Global Update on P.falciparum HRP2 deletions

Transcription

1 Global Update on P.falciparum HRP2 deletions Jane Cunningham XV Reunion Annual de Evaluacion de AMI/RAVREDA Bogota, Colombia 3 5 May 2016

2 What is histidine rich protein 2 (HRP2)? Malaria protein specific to P.falciparum Found in cytoplasm and surface of Pf infected erythrocytes Secreted by the parasite and may be found in plasma and in culture media Function not very well understood May detoxify free haeme by polymerization (acts as haeme polymerase) to inactive haemozoin

3 Main application of HRP2: RDTs Most RDTs that are capable of diagnosing Plasmodium falciparum, target PfHRP2. Monoclonal antibodies in RDTs target an epitope abundant in both HRP2 and HRP3 proteins. Pf HRP2 detecting RDTs a widely used diagnostic tool for P. falciparum infections. Generally, PfHRP2 detecting RDTs have better sensitivity and thermal stability compared to pldh detecting RDTs Many more available products meeting WHO procurement criteria RDTs detecting P. falciparum alone are suitable for use in most of sub Saharan Africa where malaria cases are predominantly caused by P. falciparum. 2014: 53% of global RDT sales (166 M) in 2014 were Pf only tests delivered to Africa; in Americas 444,730 Pf only tests; 446,265 combo tests Reporting of hrp2/hrp3 deletions has a significant potential impact on RDT procurement and case management accurate reporting and mapping is essential

4 HRP2 deleted parasites.old news in South America January 2010 Volume 5 Issue 1 e % (61/148) isolates lacked pfhrp2; 21% lacked both pfhrp2 and 3 o Recommendations against use of HRP2 based RDTs o Urgent need for investigation of the abundance and geographic distribution of these parasites in Peru and neighboring countries. o Surveys conducted in: Bolivia, Colombia, Guyana, Peru, Suriname, Brazil, Honduras

5 Rest of world ( )HRP2 fishing expeditions Shortcomings in African studies including: New survey to be published in sites in 8 endemic states Use of RDTs of unknown performance/quality or not used at all Incomplete analyses: flanking genes Failure to verify the quality of DNA in the sample (amplifying at least 2 single copy genes) No published follow up surveys Just enough data to raise suspicion

6 Emphasize accurate reporting of HRP2 deletions Cheng et al. Malaria Journal 2014, 13:283 HRP3 At least 2 eg. msp1, msp2, Glurp If ELISA not available; use alternative RDT brand

7 new reports Eritrea China Myanmar Border Acta Tropica 2015; 152, Ghana Amoah et al. Malar J (2016) 15:101 India Two other HBC Use of HRP2 based RDTs in all these countries, but RDT use is not causing HRP2 deletions but it may be sufficient to select for HRP2 deleted parasites, which arose from spontaneous mutations or were imported. What other factors could be at play?

8 Eritrea In late September 2015 National Malaria Control Program/CDC of Eritrea reported to WHO high false negative RDT rates for Pf and Pv with several lots of SD BIOLINE Malaria Ag Pf/Pv, (05FK 80),compared with microscopy in several zones. Ethiopia 1 Maekel 2 Anseba 3 Gash Barka 4 Debub 5 Northern Red Sea 6 Southern Red Sea : 28 complaints forms (138 events (95% Pf) from 9 Hospitals in 4 Zobas/zones RDT retrieved from all affected areas and sent for lot testing at WHO FIND lab: Passed

9 RDT results from Ghindae, Eritrea P.falciparum confirmed by microscopy (120 parasites/µl) SD Bioline Malaria Ag Pf/Pf/Pv (05FK120) T1: HRP2 negative T2: Pf specific p LDH positive T3: Pv specific p LDH CareStart Malaria HRP2/pLDH (Pf/PAN) COMBO (G0131) T1: HRP2 negative T2: pan pldh positive (faint line) CareStart Malaria pldh (PAN) (G0111) T1: pan pldh positive

10 Preliminary results Prospective collection 50 Pf microscopy positive samples from two regional hospitals Site 1: 21/26 (81%) HRP2 Negative Site 2: 9/25 (36%) HRP2 Negative SD Bioline Malaria Ag Pf/Pf/Pv (05FK120) RDT T1: HRP2; T2: Pf specific p LDH; T3: Pv specific p LDH HRP2 test line negative/pf pldh test line positive = Pf PCR positive + HRP2 PCR negative Suggests that this RDT could be useful in screening for the presence of HRP2 deleted parasites

11 Interim recommendations Info Note 1. Suspected false negative RDT results should be investigated Consider range of factors: operator error; degradation of RDTs due to exposure to heat or humidity; low or extremely high parasite density 2. Pf hrp2/hrp3 gene deletions should be suspected: on an individual basis, when a patient sample tests negative on the HRP2 test line of at least two quality assured malaria RDTs and positive on the pan or pf pldh test line of a combination RDT and the sample is confirmed by microscopy to be positive for P. falciparum by two qualified microscopists; on a programmatic basis, when a fall in the RDT positivity rate cannot be reasonably explained by other malaria control interventions and/or when the rates of discordance between RDT and microscopy results show systematically higher positivity rates with microscopy ( 10 15%) compared to RDTs, where routine quality control is done by cross checking or both are performed on the same individuals (e.g. during surveys).

12 Interim recommendations Info Note 3. Where hrp2/hrp3 gene deletions have been reported, the prevalence should be determined in the affected country and neighbouring countries. This may require specific surveys or adaptation of planned surveys, such as malaria indicator surveys or therapeutic efficacy studies. 4. Analysis of well preserved archived specimens may be useful for identifying the existence and geographical location of hrp2/hrp3 deleted parasite populations. 5. In the absence of confirmed reports of hrp2/hrp3 gene deletions, new initiatives to find these gene deletions are not recommended, unless they are prompted by findings for programmes described under 2. In all cases, investigations should be according to established protocols and with appropriate standards and quality control measures.

13 Alternatives to HRP2 based RDTs? Threshold for use of non HRP2 based RDTs? Consider trade offs pan and pf LDH RDTs less sensitive and generate weaker test band intensities Overall non HRP2 RDT options are very limited Product Product code Manufacturer Panel Detection Score Total false 200 parasites/ l 2000 or 5000 parasites/ l Clean negative PDS for individual test lines samples : Invalid Access Bio puts both Pv HRP2/pf pldh Pv False positive rate (%) mabs for HRP2 and pfpldh on the same l Pf samples Pf samples samples WHO procurement samples Plasmodium criteria spp. requires minimum Infection i Pf only test line p/ul of 75% for Pf and Pv SD Bioline Malaria Ag P.f (HRP2/pLDH) 05FK90 Standard Diagnostics, Inc. 88 (87 / 52) NA 100 (100 / 97) NA CareStart Malaria HRP2/pLDH Pf test G0181/G0181 ET Access Bio, Inc NA 99.0 NA Pf/pan CareStart Malaria pldh 3 Line Test G0121 Access Bio, Inc CareStart Malaria Screen G0231 Access Bio, Inc Pf and Pf and Pv SD Bioline Malaria Ag P.f/P.f/P.v 05FK120 Standard Diagnostics, Inc. 85 (84 / 36) (100 / 98) f Pan only CareStart Malaria pldh (PAN) G0111 Access Bio, Inc Advantage Pan Malaria Card IR J. Mitra & Co. Pvt. Ltd Surveys + geographical variation in prevalence full picture needed to determine best RDT options. Surveillance could use RDTs with HRP2 and pf pldh test lines; HRP2 negative/pf pldh + collect DBS for PCR and HRP2/HRP3 analysis

14 WHO Response 1. Providing technical support to confirm and map HRP2/HRP3 deleted parasites where they are suspected on the basis of discordance between the results of HRP2 RDTs and highquality microscopy; 2. Working with relevant groups to adapt planned malaria indicator surveys and demographic and health surveys to include collection of blood samples for molecular testing for malaria, including analysis of pfhrp2/pfhrp3. 3. Working with research groups that hold collections of recently archived samples to screen for the presence of HRP2/HRP3 deleted parasites; 4. Rigorously reviewing manuscripts submitted for publications and published reports of pfhrp2/pfhrp3 deletions to determine the accuracy of claims and 5. Encouraging test developers and RDT manufacturers to improve the performance of pldh based tests and identify new target antigens. 6. Identify resources to be able to support 1 5

15 Thank you