Mos­quito spit stops blood clot in mice

*Tem­per­a­ture af­fects in­sec­ti­cide ef­fi­cacy against malaria vec­tors

The Guardian (Nigeria) - - HEALTH NEWS - Com­piled by Chuk­wuma Muanya, As­sis­tant Edi­tor

Abit of mos­quito saliva might one day be just what the doc­tor or­dered to stop blood clot. That is be­cause sci­en­tists have found a new way to rein­vig­o­rate an­ti­clot­ting fac­tors in mos­quito spit in the lab. The mod­i­fied blood thin­ner has so far only been tested in mice; if it ever works in hu­mans, it could help pre­vent—and even treat—the blood clots that can lead to hem­or­rhag­ing or throm­bo­sis.

When a mos­quito bites, it in­jects a po­tent mix of proteins called anophe­lins into its host, al­low­ing the blood to flow more freely. These anophe­lins have long been a tar­get of re­searchers try­ing to cre­ate new classes of blood thin­ners for hu­man use. But once ex­tracted and tested in the lab, anophe­lins do a poor job of thin­ning and un­clot­ting the blood.

To re­vi­tal­ize tired mos­quito spit, sci­en­tists added sul­fate to the mix. Sul­phate, which re­acts with amino acids in the anophe­lins, strength­ened the elec­tro­static forces be­tween the proteins, mak­ing them bet­ter able to bind to the en­zyme in blood plasma that causes clot­ting. Re­searchers in­jected three anaes­thetized mice with the mod­i­fied or orig­i­nal mol­e­cules and mea­sured how much they bled from a tail wound.

Mice treated with the mod­i­fied proteins had much thin­ner blood—their anophe­lins were 100 times as ef­fec­tive in bind­ing to the en­zyme as the un­mod­i­fied pro­tein, the sci­en­tists re­ported last month in ACS Cen­tral Sci­ence.

The team also found that sul­fated anophe­lins are more ef­fec­tive than hirudin, a blood­thin­ning mol­e­cule de­rived from the sali­vary juices of leeches, which is oc­ca­sion­ally used in clin­i­cal set­tings. Given how well the mod­i­fied anophe­lins per­formed—and the fact that they also stim­u­late a nat­u­ral im­mune re­sponse—the re­searchers are plan­ning to de­velop mos­quito spit–based blood thin­ners that could even­tu­ally be used to pre­vent and treat blood clot for­ma­tion in hu­mans.

Mean­while, am­bi­ent tem­per­a­ture has a marked ef­fect on the tox­i­c­ity of the most com­monly used in­sec­ti­cides for malaria con­trol, ac­cord­ing to a study led by Is­global, an in­sti­tu­tion sup­ported by the "la Caixa" Foun­da­tion.

The re­sults, pub­lished in Malaria Jour­nal, un­der­line the need to eval­u­ate the ef­fi­cacy of these chem­i­cals under real field con­di­tions.

The ap­pear­ance and spread of mos­qui­toes re­sis­tant to the in­sec­ti­cides cur­rently used for malaria con­trol is a threat to malaria elim­i­na­tion ef­forts. In Africa, re­sis­tance to pyrethroids (the only in­sec­ti­cide class ap­proved for treat­ing bed nets and used widely for in­door spray­ing) has been re­ported. It is there­fore cru­cial to con­tin­u­ously mon­i­tor in­sec­ti­cide sus­cep­ti­bil­ity -- or re­sis­tance -- among the main species of malaria-trans­mit­ting Anophe­les. In­sec­ti­cide ef­fi­cacy is not only de­ter­mined by the ac­tive in­gre­di­ent, but also by other fac­tors in­clud­ing am­bi­ent tem­per­a­ture. How­ever, sus­cep­ti­bil­ity tests are nor­mally per­formed in lab­o­ra­to­ries or in­sec­taries where tem­per­a­ture con­di­tions are op­ti­mal for the mos­quito.

In this study, the re­searchers ex­plored the ef­fect of tem­per­a­ture on the stan­dard in­sec­ti­cide re­sis­tance test, us­ing re­sis­tant or sus­cep­ti­ble strains of two ma­jor malaria vec­tors (An. ara­bi­en­sis and An. fu­nes­tus). Tox­i­c­ity of the pyrethroid deltamethrin and the car­ba­mate ben­dio­carb was as­sessed at dif­fer­ent tem­per­a­tures (18, 25 or 30º).

Re­sults show that tem­per­a­ture im­pacts tox­i­c­ity of both in­sec­ti­cides, but in a dif­fer­ent way: ben­dio­carb lost ef­fi­cacy at higher tem­per­a­tures for both species, re­gard­less if they were re­sis­tant or sus­cep­ti­ble. In con­trast, higher tem­per­a­tures de­creased deltamethrin tox­i­c­ity for sus­cep­ti­ble ara­bi­en­sis but the con­trary was ob­served for re­sis­tant An. ara­bi­en­sis and sus­cep­ti­ble An. fu­nes­tus. Piper­onyl-bu­tox­ide (PBO), which in­hibits pyrethroid-re­sis­tance mech­a­nisms, com­pletely re­stored deltamethrin sus­cep­ti­bil­ity at all tem­per­a­tures.

The au­thors con­clude that cau­tion must be ex­er­cised when draw­ing con­clu­sions about a chem­i­cal's ef­fi­cacy from lab­o­ra­tory as­says per­formed at only one tem­per­a­ture. Tem­per­a­tures in the field, they point out, can vary con­sid­er­able dur­ing a sin­gle day.

"Per­form­ing ef­fi­cacy tests with lo­cal vec­tors and under real field con­di­tions (which would re­flect the ap­pro­pri­ate sea­son and rel­e­vant time of day when chem­i­cals are ex­pected to act) would yield more ac­cu­rate 'en­to­mo­log­i­cal in­tel­li­gence' for ev­i­dence­based de­ci­sion-mak­ing," says Is­global re­searcher Krijn Paai­j­mans, who co­or­di­nated the study.

CREDIT: https://mi­crobe­

A bit of mos­quito saliva might one day be just what the doc­tor or­dered to stop blood clot

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