^
A
A
A

Mosquitoes with built-in 'genetic shield' stop malaria - infection rates drop by 93%

 
, medical expert
Last reviewed: 27.07.2025
 
Fact-checked
х

All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.

We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.

If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.

25 July 2025, 11:58

Overcoming insecticide resistance: How a single gene modification in mosquitoes self-propagates across generations, virtually eliminating malaria transmission without compromising survival.

In a recently published study in Nature, a team of scientists examined whether the glutamine 224 (Q224) allele in fibrinogen-related protein 1 (FREP1) renders Anopheles stephensi mosquitoes resistant to Plasmodium infection, estimated the survival costs associated with this allele, and tested an allelic gene drive system to spread this protective mutation through populations.

Prerequisites

Around 600,000 people died from malaria in 2023, mostly children in sub-Saharan Africa and South Asia. Traditional methods of control – mosquito nets, insecticide treatments, antimalarial drugs – are losing their effectiveness due to resistance in mosquitoes and parasites. Gene drive technologies that spread beneficial alleles through mosquito populations offer a promising and sustainable solution.

The FREP1 protein helps parasites cross the mosquito midgut, but the natural variant Q224 can prevent infection without compromising the mosquito's biology. The goal was to test whether such an endogenous allele could be safely distributed to reduce malaria transmission while maintaining the mosquito's viability.

About the study

Using CRISPR/Cas9, two strains of Anopheles stephensi were created that differed only in the 224th amino acid in the FREP1 protein: a wild type with leucine (L224) and a potentially protective strain with glutamine (Q224). The guide RNA targeted an intron region 126 bp upstream of the codon, allowing for homologous recombination with the insertion of a fluorescent label (GFP or RFP).

Fitness was assessed by wing length, fecundity, egg hatchability, pupation, adult emergence, and lifespan (Kaplan–Meier survival analysis).

Vector competence was determined using standard membrane feeding of Plasmodium falciparum (human) and Plasmodium berghei (rodent) parasites, with oocyst and sporozoite counts in salivary glands.

The allele drive system included a cassette with gRNA against L224 and Cas9 under the control of the vasa promoter. Allele frequencies were monitored using fluorescent tags in multi-cycle experiments (10 generations). Genotyping was performed using PCR, Sanger sequencing, and NGS. Bayesian modeling estimated allele conversion, fitness costs, and dynamics during free mating in the laboratory.

Results

The FREP1Q224 allele did not cause significant losses in survival: wing length, fecundity, hatching, pupation, and adult emergence were identical to the FREP1L224 control. Small differences in male size and lifespan did not affect competitiveness. Virgin FREP1Q224 females lived as long as controls, and females after bloodfeeding showed only a slight decrease in lifespan.

Challenge experiments revealed marked protection in homozygotes.

  • At low concentrations of P. falciparum gametocytes (0.08%):
    • Infection rate dropped from 80% to ~30% in FREP1Q224;
    • Average number of oocysts: from 3 to 0;
    • Sporozoites in salivary glands: from >4000 to 0.
  • At higher gametocythemia (0.15%):
    • Average number of oocysts: from ~32 to
    • Sporozoites also decreased dramatically.
  • For P. berghei:
    • Average number of oocysts: from 43 to 25;
    • Sporozoites: from ~19,000 to 11,000.
  • Heterozygotes (FREP1L224/Q224) were not protected.

Gene drive efficiency

  • In paired crosses, Cas9 + gRNA L224 converted 50 to 86% of FREP1L224 alleles to FREP1Q224;
  • With maternal Cas9, the frequency was higher;
  • In the 2nd generation, the frequency of the protective allele reached 93%;
  • The incidence of NHEJ repair pathway error was low (0–12%) and typically caused damage.
  • In cell populations with a donor:recipient ratio of 1:3, the FREP1Q224 frequency increased from 25% to >90% over 10 generations;
  • The frequency of NHEJ alleles fell from 5.4% to

Bayesian modeling supported the hypothesis of high conversion, low frequency of stable mutations and a lethal sterile mosaicism effect, where WT homozygotes with the maternal Cas9 genotype suffered from somatic mutations and reduced survival.

Later generations showed almost complete suppression of P. falciparum oocysts (median 0 to 5.5), confirming that the population had become largely refractory to parasite transmission.

The protective allele had no hidden benefits or side effects, and was spread by drive.

Conclusions

The study found that replacing a single amino acid in the FREP1 protein and shifting its inheritance using a gene drive could make Anopheles stephensi virtually immune to malaria – both human and rodent – without compromising the mosquitoes' viability.

This approach complements existing measures (nets, insecticides, drugs) whose effectiveness is reduced by resistance. Such a system can also be used to restore sensitivity to insecticides or introduce other protective alleles.

Before the technology can be implemented, strict environmental, ethical and governance frameworks, as well as systems for controlling dissemination, are needed.

You are reporting a typo in the following text:
Simply click the "Send typo report" button to complete the report. You can also include a comment.