RESULTS

Two hundred and six patients were diagnosed with IEI, with a prevalence of 0.94 per 100,000. The onset of disease was below 12 years in 84.9%, whereas in 10.9%, it was after 18 years. The male: female ratio was 1.78:1. Consanguinity was identified in 26.6%. IEI were found in all but one (bone marrow failure) of the 10 IUIS categories. Predominantly antibody deficiencies were the most common category among the nine identified (30.1%), followed by combined immune deficiencies with syndromic features (21.3%), immunodeficiencies affecting cellular and humoral immunity (19.9%), congenital defects of phagocyte number or function (13.1%), and defects in intrinsic and innate immunity (8.2%). Severe combined immune deficiency (SCID) was the commonest disease (14.6%), followed by chronic granulomatous disease (CGD) (10.6%) and X linked agammaglobulinemia (8.7%). Of the patients with a known outcome (n = 184), 51 died (27.7%). Mortality rates were high in SCID (83.3%), Omenn syndrome (OS) (100%), and CGD (31.8%) patients.

CONCLUSION

IEI in Sri Lanka are diagnosed mainly in childhood. The low diagnosis rates suggest a need for educating clinicians regarding IEI in adulthood. The high mortality rates associated with some IEI indicate the need of transplant services in the country.

Humoral immune response and changes in peritoneal cell populations in rats immunized against two Leptospira serovars; serovar patoc and serovar pyrogenes

BACKGROUND

Leptospirosis is a zoonotic disease caused by Leptospira species. Variations in lipopolysaccharide (LPS) structure in Leptospira are known to be associated with the serovar diversity and antigenicity. Development of immunodiagnostics for early detection of leptospirosis based on immune responses against different pathogenic antigens as well as development of vaccines are important. Hence, this study has assessed the immune response generated against leptospiral LPS and whole antigen preparations of pathogenic and saprophytic Leptospira and specific changes in peritoneal cells was also studied to elucidate the cellular responses associated with immune response of Wistar rats.

METHODS

During the study, immune response induced by two types of Leptospira antigen preparations of two selected serovars was compared. Changes in the specific peritoneal cell subpopulations following immunizations of rats were analyzed using flow cytometry.

RESULTS

Of the two antigen preparations tested, the LPS extract induced a higher IgM immune response as opposed to the sonicated antigen preparation. Of the two serovars tested, L. interrogans serovar Pyrogenes had induced a higher IgM response compared to that by L. biflexa serovar Patoc. Considering the IgG titers, equivalent responses were observed with all four antigen preparations. Significant increases in lymphocytes were observed following immunization with LPS of both serovars. Interestingly, the B2 cell percentages increased significantly during the immunization period. Further, significant correlations were observed with both IgM and IgG responses and percentage of B2 cells in the peritoneal cavity (PC).

CONCLUSION

LPS extract of L. interrogans serovar Pyrogenes induced higher IgM response while the IgG response was equivalent among the four antigen preparations tested. Significant increase of B2 cell percentage in the peritoneal cavity during the immunization reflects the accumulation of B2 cells in the PC which may play considerable role in generating humoral response against Leptospira antigens.

Identification of allergens in Artocarpus heterophyllus, Moringa oleifera, Trianthema portulacastrum and Syzygium samarangense

BACKGROUND

It is clinically important to identify allergens in Artocarpus heterophyllus (jackfruit), Moringa oleifera (moringa), Trianthema portulacastrum (horse purslane) and Syzygium samarangense (rose apple). This study included 7 patients who developed anaphylaxis to jackfruit (1), moringa (2), horse purslane (3) and rose apple (1). We sought to determine allergens in the edible ripening stages of jackfruit (tender, mature, and ripened jackfruit) and seeds, edible parts of moringa (seeds, seedpod, flesh inside seedpod, and leaves), horse purslane leaves and ripened rose apple fruit. The persistence of the allergens after cooking was also investigated.

METHODS

Allergens were identified by clinical history followed by a skin prick test. Protein profiles of plant/fruit crude protein extracts were determined by SDS-PAGE. Molecular weights of the allergens were determined by immunoblotting with patient sera.

RESULTS

A heat-stable allergen of 114 kDa in A. heterophyllus which is shared among different ripening stages and seeds was identified. Additionally, 101 kDa allergen in boiled tender jackfruit, 86 kDa allergen in boiled seeds and 80 kDa allergen in boiled mature jackfruit were identified. Five heat-stable allergens of 14, 23, 35, 43, and 48 kDa in M. oleifera, 1 heat-stable allergen of 97 kDa in T. portulacastrum, and 4 allergens of 26, 31. 60, and 82 kDa in S. samarangense were identified.

CONCLUSION

Novel IgE-sensitive proteins of A. heterophyllus, M. oleifera, T. portulacastrum and S. samarangense were identified which would be especially useful in the diagnosis of food allergies. The identified allergens can be used in Component Resolved Diagnostics (CRD).

Cardioprotective Effects of Vitex negundo: A Review of Bioactive Extracts and Compounds

There has been accumulating interest in the application of medicinal plants as alternative medicine to treat various diseases and/or to develop modern medicines. Vitex negundo is one of such medicinal plants that has been of interest to many researchers and has been of use in traditional medicine. V. negundo is found in Sri Lanka, Madagascar, Malaysia, India, China, The Philippines and East Africa. Therapeutic properties of V. negundo have previously been reviewed. Different parts, preparations and bioactive components of V. negundo possess potential protective and therapeutic effects against cardiovascular disease and related conditions as demonstrated in previous studies. We review the present state of scientific knowledge on the potential use of V. negundo and some of its bioactive components in protecting against cardiovascular diseases and related pathologies. Previous studies in animal and non-animal experimental models, although limited in number and vary in design, seem to support the cardioprotective effect of V. negundo and some of its active components. However, there is need for further preclinical and clinical studies to validate the use of V. negundo and its active constituents in protection and treatment of cardiovascular diseases. Additionally, since only a few V. negundo compounds have been evaluated, specific cardioprotective effects or mechanisms and possible side effects of other V. negundo compounds need to be extensively evaluated.

Identification of allergens in coconut milk and oil with patients sensitized to coconut milk in Sri Lanka

BACKGROUND

Despite the low prevalence of IgE sensitivity to fresh or boiled coconut milk and coconut oil, those may contain allergens of which the clinical significance remains undetermined. This study aimed to identify and compare allergens in fresh coconut milk (FCM), boiled coconut milk (BCM), unrefined wet-processed coconut oil (WPCO), and dry-processed coconut oil (DPCO) using sera from patients with allergy to coconut milk.

METHODS

The study included 18 patients with immediate hypersensitivity to coconut milk, including five who developed anaphylaxis. Sensitization was assessed by skin prick test and ImmunoCAPs using commercially available coconut extracts. Immunoblotting was performed to identify and compare allergen profiles.

RESULTS

Total sIgE levels and overall IgE reactivity of patients with anaphylaxis were higher compared to patients with allergy. Twelve allergens ranging from 5 to 128 kDa including six novel allergens with 5, 12, 47, 87, 110, and 128 kDa were visualized in immunoblots with FCM. Similarly, nine allergens of 5, 12, 17, 32, 35, 47, 87, 110, and 128 kDa were detected in BCM. One allergen (110 kDa) was discerned in all four extracts. Higher IgE prevalence was detected with three allergens of 55, 87, and 110 kDa.

CONCLUSIONS

Allergens of BCM and unrefined coconut oil (WPCO and DPCO) were determined for the first time. Novel allergens of 87 and 110 kDa and the 55 kDa allergen have the highest potential to be used in Component Resolved Diagnostics. Further, these findings demonstrate that, patients who have an allergy to coconut milk could also react to boiled coconut milk and unrefined coconut oil.

Diagnosis of Apis dorsata venom allergy: use of recombinant allergens of Apis mellifera and a passive basophil activation test

Background

Allergy to Apis dorsata (Giant Asian Honeybee) venom is the commonest insect allergy in Sri Lanka and South East Asia. However, laboratory diagnosis is difficult as the pure venom and diagnostic reagents are not commercially available.

Objective

This study assessed the use of four recombinant allergens of A. mellifera venom and the passive basophil activation test in the diagnosis of A. dorsata venom anaphylaxis.

Methods

Serum IgE levels to four recombinant allergens of A. mellifera, rApi m 1, 2, 5 and 10 were assessed and compared with serum IgE to the crude venom of A. mellifera or V. vulgaris by Phadia ImmunoCAP, in patients who developed anaphylaxis to A. dorsata stings. Basophil activation in response to venom of A. dorsata or V. affinis was assessed using a passive basophil activation test. Association of the severity of the reaction with basophil activation was compared.

Results

rApi m 1 and 10 combinedly had significant correlation (r = 0.722; p < 0.001) with the crude venom of A. mellifera (Western honeybee) and a higher positivity rate of 90% (27/30). Whereas, IgE reactivity to rApi m 2 or 5 had significant correlation (p = 0.02 and p = 0.005 respectively) with V. vulgaris crude venom. All 30 (100%) were positive to A. dorsata venom in passive BAT; 70% (21/30) had over 80% activation, 96.7% (29/30) had over 60% activation and 100% had over 50% activation. Percentage activation of basophils in patients who had mild or moderate reactions (n = 20) was significantly low (p = 0.02) from that of patients who had severe reactions (n = 10).

Conclusions

rApi m 1 and 10 when combined was sensitive for the diagnosis of A. dorsata allergy. This combination had the lowest cross-reactivity rate with Vespula vulgaris. The passive BAT is highly sensitive in A. dorsata allergy. The basophil reactivity was significantly higher in severe anaphylaxis compared to mild/moderate anaphylaxis. This finding should be further explored in further studies.

Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott–Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Autoimmune encephalitis in a South Asian population

BACKGROUND

Autoimmune encephalitis (AE) is now considered a main, potentially curable cause of encephalitis, but remains conspicuously underreported from South Asia. We studied the clinical characteristics in relation to their antibody status and outcomes of patients presenting with AE in Sri Lanka.

METHODS

Patients admitting to government hospitals who were clinically suspected of AE by an on-site neurologist were prospectively recruited over a period of 12 months. Sera and cerebrospinal fluid were tested for NMDAR, AMPAR1, AMPAR2, LGI1, CASPR2, GABARB1/B2 antibodies (Ab) using commercial cell-based assays. Demographic, clinical and laboratory data were compiled into an investigator-administered proforma. Patients were reviewed at 1 year follow up either in person or via telephone.

RESULTS

One-hundred and forty-two patients from 21 of 25 districts in Sri Lanka (median age = 20.5 years; range 1-86 years; females = 61.3%) were recruited. Of them, 65 (45.8%; median age = 19 years; range 1-86 years; females = 64.6%) fulfilled diagnostic criteria for probable NMDAR-antibody encephalitis (NMDARE) and 6 (4.2%; median age = 44 years; range 28-71 years; females = 83.3%) limbic encephalitis (LE). Abnormal behaviour (95.3%), seizures (81.5%) and movement disorders (69.2%) were the most frequent clinical manifestations of probable NMDARE. NMDAR-antibodies were detectable in 29 (44.6%) and not detectable in 36 in CSF of probable-NMDARE patients. Abnormal EEG was more frequent (p = 0.003) while a worse outcome (OR = 2.78; 95% CI = 0.88-9.09) and deaths (OR = 2.38; 95% CI = 0.67-8.33) were more likely in antibody-negative than antibody-positive probable-NMDARE. Most patients with LE had amnesia (50%) and/or confusion (100%) with agitation (83.3%) and seizures (100%) but none had detectable antibodies to any of the antigens tested.

CONCLUSIONS

NMDARE is the commonest type of AE among South Asians as is the case worldwide. Clinical presentations of NMDARAb-positive and NMDARAb-negative AE patients do not significantly differ but EEG may be a useful marker of an autoimmune basis for psychiatric symptoms.

Diagnosis of Vespa affinis venom allergy: use of immunochemical methods and a passive basophil activation test

Background

Allergy to Vespa affinis venom is common in the Asia Pacific region. Venom preparations for diagnosis are not commercially available for this species.

Methods

The prominent allergens in V. affinis venom were identifiedusing immunochemical methods. Use of ImmunoCAP of Vespula vulgaris crude venom/its components and a passive basophil activation test (BAT) in the diagnosis of patients who had anaphylaxis to V. affinis venom (n = 30) were also accessed. The IgE double-positivity rates (positive to both hornet and honeybee) in ImmunoCAP and the passive BAT were determined.

Results

High IgE reactivity was seen with the five allergens in V. affinis venom; 96% (29/30) for 34 and 24 kDa, 93% (28/30) for 45 kDa and 90% (27/30) reactivity for the 100 and 80 kDa respectively. IgE cross-reactivity was low with ImmunoCAP using V. vulgaris venom (43%; 13/30) and Ves v1 (3%; 1/30), but relatively high with Ves v5 (73%; 22/30). All patients (100%) were positive to V. affinis venom in passive BAT. In ImmunoCAP, a high double-positivity rate (76%; 23/30) was detected while no double-positivity was detected in passive BAT.

Conclusions

High IgE reactivity for five allergens of V. affinis points to the potential of using these allergens in component resolved diagnosis (CRD). The passive BAT has shown its importance as a promising diagnostic tool with high accuracy. It would be particularly useful in cases with doubtful double-positive results of other diagnostic tests.

Hyper IgE recurrent infection syndrome in South Asia: is there a different outcome?

BACKGROUND

Hyper IgE recurrent infection syndrome (HIES) is a rare immune deficiency, characterized by recurrent staphylococcal skin and lung abscesses, pneumonia and increased IgE levels. The majority of autosomal dominant HIES (AD HIGE) is due to hypomorphic mutations in the signal transducer and the activator of transcription 3 (STAT3) gene.

CASE PRESENTATION

Five patients were diagnosed with HIES, based on the clinical criteria and scoring system developed at the National Institutes of Health (NIH), USA. The STAT3 gene was sequenced and previously described mutations were identified in all five patients. We compare the clinical features of our patients with those from Asia, Europe and the US.

CONCLUSION

Even though the number of patients is limited, there are some clinical differences in patients from South Asia compared to European and even East Asian patients. However, the mutations detected are located at hot spots seen in western and Asian patients with AD HIGE.

IgE cross-reactivity of phospholipase A2 and hyaluronidase of Apis dorsata (Giant Asian Honeybee) and Apis mellifera (Western Honeybee) venom: Possible use of A. mellifera venom for diagnosis of patients allergic to A. dorsata venom

Diagnostic and therapeutic reagents are unavailable for anaphylaxis arising from stings by Apis dorsata. Venom profiles and cross-reactivity of A. dorsata and Apis mellifera were compared, to ascertain whether venom of A. mellifera can be used for diagnosis in A. dorsata allergy. Both venom profiles were similar by High Performance Liquid Chromatography and SDS-PAGE. Sera of 29 of 30 (96.7%) patients with anaphylaxis to A. dorsata stings had IgE to the phospholipase-2 (PLA₂) doublet (15 and 16 kDa) of A. dorsata venom by immunoblot, compared to 26 of 30 (86.7%) with the PLA₂ of A. mellifera and a purified preparation of PLA₂. Twelve patients (40%) with severe anaphylaxis had IgE reactivity to a 39 kDa protein band of venom of both species, a third band, identified in immunoblot as hyaluronidase. The cross-reactivity of PLA₂ and hyaluronidase of A. dorsata and A. mellifera were further confirmed by immunoblot inhibition results. Twenty five of 30 (83.3%) of our patients had positive venom specific IgE (>0.35 KU_A/L) reactivity to Phadia ImmunoCAPs of A. mellifera venom. The observed IgE cross reactivity suggests the possibility of using A. mellifera venom as a diagnostic test for A. dorsata venom allergy.

Sensitization to bovine serum albumin as a possible cause of allergic reactions to vaccines

BACKGROUND

Immediate type hypersensitivity to vaccines containing bovine/porcine excipients, such as the measles, mumps and rubella (MMR) vaccine is probably due to sensitization to bovine/porcine gelatin. Most patients with such reactions in Sri Lanka have cow's milk (CM) or beef allergy.

OBJECTIVES

We investigated whether those who had beef and CM allergy had a higher incidence of hypersensitivity reactions to vaccines and the possible trigger of such reactions.

MATERIAL AND METHODS

Twenty patients with immediate type hypersensitivity reactions to vaccines containing bovine/porcine excipients, controls with allergy to beef/pork (n=11) or CM (n=11), and 8 non atopic controls were recruited. Total serum IgE, specific IgE to beef, CM, casein, beta lactoglobulin, gelatin and bovine serum albumin (BSA) by Phadia ImmunoCap and IgE to porcine gelatin by Western blot were evaluated.

RESULTS

11/20, 5/20, 2/20, 2/20, 1/20 and 1/20 patients reported allergic reactions to measles containing, JE, rabies primary chick embryo, pentavalent, diphtheria and tetanus, and adult diphtheria and tetanus vaccines, respectively. Only one patient with allergy to vaccines had gelatin specific IgE, whereas IgE to BSA was seen in 73.3%, 90%, 66.6% and 0 of vaccine, beef or CM allergic and non-atopic controls, respectively. The mean IgE to BSA was higher in patients with allergy to vaccines, although not significant. Specific IgE to BSA was present in 54.7% of children with allergy to CM, of whom 11.8% had high levels (>17.5kUA/L). In contrast, 66.6% of these children did not have specific IgE to β-lactoglobulin, which is one of the major components of whey protein.

CONCLUSION AND CLINICAL RELEVANCE

Gelatin does not appear to play a major role in Sri Lankan children with allergy to vaccines. In contrast, due to the higher levels of BSA specific IgE, sensitization to BSA is possibly playing a role.

PCR detection and typing of human papilloma virus DNA in squamous carcinoma of the cervix in a cohort of Sri Lankan women

OBJECTIVE

To determine the prevalence of human papilloma virus (HPV) types 16 and 18 in squamous carcinomas of the cervix in Sri Lanka.

DESIGN

Case control study.

SETTING

One gynaecological unit at the Cancer Institute, Maharagama, Sri Lanka.

PATIENTS

15 patients with squamous carcinoma of the cervix, and 15 age matched controls with histologically normal cervices.

MEASUREMENTS

DNA was extracted from paraffin embedded cervical biopsies. Polymerase chain reaction was performed on extracted DNA employing primers specific for HPV types 16 and 18.

RESULTS

HPV 16 DNA was detected in 11 out of 15 cervical cancer biopsies (73.3%), in comparison with 3 out of 15 normal controls (20%). HPV 18 was detected in 3 out of 15 cervical cancer biopsies, but not in a single control biopsy.

CONCLUSION

Despite the limited number of cases in this cohort, this study supports the strong association between HPV 16 and squamous cancer of the cervix.

A case of hyper-IgE syndrome

Hyper-IgE syndrome, a multi-system disorder affecting dentition, skeletal and immune systems and connective tissues, presents with recurrent infections and dermatitis. We report here the first case in Sri Lanka.

Dietary sodium intake induced myenteric neuron hypertrophy in Wistar rats

In the present study we investigated the effect of salt intake on myenteric neuron size of the colon of adult male Wistar rats. The animals were placed on either a high-salt (HS; 8%; 12 animals) or a low-salt diet (LS; 0.15%; 12 animals) for 15 or 52 weeks and blood pressure was measured. The sizes of myenteric neurons of the distal colon from both groups were measured. No difference in neuron size was observed between the HS and LS groups after 15 weeks. After 52 weeks on HS, neuron size was increased (P<0.005) when compared with the LS group. The rats also presented hypertension, which was significantly different at 52 weeks (142 +/- 11 vs 119 +/- 7 mmHg). These results suggest that a long time on an HS diet can significantly increase myenteric nerve cell size.