Relationship of hemolymph phenol oxidase and mosquito age in Aedes aegypti

Monophenol oxidase (MPO) and diphenol oxidase (DPO) activity in hemocytes and cell-free plasma perfused from 7-, 14-, 21-, and 28-day-old Aedes aegypti mosquitoes were compared. A progressive decrease of enzyme activity was detected as mosquito age increased, and this decrease was significant in both hemocytes and cell-free plasma when mosquitoes were 28 days old as compared with that found in 7-day-old mosquitoes. There was no significant difference in total hemolymph protein as mosquito age increased. Although this decreased MPO and DPO activity might be partially responsible for the reduced immune response against filarial worms previously reported for older mosquitoes, other factors undoubtedly play a significant role.

Induced polypeptides associated with filarial worm refractoriness in Aedes aegypti

Brugia malayi and Wuchereria bancrofti are mosquito-borne parasitic nematodes responsible for lymphatic filariasis in approximately 90 million people. The genetic control of the susceptibility of Aedes aegypti mosquitoes to B. malayi was well defined 30 years ago, but no data have since been provided regarding the gene products responsible for susceptibility or refractoriness or both. We addressed this problem by assessing polypeptide synthesis in thoracic tissue, the developmental site of this parasite, in susceptible and refractory strains of A. aegypti. Polyacrylamide gel electrophoresis of radiolabeled polypeptides synthesized in vivo were compared between (i) established susceptible and refractory strains and (ii) a refractory strain newly isolated from the established susceptible strain. Six polypeptide differences recognized by SDS/PAGE and two-dimensional gel electrophoresis were seen only in the refractory strains after they took a blood meal. A seventh polypeptide was present in those refractory mosquitoes that had ingested sucrose but increased in intensity after blood-feeding. The presence of parasites in the blood meal was not necessary to stimulate the synthesis of these polypeptides. These refractory strain-associated molecules may mediate genetically determined variation in susceptibility.

Monoclonal antibodies directed against the envelope glycoproteins of La Crosse virus

Neutralizing monoclonal antibodies directed against the envelope glycoproteins of La Crosse virus (LACV) were prepared. Two antibodies immunoprecipitated the 120 kDa virus attachment protein for vertebrate cells, G1, while five immunoprecipitated the 35 kDa G2 protein, whose function is currently unknown. Two monoclonal antibodies were obtained that specifically precipitated both G1 and G2 from [35S]cysteine labeled LACV infected cell lysates. The G2 specific monoclonal antibodies had high neutralizing titers when assayed in mosquito cells but limited ability to neutralize virus in mammalian cells. The G1/G2 specific antibodies neutralized virus infectivity in both vertebrate and invertebrate cells at high titers. These results suggest that G2 is involved in the interaction of virus with mosquito cells and that G1 and G2 may share a common structural epitope relevant to their role as attachment proteins in vertebrate and mosquito cells. Monoclonal antibodies directed against G2 or G1/G2 have not previously been reported and should be useful tools for characterizing the biological functions of these molecules in the divergent micro-environments of vertebrate and invertebrate hosts.

Aedes aegypti: characterization of hemocyte polypeptide synthesis during wound healing and immune response to inoculated microfilariae

Hemocytes from adult, female Aedes aegypti, intrathoracically inoculated with microfilariae (mf) of the nematode Dirofilaria immitis, were compared to saline-inoculated and uninoculated controls using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), 125I-labeling, and wheat germ agglutinin (WGA) binding techniques. Activation of wound healing and/or melanotic encapsulation responses by the inoculation of saline or mf into the host hemocoel induced alterations in the hemocyte activity of these mosquitoes. Protein assays of whole hemocyte lysates revealed that hemocytes from saline- and mf-inoculated mosquitoes had higher protein concentrations than uninoculated controls. Many polypeptides were seen within all three hemocytes preparations when stained with silver nitrate, but there was an overall increase in protein synthesis in hemocytes from inoculated mosquitoes. In addition, a 200-kDa polypeptide was uniquely expressed in hemocytes from inoculated mosquitoes. There were several prominent surface proteins labeled with 125I, and several of these increased dramatically in intensity during wound healing and/or a melanotic encapsulation response. Similar results were seen in two-dimensional separations. A set of basic polypeptides comigrated with an acidic polypeptide resulting in a surface protein of approximately 80-90 kDa that increased in inoculated mosquitoes. Hemocytes from inoculated mosquitoes exhibited a group of three acidic polypeptides, whereas hemocytes from uninoculated mosquitoes exhibited only one of these protein fragments. Three surface polypeptides bound 125I-labeled WGA, and binding of WGA to hemocyte surface polypeptides was successfully inhibited by the incubation of cells with the lectin and its competing sugar.

Role of La Crosse virus glycoproteins in attachment of virus to host cells

Data presented in this report demonstrate that the initial event of La Crosse virus (LACV) infection of cells is probably the interaction of viral glycoproteins with specific cellular receptor sites. We have shown that LACV glycoprotein G1 binds, in a dose-dependent manner, to continuous vertebrate and mosquito cell lines, but not to mosquito midguts isolated ex vivo. This binding can be inhibited by the pretreatment of cells with excess homologous glycoprotein but not with excess heterologous LACV glycoprotein. In contrast, we have shown that LACV glycoprotein G2 binds to the continuous mosquito cell line and vector midgut cells, but not to vertebrate cells. LACV infection of vertebrate cells can be inhibited by treatment of cells with purified G1, while infection in mosquito cells can be reduced by treatment of cells with a combination of G1 and G2. The results suggest that G1 is the viral attachment protein (VAP) for vertebrate cells, and that G2 serves the same purpose for mosquito midgut cells. We speculate that the protease-resistant G2 molecule may have evolved to serve as the VAP in the midgut under conditions in which G1 might be altered or removed from the virus envelope, and thus is essential to the evolution and maintenance of vertebrate-invertebrate transmission cycles.

Dirofilaria immitis: effect on hemolymph polypeptide synthesis in Aedes aegypti during melanotic encapsulation reactions against microfilariae

[35S]Methionine-labeled hemolymph polypeptides from adult, female Aedes aegypti Liverpool strain mosquitoes inoculated with the microfilariae of the filarial nematode Dirofilaria immitis were compared with those from saline-inoculated and uninoculated controls by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by fluorography. SDS-PAGE analysis of cell-free hemolymph collected via perfusion at 6, 12, 24, 48, 72, and 96 hr postinoculation (PI) detected the enhanced expression of an 84-kDa polypeptide. This polypeptide, expressed constitutively in the hemolymph of all three groups of mosquitoes, increased considerably in inoculated mosquitoes as time progressed as compared with uninoculated controls. Moreover, the 84-kDa polypeptide was expressed at higher levels in D. immitis-inoculated mosquitoes than in saline-inoculated controls. This stimulation of de novo biosynthesis of the 84-kDa polypeptide in inoculated mosquitoes may play a role in the immune response of mosquitoes. Since it is likely that the wound healing response in insects involves many of the same chemical processes as occur in melanotic encapsulation reactions of mosquitoes against filarial worms, the preferential expression of the 84-kDa polypeptide in saline-inoculated mosquitoes seen in this study may reflect a wound healing response. The greater increase in synthesis of this protein in D. immitis-inoculated mosquitoes may reflect production of melanotic material required for parasite destruction as well as for wound healing.

Electrochemical determination of diphenol oxidase activity using high-pressure liquid chromatography

A quantitative assay for the diphenol oxidase activity of tyrosinase (EC 1.14.18.1) using high-pressure liquid chromatography with electrochemical detection is described. The assay is based on the observation (M. Sugumaran, 1986, Biochemistry 25, 4489-4492) that tyrosinase catalyzes the oxidative decarboxylation of 3,4-dihydroxymandelic acid to 3,4-dihydroxybenzaldehyde. The substrate and product were readily separated on a reverse-phase column equilibrated with 0.1 M citrate buffer, pH 3.2, containing 0.5 mM Na2 EDTA, and 5% (v/v) acetonitrile. The reaction of DHMA with mushroom tyrosinase was linear with time and proportional to the amount of enzyme present. The specific activity of mushroom tyrosinase using the method was about fourfold greater than that obtained using a spectrophotometric assay for diphenol oxidase following dopachrome formation from L-3,4-dihydroxyphenylalanine. The applicability of the high-pressure liquid chromatographic assay to determination of diphenol oxidase activity in small biological sample sizes was demonstrated by using microgram quantities of crude, cell-free hemolymph from Aedes aegypti mosquitoes.

High-pressure liquid chromatographic analysis of hemolymph plasma catecholamines in immune-reactive Aedes aegypti

Tyrosine and catecholamines have been implicated as substrates for the encapsulation reactions involved in the immune response of mosquitoes to microfilariae (mff). Identification and quantitation of tyrosine and catecholamines present in Aedes aegypti hemolymph plasma were accomplished by ion-pair high-pressure liquid chromatography with electrochemical detection at either +650 or +850 mV vs Ag/AgCl. Tyrosine, dopamine, and N-beta-alanyldopamine were detected in the hemolymph plasma of naive A. aegypti. Although no differences in these compounds were observed in hemolymph plasma from A. aegypti inoculated with Dirofilaria immitis mff, the chromatogram showed a single major peak (PI) (65 microM, expressed as dopamine equivalents) that was not present in naive hemolymph plasma. Saline-inoculated controls contained only 5% of the PI in immune reactive hemolymph plasma. A high concentration of PI (127 +/- 39 microM) was also detected after treatment of hemolymph plasma with mild alkaline conditions (pH 9.0), indicating that it is normally present as an electrochemically inert form in naive mosquitoes. High concentrations of PI were also detected in the naive hemolymph plasma from three other mosquito species, but no PI was found in A. trivittatus under any conditions. PI did not cochromatograph with any of the catecholamines commonly thought to be involved in immune responses of dipterans against metazoan parasites, suggesting that it may be a unique substrate for these reactions. The biological relevance of PI was evidenced by its appearance in the hemolymph plasma of two strains of D. immitis-inoculated A. aegypti.

Effect of gamma irradiation on the hemocyte-mediated immune response of Aedes aegypti against microfilariae

The effect of gamma irradiation on the melanotic encapsulation response of Aedes aegypti black eye Liverpool strain against inoculated Dirofilaria immitis microfilariae (mff) was assessed at 1, 2, 3, and 6 days postinoculation (PI). Mosquitoes received 6000 rad from a 137Cs source (Shepard Mark I irradiator) at 3 days postemergence and were inoculated with 15-20 mff 24 hr later. These mosquitoes were compared to nonirradiated controls that also were inoculated with 15-20 mff at 3 days postemergence. The immune response was significantly reduced in irradiated mosquitoes as compared with controls at all days PI. Although the response was significantly inhibited compared with controls, irradiated mosquitoes were still capable of eliciting a response against 69% of recovered mff at 6 days PI. External gamma irradiation did not significantly affect the proliferation of hemocytes associated with the melanotic encapsulation response of A. aegypti. The number of circulating hemocytes increased in irradiated mosquitoes in response to inoculated mff in a manner similar to nonirradiated, inoculated controls. Hemocyte monophenol oxidase activity, however, was significantly reduced in gamma-irradiated mosquitoes at 12 hr PI as compared with controls. The reduced immunological capacity of irradiated mosquitoes might be related to an interference with gene activity required for the synthesis or activation of enzymes that are directly or indirectly involved in the biochemical processes associated with the production of melanotic substances that sequester mff.

Immune competence of Aedes trivittatus hemocytes as assessed by lectin binding

Hemocytes were perfused from uninoculated, saline-inoculated, and Dirofilaria immitis microfilariae-inoculated Aedes trivittatus and assessed for their capacity to bind wheat germ agglutinin (WGA). Approximately one-fourth of perfused hemocytes were WGA positive in all groups of mosquitoes at all time periods tested. Results suggest A. trivittatus has a larger inherent population of immune-competent hemocytes as compared with Aedes aegypti and, therefore, is faster and more effective in killing microfilariae by melanotic encapsulation reactions.

Hematozoa of wild turkeys from the midwestern United States: translocation of wild turkeys and its potential role in the introduction of Plasmodium kempi

Twenty-three of 310 blood samples taken from live-trapped eastern wild turkeys (Meleagris gallopavo silvestris) from Missouri (USA), and hunter-killed birds from Wisconsin, North Dakota and Minnesota (USA), and inoculated into domestic broad-breasted-white turkey poults were positive for two species of Plasmodium. Twenty-one of the positive samples were infected with P. (Novyella) kempi, and two samples from Wisconsin were infected with P. (Giovannolaia) lophurae. Twenty percent of 310 blood smears were positive for Haemoproteus melagridis, while only 3% were infected with Leucocytozoon smithi. A statistically higher prevalence of Plasmodium spp. from 1983 to 1984 was observed in Wisconsin, and in the samples from Minnesota when compared with both Missouri and Wisconsin. Turkeys from Wisconsin and Minnesota had both a statistically higher prevalence and mean intensity of H. meleagridis than birds from Missouri. Evidence indicates that P. kempi has been introduced into other states along with the vertebrate hosts. It is suggested that greater care should be exercised when translocated wild turkeys are introduced into areas where there are other endangered or threatened avian species.

Experimental avian PMV-2 infection in a domesticated wild host: daily behavior and effect on activity levels

Paramyxovirus type 2 (PMV-2) isolated from wild birds is often considered non-pathogenic, but nothing is known about its effects on overall behavior and fitness of free-flying birds. Domestically bred, African cut-throat finches (Amadina fasciata), a species from which PMV-2 has been isolated in the wild, were inoculated with a Central American field strain of PMV-2. Patterns of behavior were examined before and after viral challenge to quantify inapparent, sublethal effects of the disease. Infected birds demonstrated a significant decrease in activity (P = 0.01) followed by an apparent recovery period. Antibody titers confirmed infection in inoculated birds and indicated that sentinel birds did not become infected.

Enzyme processing of La Crosse virus glycoprotein G1: a bunyavirus-vector infection model

Efficient transmission, amplification, and dissemination of arboviruses require viral replication in vertebrate and invertebrate hosts. As a result, virions are exposed to two significantly different environments. Exposure of LaCrosse virus (LACV) to proteolytic enzymes, such as those that may be found in the mosquito midgut, increases virus affinity for mosquito cells. These enzymes remove the major envelope glycoprotein (G1) while leaving the second glycoprotein (G2) intact. Processing of LACV glycoproteins in the mosquito midgut may be necessary to expose attachment proteins on the virion surface before attachment to, and infection of, midgut cells can occur. This model may suggest answers to questions regarding the molecular basis for midgut infection barriers and species susceptibility to arbovirus infection in nature.

Immunity to larval Brugia malayi in BALB/c mice: protective immunity and inhibition of larval development

The objective of this study was to analyze the immune response of mice to the larval stages of Brugia malayi. Male BALB/c mice were inoculated with 3 doses of irradiated third-stage larvae (L-3) of B. malayi and were subsequently challenged with L-3 implanted ip within diffusion chambers. After 3 weeks, larvae were recovered to determine their viability, length, and stage of development. A significant reduction in parasite survival was observed in immunized mice. Furthermore, larvae recovered from immunized mice were significantly shorter than larvae recovered from control mice. All larvae recovered from immunized mice were L-3, whereas 96% of larvae recovered from controls were fourth-stage larvae (L-4). Sera collected from control and immunized mice were tested for the presence of antibodies reactive with L-3 and L-4 antigens using an indirect fluorescent antibody assay employing frozen larval cross-sections as antigen. Sera recovered after challenge of control mice reacted with internal, but not surface, antigens of L-3 and L-4. Alternatively, sera from immunized mice reacted with both internal and external antigens of both L-3 and L-4.

Termination of second trimester pregnancy with gemeprost vaginal pessaries and intra-amniotic PGF2 alpha. A comparative study

152 women admitted for legal abortion in the second trimester of pregnancy were included in an open, randomized, controlled six-centre study. 75 patients received gemeprost 1 mg vaginal pessaries at 3 hours intervals up to a maximum of 5 mg and 66 patients were treated with a single 40 mg intra-amniotic dose of PGF2 alpha. The 24-hour success rate was 81% (n = 61/75) in the gemeprost and 64% (n = 42/66) in the PGF2 alpha group (p less than 0.02). The mean abortion times were 14.3 and 14.8 hours in the gemeprost and the PGF2 alpha groups, respectively. The mean time to onset of pain was shorter and more patients experienced blood loss over 100 ml during the induction in the PGF2 alpha group than in the gemeprost group (p less than 0.02). Apart from that, the nature and severity of side effects were comparable between the two groups. Besides significantly better efficacy, the non-invasive gemeprost treatment was found to be easier and safer as compared to the PGF2 alpha treatment.

Hemocyte population changes during the immune response of Aedes aegypti to inoculated microfilariae of Dirofilaria immitis

Ultrastructural and lectin-binding studies have established that the melanotic encapsulation reaction of Aedes aegypti Liverpool strain against inoculated Dirofilaria immitis microfilariae (mff) is a hemocyte-mediated reaction. Total hemocyte counts from mff-inoculated (= immune-activated), saline-inoculated, and uninoculated female A. aegypti were determined using a hemocoel perfusion technique. Total hemocyte populations in uninoculated mosquitoes were significantly larger in younger mosquitoes, but no significant change was noted as mosquitoes aged beyond 14 days. Hemocyte populations in immune-activated mosquitoes increased from 1 to 3 days postinoculation (PI) and decreased on days 4 and 5 PI. Hemocyte populations at 1 to 4 days PI were significantly elevated in mff-inoculated A. aegypti as compared with saline-inoculated controls. Saline-inoculated mosquitoes displayed little change in total hemocyte numbers from 1 to 5 days PI, and their hemocyte populations were similar to those seen in uninoculated insects of the same age. Experiments involving the inoculation of [3H]thymidine along with mff or saline alone and studies involving the administration of colchicine suggest that increased hemocyte populations in immune-activated A. aegypti are a result of mitotic division of circulating blood cells.

Brugia malayi and Brugia pahangi: inherent difference in immune activation in the mosquitoes Armigeres subalbatus and Aedes aegypti

The inherent ability of Brugia malayi and Brugia pahangi (Nematoda) to establish successful relationships with the mosquitoes Armigeres subalbatus and Aedes aegypti Liverpool strain was evaluated. Brugia pahangi microfilariae (mff) avoided the immune response and developed normally in A. subalbatus exposed to the parasite by an infective bloodmeal, whereas nearly 85% of B. malayi were destroyed by the immune response. Because A. aegypti supports the development of both filarial worm species but destroys intrathoracically inoculated B. pahangi isolated from jird blood, blood-isolated B. malayi were inoculated into A. aegypti, and the immune response was compared with that observed against B. pahangi. The response against B. malayi was significantly more rapid and effective than the response against B. pahangi. Similar results were obtained when blood-isolated B. pahangi or B. malayi were inoculated into A. subalbatus. Microfilariae of both species were able to avoid immune destruction in A. aegypti if they were allowed to penetrate the Liverpool midgut in vitro prior to inoculation. Most B. pahangi that had first penetrated an Armigeres midgut prior to inoculation into A. subalbatus were able to avoid the immune response, but by day 3 postinoculation, less than 40% of the B. malayi, treated in the same manner, were able to escape the immune response. Genetic susceptibility of mosquitoes to infection by filarial worms and potential mechanisms of immune evasion/suppression are discussed regarding B. malayi and B. pahangi.

Hemocyte monophenol oxidase activity in mosquitoes exposed to microfilariae of Dirofilaria immitis

Monophenol oxidase (MPO) activity in hemocytes collected from Aedes aegypti Liverpool strain and Aedes trivittatus intrathoracically inoculated with saline alone, inoculated with Dirofilaria immitis microfilariae (mff), or from uninoculated mosquitoes was compared using a radiometric tyrosine hydroxylation assay. Hemocyte MPO activity in mff-inoculated (= immune-activated) mosquitoes was significantly increased at 24 hr postinoculation (PI) in A. aegypti and at 6, 12, and 24 hr PI in A. trivittatus as compared with saline-inoculated controls. Baseline and immune-activated levels of hemocyte MPO activity in A. trivittatus were significantly higher compared with those seen in A. aegypti. Baseline hemocyte population levels were similar in both species, but immune activation did not elicit increases in total hemocyte populations in A. trivittatus as has been demonstrated for A. aegypti. Likewise, immune activation by the inoculation of mff did not significantly alter plasma MPO activity in A. trivittatus as compared with uninoculated or saline-inoculated mosquitoes. Plasma MPO activity in A. aegypti, however, appears to constitute a major component of the immune response. The importance of phenol oxidase(s) in the immune response of mosquitoes against mff and the relationship of observed differences in MPO activity to differences in immunological capability between A. aegypti and A. trivittatus are assessed.

Spontaneous flight activity of Aedes trivittatus infected with Dirofilaria immitis

Spontaneous flight activity of Dirofilaria immitis-infected Aedes trivittatus was evaluated by using an acoustic activity system. The activity of mosquitoes infected with low numbers of filarial larvae (1-4) was similar to that of uninfected mosquitoes. However, mosquitoes infected with more than 4 larvae became more active than uninfected mosquitoes 8 days after infection. Peak flight activity (circadian) occurred at the same time in both infected and uninfected mosquitoes, but infected mosquitoes were much more active during normal periods of quiescence. Flight activity of mosquitoes infected with more than 4 larvae was suppressed on days 10 and 14 postinfection, corresponding to times of greatest disruption of the Malpighian tubules by the developing larvae.

Host-parasite relationships of caryophyllaeid cestodes and aquatic oligochaetes: II. Effects of host age and mixed infections

Experiments were conducted to assess the relationship between annelid age and susceptibility of the annelid as an intermediate host for a caryophyllaeid, as well as the effect a mixed-species infection has on rate of metacestode development and parasite mortality. Four host-parasite systems were studied: Biacetabulum biloculoides and Hunterella nodulosa in Limnodrilus hoffmeisteri and Glaridacris catostomi in Ilyodrilus templetoni and Tubifex tubifex. Annelids were divided into 3 age classes: immature, approximately 7 days old; intermediate, approximately 14 days old; and mature, approximately 30 days old. Immature oligochaetes in all groups were more susceptible to infection, their parasites exhibited a lower mortality rate than 30-day-olds, and the total number of parasites in this group was higher than for the other age classes. Metacestodes reached the infective stage earlier in immature as compared to older oligochaetes. Interspecific competition between B. biloculoides and H. nodulosa resulted in increased parasite mortality and a slower rate of parasite development for the species that became established second. A prior infection with one species of cestode also affected the susceptibility of L. hoffmeisteri to infection with another species.

Hematozoan parasites of Rio Grande wild turkeys from southern Texas

One hundred twenty-three of 300 blood samples (41%) taken from Rio Grande wild turkeys (Meleagris gallopavo intermedia) from three locations in southern Texas (Welder Wildlife Refuge, Chaparrosa Ranch, and Campo Alegre Ranch) and subinoculated into domestic broad-breasted white turkey poults were positive for a Plasmodium (Novyella) sp. Analysis of blood films from 350 turkeys revealed Haemoproteus meleagridis in 76% of the birds. A significantly greater mean parasite intensity was observed in birds from Welder Wildlife Refuge. Birds from the Campo Alegre Ranch exhibited a significantly higher prevalence of H. meleagridis than birds from Chaparrosa. The Plasmodium sp. was infective for canaries (Serinus canaria), bobwhites (Colinus virginianus), and ring-necked pheasants (Phasianus colchicus), but would not produce infection in white leghorn chickens (Gallus gallus) or Coturnix quail (Coturnix coturnix). Attempts to infect Culex tarsalis and C. pipiens were unsuccessful. Asexual erythrocytic synchrony was not observed when blood-induced infections were monitored in two domestic turkey poults every 4 hr for 72 hr. Exoerythrocytic stages were not found upon examination of impression smears and tissue samples taken from brain, liver, spleen, kidney, lung, and bone marrow. The Plasmodium sp. is most similar morphologically to three species in the subgenus Novyella, P. hexamerium, P. vaughani, and P. kempi. The most striking similarities are to P. hexamerium, and involve mean merozoite number, erythrocytic schizont location, and vertebrate host susceptibility. It differs from P. vaughani in being able to infect turkeys and in type of parasitized erythrocytes. Differences to P. kempi include mean merozoite number, and ability to infect pheasants, and its inability to develop in C. pipiens and C. tarsalis.

Hemocyte cell surface changes in Aedes aegypti in response to microfilariae of Dirofilaria immitis

This study involved the assessment of surface changes on hemocytes of Aedes aegypti black-eyed Liverpool strain in association with the melanization response against intrathoracically inoculated Dirofilaria immitis microfilariae (mff). Surface changes on hemocytes were identified using fluorescein-labeled wheat germ agglutinin (WGA). In mosquitoes eliciting a melanization response against inoculated mff, there was a 5-fold increase in the percentages of hemocytes exhibiting WGA binding compared with saline inoculated controls. Relationships of this hemocyte activation in relation to cell-mediated melanization responses of adult mosquitoes against mff are discussed.