Vaccine for mosquito-borne infection shows promise in test

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MINNEAPOLIS — A novel vac­cine de­vel­oped by U.S. gov­ern­ment re­search­ers is show­ing prom­ise against chikun­gunya, a de­bil­i­tat­ing mos­quito-borne vi­rus that started spread­ing this sum­mer in the south­ern United States.

The vi­rus has sick­ened mil­lions of peo­ple in Africa and Asia, where it is en­demic, and slammed into the Ca­rib­bean and South Amer­ica in the past year with an es­ti­mated 165,000 cases. The in­fec­tion trig­gers a high fe­ver and mal­aise, with the vi­rus of­ten pen­e­trat­ing the joints and caus­ing se­vere ar­thri­tis pain that can last for months. There is no treat­ment.

The ex­per­i­men­tal im­mu­ni­za­tion, given in three in­jec­tions at vary­ing doses to 25 healthy vol­un­teers, trig­gered an im­mune re­sponse sim­i­lar to pa­tients who re­cov­ered from the in­fec­tion, ac­cord­ing to the study pub­lished Thurs­day in the jour­nal Lan­cet. Most re­search­ers be­lieve that pa­tients who re­cover from the in­fec­tion won’t get sick again, though more in­ves­ti­ga­tion is needed, said al­ler­gist-im­mu­nol­o­gist Julie Ledger­wood, a se­nior study au­thor.

The strength of the re­sponse “is why we are so op­ti­mis­tic about the vac­cine,” Dr. Ledger­wood, chief of the vac­cine re­search cen­ter at the Na­tional In­sti­tute of Al­lergy and In­fec­tious Dis­eases, said in a phone in­ter­view. “At all three doses, the sub­jects tol­er­ated the vac­cine well, a very im­por­tant point in a first in hu­man study.”

While chikun­gunya ini­tially emerged in Tan­za­nia in 1953, the first four in­fec­tions ac­quired in the United States started last month in Flor­ida. The mos­qui­toes that spread the dis­ease have re­cently been found from Vir­ginia to Flor­ida, sweep­ing across the south­ern United States to Cal­i­for­nia. His­tor­i­cally, they have been spot­ted as far north as New York and Iowa.

More work must be done be­fore the im­mu­ni­za­tion is of­fered to a wider group of peo­ple. It costs $200 mil­lion to $500 mil­lion to de­velop a new vac­cine, which can be a chal­lenge if the mar­ket isn’t large enough to jus­tify the in­vest­ment, said Ann M. Pow­ers, of the U.S. Centers for Dis­ease Con­trol and Preven­tion’s di­vi­sion of vec­tor-borne dis­eases in Fort Collins, Colo. Re­search­ers should con­tinue work­ing on this and other vac­cines for chikun­gunya since the vi­rus can blaze through un­pro­tected groups of peo­ple, sick­en­ing as much as 63 per­cent of a lo­cal group within months, she wrote in an ed­i­to­rial.

The vac­cine is crafted from pro­teins found on the out­side en­ve­lope of the vi­rus, par­ti­cles that ac­ti­vate the im­mune sys­tem with­out car­ry­ing the ge­netic ma­terial needed to trig­ger an in­fec­tion. All 25 vol­un­teers pro­duced an­ti­bod­ies to neu­tral­ize the vi­rus af­ter get­ting the in­jec­tions, with a sig­nifi­cant boost af­ter the third shot, the study found.

The an­ti­bod­ies pro­duced to fight an in­fec­tion re­mained for at least 11 months af­ter the fi­nal vac­ci­na­tion, sug­gest­ing that the pro­tec­tion may be long-last­ing, the re­search­ers said.

The Na­tional In­sti­tutes of Health has re­ceived one li­cense ap­pli­ca­tion from a po­ten­tial part­ner, Dr. Ledger­wood said. The agency is com­mit­ted to con­tin­ued de­vel­op­ment of the vac­cine, and a part­ner­ship would al­low the re­search­ers to go fur­ther, she said. Ad­di­tional work on the safety and po­tency of the vac­cine is nec­es­sary be­fore large-scale tri­als could be done, she said.

There have been more than 570,000 sus­pected cases in the Amer­i­cas since the vi­rus first ap­peared in the Western Hemi­sphere in late 2013, ac­cord­ing to the NIH. More than 500 cases have been re­ported in the con­ti­nen­tal United States; al­most all in­volved trav­el­ers who brought the vi­rus with them.


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